title: CD4-Chemokine receptor hybrids in human immunodeficiency virus type 1 infection.
abstract: Most human immunodeficiency virus (HIV) strains require both CD4 and a chemokine receptor for entry into a host cell. In order to analyze how the HIV-1 envelope glycoprotein interacts with these cellular molecules, we constructed single-molecule hybrids of CD4 and chemokine receptors and expressed these constructs in the mink cell line Mv-1-lu. The two N-terminal (2D) or all four (4D) extracellular domains of CD4 were linked to the N terminus of the chemokine receptor CXCR4. The CD4(2D)CXCR4 hybrid mediated infection by HIV-1(LAI) to nearly the same extent as the wild-type molecules, whereas CD4(4D)CXCR4 was less efficient. Recombinant SU(LAI) protein competed more efficiently with the CXCR4-specific monoclonal antibody 12G5 for binding to CD4(2D)CXCR4 than for binding to CD4(4D)CXCR4. Stromal cell-derived factor 1 (SDF-1) blocked HIV-1(LAI) infection of cells expressing CD4(2D)CXCR4 less efficiently than for cells expressing wild-type CXCR4 and CD4, whereas down-modulation of CXCR4 by SDF-1 was similar for hybrids and wild-type CXCR4. In contrast, the bicyclam AMD3100, a nonpeptide CXCR4 ligand that did not down-modulate the hybrids, blocked hybrid-mediated infection at least as potently as for wild-type CXCR4. Thus SDF-1, but not the smaller molecule AMD3100, may interfere at multiple points with the binding of the surface unit (SU)-CD4 complex to CXCR4, a mechanism that the covalent linkage of CD4 to CXCR4 impedes. Although the CD4-CXCR4 hybrids yielded enhanced SU interactions with the chemokine receptor moiety, this did not overcome the specific coreceptor requirement of different HIV-1 strains: the X4 virus HIV-1(LAI) and the X4R5 virus HIV-1(89. 6), unlike the R5 strain HIV-1(SF162), infected Mv-1-lu cells expressing the CD4(2D)CXCR4 hybrid, but none could use hybrids of CD4 and the chemokine receptor CCR2b, CCR5, or CXCR2. Thus single-molecule hybrid constructs that mimic receptor-coreceptor complexes can be used to dissect coreceptor function and its inhibition.
authors.affiliation: MRC Laboratory for Molecular Cell Biology and Department of Biochemistry and Molecular Biology, University College London, London WC1E 6BT, United Kingdom. p.klasse@ucl.ac.uk
authors.forename: P J
authors.initials: PJ
authors.lastname: Klasse
authors.forename: M M
authors.initials: MM
authors.lastname: Rosenkilde
authors.forename: N
authors.initials: N
authors.lastname: Signoret
authors.forename: A
authors.initials: A
authors.lastname: Pelchen-Matthews
authors.forename: T W
authors.initials: TW
authors.lastname: Schwartz
authors.forename: M
authors.initials: M
authors.lastname: Marsh
mesh_terms: D000818:Animals; D019380:Anti-HIV Agents / Q000378:metabolism; D000911:Antibodies, Monoclonal; D001596:Benzylamines; D001667:Binding, Competitive; D015704:CD4 Antigens / Q000235:genetics / Q000378:metabolism*; D019556:COS Cells; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D054377:Chemokine CXCL12; D019743:Chemokines, CXC / Q000378:metabolism; D000080027:Cyclams; D015536:Down-Regulation; D015870:Gene Expression; D015699:HIV Envelope Protein gp120 / Q000378:metabolism; D015497:HIV-1 / Q000378:metabolism* / Q000502:physiology; D006571:Heterocyclic Compounds / Q000378:metabolism; D006801:Humans; D008907:Mink; D055503:Protein Multimerization; D019718:Receptors, CXCR4 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D019380:Anti-HIV Agents; D000911:Antibodies, Monoclonal; D001596:Benzylamines; D015704:CD4 Antigens; C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D019743:Chemokines, CXC; D000080027:Cyclams; D015699:HIV Envelope Protein gp120; D006571:Heterocyclic Compounds; D019718:Receptors, CXCR4; C088327:plerixafor