Phosphorylation of cMyBP-C affects contractile mechanisms in a site-specific manner

Li Wang; Xiang Ji; David Barefield; Sakthivel Sadayappan; Masakata Kawai

doi:10.1016/j.bpj.2014.01.029

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Phosphorylation of cMyBP-C affects contractile mechanisms in a site-specific manner

Journal article

Open access

Peer reviewed

Phosphorylation of cMyBP-C affects contractile mechanisms in a site-specific manner

Li Wang, Xiang Ji, David Barefield, Sakthivel Sadayappan and Masakata Kawai

Biophysical journal, Vol.106(5), pp.1112-1122

03/04/2014

DOI: 10.1016/j.bpj.2014.01.029

PMCID: PMC4026776

PMID: 24606935

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Abstract

Cardiac myosin binding protein-C (cMyBP-C) is a cardiac-specific, thick-filament regulatory protein that is differentially phosphorylated at Ser(273), Ser(282), and Ser(302) by various kinases and modulates contraction. In this study, phosphorylation-site-specific effects of cMyBP-C on myocardial contractility and cross-bridge kinetics were studied by sinusoidal analysis in papillary and trabecular muscle fibers isolated from t/t (cMyBP-C-null) mice and in their counterparts in which cMyBP-C contains the ADA (Ala(273)-Asp(282)-Ala(302)), DAD (Asp(273)-Ala(282)-Asp(302)), and SAS (Ser(273)-Ala(282)-Ser(302)) mutations; the results were compared to those from mice expressing the wild-type (WT) transgene on the t/t background. Under standard activating conditions, DAD fibers showed significant decreases in tension (~50%), stiffness, the fast apparent rate constant 2πc, and its magnitude C, as well as its magnitude H, but an increase in the medium rate constant 2πb, with respect to WT. The t/t fibers showed a smaller drop in stiffness and a significant decrease in 2πc that can be explained by isoform shift of myosin heavy chain. In the pCa-tension study using the 8 mM phosphate (Pi) solution, there was hardly any difference in Ca(2+) sensitivity (pCa50) and cooperativity (nH) between the mutant and WT samples. However, in the solutions without Pi, DAD showed increased nH and slightly decreased pCa50. We infer from these observations that the nonphosphorylatable residue 282 combined with phosphomimetic residues Asp(273) and/or Asp(302) (in DAD) is detrimental to cardiomyocytes by lowering isometric tension and altering cross-bridge kinetics with decreased 2πc and increased 2πb. In contrast, a single change of residue 282 to nonphosphorylatable Ala (SAS), or to phosphomimetic Asps together with the changes of residues 273 and 302 to nonphosphorylatable Ala (ADA) causes minute changes in fiber mechanics.

Animals

Binding Sites

Calcium - metabolism

Carrier Proteins - chemistry

Carrier Proteins - genetics

Carrier Proteins - metabolism

Female

Gene Expression Regulation

Hydrogen-Ion Concentration

Kinetics

Male

Mice

Mutation

Myocardial Contraction

Myosins - metabolism

Phosphorylation

Protein Isoforms - metabolism

Stress, Mechanical

Details

Title: Subtitle: Phosphorylation of cMyBP-C affects contractile mechanisms in a site-specific manner
Creators: Li Wang - Soochow University
Xiang Ji - Loyola University Chicago
David Barefield - Loyola University Chicago
Sakthivel Sadayappan - Loyola University Chicago
Masakata Kawai - Roy J. and Lucille A. Carver College of Medicine
Resource Type: Journal article
Publication Details: Biophysical journal, Vol.106(5), pp.1112-1122
DOI: 10.1016/j.bpj.2014.01.029
PMID: 24606935
PMCID: PMC4026776
NLM abbreviation: Biophys J
ISSN: 0006-3495
eISSN: 1542-0086
Grant note: R01 HL070041 / NHLBI NIH HHS R01 HL105826 / NHLBI NIH HHS K02HL114749 / NHLBI NIH HHS R01HL105826 / NHLBI NIH HHS K02 HL114749 / NHLBI NIH HHS HL070041 / NHLBI NIH HHS
Language: English
Date published: 03/04/2014
Academic Unit: Anatomy and Cell Biology; Internal Medicine
Record Identifier: 9984284341502771

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