Tang Jing-shu, Xie Bing-xue, Bian Xi-ling, Xue Yu, Wei Ning-ning, Zhou Jing-heng, Hao Yu-chen, Li Gang, Zhang Liang-ren, Wang Ke-wei
Shenzhen-Peking University-The Hong Kong University of Science and Technology Medical Center, Shenzhen 518036, China.
Department of Medicinal Chemistry, State Key Laboratory of Natural and Biomimetic Drugs, Peking University, Beijing 100191, China.
Acta Pharmacol Sin. 2015 Jul;36(7):800-12. doi: 10.1038/aps.2015.9. Epub 2015 Apr 27.
Alpha7-nicotinic acetylcholine receptor (α7 nAChR) is a ligand-gated Ca(2+)-permeable ion channel implicated in cognition and neuropsychiatric disorders. Activation of α7 nAChR improves learning, memory, and sensory gating in animal models. To identify novel α7 nAChR agonists, we synthesized a series of small molecules and characterized a representative compound, Br-IQ17B, N-[(3R)-1-azabicyclo[2,2,2]oct-3-yl]-5-bromoindolizine-2-carboxamide, which specifically activates α7 nAChR.
Two-electrode voltage clamp (TEVC) recordings were primarily used for screening in Xenopus oocytes expressing human α7 nAChR. Assays, including radioisotope ligand binding, Western blots, whole-cell recordings of hippocampal culture neurons, and spontaneous IPSC recordings of brain slices, were also utilized to evaluate and confirm the specific activation of α7 nAChR by Br-IQ17B.
Br-IQ17B potently activates α7 nAChR with an EC50 of 1.8±0.2 μmol/L. Br-IQ17B is selective over other subtypes such as α4β2 and α3β4, but it blocks 5-HT3A receptors. Br-IQ17B displaced binding of the α7 blocker [(3)H]-MLA to hippocampal crude membranes with a Ki of 14.9±3.2 nmol/L. In hippocampal neurons, Br-IQ17B evoked α7-like currents that were inhibited by MLA and enhanced in the presence of the α7 PAM PNU-120596. In brain slice recordings, Br-IQ17B enhanced GABAergic synaptic transmission in CA1 neurons. Mechanistically, Br-IQ17B increased ERK1/2 phosphorylation that was MLA-sensitive.
We identified the novel, potent, and selective α7 agonist Br-IQ17B, which enhances synaptic transmission. Br-IQ17B may be a helpful tool to understand new aspects of α7 nAChR function, and it also has potential for being developed as therapy for schizophrenia and cognitive deficits.
α7-烟碱型乙酰胆碱受体（α7 nAChR）是一种配体门控的Ca(2+)通透性离子通道，与认知和神经精神疾病有关。在动物模型中，α7 nAChR的激活可改善学习、记忆和感觉门控。为了鉴定新型α7 nAChR激动剂，我们合成了一系列小分子，并对一种代表性化合物Br-IQ17B，即N-[(3R)-1-氮杂双环[2,2,2]辛-3-基]-5-溴中氮茚-2-甲酰胺进行了表征，该化合物可特异性激活α7 nAChR。
主要采用双电极电压钳（TEVC）记录法在表达人α7 nAChR的非洲爪蟾卵母细胞中进行筛选。还利用了包括放射性同位素配体结合、蛋白质免疫印迹、海马培养神经元的全细胞记录以及脑片的自发性抑制性突触后电流（sIPSC）记录等实验，来评估和确认Br-IQ17B对α7 nAChR的特异性激活作用。
Br-IQ17B能有效激活α7 nAChR，其半数有效浓度（EC50）为1.8±0.2 μmol/L。Br-IQ17B对其他亚型如α4β2和α3β4具有选择性，但它会阻断5-HT3A受体。Br-IQ17B以14.9±3.2 nmol/L的解离常数（Ki）取代了α7阻断剂[(3)H]-MLA与海马粗膜的结合。在海马神经元中，Br-IQ17B诱发了类似α7的电流，该电流被MLA抑制，并在α7正变构调节剂（PAM）PNU-120596存在时增强。在脑片记录中，Br-IQ17B增强了CA1神经元中的GABA能突触传递。从机制上讲，Br-IQ17B增加了对MLA敏感的细胞外信号调节激酶1/2（ERK1/2）的磷酸化。
我们鉴定出了新型、强效且具有选择性的α7激动剂Br-IQ17B，它可增强突触传递。Br-IQ17B可能是理解α7 nAChR功能新方面的有用工具，并且它也有开发成为治疗精神分裂症和认知缺陷药物的潜力。
