Post-Golgi vesicles target and deliver most biosynthetic cargoes to the cell surface. However, the molecules and mechanisms involved in fusion of these vesicles are not well understood. We have employed a system to simultaneously monitor release of luminal and membrane biosynthetic cargoes from individual post-Golgi vesicles.
Exocytosis of these vesicles is not
calcium triggered. Release of luminal cargo can be accompanied by complete, partial, or no release of membrane cargo. Partial and no release of membrane cargo of a fusing vesicle are fates associated with kiss-and-run
exocytosis, and we find that these are the predominant mode of post-Golgi vesicle
exocytosis. Partial cargo release by post-Golgi vesicles occurs because of premature closure of the
fusion pore and is modulated by the activity of
clathrin,
actin, and
dynamin. Our results demonstrate that these components of the endocytic machinery modulate the nature and extent of biosynthetic cargo delivery by post-Golgi vesicles at the
cell membrane.
