Abstract
The human immunodeficiency virus type 1 (HIV-1) external envelope glycoprotein gp120 presents conserved binding sites for binding to the primary virus receptor CD4 as well as the major HIV chemokine coreceptors, CCR5 and CXCR4.Concerted efforts are underway to understand the specific interactions between gp120 and coreceptors as well as their contribution to the subsequent membrane fusion process.The present review summarizes the current knowledge on this biological aspect, which represents one of the key and essential points of the HIV-host cell interplay and HIV life cycle. The relevance of conformational HIV-1 Envelope proteins presented on Virus-like Particles for appropriate assessment of this molecular interaction, is also discussed.
Highlights
The molecular interaction between human immunodeficiency virus type 1 (HIV-1) gp120, in its trimeric conformation, and the CD4 receptor on the host cell surface represents the first step of the HIV infection cycle
The molecular interaction of HIV gp120 with the CD4 receptor and, subsequently, with the CCR5 or CXCR4 coreceptor leads to the insertion of the hydrophobic gp41 N-terminal region into the host cell membrane
The interaction between HIV particles and target host cells is a defined temporally sequential stepwise process, characterized by the binding of surface gp120 Envelope protein to CD4 receptor and subsequent binding of the gp120-CD4 complex to chemokines coreceptors. This will lead to membrane fusion and host cell infection
Summary
The molecular interaction between HIV-1 gp120, in its trimeric conformation, and the CD4 receptor on the host cell surface represents the first step of the HIV infection cycle. The molecular interaction of SIV envelope protein with the CD4 receptor and coreceptors leads to conformational changes in the gp ectodomain trimers and exposure of the fusion peptide which closely resemble what described for the HIV-1 counterpart [72,73]. Stable trimeric forms of human immunodeficiency virus recombinant gp140 As described above, the envelope proteins on the virus surface are assembled into trimers, consisting of three gp120 molecules associated non-covalently with three gp subunits, which interact sequentially with the CD4 receptor and the chemokine coreceptors, leading to viral and cell membrane fusion. Considering the biological and structural properties of HIV gp140 trimers presented on the VLP surface, they can be even more strategic for binding studies, providing an invaluable tool for evaluating and dissecting the whole virus-host cell interaction leading to and ending with membrane fusion [163,164] (Fig. 2)
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