Division of Molecular Neurobiology, The Institute for Enzyme Research (KOSOKEN), Tokushima University, Tokushima, Japan.
Core Research Facility, Center for Infectious Disease Education and Research (CiDER), Osaka University, Osaka, Japan.
J Virol. 2024 Sep 17;98(9):e0126224. doi: 10.1128/jvi.01262-24. Epub 2024 Aug 28.
Production of the amyloidogenic prion protein, PrP, which forms infectious protein aggregates, or prions, is a key pathogenic event in prion diseases. Functional prion-like protein aggregations, such as the mitochondrial adaptor protein MAVS and the inflammasome component protein ASC, have been identified to play a protective role in viral infections in mammalian cells. In this study, to investigate if PrP could play a functional role against external stimuli, we infected prion-infected cells with a neurotropic influenza A virus strain, IAV/WSN. We found that prion-infected cells were highly resistant to IAV/WSN infection. In these cells, NF-κB nuclear translocation was disturbed; therefore, mitochondrial superoxide dismutase (mtSOD) expression was suppressed, and mitochondrial reactive oxygen species (mtROS) was increased. The elevated mtROS subsequently activated NLRP3 inflammasomes, leading to the suppression of IAV/WSN-induced necroptosis. We also found that prion-infected cells accumulated a portion of PrP molecules in the cytosol, and that the N-terminal potential nuclear translocation signal of PrP impeded NF-κB nuclear translocation. These results suggest that PrP might play a functional role in protection against viral infections by stimulating the NLRP3 inflammasome-dependent antivirus mechanism through the cytosolic PrP-mediated disturbance of NF-κB nuclear translocation, which leads to suppression of mtSOD expression and consequently upregulation of the NLRP3 inflammasome activator mtROS.
Cytosolic PrP has been detected in prion-infected cells and suggested to be involved in the neurotoxicity of prions. Here, we also detected cytosolic PrP in prion-infected cells. We further found that the nuclear translocation of NF-κB was disturbed in prion-infected cells and that the N-terminal potential nuclear translocation signal of PrP expressed in the cytosol disturbed the nuclear translocation of NF-κB. Thus, the N-terminal nuclear translocation signal of cytosolic PrP might play a role in prion neurotoxicity. Prion-like protein aggregates in other protein misfolding disorders, including Alzheimer's disease were reported to play a protective role against various environmental stimuli. We here showed that prion-infected cells were partially resistant to IAV/WSN infection due to the cytosolic PrP-mediated disturbance of the nuclear translocation of NF-κB, which consequently activated NLRP3 inflammasomes after IAV/WSN infection. It is thus possible that prions could also play a protective role in viral infections.
淀粉样蛋白形成朊病毒，PrP 的产生是朊病毒病的关键致病事件，PrP 形成感染性蛋白聚集物，或朊病毒。功能类似朊病毒的蛋白聚集物，如线粒体衔接蛋白 MAVS 和炎性小体成分蛋白 ASC，已被鉴定在哺乳动物细胞的病毒感染中发挥保护作用。在这项研究中，为了研究 PrP 是否可以针对外部刺激发挥功能作用，我们用神经嗜性流感 A 病毒株 IAV/WSN 感染朊病毒感染的细胞。我们发现朊病毒感染的细胞对 IAV/WSN 感染具有高度抗性。在这些细胞中，NF-κB 核易位受到干扰；因此，线粒体超氧化物歧化酶（mtSOD）的表达受到抑制，线粒体活性氧物质（mtROS）增加。升高的 mtROS 随后激活 NLRP3 炎性小体，导致抑制 IAV/WSN 诱导的坏死性凋亡。我们还发现朊病毒感染的细胞在细胞质中积累了一部分 PrP 分子，并且 PrP 的 N 端潜在核易位信号阻碍了 NF-κB 的核易位。这些结果表明，PrP 可能通过刺激依赖 NLRP3 炎性小体的抗病毒机制发挥功能作用，该机制通过细胞质 PrP 介导的 NF-κB 核易位干扰来实现，从而抑制 mtSOD 的表达并随后上调 NLRP3 炎性小体激活剂 mtROS。
已在朊病毒感染的细胞中检测到细胞质 PrP，并提示其参与朊病毒的神经毒性。在这里，我们还在朊病毒感染的细胞中检测到细胞质 PrP。我们进一步发现，NF-κB 的核易位在朊病毒感染的细胞中受到干扰，并且在细胞质中表达的 PrP 的 N 端潜在核易位信号干扰了 NF-κB 的核易位。因此，细胞质 PrP 的 N 端核易位信号可能在朊病毒神经毒性中发挥作用。包括阿尔茨海默病在内的其他蛋白质错误折叠疾病中的朊病毒样蛋白聚集物被报道在各种环境刺激下发挥保护作用。我们在这里表明，由于 IAV/WSN 感染后细胞质 PrP 介导的 NF-κB 核易位干扰，朊病毒感染的细胞对 IAV/WSN 感染具有部分抗性，从而激活 NLRP3 炎性小体。因此，朊病毒也可能在病毒感染中发挥保护作用。
