Varying effects of temperature, Ca2+ and cytochalasin on fusion activity mediated by human immunodeficiency virus type 1 and type 2 glycoproteins

We examined fusion mediated by the human immunodeficiency virus type 1 (HIV -1) and type 2 (HIV-2) envelope glycoproteins under various experimental co nditions. Incubation of HeLa cells expressing HIV-2(ROD) and HIV-2(SBL,ISY) envelope glycoproteins with HeLa-CD4 target cells resulted in fusion at te mperatures greater than or equal to 25 degrees C whereas fusion with cells expressing HIV-1(Lai) occurred only at greater than or equal to 31 degrees C. HIV-2 envelope glycoprotein-mediated fusion proceeded in the absence of Ca2+ in the culture medium, whereas HIV-1 fusion required Ca2+ ions for fus ion, In contrast to HIV-2 envelope glycoprotein fusion, incubations in the presence of the 0.5 mu M cytochalasin B completely inhibited HIV-1 envelope glycoprotein-mediated fusion. Our results suggest that in contrast to HIV- 2, HIV-1 fusion is dependent on dynamic processes in the target membrane. ( C) 2000 Federation of European Biochemical Societies.