scholarly journals High Throughput Quantitation of cAMP Production Mediated by Activation of Seven Transmembrane Domain Receptors

1999 ◽  
Vol 4 (1) ◽  
pp. 27-32 ◽  
Author(s):  
Ilona Kariv ◽  
Michelle E. Stevens ◽  
Davette L. Behrens ◽  
Kevin R. Oldenburg
Keyword(s):  
Ligand Binding ◽  
G Protein ◽  
High Throughput ◽  
High Throughput Screening ◽  
Transmembrane Domain ◽  
Receptor Function ◽  
Camp Production ◽  
Ligand Interaction ◽  
G Protein Coupled ◽  
Native Ligand

Impairment of G protein—coupled seven-transmembrane (7 TM) receptor function has been implicated in a variety of different pathologic conditions, suggesting that the discovery of specific antagonists may lead to the development of successful therapeutic agents. The effect of different agents on receptor-ligand interaction is often measured directly in a receptor binding assay; however, this assay format can be time consuming and does not detect agents that interact at sites distal to the native ligand binding site. Cyclic adenosine monophospate (cAMP) represents a ubiquitous second messenger generated in response to ligand binding to many 7 TM receptors. The present study describes the practical adaptation of scintillation proximity methodology, using FlashPlate™ (NEN Life Sciences, Boston, MA) technology to evaluate cAMP production. The bioassay is based on competition between endogenously produced cAMP and exogenously added radiolabeled [125I]-cAMP. Cyclic AMP capture is mediated through an anti-cAMP antibody onto a microplate well surface. Removal of unbound radioligand is not necessary because only ligand within ≤20 μm of the plate surface is detected due to the proximity effect. The data indicate that the use of scintillation proximity technology allows accurate and specific evaluation of G protein—coupled receptor function as measured by cAMP production and is suitable for high throughput screening.

scholarly journals A Homogeneous Enzyme Fragment Complementation-Based β-Arrestin Translocation Assay for High-Throughput Screening of G-Protein-Coupled Receptors

2008 ◽  
Vol 13 (8) ◽  
pp. 737-747 ◽  
Author(s):  
Xiaoning Zhao ◽  
Adrie Jones ◽  
Keith R. Olson ◽  
Kun Peng ◽  
Tom Wehrman ◽  
...  
Keyword(s):  
G Protein ◽  
High Throughput ◽  
High Throughput Screening ◽  
Somatostatin Receptor ◽  
Gene Families ◽  
G Protein Coupled Receptors ◽  
Functional Assay ◽  
Gpcr Activation ◽  
Fragment Complementation ◽  
G Protein Coupled

G-protein-coupled receptors (GPCRs) represent one of the largest gene families in the human genome and have long been regarded as valuable targets for small-molecule drugs. The authors describe a new functional assay that directly monitors GPCR activation. It is based on the interaction between β-arrestin and ligand-activated GPCRs and uses enzyme fragment complementation technology. In this format, a GPCR of interest is fused to a small (~4 kDa), optimized α fragment peptide (termed ProLink™) derived from β-galactosidase, and β-arrestin is fused to an N-terminal deletion mutant of β-galactosidase (termed the enzyme acceptor [EA]). Upon activation of the receptor, the β-arrestin-EA fusion protein binds the activated GPCR. This interaction drives enzyme fragment complementation, resulting in an active β-galactosidase enzyme, and thus GPCR activation can be determined by quantifying β-galactosidase activity. In this report, the authors demonstrate the utility of this technology to monitor GPCR activation and validate the approach using a Gαi-coupled GPCR, somatostatin receptor 2. Potential application to high-throughput screens in both agonist and antagonist screening modes is exemplified. ( Journal of Biomolecular Screening 2008:737-747)

scholarly journals A Microdomain Formed by the Extracellular Ends of the Transmembrane Domains Promotes Activation of the G Protein-Coupled α-Factor Receptor

2004 ◽  
Vol 24 (5) ◽  
pp. 2041-2051 ◽  
Author(s):  
Jennifer C. Lin ◽  
Ken Duell ◽  
James B. Konopka
Keyword(s):  
Ligand Binding ◽  
G Protein ◽  
Transmembrane Domain ◽  
Receptor Activation ◽  
G Protein Coupled Receptors ◽  
Transmembrane Domains ◽  
Consecutive Series ◽  
Subsequent Step ◽  
G Protein Coupled ◽  
Specific Reagent

ABSTRACT The α-factor receptor (Ste2p) that promotes mating in Saccharomyces cerevisiae is similar to other G protein-coupled receptors (GPCRs) in that it contains seven transmembrane domains. Previous studies suggested that the extracellular ends of the transmembrane domains are important for Ste2p function, so a systematic scanning mutagenesis was carried out in which 46 residues near the ends of transmembrane domains 1, 2, 3, 4, and 7 were replaced with cysteine. These mutants complement mutations constructed previously near the ends of transmembrane domains 5 and 6 to analyze all the extracellular ends. Eight new mutants created in this study were partially defective in signaling (V45C, N46C, T50C, A52C, L102C, N105C, L277C, and A281C). Treatment with 2-([biotinoyl] amino) ethyl methanethiosulfonate, a thiol-specific reagent that reacts with accessible cysteine residues but not membrane-embedded cysteines, identified a drop in the level of reactivity over a consecutive series of residues that was inferred to be the membrane boundary. An unusual prolonged zone of intermediate reactivity near the extracellular end of transmembrane domain 2 suggests that this region may adopt a special structure. Interestingly, residues implicated in ligand binding were mainly accessible, whereas residues involved in the subsequent step of promoting receptor activation were mainly inaccessible. These results define a receptor microdomain that provides an important framework for interpreting the mechanisms by which functionally important residues contribute to ligand binding and activation of Ste2p and other GPCRs.

scholarly journals A Novel High Throughput Chemiluminescent Assay for the Measurement of Cellular Cyclic Adenosine Monophosphate Levels

2000 ◽  
Vol 5 (4) ◽  
pp. 239-247 ◽  
Author(s):  
Anthony C. Chiulli ◽  
Karen Trompeter ◽  
Michelle Palmer
Keyword(s):  
G Protein ◽  
High Throughput ◽  
High Throughput Screening ◽  
Cyclic Adenosine Monophosphate ◽  
Adenosine Monophosphate ◽  
Receptor Activation ◽  
G Protein Coupled Receptor ◽  
Wide Range ◽  
G Protein Coupled ◽  
Camp Levels

The second messenger 3′, 5′-cyclic AMP (cAMP) is a highly regulated molecule that is governed by G protein-coupled receptor activation and other cellular processes. Measurement of cAMP levels in cells is widely used as an indicator of receptor function in drug discovery applications. We have developed a nonradioactive ELISA for the accurate quantitation of cAMP levels produced in cell-based assays. This novel competitive assay utilizes chemiluminescent detection that affords both a sensitivity and a dynamic assay range that have not been previously reported with any other assay methodologies. The assay has been automated in 96- and 384-well formats, providing assay data that are equivalent to, if not better than, data generated by hand. This report demonstrates the application of this novel assay technology to the functional analysis of a specific G protein-coupled receptor, neuropeptide receptor Y1, on SK-N-MC cells. Our data indicate the feasibility of utilizing this assay methodology for monitoring cAMP levels in a wide range of functional cell-based assays for high throughput screening.

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