Evidence for budding of human immunodeficiency virus type 1 selectively from glycolipid-enriched membrane lipid rafts

A number of recent studies have demonstrated the significance of detergent- insoluble, glycolipid-enriched membrane domains or lipid rafts, especially in regard to activation and signaling in T lymphocytes. These domains can b e viewed as Boating rafts composed of sphingolipids and cholesterol which s equester glycosylphosphatidylinositol (GPI)-linked proteins, such as Thy-1 and CD59. CD45, a 200-kDa transmembrane phosphatase protein, is excluded fr om these domains. We have found that human immunodeficiency virus type 1 (H IV-1) particles produced by infected T-cell lines acquire the GPI-linked pr oteins Thy-1 and CD59, as cu-ell as the ganglioside GM1, which is known to partition preferentially into lipid rafts. In contrast, despite its high ex pression on the cell surface, CD45 was poorly incorporated into virus parti cles. Confocal fluorescence microscopy revealed that HEV-I proteins colocal ized with Thy-1, CD59, GM1, and a lipid raft-specific fluorescent lipid, Di IC(16)(3), in uropods of infected Jurkat cells. CD45 did not colocalize wit h HIV-1 proteins and was excluded from uropods. Dot immunoassay of Triton X -100-extracted membrane fractions revealed that HIV-1 p17 matrix protein an d gp41 were present in the detergent-resistant fractions and that [H-3]myri stic acid-labeled HIV Gag showed a nine-to-one enrichment in lipid rafts. W e propose a model for the budding of HIV virions through lipid rafts whereb y host cell cholesterol, sphingolipids, and GPI-linked proteins within thes e domains are incorporated into the viral envelope, perhaps as a result of preferential sorting of HIV Gag to lipid rafts.