Role of CD4 hinge region in GP120 utilization by immunoglobulin domain 1.
Immunoglobulin-like domain 1 of CD4 (D1-CD4) promotes HIV infection by binding the envelope glycoprotein (ENV) and exposing its coreceptor-binding site. To study CD4-ENV-coreceptor interactions, we characterized hybrid receptors having domains 1 and 2 of CD4 (D1D2-CD4) joined to the N-terminus of chemokine receptors CCR5, CXCR4, CXCR2, and DARC. Hybrid receptors showed conserved ENV-coreceptor specificity in cell-cell fusion assays. Although D1D2-CD4-CCR5 was sufficient to permit ENV-mediated fusion, D1-CD4-CCR5 and human D1/mouse D2-CD4-CCR5 lacked CD4 function and binding to a neutralizing antibody mapped to D1-CD4. Chimeric D1D2-CD4 joined to CCR5 revealed that the C-terminal 20 residues of human D2-CD4 are required for efficient ENV-mediated fusion. Mutagenesis of hybrid receptors showed the importance of residues forming D1-D2 CD4 interdomain contacts and hinge region proximal residues. Mutagenesis of WT human CD4 confirmed that residues forming D1-D2 interdomain contacts and hinge-region proximal residues contribute positively to CD4 activity in the full-length receptor.
Murray
James L
JL
Henry Vogt Cancer Research Center, University of Louisville, Louisville, Kentucky 40202, USA.
Hu
Qin-xue
QX
Navenot
Jean-Marc
JM
Peiper
Stephen C
SC
D000595:Amino Acid Sequence; D000818:Animals; D015704:CD4 Antigens / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002459:Cell Fusion; D002460:Cell Line; D015699:HIV Envelope Protein gp120 / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D007128:Immunoglobulin Fragments / Q000737:chemistry; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary; D019707:Receptors, Chemokine / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000378:metabolism
D015704:CD4 Antigens; D015699:HIV Envelope Protein gp120; D007128:Immunoglobulin Fragments; D019707:Receptors, Chemokine; D011993:Recombinant Fusion Proteins