BIOGENESIS OF COPI-COATED TRANSPORT VESICLES

Biosynthetic protein transport and sorting along the secretory pathway represents the last step in biosynthesis of a variety of proteins, Pr oteins destined for delivery to the cell surface are inserted cotransl ationally into the endoplasmic reticulum (ER) and, after their correct folding, are transported out of the ER towards their final destinatio ns. The successive compartments of the secretory pathway are connected by vesicular shuttles that mediate delivery of cargo, The formation o f these carrier vesicles depends on the recruitment of cytosolic coat proteins that are thought to act as a mechanical device to shape a fla ttened donor membrane into a spherical vesicle, A general molecular ma chinery that mediates targeting and fusion of carrier vesicles has als o been identified. This review is focused on COPI-coated vesicles that operate in protein transport within the early secretory pathway, Rath er than representing a general overview of the role of COPI-coated ves icles, this mini-review will discuss mechanisms specifically related t o the biogenesis of COPI-coated vesicles: (i) a possible role of phosp holipase D in the formation of COPI-coated vesicles, (ii) a functional role of a novel family of transmembrane proteins, the p24 family, in the initiation of COPI assembly, and (iii) the direction COPI-coated v esicles mag take within the early secretory pathway. (C) 1997 Federati on of European Biochemical Societies.