The Polybasic Cleavage Site in SARS-CoV-2 Spike Modulates Viral Sensitivity to Type I Interferon and IFITM2.
The Polybasic Cleavage Site in SARS-CoV-2 Spike Modulates Viral Sensitivity to Type I Interferon and IFITM2.
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DOI：
10.1128/jvi.02422-20
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发表时间：
2021-04-12
影响因子：
5.4
通讯作者：
Neil SJD
中科院分区：
文献类型：
--
作者：
Winstone H;Lista MJ;Reid AC;Bouton C;Pickering S;Galao RP;Kerridge C;Doores KJ;Swanson CM;Neil SJD
S蛋白中的Furin裂解位点是SARS-CoV-2的一个显著特征，被认为是与SARS-CoV-1相比具有更高的个体间传播率的决定因素。对此的一种解释是，它允许在细胞表面或细胞表面附近更有效地激活融合，而不需要在靶细胞的内吞体内进行处理。严重急性呼吸综合征相关冠状病毒1型和2型(SARS-CoV-1和-2)的细胞进入需要对病毒刺突糖蛋白进行顺序的蛋白酶处理。与SARS-CoV-1相比，SARS-CoV-2在S1/S2交界处的棘突中存在一个多碱基切割位点，这可能是SARS-CoV-2相比SARS-CoV-1传播性增加的一个因素，因为它促进了产生细胞中的呋喃类蛋白水解酶而不是靶细胞中的内体组织蛋白对尖峰前体的成熟。我们研究了SARS-CoV-2进入途径中多碱基裂解位点的相关性，以及这对干扰素(IFN)敏感性的影响，更具体地说，是抑制不同包膜病毒进入的干扰素诱导跨膜蛋白(IFITM)家族。我们发现SARS-CoV-2主要受IFITM2的限制，而不是IFITM3，并且这种限制的程度取决于病毒进入的途径。重要的是，去除Spike蛋白中的切割位点使SARS-CoV-2进入晚期内体高度依赖pH和组织蛋白酶，与SARS-CoV-1 Spike一样，它对IFITM2限制更敏感。此外，我们发现，通过靶向缺失IFITM2的表达，I型而不是II型IFN对SARS-CoV-2复制的有效抑制被减轻。我们认为，多碱基切割位点允许SARS-CoV-2以一种不依赖于pH的方式介导病毒进入，部分原因是为了缓解IFITM介导的限制，促进复制和传播。这表明，靶向呋喃介导的SARS-CoV-2尖峰切割的治疗策略可能通过I型IFN的活性来减少病毒复制。重要的是，与SARS-CoV-1相比，S蛋白中的Furin裂解位点是SARS-CoV-2的一个显著特征，并被认为是个体之间更高传播率的决定因素。对此的一种解释是，它允许在细胞表面或细胞表面附近更有效地激活融合，而不需要在靶细胞的内吞体内进行处理。在这里，我们表明SARS-CoV-2被抗病毒膜蛋白IFITM2抑制，并且这种敏感性因Furin裂解位点的缺失而加剧，这限制了病毒进入低pH值的隔间。此外，我们发现IFITM2是I型干扰素抗SARS-CoV-2复制的重要效应者。我们认为，Furin裂解位点的作用之一是降低SARS-CoV-2对天然免疫限制的敏感性，因此，它可能是新冠肺炎治疗的潜在治疗靶点。
The furin cleavage site in the spike protein is a distinguishing feature of SARS-CoV-2 and has been proposed to be a determinant for the higher transmissibility between individuals, compared to SARS-CoV-1. One explanation for this is that it permits more efficient activation of fusion at or near the cell surface rather than requiring processing in the endosome of the target cell. The cellular entry of severe acute respiratory syndrome-associated coronaviruses types 1 and 2 (SARS-CoV-1 and -2) requires sequential protease processing of the viral spike glycoprotein. The presence of a polybasic cleavage site in SARS-CoV-2 spike at the S1/S2 boundary has been suggested to be a factor in the increased transmissibility of SARS-CoV-2 compared to SARS-CoV-1 by facilitating maturation of the spike precursor by furin-like proteases in the producer cells rather than endosomal cathepsins in the target. We investigate the relevance of the polybasic cleavage site in the route of entry of SARS-CoV-2 and the consequences this has for sensitivity to interferons (IFNs) and, more specifically, the IFN-induced transmembrane (IFITM) protein family that inhibit entry of diverse enveloped viruses. We found that SARS-CoV-2 is restricted predominantly by IFITM2, rather than IFITM3, and the degree of this restriction is governed by route of viral entry. Importantly, removal of the cleavage site in the spike protein renders SARS-CoV-2 entry highly pH and cathepsin dependent in late endosomes, where, like SARS-CoV-1 spike, it is more sensitive to IFITM2 restriction. Furthermore, we found that potent inhibition of SARS-CoV-2 replication by type I but not type II IFNs is alleviated by targeted depletion of IFITM2 expression. We propose that the polybasic cleavage site allows SARS-CoV-2 to mediate viral entry in a pH-independent manner, in part to mitigate against IFITM-mediated restriction and promote replication and transmission. This suggests that therapeutic strategies that target furin-mediated cleavage of SARS-CoV-2 spike may reduce viral replication through the activity of type I IFNs. IMPORTANCE The furin cleavage site in the spike protein is a distinguishing feature of SARS-CoV-2 and has been proposed to be a determinant for the higher transmissibility between individuals, compared to SARS-CoV-1. One explanation for this is that it permits more efficient activation of fusion at or near the cell surface rather than requiring processing in the endosome of the target cell. Here, we show that SARS-CoV-2 is inhibited by antiviral membrane protein IFITM2 and that the sensitivity is exacerbated by deletion of the furin cleavage site, which restricts viral entry to low pH compartments. Furthermore, we find that IFITM2 is a significant effector of the antiviral activity of type I interferons against SARS-CoV-2 replication. We suggest that one role of the furin cleavage site is to reduce SARS-CoV-2 sensitivity to innate immune restriction, and thus, it may represent a potential therapeutic target for COVID-19 treatment development.