Colin G Nichols

Washington University in St. Louis, San Luis, Missouri, United States

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Publications (239)1433.15 Total impact

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    ABSTRACT: Diabetes is characterized by "glucotoxic" loss of pancreatic β cell function and insulin content, but underlying mechanisms remain unclear. A mouse model of insulin-secretory deficiency induced by β cell inexcitability (KATP gain of function) demonstrates development of diabetes and reiterates the features of human neonatal diabetes. In the diabetic state, β cells lose their mature identity and dedifferentiate to neurogenin3-positive and insulin-negative cells. Lineage-tracing experiments show that dedifferentiated cells can subsequently redifferentiate to mature neurogenin3-negative, insulin-positive β cells after lowering of blood glucose by insulin therapy. We demonstrate here that β cell dedifferentiation, rather than apoptosis, is the main mechanism of loss of insulin-positive cells, and redifferentiation accounts for restoration of insulin content and antidiabetic drug responsivity in these animals. These results may help explain gradual decrease in β cell mass in long-standing diabetes and recovery of β cell function and drug responsivity in type 2 diabetic patients following insulin therapy, and they suggest an approach to rescuing "exhausted" β cells in diabetes.
    Cell metabolism 04/2014; · 17.35 Impact Factor
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    ABSTRACT: ATP-sensitive potassium (KATP ) channels, composed of inward-rectifying potassium channel subunits (Kir6.1 and Kir6.2, encoded by KCNJ8 and KCNJ11, respectively) and regulatory sulfonylurea receptor (SUR1 and SUR2, encoded by ABCC8 and ABCC9, respectively), couple metabolism to excitability in multiple tissues. Mutations in ABCC9 cause Cantú syndrome, a distinct multi-organ disease, potentially via enhanced KATP channel activity. We screened KCNJ8 in an ABCC9 mutation-negative patient who also exhibited clinical hallmarks of Cantú syndrome (hypertrichosis, macrosomia, macrocephaly, coarse facial appearance, cardiomegaly, and skeletal abnormalities). We identified a de novo missense mutation encoding Kir6.1[p.Cys176Ser] in the patient. Kir6.1[p.Cys176Ser] channels exhibited markedly higher activity than wild-type channels, as a result of reduced ATP sensitivity, whether co-expressed with SUR1 or SUR2A subunits. Our results identify a novel causal gene in Cantú syndrome, but also demonstrate that the cardinal features of the disease result from gain of KATP channel function, not from Kir6-independent SUR2 function. This article is protected by copyright. All rights reserved.
    Human Mutation 04/2014; · 5.21 Impact Factor
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    ABSTRACT: The copy number of membrane proteins at the cell surface is tightly regulated. Many ion channels and receptors present retrieval motifs to COPI and are retained in the early secretory pathway. In some cases the COPI interaction is prevented by binding of 14-3-3 proteins. However, the functional significance of this COPI/14-3-3 antagonism in terminally differentiated cells is unknown. Here we show that ATP-sensitive potassium (KATP) channels composed of Kir6.2 and SUR1 subunits are stalled in the Golgi complex of ventricular, but not atrial cardiomyocytes. Upon sustained β-adrenergic stimulation, which leads to activation of protein-kinase A (PKA), SUR1-containing channels reach the plasma membrane of ventricular cells. We show that PKA-dependent phosphorylation of the C-terminus of Kir6.2 decreases binding of COPI and thereby silences the Arg-based retrieval signal. Thus, activation of the sympathetic nervous system releases this KATP channel population from storage in the Golgi and hence may facilitate the adaptive response to metabolic challenges.
    Journal of Cell Science 02/2014; · 5.88 Impact Factor
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    ABSTRACT: Congenital hyperinsulinism (CHI) requires rapid diagnosis and treatment to avoid irreversible neurological sequelae due to hypoglycemia. Etiological diagnosis is instrumental in directing the appropriate therapy. Current diagnostic algorithms provide a complete set of diagnostic tools including 1) biochemical assays, 2) genetic facility and 3) state-of-the-art imaging. They consider the response to a therapeutic diazoxide-trial an early, crucial step before proceeding (or not) to specific genetic testing and eventually imaging, aimed at distinguishing diffuse versus focal CHI. However, interpretation of the diazoxide-test is not trivial and can vary between research groups, which may lead to inappropriate decisions. Objective of this report is proposing a new algorithm in which early genetic screening, rather than diazoxide trial, dictates subsequent clinical decisions. Two CHI patients weaned from parenteral glucose infusion and glucagon after starting diazoxide. No hypoglycemia was registered during a 72-h continuous glucose monitoring (CGMS) or hypoglycemic episodes were present for no longer than 3% of 72-h. Normoglycemia was obtained by low-medium dose diazoxide combined with frequent carbohydrate feeds for several years. We identified monoallelic, paternally inherited mutations in KATP -channel genes, and (18) F-DOPA PET-CT revealed a focal lesion that was surgically resected, resulting in complete remission of hypoglycemia. Although rare, some patients with focal lesions may be responsive to diazoxide. As a consequence, we propose an algorithm that is not based on a "formal" diazoxide response but on genetic testing, in which patients carrying paternally inherited ABCC8 or KCNJ11 mutations should always be subjected to (18) F-DOPA PET-CT. This article is protected by copyright. All rights reserved.
    Clinical Endocrinology 01/2014; · 3.40 Impact Factor
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    ABSTRACT: Background Adenosine triphosphate - sensitive (KATP) potassium channel opener diazoxide (DZX) maintains myocyte volume and contractility during stress via an unknown mechanism when administered at the onset of stress. This study was performed to investigate the cardioprotective potential of DZX when added after the onset of the stresses of hyperkalemic cardioplegia, metabolic inhibition, and hypo osmotic stress. Study Design Isolated mouse ventricular and human atrial myocytes were exposed to control Tyrode’s solution (TYR) for 10-20 min, test solution for 30 min (hypothermic hyperkalemic cardioplegia (CPG), CPG + 100uM diazoxide (CPG+DZX), metabolic inhibition (MI), MI+DZX, mild hypo osmotic stress (0.9T), or 0.9T + DZX) with DZX added after 10 or 20 min stress, followed by 20 min re-exposure to TYR (+/- DZX). Myocyte volume (human + mouse) and contractility (mouse) were compared. Results Mouse and human myocytes demonstrated significant swelling during exposure to CPG, MI, and hypo osmotic stress that was not prevented by DZX when administered either at 10 or 20 min after the onset of stress. Contractility following the stress of CPG in mouse myocytes significantly declined when DZX was administered 20 min after the onset of stress (p<0.05 vs. TYR). Contractility following hypo osmotic stress in mouse myocytes was not altered by the addition of DZX. Conclusions To maintain myocyte volume homeostasis and contractility during stress (hyperkalemic cardioplegia, metabolic inhibition, and hypo osmotic stress), KATP channel opener diazoxide requires administration at the onset of stress in this isolated myocyte model. These data have potential implications for any future clinical application of diazoxide.
    Journal of the American College of Surgeons 01/2014; · 4.50 Impact Factor
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    ABSTRACT: Inwardly rectifying potassium (Kir) channels regulate multiple tissues. All Kir channels require interaction of phosphatidyl-4,5-bisphosphate (PIP2) at a crystallographically identified binding site, but an additional nonspecific secondary anionic phospholipid (PL(-)) is required to generate high PIP2 sensitivity of Kir2 channel gating. The PL(-)-binding site and mechanism are yet to be elucidated. Here we report docking simulations that identify a putative PL(-)-binding site, adjacent to the PIP2-binding site, generated by two lysine residues from neighbouring subunits. When either lysine is mutated to cysteine (K64C and K219C), channel activity is significantly decreased in cells and in reconstituted liposomes. Directly tethering K64C to the membrane by modification with decyl-MTS generates high PIP2 sensitivity in liposomes, even in the complete absence of PL(-)s. The results provide a coherent molecular mechanism whereby PL(-) interaction with a discrete binding site results in a conformational change that stabilizes the high-affinity PIP2 activatory site.
    Nature Communications 11/2013; 4:2786. · 10.02 Impact Factor
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    ABSTRACT: KirBac channels are prokaryotic homologs of mammalian inwardly rectifying channels (Kir) and recent structures of KirBac3.1 have provided important insights into the structural basis of gating in Kir channels. In this study we demonstrate that KirBac3.1 channel activity is strongly pH-dependent, and used X-ray crystallography to determine the structural changes that arise from an activatory mutation (S205L) located in the cytoplasmic domain (CTD). This mutation stabilizes a novel energetically favorable open conformation where changes at the intersubunit interface in the CTD also alter the electrostatic potential of the inner cytoplasmic cavity. These results provide a structural explanation for the activatory effect of this mutation and provide a greater insight into the role of the CTD in Kir channel gating.
    Journal of Biological Chemistry 11/2013; · 4.65 Impact Factor
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    ABSTRACT: Cardiac myocytes demonstrate significant swelling and associated reduced contractility in response to stress that is prevented by the ATP-sensitive potassium channel opener, diazoxide (DZX) via an unknown mechanism. One proposed mechanism of cardioprotection is mitochondrial matrix swelling. To establish the relationship between mitochondrial and cellular volume during stress, this study examined the effect of DZX on mitochondrial volume. Isolated mouse mitochondria were exposed to the following solutions: Tyrode, isolation buffer, cardioplegia (CPG)±DZX±ATP-sensitive potassium channel inhibitor, 5-hydroxydecanoate, and metabolic inhibition (MI)±DZX±5-hydroxydecanoate. Mitochondrial volume was measured. DZX resulted in significant mitochondrial swelling (P<0.0001 versus Tyrode). MI and CPG resulted in significant mitochondrial swelling compared with baseline volume. The addition of DZX did not alter the response of mitochondrial volume to CPG (P=0.912) but increased swelling in response to MI (P=0.036). The addition of 5-hydroxydecanoate to MI+DZX or CPG+DZX significantly reduced mitochondrial swelling (P<0.003 MI+DZX versus MI+DZX+5HD; P<0.001 CPG+DZX versus CPG+DZX+5HD). Both cellular and mitochondrial volume increased during exposure to MI and CPG. DZX did not alter mitochondrial volume during CPG; however, it was associated with an increase in mitochondrial volume during MI. 5-Hydroxydecanoate reduced mitochondrial volume during exposure to both stresses with DZX, supporting a role for a mitochondrial ATP-sensitive potassium channel in the mechanism of cardioprotection by DZX.
    Circulation 09/2013; 128(26 Suppl 1):S130-5. · 15.20 Impact Factor
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    ABSTRACT: Channel replacement therapy, based on synthetic channel-forming peptides (CFPs) with the ability to supersede defective endogenous ion channels, is a novel treatment modality that may augment existing interventions against multiple diseases. Previously, we derived CFPs from the second transmembrane segment of the α-subunit of the glycine receptor, M2GlyR, which forms chloride-selective channels in its native form. The best candidate, NK4-M2GlyR T19R, S22W (p22-T19R, S22W), was water-soluble, incorporated into cell membranes and was non-immunogenic, but lacked the structural properties for high conductance and anion selectivity when assembled into a pore. Further studies suggested that the threonine residues at positions 13, 17 and 20 line the pore of assembled p22-T19R, S22W, and here we used 2, 3-diaminopropionic acid (Dap) substitutions to introduce positive charges to the pore-lining interface of the predicted p22-T19R, S22W channel. Dap-substituted p22-T19R, S22W peptides retained the α-helical secondary structure characteristic of their parent peptide, and induced short-circuit transepithelial currents when exposed to the apical membrane of Madin-Darby canine kidney (MDCK) cells; the sequences containing multiple Dap-substituted residues induced larger currents than the peptides with single or no Dap-substitutions. To gain further insights into the effects of Dap residues on the properties of the putative pore, we performed two-electrode voltage clamp electrophysiology on Xenopus oocytes exposed to p22-T19R, S22W or its Dap-modified analogs. We observed that Dap-substituted peptides also induced significantly larger voltage-dependent currents than the parent compound, but there was no apparent change in reversal potential upon replacement of external Na(+), Cl(-) or K(+), indicating that these currents remained non-selective. These results suggest that the introduction of positively charged side chains in predicted pore-lining residues does not improve anion-to-cation selectivity, but results in higher conductance, perhaps due to higher oligomerization numbers.
    Molecular Pharmaceutics 09/2013; · 4.57 Impact Factor
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    ABSTRACT: The concept that pore-forming Kir6.2 and regulatory SUR2A subunits form cardiac ATP-sensitive potassium (KATP) channels is challenged by recent reports that SUR1 is predominant in mouse atrial KATP channels. To assess SUR subunit composition of KATP channels and consequence of KATP activation for action potential duration (APD) in dog heart. Patch-clamp techniques were used on isolated dog cardiomyocytes to investigate KATP channel properties. Dynamic current-clamp, by injection of a linear K(+) conductance to simulate activation of the native current, was employed to study consequences of KATP activation on APD. Metabolic inhibitor (MI)-activated current was not significantly different from pinacidil (SUR2A-specific)-activated current, and both currents were larger than diazoxide (SUR1-specific)-activated current, in both atrium and ventricle. Mean KATP conductance (activated by MI) did not differ significantly between chambers although, within the ventricle, both MI-induced and pinacidil-induced currents tended to decrease from epicardium to endocardium. Dynamic current-clamp results indicate that myocytes with longer baseline APDs are more susceptible to injected "KATP" current, a result reproduced in silico using a canine AP model to simulate Epi and Endo (HRd). Even a small fraction of KATP activation significantly shortens APD in a manner that depends on existing heterogeneity in KATP current and APD.
    Heart rhythm: the official journal of the Heart Rhythm Society 07/2013; · 4.56 Impact Factor
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    ABSTRACT: BACKGROUND: The adenosine triphosphate-sensitive potassium (KATP) channel opener, diazoxide, preserves myocyte volume homeostasis and contractility during stress via an unknown mechanism. Pharmacologic overlap has been suggested between succinate dehydrogenase (SDH) activity and KATP channel modulators. Diazoxide may be cardioprotective due to the inhibition of SDH which may form a portion of the mitochondrial KATP channel. To determine the role of inhibition of SDH in diazoxide's cardioprotection, this study utilized glutathione to prevent the inhibition of SDH. METHODS: SDH activity was measured in isolated mitochondria exposed to succinate (control), malonate (inhibitor of succinate dehydrogenase), diazoxide, and varying concentrations of glutathione alone or in combination with diazoxide. Enzyme activity was measured by spectrophotometric analysis. To evaluate myocyte volume and contractility, cardiac myocytes were superfused with Tyrode's physiologic solution (Tyrode's) (20 minutes), followed by test solution (20 minutes), including Tyrode's, hyperkalemic cardioplegia (stress), cardioplegia + diazoxide, cardioplegia + diazoxide + glutathione, or glutathione alone; followed by Tyrode's (20 minutes). Myocyte volume and contractility were recorded using image grabbing software. RESULTS: Both malonate and diazoxide inhibited succinate dehydrogenase. Glutathione prevented the inhibition of succinate dehydrogenase by diazoxide in a dose-dependent manner. The addition of diazoxide prevented the detrimental myocyte swelling due to cardioplegia alone and this benefit was lost with the addition of glutathione. However, glutathione elicited an independent cardioprotective effect on myocyte contractility. CONCLUSIONS: The ability of diazoxide to provide beneficial myocyte homeostasis during stress involves the inhibition of succinate dehydrogenase, which may also involve the opening of a purported mitochondrial adenosine triphosphate sensitive potassium channel.
    The Annals of thoracic surgery 05/2013; · 3.45 Impact Factor
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    ABSTRACT: ATP-sensitive potassium channel (KATP) activation can drastically shorten action potential duration (APD) in metabolically compromised myocytes. We showed previously that SUR1 with Kir6.2 forms the functional channel in mouse atria while Kir6.2 and SUR2A predominate in ventricles. SUR1 is more sensitive to metabolic stress than SUR2A, raising the possibility that KATP in atria and ventricles may respond differently to metabolic stress. Action potential duration (APD) and calcium transient duration (CaTD) were measured simultaneously in both atria and ventricles by optical mapping of the posterior surface of Langendorff-perfused hearts from C57BL wild-type (WT; n=11), Kir6.2(-/-)(n=5), and SUR1(-/-) (n=6) mice during metabolic inhibition (MI, 0mM glucose+2mM sodium cyanide). After variable delay, MI led to significant shortening of APD in WT hearts. On average, atrial APD shortened by 60.5±2.7% at 13.1±2.1 min (n=6, p<0.01) after onset of MI. Ventricular APD shortening (56.4±10.0% shortening at 18.2±1.8 min) followed atrial APD shortening. In SUR1(-/-) hearts (n=6), atrial APD shortening was abolished, but ventricular shortening (65.0±15.4% at 25.33±4.48 min, p<0.01) was unaffected. In Kir6.2(-/-) hearts, two disparate responses to MI were observed; 3 of 5 hearts displayed slight shortening of APD in the ventricles (24±3%, p<0.05) and atria (39.0±1.9%, p<0.05) but this shortening occurred later and to much less extent than in WT (p<0.05). Marked prolongation of ventricular APD was observed in the remaining hearts (327% and 489% prolongation) and was associated with occurrence of ventricular tachyarrhythmias. The results confirm that Kir6.2 contributes to APD shortening in both atria and ventricle during metabolic stress, and that SUR1 is required for atrial APD shortening while SUR2A is required for ventricular APD shortening. Importantly, the results show that the presence of SUR1-dependent KATP in the atria results in the action potential being more susceptible to metabolically driven shortening than the ventricle.
    Journal of Molecular and Cellular Cardiology 04/2013; · 5.15 Impact Factor
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    ABSTRACT: Kir2.1 channels are uniquely activated by PI(4,5)P2 and can be inhibited by other PIPs. Using biochemical and computational approaches, we assess PIP-channel interactions, and distinguish residues that are energetically critical for binding from those that alter PIP sensitivity by shifting the open-closed equilibrium. Intriguingly, binding of each PIP is disrupted by a different subset of mutations. In silico ligand-docking indicates that PIPs bind to two sites. . The second minor site may correspond to the secondary anionic phospholipid site required for channel activation. However, 96-99% of PIP binding localizes to the first cluster, which corresponds to the general PI(4,5)P2 binding location in recent Kir crystal structures. PIPs can encompass multiple orientations; each di- and tri-phosphorylated species binds with comparable energies, and is favored over mono-phosphorylated PIPs. The data suggest that selective activation by PI(4,5)P2 involves orientational specificity and that other PIPs inhibit this activation through direct competition.
    Journal of Biological Chemistry 04/2013; · 4.65 Impact Factor
  • Colin G Nichols, Gautam K Singh, Dorothy K Grange
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    ABSTRACT: ATP-sensitive potassium (KATP) channels were first discovered in the heart 30 years ago. Reconstitution of KATP channel activity by coexpression of members of the pore-forming inward rectifier gene family (Kir6.1, KCNJ8, and Kir6.2 KCNJ11) with sulfonylurea receptors (SUR1, ABCC8, and SUR2, ABCC9) of the ABCC protein subfamily has led to the elucidation of many details of channel gating and pore properties. In addition, the essential roles of Kir6.x and SURx subunits in generating cardiac and vascular KATP(2) and the detrimental consequences of genetic deletions or mutations in mice have been recognized. However, despite this extensive body of knowledge, there has been a paucity of defined roles of KATP subunits in human cardiovascular diseases, although there are reports of association of a single Kir6.1 variant with the J-wave syndrome in the ECG, and 2 isolated studies have reported association of loss of function mutations in SUR2 with atrial fibrillation and heart failure. Two new studies convincingly demonstrate that mutations in the SUR2 gene are associated with Cantu syndrome, a complex multi-organ disorder characterized by hypertrichosis, craniofacial dysmorphology, osteochondrodysplasia, patent ductus arteriosus, cardiomegaly, pericardial effusion, and lymphoedema. This realization of previously unconsidered consequences provides significant insight into the roles of the KATP channel in the cardiovascular system and suggests novel therapeutic possibilities.
    Circulation Research 03/2013; 112(7):1059-72. · 11.86 Impact Factor
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    ABSTRACT: BACKGROUND: Diazoxide maintains myocyte volume and contractility during stress via an unknown mechanism. The mechanism of action may involve an undefined (genotype unknown) mitochondrial ATP-sensitive potassium channel and is dependent on the ATP-sensitive potassium channel subunit sulfonylurea type 1 receptor (SUR1). The ATP-sensitive potassium channel openers have been shown to inhibit succinate dehydrogenase (SDH) and a gene for a portion of SDH has been found in the SUR intron. Diazoxide may be cardioprotective via inhibition of SDH, which can form part of an ATP-sensitive potassium channel or share its genetic material. This study investigated the role of inhibition of SDH by diazoxide and its relationship to the SUR1 subunit. STUDY DESIGN: Mitochondria were isolated from wild-type and SUR1 knockout mice. Succinate dehydrogenase activity was measured by spectrophotometric analysis of 2,6-dichloroindophenol reduction for 20 minutes as the relative change in absorbance over time. Mitochondria were treated with succinate (20 mM), succinate + 1% dimethylsulfoxide, succinate + malonate (8 mM) (competitive inhibitor of SDH), or succinate + diazoxide (100 μM). RESULTS: Both malonate and diazoxide inhibit SDH activity in mitochondria of wild-type mice and in mice lacking the SUR1 subunit (p < 0.05 vs control). CONCLUSIONS: The ability of DZX to inhibit SDH persists even after deletion of the SUR1 gene. Therefore, the enzyme complex SDH is not dependent on the SUR1 gene. The inhibition of SDH by DZX can play a role in the cardioprotection afforded by DZX; however, this role is independent of the ATP-sensitive potassium channel subunit SUR1.
    Journal of the American College of Surgeons 03/2013; · 4.50 Impact Factor
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    ABSTRACT: Polyamines are ubiquitous organic cations implicated in many physiological processes. Because they are positively charged at physiological pH, carrier-mediated systems are necessary for effective membrane permeation, but the identity of specific polyamine transporter proteins in eukaryotic cells remains unclear. Polyspecific organic cation transporters (OCTs) interact with many natural and xenobiotic monovalent cations and have been reported to transport dicationic compounds, including the short polyamine putrescine. In this study, we used Xenopus oocytes expressing mammalian OCT1 (SLC22A1), OCT2 (SLC22A2) or OCT3 (SLC22A3) to assess binding and transport of longer-chain polyvalent polyamines. In OCT-expressing oocytes, [3H]MPP+ uptake rates were 15- to 35-fold higher than in non-injected oocytes, whereas those for [3H]spermidine increased more modestly above the background, up to 3-fold. This reflected up to 20-fold lower affinity for spermidine than for MPP+; thus, K0.5 for MPP+ was ~50 µM in OCT1, ~170 µM in OCT2, and ~60 µM in OCT3, whereas for spermidine, K0.5 was ~1 mM in OCT1, OCT2 and OCT3. Jmax values for MPP+ and spermidine were within the same range, suggesting that both compounds are transported at a similar turnover rate. To gain further insight into OCT substrate specificity, we screened a selection of structural polyamine analogs for effect on [3H]MPP+ uptake. In general, blocking potency increased with overall hydrophobic character, which indicates that, as for monovalent cations, hydrophobicity is a major requirement for recognition in polyvalent OCT substrates and inhibitors. Our results demonstrate that the natural polyamines are low affinity, but relatively high turnover, substrates for OCTs. The identification of OCTs as polyamine transport systems may contribute to further understanding of the mechanisms involved in polyamine homeostasis, and aid in the design of polyamine-like OCT-targeted drugs.
    Molecular Pharmaceutics 03/2013; · 4.57 Impact Factor
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    ABSTRACT: Steeply voltage-dependent inward rectification of Kir (inwardly-rectifying potassium) channels arises from blockade by cytoplasmic polyamines. These polycationic blockers traverse a long (>70 angstrom) pore, displacing multiple permeant ions, en route to a high affinity binding site that remains loosely defined. We have scanned the effects of cysteine modification at multiple pore-lining positions on the blocking properties of a library of polyamine analogs, demonstrating that the effects of cysteine modification are position and blocker-dependent. Specifically, introduction of positively-charged adducts results in two distinct phenotypes: either disruption of blocker binding, or generation of a barrier to blocker migration, in a consistent pattern that depends on both the length of the polyamine blocker and the position of the modified cysteine. These findings reveal important details about the chemical basis and specific location of high-affinity polyamine binding.
    Journal of Biological Chemistry 01/2013; · 4.65 Impact Factor
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    ABSTRACT: The lipid bilayer is important for maintaining the integrity of cellular compartments and plays a vital role in providing the hydrophobic and charged interactions necessary for membrane protein structure, conformational flexibility and function. To directly assess the lipid dependence of activity for voltage-gated sodium channels, we compared the activity of three bacterial sodium channel homologues (NaChBac, NavMs, and NavSp) by cumulative (22)Na(+) uptake into proteoliposomes containing a 3∶1 ratio of 1-palmitoyl 2-oleoyl phosphatidylethanolamine and different "guest" glycerophospholipids. We observed a unique lipid profile for each channel tested. NavMs and NavSp showed strong preference for different negatively-charged lipids (phosphatidylinositol and phosphatidylglycerol, respectively), whilst NaChBac exhibited a more modest variation with lipid type. To investigate the molecular bases of these differences we used synchrotron radiation circular dichroism spectroscopy to compare structures in liposomes of different composition, and molecular modeling and electrostatics calculations to rationalize the functional differences seen. We then examined pore-only constructs (with voltage sensor subdomains removed) and found that in these channels the lipid specificity was drastically reduced, suggesting that the specific lipid influences on voltage-gated sodium channels arise primarily from their abilities to interact with the voltage-sensing subdomains.
    PLoS ONE 01/2013; 8(4):e61216. · 3.73 Impact Factor
  • Biophysical Journal 01/2013; 104(2):129-. · 3.67 Impact Factor

Publication Stats

7k Citations
1,433.15 Total Impact Points

Institutions

  • 1993–2014
    • Washington University in St. Louis
      • • Department of Surgery
      • • Department of Cell Biology and Physiology
      San Luis, Missouri, United States
  • 2013
    • University of Oxford
      Oxford, England, United Kingdom
    • Government of British Columbia, Canada
      Vancouver, British Columbia, Canada
  • 2012
    • Catholic University of the Sacred Heart
      • School of Pediatrics
      Roma, Latium, Italy
    • Drexel University College of Medicine
      • Department of Pediatrics
      Philadelphia, PA, United States
  • 2011–2012
    • University of London
      • School of Biological Sciences
      Londinium, England, United Kingdom
    • Uniformed Services University of the Health Sciences
      • Department of Anatomy, Physiology & Genetics
      Bethesda, MD, United States
  • 2010–2011
    • University of British Columbia - Vancouver
      • Department of Anesthesiology, Pharmacology and Therapeutics
      Vancouver, British Columbia, Canada
    • University of North Carolina at Chapel Hill
      • Department of Pediatrics
      Chapel Hill, NC, United States
  • 2003–2011
    • University of Washington Seattle
      • Division of Cardiothoracic Surgery
      Seattle, WA, United States
  • 2000–2004
    • Oregon Health and Science University
      • Center for Research on Occupational and Environmental Toxicology (CROET)
      Portland, OR, United States
  • 2002
    • Kuopio University Hospital
      • Department of Paediatrics
      Kuopio, Province of Eastern Finland, Finland
  • 2001
    • University of Michigan
      Ann Arbor, Michigan, United States
  • 1992–1993
    • Baylor College of Medicine
      • Department of Medicine
      Houston, TX, United States