title: Ebola Virus Does Not Induce Stress Granule Formation during Infection and Sequesters Stress Granule Proteins within Viral Inclusions.
abstract: A hallmark of Ebola virus (EBOV) infection is the formation of viral inclusions in the cytoplasm of infected cells. These viral inclusions contain the EBOV nucleocapsids and are sites of viral replication and nucleocapsid maturation. Although there is growing evidence that viral inclusions create a protected environment that fosters EBOV replication, little is known about their role in the host response to infection. The cellular stress response is an effective antiviral strategy that leads to stress granule (SG) formation and translational arrest mediated by the phosphorylation of a translation initiation factor, the α subunit of eukaryotic initiation factor 2 (eIF2α). Here, we show that selected SG proteins are sequestered within EBOV inclusions, where they form distinct granules that colocalize with viral RNA. These inclusion-bound (IB) granules are functionally and structurally different from canonical SGs. Formation of IB granules does not indicate translational arrest in the infected cells. We further show that EBOV does not induce formation of canonical SGs or eIF2α phosphorylation at any time postinfection but is unable to fully inhibit SG formation induced by different exogenous stressors, including sodium arsenite, heat, and hippuristanol. Despite the sequestration of SG marker proteins into IB granules, canonical SGs are unable to form within inclusions, which we propose might be mediated by a novel function of VP35, which disrupts SG formation. This function is independent of VP35's RNA binding activity. Further studies aim to reveal the mechanism for SG protein sequestration and precise function within inclusions.
  
  
  
  Although progress has been made developing antiviral therapeutics and vaccines against the highly pathogenic Ebola virus (EBOV), the cellular mechanisms involved in EBOV infection are still largely unknown. To better understand these intracellular events, we investigated the cellular stress response, an antiviral pathway manipulated by many viruses. We show that EBOV does not induce formation of stress granules (SGs) in infected cells and is therefore unrestricted by their concomitant translational arrest. We identified SG proteins sequestered within viral inclusions, which did not impair protein translation. We further show that EBOV is unable to block SG formation triggered by exogenous stress early in infection. These findings provide insight into potential targets of therapeutic intervention. Additionally, we identified a novel function of the interferon antagonist VP35, which is able to disrupt SG formation.
authors.affiliation: Department of Microbiology, Boston University School of Medicine, Boston University, Boston, Massachusetts, USA.|National Emerging Infectious Diseases Laboratories, Boston University, Boston, Massachusetts, USA.
authors.forename: Emily V
authors.initials: EV
authors.lastname: Nelson
authors.affiliation: Department of Microbiology, Boston University School of Medicine, Boston University, Boston, Massachusetts, USA.|National Emerging Infectious Diseases Laboratories, Boston University, Boston, Massachusetts, USA.
authors.forename: Kristina M
authors.initials: KM
authors.lastname: Schmidt
authors.affiliation: Department of Microbiology, Boston University School of Medicine, Boston University, Boston, Massachusetts, USA.|National Emerging Infectious Diseases Laboratories, Boston University, Boston, Massachusetts, USA.
authors.forename: Laure R
authors.initials: LR
authors.lastname: Deflubé
authors.affiliation: Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.
authors.forename: Sultan
authors.initials: S
authors.lastname: Doğanay
authors.affiliation: Laboratory of Virology, Rocky Mountain Laboratories, Division of Intrumural Research, NIAID, NIH, Hamilton, Montana, USA.
authors.forename: Logan
authors.initials: L
authors.lastname: Banadyga
authors.affiliation: Department of Microbiology, Boston University School of Medicine, Boston University, Boston, Massachusetts, USA.|National Emerging Infectious Diseases Laboratories, Boston University, Boston, Massachusetts, USA.
authors.forename: Judith
authors.initials: J
authors.lastname: Olejnik
authors.affiliation: Department of Microbiology, Boston University School of Medicine, Boston University, Boston, Massachusetts, USA.|National Emerging Infectious Diseases Laboratories, Boston University, Boston, Massachusetts, USA.
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Hume
authors.affiliation: Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of Russian Academy of Science, Novosibirsk, Russian Federation.
authors.forename: Elena
authors.initials: E
authors.lastname: Ryabchikova
authors.affiliation: Laboratory of Virology, Rocky Mountain Laboratories, Division of Intrumural Research, NIAID, NIH, Hamilton, Montana, USA.
authors.forename: Hideki
authors.initials: H
authors.lastname: Ebihara
authors.affiliation: Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital, Boston, Massachusetts, USA.
authors.forename: Nancy
authors.initials: N
authors.lastname: Kedersha
authors.affiliation: Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.
authors.forename: Taekjip
authors.initials: T
authors.lastname: Ha
authors.affiliation: Department of Microbiology, Boston University School of Medicine, Boston University, Boston, Massachusetts, USA muehlber@bu.edu.|National Emerging Infectious Diseases Laboratories, Boston University, Boston, Massachusetts, USA.
authors.forename: Elke
authors.initials: E
authors.lastname: Mühlberger
mesh_terms: D000818:Animals; D002460:Cell Line; D003593:Cytoplasm / Q000821:virology*; D003594:Cytoplasmic Granules / Q000378:metabolism; D029043:Ebolavirus / Q000254:growth & development* / Q000276:immunology; D006360:Heat-Shock Proteins / Q000032:analysis; D054884:Host-Pathogen Interactions; D006801:Humans; D007155:Immunologic Factors / Q000032:analysis*; D007181:Inclusion Bodies, Viral / Q000737:chemistry / Q000821:virology*; D013312:Stress, Physiological; D054334:Viral Regulatory and Accessory Proteins / Q000378:metabolism*
chemical_list: D006360:Heat-Shock Proteins; D007155:Immunologic Factors; C080980:VP35 protein, filovirus; D054334:Viral Regulatory and Accessory Proteins