ISOLATION OF FUNCTIONAL GOLGI-DERIVED VESICLES WITH A POSSIBLE ROLE IN RETROGRADE TRANSPORT

Secretory proteins enter the Golgi apparatus when transport vesicles f use with the cis-side and exit in transport vesicles budding from the trans-side. Resident Golgi enzymes that have been transported in the c is-to-trans direction with the secretory flow must be recycled constan tly by retrograde transport in the opposite direction. In this study, we describe the functional characterization of Golgi-derived transport vesicles that were isolated from tissue culture cells. We found that under the steady-state conditions of a living cell, a fraction of resi dent Golgi enzymes was found in vesicles that could be separated from cisternal membranes. These vesicles appeared to be depleted of secreto ry cargo. They were capable of binding to and fusion with isolated Gol gi membranes, and after fusion their enzymatic contents most efficient ly processed cargo that had just entered the Golgi apparatus. Those re sults indicate a possible role for these structures in recycling of Go lgi enzymes in the Golgi stack.