The Alpha2 adrenergic receptor (AR) inhibits the ubiquitous regulatory enzyme adenylate cyclase via an interaction with a guanine nucleotide binding protein, Ni. This or similar quanine nucleotide binding proteins (N-proteins) may also have other functions such as regulation of phospholipase C or membrane potassium channels. The interaction of the Alpha2 AR with N-proteins has not been well characterized. The experiments will study the factors that control coupling of the Alpha2 AR with N-proteins by use of three approaches. First, selective inactivation of receptors with high and low affinity for agonists will be done to identify receptor heterogeneity that controls the interaction with N-proteins. The effect of such selective modification on inhibition of adenylate cyclase and stimulation of GTPase will also be studied. Second, reconstitution of Alpha2 AR and N-proteins will permit variation in both the identity (Ni vs No) and concentration of the components. Agonist binding will be compared to theoretical predictions for a ternary complex model of receptor N-protein interactions and differences between Alpha2 AR coupling with Ni and No will be evaluated. Finally, studies of solubilized Alpha2 AR using reconstitution, affinity labeling and purification will characterize the structural substrate of Alpha2 AR heterogeneity. A better understanding of Alpha2 AR mechanisms may yield new approaches to the study of pathophysiology and treatment of disorders such as hypertension, Alzheimer's disease and depression.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
1R01HL037551-01
Application #
3353305
Study Section
Pharmacology A Study Section (PHRA)
Project Start
1987-02-01
Project End
1990-01-31
Budget Start
1987-02-01
Budget End
1988-01-31
Support Year
1
Fiscal Year
1987
Total Cost
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Type
Schools of Medicine
DUNS #
791277940
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
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Zamorski, M A; Ferraro, J C; Neubig, R R (1990) Subcellular distribution of alpha 2-adrenergic receptors, pertussis-toxin substrate and adenylate cyclase in human platelets. Biochem J 265:755-62
Gerhardt, M A; Wade, S M; Neubig, R R (1990) p-[125I]iodoclonidine is a partial agonist at the alpha 2-adrenergic receptor. Mol Pharmacol 38:214-21
Michel, M C; Regan, J W; Gerhardt, M A et al. (1990) Nonadrenergic [3H]idazoxan binding sites are physically distinct from alpha 2-adrenergic receptors. Mol Pharmacol 37:65-8
Thomsen, W J; Neubig, R R (1989) Rapid kinetics of alpha 2-adrenergic inhibition of adenylate cyclase. Evidence for a distal rate-limiting step. Biochemistry 28:8778-86
Neubig, R R; Thomsen, W J (1989) How does a key fit a flexible lock? Structure and dynamics in receptor function. Bioessays 11:136-41
Thomsen, W J; Jacquez, J A; Neubig, R R (1988) Inhibition of adenylate cyclase is mediated by the high affinity conformation of the alpha 2-adrenergic receptor. Mol Pharmacol 34:814-22