HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 INTERACTION WITH THE MEMBRANE OF CD4(+) CELLS INDUCES THE SYNTHESIS AND NUCLEAR TRANSLOCATION OF 70K HEAT-SHOCK PROTEIN

In the last few years a growing body of experimental evidence has indicated that the interaction of human immunodeficiency virus type 1 (HIV-1) surface glycoprotein (gp120) with the membrane of CD4(+) cells may deliver negative signals, eventually leading to programmed cell death (apoptosis) of either mature CD4(+) lymphocytes or CD34(+) haematopoietic progenitor cells, in the absence of cell infection with HIV-1. However, information on the possible activation of the classical signal transduction pathway through gp120 engagement of cell surface CD4 is contradictory. Heat shock proteins (hsp) or 'stress' proteins' are involved in protecting cells from the deleterious effects of heat and other stresses and perform various cell roles. In mammalian cells there is evidence that hsp70 is involved in the transport of proteins to lysosomes, mitochondria and the nucleus. The results obtained in our study demonstrate that early (3 h) after the exposure of permissive CD4(+) cells to HIV-1 (or to purified recombinant gp120) a peak of increased synthesis and nuclear translocation of a 70K hsp (and possibly other proteins) is observed. These data indicate that gp120 possesses the capacity to trigger a cascade of events through a transmembrane signalling activity.