Myosin light chain phosphorylation pathway (MLC phosphorylation pathway)

The Myosin Light Chain (MLC) phosphorylation pathway is a fundamental signaling cascade that regulates actomyosin contractility in smooth muscle and non-muscle cells (StatPearls, 2023). The primary event in this pathway is the phosphorylation of the 20-kDa regulatory light chain (RLC) of myosin II, catalyzed by Myosin Light Chain Kinase (MLCK) in a calcium/calmodulin-dependent manner (PubMed, 2017). This phosphorylation promotes the interaction of myosin heads with actin filaments, leading to muscle contraction or cellular tension (NIH, 2024). Conversely, Myosin Light Chain Phosphatase (MLCP) dephosphorylates the RLC to induce relaxation. The pathway is further modulated by Rho-associated protein kinase (ROCK), which inhibits MLCP, thereby sensitizing the contractile apparatus to calcium (Wikipedia, 2024). Dysregulation of MLC phosphorylation is a key factor in the pathogenesis of various conditions, including hypertension, asthma, and glaucoma (Frontiers, 2017). Therapeutic targeting of this pathway, particularly through ROCK inhibitors like fasudil and netarsudil, has proven effective in treating cardiovascular and ocular diseases by promoting vasodilation and reducing intraocular pressure (PubMed, 2024). Additionally, the pathway's role in endothelial barrier function and cell migration makes it a target for research in inflammatory diseases and cancer metastasis (PubMed, 2017).

Other names

MLC phosphorylation signalingMyosin regulatory light chain phosphorylation pathwayMLCK/MLCP pathwayActomyosin contractility pathway

The pathway is targeted by inhibiting Myosin Light Chain Kinase (MLCK) or Rho-associated protein kinase (ROCK) to prevent the phosphorylation of the myosin regulatory light chain (RLC), or by activating Myosin Light Chain Phosphatase (MLCP) via the nitric oxide/cGMP/PKG signaling axis to promote RLC dephosphorylation (PubMed, 2017; StatPearls, 2023). These actions lead to the inhibition of actomyosin cross-bridge cycling, resulting in smooth muscle relaxation and reduced cellular contractility (NIH, 2024).