Wrensch Florian, Winkler Michael, Pöhlmann Stefan
Infection Biology Unit, German Primate Center, 37077 Göttingen, Germany.
Viruses. 2014 Sep 26;6(9):3683-98. doi: 10.3390/v6093683.
The interferon-inducible transmembrane (IFITM) proteins 1, 2 and 3 inhibit the host cell entry of several enveloped viruses, potentially by promoting the accumulation of cholesterol in endosomal compartments. IFITM3 is essential for control of influenza virus infection in mice and humans. In contrast, the role of IFITM proteins in coronavirus infection is less well defined. Employing a retroviral vector system for analysis of coronavirus entry, we investigated the susceptibility of human-adapted and emerging coronaviruses to inhibition by IFITM proteins. We found that entry of the recently emerged Middle East respiratory syndrome coronavirus (MERS-CoV) is sensitive to inhibition by IFITM proteins. In 293T cells, IFITM-mediated inhibition of cellular entry of the emerging MERS- and SARS-CoV was less efficient than blockade of entry of the globally circulating human coronaviruses 229E and NL63. Similar differences were not observed in A549 cells, suggesting that cellular context and/or IFITM expression levels can impact inhibition efficiency. The differential IFITM-sensitivity of coronaviruses observed in 293T cells afforded the opportunity to investigate whether efficiency of entry inhibition by IFITMs and endosomal cholesterol accumulation correlate. No such correlation was observed. Furthermore, entry mediated by the influenza virus hemagglutinin was robustly inhibited by IFITM3 but was insensitive to accumulation of endosomal cholesterol, indicating that modulation of cholesterol synthesis/transport did not account for the antiviral activity of IFITM3. Collectively, these results show that the emerging MERS-CoV is a target of the antiviral activity of IFITM proteins and demonstrate that mechanisms other than accumulation of endosomal cholesterol can contribute to viral entry inhibition by IFITMs.
干扰素诱导跨膜（IFITM）蛋白1、2和3可抑制多种包膜病毒进入宿主细胞，这可能是通过促进胆固醇在内体区室中的积累来实现的。IFITM3对于小鼠和人类控制流感病毒感染至关重要。相比之下，IFITM蛋白在冠状病毒感染中的作用尚不太明确。我们利用逆转录病毒载体系统分析冠状病毒的进入过程，研究了适应人类的冠状病毒和新出现的冠状病毒对IFITM蛋白抑制作用的敏感性。我们发现，最近出现的中东呼吸综合征冠状病毒（MERS-CoV）的进入对IFITM蛋白的抑制敏感。在293T细胞中，IFITM介导的对新出现的MERS-CoV和SARS-CoV细胞进入的抑制作用不如对全球流行的人类冠状病毒229E和NL63进入的阻断有效。在A549细胞中未观察到类似差异，这表明细胞背景和/或IFITM表达水平会影响抑制效率。在293T细胞中观察到的冠状病毒对IFITM的不同敏感性，为研究IFITM介导的进入抑制效率与内体胆固醇积累是否相关提供了机会。未观察到这种相关性。此外，流感病毒血凝素介导的进入受到IFITM3的强烈抑制，但对内体胆固醇积累不敏感，这表明胆固醇合成/运输的调节并不能解释IFITM3的抗病毒活性。总的来说，这些结果表明，新出现的MERS-CoV是IFITM蛋白抗病毒活性的靶点，并证明除内体胆固醇积累外的其他机制也可导致IFITM对病毒进入的抑制作用。
