Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019693 (HIV)
 170,526 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The retroviral encoded protein integrase (IN) is required for the insertion of the human immunodeficiency virus type 1 (HIV-1) proviral DNA into the host genome. In spite of the crucial role played by IN in the retroviral life cycle, which makes this enzyme an attractive target for the development of new anti-AIDS agents, very few inhibitors have been described and none seems to have a potential use in anti-HIV therapy. To obtain potent and specific IN inhibitors, we used the two-hybrid system to isolate short peptides. Using HIV-1 IN as a bait and a yeast genomic library as the source of inhibitory peptides (prey), we isolated a 33-mer peptide (I33) that bound tightly to the enzyme. I33 inhibited both in vitro IN activities, i.e. 3' end processing and strand transfer. Further analysis led us to select a shorter peptide, EBR28, corresponding to the N-terminal region of I33. Truncated variants showed that EBR28 interacted with the catalytic domain of IN interfering with the binding of the DNA substrate. Alanine single substitution of each EBR28 residue (alanine scanning) allowed the identification of essential amino acids involved in the inhibition. The EBR28 NMR structure shows that this peptide adopts an alpha-helical conformation with amphipathic properties. Additionally, EBR28 showed a significant antiviral effect when assayed on HIV-1 infected human cells. Thus, this potentially important short lead peptide may not only be helpful to design new anti-HIV agents, but also could prove very useful in further studies of the structural and functional characteristics of HIV-1 IN.
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PMID:A novel short peptide is a specific inhibitor of the human immunodeficiency virus type 1 integrase. 1205 67

The envelope glycoprotein complex (gp120-gp41) of human immunodeficiency virus type 1 (HIV-1) promotes the fusion of viral and cellular membranes through formation of the fusion-active six-helix bundle in the gp41 ectodomain. This gp41 core structure consists of three C-terminal helices packed in an antiparallel manner into hydrophobic grooves on the surface of the N-terminal trimeric coiled coil. Alanine mutations that destabilize the N- and C-terminal interhelical packing interactions also reduce viral infectivity. Here we show that viruses bearing these mutations exhibit a marked potentiation of inhibition by peptides that make up the gp41 core. By contrast, these viruses are unchanged in their sensitivities to soluble CD4, the CXCR4 coreceptor ligand SDF-1alpha, and human anti-HIV immunoglobulin, reagents that impact the initial, receptor-induced conformational changes in the envelope glycoprotein. Our results support the notion that these alanine mutations specifically affect the conformational transition to the fusion-active gp41 structure. The mutations also increase viral sensitivity to the gp41-directed monoclonal antibody 2F5, suggesting that this broadly neutralizing antibody may also interfere with this transition. The conformational activation of the HIV-1 envelope glycoprotein likely represents a viable target for vaccine and antiviral drug development.
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PMID:Genetic evidence that interhelical packing interactions in the gp41 core are critical for transition of the human immunodeficiency virus type 1 envelope glycoprotein to the fusion-active state. 1207 35

Human immunodeficiency virus type 1 (HIV-1) entry is mediated by the consecutive interaction of the envelope glycoprotein gp120 with CD4 and a coreceptor such as CCR5 or CXCR4. The CCR5 coreceptor is used by the most commonly transmitted HIV-1 strains that often persist throughout the course of infection. Compounds targeting CCR5-mediated entry are a novel class of drugs being developed to treat HIV-1 infection. In this study, we have identified the mechanism of action of two inhibitors of CCR5 function, SCH-350581 (AD101) and SCH-351125 (SCH-C). AD101 is more potent than SCH-C at inhibiting HIV-1 replication in primary lymphocytes, as well as viral entry and gp120 binding to cell lines. Both molecules also block the binding of several anti-CCR5 monoclonal antibodies that recognize epitopes in the second extracellular loop of CCR5. Alanine mutagenesis of the transmembrane domain of CCR5 suggests that AD101 and SCH-C bind to overlapping but nonidentical sites within a putative ligand-binding cavity formed by transmembrane helices 1, 2, 3, and 7. We propose that the binding of small molecules to the transmembrane domain of CCR5 may disrupt the conformation of its extracellular domain, thereby inhibiting ligand binding to CCR5.
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PMID:Analysis of the mechanism by which the small-molecule CCR5 antagonists SCH-351125 and SCH-350581 inhibit human immunodeficiency virus type 1 entry. 1269 22

The Vpx protein of human immunodeficiency virus type 2 (HIV-2) is a viral accessory protein related to, but distinct from, the Vpr protein of HIV-1. Vpx is packaged into virions and, as a component of the viral preintegration complex (PIC), Vpx is required for efficient virus replication in nondividing cells. Therefore, the localization of Vpx in cells is dynamic and dependent upon discrete domains of the protein. Expressed in the absence of other viral proteins, Vpx localizes to the nucleus of cells. However, if expressed with the Gag protein of HIV-2, Vpx localizes to the plasma membrane of cells. To further understand the regulation of Vpx localization, we fused regions of Vpx to beta-galactosidase to identify regions of the protein sufficient to mediate nuclear localization. The minimal transferable region of Vpx that conferred nuclear localization in these assays was aa 65 to 72. Alanine substitution of K(68) and R(70) in a GFP-Vpx construct abolished nuclear localization, suggesting that the basic residues in this region are important for nuclear import. Analysis of the membrane transport of several GFP-Vpx alanine mutants demonstrated that while separable, the domains of Vpx required for nuclear localization are not distinct from the domains required for membrane transport. The results of heterokaryon shuttling assays indicated that Vpx is not a shuttling protein; however, HIV-2 Vpr did shuttle similar to HIV-1 Vpr.
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PMID:Identification of the nuclear localization signal of human immunodeficiency virus type 2 Vpx. 1283 98

A class of disulfide constrained peptides containing a core motif FPWG was identified from a screen of phage displayed library using the HCV RNA-dependent RNA polymerase (NS5B) as a bait. Surface plasmon resonance studies showed that three highly purified synthetic constrained peptides bound to immobilized NS5B with estimated K(d) values ranging from 30 to 60 microM. In addition, these peptides inhibited the NS5B activity in vitro with IC(50) ranging from 6 to 48 microM, whereas in contrast they had no inhibitory effect on the enzymatic activities of calf thymus polymerase alpha, human polymerase beta, RSV polymerase, and HIV reverse transcriptase in vitro. Two peptides demonstrated conformation-dependent inhibition since their synthetic linear versions were not inhibitory in the NS5B assay. A constrained peptide with the minimum core motif FPWG retained selective inhibition of NS5B activity with an IC(50) of 50 microM. Alanine scan analyses of a representative constrained peptide, FPWGNTW, indicated that residues F1 and W7 were critical for the inhibitory effect of this peptide, although residues P2 and N5 had some measurable inhibitory effect as well. Further analyses of the mechanism of inhibition indicated that these peptides inhibited the formation of preelongation complexes required for the elongation reaction. However, once the preelongation complex was formed, its activity was refractory to peptide inhibition. Furthermore, the constrained peptide FPWGNTW inhibited de novo initiated RNA synthesis by NS5B from a poly(rC) template. These data indicate that the peptides confer selective inhibition of NS5B activity by binding to the enzyme and perturbing an early step preceding the processive elongation step of RNA synthesis.
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PMID:Identification of constrained peptides that bind to and preferentially inhibit the activity of the hepatitis C viral RNA-dependent RNA polymerase. 1295 Oct 30

DC-SIGN is a C-type lectin that binds to endogenous adhesion molecules ICAM-2 and ICAM-3 as well as the viral envelope glycoprotein human immunodeficiency virus, type 1, glycoprotein (gp) 120. We wished to determine whether DC-SIGN binds differently to its endogenous ligands ICAM-2 and ICAM-3 versus HIV-1 gp120. We found that recombinant soluble DC-SIGN bound to gp120-Fc more than 100- and 50-fold better than ICAM-2-Fc and ICAM-3-Fc, respectively. This relative difference was maintained using DC-SIGN expressed on three different CD4-negative cell lines. Although the cell surface affinity for gp120 varied by up to 4-fold on the cell lines examined, the affinity for gp120 was not a correlate of the ability of the cell line to transfer virus. Monosaccharides with equatorial 4-OH groups competed as well as D-mannose for gp120 binding to DC-SIGN, regardless of how the other hydroxyl groups were positioned. Disaccharide competitors and glycan chip analysis showed that DC-SIGN has a preference for oligosaccharides linked in an alpha-anomeric configuration. Alanine-scanning mutagenesis of DC-SIGN revealed that highly conserved residues that coordinate calcium (Asp-366) and/or are involved in both calcium and specific carbohydrate interactions (Glu-347, Asn-349, Glu-354, and Asp-355) significantly compromised binding to all three ligands. Mutating non-conserved residues (Asn-311, Arg-345, Val-351, Gly-352, Glu-353, Ser-360, Gly-361, and Asn-362) minimally affected binding except for the Asp-367 mutant, which enhanced gp120 binding but diminished ICAM-2 and ICAM-3 binding. Conversely, mutating the moderately conserved residue (Gly-346) abrogated gp120 binding but enhanced ICAM-2 and ICAM-3 binding. Thus, DC-SIGN appears to bind in a distinct but overlapping manner to gp120 when compared with ICAM-2 and ICAM-3.
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PMID:DC-SIGN binds to HIV-1 glycoprotein 120 in a distinct but overlapping fashion compared with ICAM-2 and ICAM-3. 1497 Feb 26

The E1 and E2 glycoproteins of hepatitis C virus form a noncovalently associated heterodimer that mediates viral entry. Glycoprotein E2 comprises a receptor-binding domain (residues 384-661) that is connected to the transmembrane domain (residues 716-746) via a highly conserved sequence containing a hydrophobic heptad repeat (residues 675-699). Alanine- and proline-scanning mutagenesis of the E2 heptad repeat revealed that Leu675, Ser678, Leu689, and Leu692 are important for E1E2 heterodimerization. Furthermore, Pro and Ala substitution of all but one heptad repeat residue (Ser678) blocked the entry of E1E2-HIV-1 pseudotypes into Huh7 cells, irrespective of an effect on heterodimerization. Two conserved prolines (Pro676 and Pro683), occupying consecutive b positions of the heptad, were not required for E1E2 heterodimerization; however, Pro683 was critical for viral entry. Thus, disruption of the predicted alpha-helical structure by proline at position 683 is important for E2 function. The inability of mutants to mediate viral entry was not explained by a loss of receptor binding function, because all mutants were able to interact with a recombinant form of the CD81 large extracellular loop. Chimeras formed between the E1 and E2 ectodomains and the transmembrane domains of flavivirus prM and E glycoproteins, respectively, were able to heterodimerize, although with lower efficiency in comparison with wild type E1E2. The heptad repeat of E2 therefore requires the native transmembrane domain for full heterodimerization and viral entry function. Our data indicate that the membraneproximal heptad repeat of E2 is functionally homologous to the stem of flavivirus E glycoproteins. We propose that E2 has mechanistic features in common with class II fusion proteins.
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PMID:Hepatitis C virus glycoprotein E2 contains a membrane-proximal heptad repeat sequence that is essential for E1E2 glycoprotein heterodimerization and viral entry. 1513 62

Human tRNA3(Lys) is used by HIV virus as a primer for the reverse transcription of its genome. The 18 nucleotides at the 3'-end of the tRNA3(Lys) are hybridized to a complementary sequence of the viral RNA called the primer-binding site. A screen against the human tRNA3(Lys) over a peptide library designed to target RNA has been performed. Of the 175 hexapeptides tested, three were found to bind to the d-stem of tRNA3(Lys). Alanine-scanning was used to define the determinants of the interaction between the peptides and tRNA3(Lys). They also bind to two other tested tRNAs, also at the level of the d-stem and loop, although the nucleotide sequence of the stem differs in one of them. These short peptides thus recognize specific structural features within the d-stem and loop of tRNAs. Associated with other pharmacophores, they could be useful to design optimized ligands targeting specific tRNAs such as retroviral replication primers.
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PMID:NMR-based identification of peptides that specifically recognize the d-arm of tRNA. 1616 95

The G-protein coupled receptor CCR5 functions pathologically as the primary co-receptor for macrophage tropic (R5) strains of HIV-1. The interactions responsible for co-receptor activity are unknown. Molecular-dynamics simulations of the extracellular and adjacent transmembrane domains of CCR5 were performed with explicit solvation utilizing a rhodopsin-based homology model. The functional unit of co-receptor binding was constructed via docking and molecular-dynamics simulation of CCR5 and the variable 3 loop of gp120, which is a dominant determinant of co-receptor utilization. The variable 3 loop was demonstrated to interact primarily with the amino terminus and the second extracellular loop of CCR5, providing novel structural information regarding the co-receptor-binding site. Alanine mutants that alter chemokine binding and co-receptor activity were examined. Molecular-dynamics simulations with and without the variable 3 loop of gp120 were able to rationalize the activities of these mutants successfully, providing support for the proposed model. Based on these results, the global complex of CCR5, gp120 including the V3 loop and CD4, was investigated. The utilization of computational analysis, in combination with molecular biological data, provides a powerful approach for understanding the use of CCR5 as a co-receptor by HIV-1.
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PMID:CCR5 interactions with the variable 3 loop of gp120. 1672 58

The X-ray crystallographic structure of HIV-1 capsid protein suggests that the dimer interface of the dimerization domain is mainly formed from a putative alpha-helix structure of 14 amino acids (Gag residues 311-324) and lies directly C-terminal to the capsid major homology region. We found that a deletion mutation in the alpha-helix drastically reduces virus particle production. Alanine-scanning mutagenetic analysis indicated that substitution mutations at residues Q311, V313, K314, W316, and M317 all impair virus particle production markedly. Membrane flotation assays suggested that some mutations in the dimer interface have slight effects on the efficient binding of Gag to membranes. Indirect immunofluorescence studies revealed that mutants defective in virus production exhibit a subcellular distribution pattern similar to that of wild-type. However, velocity sedimentation analysis showed that mutations significantly impairing virus particle production were also detrimental to Gag multimerization, suggesting that the impaired virus production may be due to a defect in Gag multimerization. These results support the proposal that residues in the capsid dimer interface play a crucial role in promoting Gag multimerization, possibly by facilitating stable Gag-Gag interactions.
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PMID:Mutations in the alpha-helix directly C-terminal to the major homology region of human immunodeficiency virus type 1 capsid protein disrupt Gag multimerization and markedly impair virus particle production. 1677 Jun 89


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