Myosin heavy chain 9 (MYH9)

Myosin heavy chain 9 (MYH9), also known as non-muscle myosin heavy chain IIA (NMHC IIA), is a critical motor protein that forms the heavy chain component of the non-muscle myosin IIA (NM IIA) complex. As an ATP-dependent enzyme, it interacts with actin filaments to generate mechanical force and tension, which are essential for fundamental cellular processes including cytokinesis, cell migration, adhesion, and the maintenance of cell shape and polarity. MYH9 is ubiquitously expressed but plays a particularly vital role in the hematopoietic system, where it is the predominant myosin isoform in platelets and their precursor megakaryocytes, facilitating proper platelet formation and retraction. In clinical medicine, MYH9 is recognized both as a driver of disease and a potential therapeutic target. Mutations in the MYH9 gene cause a spectrum of autosomal dominant disorders, collectively termed MYH9-related disease (MYH9-RD), which manifest as macrothrombocytopenia, sensorineural hearing loss, and progressive glomerulonephritis. In oncology, MYH9 is frequently overexpressed and associated with increased tumor cell motility, epithelial-mesenchymal transition (EMT), and metastasis, making it a target for anti-cancer strategies. While small-molecule inhibitors like blebbistatin are widely used in research to study MYH9 function, newer compounds and repurposed drugs like bezafibrate are being investigated for their ability to modulate MYH9 activity in cancer and thrombosis.

Other names

Non-muscle myosin heavy chain IIANMMHC-IIAMyosin-9MHANMHC-II-ANMMHCABDPLT6DFNA17EPSTSFTNS

Inhibition of ATPase activity, stabilization of the super-relaxed state, inhibition of filament assembly, and blocking of phosphorylation.