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.