PDLIM7 Synergizes With PDLIM2 and p62/Sqstm1 to Inhibit Inflammatory Signaling by Promoting Degradation of the p65 Subunit of NF-κB

Front Immunol. 2020 Aug 4;11:1559. doi: 10.3389/fimmu.2020.01559. eCollection 2020.

Abstract

Activation of NF-κB transcription factors is critical for innate immune cells to induce inflammation and fight against microbial pathogens. On the other hand, the excessive and prolonged activation of NF-κB causes massive inflammatory damage to the host, suggesting that regulatory mechanisms to promptly terminate NF-κB activation are important to prevent immunopathology. We have previously reported that PDLIM2, a PDZ-LIM domain-containing protein, is a nuclear ubiquitin E3 ligase that targets the p65 subunit of NF-κB for degradation, thereby suppressing NF-κB activation. Here we show that PDLIM7, another member of LIM protein family, is also a ubiquitin E3 ligase that inhibits NF-κB-mediated inflammatory responses. PDLIM7 directly polyubiquitinates p65 and promotes its proteasomal degradation. Moreover, PDLIM7 heterodimerizes with PDLIM2 to promote synergistic PDLIM2-mediated degradation of p65. Mechanistically, PDLIM7 promotes K63-linked ubiquitination of PDLIM2 and then the proteasome/autophagosome cargo protein p62/Sqstm1 binds to both polyubiquitinated PDLIM2 and the proteasome, thereby facilitating the delivery of the NF-κB-PDLIM2 complex to the proteasome and subsequent p65 degradation. Consistently, double knockdown of PDLIM7 and either PDLIM2 or p62/Sqstm1 results in augmented proinflammatory cytokine production compared to control cells or single knockdown cells. These data delineate a new role for PDLIM7 and p62/Sqstm1 in the regulation of NF-κB signaling by bridging a ubiquitin E3 ligase and the proteasome.

Keywords: LIM protein; NF-κB; inflammation; p62/Sqstm1; ubiquitin E3 ligase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Animals
  • Cell Line
  • Cytoskeletal Proteins / deficiency
  • Cytoskeletal Proteins / genetics
  • Cytoskeletal Proteins / metabolism*
  • Disease Susceptibility*
  • Enzyme Activation
  • Gene Expression Regulation
  • Humans
  • Inflammation / etiology*
  • Inflammation / metabolism*
  • Intracellular Signaling Peptides and Proteins / deficiency
  • Intracellular Signaling Peptides and Proteins / genetics
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • LIM Domain Proteins / deficiency
  • LIM Domain Proteins / genetics
  • LIM Domain Proteins / metabolism*
  • Lipopolysaccharides / adverse effects
  • Lipopolysaccharides / immunology
  • Mice
  • NF-kappa B / chemistry
  • NF-kappa B / metabolism*
  • Proteasome Endopeptidase Complex / metabolism
  • Protein Binding
  • Protein Interaction Domains and Motifs
  • Protein Multimerization
  • Proteolysis
  • RNA, Small Interfering / genetics
  • Signal Transduction*
  • Ubiquitin-Protein Ligases / metabolism
  • Ubiquitination

Substances

  • Adaptor Proteins, Signal Transducing
  • Cytoskeletal Proteins
  • Intracellular Signaling Peptides and Proteins
  • LIM Domain Proteins
  • Lipopolysaccharides
  • NF-kappa B
  • Pdlim2 protein, mouse
  • Pdlim7 protein, mouse
  • RNA, Small Interfering
  • Ubiquitin-Protein Ligases
  • Proteasome Endopeptidase Complex