The role of the N-terminal segment of CCR5 in HIV-1 Env-mediated membrane fusion and the mechanism of virus adaptation to CCR5 lacking this segment
<p>Abstract</p> <p>Background</p> <p>HIV-1 envelope glycoprotein (Env) induces membrane fusion as a result of sequential binding to CD4 and chemokine receptors (CCR5 or CXCR4). The critical determinants of CCR5 coreceptor function are the N-terminal domain (Nt) and the...
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| Format: | Article |
| Language: | English |
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BMC
2007-08-01
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| Series: | Retrovirology |
| Online Access: | http://www.retrovirology.com/content/4/1/55 |
| _version_ | 1818261677177569280 |
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| author | Kabat David Platt Emily J Melikyan Gregory B |
| author_facet | Kabat David Platt Emily J Melikyan Gregory B |
| author_sort | Kabat David |
| collection | DOAJ |
| description | <p>Abstract</p> <p>Background</p> <p>HIV-1 envelope glycoprotein (Env) induces membrane fusion as a result of sequential binding to CD4 and chemokine receptors (CCR5 or CXCR4). The critical determinants of CCR5 coreceptor function are the N-terminal domain (Nt) and the second extracellular loop. However, mutations in gp120 adapt HIV-1 to grow on cells expressing the N-terminally truncated CCR5(Δ18) (Platt <it>et al</it>., <it>J. Virol</it>. 2005, 79: 4357–68).</p> <p>Results</p> <p>We have functionally characterized the adapted Env (designated Env(NYP)) using a quantitative cell-cell fusion assay. The rate of fusion with target cells expressing wild-type CCR5 and the resistance to fusion inhibitors was virtually identical for wild-type Env and Env(NYP), implying that the coreceptor affinity had not increased as a result of adaptation. In contrast, Env(NYP)-induced fusion with cells expressing CCR5(Δ18) occurred at a slower rate and was extremely sensitive to the CCR5 binding inhibitor, Sch-C. Resistance to Sch-C drastically increased after pre-incubation of Env(NYP)- and CCR5(Δ18)-expressing cells at a temperature that was not permissive to fusion. This indicates that ternary Env(NYP)-CD4-CCR5(Δ18) complexes accumulate at sub-threshold temperature and that low-affinity interactions with the truncated coreceptor are sufficient for triggering conformational changes in the gp41 of Env(NYP) but not in wild-type Env. We also demonstrated that the ability of CCR5(Δ18) to support fusion and infection mediated by wild-type Env can be partially reconstituted in the presence of a synthetic sulfated peptide corresponding to the CCR5 Nt. Pre-incubation of wild-type Env- and CCR5(Δ18)-expressing cells with the sulfated peptide at sub-threshold temperature markedly increased the efficiency of fusion.</p> <p>Conclusion</p> <p>We propose that, upon binding the Nt region of CCR5, wild-type Env acquires the ability to productively engage the extracellular loop(s) of CCR5 – an event that triggers gp41 refolding and membrane merger. The adaptive mutations in Env(NYP) enable it to more readily release its hold on gp41, even when it interacts weakly with a severely damaged coreceptor in the absence of the sulfopeptide.</p> |
| first_indexed | 2024-12-12T18:51:02Z |
| format | Article |
| id | doaj.art-75f78406c31748f3ad7003c5b2f0dcf4 |
| institution | Directory Open Access Journal |
| issn | 1742-4690 |
| language | English |
| last_indexed | 2024-12-12T18:51:02Z |
| publishDate | 2007-08-01 |
| publisher | BMC |
| record_format | Article |
| series | Retrovirology |
| spelling | doaj.art-75f78406c31748f3ad7003c5b2f0dcf42022-12-22T00:15:22ZengBMCRetrovirology1742-46902007-08-01415510.1186/1742-4690-4-55The role of the N-terminal segment of CCR5 in HIV-1 Env-mediated membrane fusion and the mechanism of virus adaptation to CCR5 lacking this segmentKabat DavidPlatt Emily JMelikyan Gregory B<p>Abstract</p> <p>Background</p> <p>HIV-1 envelope glycoprotein (Env) induces membrane fusion as a result of sequential binding to CD4 and chemokine receptors (CCR5 or CXCR4). The critical determinants of CCR5 coreceptor function are the N-terminal domain (Nt) and the second extracellular loop. However, mutations in gp120 adapt HIV-1 to grow on cells expressing the N-terminally truncated CCR5(Δ18) (Platt <it>et al</it>., <it>J. Virol</it>. 2005, 79: 4357–68).</p> <p>Results</p> <p>We have functionally characterized the adapted Env (designated Env(NYP)) using a quantitative cell-cell fusion assay. The rate of fusion with target cells expressing wild-type CCR5 and the resistance to fusion inhibitors was virtually identical for wild-type Env and Env(NYP), implying that the coreceptor affinity had not increased as a result of adaptation. In contrast, Env(NYP)-induced fusion with cells expressing CCR5(Δ18) occurred at a slower rate and was extremely sensitive to the CCR5 binding inhibitor, Sch-C. Resistance to Sch-C drastically increased after pre-incubation of Env(NYP)- and CCR5(Δ18)-expressing cells at a temperature that was not permissive to fusion. This indicates that ternary Env(NYP)-CD4-CCR5(Δ18) complexes accumulate at sub-threshold temperature and that low-affinity interactions with the truncated coreceptor are sufficient for triggering conformational changes in the gp41 of Env(NYP) but not in wild-type Env. We also demonstrated that the ability of CCR5(Δ18) to support fusion and infection mediated by wild-type Env can be partially reconstituted in the presence of a synthetic sulfated peptide corresponding to the CCR5 Nt. Pre-incubation of wild-type Env- and CCR5(Δ18)-expressing cells with the sulfated peptide at sub-threshold temperature markedly increased the efficiency of fusion.</p> <p>Conclusion</p> <p>We propose that, upon binding the Nt region of CCR5, wild-type Env acquires the ability to productively engage the extracellular loop(s) of CCR5 – an event that triggers gp41 refolding and membrane merger. The adaptive mutations in Env(NYP) enable it to more readily release its hold on gp41, even when it interacts weakly with a severely damaged coreceptor in the absence of the sulfopeptide.</p>http://www.retrovirology.com/content/4/1/55 |
| spellingShingle | Kabat David Platt Emily J Melikyan Gregory B The role of the N-terminal segment of CCR5 in HIV-1 Env-mediated membrane fusion and the mechanism of virus adaptation to CCR5 lacking this segment Retrovirology |
| title | The role of the N-terminal segment of CCR5 in HIV-1 Env-mediated membrane fusion and the mechanism of virus adaptation to CCR5 lacking this segment |
| title_full | The role of the N-terminal segment of CCR5 in HIV-1 Env-mediated membrane fusion and the mechanism of virus adaptation to CCR5 lacking this segment |
| title_fullStr | The role of the N-terminal segment of CCR5 in HIV-1 Env-mediated membrane fusion and the mechanism of virus adaptation to CCR5 lacking this segment |
| title_full_unstemmed | The role of the N-terminal segment of CCR5 in HIV-1 Env-mediated membrane fusion and the mechanism of virus adaptation to CCR5 lacking this segment |
| title_short | The role of the N-terminal segment of CCR5 in HIV-1 Env-mediated membrane fusion and the mechanism of virus adaptation to CCR5 lacking this segment |
| title_sort | role of the n terminal segment of ccr5 in hiv 1 env mediated membrane fusion and the mechanism of virus adaptation to ccr5 lacking this segment |
| url | http://www.retrovirology.com/content/4/1/55 |
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