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Chen X, Tang H, Lu K, Niu Z, Sheng W, Hwang HY, Pang PYK, Phillips JD, Khoynezhad A, Qu X, Li B, Han W. Gene modules and genes associated with postoperative atrial fibrillation: weighted gene co-expression network analysis and circRNA-miRNA-mRNA regulatory network analysis. J Thorac Dis 2023; 15:4949-4960. [PMID: 37868904 PMCID: PMC10586969 DOI: 10.21037/jtd-23-1179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Accepted: 08/31/2023] [Indexed: 10/24/2023]
Abstract
Background Atrial fibrillation (AF) is the most common complication in patients undergoing cardiac surgery. However, the pathogenesis of postoperative AF (POAF) is elusive, and research related to this topic is sparse. Our study aimed to identify key gene modules and genes and to conduct a circular RNA (circRNA)-microRNA (miRNA)-messenger RNA (mRNA) regulatory network analysis of POAF on the basis of bioinformatic analysis. Methods The GSE143924 and GSE97455 data sets from the Gene Expression Omnibus (GEO) database were analyzed. Weighted gene co-expression network analysis (WGCNA) was used to identify the key gene modules and genes related to POAF. A circRNA-miRNA-mRNA regulatory network was also built according to differential expression analysis. Functional enrichment analysis was further performed according to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. Results WGCNA identified 2 key gene modules and 44 key genes that were significantly related to POAF. Functional enrichment analysis of these key genes implicated the following important biological processes (BPs): endosomal transport, protein kinase B signaling, and transcription regulation. The circRNA-miRNA-mRNA regulatory network suggested that KLF10 may take critical part in POAF. Moreover, 2 novel circRNAs, hsa_circRNA_001654 and hsa_circRNA_005899, and 2 miRNAs, hsa-miR-19b-3p and hsa-miR-30a-5p, which related with KLF10, were involved in the network. Conclusions Our study provides foundational expression profiles following POAF based on WGCNA. The circRNA-miRNA-mRNA network offers insights into the BPs and underlying mechanisms of POAF.
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Affiliation(s)
- Xiaomeng Chen
- Department of Cardiology, Qingdao Municipal Hospital, Qingdao University, Qingdao, China
- Department of Cardiology, Qingdao Municipal Hospital, University of Health and Rehabilitation Sciences, Qingdao, China
| | - Huaiguang Tang
- Department of Cardiology, Qingdao Municipal Hospital, Qingdao University, Qingdao, China
- Department of Cardiology, Qingdao Municipal Hospital, University of Health and Rehabilitation Sciences, Qingdao, China
| | - Kongmiao Lu
- Department of Pulmonary and Critical Care Medicine, University of Health and Rehabilitation Sciences, Qingdao, China
| | - Zhaozhuo Niu
- Department of Cardiovascular Surgery, University of Health and Rehabilitation Sciences, Qingdao, China
| | - Wei Sheng
- Department of Cardiovascular Surgery, University of Health and Rehabilitation Sciences, Qingdao, China
| | - Ho Young Hwang
- Department of Thoracic and Cardiovascular Surgery, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Philip Y. K. Pang
- Department of Cardiothoracic Surgery, National Heart Centre Singapore, Singapore, Singapore
| | - Joseph D. Phillips
- Section of Thoracic Surgery, Dartmouth-Hitchcock Medical Center, 1 Medical Center Dr., Lebanon, NH, USA
| | - Ali Khoynezhad
- Department of Cardiovascular Surgery, MemorialCare Heart and Vascular Institute, Long Beach, CA, USA
| | - Xiaolu Qu
- Department of Pulmonary and Critical Care Medicine, University of Health and Rehabilitation Sciences, Qingdao, China
| | - Bingong Li
- Department of Cardiology, Qingdao Municipal Hospital, Qingdao University, Qingdao, China
- Department of Cardiology, Qingdao Municipal Hospital, University of Health and Rehabilitation Sciences, Qingdao, China
| | - Wei Han
- Department of Pulmonary and Critical Care Medicine, University of Health and Rehabilitation Sciences, Qingdao, China
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2
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Liu T, Li T, Xu D, Wang Y, Zhou Y, Wan J, Huang CLH, Tan X. Small-conductance calcium-activated potassium channels in the heart: expression, regulation and pathological implications. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220171. [PMID: 37122223 PMCID: PMC10150224 DOI: 10.1098/rstb.2022.0171] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Accepted: 12/25/2022] [Indexed: 05/02/2023] Open
Abstract
Ca2+-activated K+ channels are critical to cellular Ca2+ homeostasis and excitability; they couple intracellular Ca2+ and membrane voltage change. Of these, the small, 4-14 pS, conductance SK channels include three, KCNN1-3 encoded, SK1/KCa2.1, SK2/KCa2.2 and SK3/KCa2.3, channel subtypes with characteristic, EC50 ∼ 10 nM, 40 pM, 1 nM, apamin sensitivities. All SK channels, particularly SK2 channels, are expressed in atrial, ventricular and conducting system cardiomyocytes. Pharmacological and genetic modification results have suggested that SK channel block or knockout prolonged action potential durations (APDs) and effective refractory periods (ERPs) particularly in atrial, but also in ventricular, and sinoatrial, atrioventricular node and Purkinje myocytes, correspondingly affect arrhythmic tendency. Additionally, mitochondrial SK channels may decrease mitochondrial Ca2+ overload and reactive oxygen species generation. SK channels show low voltage but marked Ca2+ dependences (EC50 ∼ 300-500 nM) reflecting their α-subunit calmodulin (CaM) binding domains, through which they may be activated by voltage-gated or ryanodine-receptor Ca2+ channel activity. SK function also depends upon complex trafficking and expression processes and associations with other ion channels or subunits from different SK subtypes. Atrial and ventricular clinical arrhythmogenesis may follow both increased or decreased SK expression through decreased or increased APD correspondingly accelerating and stabilizing re-entrant rotors or increasing incidences of triggered activity. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.
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Affiliation(s)
- Ting Liu
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Tao Li
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
- Department of Cardiology, the Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Dandi Xu
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Yan Wang
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Yafei Zhou
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Juyi Wan
- Department of Cardiovascular Surgery, the Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
| | - Christopher L.-H. Huang
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
- Physiological Laboratory and Department of Biochemistry, University of Cambridge, Cambridge CB2 3EG, UK
| | - Xiaoqiu Tan
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
- Department of Cardiology, the Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
- Department of Physiology, School of Basic Medical Sciences, Southwest Medical University, Luzhou, Sichuan 646000, People's Republic of China
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3
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An X, Lee J, Kim GH, Kim HJ, Pyo HJ, Kwon I, Cho H. Modulation of I Ks channel-PIP 2 interaction by PRMT1 plays a critical role in the control of cardiac repolarization. J Cell Physiol 2022; 237:3069-3079. [PMID: 35580065 PMCID: PMC9543859 DOI: 10.1002/jcp.30775] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 04/18/2022] [Accepted: 04/25/2022] [Indexed: 11/12/2022]
Abstract
Recent studies have shown that protein arginine methyltransferase 1 (PRMT1) is highly expressed in the human heart, and loss of PRMT1 contributes to cardiac remodeling in the heart failure. However, the functional importance of PRMT1 in cardiac ion channels remains uncertain. The slow activating delayed rectifier K+ (IKs) channel is a cardiac K+ channel composed of KCNQ1 and KCNE1 subunits and is a new therapeutic target for treating lethal arrhythmias in many cardiac pathologies, especially heart failure. Here, we demonstrate that PRMT1 is a critical regulator of the IKs channel and cardiac rhythm. In the guinea pig ventricular myocytes, treatment with furamidine, a PRMT1‐specific inhibitor, prolonged the action potential duration (APD). We further show that this APD prolongation was attributable to IKs reduction. In HEK293T cells expressing human KCNQ1 and KCNE1, inhibiting PRMT1 via furamidine reduced IKs and concurrently decreased the arginine methylation of KCNQ1, a pore‐forming α‐subunit. Evidence presented here indicates that furamidine decreased IKs mainly by lowering the affinity of IKs channels for the membrane phospholipid, phosphatidylinositol 4,5‐bisphosphate (PIP2), which is crucial for pore opening. Finally, applying exogenous PIP2 to cardiomyocytes prevented the furamidine‐induced IKs reduction and APD prolongation. Taken together, these results indicate that PRMT1 positively regulated IKs activity through channel–PIP2 interaction, thereby restricting excessive cardiac action potential.
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Affiliation(s)
- Xue An
- Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Jiwon Lee
- Department of Anatomy and Cell Biology, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Ga Hye Kim
- Department of Anatomy and Cell Biology, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Hyun-Ji Kim
- Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Hyun-Jeong Pyo
- Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Ilmin Kwon
- Department of Anatomy and Cell Biology, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Hana Cho
- Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, Korea
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4
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Darkow E, Nguyen TT, Stolina M, Kari FA, Schmidt C, Wiedmann F, Baczkó I, Kohl P, Rajamani S, Ravens U, Peyronnet R. Small Conductance Ca 2 +-Activated K + (SK) Channel mRNA Expression in Human Atrial and Ventricular Tissue: Comparison Between Donor, Atrial Fibrillation and Heart Failure Tissue. Front Physiol 2021; 12:650964. [PMID: 33868017 PMCID: PMC8047327 DOI: 10.3389/fphys.2021.650964] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 03/01/2021] [Indexed: 12/25/2022] Open
Abstract
In search of more efficacious and safe pharmacological treatments for atrial fibrillation (AF), atria-selective antiarrhythmic agents have been promoted that target ion channels principally expressed in the atria. This concept allows one to engage antiarrhythmic effects in atria, but spares the ventricles from potentially proarrhythmic side effects. It has been suggested that cardiac small conductance Ca2+-activated K+ (SK) channels may represent an atria-selective target in mammals including humans. However, there are conflicting data concerning the expression of SK channels in different stages of AF, and recent findings suggest that SK channels are upregulated in ventricular myocardium when patients develop heart failure. To address this issue, RNA-sequencing was performed to compare expression levels of three SK channels (KCNN1, KCNN2, and KCNN3) in human atrial and ventricular tissue samples from transplant donor hearts (no cardiac disease), and patients with cardiac disease in sinus rhythm or with AF. In addition, for control purposes expression levels of several genes known to be either chamber-selective or differentially expressed in AF and heart failure were determined. In atria, as compared to ventricle from transplant donor hearts, we confirmed higher expression of KCNN1 and KCNA5, and lower expression of KCNJ2, whereas KCNN2 and KCNN3 were statistically not differentially expressed. Overall expression of KCNN1 was low compared to KCNN2 and KCNN3. Comparing atrial tissue from patients with AF to sinus rhythm samples we saw downregulation of KCNN2 in AF, as previously reported. When comparing ventricular tissue from heart failure patients to non-diseased samples, we found significantly increased ventricular expression of KCNN3 in heart failure, as previously published. The other channels showed no significant difference in expression in either disease. Our results add weight to the view that SK channels are not likely to be an atria-selective target, especially in failing human hearts, and modulators of these channels may prove to have less utility in treating AF than hoped. Whether targeting SK1 holds potential remains to be elucidated.
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Affiliation(s)
- Elisa Darkow
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, Freiburg im Breisgau, Germany.,Medical Center and Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany.,Spemann Graduate School of Biology and Medicine (SGBM), University of Freiburg, Freiburg im Breisgau, Germany.,Faculty of Biology, University of Freiburg, Freiburg im Breisgau, Germany
| | - Thong T Nguyen
- Genome Analysis Unit, Amgen Research, Amgen Inc., South San Francisco, CA, United States
| | - Marina Stolina
- Department of Cardiometabolic Disorders, Amgen Research, Amgen Inc., Thousand Oaks, CA, United States
| | - Fabian A Kari
- Medical Center and Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany.,Department of Cardiovascular Surgery, University Heart Center Freiburg-Bad Krozingen, Freiburg im Breisgau, Germany
| | - Constanze Schmidt
- Department of Cardiology, University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Center for Cardiovascular Research) Partner Site Heidelberg/Mannheim, Heidelberg University, Heidelberg, Germany
| | - Felix Wiedmann
- Department of Cardiology, University Hospital Heidelberg, Heidelberg, Germany.,DZHK (German Center for Cardiovascular Research) Partner Site Heidelberg/Mannheim, Heidelberg University, Heidelberg, Germany
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
| | - Peter Kohl
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, Freiburg im Breisgau, Germany.,Medical Center and Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany.,CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, Freiburg im Breisgau, Germany
| | - Sridharan Rajamani
- Translational Safety and Bioanalytical Sciences, Amgen Research, Amgen Inc., South San Francisco, CA, United States
| | - Ursula Ravens
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, Freiburg im Breisgau, Germany.,Medical Center and Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany
| | - Rémi Peyronnet
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, Freiburg im Breisgau, Germany.,Medical Center and Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany
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5
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Macias A, de la Cruz A, Peraza DA, de Benito-Bueno A, Gonzalez T, Valenzuela C. K V1.5-K Vβ1.3 Recycling Is PKC-Dependent. Int J Mol Sci 2021; 22:ijms22031336. [PMID: 33572906 PMCID: PMC7866247 DOI: 10.3390/ijms22031336] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 01/12/2021] [Accepted: 01/26/2021] [Indexed: 11/26/2022] Open
Abstract
KV1.5 channel function is modified by different regulatory subunits. KVβ1.3 subunits assemble with KV1.5 channels and induce a fast and incomplete inactivation. Inhibition of PKC abolishes the KVβ1.3-induced fast inactivation, decreases the amplitude of the current KV1.5–KVβ1.3 and modifies their pharmacology likely due to changes in the traffic of KV1.5–KVβ1.3 channels in a PKC-dependent manner. In order to analyze this hypothesis, HEK293 cells were transfected with KV1.5–KVβ1.3 channels, and currents were recorded by whole-cell configuration of the patch-clamp technique. The presence of KV1.5 in the membrane was analyzed by biotinylation techniques, live cell imaging and confocal microscopy approaches. PKC inhibition resulted in a decrease of 33 ± 7% of channels in the cell surface due to reduced recycling to the plasma membrane, as was confirmed by confocal microscopy. Live cell imaging indicated that PKC inhibition almost abolished the recycling of the KV1.5–KVβ1.3 channels, generating an accumulation of channels into the cytoplasm. All these results suggest that the trafficking regulation of KV1.5–KVβ1.3 channels is dependent on phosphorylation by PKC and, therefore, they could represent a clinically relevant issue, mainly in those diseases that exhibit modifications in PKC activity.
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Affiliation(s)
- Alvaro Macias
- Instituto de Investigaciones Biomédicas Madrid CSIC-UAM. C/Arturo Duperier 4, 28029 Madrid, Spain; (A.d.l.C.); (D.A.P.); (A.d.B.-B.); (T.G.)
- CIBER Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain
- Correspondence: (A.M.); (C.V.); Tel.: +34-91-453-1200 (A.M.); +34-91-585-4493 (C.V.)
| | - Alicia de la Cruz
- Instituto de Investigaciones Biomédicas Madrid CSIC-UAM. C/Arturo Duperier 4, 28029 Madrid, Spain; (A.d.l.C.); (D.A.P.); (A.d.B.-B.); (T.G.)
| | - Diego A. Peraza
- Instituto de Investigaciones Biomédicas Madrid CSIC-UAM. C/Arturo Duperier 4, 28029 Madrid, Spain; (A.d.l.C.); (D.A.P.); (A.d.B.-B.); (T.G.)
- CIBER Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain
| | - Angela de Benito-Bueno
- Instituto de Investigaciones Biomédicas Madrid CSIC-UAM. C/Arturo Duperier 4, 28029 Madrid, Spain; (A.d.l.C.); (D.A.P.); (A.d.B.-B.); (T.G.)
- CIBER Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain
| | - Teresa Gonzalez
- Instituto de Investigaciones Biomédicas Madrid CSIC-UAM. C/Arturo Duperier 4, 28029 Madrid, Spain; (A.d.l.C.); (D.A.P.); (A.d.B.-B.); (T.G.)
- CIBER Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain
- Department of Biochemistry, School of Medicine, Universidad Autónoma de Madrid, 28029 Madrid, Spain
- Instituto de Investigación Sanitaria del Hospital Universitario La Paz (IdiPAZ), 28029 Madrid, Spain
| | - Carmen Valenzuela
- Instituto de Investigaciones Biomédicas Madrid CSIC-UAM. C/Arturo Duperier 4, 28029 Madrid, Spain; (A.d.l.C.); (D.A.P.); (A.d.B.-B.); (T.G.)
- CIBER Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain
- Correspondence: (A.M.); (C.V.); Tel.: +34-91-453-1200 (A.M.); +34-91-585-4493 (C.V.)
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6
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Geng L, Wang S, Zhang F, Xiong K, Huang J, Zhao T, Shi D, Lv F, Li L, Liang D, Cui Y, Liu Y, Xie D, Chen YH. SNX17 (Sorting Nexin 17) Mediates Atrial Fibrillation Onset Through Endocytic Trafficking of the Kv1.5 (Potassium Voltage-Gated Channel Subfamily A Member 5) Channel. Circ Arrhythm Electrophysiol 2020; 12:e007097. [PMID: 30939909 DOI: 10.1161/circep.118.007097] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
BACKGROUND Kv1.5 (Potassium voltage-gated channel subfamily A member 5) has been regarded as a promising target of interventions for atrial fibrillation (AF). SNX17 (sorting nexin 17), a member of the SNXs (sorting nexin family), regulates the intracellular trafficking of membrane proteins through its FERM (four-point-one, ezrin, radixin, moesin) domain. However, whether SNX17 regulates the trafficking process of Kv1.5 remains unknown. METHODS A SNX17 knockout rat line was generated to test the role of SNX17 in atrial electrophysiology. The protein expression of SNX17 and membrane ion channels was detected by Western blotting. Electrophysiology changes in the atrial tissue and myocytes were analyzed by optical mapping and patch clamp, respectively. Acetylcholine and electrical stimulation were used to induce AF, and ECG recording was adopted to assess the influence of SNX17 deficiency on AF susceptibility. The spatial relationship between Kv1.5 and SNX17 was evaluated by immunostaining and confocal scanning, and the functional region of SNX17 regulating Kv1.5 trafficking was identified using plasmids with truncated SNX17 domains. RESULTS Embryonic death occurred in homozygous SNX17 knockout rats. SNX17 heterozygous rats survived, and the level of the SNX17 protein in the atrium was decreased by ≈50%. SNX17 deficiency increased the membrane expression of Kv1.5 and atria-specific ultrarapid delayed rectifier outward potassium current ( IKur) density, resulting in a shortened action potential duration, and eventually contributing to AF susceptibility. Mechanistically, SNX17 facilitated the endocytic sorting of Kv1.5 from the plasma membrane to early endosomes via the FERM domain. CONCLUSIONS SNX17 mediates susceptibility to AF by regulating endocytic sorting of the Kv1.5 channel through the FERM domain. SNX17 could be a potential target for the development of new drugs for AF.
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Affiliation(s)
- Li Geng
- Key Laboratory of Arrhythmias of the Ministry of Education of East Hospital (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China.,Institute of Medical Genetics (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., L.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China
| | - Shuo Wang
- Key Laboratory of Arrhythmias of the Ministry of Education of East Hospital (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China.,Institute of Medical Genetics (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., L.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China
| | - Fulei Zhang
- Key Laboratory of Arrhythmias of the Ministry of Education of East Hospital (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China.,Institute of Medical Genetics (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., L.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China
| | - Ke Xiong
- Key Laboratory of Arrhythmias of the Ministry of Education of East Hospital (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China.,Institute of Medical Genetics (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., L.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China
| | - Jian Huang
- Key Laboratory of Arrhythmias of the Ministry of Education of East Hospital (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China.,Institute of Medical Genetics (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., L.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China
| | - Tingting Zhao
- Key Laboratory of Arrhythmias of the Ministry of Education of East Hospital (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China.,Institute of Medical Genetics (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., L.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China
| | - Dan Shi
- Key Laboratory of Arrhythmias of the Ministry of Education of East Hospital (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China.,Institute of Medical Genetics (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., L.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China
| | - Fei Lv
- Key Laboratory of Arrhythmias of the Ministry of Education of East Hospital (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China.,Institute of Medical Genetics (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., L.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China
| | - Li Li
- Institute of Medical Genetics (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., L.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China
| | - Dandan Liang
- Key Laboratory of Arrhythmias of the Ministry of Education of East Hospital (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China.,Institute of Medical Genetics (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., L.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China
| | - Yingyu Cui
- Key Laboratory of Arrhythmias of the Ministry of Education of East Hospital (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China.,Institute of Medical Genetics (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., L.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China
| | - Yi Liu
- Key Laboratory of Arrhythmias of the Ministry of Education of East Hospital (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China.,Institute of Medical Genetics (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., L.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China
| | - Duanyang Xie
- Key Laboratory of Arrhythmias of the Ministry of Education of East Hospital (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China.,Institute of Medical Genetics (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., L.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China.,School of Life Science and Technology (D.X.), Tongji University, Shanghai, China
| | - Yi-Han Chen
- Key Laboratory of Arrhythmias of the Ministry of Education of East Hospital (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China.,Institute of Medical Genetics (L.G., S.W., F.Z., K.X., J.H., T.Z., D.S., F.L., L.L., D.L., Y.C., Y.L., D.X., Y.-H.C.), Tongji University, Shanghai, China
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7
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Mechanism of electrical remodeling of atrial myocytes and its influence on susceptibility to atrial fibrillation in diabetic rats. Life Sci 2019; 239:116903. [PMID: 31639397 DOI: 10.1016/j.lfs.2019.116903] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Revised: 09/14/2019] [Accepted: 09/22/2019] [Indexed: 02/06/2023]
Abstract
AIMS To explore the atrial electrical remodeling and the susceptibility of atrial fibrillation (AF) in diabetic rats. MATERIALS AND METHODS Zucker diabetic fatty (ZDF) rats were chosen as diabetic animal model, and age-matched non-diabetic littermate Zucker lean (ZL) rats as control. AF susceptibility was determined by electrophysiological examination. The current density of Ito, IKur and ICa-L were detected by whole-cell patch-clamp technique, and ion channel protein expression in atrial tissue and HL-1 cells treated with advanced glycation end products (AGE) was analyzed by western blotting. KEY FINDINGS Diabetic rats had significantly enlarged left atria and evenly thickened ventricular walls, hypertrophied cells and interstitial fibrosis in atrial myocardium, increased AF susceptibility, and prolonged AF duration after atrial burst stimulation. Compared with atrial myocytes isolated from ZL controls, atrial myocytes isolated from ZDF rats had prolonged action potential duration, decreased absolute value of resting membrane potential level and current densities of Ito, IKur and ICa-L. The ion channel protein (Kv4.3, Kv1.5 and Cav1.2) expression in atrium tissue of ZDF rats and HL-1 cells treated with high concentration AGE were significantly down-regulated, compared with controls. SIGNIFICANCE The atrial electrical remodeling induced by hyperglycemia contributed to the increased AF susceptibility in diabetic rats.
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8
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Sengupta S, Rothenberg KE, Li H, Hoffman BD, Bursac N. Altering integrin engagement regulates membrane localization of K ir2.1 channels. J Cell Sci 2019; 132:jcs225383. [PMID: 31391240 PMCID: PMC6771140 DOI: 10.1242/jcs.225383] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Accepted: 07/31/2019] [Indexed: 12/26/2022] Open
Abstract
How ion channels localize and distribute on the cell membrane remains incompletely understood. We show that interventions that vary cell adhesion proteins and cell size also affect the membrane current density of inward-rectifier K+ channels (Kir2.1; encoded by KCNJ2) and profoundly alter the action potential shape of excitable cells. By using micropatterning to manipulate the localization and size of focal adhesions (FAs) in single HEK293 cells engineered to stably express Kir2.1 channels or in neonatal rat cardiomyocytes, we establish a robust linear correlation between FA coverage and the amplitude of Kir2.1 current at both the local and whole-cell levels. Confocal microscopy showed that Kir2.1 channels accumulate in membrane proximal to FAs. Selective pharmacological inhibition of key mediators of protein trafficking and the spatially dependent alterations in the dynamics of Kir2.1 fluorescent recovery after photobleaching revealed that the Kir2.1 channels are transported to the cell membrane uniformly, but are preferentially internalized by endocytosis at sites that are distal from FAs. Based on these results, we propose adhesion-regulated membrane localization of ion channels as a fundamental mechanism of controlling cellular electrophysiology via mechanochemical signals, independent of the direct ion channel mechanogating.
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Affiliation(s)
- Swarnali Sengupta
- Department of Biomedical Engineering, Duke University, Durham, NC 27708, USA
| | | | - Hanjun Li
- Department of Biomedical Engineering, Duke University, Durham, NC 27708, USA
| | - Brenton D Hoffman
- Department of Biomedical Engineering, Duke University, Durham, NC 27708, USA
| | - Nenad Bursac
- Department of Biomedical Engineering, Duke University, Durham, NC 27708, USA
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9
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Ryland KE, Svoboda LK, Vesely ED, McIntyre JC, Zhang L, Martens JR, Lawlor ER. Polycomb-dependent repression of the potassium channel-encoding gene KCNA5 promotes cancer cell survival under conditions of stress. Oncogene 2014; 34:4591-600. [PMID: 25435365 PMCID: PMC4451446 DOI: 10.1038/onc.2014.384] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2014] [Revised: 09/23/2014] [Accepted: 10/10/2014] [Indexed: 02/08/2023]
Abstract
Relapse after clinical remission remains a leading cause of cancer-associated death. Although the mechanisms of tumor relapse are complex, the ability of cancer cells to survive physiological stress is a prerequisite for recurrence. Ewing sarcoma (ES) and neuroblastoma (NB) are aggressive cancers that frequently relapse after initial remission. In addition, both tumors overexpress the polycomb group (PcG) proteins BMI-1 and EZH2, which contribute to tumorigenicity. We have discovered that ES and NB resist hypoxic stress-induced death and that survival depends on PcG function. Epigenetic repression of developmental programs is the most well-established cancer-associated function of PcG proteins. However, we noted that voltage-gated potassium (Kv) channel genes are also targets of PcG regulation in stem cells. Given the role of potassium in regulating apoptosis, we reasoned that repression of Kv channel genes might have a role in cancer cell survival. Here we describe our novel finding that PcG-dependent repression of the Kv1.5 channel gene KCNA5 contributes to cancer cell survival under conditions of stress. We show that survival of cancer cells in stress is dependent upon suppression of Kv1.5 channel function. The KCNA5 promoter is marked in cancer cells with PcG-dependent chromatin repressive modifications that increase in hypoxia. Genetic and pharmacological inhibition of BMI-1 and EZH2, respectively, restore KCNA5 expression, which sensitizes cells to stress-induced death. In addition, ectopic expression of the Kv1.5 channel induces apoptotic cell death under conditions of hypoxia. These findings identify a novel role for PcG proteins in promoting cancer cell survival via repression of KCNA5.
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Affiliation(s)
- K E Ryland
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA.,Translational Oncology Program, Department of Pediatrics and Communicable Diseases, University of Michigan, Ann Arbor, MI, USA
| | - L K Svoboda
- Translational Oncology Program, Department of Pediatrics and Communicable Diseases, University of Michigan, Ann Arbor, MI, USA
| | - E D Vesely
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA
| | - J C McIntyre
- Department of Pharmacology and Therapeutics, College of Medicine, University of Florida, Gainesville, FL, USA
| | - L Zhang
- Department of Pharmacology and Therapeutics, College of Medicine, University of Florida, Gainesville, FL, USA
| | - J R Martens
- Department of Pharmacology and Therapeutics, College of Medicine, University of Florida, Gainesville, FL, USA
| | - E R Lawlor
- Translational Oncology Program, Department of Pediatrics and Communicable Diseases, University of Michigan, Ann Arbor, MI, USA.,Department of Pathology, University of Michigan, Ann Arbor, MI, USA
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10
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Functional interaction with filamin A and intracellular Ca2+ enhance the surface membrane expression of a small-conductance Ca2+-activated K+ (SK2) channel. Proc Natl Acad Sci U S A 2014; 111:9989-94. [PMID: 24951510 DOI: 10.1073/pnas.1323541111] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
For an excitable cell to function properly, a precise number of ion channel proteins need to be trafficked to distinct locations on the cell surface membrane, through a network and anchoring activity of cytoskeletal proteins. Not surprisingly, mutations in anchoring proteins have profound effects on membrane excitability. Ca(2+)-activated K(+) channels (KCa2 or SK) have been shown to play critical roles in shaping the cardiac atrial action potential profile. Here, we demonstrate that filamin A, a cytoskeletal protein, augments the trafficking of SK2 channels in cardiac myocytes. The trafficking of SK2 channel is Ca(2+)-dependent. Further, the Ca(2+) dependence relies on another channel-interacting protein, α-actinin2, revealing a tight, yet intriguing, assembly of cytoskeletal proteins that orchestrate membrane expression of SK2 channels in cardiac myocytes. We assert that changes in SK channel trafficking would significantly alter atrial action potential and consequently atrial excitability. Identification of therapeutic targets to manipulate the subcellular localization of SK channels is likely to be clinically efficacious. The findings here may transcend the area of SK2 channel studies and may have implications not only in cardiac myocytes but in other types of excitable cells.
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11
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Ding WG, Xie Y, Toyoda F, Matsuura H. Improved functional expression of human cardiac kv1.5 channels and trafficking-defective mutants by low temperature treatment. PLoS One 2014; 9:e92923. [PMID: 24663680 PMCID: PMC3963980 DOI: 10.1371/journal.pone.0092923] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Accepted: 02/26/2014] [Indexed: 11/18/2022] Open
Abstract
We herein investigated the effect of low temperature exposure on the expression, degradation, localization and activity of human Kv1.5 (hKv1.5). In hKv1.5-expressing CHO cells, the currents were significantly increased when cultured at a reduced temperature (28°C) compared to those observed at 37°C. Western blot analysis indicated that the protein levels (both immature and mature proteins) of hKv1.5 were significantly elevated under the hypothermic condition. Treatment with a proteasome inhibitor, MG132, significantly increased the immature, but not the mature, hKv1.5 protein at 37°C, however, there were no changes in either the immature or mature hKv1.5 proteins at low temperature following MG132 exposure. These observations suggest that the enhancement of the mature hKv1.5 protein at reduced temperature may not result from the inhibition of proteolysis. Moreover, the hKv1.5 fluorescence signal in the cells increased significantly on the cell surface at 28°C versus those cultured at 37°C. Importantly, the low temperature treatment markedly shifted the subcellular distribution of the mature hKv1.5, which showed considerable overlap with the trans-Golgi component. Experiments using tunicamycin, an inhibitor of N-glycosylation, indicated that the N-glycosylation of hKv1.5 is more effective at 28°C than at 37°C. Finally, the hypothermic treatment also rescued the protein expression and currents of trafficking-defective hKv1.5 mutants. These results indicate that low temperature exposure stabilizes the protein in the cellular organelles or on the plasma membrane, and modulates its maturation and trafficking, thus enhancing the currents of hKv1.5 and its trafficking defect mutants.
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Affiliation(s)
- Wei-Guang Ding
- Department of Physiology, Shiga University of Medical Science, Otsu, Shiga, Japan
- * E-mail:
| | - Yu Xie
- Department of Physiology, Shiga University of Medical Science, Otsu, Shiga, Japan
| | - Futoshi Toyoda
- Department of Physiology, Shiga University of Medical Science, Otsu, Shiga, Japan
| | - Hiroshi Matsuura
- Department of Physiology, Shiga University of Medical Science, Otsu, Shiga, Japan
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12
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Shear stress triggers insertion of voltage-gated potassium channels from intracellular compartments in atrial myocytes. Proc Natl Acad Sci U S A 2013; 110:E3955-64. [PMID: 24065831 DOI: 10.1073/pnas.1309896110] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Atrial myocytes are continuously exposed to mechanical forces including shear stress. However, in atrial myocytes, the effects of shear stress are poorly understood, particularly with respect to its effect on ion channel function. Here, we report that shear stress activated a large outward current from rat atrial myocytes, with a parallel decrease in action potential duration. The main ion channel underlying the increase in current was found to be Kv1.5, the recruitment of which could be directly observed by total internal reflection fluorescence microscopy, in response to shear stress. The effect was primarily attributable to recruitment of intracellular pools of Kv1.5 to the sarcolemma, as the response was prevented by the SNARE protein inhibitor N-ethylmaleimide and the calcium chelator BAPTA. The process required integrin signaling through focal adhesion kinase and relied on an intact microtubule system. Furthermore, in a rat model of chronic hemodynamic overload, myocytes showed an increase in basal current despite a decrease in Kv1.5 protein expression, with a reduced response to shear stress. Additionally, integrin beta1d expression and focal adhesion kinase activation were increased in this model. This data suggests that, under conditions of chronically increased mechanical stress, the integrin signaling pathway is overactivated, leading to increased functional Kv1.5 at the membrane and reducing the capacity of cells to further respond to mechanical challenge. Thus, pools of Kv1.5 may comprise an inducible reservoir that can facilitate the repolarization of the atrium under conditions of excessive mechanical stress.
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13
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Balut CM, Hamilton KL, Devor DC. Trafficking of intermediate (KCa3.1) and small (KCa2.x) conductance, Ca(2+)-activated K(+) channels: a novel target for medicinal chemistry efforts? ChemMedChem 2012; 7:1741-55. [PMID: 22887933 DOI: 10.1002/cmdc.201200226] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Revised: 07/09/2012] [Indexed: 12/22/2022]
Abstract
Ca(2+)-activated K(+) (KCa) channels play a pivotal role in the physiology of a wide variety of tissues and disease states, including vascular endothelia, secretory epithelia, certain cancers, red blood cells (RBC), neurons, and immune cells. Such widespread involvement has generated an intense interest in elucidating the function and regulation of these channels, with the goal of developing pharmacological strategies aimed at selective modulation of KCa channels in various disease states. Herein we give an overview of the molecular and functional properties of these channels and their therapeutic importance. We discuss the achievements made in designing pharmacological tools that control the function of KCa channels by modulating their gating properties. Moreover, this review discusses the recent advances in our understanding of KCa channel assembly and anterograde trafficking toward the plasma membrane, the micro-domains in which these channels are expressed within the cell, and finally the retrograde trafficking routes these channels take following endocytosis. As the regulation of intracellular trafficking by agonists as well as the protein-protein interactions that modify these events continue to be explored, we anticipate this will open new therapeutic avenues for the targeting of these channels based on the pharmacological modulation of KCa channel density at the plasma membrane.
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Affiliation(s)
- Corina M Balut
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA
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14
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Abstract
Atrial fibrillation is the most common type of cardiac arrhythmia, and is responsible for substantial morbidity and mortality in the general population. Current treatments have moderate efficacy and considerable risks, especially of pro-arrhythmia, highlighting the need for new therapeutic strategies. In recent years, substantial efforts have been invested in developing novel treatments that target the underlying molecular determinants of atrial fibrillation, and several new compounds are under development. This Review focuses on the mechanistic rationale for the development of new anti-atrial fibrillation drugs, on the molecular and structural motifs that they target and on the results obtained so far in experimental and clinical studies.
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15
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Sánchez C, Corrias A, Bueno-Orovio A, Davies M, Swinton J, Jacobson I, Laguna P, Pueyo E, Rodríguez B. The Na+/K+ pump is an important modulator of refractoriness and rotor dynamics in human atrial tissue. Am J Physiol Heart Circ Physiol 2012; 302:H1146-59. [PMID: 22198174 PMCID: PMC3311461 DOI: 10.1152/ajpheart.00668.2011] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Accepted: 12/04/2011] [Indexed: 11/22/2022]
Abstract
Pharmacological treatment of atrial fibrillation (AF) exhibits limited efficacy. Further developments require a comprehensive characterization of ionic modulators of electrophysiology in human atria. Our aim is to systematically investigate the relative importance of ionic properties in modulating excitability, refractoriness, and rotor dynamics in human atria before and after AF-related electrical remodeling (AFER). Computer simulations of single cell and tissue atrial electrophysiology were conducted using two human atrial action potential (AP) models. Changes in AP, refractory period (RP), conduction velocity (CV), and rotor dynamics caused by alterations in key properties of all atrial ionic currents were characterized before and after AFER. Results show that the investigated human atrial electrophysiological properties are primarily modulated by maximal value of Na(+)/K(+) pump current (G(NaK)) as well as conductances of inward rectifier potassium current (G(K1)) and fast inward sodium current (G(Na)). G(NaK) plays a fundamental role through both electrogenic and homeostatic modulation of AP duration (APD), APD restitution, RP, and reentrant dominant frequency (DF). G(K1) controls DF through modulation of AP, APD restitution, RP, and CV. G(Na) is key in determining DF through alteration of CV and RP, particularly in AFER. Changes in ionic currents have qualitatively similar effects in control and AFER, but effects are smaller in AFER. The systematic analysis conducted in this study unravels the important role of the Na(+)/K(+) pump current in determining human atrial electrophysiology.
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Affiliation(s)
- Carlos Sánchez
- Communications Technology Group, I3A and IIS, University of Zaragoza, Zaragoza
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16
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Balut CM, Gao Y, Murray SA, Thibodeau PH, Devor DC. ESCRT-dependent targeting of plasma membrane localized KCa3.1 to the lysosomes. Am J Physiol Cell Physiol 2010; 299:C1015-27. [PMID: 20720181 DOI: 10.1152/ajpcell.00120.2010] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The number of intermediate-conductance, Ca(2+)-activated K(+) channels (KCa3.1) present at the plasma membrane is deterministic in any physiological response. However, the mechanisms by which KCa3.1 channels are removed from the plasma membrane and targeted for degradation are poorly understood. Recently, we demonstrated that KCa3.1 is rapidly internalized from the plasma membrane, having a short half-life in both human embryonic kidney cells (HEK293) and human microvascular endothelial cells (HMEC-1). In this study, we investigate the molecular mechanisms controlling the degradation of KCa3.1 heterologously expressed in HEK and HMEC-1 cells. Using immunofluorescence and electron microscopy, as well as quantitative biochemical analysis, we demonstrate that membrane KCa3.1 is targeted to the lysosomes for degradation. Furthermore, we demonstrate that either overexpressing a dominant negative Rab7 or short interfering RNA-mediated knockdown of Rab7 results in a significant inhibition of channel degradation rate. Coimmunoprecipitation confirmed a close association between Rab7 and KCa3.1. On the basis of these findings, we assessed the role of the ESCRT machinery in the degradation of heterologously expressed KCa3.1, including TSG101 [endosomal sorting complex required for transport (ESCRT)-I] and CHMP4 (ESCRT-III) as well as VPS4, a protein involved in the disassembly of the ESCRT machinery. We demonstrate that TSG101 is closely associated with KCa3.1 via coimmunoprecipitation and that a dominant negative TSG101 inhibits KCa3.1 degradation. In addition, both dominant negative CHMP4 and VPS4 significantly decrease the rate of membrane KCa3.1 degradation, compared with wild-type controls. These results are the first to demonstrate that plasma membrane-associated KCa3.1 is targeted for lysosomal degradation via a Rab7 and ESCRT-dependent pathway.
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Affiliation(s)
- Corina M Balut
- Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, Pennsylvania15261, USA
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