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 #
2R01AI057831-06A1
Application #
7879195
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
2010-06-01
Budget End
2011-05-31
Support Year
6
Fiscal Year
2010
Total Cost
$310,135
Indirect Cost
Name
Duke University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
044387793
City
Durham
State
NC
Country
United States
Zip Code
27705
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Schmidt, Elyse A; Fee, Brian E; Henry, Stanley C et al. (2017) Metabolic Alterations Contribute to Enhanced Inflammatory Cytokine Production in Irgm1-deficient Macrophages. J Biol Chem 292:4651-4662
Pilla-Moffett, Danielle; Barber, Matthew F; Taylor, Gregory A et al. (2016) Interferon-Inducible GTPases in Host Resistance, Inflammation and Disease. J Mol Biol 428:3495-513
Murray, Henry W; Mitchell-Flack, Marisa; Taylor, Gregory A et al. (2015) IFN-?-induced macrophage antileishmanial mechanisms in mice: A role for immunity-related GTPases, Irgm1 and Irgm3, in Leishmania donovani infection in the liver. Exp Parasitol 157:103-9
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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
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
Liu, Zhen; Zhang, Huifang M; Yuan, Ji et al. (2012) The immunity-related GTPase Irgm3 relieves endoplasmic reticulum stress response during coxsackievirus B3 infection via a PI3K/Akt dependent pathway. Cell Microbiol 14:133-46

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