The transient receptor potential Ankyrin 1(TRPA1) cation channel is activated by various pungent and irritant compounds,and it also mediates the perception of noxious cold.Identification of different agonists for this channel is important for understanding its activation mechanism.Therefore,a screen for novel TRPA1 agonists was performed using an agonist-induced calcium influx assay.Out of 90 compounds screened,pinacidil was identified as a novel agonist for this channel.Pinacidil is a known opener of the K atp channel,for which it has an EC50 value of 1-3 μmol/L.In comparison,the EC50 value of pinacidil for TRPA1 is relatively high(260 μmol/L).Recombinant HEK-TRPA1 cells did not respond to P1075,another K atp channel opener,suggesting that the effect of pinacidil on TRPA1 was highly specific.Further studies revealed that the agonist activity of pinacidil could be blocked by the TRP channel inhibitors,ruthenium red and HC-030031.Using glutathione(GSH) and site-specific mutagenesis,we demonstrated that pinacidil could activate TRPA1 by covalent modification of the critical amino acids C619,C639 and C663 in the N-terminus of TRPA1.
MA LiangHuiDENG YingZHANG BiBAI YanQiuCAO JingLI ShiYouLIU JianFeng
脆性X染色体综合征(fragile X syndrome,FXS)是由于fmr1基因沉默导致脆性X精神迟滞蛋白(fragile X mental retardation protein,FMRP)表达不足而引起的一种常见的遗传性精神发育迟滞疾病。除了导致智力障碍外,FXS不同个体在临床还表现出神经发育障碍导致的其它缺陷,如注意力缺陷、多动症、自闭症、语言障碍和攻击性行为等。目前,其治疗手段主要集中在对FMRP调节的下游基因或蛋白信号的恢复和缓解上,但并不能够完全治愈。现有的针对FXS疾病的药物靶点除了I型代谢型谷氨酸受体(metabtropic glutamate receptors,mGluRs)外,近几年研究表明,γ-氨基丁酸(γ-aminobutyric acid,GABA)受体的激动剂也在动物模型和临床实验中表现出显著的效果。本文就GABA受体在FXS中的作用进展进行综述。
G-protein coupled receptors （GPCRs） class C represent a distant group among the large family of GPCRs. This class includes the receptors for the main neurotransmitters, glutamate and gamma-aminobutyric acid （GABA）, and the receptors for Ca2＋, some taste and pheromone molecules, as well as some orphan receptors. Like any other GPCRs, these receptors possess a heptahelical domain （HD） involved in heterotrimeric G-protein activation, but most of them also have a large extracellular domain （VFT） responsible for agonist recognition and binding. These receptors are dimers, either homo or heterodimers. Then whereas have mGluRs is homodimers, GABAB receptor was the first heteromeric G-protein coupled receptor （GPCR） identified. Indeed, both GB1 and GB2 subunits appear necessary to get a functional GABAB receptor. We have demonstrated that the interactions be- tween VFT domain of both GB1 and GB2 were important for receptor activation. We have also shown the dynamic movement of trans-membrane of mGluRs within dimers. Then we have found that the GABAB receptor induced acti- vation of ERK1/2/CREB and protected neurons from apoptosis by trans-activating IGF-1R. We have also demon- strated that GABAB receptor activation has been modulated by the dynamic protein-protein interactions between re- ceptors and its downstream signal proteins such as FAK1 and Rap l. Finally, we have performed the HTS screening and found the first negative allosteric modulator for GABAB receptors.
