Dissociation of the CD4 and CXCR4 binding properties of human immunodeficiency virus type 1 gp120 by deletion of the first putative alpha-helical conserved structure.
To evaluate conserved structures of the surface gp120 subunit (SU) of the human immunodeficiency virus type 1 (HIV-1) envelope in gp120-cell interactions, we designed and produced an HIV-1 IIIB (HXB2R) gp120 carrying a deletion of amino acids E61 to S85. This sequence corresponds to a highly conserved predicted amphipathic alpha-helical structure located in the gp120 C1 region. The resultant soluble mutant with a deleted alpha helix 1 (gp120 DeltaalphaHX1) exhibited a strong interaction with CXCR4, although CD4 binding was undetectable. The former interaction was specific since it inhibited the binding of the anti-CXCR4 monoclonal antibody (12G5), as well as SDF1alpha, the natural ligand of CXCR4. Additionally, the mutant gp120 was able to bind to CXCR4(+)/CD4(-) cells but not to CXCR4(-)/CD4(-) cells. Although efficiently expressed on cell surface, HIV envelope harboring the deleted gp120 DeltaalphaHX1 associated with wild-type transmembrane gp41 was unable to induce cell-to-cell fusion with HeLa CD4(+) cells. Nevertheless, the soluble gp120 DeltaalphaHX1 efficiently inhibited a single round of HIV-1 LAI infection in HeLa P4 cells, with a 50% inhibitory concentration of 100 nM. Our data demonstrate that interaction with the CXCR4 coreceptor was maintained in a SUgp120 HIV envelope lacking alphaHX1. Moreover, in the absence of CD4 binding, the interaction of gp120 DeltaalphaHX1 with CXCR4 was sufficient to inhibit HIV-1 infection.
Missé
D
D
Laboratoire d'Immunologie Rétrovirale, Institut Français de Recherches pour le Développement en Coopération, 34032 Montpellier, France.
Cerutti
M
M
Schmidt
I
I
Jansen
A
A
Devauchelle
G
G
Jansen
F
F
Veas
F
F
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D015704:CD4 Antigens / Q000378:metabolism*; D016466:CHO Cells; D002462:Cell Membrane / Q000378:metabolism; D017124:Conserved Sequence; D006224:Cricetinae; D015870:Gene Expression; D015699:HIV Envelope Protein gp120 / Q000235:genetics* / Q000378:metabolism*; D015497:HIV-1 / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D019718:Receptors, CXCR4 / Q000378:metabolism*; D012995:Solubility; D014407:Tumor Cells, Cultured
D015704:CD4 Antigens; D015699:HIV Envelope Protein gp120; D019718:Receptors, CXCR4