Dataset Information

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

ABSTRACT: Activation of NF-?B 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-?B causes massive inflammatory damage to the host, suggesting that regulatory mechanisms to promptly terminate NF-?B 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-?B for degradation, thereby suppressing NF-?B activation. Here we show that PDLIM7, another member of LIM protein family, is also a ubiquitin E3 ligase that inhibits NF-?B-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-?B-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-?B signaling by bridging a ubiquitin E3 ligase and the proteasome.

SUBMITTER: Jodo A

PROVIDER: S-EPMC7417631 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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

Jodo Aya A Shibazaki Azusa A Onuma Asuka A Kaisho Tsuneyasu T Tanaka Takashi T

Frontiers in immunology 20200804

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 th ...[more]

PMID: 32849529

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Project description:Viruses routinely employ strategies to prevent the activation of innate immune signaling in infected cells. Respiratory syncytial virus (RSV) is no exception, as it encodes two accessory proteins (NS1 and NS2) which are well established to block interferon signaling. However, RSV-encoded mechanisms for inhibiting NF-?B signaling are less well characterized. In this study, we identified RSV-mediated antagonism of this pathway, independent of the NS1 and NS2 proteins and indeed distinct from other known viral mechanisms of NF-?B inhibition. In both human and bovine RSV-infected cells, we demonstrated that the p65 subunit of NF-?B is rerouted to perinuclear puncta in the cytoplasm, which are synonymous with viral inclusion bodies (IBs), the site for viral RNA replication. Captured p65 was unable to translocate to the nucleus or transactivate a NF-?B reporter following tumor necrosis factor alpha (TNF-?) stimulation, confirming the immune-antagonistic nature of this sequestration. Subsequently, we used correlative light electron microscopy (CLEM) to colocalize the RSV N protein and p65 within bovine RSV (bRSV) IBs, which are granular, membraneless regions of cytoplasm with liquid organelle-like properties. Additional characterization of bRSV IBs indicated that although they are likely formed by liquid-liquid phase separation (LLPS), they have a differential sensitivity to hypotonic shock proportional to their size. Together, these data identify a novel mechanism for viral antagonism of innate immune signaling which relies on sequestration of the NF-?B subunit p65 to a biomolecular condensate-a mechanism conserved across the Orthopneumovirus genus and not host-cell specific. More generally, they provide additional evidence that RNA virus IBs are important immunomodulatory complexes within infected cells.IMPORTANCE Many viruses replicate almost entirely in the cytoplasm of infected cells; however, how these pathogens are able to compartmentalize their life cycle to provide favorable conditions for replication and to avoid the litany of antiviral detection mechanisms in the cytoplasm remains relatively uncharacterized. In this manuscript, we show that bovine respiratory syncytial virus (bRSV), which infects cattle, does this by generating inclusion bodies in the cytoplasm of infected cells. We confirm that both bRSV and human RSV viral RNA replication takes place in these inclusion bodies, likely meaning these organelles are a functionally conserved feature of this group of viruses (the orthopneumoviruses). Importantly, we also showed that these organelles are able to capture important innate immune transcription factors (in this case NF-KB), blocking the normal signaling processes that tell the nucleus the cell is infected, which may help us to understand how these viruses cause disease.

Project description:Macroautophagy/autophagy plays an important role in the control of viral infections and viruses have evolved multiple strategies to interfere with autophagy to avoid destruction and promote their own replication and spread. Here we report that the deubiquitinase encoded in the N-terminal domain of the Epstein-Barr virus (EBV) large tegument protein, BPLF1, regulates selective autophagy. Mass spectrometry analysis identified several vesicular traffic and autophagy related proteins as BPLF1 interactors and potential substrates, suggesting that the viral protein targets this cellular defense during productive infection. Direct binding of BPLF1 to the autophagy receptor SQSTM1/p62 (sequestosome 1) was confirmed by co-immunoprecipitation of transfected BPLF1 and by in vitro affinity isolation of bacterially expressed proteins. Expression of the catalytically active BPLF1 was associated with decreased SQSTM1/p62 ubiquitination and failure to recruit LC3 to SQSTM1/p62-positive aggregates. Selective autophagy was inhibited as illustrated by the accumulation of large protein aggregates in BPLF1-positive cells co-transfected with an aggregate-prone HTT (huntingtin)-Q109 construct, and by a slower autophagy-dependent clearance of protein aggregates upon transfection of BPLF1 in cells expressing a tetracycline-regulated HTT-Q103. The inhibition of aggregate clearance was restored by overexpression of a SQSTM1/p62[E409A,K420R] mutant that does not require ubiquitination of Lys420 for cargo loading. These findings highlight a previously unrecognized role of the viral deubiquitinase in the regulation of selective autophagy, which may promote infection and the production of infectious virus.Abbreviations: BPLF1, BamH1 fragment left open reading frame-1; EBV, Epstein-Barr virus; GFP, green fluorescent protein; HTT, huntingtin; MAP1LC3/LC3, microtubule associated protein 1 light chain 3; PB1, Phox and Bem1 domain; PE, phosphatidylethanolamine; SQSTM1/p62, sequestosome 1; UBA, ubiquitin-associated domain.

Dataset Information

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

Publications

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

Similar Datasets

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