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Channels publishes papers on ion channel research, ion transporter/exchanger function, biophysics, pharmacology and regulation in health and disease.

Recent publications
Marfan syndrome (MFS) is an autosomal dominant connective tissue disorder caused by mutation in fibrillin-1 (FBN1). However, the molecular mechanism underlying MFS remains poorly understood. The study aimed to explore how the L-type calcium channel (CaV1.2) modulates disease progression of MFS and to identify a potential effective target for attenuating MFS. KEGG enrichment analysis showed that the calcium signaling pathway gene set was significantly enriched. We demonstrated that FBN1 deficiency exhibited inhibition on both the expression of Cav1.2 and proliferation of vascular smooth muscle cells (VSMCs). Then, we examined whether FBN1 mediates Cav1.2 via regulating TGF-β1. Higher levels of TGF-β1 were observed in the serum and aortic tissues from patients with MFS. TGF-β1 modulated Cav1.2 expression in a concentration-dependent manner. We evaluated the role of Cav1.2 in MFS by small interfering RNA and Cav1.2 agonist Bay K8644. The effect of Cav1.2 on cell proliferation was dependent on c-Fos activity. These results demonstrated FBN1 deficiency decreased the expression levels of Cav1.2 via regulation of TGF-β1, and downregulation of Cav1.2 inhibited cell proliferation of human aortic smooth muscle cells (HASMCs) in MFS patients. These findings suggest that Cav1.2 may be an appealing therapeutic target for MFS.
Cav1.4 L-type calcium channels are predominantly expressed at the photoreceptor terminals and in bipolar cells, mediating neurotransmitter release. Mutations in its gene, CACNA1F, can cause congenital stationary night-blindness type 2 (CSNB2). Due to phenotypic variability in CSNB2, characterization of pathological variants is necessary to better determine pathological mechanism at the site of action. A set of known mutations affects conserved gating charges in the S4 voltage sensor, two of which have been found in male CSNB2 patients. Here, we describe two disease-causing Cav1.4 mutations with gating charge neutralization, exchanging an arginine 964 with glycine (RG) or arginine 1288 with leucine (RL). In both, charge neutralization was associated with a reduction channel expression also reflected in smaller ON gating currents. In RL channels, the strong decrease in whole-cell current densities might additionally be explained by a reduction of single-channel currents. We further identified alterations in their biophysical properties, such as a hyperpolarizing shift of the activation threshold and an increase in slope factor of activation and inactivation. Molecular dynamic simulations in RL substituted channels indicated water wires in both, resting and active, channel states, suggesting the development of omega (ω)currents as a new pathological mechanism in CSNB2. This sum of the respective channel property alterations might add to the differential symptoms in patients beside other factors, such as genomic and environmental deviations.
TRPV1 channel is a sensitive ion channel activated by some noxious stimuli and has been reported to change many physiological functions after its activation. In this paper, we present a scientometric approach to explore the trends of the association between TRPV1 channel and inflammation and our goal is to provide creative directions for future research. The related literature was retrieved from Web of Science Core Collection and then analyzed by CiteSpace and VOSviewer. A total of 1533 documents were screened. The most productive country, institution, journal, author, cited journal, cited author, and references were the United States, University of California, San Francisco, Pain, Lu-yuan Lee, Nature, Michael J. Caterina, and Caterina MJ (Science, 2000), respectively. The most influential country and institution were Switzerland and University of California, San Francisco, respectively. The cooperation among countries or institutions was extensive. Amounts of documents were distributed in molecular, biology, genetics. TRPV1-associated neurons, neuropeptides, neuropathic pain, neuroinflammation, and neurogenic inflammation were mainly hotspots in this field. The research has presented valuable data about previous studies in the link of TRPV1 channel and inflammation.
SLC26A9 is one out of 11 proteins that belong to the SLC26A family of anion transporters. Apart from expression in the gastrointestinal tract, SLC26A9 is also found in the respiratory system, in male tissues and in the skin. SLC26A9 has gained attention because of its modifier role in the gastrointestinal manifestation of cystic fibrosis (CF). SLC26A9 appears to have an impact on the extent of intestinal obstruction caused by meconium ileus. SLC26A9 supports duodenal bicarbonate secretion, but was assumed to provide a basal Cl- secretory pathway in airways. However, recent results show that basal airway Cl- secretion is due to cystic fibrosis conductance regulator (CFTR), while SLC26A9 may rather secrete HCO3-, thereby maintaining proper airway surface liquid (ASL) pH. Moreover, SLC26A9 does not secrete but probably supports reabsorption of fluid particularly in the alveolar space, which explains early death by neonatal distress in Slc26a9-knockout animals. While the novel SLC26A9 inhibitor S9-A13 helped to unmask the role of SLC26A9 in the airways, it also provided evidence for an additional role in acid secretion by gastric parietal cells. Here we discuss recent data on the function of SLC26A9 in airways and gut, and how S9-A13 may be useful in unraveling the physiological role of SLC26A9.
Recent human genetic studies have linked a variety of genetic variants in the CACNA1C and CACNA1D genes to neuropsychiatric and neurodevelopmental disorders. This is not surprising given the work from multiple laboratories using cell and animal models that have established that Cav1.2 and Cav1.3 L-type calcium channels (LTCCs), encoded by CACNA1C and CACNA1D, respectively, play a key role in various neuronal processes that are essential for normal brain development, connectivity, and experience-dependent plasticity. Of the multiple genetic aberrations reported, genome-wide association studies (GWASs) have identified multiple single nucleotide polymorphisms (SNPs) in CACNA1C and CACNA1D that are present within introns, in accordance with the growing body of literature establishing that large numbers of SNPs associated with complex diseases, including neuropsychiatric disorders, are present within non-coding regions. How these intronic SNPs affect gene expression has remained a question. Here, we review recent studies that are beginning to shed light on how neuropsychiatric-linked non-coding genetic variants can impact gene expression via regulation at the genomic and chromatin levels. We additionally review recent studies that are uncovering how altered calcium signaling through LTCCs impact some of the neuronal developmental processes, such as neurogenesis, neuron migration, and neuron differentiation. Together, the described changes in genomic regulation and disruptions in neurodevelopment provide possible mechanisms by which genetic variants of LTCC genes contribute to neuropsychiatric and neurodevelopmental disorders.
In this hybrid review, we have first collected and reviewed available information on the structure and function of the enigmatic cache domains in α2δ proteins. These are organized into two double cache (dCache_1) domains, and they are present in all α2δ proteins. We have also included new data on the key function of these domains with respect to amino acid and gabapentinoid binding to the universal amino acid–binding pocket, which is present in α2δ-1 and α2δ-2. We have now identified the reason why α2δ-3 and α2δ-4 do not bind gabapentinoid drugs or amino acids with bulky side chains. In relation to this, we have determined that the bulky amino acids Tryptophan and Phenylalanine prevent gabapentin from inhibiting cell surface trafficking of α2δ-1. Together, these novel data shed further light on the importance of the cache domains in α2δ proteins.
The CaV1.1 voltage-gated Ca²⁺ channel carries L-type Ca²⁺ current and is the voltage-sensor for excitation-contraction (EC) coupling in skeletal muscle. Significant breakthroughs in the EC coupling field have often been close on the heels of technological advancement. In particular, CaV1.1 was the first voltage-gated Ca²⁺ channel to be cloned, the first ion channel to have its gating current measured and the first ion channel to have an effectively null animal model. Though these innovations have provided invaluable information regarding how CaV1.1 detects changes in membrane potential and transmits intra- and inter-molecular signals which cause opening of the channel pore and support Ca²⁺ release from the sarcoplasmic reticulum remain elusive. Here, we review current perspectives on this topic including the recent application of functional site-directed fluorometry.
Calcium ions (Ca²⁺) are the basis of a unique and potent array of cellular responses. Calmodulin (CaM) is a small but vital protein that is able to rapidly transmit information about changes in Ca²⁺ concentrations to its regulatory targets. CaM plays a critical role in cellular Ca²⁺ signaling, and interacts with a myriad of target proteins. Ca²⁺-dependent modulation by CaM is a major component of a diverse array of processes, ranging from gene expression in neurons to the shaping of the cardiac action potential in heart cells. Furthermore, the protein sequence of CaM is highly evolutionarily conserved, and identical CaM proteins are encoded by three independent genes (CALM1-3) in humans. Mutations within any of these three genes may lead to severe cardiac deficits including severe long QT syndrome (LQTS) and/or catecholaminergic polymorphic ventricular tachycardia (CPVT). Research into disease-associated CaM variants has identified several proteins modulated by CaM that are likely to underlie the pathogenesis of these calmodulinopathies, including the cardiac L-type Ca²⁺ channel (LTCC) CaV1.2, and the sarcoplasmic reticulum Ca²⁺ release channel, ryanodine receptor 2 (RyR2). Here, we review the research that has been done to identify calmodulinopathic CaM mutations and evaluate the mechanisms underlying their role in disease.
Piezo1 is upregulated in human OC tissues. (a) Analyses of Piezo1 mRNA expression, and (b) protein expression by Western blot in human primary OC tissues and adjacent non-tumor tissues. Data were expressed as mean ± SD. ***p < 0.001.
Piezo1 knockdown inhibited OC growth in vivo. (a) Tumor volume of A-1847 xenografts with or without Piezo1 knockdown. n = 6 for each group. (b) Piezo1 mRNA levels of tumor collected from different groups. Data were expressed as mean ± SD. *p < 0.05.
Knockdown of Piezo1 gene expression suppressed cell migration in A-1847 cells. (a) mRNA and (b-c) protein expression of Piezo1 in A-1847 cells after knockdown using Piezo1-shRNA. (d) Wound disclosure rate of A-1847 cells with or without Piezo1 knockdown. Data were expressed as mean ± SD. **p < 0.01.
Piezo1 promotes OC lung metastasis. (a) Western blot and (b) Semi-quantitative analysis of protein expression of EMTrelated molecules in metastatic nodules. Data were expressed as mean ± SD, n = 3. *p < 0.05, **p < 0.01, ***p < 0.001.
Ovarian cancer (OC) is a highly malignant cancer with great metastatic potential. Here we aimed to investigate the role of Piezo1, a gene related to the mechanical environment of the tumor, in promoting the metastasis of OC. We performed Piezo1 knockdown in A-1847 cells using small hairpin RNAs, and the cells were inoculated subcutaneously in nude mice. Piezo1 knockdown decreased the tumor growth rate of OC tumor xenografts in mice and reduced cell migration in vitro. Metastasis in the lung was also attenuated after Piezo1 knockdown as revealed by HE staining of the lung tissues, which was concomitant with downregulation of E-Cadherin and vimentin and upregulation of N-Cadherin analyzed using western blot analysis, suggesting suppressed epithelial-to-mesenchymal transition. Migration of Piezo1-knockdown cells was also analyzed for their migratory capabilities using the scratch assay. We also analyzed the key proteins in the Hippo/YAP signaling pathway using western blot after treating A-1847 and 3AO cells with a Piezo1 inducer, Yoda1. Piezo1 inducer Yoda1 activated Hippo/YAP signal in OC cells. In conclusion, Piezo1 is overexpressed in OC tissues and contributes to OC tumor growth and metastasis. Suppression of Piezo1 is a potential therapeutic strategy for OC.
Started as an academic curiosity more than two decades ago, the idea that ion channels can regulate cellular processes in ways that do not depend on their conducting properties (non-ionic functions) gained traction and is now a flourishing area of research. Channels can regulate physiological processes including actin cytoskeletal remodeling, cell motility, excitation-contraction coupling, non-associative learning and embryogenesis, just to mention some, through non-ionic functions. When defective, non-ionic functions can give rise to channelopathies involved in cancer, neurodegenerative disease and brain trauma. Ion channels exert their non-ionic functions through a variety of mechanisms that range from physical coupling with other proteins, to possessing enzymatic activity, to assembling with signaling molecules. In this article, we take stock of the field and review recent findings. The concept that emerges, is that one of the most common ways through which channels acquire non-ionic attributes, is by assembling with integrins. These integrin-channel complexes exhibit broad genotypic and phenotypic heterogeneity and reveal a pleiotropic nature, as they appear to be capable of influencing both physiological and pathological processes.
Electrocardiogram after yew poisoning showing an irregular arrhythmia at a rate of 107/min with bizarre QRS prolongation.
Ineffective defibrillation after ingestion of Taxus baccata (a) Irregular wide complex tachycardia terminating to arterial flutter without ventricular response. Seconds later, broad ventricular complexes appear that quickly degenerate into the irregular wide complex tachycardia. (b) Irregular wide complex tachycardia terminating to arterial flutter without ventricular response. (c-f) Ineffective defibrillation of wide complex tachycardia.
Gastroscopy showing copious foliage of Taxus baccata.
Sequential electrocardiograms 2 ½ h (a) 3 h (b), 18 h (c), and 22 h (d) after ingestion of Taxus baccata.
Ingestion of leaves of the European yew tree (Taxus baccata) can result in fatal cardiac arrhythmias and acute cardiogenic shock. This cardiotoxicity derives from taxine alkaloids that block cardiac voltage-gated sodium and calcium channels. Prompt initiation of venoarterial extracorporeal membrane oxygenation is essential to bridge these critically ill patients to recovery, as there is no antidote available. We here report a 39-year old patient with toxic cardiogenic shock after yew poisoning, who was successfully rescued by venoarterial extracorporeal membrane oxygenation and had a full neurological recovery. This report emphasizes the role of intoxications as reversible causes of cardiac arrest and adds further evidence to the body of existing literature thus encouraging the early use of venoarterial extracorporeal membrane oxygenation in patients with yew poisoning and cardiogenic shock.
Detection of Piezo1, NOTCH3, RANKL/OPG in MLO-Y4 osteocytes a. The tSNE plot of the mesenchymal lineage cells; b. The bubble plot of the expression of Piezo1, NOTCH3, RANKL, and OPG among the mesenchymal lineage cells; c-d. The expression patterns of Piezo1 in tSNE plot and the violin plot; e-f. The expression patterns of NOTCH3 in tSNE plot and the violin plot; g-h. The expression patterns of RANKL in tSNE plot and the violin plot; i-j. The expression patterns of OPG in tSNE plot and the violin plot. Piezo1, Piezo Type Mechanosensitive Ion Channel Component 1; NOTCH3, Notch Receptor 3; RANKL, Receptor Activator of Nuclear Factor Kappa b Ligand; OPG, Osteoprotegerin; MALP, marrow adipogenic lineage precursor; IMP, intermediate mesenchymal progenitor; LCP, lineage committed progenitor; LMP, late mesenchymal progenitor; OB, osteoblast; EMP, early mesenchymal progenitor; Ocy, osteocyte.
Activation of Piezo1 inhibits the expression of NOTCH3 and RANKL, promotes the expression of OPG MLO-Y4 cells were treated with Yoda1 (10uM) for 2 h, GsMTx4 (4uM) for 0.5 h. a. Western blot analysis of the protein expression levels of Piezo1, NOTCH3, RANKL, and OPG in MLO-Y4 cells; b-e. The ratios of Piezo1/β-actin, NOTCH3/β-actin, RANKL/β-actin, and OPG/β-actin in different groups were quantified; f-i. qRT-PCR analysis of mRNA expression levels of Piezo1, NOTCH3, RANKL, and OPG in MLO-Y4 cells. Data are shown as "mean ± SD" of at least three independent experiments. *P < 0.05, **P < 0.01, ***P < 0.001.
FSS-mediated Piezo1 down-regulates the expression of NOTCH3 and RANKL, up-regulates the expression of OPG MLO-Y4 cells were treated with FSS (9dyne/cm 2 , 30 min), GsMTx4 (4uM) for 0.5 h, and FSS + GsMTx4 (4uM) for 0.5 h. a. Western blot analysis of the protein expression levels of NOTCH3, RANKL, and OPG in MLO-Y4 cells; b-d. The ratios of NOTCH3/β-actin, OPG/β-actin, and RANKL/β-actin in different groups were quantified; e-g. qRT-PCR analysis of mRNA expression levels of NOTCH3, OPG, and RANKL in MLO-Y4 cells. Data are shown as "mean ± SD" of at least three independent experiments. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.
Down-regulation of NOTCH3 inhibits the effect of GsMTx4-blocked Piezo1 on RANKL and OPGA-C. MLO-Y4 cells were transfected with negative controls (NC), siRNA-NOTCH3-1, −2, or −3. a. Western blot analysis of the protein expression level of NOTCH3 in MLO-Y4 cells; b. The ratios of NOTCH3/β-actin in different groups were quantified; c. qRT-PCR analysis of mRNA expression levels of NOTCH3 in MLO-Y4 cells. d-h. MLO-Y4 cells were treated with GsMTx4 (4uM) for 0.5 h, GsMTx4 + NC, and GsMTx4 + siRNA-NOTCH3-3. e-f. The ratios of OPG/β-actin, and RANKL/β-actin in different groups were quantified; g-h. qRT-PCR analysis of mRNA expression levels of OPG, and RANKL in MLO-Y4 cells. Data are shown as "mean ± SD" of at least three independent experiments. *P < 0.05, **P < 0.01, ***P < 0.001.
The schematic of the roles of how FSS-mediated Piezo1 ion channel regulates the expression of RANKL/OPG via NOTCH3 in osteocytes. FSS-mediated up-regulation of Piezo1 promotes the expression of OPG and inhibits the expression of RANKL via NOTCH3.
Piezo1, a mechanosensitive ion channel, participates in a variety of biological processes in maintaining bone homeostasis. As the most abundant cells in bones of the mammals, osteocytes play an essential role in bone formation, remodeling, and bone mass maintenance. Here, by exposing MLO-Y4 osteocytes to the fluid shear stress (FSS) microenvironment, we explored the effect of Piezo1-mediated FSS on the expression of the molecules critical to the process of bone formation and resorption, Receptor Activator of Nuclear Factor-Kappa-B Ligand (RANKL) and Osteoprotegerin (OPG). It was found that 9 dyne/cm² loading for 30 minutes showed an upregulation trend on Piezo1 when MLO-Y4 osteocytes were exposed to an FSS microenvironment. FSS promotes the expression of OPG and inhibits the expression of RANKL. The blocker of Piezo1, GsMTx4, downregulates the effect of FSS on the expression of these two molecules. In addition, NOTCH3 was involved in this process. Thus, the results demonstrated that Piezo1-mediated FSS promotes the expression of OPG and inhibits the expression of RANKL via NOTCH3 in MLO-Y4 osteocytes.
Spatial working memory assessed by the eight-arm radial maze and T-maze tasks in tg/+ and tg/tg mice. (a), (b) Acquisition of the eight-arm radial maze task of tg mutant mice (n = 7 for +/+, n = 8 for tg/+, and n = 8 for tg/tg). Total errors in a trial (a) and correct responses in the first eight choices (b) in the eight-arm radial maze averaged over two trials per session. (c), (d) Delayed non-matching-to-position task in the T-maze (n = 7 for +/+, n = 8 for tg/+, and n = 8 for tg/tg). Proportion of correct responses during training (c) and in delay trials (d). Data represent the mean ± SEM or mean + SEM.
CACNA1A-associated epilepsy and ataxia frequently accompany cognitive impairments as devastating co-morbidities. However, it is unclear whether the cognitive deficits are consequences secondary to the neurological symptoms elicited by CACNA1A mutations. To address this issue, Cacna1a mutant mice tottering (tg), and in particular tg/+ heterozygotes, serve as a suitable model system, given that tg/+ heterozygotes fail to display spontaneous absence epilepsy and ataxia typically observed in tg/tg homozygotes. Here, we examined hippocampus-dependent behaviors and hippocampal learning-related synaptic plasticity in tg mice. In behavioral analyses of tg/+ and tg/tg, acquisition and retention of spatial reference memory were characteristically impaired in the Morris water maze task, while working memory was intact in the eight-arm radial maze and T-maze tasks. tg/+ heterozygotes showed normal motor function in contrast to tg/tg homozygotes. In electrophysiological analyses, Schaffer collateral–CA1 synapses showed a deficit in the maintenance of long-term potentiation in tg/+ and tg/tg mice and an increased paired-pulse facilitation induced by paired pulses with 100 ms in tg/tg mice. Our results indicate that the tg mutation causes a dominant disorder of the hippocampus-related memory and synaptic plasticity, raising the possibility that in CACNA1A-associated human diseases, functionally aberrant CaV2.1 Ca²⁺ channels actively induce the observed cognitive deficits independently of the neurological symptoms.
Amphipathic compounds inhibit voltage-gated Na + currents from Na V 1.5 channels expressed in HEK293 cells. (a), Molecular structures of the amphipaths (from left to right): amiodarone, capsaicin, propranolol, and Triton X-100. (b-c), Representative Na + currents elicited by a step from −120 to the −35-mV test voltage (b), and peak Na + current-voltage plots across all test voltages (c) with 10 −9 to 10 − [4] M (blue-red spectrum) of membrane-permeable amphipathic compounds in the extracellular solution. (d), Dose-response curves for maximum peak Na + current of Na V 1.5 vs. amphipathic concentration; IC 50 values: amiodarone, 8.4 µM; capsaicin, 60.2 µM; propranolol, 7.6 µM; Triton X-100, 5.3 µM.
Capsaicin inhibits pressure-and shear-sensitivity of Na V 1.5. (a), Representative Na V 1.5 currents elicited by voltage ladders ranging −100 to 0 mV in a cell-attached patch (a) or −120 mV to −30 mV in a whole cell (b), recorded at rest (filled symbols) or with force (empty symbols), in the presence of 0 µM (black) or 20 µM capsaicin (red). Difference currents were constructed by subtracting the control Na + currents from the pressure-(a) or shear-stimulated (b) currents. (c-d), Steady-state activation (c) and inactivation (d) curves of Na + currents in cell-attached patches (left) or whole cells (right), recorded at rest (filled symbols) or with force (empty symbols), in the presence of 0 µM (black) or 20 µM capsaicin (red). (e-h), Maximum peak Na + current (e), time constant of activation (f), and voltage dependence of activation (g, V 1/2A ) or inactivation (h, V 1/2I ), recorded with 0 or −30 mmHg pressure in the patch (left) and 0 or 10 mL/min flow rate in whole cells (right) in the presence of 0 µM (black) or 20 µM capsaicin (red). n = 12-24 cells, *P < 0.05 comparing 0 to −30 mmHg or 0 to 10 mL/min, †P < 0.05 comparing 0 to 20 µM capsaicin by a 2-way ANOVA with Tukey posttest.
Effects of capsaicin on mechanosensitivity of Na V 1.5 inactivation recovery time. (a-b), Representative Na V 1.5 currents at −20 mV in a cell-attached patch (a, •) or −30 mV in a whole cell (b, ■), elicited after recovering from the control step for 3-300 ms at −120 mV (a) or 3-1000 ms at −130 mV (b). Na + currents were recorded at rest (gray) or with force (black and red traces: a, −30 mmHg pressure; b, 10 mL/min shear stress) in the presence of 0 µM (top) or 20 µM capsaicin (bottom). (c-d), Normalized peak Na + current versus recovery time in the presence of 0 µM (black) or 20 µM capsaicin (red), at 0 (•) or −30 mmHg pressure (○) in the patch (c) or at 0 (■) or 10 mL/min (□) shear stress in whole cells (d). (e-f), Inactivation recovery times (t 1/2 ) versus 0 or −30 mmHg pressure in the patch (e) and 0 or 10 mL/min shear stress in whole cells (f) with 0 µM (black) or 20 µM capsaicin (red). n = 8-11 cells, *P < 0.05 comparing 0 to −30 mmHg or 0 to 10 mL/ min, †P < 0.05 comparing 0 to 20 µM capsaicin by a 2-way ANOVA with Tukey posttest.
Effects of capsaicin on mechanosensitivity of Na V 1.5 use-dependent inactivation. (a-b), Representative Na V 1.5 currents at the 20 th step to −20 mV in a cell-attached patch (A, ·) or to −40 mV in a whole cell (b, ■), elicited at intersweep frequencies 3-33 Hz (a) or 3-50 Hz (b). Na + currents were recorded at rest (gray) or with force (black and red traces: a, −30 mmHg pressure; b, 10 mL/min shear stress) in the presence of 0 µM (top) or 20 µM capsaicin (bottom). (c-d), Use-dependent inhibition of peak Na + current versus intersweep frequency in the presence of 0 µM (black) or 20 µM capsaicin (red), at 0 (•) or −30 mmHg pressure (○) in the patch (c) or at 0 (■) or 10 mL/min (□) shear stress in whole cells (d). (e-f), Maximum use-dependent inhibition (e) or frequency of use-dependent inhibition (f) versus pressure in the patch (left) and shear stress in whole cells (right) with 0 µM (black) or 20 µM capsaicin (red). n = 8-18 cells, *P < 0.05 comparing 0 to −30 mmHg or 0 to 10 mL/min, †P < 0.05 comparing 0 to 20 µM capsaicin by a 2-way ANOVA with Tukey posttest.
SCN5A-encoded NaV1.5 is a voltage-gated Na+ channel that drives the electrical excitability of cardiac myocytes and contributes to slow waves of the human gastrointestinal smooth muscle cells. NaV1.5 is mechanosensitive: mechanical force modulates several facets of NaV1.5’s voltage-gated function, and some NaV1.5 channelopathies are associated with abnormal NaV1.5 mechanosensitivity (MS). A class of membrane-active drugs, known as amphiphiles, therapeutically target NaV1.5’s voltage-gated function and produce off-target effects including alteration of MS. Amphiphiles may provide a novel option for therapeutic modulation of NaV1.5’s mechanosensitive operation. To more selectively target NaV1.5 MS, we searched for a membrane-partitioning amphipathic agent that would inhibit MS with minimal closed-state inhibition of voltage-gated currents. Among the amphiphiles tested, we selected capsaicin for further study. We used two methods to assess the effects of capsaicin on NaV1.5 MS: (1) membrane suction in cell-attached macroscopic patches and (2) fluid shear stress on whole cells. We tested the effect of capsaicin on NaV1.5 MS by examining macro-patch and whole-cell Na+ current parameters with and without force. Capsaicin abolished the pressure- and shear-mediated peak current increase and acceleration; and the mechanosensitive shifts in the voltage-dependence of activation (shear) and inactivation (pressure and shear). Exploring the recovery from inactivation and use-dependent entry into inactivation, we found divergent stimulus-dependent effects that could potentiate or mitigate the effect of capsaicin, suggesting that mechanical stimuli may differentially modulate NaV1.5 MS. We conclude that selective modulation of NaV1.5 MS makes capsaicin a promising candidate for therapeutic interventions targeting MS.
The transient receptor potential vanilloid (TRPV) family has been preliminarily discovered to play an important role in various cancers, including clear cell renal cell carcinoma (ccRCC), which is closely associated with immune infiltration. However, the expression and prognosis of TRPV family and tumor-infiltrating immune cells in ccRCC are obscure. This study aimed to explore the prognostic and therapeutic value of the TRPV family expression in ccRCC from the perspective of bioinformatics. We analyzed the transcriptome and clinical data of kidney renal clear cell carcinoma (KIRC) from The Cancer Genome Atlas (TCGA) database. A clustering analysis and immune infiltration analysis were conducted to investigate the influence of the TRPV family genes on ccRCC. Our study found that the TRPV family is an excellent prognostic stratification for ccRCC. Among them, TRPV3 is the most significant prognostic marker of ccRCC. In addition, we performed a drug sensitivity analysis to identify the drugs with the strongest association with TRPV3. As a result, the TRPV family, particularly TRPV3, can act as a prognostic biomarker in ccRCC to determine prognosis and levels of immune infiltration.
JZTX-V is a toxin isolated from the venom of the Chinese spider Chilobrachys jingzhao. Previous studies had shown that JZTX-V could inhibit the transient outward potassium current of Kv4.2 and Kv4.3 expressed in Xenopus oocytes but had no effects on Kv1.2–1.4. However, the underlying action mechanism of JZTX-V on Kv4.3 remains unclear. In our study, JZTX-V could inhibit not only transient outward potassium currents evoked in small-sized DRG neurons but also Kv4.3-encoded currents expressed in HEK293T cells in the concentration and voltage dependence. The half maximal inhibitory concentration of JZTX-V on Kv4.3 was 9.6 ± 1.2 nM. In addition, the time course for JZTX-V inhibition and release of inhibition after washout were 15.8 ± 1.54 s and 58.8 ± 4.35 s. Electrophysiological assays indicated that 25 nM JZTX-V could shift significantly the voltage dependence of steady-state activation and steady-state inactivation to depolarization. Meanwhile, 25 nM JZTX-V decreased markedly the time constant of activation and inactivation but had no effect on the time constant of recovery from inactivation. To study the molecular determinants of Kv4.3, we performed alanine scanning on a conserved motif of Kv4.3 and assayed the affinity between mutants and JZTX-V. The results not only showed that I273, L275, V283, and F287 were molecular determinants in the conserved motif of Kv4.3 for interacting with JZTX-V but also speculated the underlying action mechanism that the hydrophobic interaction and steric effects played key roles in the binding of JZTX-V with Kv4.3. In summary, our studies have laid a scientific theoretical foundation for further research on the interaction mechanism between JZTX-V and Kv4.3.
In recent years, AMPK channel has gained considerable attention in a variety of research areas, and several academic journals have published articles on AMPK research. However, few attempts have been made to thoroughly assess the scientific output and current status systematically in this topic from a worldwide viewpoint. As a result, it is critical to adopt an appropriate visualization method to reveal the global status, future research trends, and hotspots in AMPK channel research. To investigate research hotspots/frontiers in certain domains, bibliometric analysis has been frequently utilized to determine the productivity of nations, institutions, authors, and the frequency of keywords. In this work, we used CiteSpace and VOSviewer to conduct a bibliometric analysis of AMPK channel studies from 2012 to 2021 in order to perform researchers with some directions for AMPK channel research.
Compound 194 inhibits evoked and affective pain in rats with chronic constriction injury (CCI). (a) Schematic of the mode of action of compound 194 which uncouples the interaction between CRMP2 and the E2 SUMO-conjugating enzyme Ubc9 to prevent CRMP2 SUMOylation and reduces NaV1.7 cell-surface localization. This reduces sodium currents to alleviate pain. Image generated with BioRender. (b) Mechanical withdrawal thresholds were assessed in adult male rats before injury to establish a baseline and following injury to demonstrate the development of mechanical allodynia. Rats were then orally administered compound 194, which reversed mechanical allodynia in the CCI group (pink squares) compared to the CCI animals given the vehicle (gray squares) (CCI-Vehicle vs. CCI-194, p = 0.0001 at 2 hours post injection). This effect peaked at 2 hours post administration before the animals returned to their postsurgery baseline sensitivity level. (c) Nociception was evaluated using the operator-independent mechanical conflict-avoidance assay. Naïve rats treated with 194 (pink squares) had the same latency to cross an aversive sharp surface as their vehicle treated counterparts (gray circles). Animals that had neuropathic pain induced by CCI had a profoundly increased latency to cross the aversive surface to escape the brightly lit enclosure (gray circles, right). Treatment with 194 significantly reduced the time to cross the aversive surface (pink squares, right) indicating reduced mechanical allodynia. (For B, multiple Mann-Whitney tests, n = 8 per group; for C, two-way ANOVA, naïve vehicle vs CCI vehicle, p = 0.0036; naïve 194 vs CCI vehicle, p = 0.0004; CCI vehicle vs CCI 194, p = 0.0045, n = 8 per group).
The voltage-gated sodium channel isoform NaV1.7 is a critical player in the transmission of nociceptive information. This channel has been heavily implicated in human genetic pain disorders and is a validated pain target. However, targeting this channel directly has failed, and an indirect approach – disruption of interactions with accessory protein partners – has emerged as a viable alternative strategy. We recently reported that a small-molecule inhibitor of CRMP2 SUMOylation, compound 194, selectively reduces NaV1.7 currents in DRG neurons across species from mouse to human. This compound also reversed mechanical allodynia in a spared nerve injury and chemotherapy-induced model of neuropathic pain. Here, we show that oral administration of 194 reverses mechanical allodynia in a chronic constriction injury (CCI) model of neuropathic pain. Furthermore, we show that orally administered 194 reverses the increased latency to cross an aversive barrier in a mechanical conflict-avoidance task following CCI. These two findings, in the context of our previous report, support the conclusion that 194 is a robust inhibitor of NaV1.7 function with the ultimate effect of profoundly ameliorating mechanical allodynia associated with nerve injury. The fact that this was observed using both traditional, evoked measures of pain behavior as well as the more recently developed operator-independent mechanical conflict-avoidance assay increases confidence in the efficacy of 194-induced anti-nociception.
ATP-sensitive K+ (KATP) channel couples membrane excitability to intracellular energy metabolism. Maintaining KATP channel surface expression is key to normal insulin secretion, blood pressure and cardioprotection. However, the molecular mechanisms regulating KATP channel internalization and endocytic recycling, which directly affect the surface expression of KATP channels, are poorly understood. Here we used the cardiac KATP channel subtype, Kir6.2/SUR2A, and characterized Rab35 GTPase as a key regulator of KATP channel endocytic recycling. Electrophysiological recordings and surface biotinylation assays showed decreased KATP channel surface density with co-expression of a dominant negative Rab35 mutant (Rab35-DN), but not other recycling-related Rab GTPases, including Rab4, Rab11a and Rab11b. Immunofluorescence images revealed strong colocalization of Rab35-DN with recycling Kir6.2. Rab35-DN minimized the recycling rate of KATP channels. Rab35 also regulated KATP channel current amplitude in isolated adult cardiomyocytes by affecting its surface expression but not channel properties, which validated its physiologic relevance and the potential of pharmacologic target for treating the diseases with KATP channel trafficking defects.
Carvedilol prolongs the refractoriness of the SR calcium release. A, Double pulse (S1-S2) protocol used to record Ca currents (I Ca ) and CaT simultaneously in atrial myocytes. Series of S1-S2 stimulations were applied with progressively decreased diastolic intervals (DI) from 1,000 to 2 ms. B, Representative traces of I Ca (top) and corresponding [Ca] i profiles (bottom) in control. C, Representative traces of I Ca (top) and corresponding [Ca] i profiles (bottom) in presence of carvedilol (0.75 µM). D, I Ca recovery from inactivation (RFI) curves in control (gray symbols) and in presence of carvedilol (open symbols). Dashed lines indicate time constant τ of I Ca RFI kinetics derived from mono-exponential fit. Inset: average τ of I Ca RFI (P = 0.091, n = 6, paired t-test). E, CaT and SR Ca release refractoriness in control (gray symbols) and carvedilol (open symbols). Inset: average time constant τ (mono-exponential fit) of CaT RFI (P = 0.024, n = 6, paired t-test).
Carvedilol induces APD alternans. A, Representative AP traces recorded in control and in presence of carvedilol (0.75 µM) at 1 Hz. B, Overlay of 2 consecutive APs in control and carvedilol treated cells (marked by box in panel A). APs were recorded in current-clamp mode and evoked by 5 ms stimulation pulses of a magnitude ~1.5 times higher than AP activation threshold. C, APD of a pair of consecutive APs were classified as long (l) and short (s) based on APD50 analysis. Comparison of control and carvedilol mean APD50 of long (L: P = 0.19; n = 11) and short (S: P = 0.24) APs. D, AR APD50 in control and after carvedilol (P = 0.096). E, Representative AP traces recorded in control and in presence of carvedilol (0.75 µM) at 2 Hz. F, Overlay of 2 consecutive APs in control and carvedilol treated cells (marked by box in panel E). G, Comparison of control and carvedilol mean APD50 of long (L: P = 0.12; n = 9) and short (S: P = 0.037) APs. H, Average AR APD50 in control and after carvedilol treatment (P = 0.034). Statistical analysis with paired t-test.
Carvedilol increases APD50 and CaT alternans ratios. Simultaneous AP and [Ca] i recordings in control (A) and in presence of 0.75 µM carvedilol (B) using the fluorescent probes FluoVolt and Rhod-2. V m and [Ca] i signals were acquired in confocal transverse line scan mode. AP and CaT were elicited by field stimulation at 2 Hz. C, Mean APDs at 50% repolarization (APD50) of long (L) and short (S) APs (panel a) and AR APD50 (panel b) in control and in presence of carvedilol (n = 19). Statistical analysis with unpaired t-test. D, mean amplitudes of small (S) and large (L) alternans CaTs (panel a) and average CaT ARs (panel b) in control and in presence of carvedilol. E, Correlation between AR APD50 and CaT AR in control (a) and carvedilol (b) treated cells. r, correlation coefficient. F, distribution of AR APD50 (panel a) and CaT AR (panel b) in control (gray bars) and in presence of carvedilol (open bars).
Metoprolol does not modify APD or CaT alternans. V m and [Ca] i traces from atrial myocytes in control (A) and during metoprolol (10 µM) treatment (B). APs and CaTs were elicited by field stimulation at 2 Hz. C, Mean APD50 of long (L; control vs. metoprolol: P = 0.35, n = 11) and short (S; P = 0.21) APs during alternans (panel a) and average AR APD50 (panel b) in control and metoprolol (Met; P = 0.37, n = 11). D, average CaT amplitudes of large (L: control vs. metoprolol, P = 0.43) and small (S; P = 0.29) amplitude alternans CaTs (panel a) and average CaT AR (panel b) in control and metoprolol (P = 0.41). Statistical analysis with unpaired t-test.
Carvedilol is a nonspecific β-blocker clinically used for the treatment of cardiovascular diseases but has also been shown to have profound effects on excitation-contraction coupling and Ca signaling at the cellular level. We investigate the mechanism by which carvedilol facilitates Ca transient (CaT) and action potential duration (APD) alternans in rabbit atrial myocytes. Carvedilol lowered the frequency threshold for pacing-induced CaT alternans and facilitated alternans in a concentration-dependent manner. Carvedilol prolonged the sarcoplasmic reticulum (SR) Ca release refractoriness by significantly increasing the time constant τ of recovery of SR Ca release; however, no changes in L-type calcium current recovery from inactivation or SR Ca load were found after carvedilol treatment. Carvedilol enhanced the degree of APD alternans nearly two-fold. Carvedilol slowed the APD restitution kinetics and steepened the APD restitution curve at the pacing frequency (2 Hz) where alternans were elicited. No effect on the CaT or APD alternans ratios was observed in experiments with a different β-blocker (metoprolol), excluding the possibility that the carvedilol effect on CaT and APD alternans was determined by its β-blocking properties. These data suggest that carvedilol contributes to the generation of CaT and APD alternans in atrial myocytes by modulating the restitution of CaT and APD.
Myotonia congenita (MC) is a rare genetic disease caused by mutations in the skeletal muscle chloride channel gene (CLCN1), encoding the voltage-gated chloride channel ClC-1 in skeletal muscle. Our study reported the clinical and molecular characteristics of six patients with MC and systematically review the literature on Chinese people. We retrospectively analyzed demographics, clinical features, family history, creatine kinase (CK), electromyography (EMG), treatment, and genotype data of our patients and reviewed the clinical data and CLCN1 mutations in literature. The median ages at examination and onset were 26.5 years (range 11-50 years) and 6.5 years (range 1.5-11 years), respectively, in our patients, and 21 years (range 3.5-65 years, n = 45) and 9 years (range 0.5-26 years, n = 50), respectively, in literature. Similar to previous reports, myotonia involved limb, lids, masticatory, and trunk muscles to varying degrees. Warm-up phenomenon (5/6), percussion myotonia (3/5), and grip myotonia (6/6) were common. Menstruation triggered myotonia in females, not observed in Chinese patients before. The proportion of abnormal CK levels (4/5) was higher than data from literature. Electromyography performed in six patients revealed myotonic changes (100%). Five novel CLCN1 mutations, including a splicing mutation (c.853 + 4A>G), a deletion mutation (c.2010_2014del), and three missense mutations (c.2527C>T, c.1727C>T, c.2017 G > C), were identified. The c.892 G > A (p.A298T) mutation was the most frequent mutation in the Chinese population. Our study expanded the clinical and genetic spectrum of patients with MC in the China. The MC phenotype in Chinese people is not different from that found in the West, while the genotype is different.
Chemical structures of DCPIB, Pranlukast, Zafirlukast, and ZPT.
(a) cartoon representation of a HEK293-YFP(F46L/H148Q/I152L) cell used in the YFP quenching assay. HEK293 cells are engineered to constitutively express YFP(F46L/H148Q/I152L). Endogenous VRAC is activated by a hypotonic challenge allowing iodide influx and subsequent YFP quenching. (b) scatter plot of the 1,184 FDA drug compounds screened. A 3 standard deviation from the mean cutoff was implicated to identify compounds as "hits." Compounds that slowed the rate of fluorescence quenching had positive values, and compounds that increased fluorescence quenching had negative values. (c) representative traces of YFPquenching assay with 10 µM ZPT. Traces were normalized to mean of five baseline fluorescent measurements taken at the start of the experiment. Hypotonic solution (130 mOsm) containing DMSO (vehicle) or drug compound was added 10s after the start of the experiment. After 5-min incubation period, 100 mM NaI is added and fluorescence quenching is observed. Fluorescence measurements were taken throughout the entirety of the experiment. Figure is adapted from Figueroa and Denton 2021. AJP-Cell Physiology.
Cartoon depiction of LRRC8 subunit membrane topology. Transmembrane domains are numbered 1-4. Extracellular loop domains 1 (EL1) and 2 (EL2), intracellular loop (IL), and leucine-rich repeat (LRR) domains are also shown.
Newly emerging roles of LRRC8 volume-regulated anion channels (VRAC) raise important questions about the therapeutic potential of VRAC in the treatment of epilepsy, type 2 diabetes, and other human diseases. A critical barrier to evaluating whether VRAC represents a viable drug target is the lack of potent and specific small-molecule inhibitors and activators of the channel. Here we review recent progress in developing the molecular pharmacology of VRAC made by screening a library of FDA-approved drugs for novel channel modulators. We discuss the discovery and characterization of cysteinyl leukotriene receptor antagonists Pranlukast and Zafirlukast as novel VRAC inhibitors, and zinc pyrithione (ZPT), which apparently activates VRAC through a reactive oxygen species (ROS)-dependent mechanism. These ongoing efforts set the stage for developing a pharmacological toolkit for probing the integrative physiology, molecular pharmacology, and therapeutic potential of VRAC.
As part of a drug discovery effort to identify potent inhibitors of NaV1.7 for the treatment of pain, we observed that inhibitors produced unexpected cardiovascular and respiratory effects in vivo. Specifically, inhibitors administered to rodents produced changes in cardiovascular parameters and respiratory cessation. We sought to determine the mechanism of the in vivo adverse effects by studying the selectivity of the compounds on NaV1.5, NaV1.4, and NaV1.6 in in vitro and ex vivo assays. Inhibitors lacking sufficient NaV1.7 selectivity over NaV1.6 were associated with respiratory cessation after in vivo administration to rodents. Effects on respiratory rate in rats were consistent with effects in an ex vivo hemisected rat diaphragm model and in vitro NaV1.6 potency. Furthermore, direct blockade of the phrenic nerve signaling was observed at exposures known to cause respiratory cessation in rats. Collectively, these results support a significant role for NaV1.6 in phrenic nerve signaling and respiratory function.
Schematic diagram of ankyrin's channel and transporter interactions in the nervous system [106]. These include (a) in neurons (1) AnkR, AnkB, and AnkG in the somatodendritic domain, (2) AnkG at the AIS, and (3) AnkG and AnkR at the nodes of Ranvier; (b) AnkR, AnkB, and AnkG at the NMJ; and (c) AnkB and AnkG in rods photoreceptors.
Schematic diagram of ankyrin's channel and transporter interactions in the periphery [106]. These include, (a) AnkR in erythrocytes, (b) AnkG in epithelial cells, and (c) AnkB and AnkG in cardiomyocytes.
Summary of the ankyrin protein's known channel and transporter interactions.
The ankyrin proteins (Ankyrin-R, Ankyrin-B, and Ankyrin-G) are a family of scaffolding, or membrane adaptor proteins necessary for the regulation and targeting of several types of ion channels and membrane transporters throughout the body. These include voltage-gated sodium, potassium, and calcium channels in the nervous system, heart, lungs, and muscle. At these sites, ankyrins recruit ion channels, and other membrane proteins, to specific subcellular domains, which are then stabilized through ankyrin’s interaction with the submembranous spectrin-based cytoskeleton. Several recent studies have expanded our understanding of both ankyrin expression and their ion channel binding partners. This review provides an updated overview of ankyrin proteins and their known channel and transporter interactions. We further discuss several potential avenues of future research that would expand our understanding of these important organizational proteins.
Voltage-gated sodium and calcium channels (VGSCs and VGCCs) play an important role in the modulation of physiologically relevant processes in excitable cells that range from action potential generation to neurotransmission. Once their expression and/or function is altered in disease, specific pharmacological approaches become necessary to mitigate the negative consequences of such dysregulation. Several classes of small molecules have been developed with demonstrated effectiveness on VGSCs and VGCCs; however, off-target effects have also been described, limiting their use and spurring efforts to find more specific and safer molecules to target these channels. There are a great number of plants and herbal preparations that have been empirically used for the treatment of diseases in which VGSCs and VGCCs are involved. Some of these natural products have progressed to clinical trials, while others are under investigation for their action mechanisms on signaling pathways, including channels. In this review, we synthesize information from ~30 compounds derived from natural sources like plants and fungi and delineate their effects on VGSCs and VGCCs in human disease, particularly pain.
Mechanosensitive ion channels are integral membrane proteins ubiquitously present in bacteria, archaea, and eukarya. They act as molecular sensors of mechanical stress to serve vital functions such as touch, hearing, osmotic pressure, proprioception and balance, while their malfunction is often associated with pathologies. Amongst them, the structurally distinct MscL and MscS channels from bacteria are the most extensively studied. MscS-like channels have been found in plants and Schizosaccharomyces pombe, where they regulate intracellular Ca2+ and cell volume under hypo-osmotic conditions. Here we characterize two MscS-like putative channels, named MscA and MscB, from the model filamentous fungus Aspergillus nidulans. Orthologues of MscA and MscB are present in most fungi, including relative plant and animal pathogens. MscA/MscB and other fungal MscS-like proteins share the three transmembrane helices and the extended C-terminal cytosolic domain that form the structural fingerprint of MscS-like channels with at least three additional transmembrane segments than Escherichia coli MscS. We show that MscA and MscB localize in Endoplasmic Reticulum and the Plasma Membrane, respectively, whereas their overexpression leads to increased CaCl2 toxicity or/and reduction of asexual spore formation. Our findings contribute to understanding the role of MscS-like channels in filamentous fungi and relative pathogens.
Chemical structures of N-arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG), two major endogenous cannabinoids (endocannabinoids). (a) AEA. (b) 2-AG.
CB1/CB2 receptor-independent effects of endocannabinoids or analogs on potassium channels.
CB1/CB2 receptor-independent effects of AEA on additional ion channel types.
Endocannabinoids are a group of endogenous mediators derived from membrane lipids, which are implicated in a wide variety of physiological functions such as blood pressure regulation, immunity, pain, memory, reward, perception, reproduction, and sleep. N-Arachidonoylethanolamine (anandamide; AEA) and 2-arachidonoylglycerol (2-AG) represent two major endocannabinoids in the human body and they exert many of their cellular and organ system effects by activating the Gi/o protein-coupled, cannabinoid type 1 (CB1) and type 2 (CB2) receptors. However, not all effects of cannabinoids are ascribable to their interaction with CB1 and CB2 receptors; indeed, macromolecules like other types of receptors, ion channels, transcription factors, enzymes, transporters, and cellular structure have been suggested to mediate the functional effects of cannabinoids. Among the proposed molecular targets of endocannabinoids, potassium channels constitute an intriguing group, because these channels not only are crucial in shaping action potentials and controlling the membrane potential and cell excitability, thereby regulating a wide array of physiological processes, but also serve as potential therapeutic targets for the treatment of cancer and metabolic, neurological and cardiovascular disorders. This review sought to survey evidence pertaining to the CB1 and CB2 receptor-independent actions of endocannabinoids on ion channels, with an emphasis on AEA and potassium channels. To better understand the functional roles as well as potential medicinal uses of cannabinoids in human health and disease, further mechanistic studies to delineate interactions between various types of cannabinoids and ion channels, including members in the potassium channel superfamily, are warranted.
Pannexin 1 (PANX1) channel is a critical ATP-releasing pathway that modulates tumor immunity, progression, and prognosis. However, the roles of PANX1 in different cancers remain unclear. We analyzed the expression of PANX1 in human pan-cancer in the Oncomine and GEPIA2.0 databases. The prognostic value of PANX1 expression was determined using Kaplan-Meier plotter and OncoLnc tools. The correlation between PANX1 and tumor-infiltrating immune cells was investigated using the TIMER 2.0. In addition, the relationship between PANX1 and immunomodulators was explored using TISIDB. Finally, gene set enrichment analysis (GSEA) was performed utilizing LinkedOmics. The results indicated that PANX1 was overexpressed in most cancers compared to normal tissues. The high expression of PANX1 was associated with poor prognosis in multiple tumors, especially in pancreatic adenocarcinoma (PAAD). In addition, PANX1 was correlated with a variety of immunomodulators, such as CD274, IL10, CD276, IL2RA, TAP1, and TAP2. PANX1 expression level was significantly related to infiltration of multiple immune cells in many cancers, including cancer associated fibroblast, macrophage, and neutrophil cells. Further analysis revealed that PANX1 was significantly associated with T cells CD8+ (rho = 0.524, P = 1.94e-13) and Myeloid dendritic cell (rho = 0.564, P = 9.45e-16). GSEA results showed that PANX1 was closely associated with leukocyte cell-cell adhesion, endoplasmic reticulum lumen, ECM-receptor interaction, and Focal adhesion pathways in PAAD. PANX1 expression was higher in pan-cancer samples than in normal tissues. The high expression of PANX1 was associated with poor outcome and immune infiltration in multiple cancers, especially in PAAD.
Stomatin binding and inhibition of ASIC3. A) Schematic representations of STOM and ASIC. (LEFT) Stomatin features a central STOM domain (green) (PDB Code: 4FVF). Depicted flanking the STOM domain are a CARC cholesterolbinding motif on the C-terminal end and an α-helical hairpin inserted into the membrane on the N-terminal end. (RIGHT) Structure of chicken ASIC1a in the desensitized state (PDB Code: 6VTK). Two ASIC monomers are shown in white and one monomer is colored to represent the major ASIC structural domains. N-and C-termini are depicted for one monomer as unstructured strands. B) Hypothesized interaction between STOM and ASIC3 shows a critical binding interaction between ASIC3's C-terminus and the STOM domain, while a second interaction between the STOM hairpin and TM1 inhibits ASIC3 function by locking the channel in the closed or desensitized confirmation, or C) by blocking current flow. All structures shown in pipes and planks format using Chimera1.12.
Binding partner interaction sites on ASICs. A) Schematic representations of ASIC with the N-and C-termini depicted as unstructured strands with the hypothesized binding sites for a number of binding partners shown. B) Aligned sequences of the N-termini of ASIC1a, ASIC2a, and ASIC3 from rat showing the putative NSF binding site in cyan. C) Aligned sequences of the C-termini of ASIC1a, ASIC2a, and ASIC3 showing putative binding sites for a number of proteins. The color of the boxes matches the color of the binding sites in panel A.
Acid-sensing ion channels (ASICs) are a family of proton-gated cation channels that contribute to a diverse array of functions including pain sensation, cell death during ischemia, and more broadly to neurotransmission in the central nervous system. There is an increasing interest in understanding the physiological regulatory mechanisms of this family of channels. ASICs have relatively short N- and C-termini, yet a number of proteins have been shown to interact with these domains both in vitro and in vivo. These proteins can impact ASIC gating, localization, cell-surface expression, and regulation. Like all ion channels, it is important to understand the cellular context under which ASICs function in neurons and other cells. Here we will review what is known about a number of these potentially important regulatory molecules.
Bestrophins are a family of calcium-activated chloride channels (CaCCs) with relevance to human physiology and a myriad of eye diseases termed “bestrophinopathies”. Since the identification of bestrophins as CaCCs nearly two decades ago, extensive studies from electrophysiological and structural biology perspectives have sought to define their key channel features including calcium sensing, gating, inactivation, and anion selectivity. The initial X-ray crystallography studies on the prokaryotic homolog of Best1, Klebsiella pneumoniae (KpBest), and the Best1 homolog from Gallus gallus (chicken Best1, cBest1), laid the foundational groundwork for establishing the architecture of Best1. Recent progress utilizing single-particle cryogenic electron microscopy has further elucidated the molecular mechanism of gating in cBest1 and, separately, the structure of Best2 from Bos taurus (bovine Best2, bBest2). Meanwhile, whole-cell patch clamp, planar lipid bilayer, and other electrophysiologic analyses using these models as well as the human Best1 (hBest1) have provided ample evidence describing the functional properties of the bestrophin channels. This review seeks to consolidate these structural and functional results to paint a broad picture of the underlying mechanisms comprising the bestrophin family’s structure-function relationship.
Hepatocellular carcinoma (HCC) is the most common subtype of liver cancer. Many patients with hepatocellular carcinoma are diagnosed at an advanced stage because the early symptoms are not obvious. For advanced hepatocellular carcinoma, immunotherapy and targeted therapy seem to be a promising direction. Finding a new prognostic marker for hepatocellular carcinoma and exploring its role in the immune microenvironment is of great value. ABCC transporters have previously been associated with drug resistance in hepatocellular tumors, but the exact mechanism remains unclear. Here, we conducted a study on ABCC5 in HCC and found that the expression of ABCC5 was up-regulated in HCC and was associated with poor prognosis. Further exploration revealed that ABCC5 was associated with immune infiltration of hepatocellular carcinoma. Single-cell analysis revealed a potential relationship between ABCC5 and immune cell differentiation. Therefore, it is significant to continue to explore the role of ABCC5 in hepatocellular carcinoma.
Most of Solute carrier family-2 (SLC2) members play a key role of facilitative transporters, and glucose transporter (GLUT) proteins encoded by SLC2s can transport hexoses or polyols. However, the function and mechanism of SLC2s remain unclear in human cancers. Here, we explored the dysregulated expression, prognostic values, epigenetic, genetic alterations, and biomolecular network of SLC2s in human cancers. According to the data from public-omicsrepository, SLC2A4 (GLUT4) was found to be significantly downregulated in most cancers, and higher messenger RNA (mRNA) expression of SLC2A4 significantly associated with better prognosis of breast cancer (BRCA) patients. Moreover, DNA hypermethylation in the promoter of SLC2A4 may affect the regulation of its mRNA expression, and SLC2A4 was strongly correlated with pathways, including the translocation of SLC2A4 to the plasma membrane and PID INSULIN PATHWAY. In conclusion, these results provide insight into SLC2s in human cancers and suggest that SLC2A4 could be an unfavorable prognostic biomarker for the survival of BRCA patients.
Expression levels of SLC16 family in cancerous and adjacent normal tissues. (a)The box plot showed the fluctuation of SLC16 family expression in cancer: Overall, the expression of SLC16A1 was the highest, and the expression of SLC16A12 was the lowest. The SLC16 family expression has a low dispersion in the data set, which is of great research value. (b)The heat map of the expression of the SLC16 family in each cancer compared to normal tissue: red represents upregulated expression, blue represents downregulated expression, and the shade of the color represents the degree of difference. Acute Myeloid Leukemia(LAML), Adrenocortical carcinoma(ACC), Cholangio carcinoma(CHOL), Bladder Urothelial Carcinoma(BLCA), Breast invasive carcinoma(BRCA), Cervical squamous cell carcinoma and endocervical adenocarcinoma(CESC), Colon adenocarcinoma(COAD), Uterine Corpus Endometrial Carcinoma(UCEC), Esophageal carcinoma(ESCA), Glioblastoma multiforme(GBM), Head and Neck squamous cell carcinoma(HNSC), Kidney Chromophobe(KICH), Kidney renal clear cell carcinoma(KIRC), Kidney renal papillary cell carcinoma(KIRP), Lymphoid Neoplasm Diffuse Large B-cell Lymphoma(DLBC), Liver hepatocellular carcinoma(LIHC), Brain Lower Grade Glioma(LGG), Lung adenocarcinoma(LUAD), Lung squamous cell carcinoma(LUSC), Skin Cutaneous Melanoma(SKCM), Mesothelioma(MESO), Uveal Melanoma(UVM), Ovarian serous cystadenocarcinoma(OV), Pancreatic adenocarcinoma(PAAD), Pheochromocytoma and Paraganglioma(PCPG), Prostate adenocarcinoma(PAD), Rectum adenocarcinoma(READ), Sarcoma(SARC), Stomach adenocarcinoma-(STAD), Testicular Germ Cell Tumors(TGCT), Thymoma(THYM), Thyroid carcinoma(THCA), Uterine Carcinosarcoma(USC). (c) Correlation plot based on Spearman Correlation test results to show the correlation of gene expression among the SLC16 family members across all 33 cancer types: Among them, SLC16A4 and SLC16A12 have the strongest correlation. The correlation value was 0.54.
SLC16 family gene expression levels in different cancer types and normal tissue. The red rectangle box represents gene expression levels in tumor tissue and the blue rectangle box represents normal tissue. * P < 0.05, ** P < 0.01, and *** P < 0.001. (a) SLC16A1 is differentially expressed in a variety of cancers, including BRCA, CHOL, COAD, ESCA, GBM, HNSC, KICH, KIRC, LIHC, LUSC, PRAD, STAD, THCA, UCEC. (b)SLC16A2 is differentially expressed in a variety of cancers, including BLCA, BRCA, CHOL, COAD, GBM
Kaplan-Meier survival curves comparison of high and low expression of SLC16 family members in pan-cancer. Only survival diagrams with P < 0.001 were shown. Other survival analysis diagrams with p < 0.05 were included in the supplementary document. (a)SLC16A1 is a poor prognostic biomarker in Brain Lower Grade Glioma(LGG, 524 samples). (b)SLC16A1 is a poor prognostic biomarker in Uterine Corpus Endometrial Carcinoma(UCEC, 544 samples). (c)SLC16A2 is a good prognostic biomarker in Thymoma (THYM, 118 samples). (d)SLC16A3 is a poor prognostic biomarker in Brain Lower Grade Glioma(LGG, 524 samples). (e)SLC16A3 is a poor prognostic biomarker in Liver hepatocellular carcinoma(LIHC, 368 samples). (f)SLC16A3 is a poor prognostic biomarker in Lung adenocarcinoma(LUAD, 513 samples). (g)SLC16A4 is a good prognostic biomarker in Kidney renal clear cell carcinoma(KIRC, 531 samples). (h)SLC16A4 is a poor prognostic biomarker in Brain Lower Grade Glioma(LGG, 524 samples).
Kaplan-Meier survival curves comparison of high and low expression of SLC16 family members in pan-cancer. Only survival diagrams with P < 0.001 were shown. Other survival analysis diagrams with p < 0.05 were included in the supplementary document. (a)SLC16A6 is a poor prognostic biomarker in Uveal Melanoma(UVM, 80 samples). (b)SLC16A8 is a poor prognostic biomarker in Uveal Melanoma(UVM, 80 samples). (c)SLC16A9 is a good prognostic biomarker in Brain Lower Grade Glioma(LGG, 524 samples). (d) SLC16A9 is a good prognostic biomarker in Kidney renal clear cell carcinoma(KIRC, 531 samples). (e)SLC16A13 is a good prognostic biomarker in Adrenocortical carcinoma(ACC, 79 samples). (f) SLC16A12 is a poor prognostic biomarker in Kidney renal clear cell carcinoma(KIRC, 531 samples).
Considering that the survival analysis was influenced by multiple variables of the patient, univariate Cox regression was performed to reduce the influence of other variables. Association of SLC16 family expression with patient overall survival for different cancer types. The forest plots with the hazard ratios and 95% confidence intervals for overall survival for different cancer types to show survival advantage and disadvantage with increased gene expression of the SLC16 family. Univariate Cox proportional hazard regression models were used for the association tests. Hazard ratio <1 represents low risk and hazard ratio >1 represents high risk.
Cancer is one of the serious diseases that endanger human health and bring a heavy burden to world economic development. Although the current targeted therapy and immunotherapy have achieved initial results, the emergence of drug resistance shows that the existing research is far from enough. In recent years, the tumor microenvironment has been found to be an important condition for tumor development and has profound research value. The SLC16 family is a group of monocarboxylic acid transporters involved in cancer metabolism and the formation of the tumor microenvironment. However, there have been no generalized cancer studies in the SLC16 family. In this study, we conducted a pan-cancer analysis of the SLC16 family. The results showed that multiple members of the SLC16 family could be used as prognostic indicators for many tumors, and were associated with immune invasion and tumor stem cells. Therefore, the SLC16 family has extensive exploration value in the future.
Estradiol regulates thyroid function, and chloride channels are involved in the regulation of thyroid function. However, little is known about the role of chloride channels in the regulation of thyroid functions by estrogen. In this study, the effects of estrogen on chloride channel activities in human thyroid Nthy-ori3-1 cells were therefore investigated using the whole cell patch-clamp technique. The results showed that the extracellular application of 17β-estradiol (E2) activated Cl⁻ currents, which reversed at a potential close to Cl⁻ equilibrium potential and showed remarkable outward rectification and an anion permeability of I⁻ > Br⁻ > Cl⁻ > gluconate. The Cl⁻ currents were inhibited by the chloride channel blockers, NPPB and tamoxifen. Quantitative Real-time PCR results demonstrated that ClC-3 expression was highest in ClC family member in Nthy-ori3-1 cells. The down-regulation of ClC-3 expression by ClC-3 siRNA inhibited E2-induced Cl⁻ current. The Cl⁻ current was blocked by the estrogen receptor antagonist, ICI 182780 (fulvestrant). Estrogen receptor alpha (ERα) and not estrogen receptor beta was the protein expressed in Nthy-ori3-1 cells, and the knockdown of ERα expression with ERα siRNA abolished E2-induced Cl⁻ currents. Estradiol can promote the accumulation of ClC-3 in cell membrane. ERα and ClC-3 proteins were partially co-localized in the cell membrane of Nthy-ori3-1 cells after estrogen exposure. The results suggest that estrogen activates chloride channels via ERα in normal human thyroid cells, and ClC-3 proteins play a pivotal role in the activation of E2-induced Cl⁻ current.
Accelerating desensitization of whole-cell nAChR currents by GsMTx-4 in C2C12 myotubes. (a), Sample traces of whole-cell nAChR currents were generated by the perfusion of 5 µM ACh with/without 1 µM GsMTx-4 in C2C12 myotubes. Holding potential = −70 mV, whole-cell mode. The solid black line indicated the application duration of the ACh or ACh/GsMTx-4. (b), AChinduced peak current amplitude before (CTL), during (GsMTx-4) and after (Wash) bath perfusion of 1 µM GsMTx-4 (n = 11). (c), The ratio of the current of the steady state to the peak amplitude (n = 11). D-E, The fast (d) and slow (e) components of the desensitization constant of the whole cell currents described the effect of GsMTx-4 on the rate of nAChR desensitization (n = 11). * p < 0.05 and ***P < 0.001, one-way ANOVA analysis followed by Dunnett's test in B-E.
Effect of GsMTx-4 on the single-channel current decay of endogenous nAChRs in C2C12 myotubes and exogenous nAChRs in HEK293T cells. A, The channel activity of the ACh-induced single-channel decay in C2C12 myotubes without (red, n = 18) or with (blue, n = 19) 1 µM GsMTx-4 in the pipette solution. The curve lines were the fitted results following the function of exponential decay. Right panel: representative traces of 3-min recordings of single channels with magnified 5-s recordings. B, The fitting tau values in (a) under the condition of CTL and 1 µM GsMTx-4. C, The channel activity of ACh-induced single-channel decay in HEK293T cells without toxin (red, n = 19), with 10 nM (green, n = 17), 100 nM (brown, n = 11) or with 1 µM (blue, n = 18) GsMTx-4 in the pipette solution. Cells were transfected with the nAChR subunits α, β, δ and γ. The curve lines were fitted results following the function of exponential decay. Right panel: representative traces of 3-min recordings of single channels in transiently transfected HEK293T cells. D, The fitting tau values in (c) under the condition of CTL and different concentrations of GsMTx-4. Pipette ACh concentration was 0.5 µM with a holding potential at +70 mV, cell-attached mode. The red dotted line indicates the closed state of the single channel, and the green dotted line indicates the open state. **P < 0.01 and ***P < 0.001, two-way ANOVA followed by Bonferroni's test in A and C, Mann-Whitney test in B, and Kruskal-Wallis test in D.
Kinetics of the single channel current of nAChR influenced by GsMTx-4 in HEK293T. A, Detailed ACh-induced single channels in the control and 1 μM GsMTx-4 groups. The red dotted line indicates the closed state of the single channel, and the green dotted line indicates the open state. B, An example of all-point amplitude histogram of the events (upper, control and bottom, GsMTx-4). C, Single-channel current amplitude level (control n = 13 and GsMTx-4 n = 9) from all patches. D, Dwell times of open events were averaged (for control, n = 13 and for GsMTX-4, n = 10). E-F, Open dwell time histograms for the control (e) and GsMTx-4 (f) groups. G-H, Dwell close times of the two components of the events (for control, n = 13 and for GsMTX-4, n = 10). I-J, Closed time histograms for both the control (i) and GsMTx-4 (j) groups. The histograms were fitted (continuous solid line) with an exponential log probability function by automatic comparisons of either single or double components (Clampfit software; Molecular Devices). ** p < 0.01, unpaired t-test in C-D and G-H.
Nicotinic acetylcholine receptors (nAChRs) are members of the “cys-loop” ligand-gated ion channel superfamily that play important roles in both the peripheral and central system. At the neuromuscular junction, the endplate current is induced by ACh binding and nAChR activation, and then, the current declines to a small steady state, even though ACh is still bound to the receptors. The kinetics of nAChRs with high affinity for ACh but no measurable ion conductance is called desensitization. This adopted desensitization of nAChR channel currents might be an important mechanism for protecting cells against uncontrolled excitation. This study aimed to show that Grammostola spatulata toxin (GsMTx4), which was first purified and characterized from the venom of the tarantula Grammostola spatulata (now genus Phixotricus), can facilitate the desensitization of nAChRs in murine C2C12 myotubes. To examine the details, muscle-type nAChRs, which are expressed heterologously in HEK293T cells, were studied. A single channel current was recorded under the cell-attached configuration, and the channel activity (NPo) decayed much faster after the addition of GsMTx-4 to the pipette solution. The channel kinetics were further analyzed, and GsMTx-4 affected the channel activity of nAChRs by prolonging the closing time without affecting channel conductance or opening activity. The interaction between nAChRs embedded in the lipid membrane and toxin inserted into the membrane may contribute to the conformational change in the receptor and thus change the channel activity. This new property of GsMTx-4 may lead to a better understanding of the desensitization of ligand-gated channels and disease therapy.
Metabolic reprogramming is common in various cancers. Targeting metabolism to treat tumors is a hot research topic at present. Among them, changes in glucose metabolism in cancer have been widely studied. The Warburg effect maintains a high metabolic level in the tumor, accompanied by changes in glucose transporters. The transmembrane transport of sugar was previously thought to be mediated by SGLT and GLUT. Recently, the Solute Carrier Family(SLC) 45 family may be the third sugar transporter. But the role and value of the SLC45 family in melanoma, a highly malignant skin tumor, is unclear. Our study found that the four members of the SLC45 family, SLC45A1-SLC45A4, were differentially expressed in melanoma, but only SLC45A2 and SLC45A3 had prognostic guiding values. Further analysis revealed that the co-expression patterns of SLC45A2 and SLC45A3 were enriched in multiple metabolic pathways, suggesting their potential role in melanoma. In addition, SLC45A2 and SLC45A3 are also associated with immune cell infiltration. In conclusion, SLC45A2 and SLC45A3 are good prognostic indicators for melanoma and have guiding value for the treatment of melanoma in the future.
Mathematical models for the action potential (AP) generation of the electrically excitable cells including the heart are involved different mechanisms including the voltage-dependent currents with nonlinear time- and voltage-gating properties. From the shape of the AP waveforms to the duration of the refractory periods or heart rhythms are greatly affected by the functions describing the features or the quantities of these ion channels. In this work, a mathematical measure to analyze the regional contributions of voltage-gated channels is defined by dividing the AP into phases, epochs, and intervals of interest. The contribution of each time-dependent current for the newly defined cardiomyocyte model is successfully calculated and it is found that the contribution of dominant ion channels changes substantially not only for each phase but also for different regions of the cardiac AP. Besides, the defined method can also be applied in all Hodgkin–Huxley types of electrically excitable cell models to be able to understand the underlying dynamics better.
Melanoma is a type of cancer with a relatively poor prognosis. The development of immunotherapy for the treatment of patients with melanoma has drawn considerable attention in recent years. It is of great clinical significance to identify novel promising prognostic biomarkers and to explore their roles in the immune microenvironment. The solute carrier (SLC) superfamily is a group of transporters predominantly expressed on the cell membrane and are involved in substance transport. SLC16A1 is a member of the SLC family, participating in the transport of lactate, pyruvate, amino acids, ketone bodies, etc. The role of SLC16A1 in tumor immunity has been recently elucidated, while its role in melanoma remains unclear. In this study, bioinformatics analysis was performed to explore the role of SLC16A1 in melanoma. The results showed that high SLC16A1 expression was correlated with decreased overall survival in patients with melanoma. The genes co-expressed with SLC16A1 were significantly enriched in metabolic regulation, protein ubiquitination, and substance localization. Moreover, SLC16A1 was correlated with the infiltration of immune cells. In conclusion, SLC16A1 is a robust prognostic biomarker for melanoma and may be used as a novel target in immunotherapy.
Summary of KCNMA1 variants and major clinical presentations.
Number of patients with core KCNMA1-linked channe- lopathy symptoms by mutation type.
Disease-linked KCNMA1 SNPs.
KCNMA1-linked channelopathy is an emerging neurological disorder characterized by heterogeneous and overlapping combinations of movement disorder, seizure, developmental delay, and intellectual disability. KCNMA1 encodes the BK K⁺ channel, which contributes to both excitatory and inhibitory neuronal and muscle activity. Understanding the basis of the disorder is an important area of active investigation; however, the rare prevalence has hampered the development of large patient cohorts necessary to establish genotype-phenotype correlations. In this review, we summarize 37 KCNMA1 alleles from 69 patients currently defining the channelopathy and assess key diagnostic and clinical hallmarks. At present, 3 variants are classified as gain-of-function with respect to BK channel activity, 14 loss-of-function, 15 variants of uncertain significance, and putative benign/VUS. Symptoms associated with these variants were curated from patient-provided information and prior publications to define the spectrum of clinical phenotypes. In this newly expanded cohort, seizures showed no differential distribution between patients harboring GOF and LOF variants, while movement disorders segregated by mutation type. Paroxysmal non-kinesigenic dyskinesia was predominantly observed among patients with GOF alleles of the BK channel, although not exclusively so, while additional movement disorders were observed in patients with LOF variants. Neurodevelopmental and structural brain abnormalities were prevalent in patients with LOF mutations. In contrast to mutations, disease-associated KCNMA1 single nucleotide polymorphisms were not predominantly related to neurological phenotypes but covered a wider set of peripheral physiological functions. Together, this review provides additional evidence exploring the genetic and biochemical basis for KCNMA1-linked channelopathy and summarizes the clinical repository of patient symptoms across multiple types of KCNMA1 gene variants.
VGCCs as voltage sensors. As known from the skeletal muscle, also in neurons VGCCs have been shown to colocalize with ryanodine receptors (RyR) in the endoplasmic reticulum and trigger RyR-mediated Ca 2+ release from intracellular stores. Importantly, the RyR opening, especially of RyR isoform 1, was shown to be independent of the ionic activity of the VGCCs but rather require the conformational change of the voltage-sensing transmembrane helices of the VGCC pore induced by membrane depolarization, a process called voltage-induced calcium release. Additional interaction partners like voltage-gated (Kv) or Ca 2+ -activated (KCa) potassium channel and membranebinding proteins, junctophilins, might complement and stabilize this functional complex.
VGCCs participate in gene regulation. Besides Ca 2+ -dependent signaling cascades activating NFAT, CREB, or DREAM, VGCC β 4 subunits (A, left) and α 1 C-terminal domains (B, right) also act as transcription factors. A) β 4 splice variants interact with proteins of the epigenetic machinery such as HP1s or the B56δ regulatory subunit of protein phosphatases-2A (PP2A) and translocate to the nucleus with a rank order of ᵝ 4b > ᵝ 4a > ᵝ 4e . B) CCAT and ɑ 1 ACT are fragments directly derived from the carboxyl-terminus of the pore-forming α 1 subunit of Ca V 1.2 and Ca V 2.1 channels, respectively. Their expression via an internal ribosomal entry site (IRES) or an unknown exonic promoter is controversially discussed. They have been shown to translocate to the nucleus and regulate gene activity associated with neurodevelopment and synaptic transmission. Modelled after Barbado et al. 2009 32 and Tadmouri et al. 2012 57 .
Voltage-gated calcium channels (VGCCs) represent key regulators of the calcium influx through the plasma membrane of excitable cells, like neurons. Activated by the depolarization of the membrane, the opening of VGCCs induces very transient and local changes in the intracellular calcium concentration, known as calcium nanodomains, that in turn trigger calcium-dependent signaling cascades and the release of chemical neurotransmitters. Based on their central importance as concierges of excitation-secretion coupling and therefore neuronal communication, VGCCs have been studied in multiple aspects of neuronal function and malfunction. However, studies on molecular interaction partners and recent progress in omics technologies have extended the actual concept of these molecules. With this review, we want to illustrate some new perspectives of VGCCs reaching beyond their function as calcium-permeable pores in the plasma membrane. Therefore, we will discuss the relevance of VGCCs as voltage sensors in functional complexes with ryanodine receptors, channel-independent actions of auxiliary VGCC subunits, and provide an insight into how VGCCs even directly participate in gene regulation. Furthermore, we will illustrate how structural changes in the intracellular C-terminus of VGCCs generated by alternative splicing events might not only affect the biophysical channel characteristics but rather determine their molecular environment and downstream signaling pathways.
Glycine insertions within the anchor domain influence Piezo1 channel mechanosensitivity. (a) Representative electrophysiological traces for WT human Piezo1 (hPiezo1) and the P2113 + 2 G, G2163 + 2 G and T2128 + 2 G mutants. Cellattached configuration with current shown in black and pressure trace in red, recorded at +60 mV pipette potential. (c) Quantification of midpoint pressure threshold (P 1/2 ) for WT, P2113 + 2 G and G2163 + 2 G determined by fitting pressure response curves with Boltzmann fit. Data is displayed as mean ± S.E.M. (p -value determined using One-way ANOVA with Sidak's post hoc test). (d) Normalized steady state current of the G2163 + 2 G mutant showing a significantly higher value than WT indicative of abrogated inactivation. Normalized steady state current was measured for WT and G2163 + 2 G at the first pressure that induced currents at or above the P 1/2 to normalize for pressure application. Data is displayed as a maximum to minimum box and whisker plot with all data points shown (p -value determined using T-test) .
Glycine insertion (+2 G) at position T2128 results in a trafficking defect. (a) Peak currents elicited per cell-attached patch comparing WT hPiezo1 to the T2128 + 2 G mutant at +60 mV pipette potential (p -value determined using T-test. (b) Representative western blot showing WT, P2113 + 2 G, G2163 + 2 G and T2128 + 2 G (FG -Fully glycosylated), (n = 5) .
Mutations at position F2114 in human Piezo1 influence channel sensitivity to mechanical force. (a) Side and top view of Piezo1 structure showing the inner helix (IH) outer helix (OH) and the position of F2114 (purple). Note that the F2114 residue is in very close proximity to the IH which lines the pore (denoted -P). (b) Representative electrophysiological traces for WT, F2114G, F2114A, F2114C, F2114T and F2114Y. Cell-attached configuration with current shown in black and pressure trace in red, recorded at +60 mV pipette potential. (c) Comparison of peak current elicited per patch for WT hPiezo1 and F2114 mutations (p -value determined using One-way ANOVA with Sidak's multiple comparison test, only significant comparisons with WT illustrated). (d) Representative blot showing Piezo1 protein levels for transiently transfected mutants F2114G, F2114A, F2114C, F2114T and F2114Y after 72 h expression (n = 4). Note the lower level of the upper band with F2114G (FG -fully glycosylated, CG -core glycosylated). (e) Quantification of midpoint pressure threshold (P 1/2 ) in mmHg for WT, F2114G, F2114A, F2114C, F2114T and F2114Y determined by fitting pressure response curves with Boltzmann fit. (ns -not significant, * -significant with p = 0.0232 F2114 and 0.0136, determined using One-way ANOVA with Sidak's multiple comparison test). Data is displayed as mean ± S.E.M.
Correlation of Piezo1 channel mechanosensitivity with amino acid volume and hydrophobicity at amino acid position 2114. (a) Midpoint pressure (P 1/2 ) plotted against amino acid volume. (b) Midpoint pressure (P 1/2 ) plotted against amino acid hydrophobicity using three different scales. In all cases solid lines represent linear regression.
The mechanosensitive channel Piezo1 is a crucial membrane mechanosensor ubiquitously expressed in mammalian cell types. Critical to its function in mechanosensory transduction is its ability to change conformation in response to applied mechanical force. Here, we interrogate the role of the anchor domain in the mechanically induced gating of human Piezo1 channels. Using the insertion of glycine residues at each corner of the triangular-shaped anchor domain to decouple this domain we provide evidence that the anchor is important in Piezo1 mechano-gating. Insertion of two extra glycine residues between the anchor and the outer helix of human Piezo1 causes abrogated inactivation and reduced mechanosensitivity. Whereas inserting two glycine residues at the apex of the anchor domain at the conserved amino acid P2113 causes the channel to be more sensitive to membrane forces. Correlation of stretch sensitivity with the volume of the neighboring amino acid, natively a phenylalanine (F2114), suggests this is caused by removal of steric hindrance on the inner pore-lining helix. Smaller volume amino acids at this residue increase sensitivity whereas larger volume reduces mechanosensitivity. The combined data show that the anchor domain is a critical region for Piezo1-mediated force transduction.
Biophysical and pharmacological properties of mitoBK Ca channels.
The mitochondrial BKCa channel (mitoBKCa) is a splice variant of plasma membrane BKCa (Maxi-K, BKCa, Slo1, KCa1.1). While a high-resolution structure of mitoBKCa is not available yet, functional and structural studies of the plasma membrane BKCa have provided important clues on the gating of the channel by voltage and Ca²⁺, as well as the interaction with auxiliary subunits. To date, we know that the control of expression of mitoBKCa, targeting and voltage-sensitivity strongly depends on its association with its regulatory β1-subunit, which overall participate in the control of mitochondrial Ca²⁺-overload in cardiac myocytes. Moreover, novel regulatory mechanisms of mitoBKCa such as β-subunits and amyloid-β have recently been proposed. However, major basic questions including how the regulatory BKCa-β1-subunit reaches mitochondria and the mechanism through which amyloid-β impairs mitoBKCa channel function remain to be addressed.
HCN2 protein expression and HCN2 SUMOylation are unaltered in the L4 DRG 3 days post CFA. (a) HCN2 mean pixel intensities do not change 3 days post-CFA. Average mean pixel intensity ± SEM is shown for three size classes of DRG neurons (small: ≤ 30 µm; medium: 30-40 µm; large: > 40 µm). Each dot represents the mean for one animal. Note that data for left and right DRG from each control were combined, because paired t-tests indicated left and right DRG showed no significant differences. The total number of cells examined for all animals within the treatment group is indicated in the bar. Small cells: one-way ANOVA F (2,12) = 0.090; p = 0.915; medium cells: Kruskal-Wallis (2,14) = 0.438; p = 0.819; large cells: one-way ANOVA F(2,14) = 0.330; p = 0.725. (b) The percent of HCN2 expressing cells does not change 3 days post-CFA. Plot of percent HCN2 positive cells for each size class (frequency = # HCN2 positive cells for that size class ÷ total cells number for all classes). Bars are mean ± SEM. Small cells: one-way ANOVA F(2,12) = 0.581; p = 0.574; medium cells: Kruskal-Wallis (2,14) = 1.358; p = 0.531; large cells: one-way ANOVA F (2,14) = 0.176; p = 0.840. (c) The number of SUMOylated HCN2 channels is unaltered in L4 DRG neurons. The number of puncta/µm 2 for HCN2 SUMO1 (light bars) and SUMO2/3 (dark bars) conjugation is shown for three size classes of DRG neurons (small: ≤ 30 µm; medium: 30-40 µm; large: > 40 µm). SUMO1; small: 0.473 ± 0.068 vs 0.412 ± 0.031, p = 0.307, paired t-test; medium: 0.465 ± 0.076 vs 0.393 ± 0.041, p = 0.418, paired t-test; large: 0.456 ± 0.066 vs 0.466 ± 0.040, p = 0.847, paired t-test; SUMO2/3; small: 0.479 ± 0.059 vs 0.438 ± 0.047, p = 0.121, paired t-test; medium: 0.431 ± 0.067 vs 0.361 ± 0.043, p = 0.236, paired t-test; large: 0.446 ± 0.069 vs 0.417 ± 0.047, p = 0.562, paired t-test. Inset: compares the means for contralateral and ipsilateral DRG for each animal. (d) SUMOylated HCN2 Puncta Intensities are unaltered in L4 DRG neurons. Plot of average puncta intensity ± SEM for each size class. SUMO1; small: 56.16 ± 4.766 vs 64.04 ± 8.799, p = 0.382, paired t-test; medium: 54.92 ± 4.379 vs 63.08 ± 9.142, p = 0.400, paired t-test; large: 56.32 ± 4.917 vs 65.79 ± 11.18, p = 0.423, paired t-test; SUMO2/3; small: 59.62 ± 6.125 vs 61.62 ± 8.081, p = 0.836, paired t-test; medium: 59.44 ± 6.444 vs 64.02 ± 8.447, p = 0.609, paired t-test; large: 61.18 ± 6.817 vs 64.59 ± 7.984, p = 0.691, paired t-test.
HCN2 protein expression and HCN2 SUMOylation are enhanced in the L6 DRG 1 day post-CFA. (a) HCN2 mean pixel intensity is elevated in small diameter neurons. Average mean pixel intensity ± SEM is shown for three size classes of DRG neurons (small: ≤ 30 µm; medium: 30-40 µm; large: > 40 µm). Each dot represents the mean for one animal. Note that data for left and right DRG from each control were combined, because paired t-tests indicated left and right DRG showed no significant differences. The total number of cells examined for all animals within the treatment group is indicated in the bar. Asterisks indicate significance, *p < 0.05. Small cells: one-way ANOVA with Tukey's post-hoc F(2,15) = 7.422; p = 0.0060; medium cells: one-way ANOVA F (2,15) = 3.542; p = 0.055; large cells: one-way ANOVA F(2,15) = 1.338; p = 0.292. (b) The percent of HCN2 expressing cells is unaltered 1 day post-CFA. Plot of percent HCN2 positive cells for each size class (frequency = # HCN2 positive cells for that size class ÷ total cells number for all classes). Bars indicate mean ± SEM. Small cells: one-way ANOVA F(2,15) = 1.980; p = 0.173; medium cells: one-way ANOVA F(2,15) = 0.147; p = 0.865; large cells: one-way ANOVA F(2,15) = 0.365; p = 0.700. (c) The number of SUMOylated HCN2 channels increases in medium and large diameter neurons. The number of puncta/µm 2 for HCN2 SUMO1 (light bars) and SUMO2/3 (dark bars) conjugation is shown for three size classes of DRG neurons (small: ≤ 30 µm; medium: 30-40 µm; large: > 40 µm). Bars indicate the mean ± SEM. Asterisks indicate significance, *p < 0.05. SUMO1; small: 0.408 ± 0.068 vs 0.429 ± 0.083, p = 0.574, paired t-test; medium: 0.438 ± 0.068 vs 0.365 ± 0.064, p = 0.031, Wilcoxon matched-pairs; large: 0.424 ± 0.046 vs 0.426 ± 0.049, p = 0.961, paired t-test; SUMO2/3; small: 0.407 ± 0.069 vs 0.418 ± 0.057, p = 0.752, paired t-test; medium: 0.419 ± 0.060 vs 0.372 ± 0.042, p = 0.189, paired t-test; large: 0.488 ± 0.059 vs 0.388 ± 0.042, p = 0.018, paired-test. Inset: compares the means for contralateral and ipsilateral DRG for each animal. (d) SUMOylated HCN2 Puncta Intensities are unaltered 1 day post-CFA. Plot of average puncta intensity ± SEM for each size class. SUMO1; small: 59.42 ± 8.867 vs 51.48 ± 5.557, p = 0.137, paired t-test; medium: 59.92 ± 9.085 vs 52.20 ± 5.315, p = 0.189, paired t-test; large: 59.39 ± 8.740 vs 55.49 ± 9.037, p = 0.316, paired t-test; SUMO2/3; small: 61.16 ± 8.501 vs 60.61 ± 8.770, p = 0.916, paired t-test; medium: 60.58 ± 8.002 vs 60.13 ± 9.115, p = 0.936, paired t-test; large: 54.74 ± 6.259 vs 51.96 ± 4.790, p = 0.655, paired t-test.
HCN2 SUMOylation but not protein expression is altered in the L6 DRG 3 days post-CFA. (a) HCN2 mean pixel intensities do not change 3 days post-CFA. Average mean pixel intensity ± SEM is shown for three size classes of DRG neurons (small: ≤ 30 µm; medium: 30-40 µm; large: > 40 µm). Each dot represents the mean for one animal. Note that data for left and right DRG from each control were combined, because paired t-tests indicated left and right DRG showed no significant differences. The total number of cells examined for all animals within the treatment group is indicated in the bar. Small cells: Kruskal-Wallis (2,13) = 2.842; p = 0.252; medium cells: Kruskal-Wallis (2,13) = 1.309; p = 0.543; large cells: Kruskal-Wallis (2,12) = 0.061; p = 0.977. (b) The percent of HCN2 expressing cells does not change 3 days post-CFA. Plot of percent HCN2 positive cells for each size class (frequency = # HCN2 positive cells for that size class ÷ total cells number for all classes). Bars indicate mean ± SEM. Small cells: one-way ANOVA F (2,13) = 0.206; p = 0.817; medium cells: one-way ANOVA (2,13) = 0.043; p = 0.958; large cells: one-way ANOVA F(2,12) = 0.932; p = 0.420. (c) The number of HCN2 SUMOylated channels is unaltered 3 days post-CFA. The number of puncta/µm 2 for HCN2 SUMO1 (light bars) and SUMO2/3 (dark bars) conjugation is shown for three size classes of DRG neurons (small: ≤ 30 µm; medium: 30-40 µm; large: > 40 µm). SUMO1; small: 0.473 ± 0.077 vs 0.418 ± 0.057, p = 0.211, paired t-test; medium: 0.498 ± 0.118 vs 0.413 ± 0.06, p = 0.219, paired t-test; large: 0.466 ± 0.127 vs 0.427 ± 0.071, p = 0.593, paired t-test; SUMO2/3; small: 0.423 ± 0.099 vs 0.389 ± 0.046, p = 0.678, paired t-test; medium: 0.424 ± 0.104 vs 0.392 ± 0.073, p = 0.563, Wilcoxon matched-pairs, large: 0.475 ± 0.112 vs 0.417 ± 0.059, p = 0.563, Wilcoxon matched-pairs. Inset: compares the means for contralateral and ipsilateral DRG for each animal. (d) SUMOylated HCN2 Puncta Intensities are increased in small and medium cells. Plot of average puncta intensity ± SEM for each size class. SUMO1; small: 71.29 ± 8.984 vs 65.37 ± 6.805, p = 0.219, Wilcoxon matched-pairs; medium: 73.03 ± 8.633 vs 64.59 ± 6.927, p = 0.094, Wilcoxon matched-pairs; large: 72.02 ± 9.835 vs 66.21 ± 6.770, p = 0.313, Wilcoxon matched-pairs; SUMO2/ 3; small: 75.83 ± 9.743 vs 63.63 ± 7.899, p = 0.031, Wilcoxon matched-pairs; medium: 73.25 ± 9.620 vs 64.71 ± 8.353, p = 0.046, paired t-test; large cells: 71.93 ± 6.724 vs 65.46 ± 8.374, p = 0.148, paired t-test.
Nociceptor sensitization following nerve injury or inflammation leads to chronic pain. An increase in the nociceptor hyperpolarization-activated current, Ih, is observed in many models of pathological pain. Pharmacological blockade of Ih prevents the mechanical and thermal hypersensitivity that occurs during pathological pain. Alterations in the Hyperpolarization-activated Cyclic Nucleotide-gated ion channel 2 (HCN2) mediate Ih-dependent thermal and mechanical hyperalgesia. Limited knowledge exists regarding the nature of these changes during chronic inflammatory pain. Modifications in HCN2 expression and post-translational SUMOylation have been observed in the Complete Freund’s Adjuvant (CFA) model of chronic inflammatory pain. Intra-plantar injection of CFA into the rat hindpaw induces unilateral hyperalgesia that is sustained for up to 14 days following injection. The hindpaw is innervated by primary afferents in lumbar DRG, L4-6. Adjustments in HCN2 expression and SUMOylation have been well-documented for L5 DRG during the first 7 days of CFA-induced inflammation. Here, we examine bilateral L4 and L6 DRG at day 1 and day 3 post-CFA. Using L4 and L6 DRG cryosections, HCN2 expression and SUMOylation were measured with immunohistochemistry and proximity ligation assays, respectively. Our findings indicate that intra-plantar injection of CFA elicited a bilateral increase in HCN2 expression in L4 and L6 DRG at day 1, but not day 3, and enhanced HCN2 SUMOylation in ipsilateral L6 DRG at day 1 and day 3. Changes in HCN2 expression and SUMOylation were transient over this time course. Our study suggests that HCN2 is regulated by multiple mechanisms during CFA-induced inflammation. © 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
Location of the disease-associated TRPM3 mutant residues. A: Top panel: Sequence alignment of the outer part of S6. The P1090/1092 residue in TRPM3 is highlighted blue. P1090 is the location of this residue in splice variant hTRPM3 1325 used by both Zhao et al. [37] and Van Hoeymissen et al. [36] for functional studies, P1092 is the same reside in the hTRPM3α2 splice variant also used for functional studies by Zhao et al. [37]; they correspond to P937 in Dyment et al. [35]. Bottom panel: Sequence alignment of the S4-S5 loop, the V990/992 residue in TRPM3 is labeled red, V990 and V992 are the locations of the same residue in hTRPM3 1325 and hTRPM3α2, and they both correspond to V837 in Dyment et al. [35].Yellow highlights indicate residues in contact with the agonists icilin and/or WS12 in the TRPM8 structures (6nr3, 6nr4, 6nr2), the residue highlighted green is in contact with PI[4,5]P 2 in TRPM8. B: the location of residues equivalent to V990/992 and P1090/1092 on the structure of TRPM4 (6bwi); one subunit is hidden for visibility. The short α-helical segment equivalent to the Gβγ binding site in TRPM3 is also shown. Adapted from Zhao et al. 2020 [37].
The effect of disease-associated TRPM3 mutations on agonist sensitivity and heat sensitivity. Adapted from Zhao et al. 2020 [37]. A-C: Representative two electrode voltage clamp experiments in Xenopus oocytes expressing the hTRPM3 1325 splice variant (A) and its mutants V990M (B) and P1090Q (C). Horizontal lines show the applications of different concentrations of PregS (μM). D: Hill fits of the concentration dependence of the effect of PregS. E-G: Representative whole cell patch clamp measurements on the human TRPM3α2 (A) or its mutants V992M (B) and P1092Q (C) expressed in HEK293 cells. Note that the numbering of the residues differs by 2 because of the different splice variant used compared to (A-C). The applications of 100 μM PregS are indicated by the horizontal lines, the temperature curves on the top panels. D: Summary of the slopes of the current increases between 23°C and 33°C. See Zhao et al. 2020 [37] for more details.
Human diseases caused by mutations in TRP channels.
Transient Receptor Potential Melastatin 3 (TRPM3) is a Ca²⁺ permeable nonselective cation channel, activated by heat and chemical agonists, such as the endogenous neuro-steroid Pregnenolone Sulfate (PregS) and the chemical compound CIM0216. TRPM3 is expressed in peripheral sensory neurons of the dorsal root ganglia (DRG), and its role in noxious heat sensation in mice is well established. TRPM3 is also expressed in a number of other tissues, including the brain, but its role there has been largely unexplored. Recent reports showed that two mutations in TRPM3 are associated with a developmental and epileptic encephalopathy, pointing to an important role of TRPM3 in the human brain. Subsequent reports found that the two disease-associated mutations increased basal channel activity, and sensitivity of the channel to activation by heat and chemical agonists. This review will discuss these mutations in the context of human diseases caused by mutations in other TRP channels, and in the context of the biophysical properties and physiological functions of TRPM3.
Single systemic ALA reduces mechanical hyperalgesia after incision. A. A time course of experimental protocol for a single application of ALA. B. ALA applied 2 h after surgery on postoperative day (POD) 0 at both doses of 60 mg/kg and 120 mg/kg i.p. induced significant antihyperalgesic effect in a dose-dependent manner as compared to the vehicle group (n = 5-8 rats, two-way RM-ANOVA, interaction: F(4,32) = 4.12; p = 0.0084; treatment: F(2,16) = 38.25; p < 0.001). C. ALA applied 24 h after surgery on POD 1 in both doses of 60 mg/kg and 120 mg/kg i.p. induced significant antihyperalgesic effect in a dose-dependent manner as compared to the vehicle group (n = 5-8 rats, two-way RM-ANOVA, interaction: F(4,34) = 1.82; p = 0.15; treatment: F(2,17) = 31.17; p < 0.001). Data are presented as means ± SEM. *p < 0.05; **p < 0.01; ***p < 0.001.
Systemic ALA in a dose of 120 mg/kg i.p does not affect motor performance in rats. A. A time course of experimental protocol of application of ALA and rotarod assessment. B. ALA applied i.p. at a dose of 120 mg/kg did not affect the time animals spent on rotarod 30 minutes after injections, as compared to the preinjection baseline conditions (n = 4 rats, p = 0.391, paired t-test). Data are presented as means ± SEM.
Repeated systemic ALA in a dose of 60 mg/kg had mild effect on mechanical hyperalgesia after incision. A. A time course of experimental protocol for a repeated application of ALA. B. ALA applied i.p. in a dose of 60 mg/kg, as three consecutive doses before, and three consecutive doses after surgery, exerted small but significant antihyperalgesic effect in the test of mechanical sensitivity on POD 5, as compared to the vehicle group (n = 5-8 rats, two-way RM-ANOVA, interaction: F(5,55) = 4.01; p = 0.036; treatment: F (1,11) = 5.573; p = 0.048). Data are presented as means ± SEM. *p < 0.05; **p < 0.01; ***p < 0.001.
Our previous studies have implicated CaV3.2 isoform of T-type Ca2+ channels (T-channels) in the development of postsurgical pain. We have also previously established that different T-channel antagonists can alleviate in vivo postsurgical pain. Here we investigated the analgesic potential of another T-channel blocker and endogenous antioxidant molecule, α-lipoic acid (ALA), in a postsurgical pain model in rats. Our in vivo results suggest that single and repetitive intraperitoneal injections of ALA after surgery or preemptively, significantly reduced evoked mechanical hyperalgesia following surgical paw incision. Furthermore, repeated preemptive systemic injections of ALA effectively alleviated spontaneous postsurgical pain as determined by dynamic weight-bearing testing. We expect that our preclinical study may lead to further investigation of analgesic properties and mechanisms of analgesic action of ALA in patients undergoing surgery.
Procedure for the selection of the potential biomarker in ccRCC.
Kaplan-Meier survival curve of ABCG1 mRNA expression in ccRCC patients. Survival curves suggested that patients with decreased ABCG1 mRNA level significantly correlated with poorer OS (p = 0.0067).
T-test and ROC analysis of ABC transporter family members based on the TCGA-ccRCC dataset.
Chi-square test of clinicopathologic parameters and ABCG1 mRNA expression in the TCGA-ccRCC cohort.
Univariate and multivariate Cox regression analysis of clinical pathologic features according to the TCGA-ccRCC dataset.
As the most common histologic subtype of renal cancer, clear cell renal cell carcinoma (ccRCC) poses a serious threat to public health. However, there are no specific molecular-targeted drugs for ccRCC at present. Human ATP-binding cassette (ABC) transporter family plays an important role in homeostasis maintenance. This study aimed to evaluate the potential diagnostic value of ABC genes in ccRCC. A total of 952 samples of ccRCC patients (707) and controls (245) from three different datasets were included for analysis. Receiver operating characteristic analysis and t-test were used to analyze the differential expression of ABC genes in ccRCC patients and control samples at mRNA level during screening and validations. The Cancer Genome Atlas (TCGA-ccRCC) dataset was utilized to investigate the correlation between ABC genes expression and prognostic value in ccRCC. We then investigated the interactions between ABCG1 and proteins in the Comparative Toxicogenomics Database (CTD). Finally, we found that ATP-binding cassette transporter G member 1 (ABCG1) was over-expressed in ccRCC patients compared with healthy samples at mRNA level. Cox regression analysis and Kaplan–Meier analysis showed that ccRCC patients with high ABCG1 expression had better overall survival (OS) than those patients with low expression (hazard ratio (HR) = 0.662, p = 0.007). This study demonstrated that ABCG1 is a potential diagnostic and prognostic biomarker in ccRCC and discussed the molecular mechanisms underlying the relationship between ccRCC and ABCG1, which might provide guidance for better management and treatment of ccRCC in the future.
Vitamin D is known to elicit many biological effects in diverse tissue types and is thought to act almost exclusively upon its canonical receptor within the nucleus, leading to gene transcriptional changes and the subsequent cellular response. However, not all the observed effects of vitamin D can be attributed to this sole mechanism, and other cellular targets likely exist but remain to be identified. Our recent discovery that vitamin D is a partial agonist of the Transient Receptor Potential Vanilloid family 1 (TRPV1) channel may provide new insights as to how this important vitamin exerts its biological effects either independently or in addition to the nuclear vitamin D receptor. In this review, we discuss the literature surrounding this apparent discrepancy in vitamin D signaling and compare vitamin D with known TRPV1 ligands with respect to their binding to TRPV1. Furthermore, we provide evidence supporting the notion that this novel vitamin D/TRPV1 axis may explain some of the beneficial actions of this vitamin in disease states where TRPV1 expression and vitamin D deficiency are known to overlap. Finally, we discuss whether vitamin D may also act on other members of the TRP family of ion channels.
Conceptual illustration of the cellular mechanotransduction mechanism mediated by ion channels in articular chondrocytes.
Articular chondrocytes in response to hind limb unloading or simulated microgravity.
Articular cartilage consists of an extracellular matrix including many proteins as well as embedded chondrocytes. Articular cartilage formation and function are influenced by mechanical forces. Hind limb unloading or simulated microgravity causes articular cartilage loss, suggesting the importance of the healthy mechanical environment in articular cartilage homeostasis and implying a significant role of appropriate mechanical stimulation in articular cartilage degeneration. Mechanosensitive ion channels participate in regulating the metabolism of articular chondrocytes, including matrix protein production and extracellular matrix synthesis. Mechanical stimuli, including fluid shear stress, stretch, compression and cell swelling and decreased mechanical conditions (such as simulated microgravity) can alter the membrane potential and regulate the metabolism of articular chondrocytes via transmembrane ion channel-induced ionic fluxes. This process includes Ca²⁺ influx and the resulting mobilization of Ca²⁺ that is due to massive released Ca²⁺ from stores, intracellular cation efflux and extracellular cation influx. This review brings together published information on mechanosensitive ion channels, such as stretch-activated channels (SACs), voltage-gated Ca²⁺ channels (VGCCs), large conductance Ca²⁺-activated K⁺ channels (BKCa channels), Ca²⁺-activated K⁺ channels (SKCa channels), voltage-activated H⁺ channels (VAHCs), acid sensing ion channels (ASICs), transient receptor potential (TRP) family channels, and piezo1/2 channels. Data based on epithelial sodium channels (ENaCs), purinergic receptors and N-methyl-d-aspartate (NMDA) receptors are also included. These channels mediate mechanoelectrical physiological processes essential for converting physical force signals into biological signals. The primary channel-mediated effects and signaling pathways regulated by these mechanosensitive ion channels can influence the progression of osteoarthritis during the mechanosensory and mechanoadaptive process of articular chondrocytes.
Journal metrics
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3.493 (2021)
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3.9 (2021)
Top-cited authors
Roger J Thompson
  • The University of Calgary
Jörg Striessnig
  • University of Innsbruck
Silvia Penuela
  • The University of Western Ontario
Gerald W Zamponi
  • The University of Calgary
Davis Spray
  • Albert Einstein College of Medicine