Evidence for Budding of Human Immunodeficiency Virus Type 1 Selectively from Glycolipid-Enriched Membrane Lipid Rafts

TLDR

Detergent‑insoluble, glycolipid‑enriched membrane domains or lipid rafts are key to T‑cell activation and signaling, comprising sphingolipids and cholesterol that sequester GPI‑linked proteins such as Thy‑1 and CD59 while excluding CD45. The study proposes a model in which HIV‑1 virions bud through lipid rafts, incorporating host cholesterol, sphingolipids, and GPI‑linked proteins into the viral envelope. The mechanism posits that HIV Gag preferentially localizes to lipid rafts, driving the sorting of these host components into the budding virion. HIV‑1 particles from infected T cells acquire GPI‑linked proteins Thy‑1, CD59, and ganglioside GM1 but exclude CD45; viral proteins colocalize with raft markers in uropods, and Gag is enriched nine‑to‑one in detergent‑resistant lipid raft fractions.

Abstract

ABSTRACT 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 be viewed as floating rafts composed of sphingolipids and cholesterol which sequester glycosylphosphatidylinositol (GPI)-linked proteins, such as Thy-1 and CD59. CD45, a 200-kDa transmembrane phosphatase protein, is excluded from these domains. We have found that human immunodeficiency virus type 1 (HIV-1) particles produced by infected T-cell lines acquire the GPI-linked proteins Thy-1 and CD59, as well as the ganglioside GM1, which is known to partition preferentially into lipid rafts. In contrast, despite its high expression on the cell surface, CD45 was poorly incorporated into virus particles. Confocal fluorescence microscopy revealed that HIV-1 proteins colocalized with Thy-1, CD59, GM1, and a lipid raft-specific fluorescent lipid, DiIC 16 (3), in uropods of infected Jurkat cells. CD45 did not colocalize with HIV-1 proteins and was excluded from uropods. Dot immunoassay of Triton X-100-extracted membrane fractions revealed that HIV-1 p17 matrix protein and gp41 were present in the detergent-resistant fractions and that [ 3 H]myristic acid-labeled HIV Gag showed a nine-to-one enrichment in lipid rafts. We propose a model for the budding of HIV virions through lipid rafts whereby host cell cholesterol, sphingolipids, and GPI-linked proteins within these domains are incorporated into the viral envelope, perhaps as a result of preferential sorting of HIV Gag to lipid rafts.