Ase Ariel R, Raouf Ramin, Bélanger Danny, Hamel Edith, Séguéla Philippe
Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada.
J Pharmacol Exp Ther. 2005 Oct;315(1):144-54. doi: 10.1124/jpet.105.089045. Epub 2005 Jun 15.
Postsynaptic P2X1 ATP-gated channels are expressed in smooth muscle cells of the vascular and genitourinary systems, where they mediate desensitizing neurogenic contractions. Using the model of the isolated rat tail artery, we show that the vasoactive mediator 5-hydroxytryptamine (5-HT), via the 5-HT2A metabotropic receptor, regulates the desensitization kinetics of P2X1 responses by increasing their rate of recovery. Reconstituting the potentiation of P2X1 ATP-gated currents by 5-HT2A receptors in the Xenopus oocyte expression system, we provide evidence that this modulation depends on the activation of novel protein kinase C isoforms and protein kinase D (also named PKCmu) downstream of phospholipase Cbeta. Other major kinases like Ca2+/calmodulin kinase II, protein kinase A, mitogen-activated protein kinases, and tyrosine kinases were found not to be involved. Moreover, we report that buffering intracellular Ca2+ ions with the chelator 1,2-bis(O-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) decreases the rate of recovery of P2X1 responses and increases their sensitivity to potentiation by 5-HT2A receptors or by the diacylglycerol analog phorbol ester 12-myristate 13-acetate. We conclude that intracellular Ca2+ and a subset of diacylglycerol-dependent protein kinases regulate the activity of P2X1 receptor channels by modulating their recovery from desensitization.
突触后P2X1三磷酸腺苷门控通道在血管和泌尿生殖系统的平滑肌细胞中表达，在这些细胞中它们介导脱敏性神经源性收缩。利用离体大鼠尾动脉模型，我们发现血管活性介质5-羟色胺（5-HT）通过5-HT2A代谢型受体，通过提高P2X1反应的恢复速率来调节其脱敏动力学。在非洲爪蟾卵母细胞表达系统中重建5-HT2A受体对P2X1三磷酸腺苷门控电流的增强作用，我们提供的证据表明，这种调节依赖于磷脂酶Cβ下游新型蛋白激酶C亚型和蛋白激酶D（也称为PKCμ）的激活。发现其他主要激酶如Ca2+/钙调蛋白激酶II、蛋白激酶A、丝裂原活化蛋白激酶和酪氨酸激酶不参与其中。此外，我们报告用螯合剂1,2-双（O-氨基苯氧基）乙烷-N,N,N',N'-四乙酸（BAPTA）缓冲细胞内Ca2+离子会降低P2X1反应的恢复速率，并增加其对5-HT2A受体或二酰基甘油类似物佛波酯12-肉豆蔻酸酯13-乙酸酯增强作用的敏感性。我们得出结论，细胞内Ca2+和二酰基甘油依赖性蛋白激酶的一个子集通过调节P2X1受体通道从脱敏状态的恢复来调节其活性。
