Pharmacological modulation of GPR84 revealed by dual states structures and immune functional assays

Abstract

G-protein-coupled receptor 84 (GPR84) is an orphan class A GPCR selectively activated by medium chain fatty acids and highly expressed in immune cells, where it modulates pro-inflammatory signaling. The structural basis of GPR84 inactivation and antagonism has remained unclear, limiting the rational design of pathway-selective modulators despite its clinical relevance in metabolic inflammation and fibrotic diseases. Here, we report cryo-electron microscopy structures of human GPR84 in inactive and active states. The 3.5 Å inactive structure bound to the antagonist GLPG1205 reveals a lid-like conformation of extracellular loop 2 and an inward reorientation of Arg172, with the antagonist head group blocking the allosteric sodium-binding site. Molecular dynamics simulations further support these findings, identifying an aberrant TM5, TM6 lateral entry gate. By contrast, the 3.17 Å agonist ZQ-16, Gαi complex, shows a rearranged toggle switch and comparative analyses highlight extracellular loop 2 conformational plasticity. Immune functional assays in THP-1 cells demonstrated that ZQ-16 elicited GPR84-dependent activation and cytokine production, which were effectively abrogated by GLPG1205. Mutagenesis combined with functional assays validates key ligand interactions, providing a framework for the rational design of pathway selective GPR84 modulators. G protein-coupled receptor 84 (GPR84) is a receptor primarily found in immune cells and is involved in metabolic and immune responses. This study addresses the challenge of understanding GPR84’s ligand specificity and signaling pathways, which are crucial for its role in diseases such as inflammation and cancer. Researchers used cryo-electron microscopy to capture the structures of GPR84 in both active and inactive states, bound to the agonist ZQ-16 and antagonist GLPG1205, respectively. These structures revealed how different ligands interact with GPR84, influencing its signaling pathways. The active state showed how ZQ-16 promotes pro-inflammatory responses, whereas the inactive state demonstrated how GLPG1205 inhibits these pathways. These findings provide a structural basis for designing selective modulators of GPR84, which could lead to new therapeutic strategies for diseases involving immune responses. Future research could explore endogenous ligands and diverse signaling mechanisms across cell types. This summary was initially drafted using artificial intelligence, then revised and fact-checked by the author.