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

J Virol. 1998 Sep;72(9):7280-8. doi: 10.1128/JVI.72.9.7280-7288.1998.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Binding Sites
  • CD4 Antigens / metabolism*
  • CHO Cells
  • Cell Membrane / metabolism
  • Conserved Sequence*
  • Cricetinae
  • Gene Expression
  • HIV Envelope Protein gp120 / genetics*
  • HIV Envelope Protein gp120 / metabolism*
  • HIV-1 / genetics
  • HIV-1 / metabolism*
  • HeLa Cells
  • Humans
  • Molecular Sequence Data
  • Receptors, CXCR4 / metabolism*
  • Solubility
  • Tumor Cells, Cultured

Substances

  • CD4 Antigens
  • HIV Envelope Protein gp120
  • Receptors, CXCR4