SARS-CoV-2 viroporin encoded by ORF3a triggers the NLRP3 inflammatory pathway

• Published in: Virology (New York, N.Y.) N.Y.), 2022-03, Vol.568, p.13-22
• Main Authors: Xu, Huanzhou, Akinyemi, Ibukun A., Chitre, Siddhi A., Loeb, Julia C., Lednicky, John A., McIntosh, Michael T., Bhaduri-McIntosh, Sumita
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Antiviral; Antiviral Agents - pharmacology; Cell Death; Cell Line; COVID-19; COVID-19 - metabolism; COVID-19 - virology; Cytokine; Host-Pathogen Interactions; Humans; Inflammasomes - metabolism; Models, Biological; NLR Family, Pyrin Domain-Containing 3 Protein - metabolism; NLRP3 inflammasome; Open Reading Frames; ORF3a; Potassium - metabolism; SARS-CoV-2; SARS-CoV-2 - physiology; Signal Transduction - drug effects; Viroporin; Viroporin Proteins - chemistry; Viroporin Proteins - genetics; Viroporin Proteins - metabolism
• ISSN: 0042-6822; 1096-0341
• DOI: 10.1016/j.virol.2022.01.003

Heightened inflammatory response is a prominent feature of severe COVID-19 disease. We report that the SARS-CoV-2 ORF3a viroporin activates the NLRP3 inflammasome, the most promiscuous of known inflammasomes. Ectopically expressed ORF3a triggers IL-1β expression via NFκB, thus priming the inflammasome. ORF3a also activates the NLRP3 inflammasome but not NLRP1 or NLRC4, resulting in maturation of IL-1β and cleavage/activation of Gasdermin. Notably, ORF3a activates the NLRP3 inflammasome via both ASC-dependent and -independent modes. This inflammasome activation requires efflux of potassium ions and oligomerization between the kinase NEK7 and NLRP3. Importantly, infection of epithelial cells with SARS-CoV-2 similarly activates the NLRP3 inflammasome. With the NLRP3 inhibitor MCC950 and select FDA-approved oral drugs able to block ORF3a-mediated inflammasome activation, as well as key ORF3a amino acid residues needed for virus release and inflammasome activation conserved in the new variants of SARS-CoV-2 isolates across continents, ORF3a and NLRP3 present prime targets for intervention. •SARS-CoV-2 viroporin ORF3a activates the NLRP3 inflammasome.•ORF3a activates the NLRP3 inflammasome via K ion efflux and the NEK7 kinase.•Select FDA-approved oral drugs are able to block ORF3a-mediated inflammasome activation.•ORF3a and NLRP3 represent therapeutic targets against SARS-CoV-2.