Click here to close
Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly.
We suggest using a current version of Chrome,
FireFox, or Safari.
???displayArticle.abstract???
Gonadotropin-releasing hormone receptor (GnRHR) is critical for reproductive health and a key therapeutic target for endocrine disorders and hormone-responsive cancers. Using high-resolution cryoelectron microscopy, we determined the structures of Sus scrofa and Xenopus laevis GnRHRs bound to mammal GnRH, uncovering conserved and species-specific mechanisms of receptor activation and G protein coupling. The conserved "U"-shaped GnRH conformation mediates high-affinity binding through key interactions with residues such as K3.32, Y6.51, and Y6.52. Species-specific variations in extracellular loops and receptor-ligand contacts fine-tune receptor function, while ligand binding induces structural rearrangements, including N terminus displacement and TM6 rotation, critical for signaling. Structure-activity relationship analysis demonstrates how D-amino acid substitutions in GnRH analogs enhance stability and receptor affinity. Distinct binding modes of agonists and antagonists elucidate mechanisms of ligand-dependent activation and inactivation. These insights lay the groundwork for designing next-generation GnRHR therapeutics with enhanced specificity and efficacy for conditions like endometriosis, prostate cancer, and infertility.
Fig. 1. Structure features of fGnRHR and pGnRHRs bound to GnRH. (A and B) Orthogonal views of the cryo-EM density map and the corresponding atomic model of the GnRH–fGnRHR–miniGq complex. (C and D) Orthogonal views of the cryo-EM density map and the corresponding atomic model of the GnRH–pGnRHR–miniGq complex. (E) Structural differences between ICL2 and ECLs of fGnRHRs and pGnRHRs. fGnRHR is shown in blue and pGnRHR is shown in purple.
Fig. 2. The conserved binding pocket of GnRHs across GnRHRs. (A) The U-shaped conformation of GnRH within the binding pocket of GnRHRs. (B and C) Side view of similar binding modes of GnRH in fGnRHRs and pGnRHRs. Cryo-EM density maps of GnRH are shown in salmon and green, relatively. (D and E) Conserved interactions in the binding pocket across different GnRHRs. (F) The bar plot of ΔpEC50 of important residues in the binding pocket of hGnRHR. ΔpEC50 = pEC50 of GnRH to a specific mutant GnRHR–pEC50 of GnRH to WT GnRHR, which are all measured using IP1 accumulation assays. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001. Data were shown as mean ± SEM from three independent experiments, which were performed in triplicates; significance was determined with one-way ANOVA. N.A., no active receptors; dashed-border rectangles, inapplicable pEC50 of mutations causing significant reduction of ligand potency that were not able to be calculated. (G) 2D illustration of GnRH in the conserved binding pockets and corresponding interactions. (H and I) Species–specific interactions in the pockets of fGnRHRs and pGnRHRs, respectively. Side chains of residues are displayed in sticks. Hydrogen bonds are depicted as black dashed lines.
Fig. 3. Activation mechanism of GnRHR. (A) Structural superposition of active GnRHRs and the inactive hGnRHR (PDB: 7BR3) from the side view. (B) Different modes of N terminus of inactive human and active pGnRHRs. The N terminus of inactive hGnRHR is highlighted in red. The movement directions of the N terminus is highlighted as a black arrow. (C) Top and cytoplasmic views of active GnRHRs and the inactive GnRHR. The movement directions of TMs of active GnRHRs relative to those of inactive GnRHR are highlighted as red arrows. The distances of the movements are measured by pig and hGnRHRs. (D) The insertion of the N-terminal segment of GnRH is deeper into the TMD core than the C terminus. (E) Activation of GnRHRs induced by the His2 of GnRH. (F–H) Conformational changes of the microswitches upon GnRHR activation such as DRS (F), PAF (G), and DPxxY (H) motifs. The rotation directions of residue side chains upon pGnRHR activation compared with the antagonist-bound hGnRHR are indicated by black arrows.
Fig. 4. SAR of GnRHR ligands. (A and B) 2D and 3D illustrations of engineered agonists of GnRHR with the sixth glycine substituted with D-type amino acids, along with a C-terminal modification. (C) Extra interactions formed by the side chain of the substituted D-type amino acids with N terminus, TM5-7, ECL2, or ECL3 of the pGnRHR by modeling. (D) Representative docking poses of GnRHR antagonists in the binding pocket of hGnRHR. (E) SAR principles of GnRHR ligands. The rotation of important residues upon activation compared with the inactive GnRHR are indicated by black arrows.
Fig. 5. Gq protein coupling by GnRHRs. (A) Deviation of α5 and αN helix of Gq protein in assembly with different GnRHRs. (B and C) Conserved interaction of hydrophilic and hydrophobic interactions between GnRHRs and Gq protein. (D and E) Species-specific interactions of pig (D) and frog (E) GnRHRs and Gq protein. (F) The hydrophobic and hydrophilic interfaces formed by ICL2 of GnRHRs and the αN helix of Gαq. Side chains of residues are displayed in sticks. Hydrogen bonds are depicted as black dashed lines.
