Increased Ca2+-sensitivity of the contractile apparatus in end-stage human heart failure results from altered phosphorylation of contractile proteins
J. van der Velden,Zoltán Papp,R. Zaremba,Nicky M. Boontje,J. W. de Jong,V. J. Owen,P. B.J. Burton,P. Goldmann,Kornelia Jaquet,Ger J.M. Stienen +9 more
TLDR
The increased Ca(2+)-responsiveness of the contractile apparatus in end-stage failing human hearts cannot be explained by a shift in contractile protein isoforms, but results from the complex interplay between changes in the phosphorylation status of MLC-2 and TnI.Abstract:
Objective: The alterations in contractile proteins underlying enhanced Ca2+-sensitivity of the contractile apparatus in end-stage failing human myocardium are still not resolved. In the present study an attempt was made to reveal to what extent protein alterations contribute to the increased Ca2+-responsiveness in human heart failure. Methods: Isometric force and its Ca2+-sensitivity were studied in single left ventricular myocytes from non-failing donor (n=6) and end-stage failing (n=10) hearts. To elucidate which protein alterations contribute to the increased Ca2+-responsiveness isoform composition and phosphorylation status of contractile proteins were analysed by one- and two-dimensional gel electrophoresis and Western immunoblotting. Results: Maximal tension did not differ between myocytes obtained from donor and failing hearts, while Ca2+-sensitivity of the contractile apparatus (pCa50) was significantly higher in failing myocardium (ΔpCa50=0.17). Protein analysis indicated that neither re-expression of atrial light chain 1 and fetal troponin T (TnT) nor degradation of myosin light chains and troponin I (TnI) are responsible for the observed increase in Ca2+-responsiveness. An inverse correlation was found between pCa50 and percentage of phosphorylated myosin light chain 2 (MLC-2), while phosphorylation of MLC-1 and TnT did not differ between donor and failing hearts. Incubation of myocytes with protein kinase A decreased Ca2+-sensitivity to a larger extent in failing (ΔpCa50=0.20) than in donor (ΔpCa50=0.03) myocytes, abolishing the difference in Ca2+-responsiveness. An increased percentage of dephosphorylated TnI was found in failing hearts, which significantly correlated with the enhanced Ca2+-responsiveness. Conclusions: The increased Ca2+-responsiveness of the contractile apparatus in end-stage failing human hearts cannot be explained by a shift in contractile protein isoforms, but results from the complex interplay between changes in the phosphorylation status of MLC-2 and TnI.read more
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Cardiomyocyte Stiffness in Diastolic Heart Failure
Attila Borbély,Jolanda van der Velden,Zoltán Papp,Jean G.F. Bronzwaer,István Édes,Ger J.M. Stienen,Walter Paulus +6 more
TL;DR: DHF patients had stiffer cardiomyocytes, as evident from a higher Fpassive at the same sarcomere length, which suggests that reduced phosphorylation of sarcomeric proteins is involved in DHF.
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What Mechanisms Underlie Diastolic Dysfunction in Heart Failure
TL;DR: New insights from basic and clinical research are helping define the regulators of diastolic dysfunction and illuminate novel targets for treatment, and this review puts these developments into perspective with the major aim of highlighting current knowledge gaps and controversies.
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Regulation of cardiac contractile function by troponin I phosphorylation
TL;DR: Recent advances in understanding the mechanisms of cTnI modification by protein kinases and the consequent functional effects both under physiological conditions and in pathophysiological settings are focused on.
Journal ArticleDOI
Hypophosphorylation of the Stiff N2B Titin Isoform Raises Cardiomyocyte Resting Tension in Failing Human Myocardium
Attila Borbély,Inês Falcão-Pires,Inês Falcão-Pires,Loek van Heerebeek,Nazha Hamdani,István Édes,Cristina Gavina,Adelino F. Leite-Moreira,Jean G.F. Bronzwaer,Zoltán Papp,Jolanda van der Velden,Ger J.M. Stienen,Walter Paulus +12 more
TL;DR: In this paper, the authors found that a shift in titin isoform expression from N2BA to N2B isoform, lower overall phosphorylation of titin, and a shift of titins from N 2B to N 2BA isoform can raise the diastolic stiffness of failing myocardium and elevated resting tension of cardiomyocytes.
Journal ArticleDOI
Cardiac Myosin-Binding Protein C Mutations and Hypertrophic Cardiomyopathy : Haploinsufficiency, Deranged Phosphorylation, and Cardiomyocyte Dysfunction
Sabine J. van Dijk,Dennis Dooijes,Cris dos Remedios,Michelle Michels,Jos M. J. Lamers,Saul Winegrad,Saskia Schlossarek,Lucie Carrier,Folkert J. Ten Cate,Ger J.M. Stienen,Jolanda van der Velden +10 more
TL;DR: The frameshift MYBPC3 mutations cause haploinsufficiency, deranged phosphorylation of contractile proteins, and reduced maximal force-generating capacity of cardiomyocytes, and the enhanced Ca2+ sensitivity in MYB PC3mut is due to hypophosphorylation in troponin I secondary to mutation-induced dysfunction.
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