Myosin-IXb (MYO9B)

Myosin-IXb (MYO9B) is an unconventional, single-headed processive myosin that combines actin-based motor activity with a C-terminal Rho GTPase-activating protein (RhoGAP) domain[1][2][3]. MYO9B is expressed in various cell types, including immune cells, where it is essential for the spatial and temporal regulation of the actin cytoskeleton. It serves as a “motorized Rho inhibitor,” using its mobility along actin filaments to position its RhoGAP activity at sites of active actin polymerization, such as lamellipodia and ruffles. By inactivating Rho GTPases locally, MYO9B precisely modulates cell polarity, migration, and shape—functions critical for effective immune responses, wound healing, and cellular organization[1][3]. Mutations or variants in the MYO9B gene (notably CELIAC4) have been linked to increased susceptibility to celiac disease and may also contribute to other inflammatory and autoimmune conditions due to dysregulated cytoskeletal and immune function[4]. No drugs directly target MYO9B as of current knowledge, but its pathway is a potential therapeutic target for immune and barrier-related disorders.

Other names

Unconventional myosin-IXbMYO9BMYR5Unconventional myosin-9bCELIAC4myosin-IXbunconventional myosin-9b

Negative regulation of RhoA and related Rho-family GTPases through its RhoGAP activity, thereby modulating actin-based cell motility and morphology