Innate immune chemoreceptors of 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 detection and avoidance of peptides derived from a conserved
master virulence regulator of enteric bacteria
