Lipid domains and membrane (re)shaping : from biophysics to biology

The surface of living cells provides an interface that not only separates the outer and inner environments but also contributes to several functions, including regulation of solute influx and efflux, signal transduction, lipid metabolism and trafficking. To fulfill these roles, the cell surface must be tough and plastic at the same time. This could explain why cell membranes exhibit a so large number of different lipid species and why some lipids form membrane domains. Besides the transient nanometric lipid rafts, morphogical evidence for stable submicrometric domains, well-accepted for artificial and highly specialized biological membranes, has been recently reported for a variety of living cells. Such complexity in lipid distribution could play a role in cell physiology, including in cell shaping and reshaping upon deformation and vesiculation. However, this remains to be clearly demonstrated. In this chapter, we highlight the main actors involved in cell (re)shaping, including the cytoskeleton, membrane-bending proteins and membrane biophysical properties. Based on integration of theoretical work and data obtained on model membranes, highly specialized cells and living cells (from prokaryotes to yeast and mammalian cells), we then discuss recent evidences supporting the existence of submicrometric lipid domains and documented mechanisms involved in their control. We also provide key recent advances supporting the role of lipid domains in cell (re)shaping. We believe that the surface of living cells is made of a variety of lipid domains that are differentially controlled and remodelled upon cell reshaping