Endothelin as a Regulator of Phosphorylation of cMyBP-C

Abstract

The effect of endothelin, a powerful vasoconstrictor and enhancer of cardiac contractility, and hypoxia on the degree of phosphorylation of cardiac myosin binding protein C (cMyBP-C) has been studied in cardiac trabeculae isolated from rat hearts. Endothelin in concentrations that increase contractility increases phosphorylation in a dose-dependent fashion. Increase in sarcomere length itself increases phosphorylation and enhances the effect of endothelin on phosphorylation. Hypoxia decreases phosphorylation in a duration-dependent manner and inhibits the ability of endothelin to produce phosphorylation of MyBP-C. These results suggest that phosphorylation of cMyBP-C may be a molecular component of the vascular endothelial cell - cardiac myocyte cross-talk. Coupled with already published work, the results also suggest that cMyBP-C phosphorylation may contribute to the regulation of the turnover of myofibrillar proteins.