Weitl, Nina and Seifert, Roland (2008) Distinct Interactions of Human beta(1)- and beta(2)-Adrenoceptors with Isoproterenol, Epinephrine, Norepinephrine, and Dopamine. JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS, 327 (3). pp. 760-769. ISSN 0022-3565,
Full text not available from this repository. (Request a copy)Abstract
Fluorescence studies with purified human beta(2)-adrenoceptor (beta(2)AR) revealed that the endogenous catecholamines, (-)-epinephrine (EPI), (-)-norepinephrine (NE), and dopamine (DOP), stabilize distinct active receptor conformations. However, the functional relevance of these ligand-specific conformations is as yet poorly understood. We addressed this question by studying fusion proteins of the beta(1)-adrenoceptor (beta(1)AR) and beta(2)AR with the short and long splice variants of G(s)alpha (G(s)alpha(S) and G(s)alpha(L)), respectively. Fusion proteins ensure efficient receptor/G-protein coupling and defined stoichiometry of the coupling partners. EPI, NE, DOP, and the prototypical synthetic beta AR agonist, (-)-isoproterenol (ISO), showed marked differences in their efficacies at stabilizing the high-affinity ternary complex at beta(1)AR-G(s)alpha and beta(2)AR-G(s)alpha fusion proteins. Ternary complex formation was more sensitive to disruption by GTP with the beta(2)AR than with the beta(1)AR. Generally, in steady-state GTPase assays, ISO, EPI, and NE were full agonists, and DOP was a partial agonist. Exceptionally, at beta(1)AR-G(s)alpha(L), NE was only a partial agonist. Generally, in adenylyl cyclase assays, ISO, EPI, and NE were full agonists, and DOP was a partial agonist. At beta(2)AR-G(s)alpha(L), NE was only a partial agonist. There was no correlation between efficacy at stabilizing the ternary complex and activating GTPase, and there were also dissociations between K-i values for high-affinity agonist binding and EC50 values for GTPase activation. In contrast to synthetic partial agonists, DOP did not exhibit increased efficacy at beta AR-G(s)alpha(L) versus beta AR-G(s)alpha(S) fusion proteins. In conclusion, our data with beta AR-G(s)alpha fusion proteins show that endogenous catecholamines and ISO stabilize distinct conformations in the beta(1)AR and beta(2)AR.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | RECEPTOR-G-PROTEIN; TERNARY COMPLEX MODEL; ADRENERGIC-RECEPTOR; SPLICE VARIANTS; CONFORMATIONAL STATES; QUANTITATIVE-ANALYSIS; CONSTITUTIVE ACTIVITY; MOLECULAR ANALYSIS; PARTIAL AGONISTS; FUSION PROTEINS; |
| Subjects: | 600 Technology > 615 Pharmacy |
| Divisions: | Chemistry and Pharmacy > Institute of Pharmacy > Pharmacology and Toxicology (Prof. Schlossmann, formerly Prof. Seifert) |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 19 Oct 2020 05:11 |
| Last Modified: | 19 Oct 2020 05:11 |
| URI: | https://pred.uni-regensburg.de/id/eprint/29986 |
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