Severe acute respiratory syndrome coronavirus ORF3a protein activates the NLRP3 inflammasome by promoting TRAF3-dependent ubiquitination of ASC

• Published in: The FASEB journal Vol. 33; no. 8; p. 8865
• Main Authors: Siu, Kam-Leung, Yuen, Kit-San, Castaño-Rodriguez, Carlos, Ye, Zi-Wei, Yeung, Man-Lung, Fung, Sin-Yee, Yuan, Shuofeng, Chan, Chi-Ping, Yuen, Kwok-Yung, Enjuanes, Luis, Jin, Dong-Yan
• Format: Journal Article
• Language: English
• Published: United States 01.08.2019
• Subjects: A549 Cells; Animals; CARD Signaling Adaptor Proteins - metabolism; Chlorocebus aethiops; HEK293 Cells; Humans; Inflammasomes - metabolism; NLR Family, Pyrin Domain-Containing 3 Protein - metabolism; SARS Virus - metabolism; TNF Receptor-Associated Factor 3 - metabolism; Ubiquitination; Vero Cells; Viral Structural Proteins - metabolism; SARS coronavirus
• ISSN: 1530-6860
• DOI: 10.1096/fj.201802418R

Severe acute respiratory syndrome coronavirus (SARS-CoV) is capable of inducing a storm of proinflammatory cytokines. In this study, we show that the SARS-CoV open reading frame 3a (ORF3a) accessory protein activates the NLRP3 inflammasome by promoting TNF receptor-associated factor 3 (TRAF3)-mediated ubiquitination of apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC). SARS-CoV and its ORF3a protein were found to be potent activators of pro-IL-1β gene transcription and protein maturation, the 2 signals required for activation of the NLRP3 inflammasome. ORF3a induced pro-IL-1β transcription through activation of NF-κB, which was mediated by TRAF3-dependent ubiquitination and processing of p105. ORF3a-induced elevation of IL-1β secretion was independent of its ion channel activity or absent in melanoma 2 but required NLRP3, ASC, and TRAF3. ORF3a interacted with TRAF3 and ASC, colocalized with them in discrete punctate structures in the cytoplasm, and facilitated ASC speck formation. TRAF3-dependent K63-linked ubiquitination of ASC was more pronounced in SARS-CoV-infected cells or when ORF3a was expressed. Taken together, our findings reveal a new mechanism by which SARS-CoV ORF3a protein activates NF-κB and the NLRP3 inflammasome by promoting TRAF3-dependent ubiquitination of p105 and ASC.-Siu, K.-L., Yuen, K.-S., Castaño-Rodriguez, C., Ye, Z.-W., Yeung, M.-L., Fung, S.-Y., Yuan, S., Chan, C.-P., Yuen, K.-Y., Enjuanes, L., Jin, D.-Y. Severe acute respiratory syndrome coronavirus ORF3a protein activates the NLRP3 inflammasome by promoting TRAF3-dependent ubiquitination of ASC.