Molecular mechanism underlying non-discriminatory recognition of relaxin-3 by RXFP3 and RXFP4
Abstract The human relaxin family peptide receptors RXFP3 and RXFP4 play important physiological roles through interactions with endogenous hormones, relaxin-3 and insulin-like peptide 5 (INSL5). They are implicated in certain neurological and metabolic disorders. While INSL5 only activates RXFP4, r...
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| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Nature Portfolio
2025-05-01
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| Series: | Communications Biology |
| Online Access: | https://doi.org/10.1038/s42003-025-08220-7 |
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| Summary: | Abstract The human relaxin family peptide receptors RXFP3 and RXFP4 play important physiological roles through interactions with endogenous hormones, relaxin-3 and insulin-like peptide 5 (INSL5). They are implicated in certain neurological and metabolic disorders. While INSL5 only activates RXFP4, relaxin-3 is recognized by both receptors. Here, we report the cryo-electron microscopy structures of RXFP3–Gi complexes bound by relaxin-3 or a small-molecule dual agonist (compound 4), and relaxin-3 in complex with RXFP4–Gi, with global resolutions of 2.91 Å, 2.95 Å, and 3.10 Å, respectively. It is found that relaxin-3 adopts a conserved binding conformation within the transmembrane domain (TMD) bundle of RXFP3 and RXFP4, where the C-terminal tip residues of its B chain, R26 and W27, make extensive contacts with conserved receptor residues, thereby activating RXFP3 and RXFP4. Compound 4 mimics these key interactions by binding to both receptors. In contrast, the C-terminal residues composition and TMD-binding angle of INSL5 in RXFP4 differ significantly from that of relaxin-3, ensuring its selectivity for RXFP4. These findings deepen our understanding about the structural basis of ligand recognition and selectivity in this G protein-coupled receptor subfamily. |
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| ISSN: | 2399-3642 |