A role for the vesicle tethering protein, p115, in the post-mitotic stacking of reassembling Golgi cisternae in a cell-free system

During telophase, Golgi cisternae are regenerated and stacked from a hetero geneous population of tubulovesicular clusters. A cell-free system that rec onstructs these events has revealed that cisternal regrowth requires interp lay between soluble factors and soluble N-ethylmaleimide (NEM)-sensitive fu sion protein (NSF) attachment protein receptors (SNAREs) via two intersecti ng pathways controlled by the ATPases, p97 and NSF. Golgi reassembly stacki ng protein 65 (GRASP65), an NEM-sensitive membrane-bound component, is requ ired for the stacking process. NSF-mediated cisternal regrowth requires a v esicle tethering protein, p115, which we now show operates through its two Golgi receptors, GM130 and giantin. p97-mediated cisternal regrowth is p115 -independent, but we now demonstrate a role for p115, in conjunction with i ts receptors,in stacking p97 generated cisternae. Temporal analysis suggest s that p115 plays a transient role in stacking that may be upstream of GRAS P65-mediated stacking. These results implicate p115 and its receptors in th e initial alignment and docking of single cisternae that may be an importan t prerequisite for stack formation.