title: Pak1 is required to maintain ventricular Ca²⁺ homeostasis and electrophysiological stability through SERCA2a regulation in mice.
abstract: BACKGROUND
  Impaired sarcoplasmic reticular Ca(2+) uptake resulting from decreased sarcoplasmic reticulum Ca(2+)-ATPase type 2a (SERCA2a) expression or activity is a characteristic of heart failure with its associated ventricular arrhythmias. Recent attempts at gene therapy of these conditions explored strategies enhancing SERCA2a expression and the activity as novel approaches to heart failure management. We here explore the role of Pak1 in maintaining ventricular Ca(2+) homeostasis and electrophysiological stability under both normal physiological and acute and chronic β-adrenergic stress conditions.
  
  
  RESULTS
  Mice with a cardiomyocyte-specific Pak1 deletion (Pak1(cko)), but not controls (Pak1(f/f)), showed high incidences of ventricular arrhythmias and electrophysiological instability during either acute β-adrenergic or chronic β-adrenergic stress leading to hypertrophy, induced by isoproterenol. Isolated Pak1(cko) ventricular myocytes correspondingly showed aberrant cellular Ca(2+) homeostasis. Pak1(cko) hearts showed an associated impairment of SERCA2a function and downregulation of SERCA2a mRNA and protein expression. Further explorations of the mechanisms underlying the altered transcriptional regulation demonstrated that exposure to control Ad-shC2 virus infection increased SERCA2a protein and mRNA levels after phenylephrine stress in cultured neonatal rat cardiomyocytes. This was abolished by the Pak1-knockdown in Ad-shPak1-infected neonatal rat cardiomyocytes and increased by constitutive overexpression of active Pak1 (Ad-CAPak1). We then implicated activation of serum response factor, a transcriptional factor well known for its vital role in the regulation of cardiogenesis genes in the Pak1-dependent regulation of SERCA2a.
  
  
  CONCLUSIONS
  These findings indicate that Pak1 is required to maintain ventricular Ca(2+) homeostasis and electrophysiological stability and implicate Pak1 as a novel regulator of cardiac SERCA2a through a transcriptional mechanism.
authors.affiliation: From the Department of Pharmacology, University of Oxford, Oxford, United Kingdom (Y.W., D.A.T., M.L.); Institute of Cardiovascular Sciences, Faculty of Medicine and Human Sciences (Y.W., H.T., Y.L., L.D., E.J.C., L.V., M.L.), Faculty of Life Science (X.W.), School of Physics and Astronomy (H.Z.), University of Manchester, Manchester, United Kingdom; Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago (Y.K., R.J.S.); Department of Cardiovascular Diseases, Union Hospital, Huazhong University of Science and Technology, Wuhan, People's Republic of China (Y.S., M.L.); Physiological Laboratory, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom (C.L.-H.H.).
authors.forename: Yanwen
authors.initials: Y
authors.lastname: Wang
authors.affiliation: From the Department of Pharmacology, University of Oxford, Oxford, United Kingdom (Y.W., D.A.T., M.L.); Institute of Cardiovascular Sciences, Faculty of Medicine and Human Sciences (Y.W., H.T., Y.L., L.D., E.J.C., L.V., M.L.), Faculty of Life Science (X.W.), School of Physics and Astronomy (H.Z.), University of Manchester, Manchester, United Kingdom; Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago (Y.K., R.J.S.); Department of Cardiovascular Diseases, Union Hospital, Huazhong University of Science and Technology, Wuhan, People's Republic of China (Y.S., M.L.); Physiological Laboratory, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom (C.L.-H.H.).
authors.forename: Hoyee
authors.initials: H
authors.lastname: Tsui
authors.affiliation: From the Department of Pharmacology, University of Oxford, Oxford, United Kingdom (Y.W., D.A.T., M.L.); Institute of Cardiovascular Sciences, Faculty of Medicine and Human Sciences (Y.W., H.T., Y.L., L.D., E.J.C., L.V., M.L.), Faculty of Life Science (X.W.), School of Physics and Astronomy (H.Z.), University of Manchester, Manchester, United Kingdom; Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago (Y.K., R.J.S.); Department of Cardiovascular Diseases, Union Hospital, Huazhong University of Science and Technology, Wuhan, People's Republic of China (Y.S., M.L.); Physiological Laboratory, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom (C.L.-H.H.).
authors.forename: Yunbo
authors.initials: Y
authors.lastname: Ke
authors.affiliation: From the Department of Pharmacology, University of Oxford, Oxford, United Kingdom (Y.W., D.A.T., M.L.); Institute of Cardiovascular Sciences, Faculty of Medicine and Human Sciences (Y.W., H.T., Y.L., L.D., E.J.C., L.V., M.L.), Faculty of Life Science (X.W.), School of Physics and Astronomy (H.Z.), University of Manchester, Manchester, United Kingdom; Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago (Y.K., R.J.S.); Department of Cardiovascular Diseases, Union Hospital, Huazhong University of Science and Technology, Wuhan, People's Republic of China (Y.S., M.L.); Physiological Laboratory, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom (C.L.-H.H.).
authors.forename: Ying
authors.initials: Y
authors.lastname: Shi
authors.affiliation: From the Department of Pharmacology, University of Oxford, Oxford, United Kingdom (Y.W., D.A.T., M.L.); Institute of Cardiovascular Sciences, Faculty of Medicine and Human Sciences (Y.W., H.T., Y.L., L.D., E.J.C., L.V., M.L.), Faculty of Life Science (X.W.), School of Physics and Astronomy (H.Z.), University of Manchester, Manchester, United Kingdom; Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago (Y.K., R.J.S.); Department of Cardiovascular Diseases, Union Hospital, Huazhong University of Science and Technology, Wuhan, People's Republic of China (Y.S., M.L.); Physiological Laboratory, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom (C.L.-H.H.).
authors.forename: Yatong
authors.initials: Y
authors.lastname: Li
authors.affiliation: From the Department of Pharmacology, University of Oxford, Oxford, United Kingdom (Y.W., D.A.T., M.L.); Institute of Cardiovascular Sciences, Faculty of Medicine and Human Sciences (Y.W., H.T., Y.L., L.D., E.J.C., L.V., M.L.), Faculty of Life Science (X.W.), School of Physics and Astronomy (H.Z.), University of Manchester, Manchester, United Kingdom; Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago (Y.K., R.J.S.); Department of Cardiovascular Diseases, Union Hospital, Huazhong University of Science and Technology, Wuhan, People's Republic of China (Y.S., M.L.); Physiological Laboratory, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom (C.L.-H.H.).
authors.forename: Laura
authors.initials: L
authors.lastname: Davies
authors.affiliation: From the Department of Pharmacology, University of Oxford, Oxford, United Kingdom (Y.W., D.A.T., M.L.); Institute of Cardiovascular Sciences, Faculty of Medicine and Human Sciences (Y.W., H.T., Y.L., L.D., E.J.C., L.V., M.L.), Faculty of Life Science (X.W.), School of Physics and Astronomy (H.Z.), University of Manchester, Manchester, United Kingdom; Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago (Y.K., R.J.S.); Department of Cardiovascular Diseases, Union Hospital, Huazhong University of Science and Technology, Wuhan, People's Republic of China (Y.S., M.L.); Physiological Laboratory, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom (C.L.-H.H.).
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Cartwright
authors.affiliation: From the Department of Pharmacology, University of Oxford, Oxford, United Kingdom (Y.W., D.A.T., M.L.); Institute of Cardiovascular Sciences, Faculty of Medicine and Human Sciences (Y.W., H.T., Y.L., L.D., E.J.C., L.V., M.L.), Faculty of Life Science (X.W.), School of Physics and Astronomy (H.Z.), University of Manchester, Manchester, United Kingdom; Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago (Y.K., R.J.S.); Department of Cardiovascular Diseases, Union Hospital, Huazhong University of Science and Technology, Wuhan, People's Republic of China (Y.S., M.L.); Physiological Laboratory, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom (C.L.-H.H.).
authors.forename: Luigi
authors.initials: L
authors.lastname: Venetucci
authors.affiliation: From the Department of Pharmacology, University of Oxford, Oxford, United Kingdom (Y.W., D.A.T., M.L.); Institute of Cardiovascular Sciences, Faculty of Medicine and Human Sciences (Y.W., H.T., Y.L., L.D., E.J.C., L.V., M.L.), Faculty of Life Science (X.W.), School of Physics and Astronomy (H.Z.), University of Manchester, Manchester, United Kingdom; Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago (Y.K., R.J.S.); Department of Cardiovascular Diseases, Union Hospital, Huazhong University of Science and Technology, Wuhan, People's Republic of China (Y.S., M.L.); Physiological Laboratory, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom (C.L.-H.H.).
authors.forename: Henggui
authors.initials: H
authors.lastname: Zhang
authors.affiliation: From the Department of Pharmacology, University of Oxford, Oxford, United Kingdom (Y.W., D.A.T., M.L.); Institute of Cardiovascular Sciences, Faculty of Medicine and Human Sciences (Y.W., H.T., Y.L., L.D., E.J.C., L.V., M.L.), Faculty of Life Science (X.W.), School of Physics and Astronomy (H.Z.), University of Manchester, Manchester, United Kingdom; Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago (Y.K., R.J.S.); Department of Cardiovascular Diseases, Union Hospital, Huazhong University of Science and Technology, Wuhan, People's Republic of China (Y.S., M.L.); Physiological Laboratory, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom (C.L.-H.H.).
authors.forename: Derek A
authors.initials: DA
authors.lastname: Terrar
authors.affiliation: From the Department of Pharmacology, University of Oxford, Oxford, United Kingdom (Y.W., D.A.T., M.L.); Institute of Cardiovascular Sciences, Faculty of Medicine and Human Sciences (Y.W., H.T., Y.L., L.D., E.J.C., L.V., M.L.), Faculty of Life Science (X.W.), School of Physics and Astronomy (H.Z.), University of Manchester, Manchester, United Kingdom; Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago (Y.K., R.J.S.); Department of Cardiovascular Diseases, Union Hospital, Huazhong University of Science and Technology, Wuhan, People's Republic of China (Y.S., M.L.); Physiological Laboratory, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom (C.L.-H.H.).
authors.forename: Christopher L-H
authors.initials: CL
authors.lastname: Huang
authors.affiliation: From the Department of Pharmacology, University of Oxford, Oxford, United Kingdom (Y.W., D.A.T., M.L.); Institute of Cardiovascular Sciences, Faculty of Medicine and Human Sciences (Y.W., H.T., Y.L., L.D., E.J.C., L.V., M.L.), Faculty of Life Science (X.W.), School of Physics and Astronomy (H.Z.), University of Manchester, Manchester, United Kingdom; Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago (Y.K., R.J.S.); Department of Cardiovascular Diseases, Union Hospital, Huazhong University of Science and Technology, Wuhan, People's Republic of China (Y.S., M.L.); Physiological Laboratory, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom (C.L.-H.H.).
authors.forename: R John
authors.initials: RJ
authors.lastname: Solaro
authors.affiliation: From the Department of Pharmacology, University of Oxford, Oxford, United Kingdom (Y.W., D.A.T., M.L.); Institute of Cardiovascular Sciences, Faculty of Medicine and Human Sciences (Y.W., H.T., Y.L., L.D., E.J.C., L.V., M.L.), Faculty of Life Science (X.W.), School of Physics and Astronomy (H.Z.), University of Manchester, Manchester, United Kingdom; Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago (Y.K., R.J.S.); Department of Cardiovascular Diseases, Union Hospital, Huazhong University of Science and Technology, Wuhan, People's Republic of China (Y.S., M.L.); Physiological Laboratory, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom (C.L.-H.H.). ming.lei@pharm.ox.ac.uk xing.wang@manchester.ac.uk.
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.affiliation: From the Department of Pharmacology, University of Oxford, Oxford, United Kingdom (Y.W., D.A.T., M.L.); Institute of Cardiovascular Sciences, Faculty of Medicine and Human Sciences (Y.W., H.T., Y.L., L.D., E.J.C., L.V., M.L.), Faculty of Life Science (X.W.), School of Physics and Astronomy (H.Z.), University of Manchester, Manchester, United Kingdom; Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago (Y.K., R.J.S.); Department of Cardiovascular Diseases, Union Hospital, Huazhong University of Science and Technology, Wuhan, People's Republic of China (Y.S., M.L.); Physiological Laboratory, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom (C.L.-H.H.). ming.lei@pharm.ox.ac.uk xing.wang@manchester.ac.uk.
authors.forename: Ming
authors.initials: M
authors.lastname: Lei
mesh_terms: D000318:Adrenergic beta-Agonists; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002304:Cardiac Pacing, Artificial; D006332:Cardiomegaly / Q000201:enzymology; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004562:Electrocardiography; D015971:Gene Expression Regulation, Enzymologic; D006352:Heart Ventricles / Q000201:enzymology* / Q000503:physiopathology; D006706:Homeostasis; D007545:Isoproterenol; D008297:Male; D018345:Mice, Knockout; D032383:Myocytes, Cardiac / Q000201:enzymology*; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D012307:Risk Factors; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000235:genetics / Q000378:metabolism*; D017180:Tachycardia, Ventricular / Q000139:chemically induced / Q000201:enzymology* / Q000235:genetics / Q000503:physiopathology; D013997:Time Factors; D014158:Transcription, Genetic; D014162:Transfection; D054462:p21-Activated Kinases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
chemical_list: D000318:Adrenergic beta-Agonists; C506948:Atp2a2 protein, rat; D012333:RNA, Messenger; C515905:Pak1 protein, mouse; C515906:Pak1 protein, rat; D054462:p21-Activated Kinases; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; C506947:Atp2a2 protein, mouse; D007545:Isoproterenol; D002118:Calcium
keywords: P21-activated kinases; arrhythmias, cardiac; calcium signaling; sarcoplasmic reticulum Ca2+ ATPases