EXPRESSION AND CHARACTERIZATION OF GLYCOPHOSPHOLIPID-ANCHORED HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 ENVELOPE GLYCOPROTEINS

Four chimeric human immunodeficiency virus type 1 (HIV-1) env genes we re constructed which encoded the extracellular domain of either the wi ld-type or a cleavage-defective HIV-1 envelope glycoprotein (gp160) fu sed at one of two different positions in env to a C-terminal glycosyl- phosphatidylinositol (GPI) attachment signal from the mouse Thy-1.1 gl ycoprotein. All four of the constructs encoded glycoproteins that were efficiently expressed when Rev was supplied in trans, and the two cle avable forms were processed normally to gp120 and a chimeric ''gp41.'' The chimeric glycoproteins, in contrast to the wild-type glycoprotein , could be cleaved from the surface of transfected cells by treatment with phosphatidylinositol-specific phospholipase C, indicating that th ey were anchored in the plasma membrane by a GPI moiety. These GPI-anc hored glycoproteins were transported intracellularly at a rate only sl ightly lower than that of the full-length HIV-1 glycoprotein and were present on the cell surface in equivalent amounts. Nevertheless, all f our glycoproteins were defective in mediating both cell-cell and virus -cell fusion as determined by syncytium formation in COS-1-HeLa-T4 cel l mixtures and trans complementation of an env-defective HIV-1 genome.