Formin

Formins are a family of conserved actin-nucleating proteins that regulate the assembly and organization of the cytoskeleton. They promote the formation of linear actin filaments and participate in various cellular processes, including cell shape changes, migration, and cytokinesis. In many organisms, formins are essential for development and tissue morphogenesis.

Most formins contain a conserved actin- nucleating region known as the FH2 domain, often accompanied by a proline-rich FH1 region that binds profilin–actin complexes to accelerate filament elongation. Regulation typically involves an N-terminal diaphanous inhibitory domain (DID) that interacts with a C-terminal diaphanous activating domain (DAD) to keep the protein autoinhibited until signaling relieves the interaction. Rho family GTPases and other signaling inputs can activate formins by disrupting the autoinhibitory interaction. Formins can also associate with microtubules and influence their dynamics, linking actin and microtubule networks.

Biological roles of formins are diverse and include control of cell polarity, directed cell migration, cytokinesis, and neurite outgrowth. Different isoforms are expressed in distinct tissues and developmental stages, and many formins shuttle between cytoplasmic and membrane-associated locations to coordinate cytoskeletal remodeling.

In humans, misregulation or mutation of certain formin genes has been linked to developmental disorders, hearing loss, and cancer in some studies. Researchers commonly use experimental inhibitors, such as SMIFH2, to study formin function and actin dynamics. Formins remain an active area of investigation for understanding how cells shape and move.