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Cloning and functional expression of a human 5-hydroxytryptamine type 3AS receptor subunit
D Belelli1, J M Balcarek, A G Hope
1Department of Pharmacology and Clinical Pharmacology, Ninewells Hospital and Medical School, The University, Dundee, UK.
Molecular Pharmacology
|December 1, 1995
Summary
Researchers cloned the human 5-hydroxytryptamine receptor type 3AS (5-HT3R-AS) subunit, revealing its sequence and function. Pharmacological differences between human and mouse receptors, particularly with (+)-tubocurarine, offer insights into ligand binding sites.
Area of Science:
- Neuroscience
- Molecular Biology
- Pharmacology
Background:
- The 5-hydroxytryptamine type 3 receptor (5-HT3R) is a ligand-gated ion channel involved in various physiological processes.
- Understanding the human 5-HT3R-AS subunit is crucial for elucidating its role in neurological functions and drug development.
Purpose of the Study:
- To clone and characterize the human 5-hydroxytryptamine receptor type 3AS (5-HT3R-AS) subunit.
- To compare the pharmacological properties of human and mouse 5-HT3R-AS receptor complexes.
- To identify key regions involved in ligand binding.
Main Methods:
- Cloning of the human 5-HT3R-AS subunit from an amygdala cDNA library.
- Expression of the human 5-HT3R-AS subunit in Xenopus laevis oocytes.
- Electrophysiological recordings to assess receptor function and pharmacology.
- Quantitative comparison of pharmacological profiles with mouse homologues.
Main Results:
- The human 5-HT3R-AS subunit sequence was determined, showing high identity with mouse and rat counterparts.
- Functional expression in oocytes confirmed responses to 5-HT and selective agonists, with characteristic desensitization.
- Receptor activity was blocked by 5-HT3 antagonists but not by G protein-linked 5-HT receptor ligands.
- Significant differences in antagonist potency, such as for (+)-tubocurarine, were observed between human and mouse receptors.
- A homo-oligomeric assembly of human 5-HT3R-AS subunits may explain observed ligand binding properties.
Conclusions:
- The cloned human 5-HT3R-AS subunit provides a valuable tool for studying serotonin receptor function.
- Pharmacological discrepancies, especially with (+)-tubocurarine, highlight the importance of specific amino acid residues in the ligand-binding site.
- Further studies using site-directed mutagenesis can pinpoint residues critical for ligand interaction.
- The findings suggest that human 5-HT3 receptors can be formed by homo-oligomeric assembly of 5-HT3R-AS subunits.
