Septins: the fourth component of the cytoskeleton

Septins belong to a family of GTP-binding proteins that is highly conserved in eukaryotes and is recognized as a novel component of the cytoskeleton. They assemble to form hetero-oligomeric complexes, filaments, bundles and rings.How septins assemble for function, and how they interact and work in conjunction with actin, microtubules and phospholipids, is the focus of intense investigation.Septins have recently been reported to act as scaffolds for protein recruitment at the plasma membrane and in the cytosol, and as diffusion barriers for subcellular compartmentalization at the bases of cilia, at the annuli of spermatozoa and at the bases of dendritic spines in neurons.Studies of host–microorganism interactions have highlighted roles for septins in bacterial invasion and autophagy.Septin biology will help to decipher the molecular mechanisms underlying human diseases in which septins have been implicated, such as cancer, neurological disorders and infections.