GRASP65, A PROTEIN INVOLVED IN THE STACKING OF GOLGI CISTERNAE

NEM prevents mitotic reassembly of Golgi cisternae into stacked struct ures. The major target of NEM is a 65 kDa protein conserved from yeast to mammals. Antibodies to this protein and a recombinant form of it b lock cisternal stacking in a cell-free system, justifying its designat ion as a Golgi ReAssembly Stacking Protein (GRASP65). One of the two m inor targets of NEM is GM130, previously implicated in the docking of transport vesicles and mitotic fragmentation of the Golgi stack. GRASP 65 is complexed with GM130 and is tightly bound to Golgi membranes, ev en under mitotic conditions when both are heavily phosphorylated. Thes e results link vesicle docking, stacking of Golgi cisternae, and the d isruption of both of these interactions during mitosis.