Restrictive cardiomyopathy Troponin-I R145W mutation does not perturb myofilament length dependent activation in human cardiac sarcomeres Journal Article

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Authors: Dvornikov, A. V.; Smolin, N; Zhang, M; Martin, J. L.; Robia, S. L.; de Tombe, P. P.
Article Title: Restrictive cardiomyopathy Troponin-I R145W mutation does not perturb myofilament length dependent activation in human cardiac sarcomeres
Abstract: The cardiac Troponin cTnI-R145W mutation is associated with restrictive cardiomyopathy (RCM). Recent evidence suggests that this mutation induces perturbed myofilament length dependent activation (LDA) under conditions of maximal protein kinase A (PKA) stimulation. Some cardiac disease causing mutations, however, have been associated with a blunted response to PKA mediated phosphorylation; whether this includes LDA is unknown. Endogenous Troponin was exchanged in isolated skinned human myocardium for recombinant troponin containing either cTnI: R145W, PKA/PKC phosphomimetic charge mutations (S23D/S24D; T143E), or various combinations thereof. Myofilament Ca2+ sensitivity of force, tension-cost, LDA, and single myofibril activation/relaxation parameters were measured. Our results show that both R145W and T143E uncouple the impact of S23D/S24D phosphomimetic on myofilament function, including LDA. Molecular dynamics simulations revealed a marked reduction in interactions between Helix-C of cTnC (residues 56,59,63), and cTnI (residue 145) in the presence of either cTnI-RCM mutation or cTnI-PKC phosphomimetic. These results suggest that the RCM associated cTnI-R145W mutation induces a permanent structural state that is similar, yet more extensive, to that induced by PKC mediated phosphorylation of cTnI-T143. We suggest that this structural conformational change induces an increase in myofilament Ca2+ sensitivity and, moreover, uncoupling from the impact of phosphorylation of cTnI mediated by PKA at the S23/S24 target sites. The R145W RCM mutation by itself, however, does not impact LDA. These perturbed biophysical and biochemical myofilament properties are likely to significantly contribute to the diastolic cardiac pump dysfunction that is seen in patients suffering from a restrictive cardiomyopathy that is associated with the cTnI-R145W mutation.
Journal Title: The Journal of biological chemistry
ISSN: 1083-351X; 0021-9258
Publisher: The American Society for Biochemistry and Molecular Biology  
Journal Place: United States
Date Published: 2016
Language: ENG
DOI/URL:

jbc.M116.746172
Notes: LR: 20160825; CI: Copyright (c) 2016; JID: 2985121R; OTO: NOTNLM; 2016/06/30 [received]; 2016/08/24 [accepted]; aheadofprint