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Poxvirus targeting of E3 ligase ?-TrCP by molecular mimicry: a mechanism to inhibit NF-?B activation and promote immune evasion and virulence.

ABSTRACT: The transcription factor NF-?B is essential for immune responses against pathogens and its activation requires the phosphorylation, ubiquitination and proteasomal degradation of I?B?. Here we describe an inhibitor of NF-?B from vaccinia virus that has a closely related counterpart in variola virus, the cause of smallpox, and mechanistic similarity with the HIV protein Vpu. Protein A49 blocks NF-?B activation by molecular mimicry and contains a motif conserved in I?B? which, in I?B?, is phosphorylated by IKK? causing ubiquitination and degradation. Like I?B?, A49 binds the E3 ligase ?-TrCP, thereby preventing ubiquitination and degradation of I?B?. Consequently, A49 stabilised phosphorylated I?B? (p-I?B?) and its interaction with p65, so preventing p65 nuclear translocation. Serine-to-alanine mutagenesis within the I?B?-like motif of A49 abolished ?-TrCP binding, stabilisation of p-I?B? and inhibition of NF-?B activation. Remarkably, despite encoding nine other inhibitors of NF-?B, a VACV lacking A49 showed reduced virulence in vivo.

SUBMITTER: Mansur DS

PROVIDER: S-EPMC3585151 | biostudies-literature | 2013 Feb

REPOSITORIES: biostudies-literature

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Poxvirus targeting of E3 ligase β-TrCP by molecular mimicry: a mechanism to inhibit NF-κB activation and promote immune evasion and virulence.

Mansur Daniel S DS Maluquer de Motes Carlos C Unterholzner Leonie L Sumner Rebecca P RP Ferguson Brian J BJ Ren Hongwei H Strnadova Pavla P Bowie Andrew G AG Smith Geoffrey L GL

PLoS pathogens 20130228 2

The transcription factor NF-κB is essential for immune responses against pathogens and its activation requires the phosphorylation, ubiquitination and proteasomal degradation of IκBα. Here we describe an inhibitor of NF-κB from vaccinia virus that has a closely related counterpart in variola virus, the cause of smallpox, and mechanistic similarity with the HIV protein Vpu. Protein A49 blocks NF-κB activation by molecular mimicry and contains a motif conserved in IκBα which, in IκBα, is phosphory ...[more]

PMID: 23468625

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Project description:NF-κB plays a critical role in the induction and maintenance of innate and adaptive immune transcriptional programs. An associated inhibitor of κB protein (IκB) regulates NF-κB activation and contains a degron motif (DSGΦxS) that undergoes phosphorylation following pathogen recognition or other proinflammatory signals. The E3 ubiquitin ligase SCF(β-TrCP) recognizes this phosphodegron through its β-transducin repeat-containing protein (β-TrCP) subunit and induces IκB degradation, allowing NF-κB to translocate to the nucleus and modulate gene expression. Rotavirus (RV), a major cause of pediatric gastroenteritis, can block NF-κB activation through the action of its nonstructural protein NSP1, a putative E3 ubiquitin ligase that mediates the degradation of β-TrCP or other immunomodulatory proteins in a virus strain-specific manner. Here, we show that NSP1 targets β-TrCP by mimicking the IκB phosphodegron. The NSP1 proteins of most human and porcine RV strains conserve a C-terminal phosphodegron-like (PDL) motif, DSGΦS. Deletion of this motif or mutation of its serine residues disrupts NSP1-mediated degradation of β-TrCP and inhibition of NF-κB activation. Additionally, a point mutation within the phosphodegron-binding pocket protects β-TrCP from NSP1-mediated turnover. Fusion of the PDL motif to an NSP1 protein known to target other immunomodulatory proteins generates a chimeric NSP1 protein that can induce β-TrCP degradation and block NF-κB activation. Other viral proteins (Epstein-Barr virus LMP1, HIV-1 Vpu, and vaccinia virus A49) also contain a PDL motif and interact with β-TrCP to inhibit NF-κB activation. Taken together, these data suggest that targeting β-TrCP by molecular mimicry may be a common strategy used by human viruses to evade the host immune response. The transcription factor NF-κB, a central regulator of the host response to infection, is a frequent target of viral antagonism. Pathogen detection activates NF-κB by inducing the phosphorylation of an associated inhibitor protein (IκB), which targets IκB for degradation by the E3 ubiquitin ligase β-TrCP. Rotavirus, a significant cause of childhood gastroenteritis, antagonizes NF-κB through the activity of its NSP1 protein, a putative E3 ubiquitin ligase that mediates β-TrCP turnover. Here, we show that NSP1 functions by mimicking the IκB phosphodegron recognized by β-TrCP. Nearly all human rotavirus strains conserve this motif at the NSP1 C terminus, and its removal disrupts NSP1 antagonist activity. This sequence conserves the biochemical properties of the IκB phosphodegron and can rescue antagonist activity when fused to an NSP1 protein otherwise inactive against β-TrCP. Other viral proteins also mimic IκB to disrupt NF-κB activation, indicating that this is an important immune evasion strategy.

Dataset Information

Poxvirus targeting of E3 ligase ?-TrCP by molecular mimicry: a mechanism to inhibit NF-?B activation and promote immune evasion and virulence.

Publications

Poxvirus targeting of E3 ligase β-TrCP by molecular mimicry: a mechanism to inhibit NF-κB activation and promote immune evasion and virulence.

Similar Datasets

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