Poster Presentation The 47th Lorne Conference on Protein Structure and Function 2022

Structural characterisation of peptide activated class A G protein coupled receptors (#211)

Jesse I Mobbs 1 , Matthew J Belousoff 1 , Kaleeckal G Harikumar 2 , Hari Venugopal 3 , Sarah J Piper 1 , Xiaomeng Xu 1 , Sebastian Furness 1 , Alisa Glukhova 4 , Radostin Danev 5 , Denise Wootten 1 , Laurence J Miller 2 , Patrick M Sexton 1 , David M Thal 1
  1. Monash Institute of Pharmaceutical Sciences, Parkville, VIC, Australia
  2. Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, Arizona, United states
  3. Ramaciotti Centre for Cryo-Electron Microscopy , Monash University, Clayton, Victoria, Australia
  4. Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
  5. Graduate School of Medicine, University of Tokyo, Tokyo, Japan

Many class A G protein coupled receptors (GPCRs) are regulated by a variety of endogenous peptides and control a wide range of physiological processes. Class A peptide GPCRs are therefore considered as potential therapeutic targets for a wide variety of human conditions, such as diabetes and cancer. To develop better and safer therapeutics, the molecular mechanisms that govern receptor activation must be further understood.

One such class A peptide receptor is the cholecystokinin type 1 receptor (CCK1R) which is activated by the endogenous peptide ligand cholecystokinin (CCK). CCK1R has a wide range of roles in metabolism; including gastric motility, gallbladder contraction, and satiety. For these roles in metabolism the CCK1R is an attractive candidate for treating metabolic disorders such as obesity. Here, we used cryo-electron microscopy (cryo-EM) to determine structures of CCK1R bound to the CCK peptide agonist, CCK-8 and 2 distinct transducer proteins, its primary transducer Gq, and the more weakly coupled Gs. As seen with other Gq/11–GPCR complexes, the Gq–α5 helix (αH5) bound to a relatively narrow pocket in the CCK1R core. Surprisingly, the backbone of the CCK1R and volume of the G protein binding pocket were essentially equivalent when Gs was bound, with the Gs αH5 displaying a conformation that arises from “unwinding” of the far carboxyl-terminal residues, compared to canonically Gs coupled receptors. Thus, integrated changes in the conformations of both the receptor and G protein are likely to play critical roles in the promiscuous coupling of individual GPCRs.

Using methods developed for the structures of CCK1R, we have set out to determine the active state structure of the delta opioid receptor (DOR) an important target for chronic pain. Altogether these results will further our understanding of the intricacies of activation of class A peptide activated receptors.