RNA-editing of the 5-HT(2C) receptor alters agonist-receptor-effector coupling specificity.

Department of Pharmacology, Mail Code 7764, University of Texas Health Science Center, San Antonio, Texas, TX 78229-3900, USA.
British Journal of Pharmacology (Impact Factor: 4.99). 10/2001; 134(2):386-92. DOI: 10.1038/sj.bjp.0704255
Source: PubMed

ABSTRACT 1. The serotonin(2C) (5-HT(2C)) receptor couples to both phospholipase C (PLC)-inositol phosphate (IP) and phospholipase A(2) (PLA(2))-arachidonic acid (AA) signalling cascades. Agonists can differentially activate these effectors (i.e. agonist-directed trafficking of receptor stimulus) perhaps due to agonist-specific receptor conformations which differentially couple to/activate transducer molecules (e.g. G proteins). Since editing of RNA transcripts of the human 5-HT(2C) receptor leads to substitution of amino acids at positions 156, 158 and 160 of the putative second intracellular loop, a region important for G protein coupling, we examined the capacity of agonists to activate both the PLC-IP and PLA(2)-AA pathways in CHO cells stably expressing two major, fully RNA-edited isoforms (5-HT(2C-VSV), 5-HT(2C-VGV)) of the h5-HT(2C) receptor. 2. 5-HT increased AA release and IP accumulation in both 5-HT(2C-VSV) and 5-HT(2C-VGV) expressing cells. As expected, the potency of 5-HT for both RNA-edited isoforms for both responses was 10 fold lower relative to that of the non-edited receptor (5-HT(2C-INI)) when receptors were expressed at similar levels. 3. Consistent with our previous report, the efficacy order of two 5-HT receptor agonists (TFMPP and bufotenin) was reversed for AA release and IP accumulation at the non-edited receptor thus demonstrating agonist trafficking of receptor stimulus. However, with the RNA-edited receptor isoforms there was no difference in the relative efficacies of TFMPP or bufotenin for AA release and IP accumulation suggesting that the capacity for 5-HT(2C) agonists to traffic receptor stimulus is lost as a result of RNA editing. 4. These results suggest an important role for the second intracellular loop in transmitting agonist-specific information to signalling molecules.

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    ABSTRACT: Serotonin 2C receptors (5-HT2CR) are G-protein-coupled receptors with various actions, including involvement in drug addiction. 5-HT2CR undergoes mRNA editing, converting genomically encoded adenosine residues to inosines via adenosine deaminases acting on RNA (ADARs). Here we show that enhanced alcohol drinking behaviour in mice is associated with the degree of 5-HT2CR mRNA editing in the nucleus accumbens and dorsal raphe nuceus, brain regions important for reward and addiction. Following chronic alcohol vapour exposure, voluntary alcohol intake increased in C57BL/6J mice, but remained unchanged in C3H/HeJ and DBA/2J mice. 5-HT2CR mRNA editing frequency in both regions increased significantly in C57BL/6J mice, as did expressions of 5-HT2CR, ADAR1 and ADAR2, but not in other strains. Moreover, mice that exclusively express the unedited isoform (INI) of 5-HT2CR mRNA on a C57BL/6J background did not exhibit increased alcohol intake compared with wild-type mice. Our results indicate that alterations in 5-HT2CR mRNA editing underlie alcohol preference in mice.
    The International Journal of Neuropsychopharmacology 12/2013; · 5.64 Impact Factor

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