Transcripts encoding 5HT2C receptors are modified posttranscriptionally by RNA editing, generating up to 24 protein isoforms. In recombinant cells, the fully edited isoform, 5HT2C-VGV, exhibits blunted G-protein coupling and reduced constitutive activity. The present studies examine the signal transduction properties of 5HT2C-VGV receptors in brain to determine the in vivo consequences of altered editing. Due to a surprising lack of ligand affinity data in mice, we first established the selectivity of several 5-HT2 receptor ligands in mice. Using mice solely expressing the 5HT2C-VGV (VGV/Y) receptor, we demonstrate reduced G-protein coupling efficiencies and high-affinity agonist binding of brain 5HT2C-VGV receptors. However, enhanced behavioral sensitivity to a 5HT2C receptor agonist was also seen in mice expressing 5HT2C-VGV receptors, an unexpected finding given the blunted G-protein coupling. In addition, mice expressing 5HT2C-VGV receptors had enhanced sensitivity to 5HT2C inverse agonist/antagonist enhancement of dopamine turnover relative to wild-type mice. These behavioral and biochemical results are most likely explained by massive increases in receptor binding sites in the brains of mice solely expressing 5HT2C-VGV receptors. We conclude that 5-HT2C-VGV receptor signaling in brain is blunted, but this deficiency is masked by a marked increase in receptor binding site density. These findings suggest that RNA editing may regulate the density of 5-HT2C receptor binding sites in brain. We further caution that the pattern of 5-HT2C receptor RNA isoforms may not reflect the pattern of protein isoforms, and hence the inferred overall receptor functionality.
| Identifer | oai:union.ndltd.org:VANDERBILT/oai:VANDERBILTETD:etd-02012010-015023 |
| Date | 09 February 2010 |
| Creators | Olaghere da Silva, Uade |
| Contributors | Randy Blakely, Ariel Deutch, Sanika Chirwa, Elaine Sanders-Bush, Craig Kennedy |
| Publisher | VANDERBILT |
| Source Sets | Vanderbilt University Theses |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.vanderbilt.edu/available/etd-02012010-015023/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Vanderbilt University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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