Bacterial MgrB peptide activates chemoreceptor Fpr3 in mouse accessory olfactory system and drives avoidance behaviour

Innate immune chemoreceptorsof the formyl peptide receptor(Fpr) family are expressed by vomeronasal sensory neurons(VSNs) in the accessory olfactory system. Their biological function and coding mechanisms remain unknown. We show that mouse Fpr3 (Fpr-rs1) recognizes the core peptide motif f-MKKFRW that is predominantly present in the signal sequence of the bacterial protein MgrB, a highly conserved regulator of virulence and antibiotic resistance in Enterobacteriaceae. MgrB peptide can be produced and secreted by bacteria, and is selectively recognized by a subset of VSNs. Exposure to the peptide also stimulates VSNs in freely behaving mice and drives innate avoidance. Our data shows that Fpr3 is required for neuronal detectionand avoidanceof peptides derived from a conserved master virulence regulator of enteric bacteria. The role of chemoreceptorson vomeronasal neurons are not fully understood. Here the authors show that in mice, the vomeronasal chemoreceptorFpr3 responds to peptides from the bacterial MgrB protein, and that exposure to these peptides drives an avoidance response.