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

Huanzhou Xu; Ibukun A Akinyemi; Siddhi A Chitre; Julia C Loeb; John A Lednicky; Michael T McIntosh; Sumita Bhaduri-McIntosh

doi:10.1016/j.virol.2022.01.003

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

Virology. 2022 Mar:568:13-22. doi: 10.1016/j.virol.2022.01.003. Epub 2022 Jan 17.

Authors

Huanzhou Xu¹, Ibukun A Akinyemi², Siddhi A Chitre¹, Julia C Loeb³, John A Lednicky³, Michael T McIntosh⁴, Sumita Bhaduri-McIntosh⁵

Affiliations

¹ Division of Infectious Disease, Department of Pediatrics, University of Florida, Gainesville, FL, USA.
² Child Health Research Institute, Department of Pediatrics, University of Florida, Gainesville, FL, USA.
³ Department of Environmental and Global Health, College of Public Health and Health Professions, University of Florida, Gainesville, FL, USA; Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA.
⁴ Child Health Research Institute, Department of Pediatrics, University of Florida, Gainesville, FL, USA; Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL, USA.
⁵ Division of Infectious Disease, Department of Pediatrics, University of Florida, Gainesville, FL, USA; Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL, USA. Electronic address: sbhadurimcintosh@ufl.edu.

Abstract

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.

Keywords: Antiviral; COVID-19; Cytokine; NLRP3 inflammasome; ORF3a; SARS-CoV-2; Viroporin.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Amino Acid Sequence
Antiviral Agents / pharmacology
COVID-19 / metabolism*
COVID-19 / virology*
Cell Death
Cell Line
Host-Pathogen Interactions
Humans
Inflammasomes / metabolism*
Models, Biological
NLR Family, Pyrin Domain-Containing 3 Protein / metabolism*
Open Reading Frames
Potassium / metabolism
SARS-CoV-2 / physiology*
Signal Transduction* / drug effects
Viroporin Proteins / chemistry
Viroporin Proteins / genetics*
Viroporin Proteins / metabolism

Substances

Antiviral Agents
Inflammasomes
NLR Family, Pyrin Domain-Containing 3 Protein
Viroporin Proteins
Potassium