The long-term goal of the PI's laboratory is to better understand how Caenorhabditis elegans is able to cope with pathogens that affect animals by invading the intestine. The aim of the proposed project is to identify the mechanisms that regulate the activation of intracellular defenses to bacterial pathogens in the C. elegans intestine. Understanding how these defenses are activated is important because it is known that when they are compromised, animals are more susceptible to bacterial infection. The central hypothesis of this proposal is that C. elegans has an innate immune system that detects microbial invaders in the intestine and responds by activating immune effectors to eliminate the threat. The PI's laboratory has recently shown that the intestinal cells in response to infection activate a series of signaling pathways. The key element of this response is DAF-2, a well-studied insulin receptor ortholog. Further, DAF-2 signaling plays an essential role in the innate immunity of worms. It is still unclear, however, exactly how it is activated in response to pathogen infection. Previous studies suggest that certain cells in the intestine act as conduits and relay DAF-2 signals into the rest of the intestine. Whether these cells play a more active role in generating and/or propagating these signals is not known. In this proposal, we plan to identify the cell type that functions as a conduit and study how these cells activate DAF-2 in response to infection. These cells are thought to be similar to mammalian Paneth cells. Mammalian Paneth cells reside in the small intestine where they not only produce antimicrobials, but also act as a key component of the intestinal barrier by secreting a protective mucus layer. Thus, we believe these cells will provide an ideal model to study the mechanism of transcellular signaling of the DAF-2 signal. To identify these cells, we will create specific alleles of key signaling molecules in Paneth cell-enriched cell populations. These alleles will be used to determine whether the cell type that connects the infection sites to the rest of the intestine is indeed Paneth cells. We believe that a better understanding of how these cells activate the intestine's defenses will provide a framework for the future development of therapies to combat infectious disease. PUBLIC HEALTH RELEVANCE: Pathogens that infect animals or plants are difficult to treat because they have found ways to suppress the normal animal or plant defense mechanisms. C. elegans is an ideal model to study such pathogens because many of these pathogens can infect worms in a similar way as they do other animals and plants. Thus, through studying how worms combat infections, we will be able to better understand how other pathogens manage to infect the animals. We will also be able to use the information learned about these worms to develop new strategies to cure infections.