Inhibition of Cell Surface Expression by Mutant Receptors Demonstrates that D2 Dopamine Receptors Exist as Oligomers in the Cell
- Samuel P. Lee1,
- Brian F. O'Dowd1,4,
- Gordon Y.K. Ng1,
- George Varghese1,
- Huda Akil5,
- Alfred Mansour2,5,
- Tuan Nguyen4 and
- Susan R. George1,3,4
- Departments of 1Pharmacology (S.P.L., B.F.O., G.V., S.R.G.),2Psychiatry (G.Y.N.), and 3Medicine (S.R.G.), University of Toronto, Toronto, Ontario; 4Centre for Addiction and Mental Health (B.F.O., T.N., S.R.G.), Toronto, Ontario; and 5Mental Health Research Institute (H.A., A.M.), University of Michigan, Ann Arbor, Michigan
Abstract
Numerous mutant G protein-coupled receptors with diminished or no function have been described that are naturally occurring or that are the product of gene manipulation. It has largely been assumed that receptor mutants do not affect the function of the wild-type receptor; however, the occurrence of G protein-coupled receptor dimerization suggests the possibility that an intermolecular interaction between mutant and wild-type receptors can occur. We have shown previously that the D2 dopamine receptor (D2DR) exists as dimers in cell lines and brain tissue. In this study, we demonstrated that mutant D2DR can modulate the function of the wild-type D2DR. While attempting to elucidate the structure of the D2DR dimer, we demonstrated that nonfunctional D2DR substitution and truncation mutants antagonized wild-type D2DR function. Furthermore, from analyses of this interaction between the receptor mutants and the D2DR, using photoaffinity labeling, we provide evidence that the D2DR is oligomeric in the cell.
Footnotes
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Dr. Susan R. George, Department of Pharmacology, University of Toronto, Room 4358, Medical Sciences Blgd., 1 King's College Circle, Toronto, ON M5S 1A8, Canada. E-mail:s.george{at}utoronto.ca.
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↵1 Current address: Merck Frosst Center for Therapeutic Research, Kirkland, QC H9H 3L1, Canada.
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↵2 Current address: Pharmaco Genesis, 6628 Heather Heath Lane, West Bloomfield, MI, 48322.
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This work was supported by grants from the Medical Research Council of Canada, the National Institute on Drug Abuse, the Smokeless Tobacco Research Council, an Addiction Research Foundation Fellowship to S.P.L., and a Medical Research Council of Canada Fellowship to G.N.
- Abbreviations:
- GPCR
- G protein-coupled receptor
- D2DR
- D2 dopamine receptor
- TM
- transmembrane
- D2N
- N terminus-truncated D2DR fragment (amino acids 1–373)
- D2C
- C terminus-truncated D2DR fragment (amino acids 212–414)
- PCR
- polymerase chain reaction
- CHO
- Chinese hamster ovary
- PNR
- putative neurotransmitter receptor
- azido-YM
- 4-azido-5-iodo-nemonapride
- azido-NAPS
- azidophenethyl-spiperone
- CCR5
- human chemokine receptor 5
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- Received November 5, 1999.
- Accepted March 28, 2000.
- The American Society for Pharmacology and Experimental Therapeutics
