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The homozygous K280N troponin T mutation alters cross-bridge kinetics and energetics in human HCM

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Title: The homozygous K280N troponin T mutation alters cross-bridge kinetics and energetics in human HCM
Authors: Piroddi, N
Witjas-Paalberends, ER
Ferrara, C
Ferrantini, C
Vitale, G
Scellini, B
Wijnker, PJM
Sequiera, V
Dooijes, D
Dos Remedios, C
Schlossarek, S
Leung, MC
Messer, A
Ward, DG
Biggeri, A
Tesi, C
Carrier, L
Redwood, CS
Marston, SB
Van der Velden, J
Poggesi, C
Item Type: Journal Article
Abstract: Hypertrophic cardiomyopathy (HCM) is a genetic form of left ventricular hypertrophy, primarily caused by mutations in sarcomere proteins. The cardiac remodeling that occurs as the disease develops can mask the pathogenic impact of the mutation. Here, to discriminate between mutation-induced and disease-related changes in myofilament function, we investigate the pathogenic mechanisms underlying HCM in a patient carrying a homozygous mutation (K280N) in the cardiac troponin T gene (TNNT2), which results in 100% mutant cardiac troponin T. We examine sarcomere mechanics and energetics in K280N-isolated myofibrils and demembranated muscle strips, before and after replacement of the endogenous troponin. We also compare these data to those of control preparations from donor hearts, aortic stenosis patients (LVHao), and HCM patients negative for sarcomeric protein mutations (HCMsmn). The rate constant of tension generation following maximal Ca2+ activation (kACT) and the rate constant of isometric relaxation (slow kREL) are markedly faster in K280N myofibrils than in all control groups. Simultaneous measurements of maximal isometric ATPase activity and Ca2+-activated tension in demembranated muscle strips also demonstrate that the energy cost of tension generation is higher in the K280N than in all controls. Replacement of mutant protein by exchange with wild-type troponin in the K280N preparations reduces kACT, slow kREL, and tension cost close to control values. In donor myofibrils and HCMsmn demembranated strips, replacement of endogenous troponin with troponin containing the K280N mutant increases kACT, slow kREL, and tension cost. The K280N TNNT2 mutation directly alters the apparent cross-bridge kinetics and impairs sarcomere energetics. This result supports the hypothesis that inefficient ATP utilization by myofilaments plays a central role in the pathogenesis of the disease.
Issue Date: 7-Jan-2019
Date of Acceptance: 29-Nov-2018
URI: http://hdl.handle.net/10044/1/68175
DOI: https://dx.doi.org/10.1085/jgp.201812160
ISSN: 0022-1295
Publisher: Rockefeller University Press
Start Page: 18
End Page: 29
Journal / Book Title: Journal of General Physiology
Volume: 151
Issue: 1
Copyright Statement: © 2018 Piroddi et al. http://www.rupress.org/terms/https://creativecommons.org/licenses/by-nc-sa/4.0/This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms/). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 International license, as described at https://creativecommons.org/licenses/by-nc-sa/4.0/).
Keywords: Science & Technology
Life Sciences & Biomedicine
Physiology
HUMAN HYPERTROPHIC CARDIOMYOPATHY
LENGTH-DEPENDENT ACTIVATION
HUMAN CARDIAC TROPONIN
PROTEIN-KINASE-A
MECHANICAL PERFORMANCE
TENSION GENERATION
BETA-MYOSIN
MUTANT
PHOSPHORYLATION
RELAXATION
0606 Physiology
1116 Medical Physiology
Publication Status: Published
Article Number: 18
Online Publication Date: 2018-12-21
Appears in Collections:National Heart and Lung Institute
Faculty of Medicine



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