title: Altered myocyte contractility and calcium homeostasis in alpha-myosin heavy chain point mutations linked to familial dilated cardiomyopathy.
abstract: Mutations in the human cardiac motor protein beta-myosin heavy chain (βMHC) have been long recognized as a cause of familial hypertrophic cardiomyopathy. Recently, mutations (P830L and A1004S) in the less abundant but faster isoform alpha-myosin heavy chain (αMHC) have been linked to dilated cardiomyopathy (DCM). In this study, we sought to determine the cellular contractile phenotype associated with these point mutations. Ventricular myocytes were isolated from 2 month male Sprague Dawley rats. Cells were cultured in M199 media and infected with recombinant adenovirus containing the P830L or the A1004S mutant human αMHC at a MOI of 500 for 18 h. Uninfected cells (UI), human βMHC (MOI 500, 18 h), and human αMHC (MOI 500, 18 h) were used as controls. Cells were loaded with fura-2 (1 μM, 15 min) after 48 h. Sarcomere shortening and calcium transients were recorded in CO2buffered M199 media (36°±1 C) with and without 10 nM isoproterenol (Iso). The A1004S mutation resulted in decreased peak sarcomere shortening while P830L demonstrated near normal shortening kinetics at baseline. In the presence of Iso, the A1004S sarcomere shortening was identical to the βMHC shortening while the P830L was identical to the αMHC control. All experimental groups had identical calcium transients. Despite a shared association with DCM, the P830L and A1004S αMHC mutations alter myocyte contractility in completely different ways while at the same preserving peak intracellular calcium.
authors.affiliation: Department of Pediatric Cardiac Surgery, UH Hospitals Cleveland, Cleveland, OH 44106, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Klos
authors.affiliation: Department of Internal Medicine, Cardiovascular Medicine, Center for Arrhythmia Research, University of Michigan, Ann Arbor, MI 48108, USA.
authors.forename: Lakshmi
authors.initials: L
authors.lastname: Mundada
authors.affiliation: Department of Medicine, University of California, San Diego, CA 92103, USA.
authors.forename: Indroneal
authors.initials: I
authors.lastname: Banerjee
authors.affiliation: Department of Pediatric Cardiac Surgery, UH Hospitals Cleveland, Cleveland, OH 44106, USA.
authors.forename: Sherry
authors.initials: S
authors.lastname: Morgenstern
authors.affiliation: Department of Medicine, University of California, San Diego, CA 92103, USA.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Myers
authors.affiliation: Department of Medicine, University of California, San Diego, CA 92103, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Leone
authors.affiliation: Department of Medicine, University of California, San Diego, CA 92103, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Kleid
authors.affiliation: Department of Internal Medicine, Cardiovascular Medicine, Center for Arrhythmia Research, University of Michigan, Ann Arbor, MI 48108, USA.
authors.forename: Todd
authors.initials: T
authors.lastname: Herron
authors.affiliation: Department of Pediatric Cardiac Surgery, UH Hospitals Cleveland, Cleveland, OH 44106, USA. Electronic address: Eric.Devaney@uhhospitals.org.
authors.forename: Eric
authors.initials: E
authors.lastname: Devaney
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002311:Cardiomyopathy, Dilated; D006706:Homeostasis; D006801:Humans; D006984:Hypertrophy; D007545:Isoproterenol / Q000737:chemistry; D007700:Kinetics; D008297:Male; D032342:Muscle Cells / Q000166:cytology*; D016296:Mutagenesis; D009200:Myocardial Contraction; D032383:Myocytes, Cardiac / Q000378:metabolism; D018995:Myosin Heavy Chains / Q000235:genetics* / Q000378:metabolism; D010641:Phenotype; D017354:Point Mutation; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000378:metabolism; D012518:Sarcomeres / Q000378:metabolism; D024723:Ventricular Myosins / Q000378:metabolism
chemical_list: D011994:Recombinant Proteins; D024723:Ventricular Myosins; D018995:Myosin Heavy Chains; D007545:Isoproterenol; D002118:Calcium
keywords: Alpha myosin heavy chain (αMHC); Beta myosin heavy chain (βMHC); Dilated cardiomyopathy (DCM); Hypertrophic cardiomyopathy (HCM); Isoproterenol (Iso)