Evidence for Segregation of Sphingomyelin and Cholesterol during Formation of Copi-Coated Vesicles

摘要: In higher eukaryotes, phospholipid and cholesterol synthesis occurs mainly in the endoplasmic reticulum, whereas sphingomyelin glycosphingolipids are synthesized Golgi apparatus. Lipids like gradually enriched along secretory pathway, with their highest concentration at plasma membrane. How a cell succeeds maintaining organelle-specific lipid compositions, despite steady flow of incoming outgoing transport carriers is not yet clear. Transport sorting pathway both proteins most lipids thought to be mediated by vesicular transport, coat protein I (COPI) vesicles operating early pathway. Although constituents these intermediates characterized great detail, much less known about content. Using nano-electrospray ionization tandem mass spectrometry for quantitative analysis COPI-coated parental membranes, we find only low amounts compared donor providing evidence significant segregation from COPI lipids. addition, our data indicate individual molecular species. The possible mechanisms underlying this segregation, as well implications on function, discussed.