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ZFIN ID: ZDB-PUB-161209-1
Structural Mapping and Functional Characterization of Zebrafish Class B G-Protein Coupled Receptor (GPCR) with Dual Ligand Selectivity towards GLP-1 and Glucagon
Oren, D.A., Wei, Y., Skrabanek, L., Chow, B.K., Mommsen, T., Mojsov, S.
Date: 2016
Source: PLoS One 11: e0167718 (Journal)
Registered Authors:
Keywords: Glucagon, Zebrafish, Crystal structure, Hydrogen bonding, G protein coupled receptors, Intracellular receptors, Protein sequencing, Sequence alignment
MeSH Terms:
  • Amino Acid Sequence
  • Animals
  • Glucagon/metabolism*
  • Glucagon-Like Peptide 1/metabolism*
  • Ligands
  • Receptors, G-Protein-Coupled/chemistry
  • Receptors, G-Protein-Coupled/metabolism*
  • Sequence Homology, Amino Acid
  • Zebrafish/metabolism*
PubMed: 27930690 Full text @ PLoS One
GLP-1 and glucagon regulate glucose metabolism through a network of metabolic pathways initiated upon binding to their specific receptors that belong to class B G-protein coupled receptors (GPCRs). The therapeutic potential of glucagon is currently being evaluated, while GLP-1 is already used in the treatment of type 2 diabetes and obesity. Development of a second generation of GLP-1 based therapeutics depends on a molecular and structural understanding of the interactions between the GLP-1 receptor (GLP-1R) and its ligand GLP-1. There is considerable sequence conservation between GLP-1 and glucagon and between the hGLP-1R and human glucagon receptor (hGCGR), yet each receptor recognizes only its own specific ligand. Glucagon receptors in fish and frogs also exhibit ligand selectivity only towards glucagon and not GLP-1. Based on competitive binding experiments and assays of increase in intracellular cAMP, we demonstrate here that a GPCR in zebrafish (Danio rerio) exhibits dual ligand selectivity towards GLP-1 and glucagon, a characteristic not found in mammals. Further, many structural features found in hGLP-1R and hGCGR are also found in this zebrafish GPCR (zfGPCR). We show this by mapping of its sequence and structural features onto the hGLP-1R and hGCGR based on their partial and complementary crystal structures. Thus, we propose that zfGPCR represents a dual GLP-1R/GCGR. The main differences between the three receptors are in their stalk regions that connect their N-terminal extracellular domains (NECDs) with their transmembrane domains and the absence of loop 3 in the NECD in zfGLP-1R/GCGR. These observations suggest that the interactions between GLP-1 and glucagon with loop 3 and the stalk regions may induce different conformational changes in hGLP-1R and hGCGR upon ligand binding and activation that lead to selective recognition of their native ligands.