title: Suppressor of Cytokine Signaling 3 Is an Inducible Host Factor That Regulates Virus Egress during Ebola Virus Infection.
abstract: Ebola virus (EBOV) initially targets monocytes and macrophages, which can lead to the release of proinflammatory cytokines and chemokines. These inflammatory cytokines are thought to contribute to the development of circulatory shock seen in fatal EBOV infections. The VP40 matrix protein is a key viral structural protein that is critical for virion egress. Physical and functional interactions between VP40 and host proteins such as Tsg101 and Nedd4 facilitate efficient release of VP40-driven virus-like particles (VLPs) and infectious virus. Here, we show that host suppressor of cytokine signaling 3 (SOCS3) can also bind to EBOV VP40, leading to enhanced ubiquitinylation and egress of VP40. Indeed, titers of infectious EBOV derived from SOCS3 knockout mouse embryonic fibroblasts (MEFs) were significantly reduced compared to those from wild-type (WT) MEFs at 24 and 48 h postinfection. Importantly, this reduced virus yield could be rescued back to WT levels by exogenously expressing SOCS3. Lastly, we show that SOCS3 expression is induced by EBOV glycoprotein (GP) expression and that VLPs containing EBOV VP40 and GP induced production of proinflammatory cytokines, which induced SOCS3 for negative-feedback regulation. These data indicate that host innate immune protein SOCS3 may play an important role in budding and pathogenesis of EBOV.
  
  
  OBJECTIVE
  The VP40 matrix protein is a key structural protein critical for Ebola virus budding. Physical and functional interactions between VP40 and host proteins such as Tsg101 and Nedd4 facilitate efficient release of VLPs and infectious virus. We reported that host TLR4 is a sensor for Ebola GP on VLPs and that the resultant TLR4 signaling pathways lead to the production of proinflammatory cytokines. Host SOCS3 regulates the innate immune response by controlling and limiting the proinflammatory response through negative-feedback inhibition of cytokine receptors. We present evidence that Ebola virus VLPs stimulate induction of SOCS3 as well as proinflammatory cytokines, and that expression of human SOCS3 enhances budding of Ebola VLPs and infectious virus via a mechanism linked to the host ubiquitinylation machinery.
authors.affiliation: Department of Microbiology, School of Medicine, University of Washington, Seattle, Washington, USA Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rocky Mountain Laboratories, Hamilton, Montana, USA.
authors.forename: Atsushi
authors.identifier: http://orcid.org/0000-0002-7779-3059
authors.initials: A
authors.lastname: Okumura
authors.affiliation: Department of Microbiology, School of Medicine, University of Washington, Seattle, Washington, USA.
authors.forename: Angela L
authors.initials: AL
authors.lastname: Rasmussen
authors.affiliation: Influenza Research Institute, Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Halfmann
authors.affiliation: Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rocky Mountain Laboratories, Hamilton, Montana, USA.
authors.forename: Friederike
authors.initials: F
authors.lastname: Feldmann
authors.affiliation: Department of Microbiology and Immunology, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Yoshimura
authors.affiliation: Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rocky Mountain Laboratories, Hamilton, Montana, USA.
authors.forename: Heinz
authors.initials: H
authors.lastname: Feldmann
authors.affiliation: Influenza Research Institute, Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo Japan ERATO Infection-Induced Host Responses Project, Japan Science and Technology Agency, Kawaguchi, Saitama, Japan Department of Special Pathogens, International Research Center for Infectious Diseases, Institute of Medical Science, University of Tokyo, Tokyo, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kawaoka
authors.affiliation: Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Ronald N
authors.initials: RN
authors.lastname: Harty
authors.affiliation: Department of Microbiology, School of Medicine, University of Washington, Seattle, Washington, USA Washington National Primate Research Center, Seattle, Washington, USA honey@uw.edu.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Katze
mesh_terms: D000818:Animals; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D029043:Ebolavirus / Q000235:genetics / Q000378:metabolism; D056827:Endosomal Sorting Complexes Required for Transport / Q000235:genetics / Q000378:metabolism; D025461:Feedback, Physiological; D005347:Fibroblasts / Q000378:metabolism* / Q000821:virology; D015967:Gene Expression Regulation, Viral; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D054884:Host-Pathogen Interactions; D006801:Humans; D008264:Macrophages / Q000378:metabolism* / Q000821:virology; D051379:Mice; D008810:Mice, Inbred C57BL; D000075702:Nedd4 Ubiquitin Protein Ligases; D009698:Nucleoproteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000235:genetics / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism; D054875:Ubiquitination; D014758:Viral Core Proteins / Q000235:genetics / Q000378:metabolism*; D014771:Virion / Q000235:genetics / Q000378:metabolism; D057074:Virus Release / Q000235:genetics*; D000099177:Tsg101 Protein
chemical_list: D004268:DNA-Binding Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D006023:Glycoproteins; D000075702:Nedd4 Ubiquitin Protein Ligases; D009698:Nucleoproteins; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D051197:Toll-Like Receptor 4; D014157:Transcription Factors; D044767:Ubiquitin-Protein Ligases; D014758:Viral Core Proteins; D000099177:Tsg101 Protein; C106644:SOCS3 protein, human; C495345:TLR4 protein, human; C084819:nucleoprotein VP40, Ebola virus; C000618483:Nedd4 protein, human; C000618461:Nedd4l protein, mouse