BPOZ-2 is a negative regulator of the NLPR3 inflammasome contributing to SARS-CoV-2-induced hyperinflammation

Front Cell Infect Microbiol. 2023 Mar 2:13:1134511. doi: 10.3389/fcimb.2023.1134511. eCollection 2023.

Abstract

Introduction: Inflammation play important roles in the initiation and progression of acute lung injury (ALI), acute respiratory distress syndrome (ARDS), septic shock, clotting dysfunction, or even death associated with SARS-CoV-2 infection. However, the pathogenic mechanisms underlying SARS-CoV-2-induced hyperinflammation are still largely unknown.

Methods: The animal model of septic shock and ALI was established after LPS intraperitoneal injection or intratracheal instillation. Bone marrow-derived macrophages (BMDMs) from WT and BPOZ-2 KO mouse strains were harvested from the femurs and tibias of mice. Immunohistology staining, ELISA assay, coimmunoprecipitation, and immunoblot analysis were used to detect the histopathological changes of lung tissues and the expression of inflammatory factors and protein interaction.

Results and conclusions: We show a distinct mechanism by which the SARS-CoV-2 N (SARS-2-N) protein targets Bood POZ-containing gene type 2 (BPOZ-2), a scaffold protein for the E3 ubiquitin ligase Cullin 3 that we identified as a negative regulator of inflammatory responses, to promote NLRP3 inflammasome activation. We first demonstrated that BPOZ-2 knockout (BPOZ-2 KO) mice were more susceptible to lipopolysaccharide (LPS)-induced septic shock and ALI and showed increased serum IL-1β levels. In addition, BMDMs isolated from BPOZ-2 KO mice showed increased IL-1β production in response to NLRP3 stimuli. Mechanistically, BPOZ-2 interacted with NLRP3 and mediated its degradation by recruiting Cullin 3. In particular, the expression of BPOZ-2 was significantly reduced in lung tissues from mice infected with SARS-CoV-2 and in cells overexpressing SARS-2-N. Importantly, proinflammatory responses triggered by the SARS-2-N were significantly blocked by BPOZ-2 reintroduction. Thus, we concluded that BPOZ-2 is a negative regulator of the NLPR3 inflammasome that likely contributes to SARS-CoV-2-induced hyperinflammation.

Keywords: BPOZ-2; NLPR3; SARS-CoV-2; hyperinflammation; inflammasome.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acute Lung Injury* / metabolism
  • Animals
  • COVID-19*
  • Cullin Proteins
  • Inflammasomes / metabolism
  • Lipopolysaccharides / pharmacology
  • Mice
  • Mice, Inbred C57BL
  • NLR Family, Pyrin Domain-Containing 3 Protein* / genetics
  • NLR Family, Pyrin Domain-Containing 3 Protein* / metabolism
  • Nuclear Proteins* / genetics
  • Nuclear Proteins* / metabolism
  • SARS-CoV-2 / metabolism
  • Shock, Septic*

Substances

  • Cullin Proteins
  • Inflammasomes
  • Lipopolysaccharides
  • NLR Family, Pyrin Domain-Containing 3 Protein
  • Abtb2 protein, mouse
  • Nuclear Proteins

Grants and funding

This work was supported by the Postdoctoral Science Foundation of China (Grant number: 2020M683743), the National Key Research and Development Program of China (Grant number: 2018YFA0900800), and the National Natural Science Foundation of China (Grant numbers: 32070755, 31872715, 81972696, 81773205, 82070595, and 92168207).