Department of Microbiology, Harbin Medical University, Harbin, China
Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, Maryland, USA.
J Virol. 2019 May 15;93(11). doi: 10.1128/JVI.00142-19. Print 2019 Jun 1.
Binding of the gp120 surface subunit of the envelope glycoprotein (Env) of HIV-1 to CD4 and chemokine receptors on target cells triggers refolding of the gp41 transmembrane subunit into a six-helix bundle (6HB) that promotes fusion between virus and host cell membranes. To elucidate details of Env entry and potential differences between viruses that use CXCR4 (X4) or CCR5 (R5) coreceptors, we generated viruses that are resistant to peptide fusion inhibitors corresponding to the first heptad repeat region (HR1) of gp41 that target fusion-intermediate conformations of Env. Previously we reported that an R5 virus selected two resistance pathways, each defined by an early gp41 resistance mutation in either HR1 or the second heptad repeat (HR2), to escape inhibition by an HR1 peptide, but preferentially selected the HR1 pathway to escape inhibition by a trimer-stabilized HR1 peptide. Here, we report that an X4 virus selected the same HR1 and HR2 resistance pathways as the R5 virus to escape inhibition by the HR1 peptide. However, in contrast to the R5 virus, the X4 virus selected a unique mutation in HR2 to escape inhibition by the trimer-stabilized peptide. Significantly, both of these X4 and R5 viruses acquired gp41 resistance mutations that improved the thermostability of the six-helix bundle, but they selected different gp120 adaptive mutations. These findings show that these X4 and R5 viruses use a similar resistance mechanism to escape from HR1 peptide inhibition but different gp120-gp41 interactions to regulate Env conformational changes. HIV-1 fuses with cells when the gp41 subunit of Env refolds into a 6HB after binding to cellular receptors. Peptides corresponding to HR1 or HR2 interrupt gp41 refolding and inhibit HIV infection. Previously, we found that a CCR5 coreceptor-tropic HIV-1 acquired a key HR1 or HR2 resistance mutation to escape HR1 peptide inhibitors but only the key HR1 mutation to escape a trimer-stabilized HR1 peptide inhibitor. Here, we report that a CXCR4 coreceptor-tropic HIV-1 selected the same key HR1 or HR2 mutations to escape inhibition by the HR1 peptide but different combinations of HR1 and HR2 mutations to escape the trimer-stabilized HR1 peptide. All gp41 mutations enhance 6HB stability to outcompete inhibitors, but gp120 adaptive mutations differed between these R5 and X4 viruses, providing new insights into gp120-gp41 functional interactions affecting Env refolding during HIV entry.
HIV-1 包膜糖蛋白 (Env) 的 gp120 表面亚基与靶细胞上的 CD4 和趋化因子受体结合，触发 gp41 跨膜亚基的重折叠成六螺旋束 (6HB)，促进病毒与宿主细胞膜融合。为了阐明 Env 进入的细节和使用 CXCR4 (X4) 或 CCR5 (R5) 核心受体的病毒之间的潜在差异，我们生成了对针对 gp41 第一七肽重复区 (HR1) 的融合抑制剂具有抗性的病毒，这些抑制剂针对 Env 的融合中间构象。此前，我们报道了一种 R5 病毒选择了两种抗性途径，每种途径都由 HR1 或第二个七肽重复 (HR2) 中的早期 gp41 抗性突变定义，以逃避 HR1 肽的抑制，但优先选择 HR1 途径以逃避三聚物稳定的 HR1 肽的抑制。在这里，我们报告说，X4 病毒选择了与 R5 病毒相同的 HR1 和 HR2 抗性途径，以逃避 HR1 肽的抑制。然而，与 R5 病毒不同的是，X4 病毒选择了 HR2 中的一个独特突变，以逃避三聚物稳定的肽的抑制。重要的是，这两种 X4 和 R5 病毒都获得了 gp41 抗性突变，提高了六螺旋束的热稳定性，但它们选择了不同的 gp120 适应性突变。这些发现表明，这些 X4 和 R5 病毒使用类似的抗性机制来逃避 HR1 肽抑制，但通过不同的 gp120-gp41 相互作用来调节 Env 构象变化。当 HIV-1 的 Env 亚单位 gp41与细胞受体结合后，gp41 亚单位折叠成 6HB 时与细胞融合。与 HR1 或 HR2 对应的肽中断 gp41 重折叠并抑制 HIV 感染。此前，我们发现，一种 CCR5 核心受体嗜性 HIV-1 获得了关键的 HR1 或 HR2 抗性突变，以逃避 HR1 肽抑制剂，但仅获得关键的 HR1 突变以逃避三聚物稳定的 HR1 肽抑制剂。在这里，我们报告说，一种 CXCR4 核心受体嗜性 HIV-1 选择了相同的关键 HR1 或 HR2 突变来逃避 HR1 肽的抑制，但逃避三聚物稳定的 HR1 肽的抑制则需要不同的 HR1 和 HR2 突变组合。所有 gp41 突变都增强了 6HB 的稳定性，以竞争抑制剂，但这些 R5 和 X4 病毒之间的 gp120 适应性突变不同，这为 gp120-gp41 功能相互作用提供了新的见解，这些相互作用影响 HIV 进入过程中 Env 的重折叠。
