26.19: Role of Septins
Septins are the recently discovered fourth major protein component of the cytoskeleton, along with microfilaments, microtubules, and intermediate filaments. These proteins can associate with other cytoskeletal filaments and carry out varied roles or can be free-floating in the cytoplasm.
Cellular Functions of Septins
Recent studies have revealed the multifaceted roles of septins in various cellular processes such as cytokinesis, ciliogenesis, and neurogenesis. Septins act as scaffolds and promote protein-protein interactions; for example, in S. cerevisiae, septin scaffolding protein helps recruit different filament proteins to form contractile rings during cytokinesis.
Septin was first found in the sperm flagella's annulus, which compartmentalizes the anterior and posterior tail regions. Mutation in the septin-forming genes like SEPT12 affects sperm motility and its structural integrity. Other septins like SEPT2 are involved in forming a diffusion barrier between the cilia and the cytoplasm.
Septins also play a role in stabilizing the membrane by binding and modifying the membrane and action-myosin interactions.
Diseases Related to Septins
Studies have shown septins are associated with proteins involved in neurodegenerative diseases like Parkinson's and Alzheimer's. In Parkinson's disease, septin interacts with parkin, an E3 ubiquitin ligase. Septins' mutation has also been linked with tumorigenesis or cancer. Studies on cancerous cells suggest septin mutations are also related to resistance to cells, metastasis, proliferation, and angiogenesis.
