ENDOPROTEOLYTIC CLEAVAGE OF HIV-1 GP160 ENVELOPE PRECURSOR OCCURS AFTER EXIT FROM THE TRANS-GOLGI NETWORK (TGN)

Endoproteolytic processing of human immunodeficiency virus type 1 (HIV -1) gp160 membrane glycoprotein precursor into gp 120 and gp41 is nece ssary for formation of infectious HIV particles [1]. We have studied t he intracellular site of this processing using inhibition of transport at reduced temperature (20 degrees C). That reduced temperature (20 d egrees C) inhibits the intracellular transport also in Jurkat-tat cell s was demonstrated using the Semliki Forest virus p62 precursor proces sing as model. In HIV-1 infected Jurkat-tat cells the proteolytic proc essing of gp160 precursor did not occur when the protein was accumulat ed in the TGN at 20 degrees C temperature. When the temperature was sh ifted to 37 degrees C the HIV-1 gp160, which had accumulated in the TG N at the reduced temperature, was proteolytically processed. The proce ssing of gp 160 was inhibited when the temperature reversion was carri ed out in the presence of brefeldin A (BFA) or aluminium fluoride (ALF (n)) indicating that the exit from the TGN is required for the proteol ytic cleavage of HIV-1 gp 160 precursor. The results suggest that the processing of gp 160 takes place at a yet unidentified transport step which is distal to the TGN/20 degrees C block site.