FMN1

FMN1, also known as Formin-1, is a protein encoded by the FMN1 gene in humans. It is a member of the formin family, specifically the diaphanous-related formin (DRF) subfamily, which acts as an actin nucleator and elongator to regulate the assembly of linear actin filaments. Formin proteins commonly function downstream of Rho family GTPases to coordinate cytoskeletal remodeling.

FMN1 proteins feature an N-terminal regulatory region that includes a GTPase-binding domain, and a C-terminal region containing the FH1 and FH2 actin-nucleation domains. They also contain diaphanous inhibitory (DID) and diaphanous autoregulatory (DAD) domains that mediate autoinhibition; activation occurs when Rho family GTPases bind, relieving autoinhibition and enabling filament nucleation and processive barbed-end elongation. The FH1 domain recruits profilin–actin complexes, promoting rapid actin polymerization.

In terms of expression and function, FMN1 is expressed in various tissues, with notable roles in the nervous system and developing tissues. It participates in cytoskeletal organization, cell polarity, and cell migration. In neurons, FMN1 has been associated with neurite outgrowth, axon guidance, and dendritic spine formation, contributing to neuronal development and morphogenesis. In other cell types, FMN1 influences actin dynamics at leading-edge structures such as filopodia and lamellipodia.

Interactions of FMN1 include engagement with Rho family GTPases and actin-related proteins, as well as profilin, which together regulate filament nucleation and elongation. Research continues to elucidate the full spectrum of FMN1’s roles in development, neurobiology, and disease.