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Agonist-specific coupling of a cloned Drosophila octopamine/tyramine receptor to multiple second messenger systems
S Robb1, T R Cheek, F L Hannan
1AFRC Laboratory of Molecular Signalling, Department of Zoology, University of Cambridge, UK.
Abstract:
A cloned seven transmembrane-spanning Drosophila octopamine/tyramine receptor, permanently expressed in a Chinese hamster ovary cell line, both inhibits adenylate cyclase activity and leads to the elevation of intracellular Ca2+ levels by separate G-protein-coupled pathways. Agonists of this receptor (octopamine and tyramine), differing by only a single hydroxyl group in their side chain, may be capable of differentially coupling it to different second messenger systems. Thus, a single receptor may have a different pharmacological profile depending on which second messenger system is used to assay its efficacy.
Insights
This study shows a single Drosophila octopamine/tyramine receptor can activate different cellular pathways. Agonists like octopamine and tyramine may trigger distinct responses, influencing the receptor
Area of Science:
- Pharmacology
- Cellular Biology
- Neuroscience
Background:
- A cloned seven transmembrane-spanning Drosophila octopamine/tyramine receptor was permanently expressed in Chinese hamster ovary cells.
- Octopamine and tyramine receptors are crucial in invertebrate nervous systems.
- Understanding receptor signaling is key to developing targeted therapeutics.
Purpose of the Study:
- To investigate the signaling pathways activated by the Drosophila octopamine/tyramine receptor.
- To determine if different agonists (octopamine, tyramine) differentially couple the receptor to distinct second messenger systems.
- To explore the implications for receptor pharmacology and drug development.
Main Methods:
- Utilized a Chinese hamster ovary cell line stably expressing the cloned Drosophila octopamine/tyramine receptor.
- Assayed adenylate cyclase activity to measure G-protein-coupled inhibition.
- Measured intracellular Ca2+ levels to assess G-protein-coupled pathway activation.
Main Results:
- The receptor was found to inhibit adenylate cyclase activity via one G-protein-coupled pathway.
- The receptor also elevated intracellular Ca2+ levels through a separate G-protein-coupled pathway.
- Agonists octopamine and tyramine, differing by a single hydroxyl group, showed potential for differential pathway coupling.
Conclusions:
- A single octopamine/tyramine receptor can engage distinct intracellular signaling cascades.
- The pharmacological profile of the receptor may vary depending on the second messenger system being measured.
- This differential signaling offers a novel target for selective modulation of invertebrate physiology.