Functional elements of the gastric inhibitory polypeptide receptor: Comparison between secretin- and rhodopsin-like G protein-coupled receptors

Arnau Cordomí, Sadek Ismail, Minos Timotheos Matsoukas, Chantal Escrieut, Marie Julie Gherardi, Leonardo Pardo, Daniel Fourmy

Research output: Contribution to journalArticleResearchpeer-review

14 Citations (Scopus)

Abstract

© 2015 Elsevier Inc. Abstract Innovative crystallographic techniques have resulted in an exponential growth in the number of solved G-protein coupled receptor (GPCR) structures and a better understanding of the mechanisms of class A receptor activation and G protein binding. The recent release of the type 1 receptor for the corticotropin-releasing factor and the glucagon receptor structures, two members of the secretin-like family, gives the opportunity to understand these mechanisms of activation in this family of GPCRs. Here, we addressed the comparison of the functional elements of class A and secretin-like GPCRs, using the glucose-dependent insulinotropic polypeptide receptor (GIPR) as a model receptor. Inactive and active models of GIPR permitted to select, by structural homology with class A GPCRs, several residues that may form key interactions presumably involved in receptor activation and Gs coupling, for pharmacological evaluation. Mutants on these amino acids were expressed in HEKT 293 cells and characterized in terms of GIP-induced cAMP production. We identified various functional domains spanning from the peptide-binding to the G protein pockets: including: a network linking the extracellular part of transmembrane (TM) 6 with TMs 2 and 7; a polar lock that resembles the ionic-lock in class A GPCRs; an interaction between TMs 3 and 7 that favors activation; and two clusters of polar/charged and of hydrophobic residues that interact with the C-terminus of the Gα. The results show that despite the low degree of sequence similarity between rhodopsin- and secretin-like GPCRs, the two families share conserved elements in their mechanisms of activation and G protein binding.
Original languageEnglish
Article number12255
Pages (from-to)237-246
JournalBiochemical Pharmacology
Volume96
Issue number3
DOIs
Publication statusPublished - 6 Jul 2015

Keywords

  • G protein
  • G protein-coupled receptor (GPCR)
  • Gastric glucose-dependent insulinotropic polypeptide receptor (GIPR)
  • Homology modeling
  • Molecular modeling
  • Secretin-like receptor
  • Site-directed mutagenesis

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