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Agonist-induced functional desensitization of recombinant human 5-HT2 receptors expressed in CHO-K1 cells
The desensitization characteristics of recombinant human 5-HT 2A, 5-HT 2B, and 5-HT 2C receptors (VSV and INI isoforms) stably expressed in CHO-K1 (Chinese hamster ovary) cells was investigated by calcium fluorimetry. Comparative desensitization characteristics of the agonists 5-HT, m-chlorophenylpi...
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Published in: | Biochemical pharmacology 2001-08, Vol.62 (4), p.431-438 |
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Main Authors: | , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Online Access: | Get full text |
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Summary: | The desensitization characteristics of recombinant human 5-HT
2A, 5-HT
2B, and 5-HT
2C receptors (VSV and INI isoforms) stably expressed in CHO-K1 (Chinese hamster ovary) cells was investigated by calcium fluorimetry. Comparative desensitization characteristics of the agonists 5-HT, m-chlorophenylpiperazine (mCPP), and 2,5-dimethoxy-4-iodoamphetamine hydrobromide (DOI) were performed. Human 5-HT
2C (INI) receptors exhibited a greater degree of desensitization to all agonists tested than edited 5-HT
2C (VSV) receptors. A 2-hr exposure to 5-HT resulted in a significantly larger reduction in response upon re-exposure to 5-HT at 5-HT
2C (INI) receptors, as compared to 5-HT
2C (VSV) receptors (72% and 47% respectively,
P < 0.01). Both receptor isoforms were expressed at similar densities. Human 5-HT
2B receptors exhibited the most dramatic degree of desensitization, with prior exposure to 5-HT reducing subsequent response to 5-HT by 80%, with an extremely rapid time-course (
t
1
2
< 5 min). The response at 5-HT
2A receptors was reduced by 54%. The partial agonists mCPP and DOI also elicited desensitization, generally in line with their relative efficacies at each receptor, but exhibited more rapid kinetic profiles than 5-HT. Heterologous desensitization of an endogenously expressed G
q/11-coupled purinergic receptor was also examined following preincubation of the cell lines with 10 μM 5-HT. Only stimulation of 5-HT
2C (VSV) receptors resulted in a profound attenuation of subsequent ATP mediated responses. These results demonstrate differing degrees of both homologous and heterologous desensitization of 5-HT
2 receptors. Additionally, the different desensitization profiles of 5-HT
2C (INI) and 5-HT
2C (VSV) receptor may be due to signal transduction differences caused by RNA editing. |
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ISSN: | 0006-2952 1873-2968 |
DOI: | 10.1016/S0006-2952(01)00677-3 |