Cholesterol-Dependent Membrane Fusion Induced by the gp41 Membrane-Proximal External Region-Transmembrane Domain Connection Suggests a Mechanism for Broad HIV-1 Neutralization
Cholesterol-Dependent Membrane Fusion Induced by the gp41 Membrane-Proximal External Region-Transmembrane Domain Connection Suggests a Mechanism for Broad HIV-1 Neutralization
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DOI：
10.1128/jvi.02151-14
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发表时间：
2014-11-01
影响因子：
5.4
通讯作者：
Nieva, Jose L.
中科院分区：
文献类型：
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作者：
Apellaniz, Beatriz;Rujas, Edurne;Nieva, Jose L.
HIV-1 糖蛋白 41 促进病毒膜与靶细胞膜的融合。结构、生物化学和生物物理学研究表明，其膜近外部区域（MPER）可能与 HIV-1 膜相互作用，并在此过程中诱导其破坏和/或变形。然而，包膜的高胆固醇含量（约 40 至 50 mol%）赋予高刚性，从而阻碍脂质双层重组。在这里，基于囊泡稳定性测定、全原子分子动力学模拟和原子力显微镜观察的结果，我们提出连接MPER与跨膜结构域（TMD）N端残基的保守序列参与HIV-1融合。该连接将通过在富含胆固醇的刚性包膜中诱导磷脂突出和酰基链展开来发挥作用。支持这种机制的功能相关性的是，膜融合被广泛中和的 4E10 抗体抑制，但不被删除 CDR-H3 环的非中和变体抑制。我们得出的结论是，MPER-TMD 连接包含一种包膜破坏性 C 端融合肽，可以被广泛中和抗体靶向。重要性富含胆固醇的病毒包膜与细胞膜的融合标志着感染性 HIV-1 复制周期的开始。因此，Env 糖蛋白介导的融合功能构成了抑制剂和预防性疫苗的重要临床靶点。抗体 4E10 和 10E8 与位于 gp41 膜近外部区域 (MPER)-跨膜结构域 (TMD) 连接处的一个 Env 漏洞位点结合并阻断感染。这些抗体表现出广泛的病毒中和作用，这强调了 MPER-TMD 区域的保守性和功能性。在这项工作中，我们将生化测定与分子动力学模拟和显微镜观察相结合，以表征 MPER-TMD 连接前所未有的融合活性。这种活性依赖于胆固醇并被广泛中和的 4E10 抗体抑制，这一事实强调了其生理相关性。这一功能元件的发现增强了我们对 HIV-1 感染机制及其抗体阻断机制的理解。
The HIV-1 glycoprotein 41 promotes fusion of the viral membrane with that of the target cell. Structural, biochemical, and biophysical studies suggest that its membrane-proximal external region (MPER) may interact with the HIV-1 membrane and induce its disruption and/or deformation during the process. However, the high cholesterol content of the envelope (ca. 40 to 50 mol%) imparts high rigidity, thereby acting against lipid bilayer restructuring. Here, based on the outcome of vesicle stability assays, all-atom molecular dynamics simulations, and atomic force microscopy observations, we propose that the conserved sequence connecting the MPER with the N-terminal residues of the transmembrane domain (TMD) is involved in HIV-1 fusion. This junction would function by inducing phospholipid protrusion and acyl-chain splay in the cholesterol-enriched rigid envelope. Supporting the functional relevance of such a mechanism, membrane fusion was inhibited by the broadly neutralizing 4E10 antibody but not by a nonneutralizing variant with the CDR-H3 loop deleted. We conclude that the MPER-TMD junction embodies an envelope-disrupting C-terminal fusion peptide that can be targeted by broadly neutralizing antibodies.IMPORTANCEFusion of the cholesterol-enriched viral envelope with the cell membrane marks the beginning of the infectious HIV-1 replicative cycle. Consequently, the Env glycoprotein-mediated fusion function constitutes an important clinical target for inhibitors and preventive vaccines. Antibodies 4E10 and 10E8 bind to one Env vulnerability site located at the gp41 membrane-proximal external region (MPER)-transmembrane domain (TMD) junction and block infection. These antibodies display broad viral neutralization, which underscores the conservation and functionality of the MPER-TMD region. In this work, we combined biochemical assays with molecular dynamics simulations and microscopy observations to characterize the unprecedented fusogenic activity of the MPER-TMD junction. The fact that such activity is dependent on cholesterol and inhibited by the broadly neutralizing 4E10 antibody emphasizes its physiological relevance. Discovery of this functional element adds to our understanding of the mechanisms underlying HIV-1 infection and its blocking by antibodies.