Different Temporal Effects of Ebola Virus VP35 and VP24 Proteins on Global Gene Expression in Human Dendritic Cells

Ilinykh, Philipp A.; Lubaki, Ndongala Michel; Widen, Steven G.; Renn, Lynnsey; Theisen, Terence C.; Rabin, Ronald L.; Wood, Thomas G.; Bukreyev, Alexander

doi:10.1128/jvi.00924-15

Cited by 55 publications

(65 citation statements)

References 57 publications

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“…In prior studies, mutations that disrupt eVP35 RIG-I inhibitory function allowed EBOV to trigger DC maturation; however, a K142A eVP24 point mutation that impairs interaction with KPNAs and decreases eVP24 inhibition of IFN signaling also affected the inhibition of DC maturation, leading to the conclusion that eVP35 and eVP24 work in cooperation to impair DC function (28). Global analysis of DC gene expression after infection with wild-type and mutant eVP35 and eVP24 viruses demonstrated little host response to wild-type virus infection and identified an impact of eVP24 mutations that was kinetically different from changes induced by the eVP35 virus (32). These results support the possibility that eVP24 IFN signaling inhibition contributes to suppression of DC maturation.…”

Section: Dcs Are Significant Targets Of Filovirus Infection In Vivo mentioning

confidence: 66%

“…eVP24 antagonizes IFN-␣/␤ and IFN-␥ signaling pathways by inhibiting the nuclear translocation of PY-STAT1, thereby inhibiting ISG transcription (21). In addition, EBOVs with mutated eVP24s trigger altered DC responses (28,32). However, whether eVP24 is sufficient to inhibit DC responses has not been investigated.…”

Section: Resultsmentioning

confidence: 99%

“…Infection of DCs with recombinant EBOVs bearing mutations that disrupt VP35 dsRNA-binding and RLR inhibition results in significant DC maturation, definitively linking eVP35 to DC suppression in the context of EBOV infection (28). Although eVP35 expression is sufficient to suppress DC maturation, studies in DCs infected with mutant EBOVs suggest that eVP24 may also modulate DC responses and that eVP24 cooperates with eVP35 to modulate DC responses to EBOVs (32).…”

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confidence: 99%

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Effects of Filovirus Interferon Antagonists on Responses of Human Monocyte-Derived Dendritic Cells to RNA Virus Infection

Yen

Basler

2016

J Virol

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Dendritic cells (DCs) are major targets of filovirus infection in vivo. Previous studies have shown that the filoviruses Ebola virus (EBOV) and Marburg virus (MARV) suppress DC maturation in vitro.Both viruses also encode innate immune evasion functions. The EBOV VP35 (eVP35) and the MARV VP35 (mVP35) proteins each can block RIG-I-like receptor signaling and alpha/ beta interferon (IFN-␣/␤) production. The EBOV VP24 (eVP24) and MARV VP40 (mVP40) proteins each inhibit the production of IFN-stimulated genes (ISGs) by blocking Jak-STAT signaling; however, this occurs by different mechanisms, with eVP24 blocking nuclear import of tyrosine-phosphorylated STAT1 and mVP40 blocking Jak1 function. MARV VP24 (mVP24) has been demonstrated to modulate host cell antioxidant responses. Previous studies demonstrated that eVP35 is sufficient to strongly impair primary human monocyte-derived DC (MDDC) responses upon stimulation induced through the RIG-I-like receptor pathways. We demonstrate that mVP35, like eVP35, suppresses not only IFN-␣/␤ production but also proinflammatory responses after stimulation of MDDCs with RIG-I activators. In contrast, eVP24 and mVP40, despite suppressing ISG production upon RIG-I activation, failed to block upregulation of maturation markers or T cell activation. mVP24, although able to stimulate expression of antioxidant response genes, had no measurable impact of DC function. These data are consistent with a model where filoviral VP35 proteins are the major suppressors of DC maturation during filovirus infection, whereas the filoviral VP24 proteins and mVP40 are insufficient to prevent DC maturation. Zaire ebolavirus (EBOV) and Marburg marburgvirus (MARV) belong to the Filovirus family of emerging, zoonotic negativesense RNA viruses. Both EBOV and MARV cause severe, frequently fatal disease in humans (1). The West African Ebola epidemic, which was first recognized in early 2014, is the largest filovirus outbreak on record with over 28,000 cases worldwide and a reported case fatality rate of approximately 40% (2). The severity of EBOV and MARV infections reflects, at least in part, robust systemic virus replication that is not effectively restrained by host immune responses (3).Both EBOV and MARV encode multiple proteins that impair innate antiviral immune responses and likely contribute to excessive virus replication (3, 4). Both viruses encode VP35, a doublestranded RNA (dsRNA)-binding protein that carries out multiple functions critical for virus propagation. One such function is the inhibition of signaling by RIG-I and MDA5 through (RLR) signaling, which otherwise triggers alpha/beta interferon (IFN-␣/␤) gene expression (5-13). For both EBOV VP35 (eVP35) and MARV VP35 (mVP35), point mutations that disrupt VP35 dsR-NA-binding activity also greatly impair RLR inhibition activity (5,9,14,15). In vitro studies suggest that dsRNA-binding allows eVP35 to sequester RIG-I stimulatory dsRNAs (8, 9). eVP35 also interacts with the cellular protein PACT, which binds to and facilitates activatio...

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Section: Dcs Are Significant Targets Of Filovirus Infection In Vivo mentioning

confidence: 66%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Effects of Filovirus Interferon Antagonists on Responses of Human Monocyte-Derived Dendritic Cells to RNA Virus Infection

Yen

Basler

2016

J Virol

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“…In addition to VP35's critical role in virus replication as a cofactor of the viral polymerase, it has also been extensively studied for its function in inhibition of innate signaling pathways and expression of antiviral type I interferons (IFN-I) (10,11,(14)(15)(16)(17)(18)(19)(20). VP35 also inhibits the maturation of dendritic cells (DCs) and prevents efficient adaptive immune responses (21)(22)(23)(24)(25).…”

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confidence: 99%

The Host E3-Ubiquitin Ligase TRIM6 Ubiquitinates the Ebola Virus VP35 Protein and Promotes Virus Replication

Bharaj

Atkins

Luthra

et al. 2017

J Virol

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Ebola virus (EBOV), a member of the Filoviridae family, is a highly pathogenic virus that causes severe hemorrhagic fever in humans and is responsible for epidemics throughout sub-Saharan, central, and West Africa. The EBOV genome encodes VP35, an important viral protein involved in virus replication by acting as an essential cofactor of the viral polymerase as well as a potent antagonist of the host antiviral type I interferon (IFN-I) system. By using mass spectrometry analysis and coimmunoprecipitation assays, we show here that VP35 is ubiquitinated on lysine 309 (K309), a residue located on its IFN antagonist domain. We also found that VP35 interacts with TRIM6, a member of the E3-ubiquitin ligase tripartite motif (TRIM) family. We recently reported that TRIM6 promotes the synthesis of unanchored K48-linked polyubiquitin chains, which are not covalently attached to any protein, to induce efficient antiviral IFN-I-mediated responses. Consistent with this notion, VP35 also associated noncovalently with polyubiquitin chains and inhibited TRIM6-mediated IFN-I induction. Intriguingly, we also found that TRIM6 enhances EBOV polymerase activity in a minigenome assay and TRIM6 knockout cells have reduced replication of infectious EBOV, suggesting that VP35 hijacks TRIM6 to promote EBOV replication through ubiquitination. Our work provides evidence that TRIM6 is an important host cellular factor that promotes EBOV replication, and future studies will focus on whether TRIM6 could be targeted for therapeutic intervention against EBOV infection.IMPORTANCE EBOV belongs to a family of highly pathogenic viruses that cause severe hemorrhagic fever in humans and other mammals with high mortality rates (40 to 90%). Because of its high pathogenicity and lack of licensed antivirals and vaccines, EBOV is listed as a tier 1 select-agent risk group 4 pathogen. An important mechanism for the severity of EBOV infection is its suppression of innate immune responses. The EBOV VP35 protein contributes to pathogenesis, because it serves as an essential cofactor of the viral polymerase as well as a potent antagonist of innate immunity. However, how VP35 function is regulated by host cellular factors is poorly understood. Here, we report that the host E3-ubiquitin ligase TRIM6 promotes VP35 ubiquitination and is important for efficient virus replication. Therefore, our study identifies a new host factor, TRIM6, as a potential target in the development of antiviral drugs against EBOV.KEYWORDS TRIM6, tripartite motif (TRIM) protein, VP35, viral RNA polymerase, Ebola virus, innate immunity, ubiquitination, unanchored ubiquitin, virus-host interactions

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“…This is likely to increase flexibility in this area, which may allow for binding to additional or different targets. K142E is adjacent to the human KPNA5 interface site and mutations in K142 have been shown to modulate effects on interferon signaling (Ilinykh et al, 2015). This mutation reverses the charge of the side chain and could result in local conformational changes.…”

Section: 5! Multiple Mutations In Vp24 Are Likely To Be Associated mentioning

confidence: 99%

Changes associated with Ebola virus adaptation to novel species

et al. 2017

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Motivation: Ebola viruses are not pathogenic but can be adapted to replicate and cause disease in rodents. Here, we used a structural bioinformatics approach to analyze the mutations associated with Ebola virus adaptation to rodents to elucidate the determinants of host-specific Ebola virus pathogenicity. Results: We identified 33 different mutations associated with Ebola virus adaptation to rodents in the proteins GP, NP, L, VP24, and VP35. Only VP24, GP and NP were consistently found mutated in rodent-adapted Ebola virus strains. Fewer than five mutations in these genes seem to be required for the adaptation of Ebola viruses to a new species. The role of mutations in GP and NP is not clear. However, three VP24 mutations located in the protein interface with karyopherin a5 may enable VP24 to inhibit karyopherins and subsequently the host interferon response. Three further VP24 mutations change hydrogen bonding or cause conformational changes. Hence, there is evidence that few mutations including crucial mutations in VP24 enable Ebola virus adaptation to new hosts. Since Reston virus, the only non-human pathogenic Ebolavirus species circulates in pigs in Asia, this raises concerns that few mutations may result in novel human pathogenic Ebolaviruses.

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Different Temporal Effects of Ebola Virus VP35 and VP24 Proteins on Global Gene Expression in Human Dendritic Cells

Cited by 55 publications

References 57 publications

Effects of Filovirus Interferon Antagonists on Responses of Human Monocyte-Derived Dendritic Cells to RNA Virus Infection

Effects of Filovirus Interferon Antagonists on Responses of Human Monocyte-Derived Dendritic Cells to RNA Virus Infection

The Host E3-Ubiquitin Ligase TRIM6 Ubiquitinates the Ebola Virus VP35 Protein and Promotes Virus Replication

Changes associated with Ebola virus adaptation to novel species

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