CXCR4 function requires membrane cholesterol: implications for HIV infection.
HIV requires cholesterol and lipid rafts on target cell membranes for infection. To elucidate a possible mechanism, we determined that cholesterol extraction by hydroxypropyl-beta-cyclodextrin (BCD) inhibits stromal cell-derived factor 1alpha (SDF-1alpha) binding to CXCR4 on T cell lines and PBMCs. Intracellular calcium responses to SDF-1alpha, as well as receptor internalization, were impaired in treated T cells. Loss in ligand binding is likely due to conformational changes in CXCR4 and not increased sensitivity to internalization. SDF-1alpha binding and calcium responses were effectively restored by reloading cholesterol. Immunofluorescence microscopy revealed that SDF-1alpha binding occurred in lipid raft microdomains that contained GM1. CXCR4 surface expression, on the other hand, only partially colocalized with GM1. HIV-1(IIIB) infection assays confirmed the functional loss of CXCR4 in the cell lines tested, Sup-T1 and CEM-NKR-CCR5. These data suggest that cholesterol is essential for CXCR4 conformation and function and that lipid rafts may play a regulatory role in SDF-1alpha signaling.
Nguyen
Dzung H
DH
National Institute on Aging, National Institutes of Health, Gerontology Research Center, Baltimore, MD 21224, USA.
Taub
Dennis
D
D000073738:2-Hydroxypropyl-beta-cyclodextrin; D019380:Anti-HIV Agents / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000378:metabolism; D001666:Binding Sites, Antibody / Q000187:drug effects; D002118:Calcium / Q000037:antagonists & inhibitors / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism / Q000502:physiology / Q000821:virology; D054377:Chemokine CXCL12; D019743:Chemokines, CXC / Q000037:antagonists & inhibitors / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism / Q000502:physiology*; D002999:Clone Cells; D003505:Cyclodextrins / Q000494:pharmacology; D005079:Excipients / Q000494:pharmacology; D015658:HIV Infections / Q000276:immunology / Q000378:metabolism / Q000517:prevention & control; D015497:HIV-1 / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism; D019169:Jurkat Cells; D021962:Membrane Microdomains / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects / Q000276:immunology; D019718:Receptors, CXCR4 / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism / Q000821:virology; D047392:beta-Cyclodextrins
D019380:Anti-HIV Agents; D000911:Antibodies, Monoclonal; C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D019743:Chemokines, CXC; D003505:Cyclodextrins; D005079:Excipients; D019718:Receptors, CXCR4; D047392:beta-Cyclodextrins; D000073738:2-Hydroxypropyl-beta-cyclodextrin; D002784:Cholesterol; D002118:Calcium