Schnell, David and Burleigh, Katrina and Trick, Jonathan and Seifert, Roland (2010) No Evidence for Functional Selectivity of Proxyfan at the Human Histamine H-3 Receptor Coupled to Defined G(i)/G(o) Protein Heterotrimers. JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS, 332 (3). pp. 996-1005. ISSN 0022-3565,
Full text not available from this repository. (Request a copy)Abstract
Numerous structurally diverse ligands were developed to target the human histamine H-3 receptor (hH(3)R), a presynaptic G(i)/G(o)-coupled auto- and heteroreceptor. Proxyfan was identified to be functionally selective, with different efficacies toward G(i)/G(o) dependent hH(3)R signaling pathways. However, the underlying molecular mechanism of functional selectivity of proxyfan is still unclear. In the current study, we investigated the role of different G alpha(i/o) proteins in hH(3)R signaling, using a baculovirus/Sf9 cell expression system. We tested the hypothesis that ligand-specific coupling differences to defined G(i)/G(o)-heterotrimers are responsible for functional selectivity of proxyfan at hH(3)R. In Sf9 membranes, full-length hH(3)R (445 amino acids) was expressed in combination with an excess of different mammalian G proteins (G alpha(i1), G alpha(i2), G alpha(i3), or G alpha(o1) and beta(1)gamma(2) dimers, respectively). In addition, we constructed the fusion proteins hH(3)R-G alpha(i2) and hH(3)R-G alpha(o1) to ensure clearly defined receptor/G protein stoichiometries. Steady-state GTPase experiments were performed to directly measure the impact of each G protein on hH(3)R signal transduction. The hH(3)R coupled similarly to all G proteins. We also observed similar ligand-independent or constitutive activity. Proxyfan and various other imidazole-containing ligands, including full agonists, partial agonists, and inverse agonists, showed very similar pharmacological profiles not influenced by the type of G protein coexpressed. Selected ligands, examined in membranes expressing the fusion proteins hH(3)R-G alpha(i2) and hH(3)R-G alpha(o1) (plus beta(1)gamma(2) dimers), yielded very similar results. Collectively, our data indicate that hH(3)R couples similarly to different G alpha(i/o)-subunits and that ligand-specific active receptor conformations, resulting in G protein-coupling preferences, do not exist for proxyfan or other imidazole compounds investigated.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | HIGH CONSTITUTIVE ACTIVITY; FORMYL PEPTIDE RECEPTOR; SF9 INSECT CELLS; DISTINCT INTERACTIONS; MOLECULAR ANALYSIS; FUSION PROTEINS; SPLICE VARIANTS; GUINEA-PIG; BETA(2)-ADRENOCEPTOR; ANTAGONISTS; |
| 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: | 05 Aug 2020 09:16 |
| Last Modified: | 05 Aug 2020 09:16 |
| URI: | https://pred.uni-regensburg.de/id/eprint/25093 |
Actions (login required)
 |
View Item |
