Abstract
The contribution of raft domains to human immunodeficiency virus (HIV) 1 entry was assessed. In particular, we asked whether the CD4 and CCR5 HIV-1 receptors need to associate with sphingolipid-enriched, detergent-resistant membrane domains (rafts) to allow viral entry into primary and T-cell lines. Based on Triton X-100 solubilization and confocal microscopy, CD4 was shown to distribute partially to rafts. In contrast, CCR5 did not associate with rafts and localized in nonraft plasma membrane domains. HIV-1-receptor partitioning remained unchanged upon viral adsorption, suggesting that viral entry probably takes place outside rafts. To directly investigate this possibility, we targeted CD4 to nonraft domains of the membrane by preventing CD4 palmitoylation and interaction with p56(lck). Directed mutagenesis of both targeting signals significantly prevented association of CD4 with rafts, but did not suppress the HIV-1 receptor function of CD4. Collectively, these results strongly suggest that the presence of HIV-1 receptors in rafts is not required for viral infection. We show, however, that depleting plasma membrane cholesterol inhibits HIV-1 entry. We therefore propose that cholesterol modulates the HIV-1 entry process independently of its ability to promote raft formation.
Highlights
Numerous studies dealing with biological membrane organization and composition have emphasized the nonrandom distribution of lipids and proteins into distinct membrane domains [1]
We show that depleting plasma membrane cholesterol in target cells inhibits viral entry, suggesting that cholesterol-dependent membrane properties other than raft formation come into play to promote efficient human immunodeficiency virus (HIV)-1 infection
We controlled that the cholesterol deficit was maintained throughout the 4-h post-infection experiment and was not detrimental to cell viability or plasma membrane expression of human immunodeficiency virus type 1 (HIV-1) receptors CD4 and CCR5
Summary
Numerous studies dealing with biological membrane organization and composition have emphasized the nonrandom distribution of lipids and proteins into distinct membrane domains [1]. Nonionic detergent insolubility of these domains at 4 °C was found to result from tight packing of cholesterol and sphingolipids in a liquid-ordered state [3] This property allows recovery of rafts as lowdensity, floating membranes by gradient centrifugation and makes it possible to characterize raft lipids and proteins [4]. Considering that inhibition of glycosphingolipids synthesis is not detrimental to raft domain formation [19], and that cholesterol is distributed throughout plasma membranes (20 –22), inhibition of HIV-1 entry following these two means of lipid perturbation (14 –17) cannot be attributed solely to disruption of rafts. It is conceivable that C-terminal palmitoylation of CD4 [27] might account for localization of this protein to rafts This prompted us to investigate whether interference with CD4 palmitoylation would alter the distribution of the CD4 receptor to rafts.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
