MYLK/smMLCK

MYLK encodes smooth muscle myosin light chain kinase and, through alternative promoters, non-muscle isoforms from the same gene. The smooth muscle enzyme phosphorylates regulatory myosin light chain on serine 19 in a calcium-calmodulin-dependent manner, increasing actomyosin ATPase activity to drive arterial contraction, bronchoconstriction, and intestinal peristalsis. Long non-muscle isoforms contain additional domains for actin binding and focal adhesion targeting, regulating endothelial contractility, barrier permeability, leukocyte extravasation, and cell migration. Consequently MYLK dysfunction contributes to hypertension, asthma, vascular leak syndromes, and inflammatory bowel disease, and inhibitors of smooth muscle MLCK remain a long-standing pharmacological strategy for smooth muscle hypercontractility.