Interferon (IFN)-gamma is a prominent activator of pathways that effect host defense against intracellular pathogens, including many category A, B, and C biodefense priority pathogens. The Immunity-related GTPases (IRG;also known as p47 GTPases) are a family of IFN-gamma-induced proteins that play critical roles in resistance to intracellular bacteria and protozoa, including Salmonella typhimurium and Toxoplasma gondii. Mice lacking certain IRG proteins have crippled host defense against these pathogens;further, macrophages isolated from the IRG-deficient mice display defects in phagosome processing and intracellular killing, as well as in cellular motility. However, the underlying mechanisms are unknown. Based on our published and preliminary data, we hypothesize the following: Hypothesis 1. IRG proteins form complexes among themselves - both homotypic and heterotypic - that regulate phagosome processing and macrophage motility. Hypothesis 2. IRG proteins in the GMS subfamily play dominant roles as regulators of the IRG proteins in the GKS subfamily. GMS proteins complex with specific GKS proteins to prevent their degradation, enabling subsequent GKS protein assembly in homotypic complexes at sites of contact between lipid membranes and the actin cytoskeleton, impacting phagosome processing and cell motility. We will address these hypotheses with the following:
Aim 1. We will define homotypic and heterotypic IRG protein complexes that exist among specific GMS and GKS proteins in activated macrophages. We will determine the localization of the complexes, and the time frames in which they appear as related to cell motility and phagosome processing. We will determine the dependence on biochemical activity and protein domains on formation of the complexes.
Aim 2. We will define the role of IRG GMS proteins in regulating IRG GKS proteins, and in coordinating IRG protein-mediated host defense functions. We will determine the effect of GMS protein deficiency on regulating GKS protein levels. Where levels are altered, we will determine whether GMS proteins impact GKS expression at the level of transcription, translation, and/or protein stability. We will determine the effect of IRG GMS protein-deficiency on the creation of homotypic IRG GKS protein complexes on the phagosome, and on the plasma membrane at the leading edge of the migrating macrophages.

Public Health Relevance

This research will elucidate a fundamental mechanism that governs resistance to intracellular bacteria and protozoa. Our ultimate goals are the generation of broadly applicable therapeutic agents for human infectious disease and biodefense.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI057831-09
Application #
8468976
Study Section
Immunity and Host Defense Study Section (IHD)
Program Officer
Gondre-Lewis, Timothy A
Project Start
2004-03-01
Project End
2014-05-31
Budget Start
2013-06-01
Budget End
2014-05-31
Support Year
9
Fiscal Year
2013
Total Cost
$298,955
Indirect Cost
$66,305
Name
Duke University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
044387793
City
Durham
State
NC
Country
United States
Zip Code
27705
Henry, Stanley C; Schmidt, Elyse A; Fessler, Michael B et al. (2014) Palmitoylation of the immunity related GTPase, Irgm1: impact on membrane localization and ability to promote mitochondrial fission. PLoS One 9:e95021
Haldar, Arun K; Saka, Hector A; Piro, Anthony S et al. (2013) IRG and GBP host resistance factors target aberrant, "non-self" vacuoles characterized by the missing of "self" IRGM proteins. PLoS Pathog 9:e1003414
Springer, Helen M; Schramm, Michael; Taylor, Gregory A et al. (2013) Irgm1 (LRG-47), a regulator of cell-autonomous immunity, does not localize to mycobacterial or listerial phagosomes in IFN-ýý-induced mouse cells. J Immunol 191:1765-74
Liu, Bo; Gulati, Ajay S; Cantillana, Viviana et al. (2013) Irgm1-deficient mice exhibit Paneth cell abnormalities and increased susceptibility to acute intestinal inflammation. Am J Physiol Gastrointest Liver Physiol 305:G573-84
Skariah, Sini; Bednarczyk, Robert B; McIntyre, Matthew K et al. (2012) Discovery of a novel Toxoplasma gondii conoid-associated protein important for parasite resistance to reactive nitrogen intermediates. J Immunol 188:3404-15
von Bargen, Kristine; Wohlmann, Jens; Taylor, Gregory Alan et al. (2011) Nitric oxide-mediated intracellular growth restriction of pathogenic Rhodococcus equi can be prevented by iron. Infect Immun 79:2098-111
Lippmann, Juliane; Muller, Holger C; Naujoks, Jan et al. (2011) Dissection of a type I interferon pathway in controlling bacterial intracellular infection in mice. Cell Microbiol 13:1668-82
Coers, Jorn; Gondek, Dave C; Olive, Andrew J et al. (2011) Compensatory T cell responses in IRG-deficient mice prevent sustained Chlamydia trachomatis infections. PLoS Pathog 7:e1001346
Fentress, Sarah J; Behnke, Michael S; Dunay, Ildiko R et al. (2010) Phosphorylation of immunity-related GTPases by a Toxoplasma gondii-secreted kinase promotes macrophage survival and virulence. Cell Host Microbe 8:484-95
Xu, Hongwei; Wu, Zhi-Ying; Fang, Fang et al. (2010) Genetic deficiency of Irgm1 (LRG-47) suppresses induction of experimental autoimmune encephalomyelitis by promoting apoptosis of activated CD4+ T cells. FASEB J 24:1583-92

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