Membrane domains and polarized trafficking of sphingolipids

The plasma membrane of polarized cells consists of distinct domains, the ap ical and basolateral membrane that are characterized by a distinct lipid an d protein content. Apical protein transport is largely mediated by (glyco)s phingolipid-cholesterol enriched membrane microdomains, so called rafts. In addition changes in the direction of polarized sphingolipid transport appe ar instrumental in cell polarity development. Knowledge is therefore requir ed of the mechanisms that mediate sphingolipid sorting and the complexity o f the trafficking pathways that are involved in polarized transport of both sphingolipids and Proteins. Here rue summarize specific biophysical proper ties that underly mechanisms relevant to sphingolipid sorting, cargo recrui tment and polarized trafficking, and discuss the central role of a subapica l compartment, SAC or common endosome (CE), as a major intracellular site i nvolved In polarized sorting of sphingolipids, and in development and maint enance of membrane polarity.