Cell Division | Septins and Cytokinesis

TL;DR: Septins, conserved GTPases, form large complexes that regulate cellular processes, including cytokinesis, vesicle trafficking, and axon migration, and are implicated in cancer through their role in cell division and protein localization.

Abstract: Septins comprise a family of conserved GTPases that has been identified in most animals from yeast to mammals. Each organism has multiple septin family genes. Biochemical, genetic, and light- and electron microscopy have revealed that multiple septin polypeptides form large, discrete complexes that further multimerize into filaments and higher order assemblies. Septins have been implicated in a variety of cellular processes including cytokinesis, vesicle trafficking, and axon migration. In yeast, they are involved in bud site selection, cell polarity and cytokinesis. Their name derives from their requirement during the final separation of the daughter cells in yeast, a process termed septation. While the precise molecular functions of septins are not known, a unifying hypothesis considers septin assemblies as scaffolds that localize, and perhaps regulate, diverse proteins involved in cortical dynamics. The septin scaffold may also limit diffusion of proteins in the plane of the plasma membrane. This barrier role is proposed to be important in at least two contexts: cytokinesis and in dendritic spines. Through these, or possible yet-unknown, cellular functions, septins are implicated in cancer; misexpression of septin genes has been observed in diverse tumor types. Thus, characterization of the function of these unique oligomeric proteins aids our understanding of many important normal, as well as pathogenic, cellular processes.