Functional expression of CD4, CXCR4, and CCR5 in glycosphingolipid-deficient mouse melanoma GM95 cells and susceptibility to HIV-1 envelope glycoprotein-triggered membrane fusion.

Abstract We had previously reported that glycosphingolipids(GSL) support human immunodeficiency virus type 1 (HIV-1) entry. In this study, we further examined this issue by expressing HIV-1 receptors in GSL-deficient GM95 cells. GM95 cells expressing low levels of CD4 and CXCR4or CCR5 did not support HIV-1 Env-mediated fusion. However, higher expression of these receptors rendered GM95 cells highly susceptible to fusion with cells expressing appropriate HIV-1 envelope glycoproteins (HIV-1 Envs). The GM95 cells exhibited a different fusion phenotype when compared with GSL + NIH3T3 cells bearing similar receptor levels. Fusion of GM95 targets expressing higher levels of CD4 and coreceptors occurred at 25°C and was sensitive to cholesterol depletionor disruption of the cytoskeleton. In contrast, the fusion threshold of NIH3T3CD4X4/R5 targets was at ≥28°C as previously reported and was insensitive to cholesterol depletionor cytoskeletal network disruption. On the basis of these observations, we propose that target membrane GSLs support HIV-1 Env-mediated fusion at low density of receptors by stabilizing receptor pools in natural targets.