RNA editing of the human serotonin 5-hydroxytryptamine 2C receptor silences constitutive activity.

Niswender CM, Copeland SC, Herrick-Davis K, Emeson RB, Sanders-Bush E
J Biol Chem. 1999 274 (14): 9472-8

PMID: 10092629 · DOI:10.1074/jbc.274.14.9472

RNA transcripts encoding the serotonin 5-hydroxytryptamine 2C (5-HT2C) receptor (5-HT2CR) undergo adenosine-to-inosine RNA editing events at up to five specific sites. Compared with rat brain, human brain samples expressed higher levels of RNA transcripts encoding the amino acids valine-serine-valine (5-HT2C-VSV) and valine-glycine-valine (5-HT2C-VGV) at positions 156, 158, and 160, respectively. Agonist stimulation of the nonedited human receptor (5-HT2C-INI) and the edited 5-HT2C-VSV and 5-HT2C-VGV receptor variants stably expressed in NIH-3T3 fibroblasts demonstrated that serotonergic agonists were less potent at the edited receptors. Competition binding experiments revealed a guanine nucleotide-sensitive serotonin high affinity state only for the 5-HT2C-INI receptor; the loss of high affinity agonist binding to the edited receptor demonstrates that RNA editing generates unique 5-HT2CRs that couple less efficiently to G proteins. This reduced G protein coupling for the edited isoforms is primarily due to silencing of the constitutive activity of the nonedited 5-HT2CR. The distinctions in agonist potency and constitutive activity suggest that different edited 5-HT2CRs exhibit distinct responses to serotonergic ligands and further imply that RNA editing represents a novel mechanism for controlling physiological signaling at serotonergic synapses.

MeSH Terms (13)

3T3 Cells Adenosine Animals Binding, Competitive Brain Chemistry Humans Inosine Isomerism Mice Rats Receptor, Serotonin, 5-HT2C Receptors, Serotonin RNA Editing

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