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Published on: September 1, 2015
CD4-Chemokine receptor hybrids in human immunodeficiency virus type 1 infection
P J Klasse1, M M Rosenkilde, N Signoret
1MRC 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
Insights
Researchers created hybrid molecules of CD4 and chemokine receptors to study human immunodeficiency virus (HIV) entry. The CD4(2D)CXCR4 hybrid effectively mediated HIV infection, aiding in understanding coreceptor function and inhibition.
Area of Science:
- Virology
- Immunology
- Molecular Biology
Background:
- Human immunodeficiency virus (HIV) entry into host cells requires CD4 and a chemokine receptor.
- Understanding the interaction between HIV envelope glycoprotein and these cellular molecules is crucial.
Purpose of the Study:
- To analyze how the HIV-1 envelope glycoprotein interacts with CD4 and chemokine receptors.
- To construct and utilize single-molecule hybrids of CD4 and chemokine receptors to dissect coreceptor function.
Main Methods:
- Construction and expression of single-molecule hybrids of CD4 and chemokine receptors (CXCR4, CCR2b, CCR5, CXCR2) in Mv-1-lu cells.
- Testing HIV-1 strain infection mediated by these hybrids.
- Investigating the binding competition of recombinant SU(LAI) protein with antibody 12G5.
- Assessing the inhibitory effects of Stromal cell-derived factor 1 (SDF-1) and AMD3100 on infection.
Main Results:
- The CD4(2D)CXCR4 hybrid mediated HIV-1(LAI) infection efficiently, while CD4(4D)CXCR4 was less effective.
- Recombinant SU(LAI) protein showed higher binding affinity to CD4(2D)CXCR4 than CD4(4D)CXCR4.
- SDF-1 inhibition was less efficient for hybrids, but AMD3100 inhibition was potent.
- Different HIV-1 strains exhibited specific coreceptor requirements, with X4 and X4R5 viruses infecting cells with CD4(2D)CXCR4, but not other hybrids.
Conclusions:
- Single-molecule hybrid constructs effectively mimic receptor-coreceptor complexes for dissecting coreceptor function.
- The covalent linkage of CD4 to CXCR4 impedes certain inhibition mechanisms of HIV entry.
- Specific HIV-1 strains demonstrate distinct coreceptor usage, highlighting the complexity of viral tropism.
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.
