Abstract
In most tissues and cells the opioid receptor-like (ORL1) receptor regulates effectors primarily through the pertussis toxin (PTX)-sensitive guanine nucleotide-binding regulatory proteins (G proteins) Gi/Go. Many Gi-coupled receptors possess additional capability to interact with one or more PTX-insensitive G proteins. Using the βγ-induced stimulation of type 2 adenylyl cyclase as a readout, we screened the ability of ORL1 receptor to interact with a panel of PTX-insensitive G proteins. In the presence of PTX, activation of the ORL1 receptor resulted in the stimulation of type 2 adenylyl cyclase only in HEK 293 cells coexpressing the α subunit of Gz, G12, G14, or G16, but not in cells coexpressing G11, G13, or Gq. Coupling to both Gz and G16 was expected because close relatives of the ORL1 receptor, the opioid receptors, are known to couple productively to these G proteins. ORL1 receptor coupling to either G12 or G14 has not been demonstrated. As predicted by the type 2 adenylyl cyclase assays, activation of the ORL1 receptor resulted in the formation of inositol phosphates in COS-7 cells transiently cotransfected with Gα14. The ORL1receptor-mediated stimulation of phospholipase C was found to be Gα14 dependent, agonist dose dependent, ligand selective, and PTX insensitive. We conclude that G14 can link the ORL1 receptor to regulation of phopholipase C.
Footnotes
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Send reprint requests to: Dr. Yung H. Wong, Department of Biology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China. E-mail: boyung{at}uxmail.ust.hk
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↵1 This work was supported in part by grants from the Biotechnology Research Institute (BRI 96-I-3) and the Research Grants Council of Hong Kong (HKUST 6176/97M) to Y.H.W.
- Abbreviations:
- AC2
- type 2 adenylyl cyclase
- DAGO
- [d-Ala2, N-Me-Phe4, Gly5-ol]enkephalin
- DMEM
- Dulbecco’s modified Eagle’s medium
- DPDPE
- [d-Pen2,5]enkephalin
- G protein
- guanine nucleotide-binding regulatory protein
- HEK 293 cells
- human embryonic kidney cells
- MEM
- minimum essential medium
- ORL
- opioid receptor-like
- PLC
- phospholipase C
- PTX
- pertussis toxin
- FCS
- fetal calf serum
- IP
- inositol phosphate
- Received March 18, 1998.
- Accepted August 10, 1998.
- The American Society for Pharmacology and Experimental Therapeutics
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