Abstract

Septins are conserved cytoskeletal proteins essential for processes such as cell division, spermatogenesis, neuronal morphogenesis, ciliogenesis, infection, and cell migration. Their dysfunction is linked to neurodegeneration, infertility, and cancer. Septins polymerize into filaments and higher-order structures like rings and arcs, which are crucial for their function. A classic example is the septin collar in budding yeast—an hourglass-shaped structure at the bud neck that persists through most of the cell cycle and is essential for cytokinesis. It recruits numerous cytokinetic proteins, including components of the contractile actomyosin ring. Just before cytokinesis, the yeast septin collar undergoes a major remodelling into a double ring that sandwiches the actomyosin ring. We recently showed that this remodelling is required for actomyosin ring constriction and successful cytokinesis. In this seminar, I will discuss our work uncovering the molecular basis of septin ring reorganisation in budding yeast. Interestingly, similar septin remodelling has been observed in other fungi and in mammalian cells, suggesting an evolutionarily conserved process.