Identification of Residues Controlling Restriction versus Enhancing Activities of IFITM Proteins on Entry of Human Coronaviruses
Identification of Residues Controlling Restriction versus Enhancing Activities of IFITM Proteins on Entry of Human Coronaviruses
复制标题
鉴定控制 IFITM 蛋白对人类冠状病毒进入的限制与增强活性的残基。
DOI：
10.1128/jvi.01535-17
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发表时间：
2018-03-01
影响因子：
5.4
通讯作者：
Guo, Ju-Tao
中科院分区：
文献类型：
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作者：
Zhao, Xuesen;Sehgal, Mohit;Guo, Ju-Tao
干扰素诱导的跨膜蛋白（IFITM）是抑制许多包膜RNA病毒感染进入的限制因子。然而，我们以前证明了人IFITM 2和IFITM 3是促进人冠状病毒（HCoV）OC 43进入的必需宿主因子。在继续努力破译IFITM差异调节HCoV进入的分子机制，我们研究了IFITM蛋白翻译后修饰，细胞内运输和寡聚化在调节5种HCoV进入中的重要结构基序的作用。我们发现IFITM 1或IFITM 3中的三个不同突变转换了宿主限制因子，以增强由严重急性呼吸综合征冠状病毒（SARS-CoV）和/或中东呼吸综合征冠状病毒（MERS-CoV）的刺突蛋白驱动的进入。首先，用丙氨酸或天冬氨酸替代IFITM 3酪氨酸20以模拟未磷酸化或磷酸化的IFITM 3降低了其抑制HCoV-NL 63和-229E进入的活性，但增强了SARS-CoV和MERS-CoV的进入。第二，IFITM 3酪氨酸99被丙氨酸或天冬氨酸取代降低了其抑制HCoV-NL 63和SARS-CoV进入的活性，但促进了MERS-CoV的进入。第三，IFITM 1羧基末端12个氨基酸残基的缺失增强了MERS-CoV和HCoV-OC 43的进入。这些发现表明IFITM蛋白的这些残基和结构基序是调节HCoV进入的关键决定因素，很可能是通过与病毒和/或重要性IFITM蛋白对HCoV进入的差异作用，即使当IFITM蛋白与HCoV结合时，HCoV也利用不同的进入途径和膜融合机制。使用相同的受体使得HCoV成为比较研究IFITM限制或促进病毒进入宿主细胞的分子机制的有价值的系统。鉴定三个不同的突变，将IFITM 1或IFITM 3从MERS-CoV或SARS-CoV刺突蛋白介导的进入的抑制剂转化为增强剂，揭示了决定IFITM蛋白生物活性的关键结构基序或残基。因此，这些发现为进一步鉴定与IFITM蛋白的那些结构基序相互作用以差异调节HCoV的感染进入的病毒和宿主因子铺平了道路。
Interferon-induced transmembrane proteins (IFITMs) are restriction factors that inhibit the infectious entry of many enveloped RNA viruses. However, we demonstrated previously that human IFITM2 and IFITM3 are essential host factors facilitating the entry of human coronavirus (HCoV) OC43. In a continuing effort to decipher the molecular mechanism underlying IFITM differential modulation of HCoV entry, we investigated the roles of structural motifs important for IFITM protein post-translational modifications, intracellular trafficking, and oligomerization in modulating the entry of five HCoVs. We found that three distinct mutations in IFITM1 or IFITM3 converted the host restriction factors to enhance entry driven by the spike proteins of severe acute respiratory syndrome coronavirus (SARS-CoV) and/or Middle East respiratory syndrome coronavirus (MERS-CoV). First, replacement of IFITM3 tyrosine 20 with either alanine or aspartic acid to mimic unphosphorylated or phosphorylated IFITM3 reduced its activity to inhibit the entry of HCoV-NL63 and -229E but enhanced the entry of SARS-CoV and MERS-CoV. Second, replacement of IFITM3 tyrosine 99 with either alanine or aspartic acid reduced its activity to inhibit the entry of HCoV-NL63 and SARS-CoV but promoted the entry of MERS-CoV. Third, deletion of the carboxyl-terminal 12 amino acid residues from IFITM1 enhanced the entry of MERS-CoV and HCoV-OC43. These findings suggest that these residues and structural motifs of IFITM proteins are key determinants for modulating the entry of HCoVs, most likely through interaction with viral and/or host cellular components at the site of viral entry to modulate the fusion of viral envelope and cellular membranes.IMPORTANCE The differential effects of IFITM proteins on the entry of HCoVs that utilize divergent entry pathways and membrane fusion mechanisms even when using the same receptor make the HCoVs a valuable system for comparative investigation of the molecular mechanisms underlying IFITM restriction or promotion of virus entry into host cells. Identification of three distinct mutations that converted IFITM1 or IFITM3 from inhibitors to enhancers of MERS-CoV or SARS-CoV spike protein-mediated entry revealed key structural motifs or residues determining the biological activities of IFITM proteins. These findings have thus paved the way for further identification of viral and host factors that interact with those structural motifs of IFITM proteins to differentially modulate the infectious entry of HCoVs.