title: Molecular Determinants of Calpain-dependent Cleavage of Junctophilin-2 Protein in Cardiomyocytes.
abstract: Junctophilin-2 (JP2), a membrane-binding protein that provides a structural bridge between the plasmalemma and sarcoplasmic reticulum, is essential for precise Ca(2+)-induced Ca(2+) release during excitation-contraction coupling in cardiomyocytes. In animal and human failing hearts, expression of JP2 is decreased markedly, but the molecular mechanisms underlying JP2 down-regulation remain incompletely defined. In mouse hearts, ischemia/reperfusion injury resulted in acute JP2 down-regulation, which was attenuated by pretreatment with the calpain inhibitor MDL-28170 or by transgenic overexpression of calpastatin, an endogenous calpain inhibitor. Using a combination of computational analysis to predict calpain cleavage sites and in vitro calpain proteolysis reactions, we identified four putative calpain cleavage sites within JP2 with three N-terminal and one C-terminal cleavage sites. Mutagenesis defined the C-terminal region of JP2 as the predominant calpain cleavage site. Exogenous expression of putative JP2 cleavage fragments was not sufficient to rescue Ca(2+) handling in JP2-deficient cardiomyocytes, indicating that cleaved JP2 is non-functional for normal Ca(2+)-induced Ca(2+) release. These data provide new molecular insights into the posttranslational regulatory mechanisms of JP2 in cardiac diseases.
authors.affiliation: Division of Cardiovascular Medicine, Department of Internal Medicine and François M. Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242.
authors.forename: Ang
authors.initials: A
authors.lastname: Guo
authors.affiliation: Division of Cardiovascular Medicine, Department of Internal Medicine and François M. Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242.
authors.forename: Duane
authors.initials: D
authors.lastname: Hall
authors.affiliation: Division of Cardiovascular Medicine, Department of Internal Medicine and François M. Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242.
authors.forename: Caimei
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Departments of Medicine and Pathology, University of Western Ontario, London, Ontario N6A 4G5, Canada.
authors.forename: Tianqing
authors.initials: T
authors.lastname: Peng
authors.affiliation: Division of Cardiovascular Surgery, Mayo Clinic, Rochester, Minnesota 55905.
authors.forename: Jordan D
authors.initials: JD
authors.lastname: Miller
authors.affiliation: Division of Cardiovascular Medicine, Department of Internal Medicine and François M. Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242.
authors.forename: William
authors.initials: W
authors.lastname: Kutschke
authors.affiliation: Division of Cardiovascular Medicine, Department of Internal Medicine and François M. Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242.
authors.forename: Chad E
authors.initials: CE
authors.lastname: Grueter
authors.affiliation: Division of Cardiovascular Medicine, Department of Internal Medicine and François M. Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242.
authors.forename: Frances L
authors.initials: FL
authors.lastname: Johnson
authors.affiliation: Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York 11794.
authors.forename: Richard Z
authors.initials: RZ
authors.lastname: Lin
authors.affiliation: Division of Cardiovascular Medicine, Department of Internal Medicine and François M. Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242. Electronic address: long-sheng-song@uiowa.edu.
authors.forename: Long-Sheng
authors.initials: LS
authors.lastname: Song
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002154:Calpain / Q000378:metabolism*; D002478:Cells, Cultured; D015536:Down-Regulation; D056966:Excitation Contraction Coupling; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D015428:Myocardial Reperfusion Injury / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000378:metabolism*; D059748:Proteolysis
chemical_list: D008565:Membrane Proteins; C412507:junctophilin; D002154:Calpain; D002118:Calcium
keywords: calcium; calpain; excitation-contraction coupling (E-C coupling); heart; junctophilin-2; proteolysis