Hypercontractile properties of cardiac muscle fibers in a knock-in mouse model of cardiac myosin-binding protein-C

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Item Type:	Article
Title:	Hypercontractile properties of cardiac muscle fibers in a knock-in mouse model of cardiac myosin-binding protein-C
Creators Name:	Witt, C.C., Gerull, B., Davies, M.J., Centner, T., Linke, W.A. and Thierfelder, L.
Abstract:	Myosin-binding protein-C (MyBP-C) is a component of all striated-muscle sarcomeres, with a well established structural role and a possible function for force regulation. Multiple mutations within the gene for cardiac MyBP-C, one of three known isoforms, have been linked to familial hypertrophic cardiomyopathy. Here we generated a knock-in mouse model that carries N-terminal-shortened cardiac MyBP-C. The mutant protein was designed to have a similar size as the skeletal MyBP-C isoforms, whereas known myosin and titin binding sites as well as the phosphorylatable MyBP-C motif were not altered. We have shown that mutant cardiac MyBP-C is readily incorporated into the sarcomeres of both heterozygous and homozygous animals and can still be phosphorylated by cAMP-dependent protein kinase. Although histological characterization of wild-type and mutant hearts did not reveal obvious differences in phenotype, left ventricular fibers from homozygous mutant mice exhibited an increased Ca2+ sensitivity of force development, particularly at lower Ca 2+ concentrations, whereas maximal active force levels remained unchanged. The results allow us to propose a model of how cMyBP-C may affect myosin-head mobility and to rationalize why N-terminal mutations of the protein in some cases of familial hypertrophic cardiomyopathy could lead to a hypercontractile state.
Keywords:	Biological Models, Calcium, Carrier Proteins, Cyclic AMP-Dependent Protein Kinases, Gene Targeting, Heart, Messenger RNA, Muscle Fibers, Myocardial Contraction, Myocardium, Phosphorylation, Sequence Deletion, Animals, Mice
Source:	Journal of Biological Chemistry
ISSN:	0021-9258
Publisher:	American Society for Biochemistry and Molecular Biology
Volume:	276
Number:	7
Page Range:	5353-5359
Date:	1 January 2001
PubMed:	View item in PubMed

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