Smooth muscle myosin (Myosin-11) (MYH11)

The Ca2+-dependent myofibrillar ATPase in vascular smooth muscle refers to the enzymatic activity of the smooth muscle myosin complex (primarily Myosin-11), which serves as the molecular motor for vascular contraction (NIH, 2023). Unlike striated muscle, where calcium regulation is mediated by the troponin complex, smooth muscle contraction is primarily controlled by the calcium-calmodulin-dependent activation of Myosin Light Chain Kinase (MLCK) (ResearchGate, 2022). MLCK phosphorylates the 20 kDa regulatory light chain (MLC20), which triggers the myofibrillar ATPase activity and initiates cross-bridge cycling (ResearchGate, 2022). This ATPase activity is essential for maintaining vascular tone and regulating blood pressure, and its dysregulation is a key factor in the pathogenesis of hypertension, vasospasm, and atherosclerosis (Annual Reviews, 1987). Mutations in the MYH11 gene, which encodes the smooth muscle myosin heavy chain, are specifically associated with hereditary thoracic aortic aneurysms and dissections (UniProt, 2024). Pharmacological modulation of this system includes the use of calmodulin antagonists and MLCK inhibitors, which directly reduce the calcium-dependent activation of the myofibrillar ATPase (PubMed, 1980). Additionally, certain clinical agents like bepridil and perhexiline have been shown to inhibit this contractile engine, offering a direct pathway for vasodilation in cardiovascular therapy (PubMed, 1984). Research into direct myosin inhibitors, such as blebbistatin, continues to provide insights into the potential for more specific therapeutic modulation of vascular contractility (MDPI, 2022).

Other names

Smooth muscle myosin heavy chainSMMHCActomyosin ATPaseMyofibrillar ATPaseVascular smooth muscle myosinCa2+-dependent myofibrillar ATPase

Inhibition of the myosin ATPase catalytic activity or the calcium-calmodulin-dependent phosphorylation of the myosin light chain required for its activation.