Occurrence of an HIV-1 gp160 endoproteolytic activity in low-density vesicles and evidence for a distinct density distribution from endogenously expressed furin and PC7/LPC convertases

Human immunodeficiency virus (HIV) glycopprotein (gp) 160 processing by hos t cell proteinases is an essential step for viral fusion and infectivity, W e have identified a rat liver subcellular fraction which specifically proce sses gp160 into gp120 and gp41, Using equilibration of microsomes in sucros e gradients, the gp160 cleavage activity was associated with particles equi librating at low densities, well-separated from the endoplasmic reticulum, cis-Golgi network, Golgi stacks, lysosomes and plasma membrane, Its density distribution was compatible with light secretory vesicles derived from the trans-Golgi network (TGN) or to endosomes, but association with endosomes was not supported by free flow electrophoresis, Although furin and pro-prot ein convertase (PC) 7/LPC have been proposed as the major gp160 processing convertases, the rat liver microsomal gp160 processing activity was essenti ally resolved from furin and only partially overlapped PC7/LPC, These data suggest that proteinase(s) other than furin and PC7/ LPC, presumably locate d in TGN-derived vesicles, mag participate in the gp160 processing into gp1 20 and gp41, (C) 1999 Federation of European Biochemical Societies.