A dilated cardiomyopathy troponin C mutation lowers contractile force by reducing strong myosin-actin binding

David Dweck, Daniel P. Reynaldo, Jose R. Pinto, James D. Potter

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

In this study we explore the mechanisms by which a double mutation (E59D/D75Y) in cardiac troponin C (CTnC) associated with dilated cardiomyopathy reduces the Ca2+-activated maximal tension of cardiac muscle. Studying the single mutants (i.e. E59D or D75Y) indicates that D75Y, but not E59D, causes a reduction in the calcium affinity of CTnC in troponin complex, regulated thin filaments (RTF), and the Ca2+ sensitivity of contraction and ATPase in cardiac muscle preparations. However, both D75Y and E59D are required to reduce the actomyosin ATPase activity and maximal force in muscle fibers, indicating that E59D enhances the effects of D75Y. Part of the reduction in force/ATPase may be due to a defect in the interactions between CTnC and cardiac troponin T, which are known to be necessary for ATPase activation. An additional mechanism for the reduction in force/ATPase comes from measurements of the binding stoichiometry of myosin subfragment-1 (S-1) to the RTF. Using wild type RTFs, 4.8 mol S-1 was bound per mol filament (seven actins), whereas with E59D/D75Y RTFs, the number of binding sites was reduced by ∼23% to 3.7. Altogether, these results suggest that the reduction in force and ATPase activation is possibly due to a thin filament conformation that promotes fewer accessible S-1-binding sites. In the absence of any family segregation data, the functional results presented here support the concept that this is likely a dilated cardiomyopathy-causing mutation.

Original languageEnglish
Pages (from-to)17371-17379
Number of pages9
JournalJournal of Biological Chemistry
Volume285
Issue number23
DOIs
StatePublished - Jun 4 2010
Externally publishedYes

Fingerprint

Troponin C
Dilated Cardiomyopathy
Myosins
Adenosine Triphosphatases
Actins
Mutation
Muscle
Myocardium
Chemical activation
Binding Sites
Myosin Subfragments
Troponin T
Troponin
Actin Cytoskeleton
Stoichiometry
Conformations
Calcium
Muscles
Defects
Fibers

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Molecular Biology

Cite this

A dilated cardiomyopathy troponin C mutation lowers contractile force by reducing strong myosin-actin binding. / Dweck, David; Reynaldo, Daniel P.; Pinto, Jose R.; Potter, James D.

In: Journal of Biological Chemistry, Vol. 285, No. 23, 04.06.2010, p. 17371-17379.

Research output: Contribution to journalArticle

Dweck, David ; Reynaldo, Daniel P. ; Pinto, Jose R. ; Potter, James D. / A dilated cardiomyopathy troponin C mutation lowers contractile force by reducing strong myosin-actin binding. In: Journal of Biological Chemistry. 2010 ; Vol. 285, No. 23. pp. 17371-17379.
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