Hantavirus inhibits apoptosis by preventing mitochondrial membrane potential loss through up-regulation of the pro-survival factor BCL-2
Hantavirus inhibits apoptosis by preventing mitochondrial membrane potential loss through up-regulation of the pro-survival factor BCL-2
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DOI：
10.1371/journal.ppat.1008297
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发表时间：
2020-02-01
期刊：
影响因子：
6.7
通讯作者：
Klingstrom, Jonas
中科院分区：
文献类型：
--
作者：
Sola-Riera, Carles;Garcia, Marina;Klingstrom, Jonas
汉坦病毒是属于布尼亚病毒目的人畜共患核糖核酸病毒，可引起人类两种严重的急性疾病，即肾综合征出血热(HFRS)和汉坦病毒肺综合征(HPS)。感染汉坦病毒的患者表现出强烈的细胞毒性淋巴细胞反应和高度炎症；然而，感染的细胞大部分保持完好。汉坦病毒最近被证明可以抑制感染细胞的凋亡。通过抑制颗粒酶B和TRAIL介导的细胞凋亡，汉坦病毒特异性和有效地抑制细胞毒性淋巴细胞介导的对感染细胞的杀伤。汉坦病毒还强烈抑制由内在触发的细胞凋亡，即通过与细胞毒性淋巴细胞不同的细胞内激活途径启动的。然而，对后一种机制的见解目前在很大程度上是未知的。在这里，我们剖析了以引起HFRS的汉滩病毒和引起HPS的安第斯病毒为代表的汉坦病毒感染导致对星状孢子素诱导的细胞凋亡产生抵抗的机制。与未感染的星状孢子素暴露的细胞相比，感染的细胞中caspase-8和caspase-9的活性较低，因此caspase-3的活性也较低。虽然暴露于星形孢菌素的未感染细胞显示大量促细胞色素C释放到胞浆中，但在感染细胞中没有观察到这一点。此外，汉坦病毒还阻止了Bax和线粒体外膜通透性(MOMP)的激活。同时，在汉坦病毒感染的细胞中观察到促生存因子bcl2的水平显著增加。重要的是，抑制剂ABT-737对bcl2的直接抑制以及siRNA对bcl2的沉默导致了暴露于星状孢子素的汉坦病毒感染细胞的凋亡。总之，我们在这里提供了一个初步的机制，汉坦病毒通过诱导促进生存因子bcl2的表达增加，从而阻止MOMPs和随后的caspase的激活，在线粒体水平上保护受感染的细胞免受内源性凋亡的影响。汉坦病毒用来确保被感染细胞存活的各种机制可能导致在自然宿主中的持续感染，并可能在人类HFRS和HPS的免疫发病机制中发挥作用。作者概述汉坦病毒导致两种严重的、通常是致命的人类疾病：肾综合征出血热(HFRS)和汉坦病毒肺综合征(HPS；又称汉坦病毒心肺综合征(HCPS))。人类感染汉坦病毒的两个特征是强大的免疫细胞激活和高度炎症。尽管有这些强大的免疫反应，汉坦病毒感染的细胞不会死于患者的细胞死亡。最近的研究表明，汉坦病毒通过抑制细胞毒颗粒依赖的细胞凋亡诱导和TRAIL介导的细胞凋亡，以及抑制内源性细胞凋亡，从而阻碍细胞毒性淋巴细胞介导的杀伤。然而，汉坦病毒诱导抑制内源性细胞凋亡的机制尚未被描述。在这里，我们表明，汉坦病毒感染导致抗凋亡蛋白bcl2的产生增加，阻碍线粒体的通透性，从而阻止下游信号传递和caspase的激活。用bcl2抑制剂处理受感染的细胞，以及用siRNA沉默bcl2，都逆转了抗凋亡的作用。综上所述，这项研究揭示了汉坦病毒与感染细胞之间相互作用的新见解，并展示了汉坦病毒通过阻碍线粒体通透性来抑制细胞凋亡的新机制。
Hantaviruses, zoonotic RNA viruses belonging to the order Bunyavirales, cause two severe acute diseases in humans, hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS). Hantavirus-infected patients show strong cytotoxic lymphocyte responses and hyperinflammation; however, infected cells remain mostly intact. Hantaviruses were recently shown to inhibit apoptosis in infected cells. By inhibiting granzyme B- and TRAIL-mediated apoptosis, hantaviruses specifically and efficiently inhibit cytotoxic lymphocyte-mediated killing of infected cells. Hantaviruses also strongly inhibit apoptosis triggered intrinsically; i.e., initiated through intracellular activation pathways different from those used by cytotoxic lymphocytes. However, insights into the latter mechanisms are currently largely unknown. Here, we dissected the mechanism behind how hantavirus infection, represented by the HFRS-causing Hantaan virus and the HPS-causing Andes virus, results in resistance to staurosporine-induced apoptosis. Less active caspase-8 and caspase-9, and consequently less active caspase-3, was observed in infected compared to uninfected staurosporine-exposed cells. While staurosporine-exposed uninfected cells showed massive release of pro-apoptotic cytochrome C into the cytosol, this was not observed in infected cells. Further, hantaviruses prevented activation of BAX and mitochondrial outer membrane permeabilization (MOMP). In parallel, a significant increase in levels of the pro-survival factor BCL-2 was observed in hantavirus-infected cells. Importantly, direct inhibition of BCL-2 by the inhibitor ABT-737, as well as silencing of BCL-2 by siRNA, resulted in apoptosis in staurosporine-exposed hantavirus-infected cells. Overall, we here provide a tentative mechanism by which hantaviruses protect infected cells from intrinsic apoptosis at the mitochondrial level by inducing an increased expression of the pro-survival factor BCL-2, thereby preventing MOMPs and subsequent activation of caspases. The variety of mechanisms used by hantaviruses to ensure survival of infected cells likely contribute to the persistent infection in natural hosts and may play a role in immunopathogenesis of HFRS and HPS in humans.Author summaryHantaviruses cause two severe, often fatal, diseases in humans: hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS; also called hantavirus cardiopulmonary syndrome (HCPS)). Two hallmarks of human hantavirus infection are robust immune cell activation and hyperinflammation. Despite these strong immune responses, hantavirus-infected cells do not succumb to cell death in patients. Recent studies have shown that hantaviruses hamper cytotoxic lymphocyte-mediated killing, by inhibiting cytotoxic granule-dependent induction of apoptosis and TRAIL-mediated apoptosis, as well as inhibiting intrinsic apoptosis. However, mechanisms behind hantavirus induced inhibition of intrinsic apoptosis have not been described. Here, we show that hantavirus infection leads to increased production of the anti-apoptotic protein BCL-2, hampering the permeabilization of mitochondria and thereby blocking downstream signaling and activation of caspases. Treatment of infected cells with a BCL-2 inhibitor, as well as silencing of BCL-2 with siRNA, both reverted the anti-apoptotic effect. Taken together, this study reveals new insights into the interactions between hantaviruses and infected cells and demonstrates novel mechanisms by which hantaviruses inhibit apoptosis by hampering the permeabilization of mitochondria.