CD4-Independent Infection by HIV-2 Is Mediated by Fusin/CXCR4

Endres, M.; Clapham, Paul R.; Marsh, Mark; Ahuja, Menaka; Turner, Julie D.; McKnight, Áine; Thomas, Jill F.; Stoebenau-Haggarty, Beth; Choe, Sunny; Vance, Patricia J.; Wells, Timothy N.C.; Power, Christine; Sutterwala, Shaheen; Doms, Robert W.; Landau, Nathaniel R.; Hoxie, James A.

doi:10.1016/s0092-8674(00)81393-8

Cited by 629 publications

(491 citation statements)

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“…Fig. 1A shows FACS analysis with the CXCR4-specific 12G5 antibody (14). The epitope tag-specific 12CA5 antibody was used to immunoprecipitate the Wt CXCR4 (ϳ44 kDa) and ⌬Cyto CXCR4 (ϳ41 kDa) proteins from surfaceiodinated RBL cells (Fig.…”

Section: Resultsmentioning

confidence: 99%

Regulation of Human Chemokine Receptors CXCR4

Haribabu

Richardson

Fisher

et al. 1997

Journal of Biological Chemistry

258

100

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Members of the chemokine receptor family CCR5 and CXCR4 have recently been shown to be involved in the entry of human immunodeficiency virus (HIV) into target cells. Here, we investigated the regulation of CXCR4 in rat basophilic leukemia cells (RBL-2H3) stably transfected with wild type (Wt CXCR4) or a cytoplasmic tail deletion mutant (⌬Cyto CXCR4) of CXCR4. The ligand, stromal cell derived factor-1 (SDF-1) stimulated higher G-protein activation, inositol phosphate generation, and a more sustained calcium elevation in cells expressing ⌬Cyto CXCR4 relative to Wt CXCR4. SDF-1 and phorbol 12-myristate 13-acetate (PMA), but not a membrane permeable cAMP analog induced rapid phosphorylation as well as desensitization of Wt CXCR4. Phosphorylation of ⌬Cyto CXCR4 was not detected under any of these conditions. Despite lack of receptor phosphorylation, calcium mobilization by SDF-1 in ⌬Cyto CXCR4 cells was partially desensitized by prior treatment with SDF-1. Of interest, the rapid release of calcium was inhibited without affecting the sustained calcium elevation, indicating independent regulatory pathways for these processes. PMA completely inhibited phosphoinositide hydrolysis and calcium mobilization in Wt CXCR4 but only partially inhibited these responses in ⌬Cyto CXCR4. cAMP also partially inhibited these responses in both Wt CXCR4 and ⌬Cyto CXCR4. SDF-1, PMA, and cAMP caused phosphorylation of phospholipase C␤3 in Wt and ⌬Cyto CXCR4 cells. Both SDF-1 as well as PMA induced rapid internalization of Wt CXCR4. SDF-1 but not PMA induced internalization of ⌬Cyto CXCR4 albeit at reduced levels relative to Wt CXCR4. These results indicate that signaling and internalization of CXCR4 are regulated by receptor phosphorylation dependent and independent mechanisms. Desensitization of CXCR4 signaling, independent of receptor phosphorylation, appears to be a consequence of the phosphorylation of phospholipase C␤3.Chemokines are a group of proteins that mediate directed migration and activation of leukocytes (1). These have been classified into two main families, CXC or CC-chemokines. Two newly identified proteins define additional groups of C and CX3C chemokines based on the position of conserved cysteines (2, 3). Both CC and CXC chemokines bind to seven transmembrane G-protein-coupled receptors which transduce signals through heterotrimeric G-proteins (4). Several recent studies showed that chemokines play a significant role in human immunodeficiency virus (HIV-1) 1 infection and that the chemokine receptors CCR5 and CXCR4 along with CD4 act as major co-receptors for the macrophage tropic and T-cell tropic HIV-1 strains entry, respectively, into target cells (5-10). While the C-C chemokines such as MIP1␣, MIP1␤, and regulated upon activation, normal T expressed and secreted can activate CCR5 the CXC chemokine SDF-1 is the ligand for CXCR4 (11-13). Recently, CD4 independent infection by HIV-2 was shown to be mediated by CXCR4 (14). HIV-1 envelope glycoproteins interact with chemokine receptors in a CD4-dependent and in one case...

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Section: Resultsmentioning

confidence: 99%

Regulation of Human Chemokine Receptors CXCR4

Haribabu

Richardson

Fisher

et al. 1997

Journal of Biological Chemistry

258

100

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“…For CXCR4, laboratory-adapted HIV-1 strains and primary R5X4 isolates bind more weakly, with K d s of between 200 and 500 nM (3,28). Whether relatively poor affinity for CXCR4 will prove to be a general feature of X4 HIV-1 strains is not known, though high-affinity interactions with CXCR4 are possible, as evidenced by HIV-2 VCP and HIV-2 ROD/B (35 CXCR4-positive cells independently of CD4 (24,43), due perhaps in part to their high affinity for this coreceptor. While we did not directly measure the affinity with which the various YU-2 gp120 proteins interacted with CCR5, we can conclude that those which bound below the limit of detection in the equilibrium binding assay did so with affinities of Ͼ100 nM.…”

Section: Discussionmentioning

confidence: 99%

Impact of Mutations in the Coreceptor Binding Site on Human Immunodeficiency Virus Type 1 Fusion, Infection, and Entry Inhibitor Sensitivity

Reeves

Miamidian

Biscone

et al. 2004

J Virol

106

111

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An increasingly large number of antiviral agents that prevent entry of human immunodeficiency virus (HIV) into cells are in preclinical and clinical development. The envelope (Env) protein of HIV is the major viral determinant that affects sensitivity to these compounds. To understand how changes in Env can impact entry inhibitor sensitivity, we introduced six mutations into the conserved coreceptor binding site of the R5 HIV-1 strain YU-2 and measured the effect of these changes on CD4 and coreceptor binding, membrane fusion levels and rates, virus infection, and sensitivity to the fusion inhibitors enfuvirtide (T-20) and T-1249, the CCR5 inhibitor TAK-779, and an antibody to CD4. The mutations had little effect on CD4 binding but reduced CCR5 binding to various extents. In general, reductions in coreceptor binding efficiency resulted in slower fusion kinetics and increased sensitivity to TAK-779 and enfuvirtide. In addition, low CCR5 binding usually reduced overall fusion and infection levels. However, one mutation adjacent to the bridging sheet ␤21 strand, P438A, had little effect on fusion activity, fusion rate, infectivity, or sensitivity to enfuvirtide or T-1249 despite causing a marked reduction in CCR5 binding and a significant increase in TAK-779 sensitivity. Thus, our findings indicate that changes in the coreceptor binding site of Env can modulate its fusion activity, infectivity, and entry inhibitor sensitivity by multiple mechanisms and suggest that reductions in coreceptor binding do not always result in prolonged fusion kinetics and increased sensitivity to enfuvirtide.

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“…47,93,94 Furthermore, anti-human CXCR4 or CXCL12 antibodies also significantly impair metastasis and progression of non-Hodgkin's lymphoma, breast, lung and prostate tumors in animal models. [95][96][97][98] The unique properties of monoclonal antibody (mAb) therapies, including their high affinity and specificity, and the differential expression of target antigen in tumor cells versus normal cells make them attractive agents for cancer immunotherapy.…”

Section: Development Antibodies To Cxcr4mentioning

confidence: 99%