Cholesterol binds to synaptophysin and is required for biogenesis of synaptic vesicles

Here, to study lipid-protein interactions that contribute to the biogenesis of regulated secretory vesicles, we have developed new approaches by which to label proteins in vivo, using photoactivatable cholesterol and glycerop hospholipids. We identify synaptophysin as a major specifically cholesterol -binding protein in PC12 cells and brain synaptic vesicles. Limited cholest erol depletion, which has little effect on total endocytic activity, blocks the biogenesis of synaptic-like microvesicles (SLMVs) from the plasma memb rane. We propose that specific interactions between cholesterol and SLMV me mbrane proteins, such as synaptophysin, contribute to both the segregation of SLMV membrane constituents from plasma-membrane constituents, and the in duction of synaptic-vesicle curvature.