EFFECTS OF CALCIUM-IONS ON PROTEOLYTIC PROCESSING OF HIV-1 GP160 PRECURSOR AND ON CELL-FUSION

Complete activation of human immunodeficiency virus type 1 (HIV-1) req uires the endoproteolytic cleavage by cellular protease of the envelop e glycoprotein precursor (gp160) into the external glycoprotein gp 120 , and the transmembrane glycoprotein gp41. We report here the effect o f depletion of cellular calcium ions on maturation of precursor gp 160 and its concomitant effect on syncytium formation. We show that the c ellular endoprotease activity responsible for gp160 maturation and the capacity for HIV-1 to induce syncytium formation are calcium-dependen t. In addition, we show that endoproteolytic maturation is a key step in syncytium formation induced by HIV-1.