Protein kinase C α and ε phosphorylation of troponin and myosin binding protein C reduce Ca2+ sensitivity in human myocardium

被引：0
作者：
Viola Kooij
Nicky Boontje
Ruud Zaremba
Kornelia Jaquet
Cris dos Remedios
Ger J. M. Stienen
Jolanda van der Velden
机构：
[1] VU University Medical Center,Laboratory for Physiology, Institute for Cardiovascular Research
[2] Kliniken der Ruhr-Universität,Forschungslabor Molekulare Kardiologie, St. Josef Hospital/Bergmannsheil
[3] The University of Sydney,Muscle Research Unit, Institute for Biomedical Research
来源：
Basic Research in Cardiology | 2010年 / 105卷
关键词：
Protein kinase C; Cardiac; Heart failure; Myofilament function; Contractile proteins; Phosphorylation;
D O I：
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学科分类号：
摘要：
Previous studies indicated that the increase in protein kinase C (PKC)-mediated myofilament protein phosphorylation observed in failing myocardium might be detrimental for contractile function. This study was designed to reveal and compare the effects of PKCα- and PKCε-mediated phosphorylation on myofilament function in human myocardium. Isometric force was measured at different [Ca2+] in single permeabilized cardiomyocytes from failing human left ventricular tissue. Activated PKCα and PKCε equally reduced Ca2+ sensitivity in failing cardiomyocytes (ΔpCa50 = 0.08 ± 0.01). Both PKC isoforms increased phosphorylation of troponin I- (cTnI) and myosin binding protein C (cMyBP-C) in failing cardiomyocytes. Subsequent incubation of failing cardiomyocytes with the catalytic subunit of protein kinase A (PKA) resulted in a further reduction in Ca2+ sensitivity, indicating that the effects of both PKC isoforms were not caused by cross-phosphorylation of PKA sites. Both isozymes showed no effects on maximal force and only PKCα resulted in a modest significant reduction in passive force. Effects of PKCα were only minor in donor cardiomyocytes, presumably because of already saturated cTnI and cMyBP-C phosphorylation levels. Donor tissue could therefore be used as a tool to reveal the functional effects of troponin T (cTnT) phosphorylation by PKCα. Massive dephosphorylation of cTnT with alkaline phosphatase increased Ca2+ sensitivity. Subsequently, PKCα treatment of donor cardiomyocytes reduced Ca2+ sensitivity (ΔpCa50 = 0.08 ± 0.02) and solely increased phosphorylation of cTnT, but did not affect maximal and passive force. PKCα- and PKCε-mediated phosphorylation of cMyBP-C and cTnI as well as cTnT decrease myofilament Ca2+ sensitivity and may thereby reduce contractility and enhance relaxation of human myocardium.
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页码：289 / 300
页数：11
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