EVM005: An Ectromelia-Encoded Protein with Dual Roles in NF-κB Inhibition and Virulence

PLoS Pathogens

R. Mark Buller¹  Scott Parker¹  Jill Schriewer¹  Kristin Burles²  Michele Barry²  Ninad Mehta²  Nicholas van Buuren² 

[1] Department of Molecular Microbiology and Immunology, Saint Louis University School of Medicine, St. Louis, Missouri, United States of America;Li Ka Shing Institute of Virology, Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada

关键词: Transcription factors;    Ubiquitin ligases;    HeLa cells;    Polymerase chain reaction;    Cell staining;    Immune response;    Poxviruses;    Virulence factors;   

DOI  :  10.1371/journal.ppat.1004326

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Poxviruses contain large dsDNA genomes encoding numerous open reading frames that manipulate cellular signalling pathways and interfere with the host immune response. The NF-κB signalling cascade is an important mediator of innate immunity and inflammation, and is tightly regulated by ubiquitination at several key points. A critical step in NF-κB activation is the ubiquitination and degradation of the inhibitor of kappaB (IκBα), by the cellular SCFβ-TRCP ubiquitin ligase complex. We show here that upon stimulation with TNFα or IL-1β, Orthopoxvirus-infected cells displayed an accumulation of phosphorylated IκBα, indicating that NF-κB activation was inhibited during poxvirus infection. Ectromelia virus is the causative agent of lethal mousepox, a natural disease that is fatal in mice. Previously, we identified a family of four ectromelia virus genes (EVM002, EVM005, EVM154 and EVM165) that contain N-terminal ankyrin repeats and C-terminal F-box domains that interact with the cellular SCF ubiquitin ligase complex. Since degradation of IκBα is catalyzed by the SCFβ-TRCP ubiquitin ligase, we investigated the role of the ectromelia virus ankyrin/F-box protein, EVM005, in the regulation of NF-κB. Expression of Flag-EVM005 inhibited both TNFα- and IL-1β-stimulated IκBα degradation and p65 nuclear translocation. Inhibition of the NF-κB pathway by EVM005 was dependent on the F-box domain, and interaction with the SCF complex. Additionally, ectromelia virus devoid of EVM005 was shown to inhibit NF-κB activation, despite lacking the EVM005 open reading frame. Finally, ectromelia virus devoid of EVM005 was attenuated in both A/NCR and C57BL/6 mouse models, indicating that EVM005 is required for virulence and immune regulation in vivo.

【 授权许可】

CC BY