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J Immunol. 2002 Apr 15;168(8):4121-6.

CXCR4 function requires membrane cholesterol: implications for HIV infection.

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National Institute on Aging, National Institutes of Health, Gerontology Research Center, Baltimore, MD 21224, USA.


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.

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