Molecular Virology Laboratory, Rajiv Gandhi Centre for Biotechnology (RGCB), Thiruvananthapuram, India.
Research Centre, University of Kerala, Thiruvananthapuram, India.
Microbiol Spectr. 2023 Aug 17;11(4):e0537122. doi: 10.1128/spectrum.05371-22. Epub 2023 Jul 6.
Chikungunya virus (CHIKV) hijacks host cell machinery to support its replication. Nucleophosmin 1 (NPM1/B23), a nucleolar phosphoprotein, is one of the host proteins known to restrict CHIKV infection; however, the mechanistic details of the antiviral role of NPM1 are not elucidated. It was seen in our experiments that the level of NPM1 expression affected the expression levels of interferon-stimulated genes (ISGs) that play antiviral roles in CHIKV infection, such as , , , and , indicating that one of the antiviral mechanisms could be through modulation of interferon-mediated pathways. Our experiments also identified that for CHIKV restriction, NPM1 must move from the nucleus to the cytoplasm. A deletion of the nuclear export signal (NES), which confines NPM1 within the nucleus, abolishes its anti-CHIKV action. We observed that NPM1 binds CHIKV nonstructural protein 3 (nsP3) strongly via its macrodomain, thereby exerting a direct interaction with viral proteins to limit infection. Based on site-directed mutagenesis and coimmunoprecipitation studies, it was also observed that amino acid residues N24 and Y114 of the CHIKV nsP3 macrodomain, known to be involved in virus virulence, bind ADP-ribosylated NPM1 to inhibit infection. Overall, the results show a key role of NPM1 in CHIKV restriction and indicate it as a promising host target for developing antiviral strategies against CHIKV. Chikungunya, a recently reemerged mosquito-borne infection caused by a positive-sense, single-stranded RNA virus, has caused explosive epidemics in tropical regions. Unlike the classical symptoms of acute fever and debilitating arthralgia, incidences of neurological complications and mortality were reported. Currently there are no antivirals or commercial vaccines available against chikungunya. Like all viruses, CHIKV uses host cellular machinery for establishment of infection and successful replication. To counter this, the host cell activates several restriction factors and innate immune response mediators. Understanding these host-virus interactions helps to develop host-targeted antivirals against the disease. Here, we report the antiviral role of the multifunctional host protein NPM1 against CHIKV. The significant inhibitory effect of this protein against CHIKV involves its increased expression and movement from its natural location within the nucleus to the cytoplasm. There, it interacts with functional domains of key viral proteins. Our results support ongoing efforts toward development of host-directed antivirals against CHIKV and other alphaviruses.
基孔肯雅病毒（CHIKV）劫持宿主细胞机制来支持其复制。核仁磷酸蛋白 1（NPM1/B23）是一种已知限制 CHIKV 感染的宿主蛋白之一；然而，NPM1 的抗病毒作用的机制细节尚不清楚。在我们的实验中观察到，NPM1 的表达水平影响干扰素刺激基因（ISGs）的表达水平，这些基因在 CHIKV 感染中发挥抗病毒作用，如 、 、 、和 ，这表明一种抗病毒机制可能是通过调节干扰素介导的途径。我们的实验还确定，为了限制 CHIKV，NPM1 必须从细胞核转移到细胞质。核输出信号（NES）的缺失，将 NPM1 限制在核内，从而消除其抗 CHIKV 作用。我们观察到 NPM1 通过其宏结构强烈结合 CHIKV 非结构蛋白 3（nsP3），从而与病毒蛋白直接相互作用以限制感染。基于定点诱变和共免疫沉淀研究，还观察到 CHIKV nsP3 宏结构中参与病毒毒力的氨基酸残基 N24 和 Y114 与 ADP-核糖基化的 NPM1 结合，抑制感染。总的来说，这些结果表明 NPM1 在 CHIKV 限制中起关键作用，并表明它是开发针对 CHIKV 的抗病毒策略的有前途的宿主靶标。
基孔肯雅热是一种由正链、单链 RNA 病毒引起的新近重新出现的蚊媒感染，在热带地区引发了爆炸性的流行。与急性发热和衰弱性关节炎的经典症状不同，报告了神经系统并发症和死亡率的发生率。目前尚无针对基孔肯雅热的抗病毒药物或商业疫苗。与所有病毒一样，CHIKV 利用宿主细胞机制来建立感染并成功复制。为了对抗这种情况，宿主细胞激活了几种限制因子和先天免疫反应介质。了解这些宿主-病毒相互作用有助于开发针对该疾病的宿主靶向抗病毒药物。在这里，我们报告了多功能宿主蛋白 NPM1 对 CHIKV 的抗病毒作用。这种蛋白质对 CHIKV 的显著抑制作用涉及它的增加表达和从其在细胞核内的天然位置移动到细胞质。在那里，它与关键病毒蛋白的功能域相互作用。我们的结果支持针对 CHIKV 和其他甲病毒开发宿主定向抗病毒药物的努力。
