Use of the GTPγS ([35S]GTPγS and Eu‐GTPγS) binding assay for analysis of ligand potency and efficacy at G protein‐coupled receptors

In this review I consider assays for G protein‐coupled receptor (GPCR) activity based on the binding of labelled analogues of GTPγS ([35S]GTPγS or Eu‐GTPγS) to G proteins in tissues (GTPγS binding assays). Such assays provide convenient measures of GPCR activity close to the receptor in the signalli...

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Published in:British journal of pharmacology 2010-11, Vol.161 (6), p.1238-1249
Main Author: Strange, Philip G.
Format: Article
Language:English
Subjects:
agonist
Animals
antagonist
Drug Inverse Agonism
drug screening
efficacy
functional assay
GTPγS binding assay
Guanosine 5'-O-(3-Thiotriphosphate) - metabolism
Humans
inverse agonist
Ligands
Radioligand Assay - methods
Radioligand Assay - utilization
Receptors, G-Protein-Coupled - metabolism
Sulfur Radioisotopes - metabolism
Themed Section: Reviews
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Summary:In this review I consider assays for G protein‐coupled receptor (GPCR) activity based on the binding of labelled analogues of GTPγS ([35S]GTPγS or Eu‐GTPγS) to G proteins in tissues (GTPγS binding assays). Such assays provide convenient measures of GPCR activity close to the receptor in the signalling cascade. In order to set up a GTPγS binding assay, the requirements of the assay must be considered. These are tissue source, GTPγS analogue, G protein, GDP, Mg2+/Na+ ions, saponin, incubation time. The assay, once optimized, can be used to generate concentration/response curves for GPCRs signalling via Gi/o proteins (or to other G proteins with a modified assay) and actions of agonists, inverse agonists and antagonists may, in principle, be assessed. For agonists and inverse agonists, data for the maximal agonist effect, the concentration of ligand giving a half‐maximal response and the Hill coefficient may be derived. For antagonists, data for the equilibrium dissociation constant can be obtained. The mechanistic basis of the assay is considered. Although the assay can be used to profile ligands, under the conditions it is used, it may not be measuring the same event that determines GPCR action in cells. LINKED ARTICLES This article is part of a themed section on Analytical Receptor Pharmacology in Drug Discovery. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2010.161.issue‐6
ISSN:0007-1188
1476-5381
DOI:10.1111/j.1476-5381.2010.00963.x