Identification of a conserved, orphan G-protein coupled receptor required for efficient pathogen clearance in <i>C. elegans</i>

G-protein coupled receptors contribute to host defense across the animal kingdom, transducing many signals involved in both vertebrate and invertebrate immune responses. Whilst it has become well established that the nematode worm Caenorhabditis elegans triggers innate immune responses following infection with numerous bacterial, fungal and viral pathogens, the mechanisms by which C. elegans recognises these pathogens have remained somewhat more elusive. C. elegans G-protein coupled receptors have been implicated in recognising pathogen-associated damage and activating downstream host immune responses. Here we identify and characterise a novel G-protein coupled receptor required to regulate the C. elegans response to infection with Microbacterium nematophilum. We show that this receptor, which we designate PCDR-1, is required for efficient pathogen clearance following infection. PCDR-1 acts upstream of multiple G-proteins including the C. elegans Gαq ortholog EGL-30 in rectal epithelial cells to promote pathogen clearance via a novel mechanism