SARS-CoV-2 Fusion Domain Provides Clues toward the Molecular Mechanism for Membrane Fusion
SARS-CoV-2 Fusion Domain Provides Clues toward the Molecular Mechanism for Membrane Fusion
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SARS-CoV-2融合域为膜融合的分子机制提供线索
DOI：
10.1021/acs.biochem.3c00501
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发表时间：
2023
期刊：
影响因子：
2.9
通讯作者：
Lee, Jinwoo
中科院分区：
文献类型：
--
作者：
Birtles, Daniel;Lee, Jinwoo
病毒生命周期是一系列高度优化的复杂过程，使病毒能够利用宿主细胞自身的分子机制来产生额外的病毒颗粒。生命周期的每一步都是病毒不可或缺的一部分，因此，为了了解如何更好地保护自己免受病毒感染，我们必须首先了解这些病毒如何在分子水平上有效生存。进入靶细胞是病毒生命周期的关键组成部分，在冠状病毒家族中，刺突糖蛋白促进了这一过程（图 1）。该过程可分为受体结合和膜融合，分别由刺突糖蛋白的两个功能亚基 S1 和 S2 执行。 S1 中的受体结合域 (RBD) 与靶细胞受体血管紧张素转换酶 2 (ACE2) 相互作用。一旦结合，S2' 裂解位点就会发生裂解事件，从而在裂解的 S2 亚基 (S2') 的 N 末端释放融合结构域 (FD)。然后，FD 可以自由地与靶细胞膜相互作用，从而启动 S2' 中的一系列结构重排，最终导致膜融合并将病毒基因组递送到宿主细胞中。 2002 年 SARS-CoV-1 首次爆发后，围绕冠状病毒家族的研究显着增加，以识别 FD。几个膜相互作用区域很快被识别、表征和提出，大多数证据表明 S2' 的 N 末端是最有可能的候选区域。在接下来的 10 年里，Lai 和同事发现这种 FD 由两个功能单元组成，它们可以与脂质膜相互作用并扰乱脂质膜，无论是独立合成还是协同作用，都可以产生更大的效果。 1 虽然这项研究是在 SARS-CoV-1 中进行的，但强烈的序列保守性表明这适用于冠状病毒家族的所有成员。这导致冠状病毒 FD 被标记为二分系统，形成扩展的融合平台，因为它包含两个可以引发融合的区域。对 SARS-CoV-2 FD 的进一步研究导致在该域本身内发现了两个结构独立的区域。 S2' 的 N 末端存在融合肽（FP；S816-G838），其包含螺旋-转角-螺旋基序中 FD 的前 23 个氨基酸。这种结构基序允许 FP 埋入膜内，其中转角是插入的最深点。紧接着 FP 的是融合环（FL；D839-F855），由保守的二硫键形成。 FL 不包含可辨别的二级结构，仅与膜表面相互作用。我们相信，命名法 FP 和 FL 最清楚地描述了这两个区域，因为它强化了这样一个事实，即它们是单个结构域内的两个不同结构，保留了与先前描述的和在其他病毒中发现的良好融合区域的关键相似性。大约在同一时间，脂质双层中 FD 的结构发表并验证了这些结构发现。 2 随后开展了进一步的工作，以了解 FD 如何通过 FP 和 FL 的单独扰动启动融合的分子细节。当 FP 内的关键疏水基序“LLF”通过诱变被破坏以及当 FL 内的二硫键被切断时，FD 的融合能力显着下降。 3 这些结果表明了一种复杂的协同机制，涉及 FP 和 FL 的能力，其中任何一个区域都无法在其他区域完全完整的情况下有效地启动融合。完整的原子分辨率结构......
The viral lifecycle is a highly optimized series of intricate processes that allows a virus to take advantage of a host cell’s own molecular machinery to produce additional viral particles. Every step of the lifecycle is integral to the virus, and thus, in order to understand how to better protect ourselves against viral infections, we must first understand how these viruses can effectively survive on a molecular level. Entry into a target cell is a critical component of the viral lifecycle, which in the coronavirus family is facilitated by the spike glycoprotein (Figure 1). This process can be split into receptor binding and membrane fusion, which are carried out by the two functional subunits of the spike glycoprotein, S1 and S2, respectively. The receptor binding domain (RBD) found in S1 interacts with the target cell receptor, angiotensinconverting enzyme 2 (ACE2). Once bound, a cleavage event then occurs at the S2′ cleavage site, which releases the fusion domain (FD) at the N-terminus of the cleaved S2 subunit (S2′). The FD is then free to interact with the target cell membrane, which initiates a cascade of structural rearrangements in S2′ that ultimately results in membrane fusion and delivery of the viral genome into the host cell. Following the initial outbreak of SARS-CoV-1 in 2002, a significant increase in research surrounding the coronavirus family took place to identify the FD. Several membraneinteracting regions were quickly identified, characterized, and proposed, with most evidence pointing toward the N-terminus of S2′ as the most likely candidate. Over the next 10 years, Lai and co-workers discovered that this FD consisted of two functional units that could interact with and perturb lipid membranes both when independently synthesized and in synergy to even greater effect. 1 While this research was carried out in SARS-CoV-1, strong sequence conservation suggested that this was applicable to all members of the coronavirus family. This led to the coronavirus FD being labeled as a bipartite system that forms an extended fusion platform because of it containing two regions that can elicit fusion. Further investigation into the SARS-CoV-2 FD led to the discovery of two structurally independent regions within the domain itself. At the N-terminus of S2′ exists the fusion peptide (FP; S816-G838), which comprises the first 23 amino acids of the FD in a helix-turn-helix motif. This structural motif allows the FP to bury within the membrane, with the turn being the deepest point of insertion. Immediately following the FP is the fusion loop (FL; D839-F855), formed by a conserved disulfide bond. The FL contains no discernible secondary structure and only superficially interacts with the membrane. It is our belief that the nomenclature FP and FL most clearly describes the two regions because it reinforces the fact that they are two distinct structures within a single domain that retain key similarities to previously described and wellestablished fusogenic regions found in other viruses. Around the same time, the structure of the FD in a lipid bilayer was published and verified these structural findings. 2 Further work was then undertaken to understand the molecular details of how the FD initiates fusion, through the individual perturbation of the FP and FL. A significant decrease in fusogenic ability was witnessed for the FD when a key hydrophobic motif within the FP,“LLF,” was disrupted via mutagenesis and also when the disulfide bond within the FL was severed. 3 Those results indicated a complex, synergistic mechanism that involves both the FP and FL to such a capacity where neither region can efficiently initiate fusion without the other fully intact.Atomic resolution structures of the full …