Glycosphingolipids promote entry of a broad range of human immunodeficiency virus type 1 isolates into cell lines expressing CD4, CXCR4, and/or CCR5

Treatment of human osteosarcoma cells, expressing CD4 and various chemokine receptors, with the glucosylceramide synthase inhibitor 1-phenyl-2-hexadec anoylamino-3-morpholino-1-propanol (PPMP), blocked target membrane glycosph ingolipid (GSL) biosynthesis and reduced the susceptibility of cells to inf ection and fusion mediated by envelope glycoproteins from a variety of huma n immunodeficiency virus type 1 (HIV-1) isolates that utilize CXCR4 and/or CCR5. PPMP treatment of the cell lines did not significantly change the cel l surface expression of CD4, CXCR4, and/or CCR5, nor did it alter the chemo kine receptor association with CD4. PPMP-treated cells exhibited no changes in chemokine-induced Ca2+ mobilization and chemotaxis. However, massive en velope glycoprotein conformational changes triggered by CD4 and the appropr iate chemokine receptor on the target membrane were inhibited when the targ et cells were treated,vith PPMP. Addition of various purified GSLs to PPMP- treated target cells showed that for all isolates tested, globotriaosylcera mide (Gb3) was the most potent GSL in restoring the fusion susceptibility o f target cells with cells expressing HIV-1 envelope glycoproteins; addition of the monosialoganglioside GM3 yielded a slight enhancement of fusion sus ceptibility. Our data are consistent with the notion that a limited number of specific GSL species serve as crucial elements in organizing gp120-gp41, CD4, and an appropriate chemokine receptor into a membrane fusion complex.