Enterohemorrhagic Escherichia coli (EHEC), is a foodborne pathogen, causes severe diarrhea and hemorrhagic colitis in human. Our previous study has demonstrated that EHEC infects and kills Caenorhabditis elegans. Also, C. elegans activates the
p38 MAPK innate immune pathway to defend EHEC infection. However, the C. elegans pattern recognition receptors (PRRs) for EHEC detection and innate immunity regulation remain understudied. PRRs are receptors for host to recognize pathogen- or microbe-associated molecular patterns (PAMPs/MAMPs) or damage-associated molecular patterns (DAMPs) and to activate innate immune response. Here, we aimed to identify potential CePRR for immunity against EHEC. PRRs identified in other metazoans contain several conserved domains, including the leucine-rich repeat (LRR). We therefore constructed a focused RNAi library to screen for C. elegans genes with these PRR domains. From the screening, we identified the
iglr-2 gene as a potential PRR candidate. IGLR-2 contains immunoglobulin-like (Ig-like) and LRR domains and is homologous to the E. caballus (horse) Toll-like receptor 2. We generated
iglr-2 deletion mutants by CRISPR-Cas9 technology and found that
iglr-2 mutants are more susceptible to EHEC infection compared to the parental wild-type N2 strain. Moreover, overexpression of
iglr-2 confers C. elegans resistance to EHEC. Besides, we found that the
iglr-2 transcript level is significantly up-regulated after EHEC infection. In order to identify the site of action of the
iglr-2 gene, we also created
iglr-2 transcriptional reporter strains and found that
iglr-2 is expressed in neuronal and intestinal cells. Previous study demonstrated that
iglr-2 expression pattern was co-localized with some neurons such as PVD, OLL, AFD and AWB. From our results, C. elegans lost the ability to avoid pathogens when it lost the
iglr-2 function specifically in neurons. The
iglr-2 overexpression strain, which was more resistant to EHEC infection originally, showed more susceptibility to EHEC infection upon knockdown of the
p38 MAPK cascade, but no difference upon knockdown of other immune signaling pathways. Taken all together, our data suggested that
iglr-2, a potential PRR, plays an important role in C. elegans to defend against EHEC infection by activating the pathogen-avoidance behavior and immune responses via, at least in part,
p38 MAPK pathway or other unidentified immune cascades. Key words: Enterohemorrhagic E. coli (EHEC), C. elegans, innate immunity, pattern recognition receptor (PRR),
p38 MAPK