Division of Medicinal Pharmacology, Institute of Natural Medicine, University of Toyama, Sugitani, Japan.
J Pharmacol Sci. 2010;113(4):362-7. doi: 10.1254/jphs.10094fp. Epub 2010 Jul 23.
Serotonin 2C receptor (5-HT2CR) mRNA receives editing at 5 nucleotide positions (sites A-E) located in the sequence encoding the second intracellular loop of 5-HT2CR. 5-HT2CR mRNA without editing and with editing at sites AB, ABD, ABC, ABCD, and C are translated to 6 isoforms of 5-HT2CR: INI(non-edited), VNI(AB), VNV(ABD), VSI(ABC), VSV(ABCD), and ISI(C), respectively. In this study, we investigated electrophysiologically the ability of these isoforms to couple with the G protein/phospholipase C (PLC) system using Xenopus oocytes injected with edited 5-HT2CR RNAs and muscarinic M(1) receptor (M1R) RNA. The efficacy with which 5-HT stimulated each isoform was calculated by comparing 5-HT-induced current with 100 microM acetylcholine-induced M1R current. Stimulation with 5-HT of INI(non-edited), VNI(AB), VNV(ABD), VSI(ABC), VSV(ABCD), and ISI(C) expressed in Xenopus oocytes showed concentration-dependent responses with EC(50) values of 8.6, 17.2, 76,5, 22.0, 91.2, and 20.3 nM, respectively. No significant difference in the ability of 5-HT to induce currents among the oocytes expressing these isoforms was detected, but in the oocytes expressing VSI(ABC) or VSV(ABCD), 5-HT had a significantly reduced ability to induce currents. These results suggest that editing at site C together with sites A and B and/or D markedly reduces 5-HT2CR function by generating isoforms with reduced ability to activate PLC.
血清素 2C 受体（5-HT2CR）mRNA 在 5 个核苷酸位置（A-E 位点）接受编辑，这些位置位于 5-HT2CR 第二细胞内环的编码序列中。未经编辑和在 AB、ABD、ABC、ABCD 和 C 位点编辑的 5-HT2CR mRNA 分别被翻译为 5-HT2CR 的 6 种同工型：INI（未编辑）、VNI（AB）、VNV（ABD）、VSI（ABC）、VSV（ABCD）和 ISI（C）。在这项研究中，我们使用注射了编辑后的 5-HT2CR RNA 和毒蕈碱 M1 受体（M1R）RNA 的非洲爪蟾卵母细胞，在电生理水平上研究了这些同工型与 G 蛋白/磷脂酶 C（PLC）系统偶联的能力。通过比较 5-HT 诱导的电流与 100 μM 乙酰胆碱诱导的 M1R 电流，计算每种同工型刺激的效力。在非洲爪蟾卵母细胞中表达的 INI（未编辑）、VNI（AB）、VNV（ABD）、VSI（ABC）、VSV（ABCD）和 ISI（C）刺激 5-HT 显示出浓度依赖性反应，EC50 值分别为 8.6、17.2、76.5、22.0、91.2 和 20.3 nM。在表达这些同工型的卵母细胞中，5-HT 诱导电流的能力没有显著差异，但在表达 VSI（ABC）或 VSV（ABCD）的卵母细胞中，5-HT 诱导电流的能力显著降低。这些结果表明，C 位点与 A 和 B 位点和/或 D 位点的编辑显著降低了 5-HT2CR 的功能，产生了激活 PLC 能力降低的同工型。
