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ABSTRACT: Neuron-glia interactions play a key role in maintaining and regulating the central nervous system. Glial cells are implicated in the function of dopamine neurons and regulate their survival and resistance to injury. Parkinson's disease is characterized by the loss of dopamine neurons in the substantia nigra pars compacta, decreased striatal dopamine levels and consequent onset of extrapyramidal motor dysfunction. Parkinson's disease is a common chronic, neurodegenerative disorder with no effective protective treatment. In the 6-OHDA mouse model of Parkinson's disease, doxycycline administered at a dose that both induces/represses conditional transgene expression in the tetracycline system, mitigates the loss of dopaminergic neurons in the substantia nigra compacta and nerve terminals in the striatum. This protective effect was associated with: (1) a reduction of microglia in normal mice as a result of doxycycline administration per se; (2) a decrease in the astrocyte and microglia response to the neurotoxin 6-OHDA in the globus pallidus and substantia nigra compacta, and (3) the astrocyte reaction in the striatum. Our results suggest that doxycycline blocks 6-OHDA neurotoxicity in vivo by inhibiting microglial and astrocyte expression. This action of doxycycline in nigrostriatal dopaminergic neuron protection is consistent with a role of glial cells in Parkinson's disease neurodegeneration. The neuroprotective effect of doxycycline may be useful in preventing or slowing the progression of Parkinson's disease and other neurodegenerative diseases linked to glia function.
Glia 04/2013; · 4.82 Impact Factor
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ABSTRACT: Aim: The aim of this study was to silence Ether à go-go 1 (EAG1) in glioma cells by RNAi in order to further analyze whether silencing this channel would improve injury caused by interferon gamma (IFN-γ). MATERIALS AND METHODS: EAG1 silencing by the siRNAs EAG1hum_287 and EAG1hum_1727 (sequence targets 5'-GGCCTATTGTGTACAGCAATT-3' and 5'-GGGACTTCCTGAAGCTCTATT-3', respectively) was determined by reverse transcription real-time quantitative polymerase chain reaction (RT-qPCR). Cell viability was measured by the 3-(4,5)-dimethylthiazol-2-y1)-2,5-diphenyltetrazolium bromide (MTT) assay. U-138MG glioma cells were injured by IFN-γ (25 ng/ml, 24 h) with or without the RNAi for EAG1 by a non-viral vector (pKV10.1-3, 0.2 μg). RESULTS: EAG1hum_287 and EAG1hum_1727 caused 0.46- and 0.52-fold decrease in EAG1 mRNA content, respectively. RNAi for EAG1 by pKv10.1-3 strengthened the reduction in cell viability caused by IFN-γ (11.4% versus 40.4%, p<0.05). CONCLUSION: The present study reinforces the notion that EAG1 has a role in glioma biology, suggesting that this channel is a relevant player preserving the cell viability during IFN-γ injury.
Anticancer research 03/2013; 33(3):865-870. · 1.73 Impact Factor
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ABSTRACT: K(V)10.1 is a potassium channel expressed in brain and implicated in tumor progression. We have searched for proteins interacting with K(V)10.1 and identified Rabaptin-5, an effector of the Rab5 GTPase. Both proteins co-localize on large early endosomes induced by Rab5 hyperactivity. Silencing of Rabaptin-5 induces down-regulation of recycling of K(V)10.1 channel in transfected cells and reduction of K(V)10.1 current density in cells natively expressing K(V)10.1, indicating a role of Rabaptin-5 in channel trafficking. K(V)10.1 co-localizes, but does not physically interact, with Rab7 and Rab11. Our data highlights the complex control of the amount of K(V)10.1 channels on the cell surface. STRUCTURED SUMMARY OF PROTEIN INTERACTIONS: Rabaptin-5physically interacts with Kv10.1 by anti bait coimmunoprecipitation (View interaction) Rabaptin-5physically interacts with Rabaptin-5 by two hybrid (View interaction) Kv10.1physically interacts with Kv10.1 by two hybrid (View interaction) Kv10.1physically interacts with Rabaptin-5 by anti bait coimmunoprecipitation (View Interaction: 1, 2) RAB11 and Kv10.1colocalize by fluorescence microscopy (View interaction) Kv10.1 and Rabaptin-5colocalize by fluorescence microscopy (View interaction) Kv10.1physically interacts with Rabaptin-5 by two hybrid (View Interaction: 1, 2) Kv10.1 and RAB7colocalize by fluorescence microscopy (View interaction).
FEBS letters 07/2012; 586(19):3077-84. · 3.54 Impact Factor
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ABSTRACT: Overexpression of the cation-permeable channel TRPM8 in prostate cancers might represent a novel opportunity for their treatment. Inhibitors of TRPM8 reduce the growth of prostate cancer cells. We have used two recently described and highly specific blockers, AMTB and JNJ41876666, and RNAi to determine the relevance of TRPM8 expression in the proliferation of non-tumor and tumor cells. Inhibition of the expression or function of the channel reduces proliferation rates and proliferative fraction in all tumor cells tested, but not of non-tumor prostate cells. We observed no consistent acceleration of growth after stimulation of the channel with menthol or icilin, indicating that basal TRPM8 expression is enough to sustain growth of prostate cancer cells.
PLoS ONE 01/2012; 7(12):e51825. · 4.09 Impact Factor
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ABSTRACT: KV10.1 is a mammalian brain voltage-gated potassium channel whose ectopic expression outside of the brain has been proven relevant for tumor biology. Promotion of cancer cell proliferation by KV10.1 depends largely on ion flow, but some oncogenic properties remain in the absence of ion permeation. Additionally, KV10.1 surface populations are small compared to large intracellular pools. Control of protein turnover within cells is key to both cellular plasticity and homeostasis, and therefore we set out to analyze how endocytic trafficking participates in controlling KV10.1 intracellular distribution and life cycle. To follow plasma membrane KV10.1 selectively, we generated a modified channel of displaying an extracellular affinity tag for surface labeling by α-bungarotoxin. This modification only minimally affected KV10.1 electrophysiological properties. Using a combination of microscopy and biochemistry techniques, we show that KV10.1 is constitutively internalized involving at least two distinct pathways of endocytosis and mainly sorted to lysosomes. This occurs at a relatively fast rate. Simultaneously, recycling seems to contribute to maintain basal KV10.1 surface levels. Brief KV10.1 surface half-life and rapid lysosomal targeting is a relevant factor to be taken into account for potential drug delivery and targeting strategies directed against KV10.1 on tumor cells.
PLoS ONE 10/2011; 6(10). · 4.09 Impact Factor
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ABSTRACT: The search for strategies to target ion channels for therapeutic applications has become of increasing interest. Especially, the potassium channel K(V)10.1 (Ether-á-go-go) is attractive as target since this surface protein is virtually not detected in normal tissue outside the central nervous system, but is expressed in approximately 70% of tumors from different origins.
We designed a single-chain antibody against an extracellular region of K(V)10.1 (scFv62) and fused it to the human soluble TRAIL. The K(V)10.1-specific scFv62 antibody -TRAIL fusion protein was expressed in CHO-K1 cells, purified by chromatography and tested for biological activity.
Prostate cancer cells, either positive or negative for K(V)10.1 were treated with the purified construct. After sensitization with cytotoxic drugs, scFv62-TRAIL induced apoptosis only in K(V)10.1-positive cancer cells, but not in non-tumor cells, nor in tumor cells lacking K(V)10.1 expression. In co-cultures with K(V)10.1-positive cancer cells the fusion protein also induced apoptosis in bystander K(V)10.1-negative cancer cells, while normal prostate epithelial cells were not affected when present as bystander.
K(V)10.1 represents a novel therapeutic target for cancer. We could design a strategy that selectively kills tumor cells based on a K(V)10.1-specific antibody.
Molecular Cancer 09/2011; 10:109. · 3.99 Impact Factor
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Cindy Sharon Ortiz,
Daniel Montante-Montes,
Milena Saqui-Salces,
Luz María Hinojosa,
Armando Gamboa-Dominguez,
Elisabeth Hernández-Gallegos,
Braulio Martínez-Benítez,
María Del Rosario Solís-Pancoatl,
Enrique Garcia-Villa,
Ana Ramírez,
Ricardo Aguilar-Guadarrama,
Patricio Gariglio,
Luis A Pardo, Walter Stühmer,
Javier Camacho
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ABSTRACT: Human ether à-go-go 1 (Eag1) potassium channels are potential tumor markers and therapeutic targets for several types of malignancies, including cervical cancer. Estrogens and human papilloma virus oncogenes regulate Eag1 gene expression, suggesting that Eag1 may already be present in pre-malignant lesions. Therefore, Eag1 could be used as an early marker and/or a potential risk indicator for cervical cancer. Consequently, we studied Eag1 protein expression by immunochemistry in cervical cancer cell lines, normal keratinocytes, cervical cytologies from intraepithelial lesions, biopsies from cervical intraepithelial neoplasias (CIN 1, 2 and 3) and in normal smears from patients taking or not taking estrogens. Two hundred and eighty-six samples obtained by liquid-based cytology and fifteen CIN biopsies were studied. We observed Eag1 protein expression in the cervical cancer cell lines, as opposed to normal keratinocytes. Eag1 was found in 67% of the cervical cytologies from low-grade intra-epithelial lesions and in 92% of the samples from high-grade intraepithelial lesions, but only in 27% of the normal samples. Noteworthy, morphologically normal cells obtained from dysplastic samples also exhibited Eag1 expression. In CIN biopsies we found that the higher the grade of the lesion, the broader the Eag1 protein distribution. Almost 50% of the normal patients taking estrogens displayed Eag1 expression. We suggest Eag1 as a potential marker of cervical dysplasia and a risk indicator for developing cervical lesions in patients taking estrogens. Eag1 detection in cervical cancer screening programs should help to improve early diagnosis and decrease mortality rates from this disease.
Oncology Reports 08/2011; 26(6):1377-83. · 1.84 Impact Factor
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PROTEOMICS - CLINICAL APPLICATIONS 08/2011; 5(7-8):471. · 1.81 Impact Factor
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ABSTRACT: Transfection has become an everyday technique widely used for functional studies in living cells. The choice of the particular transfection method is usually determined by its efficiency and toxicity, and possible functional consequences specific to the method used are normally overlooked. We describe here that nucleofection, a method increasingly used because of its convenience and high efficiency, increases the metabolic rate of some cancer cells, which can be misleading when used as a measure of proliferation. Moreover, nucleofection can alter the subcellular expression pattern of the transfected protein. These undesired effects are independent of the transfected nucleic acid, but depend on the particular cell line used. Therefore, the interpretation of functional data using this technology requires further controls and caution.
Molecular Biology Reports 06/2011; 39(3):2187-94. · 2.93 Impact Factor
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ABSTRACT: Ectopically expressed human KV10.1 channels are relevant players in tumor biology. However, their function as ion channels at the plasma membrane does not totally explain their crucial role in tumors. Both in native and heterologous systems, it has been observed that a majority of KV10.1 channels remain at intracellular locations. In this study we investigated the localization and possible roles of perinuclear KV10.1. We show that KV10.1 is expressed at the inner nuclear membrane in both human and rat models; it co-purifies with established inner nuclear membrane markers, shows resistance to detergent extraction and restricted mobility, all of them typical features of proteins at the inner nuclear membrane. KV10.1 channels at the inner nuclear membrane are not all transported directly from the ER but rather have been exposed to the extracellular milieu. Patch clamp experiments on nuclei devoid of external nuclear membrane reveal the existence of channel activity compatible with KV10.1. We hypothesize that KV10.1 channels at the nuclear envelope might participate in the homeostasis of nuclear K+, or indirectly interact with heterochromatin, both factors known to affect gene expression.
PLoS ONE 05/2011; 6(5). · 4.09 Impact Factor
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Sabrina Grube,
Martin F Gerchen,
Bartosz Adamcio,
Luis A Pardo,
Sabine Martin,
Dörthe Malzahn,
Sergi Papiol,
Martin Begemann,
Katja Ribbe,
Heidi Friedrichs,
Konstantin A Radyushkin,
Michael Müller,
Fritz Benseler,
Joachim Riggert,
Peter Falkai,
Heike Bickeböller,
Klaus-Armin Nave,
Nils Brose, Walter Stühmer,
Hannelore Ehrenreich
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ABSTRACT: KCNN3, encoding the small conductance calcium-activated potassium channel SK3, harbours a polymorphic CAG repeat in the amino-terminal coding region with yet unproven function. Hypothesizing that KCNN3 genotypes do not influence susceptibility to schizophrenia but modify its phenotype, we explored their contribution to specific schizophrenic symptoms. Using the Göttingen Research Association for Schizophrenia (GRAS) data collection of schizophrenic patients (n = 1074), we performed a phenotype-based genetic association study (PGAS) of KCNN3. We show that long CAG repeats in the schizophrenic sample are specifically associated with better performance in higher cognitive tasks, comprising the capacity to discriminate, select and execute (p < 0.0001). Long repeats reduce SK3 channel function, as we demonstrate by patch-clamping of transfected HEK293 cells. In contrast, modelling the opposite in mice, i.e. KCNN3 overexpression/channel hyperfunction, leads to selective deficits in higher brain functions comparable to those influenced by SK3 conductance in humans. To conclude, KCNN3 genotypes modify cognitive performance, shown here in a large sample of schizophrenic patients. Reduction of SK3 function may constitute a pharmacological target to improve cognition in schizophrenia and other conditions with cognitive impairment.
EMBO Molecular Medicine 03/2011; 3(6):309-19. · 10.33 Impact Factor
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ABSTRACT: The molecular basis of bipolar disorder (BD) is still unknown as is the mechanism through which lithium, the therapy of choice, exerts its effects in treatment of BD. So far, no biomarkers exist to facilitate diagnosis of BD or treatment evaluation. To investigate whether BD and its treatment with lithium leaves a characteristic signature in the serum proteome, we used SELDI-TOF MS to analyze individual serum samples from BD patients treated with lithium (BD-plus-Li, n=15) or other drugs (BD-minus-Li, n=10) and from healthy controls (n=15). Interestingly, features of 28 kDa (one peak) and 14 kDa (three peaks) showed a decreased level in the BD-minus-Li group and a level restored to that of the control group in the BD-plus-Li group. To reveal the identity of these features, we subjected pooled serum samples from both BD groups to the 2-D DIGE technology and identified 28 kDa apolipoprotein A-I (apo A-I) and three 14 kDa fragments thereof as upregulated in the BD-plus-Li group. Immunoturbidimetry, a routine clinical assay, verified the characteristic apo A-I signature in individual serum samples. In conclusion, we propose apo A-I as a candidate marker that can visualize response to lithium treatment at the serum protein level.
Proteomics 01/2011; 11(2):261-9. · 4.43 Impact Factor
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ABSTRACT: Ectopically expressed human K(V)10.1 channels are relevant players in tumor biology. However, their function as ion channels at the plasma membrane does not totally explain their crucial role in tumors. Both in native and heterologous systems, it has been observed that a majority of K(V)10.1 channels remain at intracellular locations. In this study we investigated the localization and possible roles of perinuclear K(V)10.1. We show that K(V)10.1 is expressed at the inner nuclear membrane in both human and rat models; it co-purifies with established inner nuclear membrane markers, shows resistance to detergent extraction and restricted mobility, all of them typical features of proteins at the inner nuclear membrane. K(V)10.1 channels at the inner nuclear membrane are not all transported directly from the ER but rather have been exposed to the extracellular milieu. Patch clamp experiments on nuclei devoid of external nuclear membrane reveal the existence of channel activity compatible with K(V)10.1. We hypothesize that K(V)10.1 channels at the nuclear envelope might participate in the homeostasis of nuclear K(+), or indirectly interact with heterochromatin, both factors known to affect gene expression.
PLoS ONE 01/2011; 6(5):e19257. · 4.09 Impact Factor
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[show abstract]
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ABSTRACT: K(V)10.1 is a mammalian brain voltage-gated potassium channel whose ectopic expression outside of the brain has been proven relevant for tumor biology. Promotion of cancer cell proliferation by K(V)10.1 depends largely on ion flow, but some oncogenic properties remain in the absence of ion permeation. Additionally, K(V)10.1 surface populations are small compared to large intracellular pools. Control of protein turnover within cells is key to both cellular plasticity and homeostasis, and therefore we set out to analyze how endocytic trafficking participates in controlling K(V)10.1 intracellular distribution and life cycle. To follow plasma membrane K(V)10.1 selectively, we generated a modified channel of displaying an extracellular affinity tag for surface labeling by α-bungarotoxin. This modification only minimally affected K(V)10.1 electrophysiological properties. Using a combination of microscopy and biochemistry techniques, we show that K(V)10.1 is constitutively internalized involving at least two distinct pathways of endocytosis and mainly sorted to lysosomes. This occurs at a relatively fast rate. Simultaneously, recycling seems to contribute to maintain basal K(V)10.1 surface levels. Brief K(V)10.1 surface half-life and rapid lysosomal targeting is a relevant factor to be taken into account for potential drug delivery and targeting strategies directed against K(V)10.1 on tumor cells.
PLoS ONE 01/2011; 6(10):e26329. · 4.09 Impact Factor
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Katja Ribbe,
Heidi Friedrichs,
Martin Begemann,
Sabrina Grube,
Sergi Papiol,
Anne Kästner,
Martin F Gerchen,
Verena Ackermann,
Asieh Tarami,
Annika Treitz, [......],
Udo Schneider,
Hans-Joachim Schwarz,
Birgit Kröner-Herwig,
Ursula Havemann-Reinecke,
Jens Frahm, Walter Stühmer,
Peter Falkai,
Nils Brose,
Klaus-Armin Nave,
Hannelore Ehrenreich
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ABSTRACT: Schizophrenia is the collective term for an exclusively clinically diagnosed, heterogeneous group of mental disorders with still obscure biological roots. Based on the assumption that valuable information about relevant genetic and environmental disease mechanisms can be obtained by association studies on patient cohorts of ≥ 1000 patients, if performed on detailed clinical datasets and quantifiable biological readouts, we generated a new schizophrenia data base, the GRAS (Göttingen Research Association for Schizophrenia) data collection. GRAS is the necessary ground to study genetic causes of the schizophrenic phenotype in a 'phenotype-based genetic association study' (PGAS). This approach is different from and complementary to the genome-wide association studies (GWAS) on schizophrenia.
For this purpose, 1085 patients were recruited between 2005 and 2010 by an invariable team of traveling investigators in a cross-sectional field study that comprised 23 German psychiatric hospitals. Additionally, chart records and discharge letters of all patients were collected.
The corresponding dataset extracted and presented in form of an overview here, comprises biographic information, disease history, medication including side effects, and results of comprehensive cross-sectional psychopathological, neuropsychological, and neurological examinations. With >3000 data points per schizophrenic subject, this data base of living patients, who are also accessible for follow-up studies, provides a wide-ranging and standardized phenotype characterization of as yet unprecedented detail.
The GRAS data base will serve as prerequisite for PGAS, a novel approach to better understanding 'the schizophrenias' through exploring the contribution of genetic variation to the schizophrenic phenotypes.
BMC Psychiatry 11/2010; 10:91. · 2.55 Impact Factor
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ABSTRACT: Ion channels are involved in a variety of tumors. In particular, potassium channels are expressed abnormally in many cancer types, where their pharmacologic manipulation impairs tumor progression. Since this group of molecules has been successfully targeted for decades in other therapeutic areas, there is a significant body of knowledge on the pharmacology of potassium channels. Several groups of potassium channels with defined molecular identities have been proposed as candidates for therapeutic intervention. The strategies put forward range from classical small molecule blockade to gene therapy approaches, and include the use of potassium channels as targets for adjuvant therapy. We will discuss the reasons for these proposals and explore possible future developments.
Future medicinal chemistry 05/2010; 2(5):745-55. · 2.52 Impact Factor
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ABSTRACT: The voltage-gated potassium channel hEag1 (KV10.1) has been related to cancer biology. The physiological expression of the human channel is restricted to the brain but it is frequently and abundantly expressed in many solid tumors, thereby making it a promising target for a specific diagnosis and therapy. Because chronic lymphatic leukemia has been described not to express hEag1, it has been assumed that the channel is not expressed in hematopoietic neoplasms in general.
Here we show that this assumption is not correct, because the channel is up-regulated in myelodysplastic syndromes, chronic myeloid leukemia and almost half of the tested acute myeloid leukemias in a subtype-dependent fashion. Most interestingly, channel expression strongly correlated with increasing age, higher relapse rates and a significantly shorter overall survival. Multivariate Cox regression analysis revealed hEag1 expression levels in AML as an independent predictive factor for reduced disease-free and overall survival; such an association had not been reported before. As a functional correlate, specific hEag1 blockade inhibited the proliferation and migration of several AML cell lines and primary cultured AML cells in vitro.
Our observations implicate hEag1 as novel target for diagnostic, prognostic and/or therapeutic approaches in AML.
Molecular Cancer 01/2010; 9:18. · 3.99 Impact Factor
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ABSTRACT: Voltage-gated ion channels are main players involved in fast synaptic events. However, only slow intracellular mechanisms have so far been described for controlling their localization as real-time visualization of endogenous voltage-gated channels at high temporal and spatial resolution has not been achieved yet. Using a specific extracellular antibody and quantum dots we reveal and characterize lateral mobility as a faster mechanism to dynamically control the number of endogenous ether-a-go-go (Eag)1 ion channels inside synapses. We visualize Eag1 entering and leaving synapses by lateral diffusion in the plasma membrane of rat hippocampal neurons. Mathematical analysis of their trajectories revealed how the motion of Eag1 gets restricted when the channels diffuse into the synapse, suggesting molecular interactions between Eag1 and synaptic components. In contrast, Eag1 channels switch to Brownian movement when they exit synapses and diffuse into extrasynaptic membranes. Furthermore, we demonstrate that the mobility of Eag1 channels is specifically regulated inside synapses by actin filaments, microtubules and electrical activity. In summary, using single-particle-tracking techniques with quantum dots nanocrystals, our study shows for the first time the lateral diffusion of an endogenous voltage-gated ion channel in neurons. The location-dependent constraints imposed by cytoskeletal elements together with the regulatory role of electrical activity strongly suggest a pivotal role for the mobility of voltage-gated ion channels in synaptic activity.
PLoS ONE 01/2010; 5(1):e8858. · 4.09 Impact Factor
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ABSTRACT: Abstract
Background
The voltage-gated potassium channel hEag1 (K<sub>V</sub>10.1) has been related to cancer biology. The physiological expression of the human channel is restricted to the brain but it is frequently and abundantly expressed in many solid tumors, thereby making it a promising target for a specific diagnosis and therapy. Because chronic lymphatic leukemia has been described not to express hEag1, it has been assumed that the channel is not expressed in hematopoietic neoplasms in general.
Results
Here we show that this assumption is not correct, because the channel is up-regulated in myelodysplastic syndromes, chronic myeloid leukemia and almost half of the tested acute myeloid leukemias in a subtype-dependent fashion. Most interestingly, channel expression strongly correlated with increasing age, higher relapse rates and a significantly shorter overall survival. Multivariate Cox regression analysis revealed hEag1 expression levels in AML as an independent predictive factor for reduced disease-free and overall survival; such an association had not been reported before. As a functional correlate, specific hEag1 blockade inhibited the proliferation and migration of several AML cell lines and primary cultured AML cells in vitro .
Conclusion
Our observations implicate hEag1 as novel target for diagnostic, prognostic and/or therapeutic approaches in AML.
Molecular Cancer. 01/2010;
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ABSTRACT: Ca(2+)-mediated regulation of ion channels provides a link between intracellular signaling pathways and membrane electrical activity. Intracellular Ca(2+) inhibits the voltage-gated potassium channel EAG1 through the direct binding of calmodulin (CaM). Three CaM binding sites (BD-C1: 674-683, BD-C2: 711-721, BD-N: 151-165) have been identified in a peptide screen and were proposed to mediate binding. The participation of the three sites in CaM binding to the native channel, however, remains unclear.
Here we studied the binding of Ca(2+)/CaM to the EAG channel by visualizing the interaction between YFP-labeled CaM and Cerulean-labeled hEAG1 in mammalian cells by FRET. The results of our cellular approach substantiate that two CaM binding sites are predominantly involved; the high-affinity 1-8-14 based CaM binding domain in the N-terminus and the second C-terminal binding domain BD-C2. Mutations at these sites completely abolished CaM binding to hEAG1.
We demonstrated that the BD-N and BD-C2 binding domains are sufficient for CaM binding to the native channel, and, therefore, that BD-C1 is unable to bind CaM independently.
PLoS ONE 01/2010; 5(5):e10873. · 4.09 Impact Factor
