Regulation of myosin light-chain phosphorylation and its roles in cardiovascular physiology and pathophysiology

The regulation of muscle contraction is a critical function in the cardiovascular system, and abnormalities may be life-threatening or cause illness. The common basic mechanism in muscle contraction is the interaction between the protein filaments myosin and actin. Although this interaction is primarily regulated by intracellular Ca2+, the primary targets and intracellular signaling pathways differ in vascular smooth muscle and cardiac muscle. Phosphorylation of the myosin regulatory light chain (RLC) is a primary molecular switch for smooth muscle contraction. The equilibrium between phosphorylated and unphosphorylated RLC is dynamically achieved through two enzymes, myosin light chain kinase, a Ca2+-dependent enzyme, and myosin phosphatase, which modifies the Ca2+ sensitivity of contractions. In cardiac muscle, the primary target protein for Ca2+ is troponin C on thin filaments; however, RLC phosphorylation also plays a modulatory role in contraction. This review summarizes recent advances in our understanding of the regulation, physiological function, and pathophysiological involvement of RLC phosphorylation in smooth and cardiac muscles.

Automated summary

Regulation of muscle contraction is essential in the cardiovascular system, with the interaction between myosin and actin filaments being a common mechanism. The phosphorylation of myosin regulatory light chain plays a crucial role in smooth muscle contraction, while in cardiac muscle, troponin C is the primary target protein for Ca2+ with RLC phosphorylation also modulating contraction. Recent advances have improved our understanding of the regulatory role of RLC phosphorylation in smooth and cardiac muscles.