Alternative links to fulltext:DOI
| Item type: | Article | ||||
|---|---|---|---|---|---|
| Journal or Publication Title: | Journal of Pharmacology and Experimental Therapeutics . JPET | ||||
| Publisher: | AMER SOC PHARMACOLOGY EXPERIMENTAL THERAPEUTICS | ||||
| Place of Publication: | BETHESDA | ||||
| Volume: | 332 | ||||
| Number of Issue or Book Chapter: | 3 | ||||
| Page Range: | pp. 996-1005 | ||||
| Date: | March 2010 | ||||
| Institutions: | Chemistry and Pharmacy > Institute of Pharmacy > Pharmacology and Toxicology (Prof. Schlossmann, formerly Prof. Seifert) | ||||
| Identification Number: |
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| Keywords: | HIGH CONSTITUTIVE ACTIVITY; FORMYL PEPTIDE RECEPTOR; SF9 INSECT CELLS; DISTINCT INTERACTIONS; MOLECULAR ANALYSIS; FUSION PROTEINS; SPLICE VARIANTS; GUINEA-PIG; BETA(2)-ADRENOCEPTOR; ANTAGONISTS; | ||||
| Dewey Decimal Classification: | 600 Technology > 615 Pharmacy | ||||
| Status: | Published | ||||
| Refereed: | Yes, this version has been refereed | ||||
| Created at the University of Regensburg: | Yes | ||||
| Item ID: | 20190 |
Web of ScienceAbstract
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. ...
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.
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