The interferons (IFNs) are powerful anti-viral cytokines that can limit virus replication by directly triggering the death of infected cells. We have recently reported the identification of a new pathway of programmed necrosis activated by IFNs, but how this pathway is regulated during antiviral innate-immune responses remains unclear. In this proposal, we outline the discovery of a putative new checkpoint that specifically licenses the necrotic cell death of virus-infected cells by IFNs. The goal of this proposal is to identify how this checkpoint is regulated, and what its role is during acute RNA virus infections in vivo. We have found that IFNs activate RIP1/RIP3 kinase-mediated necrosis only when the adaptor protein FADD is disabled. In uninfected cells, FADD sequesters RIP1 to block necrosis, but upon an acute RNA virus infection, FADD becomes phosphorylated on a conserved serine (S191 in mice or S194 in humans) and can no longer inhibit RIP1. Under these circumstances, IFNs activate RIP kinases and induce necrosis. These findings represent the first complete outline of an IFN-activated necrosis pathway and identify phosphorylation of FADD as a putative new innate-immune cell-fate checkpoint. In the first Aim of this proposal, we will identify how FADD is phosphorylated during virus infections, and how this event licenses IFN-activated necrosis. In the second Aim, we will use a unique mouse model in which FADD cannot be phosphorylated to identify the role of IFN- triggered necrotic death during acute respiratory infection by RNA viruses (including influenza A). The successful completion of these experiments stands to define a new arm of the IFN antiviral response.

Public Health Relevance

Our data suggest that IFN-activated necrosis may represent a major host defense mechanism that responds to pulmonary RNA virus infections (such as influenza A and the SARS coronavirus). Considering the pandemic potential of these and other RNA viruses, understanding the mechanisms by which IFN-activated necrosis is controlled represents an important public health objective. Our proposal outlines experiments that will help elucidate the regulation and significance of IFN-induced necrosis; the successful completion of these experiments has potentially-important implications for antiviral therapeutic strategies and vaccines.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Exploratory/Developmental Grants (R21)
Project #
5R21AI113469-02
Application #
8856491
Study Section
Immunity and Host Defense (IHD)
Program Officer
Singleton, Kentner L
Project Start
2014-06-01
Project End
2016-05-31
Budget Start
2015-06-01
Budget End
2016-05-31
Support Year
2
Fiscal Year
2015
Total Cost
Indirect Cost
Name
Research Institute of Fox Chase Cancer Center
Department
Type
DUNS #
064367329
City
Philadelphia
State
PA
Country
United States
Zip Code
19111
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Ingram, Justin P; Brodsky, Igor E; Balachandran, Siddharth (2017) Interferon-? in Salmonella pathogenesis: New tricks for an old dog. Cytokine 98:27-32
Nogusa, Shoko; Thapa, Roshan J; Dillon, Christopher P et al. (2016) RIPK3 Activates Parallel Pathways of MLKL-Driven Necroptosis and FADD-Mediated Apoptosis to Protect against Influenza A Virus. Cell Host Microbe 20:13-24
Nogusa, Shoko; Slifker, Michael J; Ingram, Justin P et al. (2016) RIPK3 Is Largely Dispensable for RIG-I-Like Receptor- and Type I Interferon-Driven Transcriptional Responses to Influenza A Virus in Murine Fibroblasts. PLoS One 11:e0158774
Thapa, Roshan J; Ingram, Justin P; Ragan, Katherine B et al. (2016) DAI Senses Influenza A Virus Genomic RNA and Activates RIPK3-Dependent Cell Death. Cell Host Microbe 20:674-681
Najjar, Malek; Suebsuwong, Chalada; Ray, Soumya S et al. (2015) Structure guided design of potent and selective ponatinib-based hybrid inhibitors for RIPK1. Cell Rep 10:1850-60