Early intermediates in HIV-1 envelope glycoprotein-mediated fusion triggered by CD4 and co-receptor complexes.
An early step in the process of HIV-1 entry into target cells is the activation of its envelope glycoprotein (GP120-GP41) to a fusogenic state upon binding to target cell CD4 and cognate co-receptor. Incubation of human immunodeficiency virus (HIV)-1 Env-expressing cells with an excess of CD4 and co-recepeptor-bearing target cells resulted in an influx of an impermeant nucleic acid-staining fluorescent dye into the Env-expressing cells. The dye influx occurred concomitant with cell fusion. No influx of dye into target cells was observed if they were incubated with an excess of Env-expressing cells. The permeabilization of Env-expressing cells was also triggered by CD4.co-receptor complexes attached to Protein G-Sepharose beads in the absence of target cells. The CD4 and co-receptor-induced permeabilization of Env-expressing cells occurred with the same specificity with respect to co-receptor usage as cell fusion. Natural ligands for the co-receptors and C-terminal GP41 peptide inhibitors of HIV-1 fusion blocked this effect. Our results indicate that the process of HIV-1 Env-mediated fusion is initiated by the destabilization of HIV-1 Env-expressing membranes. Further elucidation of these early intermediates may help identify and develop potential inhibitors of HIV-1 entry into cells.
Dimitrov
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AS
Laboratory of Experimental and Computational Biology, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702, USA.
Xiao
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Dimitrov
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Blumenthal
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D016475:3T3 Cells; D000818:Animals; D015704:CD4 Antigens / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism / Q000821:virology; D002478:Cells, Cultured; D004396:Coloring Agents / Q000494:pharmacology; D005452:Fluoresceins / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000494:pharmacology; D015699:HIV Envelope Protein gp120 / Q000737:chemistry* / Q000378:metabolism*; D015700:HIV Envelope Protein gp41 / Q000737:chemistry* / Q000378:metabolism*; D015497:HIV-1 / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008024:Ligands; D051379:Mice; D009930:Organic Chemicals; D011233:Precipitin Tests; D011485:Protein Binding; D012685:Sepharose / Q000378:metabolism; D013997:Time Factors; D014616:Vaccinia virus / Q000235:genetics; D014760:Viral Fusion Proteins / Q000737:chemistry*
D015704:CD4 Antigens; D004396:Coloring Agents; D005452:Fluoresceins; D005456:Fluorescent Dyes; D015699:HIV Envelope Protein gp120; D015700:HIV Envelope Protein gp41; D008024:Ligands; D009930:Organic Chemicals; C416802:SYTOX Orange dye; D014760:Viral Fusion Proteins; D012685:Sepharose; C007740:fluorexon