Cryo-EM structures of the human G-protein coupled receptor 1 (GPR1) – Gi protein complexes bound to the full-length chemerin and to its C-terminal nonapeptide

Abstract

Chemerin is a chemoattractant and adipokine protein that acts on G protein-coupled receptors including chemokine-like receptor 1 (CMKLR1), G-protein coupled receptor 1 (GPR1) and C-C chemokine receptor-like 2 (CCRL2), mainly through its C-terminal peptide containing the sequence YFPGQFAFS (C-terminal nonapeptide or C9). Previous studies suggest that the three receptors respond to chemerin and C9 differently, with activation of the Gi signaling pathway through CMKLR1 but not GPR1 and CCRL2. Recently we reported a cryo-EM structure of human CMKLR1 in complex with Gi proteins and the C9 peptide. To identify structural differences among these receptors in ligand binding and Gi protein signaling, here we report a high-resolution cryo-EM structure of human GPR1-Gi complex bound to C9. Our structural and functional results show that GPR1 is able to respond to the C9 peptide with activation of the Gi signaling pathway and forms complex with a Gi protein. Similar to the CMKLR1-C9 structure, C9 adopts a C-terminus-in and S-shaped pose in the binding pocket. C9 is stabilized through hydrophobic interactions involving its Y1, F2, Q5, F6 and F8, and polar interactions between the P3, G4, Q5, F6, F8, S9 and residues lining the GPR1 binding pocket. An analysis of the GPR1-Gi protein interface found high similarities to the CMKLR1-Gi complex, and site-directed mutagenesis with functional verifications support GPR1 as a Gi-coupling receptors. These findings provide a structural basis of ligand recognition and Gi protein coupling by GPR1, and may help to understand the respective functions of the three chemerin receptors.

Structural insights into agonist binding and activation of succinate receptor 1

“…The model building was facilitated by the previous structure of PDB code 6IBB (Haffke et al, 2019) and 8JJP (Liu et al, 2023), as a starting template for SUCNR1 and G protein respectively. The model was manually adjusted and built by Coot (Emsley et al, 2010), as well as iterative real-space refinement in Phenix (Liebschner et al, 2019).…”