Myosin light chain kinase (smooth muscle isoform) (smMLCK)

Myosin light chain kinase (smooth muscle isoform), commonly referred to as smMLCK, is a specialized calcium/calmodulin-dependent serine/threonine kinase essential for the regulation of smooth muscle contractility [1, 2]. Upon an increase in intracellular calcium, the calcium-calmodulin complex binds to smMLCK, activating its catalytic domain to phosphorylate the 20-kDa regulatory light chain of myosin II (MLC20) [1, 5]. This phosphorylation event triggers the actin-activated ATPase activity of myosin, enabling cross-bridge cycling and muscle contraction [2, 5]. Beyond its primary role in contraction, smMLCK is a critical regulator of vascular endothelial permeability and is involved in various cellular processes such as migration and apoptosis [2, 3]. Dysregulation of smMLCK activity is strongly associated with the pathogenesis of asthma, where it drives airway hyperresponsiveness, and cardiovascular conditions like hypertension and aortic dissection [3, 5]. It also plays a role in inflammatory diseases by modulating the intestinal and lung epithelial barriers [2]. While several small-molecule inhibitors like ML-7 and ML-9 have been developed as research tools, achieving high selectivity for the smooth muscle isoform over the non-muscle isoform remains a challenge for clinical application [4]. Therapeutic strategies targeting smMLCK aim to alleviate excessive muscle constriction and restore barrier function in diverse disease states [2, 3].

Other names

MLCKMYLKMYLK1Smooth muscle MLCKMLCK108MLCK210Kinase-related protein

Inhibition of the catalytic activity of myosin light chain kinase, preventing the phosphorylation of the 20-kDa regulatory light chain of myosin (MLC20) [1, 2]. This prevents the activation of myosin ATPase and the subsequent interaction with actin, leading to smooth muscle relaxation and reduced cellular contractility [2, 5].