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

Agonist-bound GPR52 G protein complex structures solved by cryo-EM (#133)

Yao Lu 1 2 , Rachel Johnson 1 2 , Matthew Belousoff 1 2 , Radostin Danev 3 , Patrick Sexton 1 2 , Denise Wootten 1 2 , Christopher Langmead 1 2 , Gregory Stewart 1 2
  1. Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia
  2. ARC Centre for Cryo-electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia
  3. Graduate School of Medicine, University of Tokyo, Tokyo, Japan

Schizophrenia is characterised as a chronic, heterogeneous psychiatric disorder with symptoms that include hallucinations, social withdrawal and cognitive deficits1. While current antipsychotic drugs are effective at targeting some symptoms such as hallucinations, the cognitive deficits are left untreated2. GPR52 is an orphan GPCR that is almost exclusively expressed in the brain, particularly the striatal region and has emerged as a potential target for schizophrenia3.

 

Various potent small molecule agonists have emerged that allow biological and pharmacological characterisation of GPR52. Preclinical studies have demonstrated the first potent GPR52 agonist 3-BTBZ (also called 7m) has antipsychotic activity4.  FTMBT is another GPR52 agonist with similar potency, but has improved oral availability compared to 3-BTBZ and shows pro-cognitive activity in psychostimulant-treated mice5. While exploring the cellular mechanisms in mouse brain slices, FTBMT induced DARPP-32 phosphorylation at T34 residue, which is a downstream effect of cAMP5. In contrast, this was not observed for 3-BTBZ6. Due to notable differences in the chemical structures and physicochemical properties, it is possible that 3-BTBZ and FTBMT engage differently with GPR52 in the binding pocket, leading to differential activation of the receptor and the downstream signalling in its native tissue environment.

 

With the development of cryo-electron microscopy (cryo-EM) imaging, high-resolution GPCR complex structures have become more attainable, enabling structure-guided design of novel ligands based on the structure-revealed binding pocket in the receptor. To understand the molecular nuances of agonist/GPR52 binding we use cryo-EM to map the GPR52 binding pocket using an N-terminal FLAG tagged GPR52 with full-length G protein heterotrimers. In this study, GPR52 Gαs complex structures bound to 3-BTBZ and FTBMT were solved using cryo-EM. This will not only enhance our understanding of the relationships that underpin GPR52 agonist binding and signalling, but also aid novel compound development for GPR52.