COR758, a negative allosteric modulator of GABAB receptors

Alessandra Porcu; Rafaela Mostallino; Valeria Serra; Miriam Melis; Valeria Sogos; Sarah Beggiato; Luca Ferraro; Fabrizio Manetti; Beatrice Gianibbi; Bernhard Bettler; Federico Corelli; Claudia Mugnaini; M Paola Castelli

doi:10.1016/j.neuropharm.2021.108537

COR758, a negative allosteric modulator of GABA_B receptors

Neuropharmacology. 2021 May 15:189:108537. doi: 10.1016/j.neuropharm.2021.108537. Epub 2021 Mar 30.

Authors

Affiliations

¹ Department of Biomedical Sciences, University of Cagliari, 09042, Monserrato, Italy; Department of Biomedicine, University of Basel, Klingelbergstrasse 50-70, CH-4056, Basel, Switzerland.
² Department of Biomedical Sciences, University of Cagliari, 09042, Monserrato, Italy.
³ Department of Life Sciences and Biotechnology, Section of Medicinal and Health Products, and LTTA Center, University of Ferrara, Ferrara, Italy; Department of Medical, Oral and Biotechnological Sciences, University of Chieti-Pescara, 66100, Chieti, Italy.
⁴ Department of Life Sciences and Biotechnology, Section of Medicinal and Health Products, and LTTA Center, University of Ferrara, Ferrara, Italy.
⁵ Department of Biotechnology, Chemistry, and Pharmacy, University of Siena, I-53100, Siena, SI, Italy.
⁶ Department of Biomedicine, University of Basel, Klingelbergstrasse 50-70, CH-4056, Basel, Switzerland.
⁷ Department of Biomedical Sciences, University of Cagliari, 09042, Monserrato, Italy; Guy Everett Laboratory, University of Cagliari, 09042, Monserrato, Italy; Center of Excellence "Neurobiology of Addiction", University of Cagliari, 09042, Monserrato, Italy. Electronic address: castelli@unica.it.

PMID: 33798546
DOI: 10.1016/j.neuropharm.2021.108537

Abstract

Allosteric modulators of G protein coupled receptors (GPCRs), including GABA_BRs (GABA_BRs), are promising therapeutic candidates. While several positive allosteric modulators (PAM) of GABA_BRs have been characterized, only recently the first negative allosteric modulator (NAM) has been described. In the present study, we report the characterization of COR758, which acts as GABA_BR NAM in rat cortical membranes and CHO cells stably expressing GABA_BRs (CHO-GABA_B). COR758 failed to displace the antagonist [³H]CGP54626 from the orthosteric binding site of GABA_BRs showing that it acts through an allosteric binding site. Docking studies revealed a possible new allosteric binding site for COR758 in the intrahelical pocket of the GABA_B1 monomer. COR758 inhibited basal and GABA_BR-stimulated O-(3-[³⁵Sthio)-triphosphate ([³⁵S]GTPγS) binding in brain membranes and blocked the enhancement of GABA_BR-stimulated [³⁵S]GTPγS binding by the PAM GS39783. Bioluminescent resonance energy transfer (BRET) measurements in CHO-GABA_B cells showed that COR758 inhibited G protein activation by GABA and altered GABA_BR subunit rearrangements. Additionally, the compound altered GABA_BR-mediated signaling such as baclofen-induced inhibition of cAMP production in transfected HEK293 cells, agonist-induced Ca²⁺ mobilization as well as baclofen and the ago-PAM CGP7930 induced phosphorylation of extracellular signal-regulated kinases (ERK1/2) in CHO-GABA_B cells. COR758 also prevented baclofen-induced outward currents recorded from rat dopamine neurons, substantiating its property as a NAM for GABA_BRs. Altogether, these data indicate that COR758 inhibits G protein signaling by GABA_BRs, likely by interacting with an allosteric binding-site. Therefore, COR758 might serve as a scaffold to develop additional NAMs for therapeutic intervention.

Keywords: Allosteric modulators; Bioluminescence resonance energy transfer (BRET); GABA(B) receptors; GTPγS binding; Negative allosteric modulator (NAM).

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Allosteric Regulation / drug effects
Allosteric Regulation / physiology
Animals
Bioluminescence Resonance Energy Transfer Techniques / methods
CHO Cells
Cricetulus
Dose-Response Relationship, Drug
GABA Modulators / chemistry*
GABA Modulators / pharmacology*
GABA-B Receptor Agonists / chemistry
GABA-B Receptor Agonists / pharmacology
GABA-B Receptor Antagonists / chemistry*
GABA-B Receptor Antagonists / pharmacology*
Humans
Male
Rats
Rats, Sprague-Dawley
Receptors, GABA-B / physiology*
gamma-Aminobutyric Acid / chemistry
gamma-Aminobutyric Acid / pharmacology

Substances

GABA Modulators
GABA-B Receptor Agonists
GABA-B Receptor Antagonists
Receptors, GABA-B
gamma-Aminobutyric Acid