Inhibition of the membrane fusion machinery prevents exit from the TGN and proteolytic processing by furin.

The Semliki Forest virus (SFV) glycoprotein precursor p62 is processed to the E2 and E3 during the transport from the trans-Golgi network (TGN) to the cell surface. We have studied the regulation of the membrane fusion machinery (Rab/N-ethylmaleimide (NEM)-sensitive fusion protein (NSF)/soluble NSF attachment protein (SNAP)-SNAP receptor) in this processing. Activation of the disassembly of this complex with recombinant NSF stimulated the cleavage of p62 in permeabilized cells. Inactivation of NSF with a mutant alpha-SNAP(L294A) or NEM treatment inhibited processing of p62. Rab GDP dissociation inhibitor inhibited the cleavage. Inactivation of NSF blocks the transport of SFV glycoproteins and vesicular stomatitis virus G-glycoprotein from the TGN membranes to the cell surface. The results support the conclusion that inhibition of membrane fusion arrests p62 in the TGN and prevents its processing by furin.