CaMKII in addition to MLCK contributes to phosphorylation of regulatory light chain in cardiomyocytes

Biochemical and Biophysical Research Communications
Hilde EikemoJan-Bjørn Osnes

Abstract

The aim was to identify kinase activities involved in the phosphorylation of regulatory light chain (RLC) in situ in cardiomyocytes. In electrically stimulated rat cardiomyocytes, phosphatase inhibition by calyculin A unmasked kinase activities evoking an increase of phosphorylated RLC (P-RLC) from about 16% to about 80% after 80 min. The phosphorylation rate in cardiomyocytes was reduced by about 40% by the myosin light chain kinase (MLCK) inhibitor, ML-7. In rat ventricular muscle strips, calyculin A induced a positive inotropic effect that correlated with P-RLC levels. The inotropic effect and P-RLC elevation were abolished by ML-7 treatment. The kinase activities phosphorylating RLC in cardiomyocytes were reduced by about 60% by the non-selective kinase inhibitor staurosporine and by about 50% by the calmodulin antagonist W7. W7 eliminated the inhibitory effect of ML-7, suggesting that the cardiac MLCK is Ca(2+)/calmodulin (CaM)-dependent. The CaM-dependent kinase II (CaMKII) inhibitor KN-93 attenuated the calyculin A-induced RLC phosphorylation by about 40%, indicating a contribution from CaMKII. The residual phosphorylation in the presence of W7 indicated that also CaM-independent kinase activities might contribute. RLC p...Continue Reading

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Citations

May 31, 2016·Biochemical and Biophysical Research Communications·Hilde EikemoJan-Bjørn Osnes
Mar 1, 2017·Regenerative Medicine·Maureen Wanjare, Ngan F Huang
Nov 14, 2020·Expert Review of Clinical Immunology·Yiran YaoJun Shen
May 1, 2021·International Journal of Molecular Sciences·Kasturi MarkandranChristine Cheung

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