Molecular basis of lipid and ligand regulation of prostaglandin receptor DP2

Prostaglandin D2 receptor 2 (DP2) is an important anti-inflammatory and antiallergic drug target. While inactive DP2 structures are known, its activation mechanisms and biased signaling remain unclear. Here, we report cryo-EM structures of an apo DP2-Gi complex, a DP2-Gi complex bound to the endogenous ligand Prostaglandin D₂ (PGD₂), and a DP2-Gi complex bound to indomethacin, an arrestin-biased ligand, at resolutions of 2.5 Å, 2.8Å, and 2.3 Å, respectively. These structures reveal a distinct binding pose of PGD₂ and indomethacin and provide key insights into receptor activation and transducer coupling. Combining the structural data with functional studies, we uncover the molecular basis for biased signaling of indomethacin toward β-arrestin over G proteins. Notably, a phospholipid binding site was identified at the DP2-G protein interface that modulates DP2-G protein interactions. Together, our functional and structural findings provide insights into DP2 activation, biased signaling, drug interactions, and lipid regulation, enabling rational design of safer antiallergy therapeutics targeting this key immune receptor.