Year: 2025
Type: article
Abstract: GPR99/OXGR1 is a G protein-coupled receptor (GPCR) with two endogenous agonists, the tricarboxylic acid cycle derivative 2-oxoglutarate (α-ketoglutarate) and the inflammatory mediator cysteinyl leukotriene E4 (LTE4), hence also termed CysLT3 receptor. How GPR99/OXGR1 recognizes two distinct ligands is a biologically important question. Here we present cryo-EM structures of GPR99/OXGR1-Gq complexed with oxoglutarate and LTE4, respectively. The oxoglutarate-bound structure shows a binding pocket surrounded by the transmembrane domains (TM), with a primary site and an accessory site for simultaneous binding of two oxoglutarate molecules for full activation of the receptor. The TM binding pocket, however, is too small to accommodate the cysteinyl leukotriene LTE4. Alanine substitution of key residues for oxoglutarate binding had little impact on LTE4-induced signaling. A distinct site in between TM3/4/5 just above intracellular loop 2 was identified in the solved structure with LTE4, but the densities were less well-defined. Alanine substitution of amino acids potentially involved in LTE4 interaction at this site abrogated LTE4-induced receptor activation without affecting oxoglutarate-induced signaling. Both ligands activated GPR99/OXGR1 primarily through the Gq pathway, but LTE4 also induced Gi signaling. These findings illustrate the structural basis for GPR99/OXGR1 to interact with structurally distict oxoglutarate and LTE4. GPR99/OXGR1 is a GPCR activated by both oxoglutarate and leukotriene E4, implicated in asthma and inflammation. The authors report here the cryo-EM structures of GPR99-Gq bound to both ligands, demonstrating two distinct binding sites.
Source: Nature Communications
Authors: Aijun Liu, Yezhou Liu, Yuanzhengyang Long, Richard D. Ye
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: gold
Estimated APC paid: $6,990
Awards: G4258293004, G7549885245
OpenAlex ID: W4417524590