Addition of protein kinase C together with myosin light-chain kinase enhanced the Ca2+ sensitivity of rat skinned cardiac cells by up to 0.19 pCa unit.
Protein kinase C enhances the effects of myosin light-chain kinase on cardiac contractility through phosphorylation of LC2, troponin I, and troponin T.
Many neurohormones alter the force of cardiac contraction by variations in the intracellular Ca2+ concentration. alpha 1-Adrenergic and muscarinic stimulations, rather, modify the sensitivity of contractile proteins to Ca(2+)-calmodulin-myosin light-chain kinase (MLCK) complex induces a large increase in Ca2+ sensitivity (0.14 pCa unit) of these easily accessible myofilaments. This increase is further enhanced by up to 0.19 pCa unit when protein kinase C (PKC) is added together with MLCK. Similarly, the Ca2+ ATPase activity of skinned cells in suspension is increased in the presence of MLCK and further in the presence of both kinases. 32P-labelling and SDS/PAGE show that these changes are associated with light-chain 2 (LC2) phosphorylation together with phosphorylation of troponin I and troponin T when PKC is added. Although to a smaller extent than in smooth muscle, phosphorylation of cardiac myosin LC2 may be involved in the modulation of heart contractility.
Clémеnt et al. (1992) studied Cardiac contractility (rat model). Protein kinase C (PKC) and myosin light-chain kinase (MLCK) vs. MLCK alone was evaluated on Ca2+ sensitivity and Ca2+ ATPase activity. Addition of protein kinase C together with myosin light-chain kinase enhanced the Ca2+ sensitivity of rat skinned cardiac cells by up to 0.19 pCa unit.