septins

Septins are a family of GTP-binding proteins that assemble into heteromeric complexes and higher-order filaments, providing a cytoskeletal scaffold at the cell cortex in many eukaryotic cells. They were first described in yeast and have since been found in animals and some protists.

Each septin protein contains a conserved central GTPase domain, flanked by variable N- and C-terminal regions, including coiled-coil domains important for interactions. In cells they form defined subcomplexes, such as hexamers or octamers, that polymerize into filaments and ring-like structures at membranes. GTP binding and hydrolysis regulate assembly dynamics and filament stability.

Septins organize cell division and polarity by forming a scaffold at the cytokinetic ring during cytokinesis, coordinating membrane remodeling and cytoskeletal organization, and directing vesicle trafficking. They also localize to the base of cilia, cell–cell junctions, and other sites of membrane curvature, where they interact with actin filaments and microtubules to organize organelles and signaling pathways.

In humans, fourteen SEPT genes (SEPT1–SEPT14) encode multiple isoforms with tissue-specific expression. Septins are evolutionarily conserved in fungi and animals but are not found in higher plants. Their assembly into higher-order structures is influenced by subunit composition and post-translational modifications.

Dysregulation of septins has been linked to diseases including cancer and neurodevelopmental disorders. Septins are studied as markers and potential therapeutic targets, with ongoing research aimed at elucidating their diverse roles in cell biology and disease processes.