Abstract
Drugs targeting G-protein-coupled receptors (GPCRs) make up more than 25% of all prescribed medicines. The ability of GPCRs to form heteromers with unique signaling properties suggests an entirely new and unexplored pool of drug targets. However, current in vitro assays are ill equipped to detect heteromer-selective compounds. We have successfully adapted an approach, using fusion proteins of GPCRs and chimeric G proteins, to create an in vitro screening assay (in human embryonic kidney cells) in which only activated heteromers are detectable. Here we show that this assay can demonstrate heteromer-selective G-protein bias as well as measure transinhibition. Using this assay, we reveal that the δ-opioid receptor agonist ADL5859, which is currently in clinical trials, has a 10-fold higher potency against δ-opioid receptor homomers than δ/μ-opioid receptor heteromers (pEC50 = 6.7 ± 0.1 versus 5.8 ± 0.2). The assay enables the screening of large compound libraries to identify heteromer-selective compounds that could then be used in vivo to determine the functional role of heteromers and develop potential therapeutic agents.
Footnotes
This work was funded by the Foundation for Alcohol Research-Alcoholic Beverage Medical Research Foundation (R.M.v.R.); the National Institutes of Health National Institute on Alcohol Abuse and Alcoholism [Grants K99AA020539 (to R.M.v.R.), R01AA020401 (to J.L.W.), and P50AA017072-03], and National Institutes of Health National Institute on Drug Abuse [Grants R01DA015232 and R01DA019958 (to J.L.W.)]. J.H.H. is supported in part by grants from the Program for Breakthrough Biomedical Research and the A. P. Giannini Foundation. Funds were also provided by the State of California for medical research on alcohol and substance abuse through the University of California, San Francisco, to J.L.W.
- Received July 30, 2012.
- Accepted October 24, 2012.
- Copyright © 2013 by The American Society for Pharmacology and Experimental Therapeutics
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