A Bacteroides fragilis protease activates host PAR(2) to induce intestinal pain and inflammation.

Protease-activated receptor 2 (PAR(2)) is a central regulator of intestinal barrier function, inflammation, and pain. Upregulated intestinal proteolysis and PAR(2) signaling are implicated in inflammatory bowel diseases (IBDs) and irritable bowel syndrome (IBS), conditions often associated with gut microbiome alterations. To identify potential bacterial regulators of PAR(2) activity, we developed a functional assay for PAR(2) processing to screen a library of diverse gut microbes. We identify multiple bacteria that secrete proteases capable of cleaving host PAR(2). Using chemoproteomic profiling with a covalent irreversible inhibitor, we uncovered a previously uncharacterized Bacteroides fragilis serine protease 1 (Bfp1) and show that it cleaves and activates PAR(2) in multicellular and murine models. PAR(2) cleavage by Bfp1 disrupts the intestinal barrier, sensitizes nociceptors, and triggers colonic inflammation and abdominal pain. Collectively, our findings uncover Bfp1-mediated PAR(2) processing as an axis of host-commensal interaction in the gut that has the potential to be targeted for therapeutic intervention in IBD or IBS.