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 language | English |
|---|---|
| Pages (from-to) | 17371-17379 |
| Number of pages | 9 |
| Journal | Journal of Biological Chemistry |
| Volume | 285 |
| Issue number | 23 |
| DOIs | |
| State | Published - Jun 4 2010 |
| Externally published | Yes |
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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 journal › Article
}
TY - JOUR
T1 - A dilated cardiomyopathy troponin C mutation lowers contractile force by reducing strong myosin-actin binding
AU - Dweck, David
AU - Reynaldo, Daniel P.
AU - Pinto, Jose R.
AU - Potter, James D.
PY - 2010/6/4
Y1 - 2010/6/4
N2 - 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.
AB - 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.
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U2 - 10.1074/jbc.M109.064105
DO - 10.1074/jbc.M109.064105
M3 - Article
VL - 285
SP - 17371
EP - 17379
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 0021-9258
IS - 23
ER -