p97 and p47 function in membrane tethering in cooperation with FTCD during mitotic Golgi reassembly

p97ATPase‐mediated membrane fusion is required for the biogenesis of the Golgi complex. p97 and its cofactor p47 function in soluble N‐ethylmaleimide‐sensitive factor (NSF) attachment protein receptor (SNARE) priming, but the tethering complex for p97/p47‐mediated membrane fusion remains unknown. In this study, we identified formiminotransferase cyclodeaminase (FTCD) as a novel p47‐binding protein. FTCD mainly localizes to the Golgi complex and binds to either p47 or p97 via its association with their polyglutamate motifs. FTCD functions in p97/p47‐mediated Golgi reassembly at mitosis in vivo and in vitro via its binding to p47 and to p97. We also showed that FTCD, p47, and p97 form a big FTCD‐p97/p47‐FTCD tethering complex. In vivo tethering assay revealed that FTCD that was designed to localize to mitochondria caused mitochondria aggregation at mitosis by forming a complex with endogenous p97 and p47, which support a role for FTCD in tethering biological membranes in cooperation with the p97/p47 complex. Therefore, FTCD is thought to act as a tethering factor by forming the FTCD‐p97/p47‐FTCD complex in p97/p47‐mediated Golgi membrane fusion.