Agonist ligand discrimination by the two orexin receptors depends on the expression system
| Autor: | Marie E. Ekholm, Pauli M. Turunen, Jaana Putula, Jyrki P. Kukkonen, Maria Jäntti |
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| Rok vydání: | 2011 |
| Předmět: |
Receptors
Neuropeptide Agonist medicine.drug_class CHO Cells Pharmacology Ligands Partial agonist Receptors G-Protein-Coupled 03 medical and health sciences Orexin-A Cricetulus 0302 clinical medicine Orexin Receptors Cricetinae mental disorders medicine Animals Humans Receptor Cells Cultured 030304 developmental biology G protein-coupled receptor Orexins 0303 health sciences Chemistry General Neuroscience Chinese hamster ovary cell Neuropeptides digestive oral and skin physiology Intracellular Signaling Peptides and Proteins Molecular biology Orexin receptor Orexin HEK293 Cells nervous system 030217 neurology & neurosurgery Protein Binding |
| Zdroj: | Neuroscience Letters. 494:57-60 |
| ISSN: | 0304-3940 |
| DOI: | 10.1016/j.neulet.2011.02.055 |
| Popis: | Despite the recent successes in producing orexin receptor subtype-selective antagonists, these are not commonly available, and therefore, agonist ligands are regularly used to ascribe cell and tissue responses to OX 1 or OX 2 receptors. In the current study, we have compared the native “subtype-selective” agonist, orexin-B, and its reputedly enhanced synthetic variant, Ala 11 , d -Leu 15 -orexin-B, in two different recombinant cell lines. Ca 2+ elevation was used as readout, and the two “selective” ligands were compared to the subtype-non-selective orexin-A, as is customary with these ligands. In transiently transfected HEK-293 cells, orexin-B showed 9-fold selectivity for the OX 2 receptor and Ala 11 , d -Leu 15 -orexin-B 23-fold selectivity, when the potency ratios of ligands were compared between OX 1 and OX 2 . In stable CHO-K1 cells, the corresponding values were only 2.6- and 14-fold, respectively. In addition to being low, the selectivity of the ligands was also variable, as indicated by the comparison of the two cell lines. For instance, the relative potency of Ala 11 , d -Leu 15 -orexin-B at OX 2 in CHO cells was only 2.3-fold higher than its relative potency at OX 1 in HEK-293 cells; this indicates that Ala 11 , d -Leu 15 -orexin-B does not show high enough selectivity for OX 2 to be useful for determination of receptor subtype expression. Comparison of the potencies of orexin-A and -B with respect to a number of published responses in OX 1 -expressing CHO cells, demonstrates that these show great variation: i.e., orexin-A is 1.6–18-fold more potent than orexin-B, depending on the response assessed. These data together suggest that orexin receptor ligands show signal trafficking, which makes agonist-based pharmacology unreliable. |
| Databáze: | OpenAIRE |
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