1
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Bahouth SW, Nooh MM, Mancarella S. Involvement of SAP97 anchored multiprotein complexes in regulating cardiorenal signaling and trafficking networks. Biochem Pharmacol 2023; 208:115406. [PMID: 36596415 DOI: 10.1016/j.bcp.2022.115406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 12/26/2022] [Accepted: 12/28/2022] [Indexed: 01/02/2023]
Abstract
SAP97 is a member of the MAGUK family of proteins, but unlike other MAGUK proteins that are selectively expressed in the CNS, SAP97 is also expressed in peripheral organs, like the heart and kidneys. SAP97 has several protein binding cassettes, and this review will describe their involvement in creating SAP97-anchored multiprotein networks. SAP97-anchored networks localized at the inner leaflet of the cell membrane play a major role in trafficking and targeting of membrane G protein-coupled receptors (GPCR), channels, and structural proteins. SAP97 plays a major role in compartmentalizing voltage gated sodium and potassium channels to specific cellular compartments of heart cells. SAP97 undergoes extensive alternative splicing. These splice variants give rise to different SAP97 isoforms that alter its cellular localization, networking, signaling and trafficking effects. Regarding GPCR, SAP97 binds to the β1-adrenergic receptor and recruits AKAP5/PKA and PDE4D8 to create a multiprotein complex that regulates trafficking and signaling of cardiac β1-AR. In the kidneys, SAP97 anchored networks played a role in trafficking of aquaporin-2 water channels. Cardiac specific ablation of SAP97 (SAP97-cKO) resulted in cardiac hypertrophy and failure in aging mice. Similarly, instituting transverse aortic constriction (TAC) in young SAP97 c-KO mice exacerbated TAC-induced cardiac remodeling and dysfunction. These findings highlight a critical role for SAP97 in the pathophysiology of a number of cardiac and renal diseases, suggesting that SAP97 is a relevant target for drug discovery.
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Affiliation(s)
- Suleiman W Bahouth
- Department of Pharmacology, Addiction Science and Toxicology, The University of Tennessee-Health Sciences Center, Memphis, TN, United States.
| | - Mohammed M Nooh
- Department of Biochemistry, Faculty of Pharmacy Cairo University, Cairo, Egypt and Biochemistry Department, Faculty of Pharmacy, October 6 University, Giza, Egypt
| | - Salvatore Mancarella
- Department of Physiology, The University of Tennessee-Health Sciences Center, Memphis, TN, United States
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2
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Daimi H, Lozano-Velasco E, Aranega A, Franco D. Genomic and Non-Genomic Regulatory Mechanisms of the Cardiac Sodium Channel in Cardiac Arrhythmias. Int J Mol Sci 2022; 23:1381. [PMID: 35163304 PMCID: PMC8835759 DOI: 10.3390/ijms23031381] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 12/30/2021] [Accepted: 01/06/2022] [Indexed: 12/19/2022] Open
Abstract
Nav1.5 is the predominant cardiac sodium channel subtype, encoded by the SCN5A gene, which is involved in the initiation and conduction of action potentials throughout the heart. Along its biosynthesis process, Nav1.5 undergoes strict genomic and non-genomic regulatory and quality control steps that allow only newly synthesized channels to reach their final membrane destination and carry out their electrophysiological role. These regulatory pathways are ensured by distinct interacting proteins that accompany the nascent Nav1.5 protein along with different subcellular organelles. Defects on a large number of these pathways have a tremendous impact on Nav1.5 functionality and are thus intimately linked to cardiac arrhythmias. In the present review, we provide current state-of-the-art information on the molecular events that regulate SCN5A/Nav1.5 and the cardiac channelopathies associated with defects in these pathways.
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Affiliation(s)
- Houria Daimi
- Biochemistry and Molecular Biology Laboratory, Faculty of Pharmacy, University of Monastir, Monastir 5000, Tunisia
| | - Estefanía Lozano-Velasco
- Department of Experimental Biology, University of Jaen, 23071 Jaen, Spain; (E.L.-V.); (A.A.); (D.F.)
- Medina Foundation, Technology Park of Health Sciences, Av. del Conocimiento, 34, 18016 Granada, Spain
| | - Amelia Aranega
- Department of Experimental Biology, University of Jaen, 23071 Jaen, Spain; (E.L.-V.); (A.A.); (D.F.)
- Medina Foundation, Technology Park of Health Sciences, Av. del Conocimiento, 34, 18016 Granada, Spain
| | - Diego Franco
- Department of Experimental Biology, University of Jaen, 23071 Jaen, Spain; (E.L.-V.); (A.A.); (D.F.)
- Medina Foundation, Technology Park of Health Sciences, Av. del Conocimiento, 34, 18016 Granada, Spain
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3
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Zhang S, Li X, Liu W, Zhang X, Huang L, Li S, Yang M, Zhao P, Yang J, Fei P, Zhu X, Yang Z. Whole-Exome Sequencing Identified DLG1 as a Candidate Gene for Familial Exudative Vitreoretinopathy. Genet Test Mol Biomarkers 2021; 25:309-316. [PMID: 33945310 DOI: 10.1089/gtmb.2021.0013] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Purpose: Familial exudative vitreoretinopathy (FEVR) is a blinding retinal vascular disease. Clinically, FEVR is characterized by incomplete vascularization of the peripheral retina and pathological neovascularization. Only about 50% of FEVR cases can be explained by known FEVR disease gene variations. This study aimed to identify novel genes associated with the FEVR phenotype and explore their pathogenic mechanisms. Materials and Methods: Exome sequencing analyses were conducted on one Chinese family with FEVR whose affected members did not exhibit pathogenic variants in the known FEVR genes (verified using Sanger sequencing analysis). Functions of the affected proteins were evaluated using reporter assays. Western blot analysis was used to detect mutant protein expression and the genes' pathogenic mechanisms. Results: A rare novel heterozygous variant in DLG1 (c.1792A>G; p.S598G) was identified. The amino acid residues surrounding the identified variant are highly conserved among vertebrates. A luciferase reporter assay revealed that the mutant DLG1 protein DLG1-S598G lost its ability to activate Wnt signaling. Moreover, a knockdown (KD) of DLG1 in human primary retinal endothelial cells impaired tube formation. Mechanistically, DLG1 KD led to a reduction in phosphorylated VEGFR2, an essential receptor for the angiogenic potency that signals the vascular endothelial growth factor molecule. Conclusions: The data reported here demonstrate that DLG1 is a novel candidate gene for FEVR.
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Affiliation(s)
- Shanshan Zhang
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Prenatal Diagnosis Center, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China.,Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, China
| | - Xiao Li
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Prenatal Diagnosis Center, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China.,Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, China
| | - Wenjing Liu
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Prenatal Diagnosis Center, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China.,Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, China
| | - Xiang Zhang
- Department of Ophthalmology, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Lulin Huang
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Prenatal Diagnosis Center, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China.,Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, China
| | - Shujin Li
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Prenatal Diagnosis Center, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China.,Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, China.,Chengdu Institute of Biology, Sichuan Translational Medicine Research Hospital, Chinese Academy of Sciences, Chengdu, China
| | - Mu Yang
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Prenatal Diagnosis Center, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China.,Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, China.,Chengdu Institute of Biology, Sichuan Translational Medicine Research Hospital, Chinese Academy of Sciences, Chengdu, China
| | - Peiquan Zhao
- Department of Ophthalmology, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jiyun Yang
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Prenatal Diagnosis Center, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China.,Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, China
| | - Ping Fei
- Department of Ophthalmology, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xianjun Zhu
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Prenatal Diagnosis Center, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China.,Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, China.,Chengdu Institute of Biology, Sichuan Translational Medicine Research Hospital, Chinese Academy of Sciences, Chengdu, China
| | - Zhenglin Yang
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Prenatal Diagnosis Center, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China.,Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, China.,Chengdu Institute of Biology, Sichuan Translational Medicine Research Hospital, Chinese Academy of Sciences, Chengdu, China
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4
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Tinaquero D, Crespo-García T, Utrilla RG, Nieto-Marín P, González-Guerra A, Rubio-Alarcón M, Cámara-Checa A, Dago M, Matamoros M, Pérez-Hernández M, Tamargo M, Cebrián J, Jalife J, Tamargo J, Bernal JA, Caballero R, Delpón E. The p.P888L SAP97 polymorphism increases the transient outward current (I to,f) and abbreviates the action potential duration and the QT interval. Sci Rep 2020; 10:10707. [PMID: 32612162 PMCID: PMC7329876 DOI: 10.1038/s41598-020-67109-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Accepted: 06/01/2020] [Indexed: 11/09/2022] Open
Abstract
Synapse-Associated Protein 97 (SAP97) is an anchoring protein that in cardiomyocytes targets to the membrane and regulates Na+ and K+ channels. Here we compared the electrophysiological effects of native (WT) and p.P888L SAP97, a common polymorphism. Currents were recorded in cardiomyocytes from mice trans-expressing human WT or p.P888L SAP97 and in Chinese hamster ovary (CHO)-transfected cells. The duration of the action potentials and the QT interval were significantly shorter in p.P888L-SAP97 than in WT-SAP97 mice. Compared to WT, p.P888L SAP97 significantly increased the charge of the Ca-independent transient outward (Ito,f) current in cardiomyocytes and the charge crossing Kv4.3 channels in CHO cells by slowing Kv4.3 inactivation kinetics. Silencing or inhibiting Ca/calmodulin kinase II (CaMKII) abolished the p.P888L-induced Kv4.3 charge increase, which was also precluded in channels (p.S550A Kv4.3) in which the CaMKII-phosphorylation is prevented. Computational protein-protein docking predicted that p.P888L SAP97 is more likely to form a complex with CaMKII than WT. The Na+ current and the current generated by Kv1.5 channels increased similarly in WT-SAP97 and p.P888L-SAP97 cardiomyocytes, while the inward rectifier current increased in WT-SAP97 but not in p.P888L-SAP97 cardiomyocytes. The p.P888L SAP97 polymorphism increases the Ito,f, a CaMKII-dependent effect that may increase the risk of arrhythmias.
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Affiliation(s)
- David Tinaquero
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | - Teresa Crespo-García
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | - Raquel G Utrilla
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | - Paloma Nieto-Marín
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | | | - Marcos Rubio-Alarcón
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | - Anabel Cámara-Checa
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | - María Dago
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | - Marcos Matamoros
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | - Marta Pérez-Hernández
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | - María Tamargo
- Cardiology Department, Hospital General Universitario Gregorio Marañón, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | - Jorge Cebrián
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | - José Jalife
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain.,Department of Internal Medicine/Cardiovascular Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Juan Tamargo
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | | | - Ricardo Caballero
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain.
| | - Eva Delpón
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
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5
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Musa H, Marcou CA, Herron TJ, Makara MA, Tester DJ, O'Connell RP, Rosinski B, Guerrero-Serna G, Milstein ML, Monteiro da Rocha A, Ye D, Crotti L, Nesterenko VV, Castelletti S, Torchio M, Kotta MC, Dagradi F, Antzelevitch C, Mohler PJ, Schwartz PJ, Ackerman MJ, Anumonwo JM. Abnormal myocardial expression of SAP97 is associated with arrhythmogenic risk. Am J Physiol Heart Circ Physiol 2020; 318:H1357-H1370. [PMID: 32196358 DOI: 10.1152/ajpheart.00481.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Synapse-associated protein 97 (SAP97) is a scaffolding protein crucial for the functional expression of several cardiac ion channels and therefore proper cardiac excitability. Alterations in the functional expression of SAP97 can modify the ionic currents underlying the cardiac action potential and consequently confer susceptibility for arrhythmogenesis. In this study, we generated a murine model for inducible, cardiac-targeted Sap97 ablation to investigate arrhythmia susceptibility and the underlying molecular mechanisms. Furthermore, we sought to identify human SAP97 (DLG1) variants that were associated with inherited arrhythmogenic disease. The murine model of cardiac-specific Sap97 ablation demonstrated several ECG abnormalities, pronounced action potential prolongation subject to high incidence of arrhythmogenic afterdepolarizations and notable alterations in the activity of the main cardiac ion channels. However, no DLG1 mutations were found in 40 unrelated cases of genetically elusive long QT syndrome (LQTS). Instead, we provide the first evidence implicating a gain of function in human DLG1 mutation resulting in an increase in Kv4.3 current (Ito) as a novel, potentially pathogenic substrate for Brugada syndrome (BrS). In conclusion, DLG1 joins a growing list of genes encoding ion channel interacting proteins (ChIPs) identified as potential channelopathy-susceptibility genes because of their ability to regulate the trafficking, targeting, and modulation of ion channels that are critical for the generation and propagation of the cardiac electrical impulse. Dysfunction in these critical components of cardiac excitability can potentially result in fatal cardiac disease.NEW & NOTEWORTHY The gene encoding SAP97 (DLG1) joins a growing list of genes encoding ion channel-interacting proteins (ChIPs) identified as potential channelopathy-susceptibility genes because of their ability to regulate the trafficking, targeting, and modulation of ion channels that are critical for the generation and propagation of the cardiac electrical impulse. In this study we provide the first data supporting DLG1-encoded SAP97's candidacy as a minor Brugada syndrome susceptibility gene.
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Affiliation(s)
- Hassan Musa
- Departments of Internal Medicine and of Physiology and Cell Biology, Dorothy M. Davis Heart and Lung Research Institute, Wexner Medical Center, The Ohio State University, Columbus, Ohio.,Departments of Internal Medicine (Cardiovascular) and of Molecular and Integrative Physiology, Center for Arrhythmia Research, University of Michigan, Ann Arbor, Michigan
| | - Cherisse A Marcou
- Division of Heart Rhythm Services, Department of Cardiovascular Diseases; Division of Pediatric Cardiology, Department of Pediatrics; and Department of Molecular Pharmacology and Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minnesota
| | - Todd J Herron
- Departments of Internal Medicine and of Physiology and Cell Biology, Dorothy M. Davis Heart and Lung Research Institute, Wexner Medical Center, The Ohio State University, Columbus, Ohio.,Departments of Internal Medicine (Cardiovascular) and of Molecular and Integrative Physiology, Center for Arrhythmia Research, University of Michigan, Ann Arbor, Michigan.,Cardiovascular Regeneration Core Laboratory, Frankel Cardiovascular Center, University of Michigan, Ann Arbor, Michigan
| | - Michael A Makara
- Departments of Internal Medicine and of Physiology and Cell Biology, Dorothy M. Davis Heart and Lung Research Institute, Wexner Medical Center, The Ohio State University, Columbus, Ohio
| | - David J Tester
- Division of Heart Rhythm Services, Department of Cardiovascular Diseases; Division of Pediatric Cardiology, Department of Pediatrics; and Department of Molecular Pharmacology and Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minnesota
| | - Ryan P O'Connell
- Departments of Internal Medicine (Cardiovascular) and of Molecular and Integrative Physiology, Center for Arrhythmia Research, University of Michigan, Ann Arbor, Michigan
| | - Brad Rosinski
- Departments of Internal Medicine (Cardiovascular) and of Molecular and Integrative Physiology, Center for Arrhythmia Research, University of Michigan, Ann Arbor, Michigan
| | - Guadalupe Guerrero-Serna
- Departments of Internal Medicine (Cardiovascular) and of Molecular and Integrative Physiology, Center for Arrhythmia Research, University of Michigan, Ann Arbor, Michigan
| | - Michelle L Milstein
- Departments of Internal Medicine (Cardiovascular) and of Molecular and Integrative Physiology, Center for Arrhythmia Research, University of Michigan, Ann Arbor, Michigan
| | - André Monteiro da Rocha
- Departments of Internal Medicine (Cardiovascular) and of Molecular and Integrative Physiology, Center for Arrhythmia Research, University of Michigan, Ann Arbor, Michigan.,Cardiovascular Regeneration Core Laboratory, Frankel Cardiovascular Center, University of Michigan, Ann Arbor, Michigan
| | - Dan Ye
- Division of Heart Rhythm Services, Department of Cardiovascular Diseases; Division of Pediatric Cardiology, Department of Pediatrics; and Department of Molecular Pharmacology and Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minnesota
| | - Lia Crotti
- Department of Molecular Medicine, University of Pavia, Pavia, Italy.,IRCCS Istituto Auxologico Italiano, San Luca Hospital, Milan, Italy.,IRCCS Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, Milan, Italy
| | | | - Silvia Castelletti
- IRCCS Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, Milan, Italy
| | - Margherita Torchio
- Department of Molecular Medicine, University of Pavia, Pavia, Italy.,IRCCS Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, Milan, Italy
| | - Maria-Christina Kotta
- Department of Molecular Medicine, University of Pavia, Pavia, Italy.,IRCCS Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, Milan, Italy
| | - Federica Dagradi
- IRCCS Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, Milan, Italy
| | | | - Peter J Mohler
- Departments of Internal Medicine and of Physiology and Cell Biology, Dorothy M. Davis Heart and Lung Research Institute, Wexner Medical Center, The Ohio State University, Columbus, Ohio.,Division of Cardiovascular Medicine, Department of Internal Medicine, The Ohio State University College of Medicine and Wexner Medical Center, Columbus, Ohio
| | - Peter J Schwartz
- IRCCS Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, Milan, Italy
| | - Michael J Ackerman
- Division of Heart Rhythm Services, Department of Cardiovascular Diseases; Division of Pediatric Cardiology, Department of Pediatrics; and Department of Molecular Pharmacology and Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minnesota
| | - Justus M Anumonwo
- Departments of Internal Medicine (Cardiovascular) and of Molecular and Integrative Physiology, Center for Arrhythmia Research, University of Michigan, Ann Arbor, Michigan
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6
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Abstract
Activation of the electrical signal and its transmission as a depolarizing wave in the whole heart requires highly organized myocyte architecture and cell-cell contacts. In addition, complex trafficking and anchoring intracellular machineries regulate the proper surface expression of channels and their targeting to distinct membrane domains. An increasing list of proteins, lipids, and second messengers can contribute to the normal targeting of ion channels in cardiac myocytes. However, their precise roles in the electrophysiology of the heart are far from been extensively understood. Nowadays, much effort in the field focuses on understanding the mechanisms that regulate ion channel targeting to sarcolemma microdomains and their organization into macromolecular complexes. The purpose of the present section is to provide an overview of the characterized partners of the main cardiac sodium channel, NaV1.5, involved in regulating the functional expression of this channel both in terms of trafficking and targeting into microdomains.
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7
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Eichel CA, Beuriot A, Chevalier MYE, Rougier JS, Louault F, Dilanian G, Amour J, Coulombe A, Abriel H, Hatem SN, Balse E. Lateral Membrane-Specific MAGUK CASK Down-Regulates NaV1.5 Channel in Cardiac Myocytes. Circ Res 2016; 119:544-56. [PMID: 27364017 DOI: 10.1161/circresaha.116.309254] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 06/30/2016] [Indexed: 12/24/2022]
Abstract
RATIONALE Mechanisms underlying membrane protein localization are crucial in the proper function of cardiac myocytes. The main cardiac sodium channel, NaV1.5, carries the sodium current (INa) that provides a rapid depolarizing current during the upstroke of the action potential. Although enriched in the intercalated disc, NaV1.5 is present in different membrane domains in myocytes and interacts with several partners. OBJECTIVE To test the hypothesis that the MAGUK (membrane-associated guanylate kinase) protein CASK (calcium/calmodulin-dependent serine protein kinase) interacts with and regulates NaV1.5 in cardiac myocytes. METHODS AND RESULTS Immunostaining experiments showed that CASK localizes at lateral membranes of cardiac myocytes, in association with dystrophin. Whole-cell patch clamp showed that CASK-silencing increases INa in vitro. In vivo CASK knockdown similarly increased INa recorded in freshly isolated myocytes. Pull-down experiments revealed that CASK directly interacts with the C-terminus of NaV1.5. CASK silencing reduces syntrophin expression without affecting NaV1.5 and dystrophin expression levels. Total Internal Reflection Fluorescence microscopy and biotinylation assays showed that CASK silencing increased the surface expression of NaV1.5 without changing mRNA levels. Quantification of NaV1.5 expression at the lateral membrane and intercalated disc revealed that the lateral membrane pool only was increased upon CASK silencing. The protein transport inhibitor brefeldin-A prevented INa increase in CASK-silenced myocytes. During atrial dilation/remodeling, CASK expression was reduced but its localization remained unchanged. CONCLUSION This study constitutes the first description of an unconventional MAGUK protein, CASK, which directly interacts with NaV1.5 channel and controls its surface expression at the lateral membrane by regulating ion channel trafficking.
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Affiliation(s)
- Catherine A Eichel
- From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.)
| | - Adeline Beuriot
- From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.)
| | - Morgan Y E Chevalier
- From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.)
| | - Jean-Sébastien Rougier
- From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.)
| | - Florent Louault
- From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.)
| | - Gilles Dilanian
- From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.)
| | - Julien Amour
- From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.)
| | - Alain Coulombe
- From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.)
| | - Hugues Abriel
- From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.)
| | - Stéphane N Hatem
- From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.)
| | - Elise Balse
- From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.).
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8
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Ohya S, Kito H, Hatano N, Muraki K. Recent advances in therapeutic strategies that focus on the regulation of ion channel expression. Pharmacol Ther 2016; 160:11-43. [PMID: 26896566 DOI: 10.1016/j.pharmthera.2016.02.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
A number of different ion channel types are involved in cell signaling networks, and homeostatic regulatory mechanisms contribute to the control of ion channel expression. Profiling of global gene expression using microarray technology has recently provided novel insights into the molecular mechanisms underlying the homeostatic and pathological control of ion channel expression. It has demonstrated that the dysregulation of ion channel expression is associated with the pathogenesis of neural, cardiovascular, and immune diseases as well as cancers. In addition to the transcriptional, translational, and post-translational regulation of ion channels, potentially important evidence on the mechanisms controlling ion channel expression has recently been accumulated. The regulation of alternative pre-mRNA splicing is therefore a novel therapeutic strategy for the treatment of dominant-negative splicing disorders. Epigenetic modification plays a key role in various pathological conditions through the regulation of pluripotency genes. Inhibitors of pre-mRNA splicing and histone deacetyalase/methyltransferase have potential as potent therapeutic drugs for cancers and autoimmune and inflammatory diseases. Moreover, membrane-anchoring proteins, lysosomal and proteasomal degradation-related molecules, auxiliary subunits, and pharmacological agents alter the protein folding, membrane trafficking, and post-translational modifications of ion channels, and are linked to expression-defect channelopathies. In this review, we focused on recent insights into the transcriptional, spliceosomal, epigenetic, and proteasomal regulation of ion channel expression: Ca(2+) channels (TRPC/TRPV/TRPM/TRPA/Orai), K(+) channels (voltage-gated, KV/Ca(2+)-activated, KCa/two-pore domain, K2P/inward-rectifier, Kir), and Ca(2+)-activated Cl(-) channels (TMEM16A/TMEM16B). Furthermore, this review highlights expression of these ion channels in expression-defect channelopathies.
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Affiliation(s)
- Susumu Ohya
- Department of Pharmacology, Division of Pathological Sciences, Kyoto Pharmaceutical University, Kyoto 607-8414, Japan.
| | - Hiroaki Kito
- Department of Pharmacology, Division of Pathological Sciences, Kyoto Pharmaceutical University, Kyoto 607-8414, Japan
| | - Noriyuki Hatano
- Laboratory of Cellular Pharmacology, School of Pharmacy, Aichi-Gakuin University, Nagoya 464-8650, Japan
| | - Katsuhiko Muraki
- Laboratory of Cellular Pharmacology, School of Pharmacy, Aichi-Gakuin University, Nagoya 464-8650, Japan.
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9
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Silva O, Crocetti J, Humphries LA, Burkhardt JK, Miceli MC. Discs Large Homolog 1 Splice Variants Regulate p38-Dependent and -Independent Effector Functions in CD8+ T Cells. PLoS One 2015; 10:e0133353. [PMID: 26186728 PMCID: PMC4505885 DOI: 10.1371/journal.pone.0133353] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Accepted: 06/02/2015] [Indexed: 11/22/2022] Open
Abstract
Functionally diverse CD8+ T cells develop in response to antigenic stimulation with differing capacities to couple TCR engagement to downstream signals and functions. However, mechanisms of diversifying TCR signaling are largely uncharacterized. Here we identified two alternative splice variants of scaffold protein Dlg1, Dlg1AB and Dlg1B, that diversify signaling to regulate p38 –dependent and –independent effector functions in CD8+ T cells. Dlg1AB, but not Dlg1B associated with Lck, coupling TCR stimulation to p38 activation and proinflammatory cytokine production. Conversely, both Dlg1AB and Dlg1B mediated p38-independent degranulation. Degranulation depended on a Dlg1 fragment containing an intact Dlg1SH3-domain and required the SH3-ligand WASp. Further, Dlg1 controlled WASp activation by promoting TCR-triggered conformational opening of WASp. Collectively, our data support a model where Dlg1 regulates p38-dependent proinflammatory cytokine production and p38-independent cytotoxic granule release through the utilization of alternative splice variants, providing a mechanism whereby TCR engagement couples downstream signals to unique effector functions in CD8+ T cells.
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Affiliation(s)
- Oscar Silva
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, California, United States of America
| | - Jillian Crocetti
- Molecular Biology Interdepartmental Program, University of California Los Angeles, Los Angeles, California, United States of America
| | - Lisa A. Humphries
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, California, United States of America
| | - Janis K. Burkhardt
- Department of Laboratory Medicine, Children’s Hospital of Philadelphia and University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - M. Carrie Miceli
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail:
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10
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Gillet L, Rougier JS, Shy D, Sonntag S, Mougenot N, Essers M, Shmerling D, Balse E, Hatem SN, Abriel H. Cardiac-specific ablation of synapse-associated protein SAP97 in mice decreases potassium currents but not sodium current. Heart Rhythm 2014; 12:181-92. [PMID: 25447080 DOI: 10.1016/j.hrthm.2014.09.057] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Indexed: 12/13/2022]
Abstract
BACKGROUND Membrane-associated guanylate kinase (MAGUK) proteins are important determinants of ion channel organization in the plasma membrane. In the heart, the MAGUK protein SAP97, encoded by the DLG1 gene, interacts with several ion channels via their PDZ domain-binding motif and regulates their function and localization. OBJECTIVE The purpose of this study was to assess in vivo the role of SAP97 in the heart by generating a genetically modified mouse model in which SAP97 is suppressed exclusively in cardiomyocytes. METHODS SAP97(fl/fl) mice were generated by inserting loxP sequences flanking exons 1-3 of the SAP97 gene. SAP97(fl/fl) mice were crossed with αMHC-Cre mice to generate αMHC-Cre/SAP97(fl/fl) mice, thus resulting in a cardiomyocyte-specific deletion of SAP97. Quantitative reverse transcriptase-polymerase chain reaction, western blots, and immunostaining were performed to measure mRNA and protein expression levels, and ion channel localization. The patch-clamp technique was used to record ion currents and action potentials. Echocardiography and surface ECGs were performed on anesthetized mice. RESULTS Action potential duration was greatly prolonged in αMHC-Cre/SAP97(fl/fl) cardiomyocytes compared to SAP97(fl/fl) controls, but maximal upstroke velocity was unchanged. This was consistent with the decreases observed in IK1, Ito, and IKur potassium currents and the absence of effect on the sodium current INa. Surface ECG revealed an increased corrected QT interval in αMHC-Cre/SAP97(fl/fl) mice. CONCLUSION These data suggest that ablation of SAP97 in the mouse heart mainly alters potassium channel function. Based on the important role of SAP97 in regulating the QT interval, DLG1 may be a susceptibility gene to be investigated in patients with congenital long QT syndrome.
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Affiliation(s)
- Ludovic Gillet
- Department of Clinical Research, University of Bern, Bern, Switzerland.
| | | | - Diana Shy
- Department of Clinical Research, University of Bern, Bern, Switzerland
| | | | - Nathalie Mougenot
- Plateau d'Expérimentation Coeur, Muscle, Vaisseaux, Université Pierre et Marie Curie, Paris, France
| | - Maria Essers
- Department of Clinical Research, University of Bern, Bern, Switzerland
| | | | - Elise Balse
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR S1166, Institut de Recherche Sur Les Maladies Cardiovasculaires, du Métabolisme et de la Nutrition, Paris, France; Sorbonne Universités, UPMC Univ Paris 06, UMR S1166, Paris, France; Institute of Cardiometabolism & Nutrition, ICAN, Pitié-Salpêtrière Hospital, Paris, France
| | - Stéphane N Hatem
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR S1166, Institut de Recherche Sur Les Maladies Cardiovasculaires, du Métabolisme et de la Nutrition, Paris, France; Sorbonne Universités, UPMC Univ Paris 06, UMR S1166, Paris, France; Institute of Cardiometabolism & Nutrition, ICAN, Pitié-Salpêtrière Hospital, Paris, France
| | - Hugues Abriel
- Department of Clinical Research, University of Bern, Bern, Switzerland.
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11
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Crocetti J, Silva O, Humphries LA, Tibbs MD, Miceli MC. Selective phosphorylation of the Dlg1AB variant is critical for TCR-induced p38 activation and induction of proinflammatory cytokines in CD8+ T cells. THE JOURNAL OF IMMUNOLOGY 2014; 193:2651-60. [PMID: 25098293 DOI: 10.4049/jimmunol.1401196] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
CD8(+) T cells respond to TCR stimulation by producing proinflammatory cytokines, and destroying infected or malignant cells through the production and release of cytotoxic granules. Scaffold protein Discs large homolog 1 (Dlg1) specifies TCR-dependent functions by channeling proximal signals toward the activation of p38-dependent proinflammatory cytokine gene expression and/or p38-independent cytotoxic granule release. Two Dlg1 variants are expressed in CD8(+) T cells via alternative splicing, Dlg1AB and Dlg1B, which have differing abilities coordinate TCR-dependent functions. Although both variants facilitate p38-independent cytotoxicity, only Dlg1AB coordinates p38-dependent proinflammatory cytokine expression. In this study, we identify TCR-induced Dlg1 tyrosine phosphorylation as a key regulatory step required for Dlg1AB-mediated p38-dependent functions, including proinflammatory cytokine expression. We find that Dlg1AB but not Dlg1B is tyrosine phosphorylated by proximal tyrosine kinase Lck in response to TCR stimulation. Furthermore, we identify Dlg1 tyrosine 222 (Y222) as a major site of Dlg1 phosphorylation required for TCR-triggered p38 activation and NFAT-dependent expression of proinflammatory cytokines, but not for p38-independent cytotoxicity. Taken together, our data support a model where TCR-induced phosphorylation of Dlg1 Y222 is a key point of control that endows Dlg1AB with the ability to coordinate p38 activation and proinflammatory cytokine production. We propose blocking Dlg1AB phosphorylation as a novel therapeutic target to specifically block proinflammatory cytokine production but not cytotoxicity.
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Affiliation(s)
- Jillian Crocetti
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095
| | - Oscar Silva
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095
| | - Lisa A Humphries
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095; Amgen, Thousand Oaks, CA 91320; and
| | - Michelle D Tibbs
- Department of Psychology, University of California, Los Angeles, Los Angeles, CA 90095
| | - M Carrie Miceli
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095; Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095;
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12
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Walch L. Emerging role of the scaffolding protein Dlg1 in vesicle trafficking. Traffic 2014; 14:964-73. [PMID: 23829493 DOI: 10.1111/tra.12089] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Revised: 07/02/2013] [Accepted: 07/06/2013] [Indexed: 01/23/2023]
Abstract
Discs large 1 (Dlg1) is a modular scaffolding protein implicated in the control of cell polarity through assembly of specific multiprotein complexes, including receptors, ion channels and signaling proteins, at specialized zones of the plasma membrane. Recent data have shown that in addition to these well-known interaction partners, Dlg1 may also recruit components of the vesicle trafficking machinery either to the plasma membrane or to transport vesicles. Here, we discuss Dlg1 function in vesicle formation, targeting, tethering and fusion, in both the exocytotic and endocytotic pathways. These pathways contribute to cell functions as major and diverse as glutamatergic activity in the neurons, membrane homeostasis in Schwann cell myelination, insulin stimulation of glucose transport in adipocytes, or endothelial secretion of the hemostatic protein, von Willebrand factor (VWF).
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Affiliation(s)
- Laurence Walch
- INSERM U698, Université Paris 7, Hemostasis, Bio-engineering and Cardiovascular Remodeling, CHU X. Bichat, Paris, France.
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13
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Philippe M, Léger T, Desvaux R, Walch L. Discs large 1 (Dlg1) scaffolding protein participates with clathrin and adaptator protein complex 1 (AP-1) in forming Weibel-Palade bodies of endothelial cells. J Biol Chem 2013; 288:13046-56. [PMID: 23532850 DOI: 10.1074/jbc.m112.441261] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Weibel-Palade bodies (WPBs) are specific cigar-shaped granules that store von Willebrand factor (VWF) for its regulated secretion by endothelial cells. The first steps of the formation of these granules at the trans-Golgi network specifically require VWF aggregation and an external scaffolding complex that contains the adaptator protein complex 1 (AP-1) and clathrin. Discs large 1 (Dlg1) is generally considered to be a modular scaffolding protein implicated in the control of cell polarity in a large variety of cells by specific recruiting of receptors, channels, or signaling proteins to specialized zones of the plasma membrane. We propose here that in endothelial cells, Dlg1, in a complex with AP-1 and clathrin, participates in the biogenesis of WPBs. Supporting data show that Dlg1 colocalizes with microtubules, intermediate filaments, and Golgi markers. Tandem mass spectrometry experiments led to the identification of clathrin as an Dlg1-interacting partner. Interaction was confirmed by in situ proximity ligation assays. Furthermore, AP-1 and VWF immunoprecipitate and colocalize with Dlg1 in the juxtanuclear zone. Finally, Dlg1 depletion by siRNA duplexes disrupts trans-Golgi network morphology and WPB formation. Our results provide the first evidence for an unexpected role of Dlg1 in controlling the formation of specific secretory granules involved in VWF exocytosis in endothelial cells.
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Affiliation(s)
- Monique Philippe
- INSERM U698, Université Paris 7, Hemostasis, Bio-Engineering and Cardiovascular Remodeling, CHU X. Bichat, 75018 Paris, France
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14
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Fourie C, Li D, Montgomery JM. The anchoring protein SAP97 influences the trafficking and localisation of multiple membrane channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:589-94. [PMID: 23535319 DOI: 10.1016/j.bbamem.2013.03.015] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2013] [Revised: 02/26/2013] [Accepted: 03/15/2013] [Indexed: 12/23/2022]
Abstract
SAP97 is a member of the MAGUK family of proteins that play a major role in the trafficking and targeting of membrane ion channels and cytosolic structural proteins in multiple cell types. Within neurons, SAP97 is localised throughout the secretory trafficking pathway and at the postsynaptic density (PSD). SAP97 differs from other MAGUK family members largely in its long N-terminus and in the sequences between the SH3 and GUK domains, where SAP97 undergoes significant alternative splicing to produce multiple SAP97 isoforms. These splice insertions endow SAP97 with differential cellular localisation patterns and functional roles within neurons. With regard to membrane ion channels, SAP97 forms multi-protein complexes with AMPA and NMDA-type glutamate receptors, and Kv1.4, Kv4.2, and Kir2.2 potassium channels, playing a major role in trafficking and anchoring ion channel surface expression. This highlights SAP97 not only as a regulator of neuronal excitability, synaptic function and plasticity in the brain, but also as a target for the pathophysiology of a number of neurological disorders. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters. Guest Editor: Jean Claude Hervé.
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Affiliation(s)
- Chantelle Fourie
- Department of Physiology, University of Auckland, New Zealand; Centre for Brain Research, University of Auckland, New Zealand
| | - Dong Li
- Department of Physiology, University of Auckland, New Zealand; Centre for Brain Research, University of Auckland, New Zealand
| | - Johanna M Montgomery
- Department of Physiology, University of Auckland, New Zealand; Centre for Brain Research, University of Auckland, New Zealand.
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15
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Balse E, Steele DF, Abriel H, Coulombe A, Fedida D, Hatem SN. Dynamic of Ion Channel Expression at the Plasma Membrane of Cardiomyocytes. Physiol Rev 2012; 92:1317-58. [DOI: 10.1152/physrev.00041.2011] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Cardiac myocytes are characterized by distinct structural and functional entities involved in the generation and transmission of the action potential and the excitation-contraction coupling process. Key to their function is the specific organization of ion channels and transporters to and within distinct membrane domains, which supports the anisotropic propagation of the depolarization wave. This review addresses the current knowledge on the molecular actors regulating the distinct trafficking and targeting mechanisms of ion channels in the highly polarized cardiac myocyte. In addition to ubiquitous mechanisms shared by other excitable cells, cardiac myocytes show unique specialization, illustrated by the molecular organization of myocyte-myocyte contacts, e.g., the intercalated disc and the gap junction. Many factors contribute to the specialization of the cardiac sarcolemma and the functional expression of cardiac ion channels, including various anchoring proteins, motors, small GTPases, membrane lipids, and cholesterol. The discovery of genetic defects in some of these actors, leading to complex cardiac disorders, emphasizes the importance of trafficking and targeting of ion channels to cardiac function. A major challenge in the field is to understand how these and other actors work together in intact myocytes to fine-tune ion channel expression and control cardiac excitability.
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Affiliation(s)
- Elise Balse
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
| | - David F. Steele
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
| | - Hugues Abriel
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
| | - Alain Coulombe
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
| | - David Fedida
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
| | - Stéphane N. Hatem
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
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16
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Tully MD, Grossmann JG, Phelan M, Pandelaneni S, Leyland M, Lian LY. Conformational Characterization of Synapse-Associated Protein 97 by Nuclear Magnetic Resonance and Small-Angle X-ray Scattering Shows Compact and Elongated Forms. Biochemistry 2012; 51:899-908. [DOI: 10.1021/bi201178v] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mark D. Tully
- Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, U.K
| | - J. Günter Grossmann
- Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, U.K
| | - Marie Phelan
- Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, U.K
| | - Sravan Pandelaneni
- Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, U.K
| | - Mark Leyland
- Department of Biochemistry, University of Leicester, Leicester LE1 9HN, U.K
| | - Lu-Yun Lian
- Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, U.K
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17
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Maïga O, Philippe M, Kotelevets L, Chastre E, Benadda S, Pidard D, Vranckx R, Walch L. Identification of mitogen-activated protein/extracellular signal-responsive kinase kinase 2 as a novel partner of the scaffolding protein human homolog of disc-large. FEBS J 2011; 278:2655-65. [PMID: 21615688 DOI: 10.1111/j.1742-4658.2011.08192.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Human disc-large homolog (hDlg), also known as synapse-associated protein 97, is a scaffold protein, a member of the membrane-associated guanylate kinase family, implicated in neuronal synapses and epithelial-epithelial cell junctions whose expression and function remains poorly characterized in most tissues, particularly in the vasculature. In human vascular tissues, hDlg is highly expressed in smooth muscle cells (VSMCs). Using the yeast two-hybrid system to screen a human aorta cDNA library, we identified mitogen-activated protein/extracellular signal-responsive kinase (ERK) kinase (MEK)2, a member of the ERK cascade, as an hDlg binding partner. Site-directed mutagenesis showed a major involvement of the PSD-95, disc-large, ZO-1 domain-2 of hDlg and the C-terminal sequence RTAV of MEK2 in this interaction. Coimmunoprecipitation assays in both human VSMCs and human embryonic kidney 293 cells, demonstrated that endogenous hDlg physically interacts with MEK2 but not with MEK1. Confocal microscopy suggested a colocalization of the two proteins at the inner layer of the plasma membrane of confluent human embryonic kidney 293 cells, and in a perinuclear area in human VSMCs. Additionally, hDlg also associates with the endoplasmic reticulum and microtubules in these latter cells. Taken together, these findings allow us to hypothesize that hDlg acts as a MEK2-specific scaffold protein for the ERK signaling pathway, and may improve our understanding of how scaffold proteins, such as hDlg, differentially tune MEK1/MEK2 signaling and cell responses.
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18
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Petitprez S, Zmoos AF, Ogrodnik J, Balse E, Raad N, El-Haou S, Albesa M, Bittihn P, Luther S, Lehnart SE, Hatem SN, Coulombe A, Abriel H. SAP97 and dystrophin macromolecular complexes determine two pools of cardiac sodium channels Nav1.5 in cardiomyocytes. Circ Res 2010; 108:294-304. [PMID: 21164104 DOI: 10.1161/circresaha.110.228312] [Citation(s) in RCA: 187] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE The cardiac sodium channel Na(v)1.5 plays a key role in excitability and conduction. The 3 last residues of Na(v)1.5 (Ser-Ile-Val) constitute a PDZ-domain binding motif that interacts with the syntrophin-dystrophin complex. As dystrophin is absent at the intercalated discs, Na(v)1.5 could potentially interact with other, yet unknown, proteins at this site. OBJECTIVE The aim of this study was to determine whether Na(v)1.5 is part of distinct regulatory complexes at lateral membranes and intercalated discs. METHODS AND RESULTS Immunostaining experiments demonstrated that Na(v)1.5 localizes at lateral membranes of cardiomyocytes with dystrophin and syntrophin. Optical measurements on isolated dystrophin-deficient mdx hearts revealed significantly reduced conduction velocity, accompanied by strong reduction of Na(v)1.5 at lateral membranes of mdx cardiomyocytes. Pull-down experiments revealed that the MAGUK protein SAP97 also interacts with the SIV motif of Na(v)1.5, an interaction specific for SAP97 as no pull-down could be detected with other cardiac MAGUK proteins (PSD95 or ZO-1). Furthermore, immunostainings showed that Na(v)1.5 and SAP97 are both localized at intercalated discs. Silencing of SAP97 expression in HEK293 and rat cardiomyocytes resulted in reduced sodium current (I(Na)) measured by patch-clamp. The I(Na) generated by Na(v)1.5 channels lacking the SIV motif was also reduced. Finally, surface expression of Na(v)1.5 was decreased in silenced cells, as well as in cells transfected with SIV-truncated channels. CONCLUSIONS These data support a model with at least 2 coexisting pools of Na(v)1.5 channels in cardiomyocytes: one targeted at lateral membranes by the syntrophin-dystrophin complex, and one at intercalated discs by SAP97.
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Affiliation(s)
- Séverine Petitprez
- University of Bern, Department of Clinical Research, Murtenstrasse, 35, 3010 Bern, Switzerland
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Nikandrova YA, Jiao Y, Baucum AJ, Tavalin SJ, Colbran RJ. Ca2+/calmodulin-dependent protein kinase II binds to and phosphorylates a specific SAP97 splice variant to disrupt association with AKAP79/150 and modulate alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type glutamate receptor (AMPAR) activity. J Biol Chem 2010; 285:923-34. [PMID: 19858198 PMCID: PMC2801293 DOI: 10.1074/jbc.m109.033985] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2009] [Revised: 09/24/2009] [Indexed: 11/06/2022] Open
Abstract
Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) promotes trafficking and activation of the GluR1 subunit of alpha-amino- 3-hydroxy-5-methyl-4-isoxazolepropionic acid-type glutamate receptors (AMPARs) during synaptic plasticity. GluR1 is also modulated in parallel by multiprotein complexes coordinated by synapse-associated protein 97 (SAP97) that contain A-kinase anchoring protein 79/150 (AKAP79/150), protein kinase A, and protein phosphatase 2B. Here we show that SAP97 is present in CaMKII immune complexes isolated from rodent brain as well as from HEK293 cells co-expressing CaMKIIalpha and SAP97. CaMKIIalpha phosphorylated recombinant SAP97 within immune complexes in vitro and in intact cells. Four alternative mRNA splice variants of SAP97 expressing combinations of four inserts (I2, I3, I4, I5) in the U5 region between Src homology 3 (SH3) and guanylyl kinase-like (GK) domains were identified in rat brain at postnatal day 21. CaMKIIalpha preferentially phosphorylated a full-length SAP97 and a glutathione S-transferase (GST) fusion protein containing the I3 and I5 inserts (SAP97-I3I5 and GST-SH3-I3I5-GK, respectively) and also specifically interacted with GST-SH3-I3I5-GK compared with GST proteins containing other naturally occurring insert combinations. AKAP79/150 also directly and specifically bound only to GST-SH3-I3I5-GK, but CaMKII phosphorylation of GST-SH3-I3I5-GK prevented this interaction. AKAP79-dependent down-regulation of GluR1 AMPAR currents was ablated by overexpression of SAP97-I2I5 (which does not bind AKAP79) or by infusion of active CaMKIIalpha. Collectively, the data suggest that CaMKIIalpha targets a specific SAP97 splice variant to disengage AKAP79/150 from regulating GluR1 AMPARs, providing new insight into protein-protein interactions and phosphorylation events that are required for normal regulation of glutamatergic synaptic transmission, learning, and memory.
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Affiliation(s)
| | - Yuxia Jiao
- From the Department of Molecular Physiology and Biophysics
| | - Anthony J. Baucum
- From the Department of Molecular Physiology and Biophysics
- Center for Molecular Neuroscience, and
| | - Steven J. Tavalin
- the Department of Pharmacology, University of Tennessee Health Science Center, Memphis, Tennessee 38163
| | - Roger J. Colbran
- From the Department of Molecular Physiology and Biophysics
- Center for Molecular Neuroscience, and
- Vanderbilt Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, Tennessee 37232 and
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Hatem SN, Coulombe A, Balse E. Specificities of atrial electrophysiology: Clues to a better understanding of cardiac function and the mechanisms of arrhythmias. J Mol Cell Cardiol 2009; 48:90-5. [PMID: 19744488 DOI: 10.1016/j.yjmcc.2009.08.029] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2009] [Revised: 08/14/2009] [Accepted: 08/29/2009] [Indexed: 11/19/2022]
Abstract
The electrical properties of the atria and ventricles differ in several aspects reflecting the distinct role of the atria in cardiac physiology. The study of atrial electrophysiology had greatly contributed to the understanding of the mechanisms of atrial fibrillation (AF). Only the atrial L-type calcium current is regulated by serotonine or, under basal condition, by phosphodiesterases. These distinct regulations can contribute to I(Ca) down-regulation observed during AF, which is an important determinant of action potential refractory period shortening. The voltage-gated potassium current, I(Kur), has a prominent role in the repolarization of the atrial but not ventricular AP. In many species, this current is based on the functional expression of K(V)1.5 channels, which might represent a specific therapeutic target for AF. Mechanisms regulating the trafficking of K(V)1.5 channels to the plasma membrane are being actively investigated. The resting potential of atrial myocytes is maintained by various inward rectifier currents which differ with ventricle currents by a reduced density of I(K1), the presence of a constitutively active I(KACh) and distinct regulation of I(KATP). Stretch-sensitive or mechanosensitive ion channels are particularly active in atrial myocytes and are involved in the secretion of the natriuretic peptide. Integration of knowledge on electrical properties of atrial myocytes in comprehensive schemas is now necessary for a better understanding of the physiology of atria and the mechanisms of AF.
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El-Haou S, Balse E, Neyroud N, Dilanian G, Gavillet B, Abriel H, Coulombe A, Jeromin A, Hatem SN. Kv4 potassium channels form a tripartite complex with the anchoring protein SAP97 and CaMKII in cardiac myocytes. Circ Res 2009; 104:758-69. [PMID: 19213956 DOI: 10.1161/circresaha.108.191007] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Membrane-associated guanylate kinase (MAGUK) proteins are major determinants of the organization of ion channels in the plasma membrane in various cell types. Here, we investigated the interaction between the MAGUK protein SAP97 and cardiac Kv4.2/3 channels, which account for a large part of the outward potassium current, I(to), in heart. We found that the Kv4.2 and Kv4.3 channels C termini interacted with SAP97 via a SAL amino acid sequence. SAP97 and Kv4.3 channels were colocalized in the sarcolemma of cardiomyocytes. In CHO cells, SAP97 clustered Kv4.3 channels in the plasma membrane and increased the current independently of the presence of KChIP and dipeptidyl peptidase-like protein-6. Suppression of SAP97 by using short hairpin RNA inhibited I(to) in cardiac myocytes, whereas its overexpression by using an adenovirus increased I(to). Kv4.3 channels without the SAL sequence were no longer regulated by Ca2+/calmodulin kinase (CaMK)II inhibitors. In cardiac myocytes, pull-down and coimmunoprecipitation assays showed that the Kv4 channel C terminus, SAP97, and CaMKII interact together, an interaction suppressed by SAP97 silencing and enhanced by SAP97 overexpression. In HEK293 cells, SAP97 silencing reproduced the effects of CaMKII inhibition on current kinetics and suppressed Kv4/CaMKII interactions. In conclusion, SAP97 is a major partner for surface expression and CaMKII-dependent regulation of cardiac Kv4 channels.
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Affiliation(s)
- Saïd El-Haou
- UMRS-956, Faculté de Médecine Pierre-Marie Curie, 91 Boulevard de l'Hôpital, 75013 Paris, France
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22
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Balijepalli RC, Kamp TJ. Caveolae, ion channels and cardiac arrhythmias. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2009; 98:149-60. [PMID: 19351512 DOI: 10.1016/j.pbiomolbio.2009.01.012] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Caveolae are specialized membrane microdomains enriched in cholesterol and sphingolipids which are present in multiple cell types including cardiomyocytes. Along with the essential scaffolding protein caveolin-3, a number of different ion channels and transporters have been localized to caveolae in cardiac myocytes including L-type Ca2+ channels (Ca(v)1.2), Na+ channels (Na(v)1.5), pacemaker channels (HCN4), Na+/Ca2+ exchanger (NCX1) and others. Closely associated with these channels are specific macromolecular signaling complexes that provide highly localized regulation of the channels. Mutations in the caveolin-3 gene (CAV3) have been linked with the congenital long QT syndrome (LQT9), and mutations in caveolar-localized ion channels may contribute to other inherited arrhythmias. Changes in the caveolar microdomain in acquired heart disease may also lead to dysregulation and dysfunction of ion channels, altering the risk of arrhythmias in conditions such as heart failure. This review highlights the existing evidence identifying and characterizing ion channels localized to caveolae in cardiomyocytes and their role in arrhythmogenesis.
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Affiliation(s)
- Ravi C Balijepalli
- Department of Medicine, Cellular and Molecular Arrhythmia Research Program, University of Wisconsin, Madison, WI 53792, USA
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23
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Peters CJ, Chow SS, Angoli D, Nazzari H, Cayabyab FS, Morshedian A, Accili EA. In situ co-distribution and functional interactions of SAP97 with sinoatrial isoforms of HCN channels. J Mol Cell Cardiol 2009; 46:636-43. [PMID: 19336273 DOI: 10.1016/j.yjmcc.2009.01.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2008] [Revised: 01/15/2009] [Accepted: 01/15/2009] [Indexed: 11/29/2022]
Abstract
The sinoatrial node is a region of specialized cardiomyocytes that is responsible for the repetitive activity of the adult heart. The sinoatrial node is heavily innervated compared to the other regions of the heart, and the specialized cardiomyocytes of this region receive neural and hormonal input from the autonomic nervous system, which leads to changes in heart rate. A key regulator of sinoatrial beating frequency in response to autonomic input is the hyperpolarization-activated cyclic nucleotide gated (HCN) channel, a mixed cationic channel whose activity is increased by the binding of cAMP to its cytoplasmic side. HCN channels localize to distinct regions or "hot spots" on the cell surface of sinoatrial myocytes, but how these regions are formed, whether they correspond to specific signaling domains and the specific HCN isoforms and other proteins therein are not known. In this paper, we show that both HCN2 and HCN4 isoforms co-distribute with the adapter protein SAP97, an important component of distinct punctae in the sinoatrial node of the rabbit heart. HCN4, but not HCN2, also co-distributes with the post-synaptic marker beta-catenin, thus identifying diverse organized domains within this tissue. Furthermore, we show, using heterologous expression systems, whole-cell patch clamp electrophysiology and imaging, that SAP97 interacts functionally with HCN in a manner that depends upon the PDZ compatible binding motif of the C-terminus, but that its effects on I(f) behaviour are HCN isoform and context dependent. Together, the data suggest that SAP97 contributes to isoform specific organization of HCN channels within specific domains in the sinoatrial node of the rabbit.
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Affiliation(s)
- Christian J Peters
- Department of Cellular and Physiological Sciences, University of British Columbia, #2320-2350 Health Sciences Mall, Vancouver, BC V6T1Z3, Canada
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24
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Perugi F, Muriaux D, Ramirez BC, Chabani S, Decroly E, Darlix JL, Blot V, Pique C. Human Discs Large is a new negative regulator of human immunodeficiency virus-1 infectivity. Mol Biol Cell 2008; 20:498-508. [PMID: 18946087 DOI: 10.1091/mbc.e08-02-0189] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Human immunodeficiency virus (HIV)-1 replication is positively or negatively regulated through multiple interactions with host cell proteins. We report here that human Discs Large (Dlg1), a scaffold protein recruited beneath the plasma membrane and involved in the assembly of multiprotein complexes, restricts HIV-1 infectivity. The endogenous Dlg1 and HIV-1 Gag polyprotein spontaneously interact in HIV-1-chronically infected T cells. Depleting endogenous Dlg1 in either adherent cells or T cells does not affect Gag maturation, production, or release, but it enhances the infectivity of progeny viruses five- to sixfold. Conversely, overexpression of Dlg1 reduces virus infectivity by approximately 80%. Higher virus infectivity upon Dlg1 depletion correlates with increased Env content in cells and virions, whereas the amount of virus-associated Gag or genomic RNA remains identical. Dlg1 knockdown is also associated with the redistribution and colocalization of Gag and Env toward CD63 and CD82 positive vesicle-like structures, including structures that seem to still be connected to the plasma membrane. This study identifies both a new negative regulator that targets the very late steps of the HIV-1 life cycle, and an assembly pathway that optimizes HIV-1 infectivity.
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Affiliation(s)
- Fabien Perugi
- Department of Cell Biology, Institut Cochin, Université Paris Descartes, Centre National de la Recherche Scientifique Unité Mixte de Recherche, Institut National de la Santé et de la Recherche Médicale, Paris, France
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25
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Abi-Char J, El-Haou S, Balse E, Neyroud N, Vranckx R, Coulombe A, Hatem SN. The anchoring protein SAP97 retains Kv1.5 channels in the plasma membrane of cardiac myocytes. Am J Physiol Heart Circ Physiol 2008; 294:H1851-61. [DOI: 10.1152/ajpheart.01045.2007] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Membrane- associated guanylate kinase proteins (MAGUKs) are important determinants of localization and organization of ion channels into specific plasma membrane domains. However, their exact role in channel function and cardiac excitability is not known. We examined the effect of synapse-associated protein 97 (SAP97), a MAGUK abundantly expressed in the heart, on the function and localization of Kv1.5 subunits in cardiac myocytes. Recombinant SAP97 or Kv1.5 subunits tagged with green fluorescent protein (GFP) were overexpressed in rat neonatal cardiac myocytes and in Chinese hamster ovary (CHO) cells from adenoviral or plasmidic vectors. Immunocytochemistry, fluorescence recovery after photobleaching, and patch-clamp techniques were used to study the effects of SAP97 on the localization, mobility, and function of Kv1.5 subunits. Adenovirus-mediated SAP97 overexpression in cardiac myocytes resulted in the clustering of endogenous Kv1.5 subunits at myocyte-myocyte contacts and an increase in both the maintained component of the outward K+current, IKur(5.64 ± 0.57 pA/pF in SAP97 myocytes vs. 3.23 ± 0.43 pA/pF in controls) and the number of 4-aminopyridine-sensitive potassium channels in cell-attached membrane patches. In live myocytes, GFP-Kv1.5 subunits were mobile and organized in clusters at the basal plasma membrane, whereas SAP97 overexpression reduced their mobility. In CHO cells, Kv1.5 channels were diffusely distributed throughout the cell body and freely mobile. When coexpressed with SAP97, Kv subunits were organized in plaquelike clusters and poorly mobile. In conclusion, SAP97 regulates the K+current in cardiac myocytes by retaining and immobilizing Kv1.5 subunits in the plasma membrane. This new regulatory mechanism may contribute to the targeting of Kv channels in cardiac myocytes.
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26
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Abstract
The proper trafficking and localization of cardiac potassium channels is profoundly important to the regulation of the regionally distinct action potentials across the myocardium. These processes are only beginning to be unravelled and involve modulators of channel synthesis and assembly, post-translational processing, various molecular motors and an increasing number of modifying enzymes and molecular anchors. The roles of anchoring proteins, molecular motors and kinases are explored and recent findings on channel internalization and trafficking are presented.
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27
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28
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Abi-Char J, Maguy A, Coulombe A, Balse E, Ratajczak P, Samuel JL, Nattel S, Hatem SN. Membrane cholesterol modulates Kv1.5 potassium channel distribution and function in rat cardiomyocytes. J Physiol 2007; 582:1205-17. [PMID: 17525113 PMCID: PMC2075263 DOI: 10.1113/jphysiol.2007.134809] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Membrane lipid composition is a major determinant of cell excitability. In this study, we assessed the role of membrane cholesterol composition in the distribution and function of Kv1.5-based channels in rat cardiac membranes. In isolated rat atrial myocytes, the application of methyl-beta-cyclodextrin (MCD), an agent that depletes membrane cholesterol, caused a delayed increase in the Kv1.5-based sustained component, I(kur), which reached steady state in approximately 7 min. This effect was prevented by preloading the MCD with cholesterol. MCD-increased current was inhibited by low 4-aminopyridine concentration. Neonatal rat cardiomyocytes transfected with Green Fluorescent Protein (GFP)-tagged Kv1.5 channels showed a large ultrarapid delayed-rectifier current (I(Kur)), which was also stimulated by MCD. In atrial cryosections, Kv1.5 channels were mainly located at the intercalated disc, whereas caveolin-3 predominated at the cell periphery. A small portion of Kv1.5 floated in the low-density fractions of step sucrose-gradient preparations. In live neonatal cardiomyocytes, GFP-tagged Kv1.5 channels were predominantly organized in clusters at the basal plasma membrane. MCD caused reorganization of Kv1.5 subunits into larger clusters that redistributed throughout the plasma membrane. The MCD effect on clusters was sizable 7 min after its application. We conclude that Kv1.5 subunits are concentrated in cholesterol-enriched membrane microdomains distinct from caveolae, and that redistribution of Kv1.5 subunits by depletion of membrane cholesterol increases their current-carrying capacity.
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29
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Abstract
The regulation of ion channels involves more than just modulation of their synthesis and kinetics, as controls on their trafficking and localization are also important. Although the body of knowledge is fairly large, the entire trafficking pathway is not known for any one channel. This review summarizes current knowledge on the trafficking of potassium channels that are expressed in the heart. Our knowledge of channel assembly, trafficking through the Golgi apparatus and on to the surface is covered, as are controls on channel surface retention and endocytosis.
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Affiliation(s)
- David F Steele
- Department of Physiology, University of British Columbia, 2146 Health Sciences Mall, Vancouver, British Columbia, Canada V6T 1Z3
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30
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Mathur R, Choi WS, Eldstrom J, Wang Z, Kim J, Steele DF, Fedida D. A specific N-terminal residue in Kv1.5 is required for upregulation of the channel by SAP97. Biochem Biophys Res Commun 2006; 342:1-8. [PMID: 16466689 DOI: 10.1016/j.bbrc.2006.01.110] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2006] [Accepted: 01/23/2006] [Indexed: 11/20/2022]
Abstract
We have previously reported that SAP97 enhancement of hKv1.5 currents requires an intact Kv1.5 N-terminus and is independent of the PDZ-binding motif at the C-terminus of the channel [J. Eldstrom, W.S. Choi, D.F. Steele, D. Fedida, SAP97 increases Kv1.5 currents through an indirect N-terminal mechanism, FEBS Lett. 547 (2003) 205-211]. Here, we report that an interaction between the two proteins can be detected under certain conditions but their interaction is irrelevant to the enhancement of channel expression. Instead, a threonine residue at position 15 in the hKv1.5 N-terminus is critically important. Mutation of this residue, which lies within a consensus site for phosphorylation by protein kinase C, to an alanine, completely abrogated the effect of SAP97 on channel expression. Although we were unable to detect phosphorylation of this residue, specific inhibition of kinase C by Calphostin C eliminated the increase in wild-type hKv1.5 currents associated with SAP97 overexpression suggesting a role for this kinase in the response.
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Affiliation(s)
- Rajesh Mathur
- Department of Cellular and Physiological Sciences, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, Canada V6T 1Z3
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31
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Leoni AL, Marionneau C, Demolombe S, Le Bouter S, Mangoni ME, Escande D, Charpentier F. Chronic heart rate reduction remodels ion channel transcripts in the mouse sinoatrial node but not in the ventricle. Physiol Genomics 2005; 24:4-12. [PMID: 16219869 DOI: 10.1152/physiolgenomics.00161.2005] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We investigated the effects of chronic and moderate heart rate (HR) reduction on ion channel expression in the mouse sinoatrial node (SAN) and ventricle. Ten-week-old male C57BL/6 mice were treated twice daily with either vehicle or ivabradine at 5 mg/kg given orally during 3 wk. The effects of HR reduction on cardiac electrical activity were investigated in anesthetized mice with serial ECGs and in freely moving mice with telemetric recordings. With the use of high-throughput real-time RT-PCR, the expression of 68 ion channel subunits was evaluated in the SAN and ventricle at the end of the treatment period. In conscious mice, ivabradine induced a mean 16% HR reduction over a 24-h period that was sustained over the 3-wk administration. Other ECG parameters were not modified. Two-way hierarchical clustering analysis of gene expression revealed a separation of ventricles from SANs but no discrimination between treated and untreated ventricles, indicating that HR reduction per se induced limited remodeling in this tissue. In contrast, SAN samples clustered in two groups depending on the treatment. In the SAN from ivabradine-treated mice, the expression of nine ion channel subunits, including Navbeta1 (-25%), Cav3.1 (-29%), Kir6.1 (-28%), Kvbeta2 (-41%), and Kvbeta3 (-30%), was significantly decreased. Eight genes were significantly upregulated, including K+ channel alpha-subunits (Kv1.1, +30%; Kir2.1, +29%; Kir3.1, +41%), hyperpolarization-activated cation channels (HCN2, +24%; HCN4, +52%), and connexin 43 (+26%). We conclude that reducing HR induces a complex remodeling of ion channel expression in the SAN but has little impact on ion channel transcripts in the ventricle.
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Affiliation(s)
- Anne-Laure Leoni
- Institut National de la Santé et de la Recherche Médicale (INSERM), U533, l'Institut du Thorax, Nantes, France
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Palmer CL, Cotton L, Henley JM. The molecular pharmacology and cell biology of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors. Pharmacol Rev 2005; 57:253-77. [PMID: 15914469 PMCID: PMC3314513 DOI: 10.1124/pr.57.2.7] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptors (AMPARs) are of fundamental importance in the brain. They are responsible for the majority of fast excitatory synaptic transmission, and their overactivation is potently excitotoxic. Recent findings have implicated AMPARs in synapse formation and stabilization, and regulation of functional AMPARs is the principal mechanism underlying synaptic plasticity. Changes in AMPAR activity have been described in the pathology of numerous diseases, such as Alzheimer's disease, stroke, and epilepsy. Unsurprisingly, the developmental and activity-dependent changes in the functional synaptic expression of these receptors are under tight cellular regulation. The molecular and cellular mechanisms that control the postsynaptic insertion, arrangement, and lifetime of surface-expressed AMPARs are the subject of intense and widespread investigation. For example, there has been an explosion of information about proteins that interact with AMPAR subunits, and these interactors are beginning to provide real insight into the molecular and cellular mechanisms underlying the cell biology of AMPARs. As a result, there has been considerable progress in this field, and the aim of this review is to provide an account of the current state of knowledge.
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Affiliation(s)
- Claire L Palmer
- Medical Research Council Centre for Synaptic Plasticity, Department of Anatomy, School of Medical Sciences, Bristol University, Bristol, UK
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Sierralta J, Mendoza C. PDZ-containing proteins: alternative splicing as a source of functional diversity. ACTA ACUST UNITED AC 2005; 47:105-15. [PMID: 15572166 DOI: 10.1016/j.brainresrev.2004.06.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/08/2004] [Indexed: 12/30/2022]
Abstract
Scaffold proteins allow specific protein complexes to be assembled in particular regions of the cell at which they organize subcellular structures and signal transduction complexes. This characteristic is especially important for neurons, which are highly polarized cells. Among the domains contained by scaffold proteins, the PSD-95, Discs-large, ZO-1 (PDZ) domains are of particular relevance in signal transduction processes and maintenance of neuronal and epithelial polarity. These domains are specialized in the binding of the carboxyl termini of proteins allowing membrane proteins to be localized by the anchoring to the cytoskeleton mediated by PDZ-containing scaffold proteins. In vivo studies carried out in Drosophila have taught that the role of many scaffold proteins is not limited to a single process; thus, in many cases the same genes are expressed in different tissues and participate in apparently very diverse processes. In addition to the differential expression of interactors of scaffold proteins, the expression of variants of these molecular scaffolds as the result of the alternative processing of the genes that encode them is proving to be a very important source of variability and complexity on a main theme. Alternative splicing in the nervous system is well documented, where specific isoforms play roles in neurotransmission, ion channel function, neuronal cell recognition, and are developmentally regulated making it a major mechanism of functional diversity. Here we review the current state of knowledge about the diversity and the known function of PDZ-containing proteins in Drosophila with emphasis in the role played by alternatively processed forms in the diversity of functions attributed to this family of proteins.
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Affiliation(s)
- Jimena Sierralta
- Program of Physiology and Biophysics, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Centro de Neurociencias Integradas, Independencia 1027, Santiago, Chile.
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Folco EJ, Liu GX, Koren G. Caveolin-3 and SAP97 form a scaffolding protein complex that regulates the voltage-gated potassium channel Kv1.5. Am J Physiol Heart Circ Physiol 2004; 287:H681-90. [PMID: 15277200 DOI: 10.1152/ajpheart.00152.2004] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The targeting of ion channels to particular membrane microdomains and their organization in macromolecular complexes allow excitable cells to respond efficiently to extracellular signals. In this study, we describe the formation of a complex that contains two scaffolding proteins: caveolin-3 (Cav-3) and a membrane-associated guanylate kinase (MAGUK), SAP97. Complex formation involves the association of Cav-3 with a segment of SAP97 localized between its PDZ2 and PDZ3 domains. In heterologous expression systems, this scaffolding complex can recruit Kv1.5 to form a tripartite complex in which each of the three components interacts with the other two. These interactions regulate the expression of currents encoded by a glycosylation-deficient mutant of Kv1.5. We conclude that the association of Cav-3 with SAP97 may constitute the nucleation site for the assembly of macromolecular complexes containing potassium channels.
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Affiliation(s)
- Eduardo J Folco
- Bioelectricity Laboratory, Cardiovascular Division, Brigham and Women's Hospital, Boston, MA 02115, USA
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Godreau D, Neyroud N, Vranckx R, Hatem S. Les MAGUK : au-delà de l’accrochage des canaux ioniques. Med Sci (Paris) 2004; 20:84-8. [PMID: 14770369 DOI: 10.1051/medsci/200420184] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A family of anchoring proteins named MAGUK (for membrane associated guanylate kinase) has emerged as a key element in the organization of protein complexes in specialized membrane regions. These proteins are characterized by the presence of multipe protein-protein interaction domains including PDZ and SH3 domains. The MAGUK family comprises the post-synaptic density 95 (PSD-95) protein and closely related molecules such as chapsyn-110, synapse-associated protein 102 (SAP-102), and SAP-97. These are located either on the pre- and/or post-synaptic sides of synapses or at cell-cell adhesion sites of epithelial cells. MAGUK proteins interact with glutamate receptors and various ionic channels. For instance, an interaction has been reported between the first two PDZ domains of MAGUK proteins and several channels via a consensus sequence Thr/Ser-X-Val/Leu usually located at their carboxy terminus. The role of these anchoring proteins in channel function is not fully understood. MAGUK proteins enhance the current density by increasing the number of functional channels to the sarcolemma. They can also facilitate signaling between channels and several enzymes or G protein-dependent signaling pathways. In the heart also, MAGUK proteins are abundantly expressed and they interact with various channels including Shaker Kv1.5 and connexins.
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Affiliation(s)
- David Godreau
- Inserm U. 460, bâtiment 13, CHU Xavier Bichat-Claude Bernard, 46, rue Henri Huchard, 75877 Paris 18, France
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