Abstact

Protease-activated receptor 2 (PAR2) is a transmembrane receptor that is irreversibly activated by proteolytic cleavage of its N-terminus via extracellular proteases, resulting in the release of the tethered ligand (TL), which binds to and activates the receptor. PAR2 plays a pivotal role in the inflammatory response and pain sensation and is a promising drug target for treating arthritis, asthma, and neuronal pain. Here, we present the cryo-electron microscopy structures of active PAR2 complexed with miniGs/q and miniG13. Combining functional assays with structural analysis, our study revealed that TL forms a parallel β-sheet with the extracellular loop 2 of PAR2 to engage the receptor. The binding of TL triggers a conformational rearrangement in the transmembrane core, releasing the inhibitory ion lock and allowing receptor activation. Furthermore, we provide structural insights into the engagement of Gq and G13 with PAR2, highlighting that a hydrophobic interaction mediated by the last methionine residue of Gα13 is crucial for G13 coupling selectivity. In combination with molecular dynamics simulations and mutagenesis, we identified the I39TL3/D62N-term interaction at the pocket side of the receptor as a key determinant of G13 signaling. Disrupting this interaction significantly inhibits G13 signaling while preserving Gq activity, enabling us to design a biased peptide ligand that selectively activates Gq signaling. The information revealed in this study provides a framework for understanding PAR2 signaling and offers a rational basis for the design of biased PAR2 ligands.