The SARS (severe acute respiratory syndrome) outbreak was caused by a coronavirus (CoV) named the SARS-CoV. SARS pathology is propagated both by direct cytotoxic effects of the virus and aberrant activation of the innate immune response. Here, we identify several mechanisms by which a SARS-CoV open reading frame (ORF) activates intracellular stress pathways and targets the innate immune response. We show that ORF8b forms insoluble intracellular aggregates dependent on a valine at residue 77. Aggregated ORF8b induces endoplasmic reticulum (ER) stress, lysosomal damage, and subsequent activation of the master regulator of the autophagy and lysosome machinery, Transcription factor EB (TFEB). ORF8b causes cell death in epithelial cells, which is partially rescued by reducing its ability to aggregate. In macrophages, ORF8b robustly activates the NLRP3 inflammasome by providing a potent signal 2 required for activation. Mechanistically, ORF8b interacts directly with the Leucine Rich Repeat domain of NLRP3 and localizes with NLRP3 and ASC in cytosolic dot-like structures. ORF8b triggers cell death consistent with pyroptotic cell death in macrophages. While in those cells lacking NLRP3 accumulating ORF8b cytosolic aggregates cause ER stress, mitochondrial dysfunction, and caspase-independent cell death.

SARS（严重急性呼吸道综合症）暴发是由冠状病毒（CoV）引起的，该冠状病毒名为SARS-CoV。SARS病理通过病毒的直接细胞毒性作用和先天免疫应答的异常激活而传播。在这里，我们确定了SARS-CoV开放阅读框（ORF）激活细胞内应激途径并靶向先天免疫应答的几种机制。我们显示，ORF8b形成依赖于缬氨酸在残基77的不溶性细胞内聚集体。聚集的ORF8b诱导内质网（ER）压力，溶酶体损伤，并随后激活自噬和溶酶体机制，转录因子EB（TFEB）的主调节剂。ORF8b导致上皮细胞死亡，这是通过降低其聚集能力而部分挽救的。在巨噬细胞中 ORF8b通过提供激活所需的有效信号2来强烈激活NLRP3炎性体。从机制上讲，ORF8b与NLRP3的亮氨酸富集重复域直接相互作用，并在细胞质点状结构中定位于NLRP3和ASC。ORF8b触发的细胞死亡与巨噬细胞中的焦细胞死亡一致。在缺少NLRP3的那些细胞中，ORF8b的胞质聚集体会引起ER应激，线粒体功能障碍和不依赖caspase的细胞死亡。