Infectious diseases impose a significant burden on human health, with epithelial cells on the front lines of attack by disease-causing microbes that can invade and replicate inside of these cells. In addition to diseases such as diarrhea and pneumonia caused by pathogens, inappropriate activation of defense pathways in epithelial cells can lead to inflammatory disease. Therefore, it is critical learn more about epithelial defense against intracellular pathogens. In particular, little is known about defense against the Microsporidia phylum of fungal-related intracellular parasites, 14 of which can infect and cause disease in humans, most commonly infecting intestinal epithelial cells. We have developed a convenient whole-animal model for studying defense against microsporidia through characterization of natural intestinal infection in the nematode C. elegans. Our long-term goal is to dissect the mechanisms by which epithelial cells defend against co-evolved intracellular pathogens like microsporidia. Closing this gap in our understanding will provide new insights for treating infectious disease and inflammatory disorders. Our central hypothesis is that attack from co-evolved pathogens causes expansion and diversification of host genes to become ?species-specific? although these genes may control conserved immune pathways. The objective here is to characterize the species-specific pals gene family, which expanded to 39 pals genes in C. elegans, whereas there is only one pals gene in humans. Virtually nothing is known about PALS protein structure or biochemical function in any system, although they have been connected to ubiquitin ligases through sequence analysis and genetic studies in C. elegans. We found PALS-22 and PALS-25 to be key regulators of a common transcriptional response to natural microsporidia and viral infections in C. elegans that we call the Intracellular Pathogen Response or IPR. The IPR appears to define an entire physiological program and our forward genetic screens identified PALS-22 as a negative regulator and PALS-25 as a positive regulator of the IPR. Loss of PALS-22 leads to enhanced immunity against intracellular pathogens, increased RNA interference, as well as fitness consequences such as delayed development, all of which depend on PALS-25.
In Specific Aim 1 we will characterize the relationship between gene expression and immune responses regulated by PALS-22 and PALS-25, identify the tissues where they act, and define the stage of microsporidia they target.
In Specific Aim 2 we will recombinantly express PALS-22 and PALS-25 proteins to characterize their interaction, as well as their structure using X-ray crystallography and cryo EM.
In Specific Aim 3 we will analyze the role of other PALS proteins, RNAi machinery and identify new regulators of the IPR. The approach is innovative as it focuses on uncharacterized proteins that regulate a novel form of epithelial immunity. The proposed research is significant, because it could lead to new treatments for infectious diseases and inflammatory disorders.

Public Health Relevance

The proposed research is relevant to public health because it will characterize a novel form of immune defense against intracellular pathogens in intestinal epithelial cells. By describing how these cells can defend against viruses and microsporidia we may learn about new ways to manage and treat infectious diseases, as well as inflammatory disorders. Thus, the proposed research is relevant to the NIH?s mission to seek fundamental knowledge about living systems in order to reduce the burden of disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM114139-06
Application #
9985884
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Zhao, Xiaoli
Project Start
2015-08-01
Project End
2023-07-31
Budget Start
2020-08-01
Budget End
2021-07-31
Support Year
6
Fiscal Year
2020
Total Cost
Indirect Cost
Name
University of California, San Diego
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
804355790
City
La Jolla
State
CA
Country
United States
Zip Code
92093
Troemel, Emily (2018) Host-parasite interactions: an interview with Emily Troemel. BMC Biol 16:133
Kuo, Cheng-Ju; Hansen, Malene; Troemel, Emily (2018) Autophagy and innate immunity: Insights from invertebrate model organisms. Autophagy 14:233-242
Reddy, Kirthi C; Dror, Tal; Sowa, Jessica N et al. (2017) An Intracellular Pathogen Response Pathway Promotes Proteostasis in C. elegans. Curr Biol 27:3544-3553.e5
Reinke, Aaron W; Mak, Raymond; Troemel, Emily R et al. (2017) In vivo mapping of tissue- and subcellular-specific proteomes in Caenorhabditis elegans. Sci Adv 3:e1602426
Reinke, Aaron W; Balla, Keir M; Bennett, Eric J et al. (2017) Identification of microsporidia host-exposed proteins reveals a repertoire of rapidly evolving proteins. Nat Commun 8:14023
Balla, Keir M; Luallen, Robert J; Bakowski, Malina A et al. (2016) Cell-to-cell spread of microsporidia causes Caenorhabditis elegans organs to form syncytia. Nat Microbiol 1:16144
Botts, Michael R; Cohen, Lianne B; Probert, Christopher S et al. (2016) Microsporidia Intracellular Development Relies on Myc Interaction Network Transcription Factors in the Host. G3 (Bethesda) 6:2707-16
Reddy, Kirthi C; Dunbar, Tiffany L; Nargund, Amrita M et al. (2016) The C. elegans CCAAT-Enhancer-Binding Protein Gamma Is Required for Surveillance Immunity. Cell Rep 14:1581-1589
Stentiford, G D; Becnel, -J J; Weiss, L M et al. (2016) Microsporidia - Emergent Pathogens in the Global Food Chain. Trends Parasitol 32:336-348
Zhang, Gaotian; Sachse, Martin; Prevost, Marie-Christine et al. (2016) A Large Collection of Novel Nematode-Infecting Microsporidia and Their Diverse Interactions with Caenorhabditis elegans and Other Related Nematodes. PLoS Pathog 12:e1006093

Showing the most recent 10 out of 16 publications