The death domain containing serine/threonine kinase Ripk1 is the core component of TNF-induced signaling complexes mediating NF?B and MAP kinase activation, apoptosis and an alternative form of caspase independent cell death called necroptosis. In unbiased genome wide siRNA screens for regulators of necroptosis, Ripk1, its deubiquitinase Cyld, the related Ripk3 as well as other proteins belonging to the interferon and Toll-like receptor signaling systems were identified. These studies and those using an allosteric Ripk1 kinase inhibitor or Ripk3-deficient mice establish necroptosis as a prominent host defense against viral infection. Necroptosis requires the kinase activities of Ripk1 and Ripk3 but precisely how Rip kinases initiate and execute necroptotic cell death is unknown. We have shown that Ripk1 has additional signaling functions beyond TNF, in nucleic acid sensing pathways mediated by TLR3 and Rig-I. Our preliminary studies additionally implicate Ripk1 in a cytosolic DNA sensing pathway involving Sting, Tbk1 and Irf3. Collectively, these studies predict a central role for Ripk1 in innate anti-viral immunity, however the perinatal lethality associated with a Ripk1-deficiency has precluded in vivo analyses. Goals of the current proposal are to test a requirement for Ripk1 in the anti-viral innate immune response using the conditional Ripk1 mice we have generated. We have also introduced a mutation into the Ripk1 locus that impairs the kinase activity of Ripk1. Our preliminary studies in Ripk1 kinase inactive MEFs and macrophages find these cells protected from TNF- and TLR3-induced necroptosis, respectively. An additional objective of this proposal is to examine the contribution of viral-initiated necroptosis to host defense in these newly engineered Ripk1 kinase inactive mice. In addition to virus-induced injury and inflammation, Rip kinases respond to non-microbial signals called danger-associated molecular patterns (DAMPs) released upon tissue injury. The long-term goal of these studies is to selectively inhibit Rip kinases in sterile inflammation without impairing innate immunity.

Public Health Relevance

This proposal examines the role of the serine/threonine kinase Ripk1 in host defense to viral infection. The kinase activity of Ripk1 is required for a for of cell death called necroptosis, used by the host to limit viral replication and activate immune cells. We plan to infect the new mouse Ripk1 models we have generated with RNA and DNA viruses and analyze viral replication, cytokine production and adaptive immune responses.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
2R01AI075118-06
Application #
8631696
Study Section
Immunity and Host Defense Study Section (IHD)
Program Officer
Palker, Thomas J
Project Start
2007-09-21
Project End
2018-11-30
Budget Start
2013-12-01
Budget End
2014-11-30
Support Year
6
Fiscal Year
2014
Total Cost
$375,562
Indirect Cost
$150,562
Name
University of Massachusetts Medical School Worcester
Department
Biology
Type
Schools of Medicine
DUNS #
603847393
City
Worcester
State
MA
Country
United States
Zip Code
01655
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Ito, Yasushi; Ofengeim, Dimitry; Najafov, Ayaz et al. (2016) RIPK1 mediates axonal degeneration by promoting inflammation and necroptosis in ALS. Science 353:603-8
Legarda, Diana; Justus, Scott J; Ang, Rosalind L et al. (2016) CYLD Proteolysis Protects Macrophages from TNF-Mediated Auto-necroptosis Induced by LPS and Licensed by Type I IFN. Cell Rep 15:2449-61
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Weng, Dan; Marty-Roix, Robyn; Ganesan, Sandhya et al. (2014) Caspase-8 and RIP kinases regulate bacteria-induced innate immune responses and cell death. Proc Natl Acad Sci U S A 111:7391-6
Mavrogiorgos, Nikolaos; Mekasha, Samrawit; Yang, Yibin et al. (2014) Activation of NOD receptors by Neisseria gonorrhoeae modulates the innate immune response. Innate Immun 20:377-89
Roderick, Justine E; Hermance, Nicole; Zelic, Matija et al. (2014) Hematopoietic RIPK1 deficiency results in bone marrow failure caused by apoptosis and RIPK3-mediated necroptosis. Proc Natl Acad Sci U S A 111:14436-41
Dannappel, Marius; Vlantis, Katerina; Kumari, Snehlata et al. (2014) RIPK1 maintains epithelial homeostasis by inhibiting apoptosis and necroptosis. Nature 513:90-4

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