Septins are
GTP-binding proteins that form filaments and higher-order structures on the cell cortex of eukaryotic cells and associate with actin and microtubule cytoskeletal networks. When assembled,
septins coordinate cell division and contribute to cell polarity maintenance and membrane remodeling. These functions manifest themselves via scaffolding of cytosolic
proteins and cytoskeletal networks to specific locations on membranes and by forming diffusional barriers that restrict lateral diffusion of
proteins embedded in membranes. Notably, many
neurodegenerative diseases and
cancers have been characterized as having misregulated
septins, suggesting that their functions are relevant to diverse diseases. Despite the importance of
septins, little is known about what features of the plasma membrane influence
septin recruitment and alternatively, how
septins influence plasma membrane properties.
Septins have been localized to the cell cortex at the base of cilia, the mother-bud neck of yeast, and branch points of filamentous fungi and dendritic spines, in cleavage furrows, and in retracting membrane protrusions in mammalian cells. These sites all possess some degree of curvature and are likely composed of distinct
lipid pools. Depending on the context,
septins may act alone or in concert with other cytoskeletal elements to influence and sense membrane properties. The degree to which
septins react to and/or induce changes in shape and
lipid composition are discussed here. As
septins are an essential player in basic biology and disease, understanding the interplay between
septins and the plasma membrane is critical and may yield new and unexpected functions.