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Dissertation
The structural features of the ligand binding site of the serotonin type 3 receptor
Doctor of Philosophy (Ph.D.), Medical College of Pennsylvania and Hahnemann University
Aug 2002
DOI:
https://doi.org/10.17918/00009470
Abstract
A member of the ligand-gated ion channel (LGIC) superfamily, the serotonin type 3 receptor (5-HT₃R) is involved in many important physiological and pathological actions in both the central and peripheral nervous system. Functional studies have been conducted extensively on various aspects of this receptor, for example, regulation of the release of other neurotransmitters, pain transmission, vomiting reflex, and some aspects have been transformed into clinical applications, such as antiemetic treatment with 5-HT₃R antagonists after chemotherapy. To date, structural studies have been lacking. Consequently, the molecular basis for the functional activation of the 5-HT₃R has remained unclear until now. In the present study, we applied ligand binding assays, whole-cell patch clamping, and site-directed mutagenesis techniques, including the "alanine scan" method, to specifically target the ligand-binding domain at the N-terminal region of the 5-HT₃R. By using curare and its analogs to interact with 5-HT₃R, and then correlating with data from previous studies on the nicotinic acetylcholine receptor (nAChR), we showed a close resemblance between the ligand-binding domains of nAChR and 5-HT₃R. Using the information from the curare analog binding experiments, we focused on Trp90, which is homologous to [gamma]Trp55 and [delta]Trp57 in nAChR, and on the region neighboring Trp90. Those two tryptophan residues in nAChR have been shown to be involved in curare binding. We successfully identified Trp90 in 5-HT₃R as involved in curare and granisetron binding, Arg92 in serotonin and granisetron binding, and Tyr94 in granisetron binding only. We also determined that the secondary structure for the local region flanking Trp90 is [beta]-strand. However, further studies indicate that although this region is involved in ligand binding in 5-HT₃R, it may not come in to direct contact with the ligand. Our findings reveal for the first time evidence for the secondary structure of part of the ligand binding domain of 5-HT₃R, providing a better understanding of the ligand binding process of this ligand-gated ion channel. This understanding will facilitate the design of new 5-HT₃R ligands, with the aim of more accurate targeting and fewer side effects in their clinical usage.
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Details
- Title
- The structural features of the ligand binding site of the serotonin type 3 receptor
- Creators
- Dong Yan
- Contributors
- Michael M. White (Advisor) - Drexel University, Medical College of Pennsylvania and Hahnemann University (1993-1996, 1998-2002)
- Awarding Institution
- Medical College of Pennsylvania and Hahnemann University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Medical College of Pennsylvania and Hahnemann University; Philadelphia, Pennsylvania
- Number of pages
- xii, 163 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- School of Medicine (1993-1996, 1998-2002); Medical College of Pennsylvania and Hahnemann University (1993-1996, 1998-2002)
- Other Identifier
- 991021888844904721