Abstract
G protein-coupled receptors (GPCRs) are the largest family of cell surface receptors and a key drug target class. Recently, allosteric drugs that can cobind with and modulate the activity of the endogenous ligand(s) for the receptor have become a major focus of the pharmaceutical and biotechnology industry for the development of novel GPCR therapeutic agents. This class of drugs has distinct properties compared with drugs targeting the endogenous (orthosteric) ligand-binding site that include the ability to sculpt cellular signaling and to respond differently in the presence of discrete orthosteric ligands, a behavior termed “probe dependence.” Here, using cell signaling assays combined with ex vivo and in vivo studies of insulin secretion, we demonstrate that allosteric ligands can cause marked potentiation of previously “inert” metabolic products of neurotransmitters and peptide hormones, a novel consequence of the phenomenon of probe dependence. Indeed, at the muscarinic M2 receptor and glucagon-like peptide 1 (GLP-1) receptor, allosteric potentiation of the metabolites, choline and GLP-1(9–36)NH2, respectively, was ∼100-fold and up to 200-fold greater than that seen with the physiological signaling molecules acetylcholine and GLP-1(7–36)NH2. Modulation of GLP-1(9–36)NH2 was also demonstrated in ex vivo and in vivo assays of insulin secretion. This work opens up new avenues for allosteric drug discovery by directly targeting modulation of metabolites, but it also identifies a behavior that could contribute to unexpected clinical outcomes if interaction of allosteric drugs with metabolites is not part of their preclinical assessment.
Footnotes
↵ The online version of this article (available at http://molpharm.aspetjournals.org) contains supplemental material.
This work was supported by the National Health and Medical Research Council of Australia [Project Grants 1002180, 519461] and the Australian Research Council [Discovery Grant 110100687].
Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
ABBREVIATIONS:
- GPCR
- G protein-coupled receptor
- GLP-1
- glucagon-like peptide 1
- GLP-1R
- glucagon-like peptide 1 receptor
- LUF6000
- N-(3,4-dichlorophenyl)-2-cyclohexyl-1H-imidazo[4,5-c]quinolin-4-amine
- A3-AR
- adenosine receptor subtype 3
- M2 mAChR
- muscarinic acetylcholine receptor, subtype 2
- A1-AR
- adenosine receptor subtype 1
- ERK1/2
- extracellular signal-regulated kinase 1 and 2
- DMEM
- Dulbecco's modified Eagle's medium
- FBS
- fetal bovine serum
- LY2033298
- 3-amino-5-chloro-N-cyclopropyl-6-methoxy-4-methyl-thieno[2,3-b]pyridine-2-carboxamide
- Compound 2
- 6,7-dichloro-2-methylsulfonyl-3-tert-butylaminoquinoxaline
- BETP
- (4-(3-benzyloxyphenyl)-2-ethylsulfinyl-6-(trifluoromethyl)pyrimidine
- VCP171
- (2-amino-4-(3-(trifluoromethyl)phenyl)thiophen-3-yl)(phenyl)methanone
- CHO
- Chinese hamster ovary
- ACh
- acetylcholine
- Ch
- choline
- PD81723
- (2-amino-4,5-dimethyl-3-thienyl)(3-(trifluoromethyl)phenyl)-methanone
- GTPγS
- guanosine 5′-O-(3-thio)triphosphate
- IVGTT
- intravenous glucose tolerance test
- pERK1/2
- extracellular signal-related kinase 1 and 2 phosphorylation
- DM
- diabetes mellitus.
- Received April 13, 2012.
- Accepted May 10, 2012.
- Copyright © 2012 The American Society for Pharmacology and Experimental Therapeutics
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