Nonmuscle myosin II (NMII)

Nonmuscle myosin II is a hexameric motor protein complex that plays a central role in generating mechanical force within most eukaryotic cells. It consists of two heavy chains (~200 kDa each), two essential light chains (~17 kDa), and two regulatory light chains (~20 kDa). The complex assembles into bipolar filaments capable of interacting with actin filaments to produce contractile forces through ATP hydrolysis. Mammalian cells express three isoforms—NMIIA, NMIIB, and NMIIC—which have distinct but overlapping roles in processes such as cell adhesion, migration, cytokinesis, tissue formation, and maintenance of cellular tension. Nonmuscle myosin II is regulated at multiple levels including conformational changes that control filament assembly; phosphorylation events that modulate its activation state; and interactions with signaling pathways such as Rho/ROCK-mediated cascades. Its functions are critical for dynamic cellular behaviors like spreading, shape change during movement or division, stress fiber formation, focal adhesion maturation, and mechanotransduction—the ability of cells to sense physical properties of their environment via integrin-based adhesions connected to the actomyosin cytoskeleton. Dysregulation or altered expression of nonmuscle myosin II has been implicated in diseases including cancer progression/metastasis due to effects on cell motility/invasion, as well as cardiovascular disorders linked to abnormal tissue remodeling or contractility. While no approved therapeutic agents currently target nonmuscle myosin II directly for clinical use based on these references, it remains an important subject for drug discovery efforts focused on modulating cytoskeletal dynamics.

Other names

Non-muscle myosin IINM IIMyosin IIA (isoform)Myosin IIB (isoform)Myosin IIC (isoform)Non-muscle myosin 2NM2