Modulation of Na+ ,K+ pumping and neurotransmitter uptake by β-amyloid
Modulation of Na+ ,K+ pumping and neurotransmitter uptake by β-amyloid
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DOI：
10.1016/j.neuroscience.2004.03.032
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发表时间：
2004-01-01
期刊：
影响因子：
3.3
通讯作者：
Schwarz, W
中科院分区：
文献类型：
--
作者：
Gu, QB;Zhao, JX;Schwarz, W
微摩尔浓度的β-淀粉样蛋白（Abeta），淀粉样蛋白前体蛋白的40/42-氨基酸长的蛋白水解片段（Abeta（1-40/42）），先前被证明在阿尔茨海默病的发病机制中起关键作用。我们使用非洲爪蟾卵母细胞表达系统研究微摩尔浓度的Abeta（1-42）对γ-氨基丁酸（GABA）、GAT 1和兴奋性氨基酸谷氨酸（EAAC 1）的神经递质转运蛋白的特异性影响，这些转运蛋白由Na+，K+-ATP酶调节的跨膜Na+梯度驱动。用Abeta（1-42）短暂处理，长达80分钟，导致Na+，K+-ATP酶对离子易位的显著抑制（30-40%）;谷氨酸摄取也被抑制（20%），而GABA摄取不受影响。由于谷氨酸摄取减少将导致细胞外谷氨酸的神经毒性浓度升高，因此我们更详细地研究了Abeta（1-42）和较小片段Abeta（12-28）和Abeta（25-35）对EAAC 1的影响。在1 μ M Abeta（1-42）中长时间孵育导致对谷氨酸摄取和EAAC 1介导的电流的进一步强烈抑制（4小时后抑制量超过80%）。Abeta（12-28）在20 μ M下孵育4小时后的抑制率为50%，效果较差。Abeta（1-42）和Abeta（12-28）影响EAAC 1介导的电流的程度与谷氨酸摄取速率相似。如果应用Abeta较长时间，则对EAAC 1介导的电流的影响是不可逆的。直接显微注射到卵母细胞中的肽是无效的，这表明所观察到的效果是由细胞外蛋白介导的。Abeta（25-35）几乎不影响EAAC 1介导的电流或谷氨酸摄取。结果表明，Abeta特异性地抑制Na+，K+泵和EAAC 1。Abeta的氨基酸12和28之间的结构域似乎对EAAC 1的抑制起关键作用。神经毒性、细胞外谷氨酸水平升高对EAAC 1的抑制可能有助于阿尔茨海默病的发病机制。(C)2004年IBRO。由爱思唯尔有限公司出版。保留所有权利。
Micromolar concentrations of beta-amyloid (Abeta), a 40/42-amino-acid-long proteolytic fragment (Abeta(1-40/42)) of the amyloid precursor protein, was shown previously to play a crucial role in pathogenesis of Alzheimer's disease. We used the Xenopus oocyte expression system to investigate specific effects of micromolar concentrations of Abeta(1-42) on the neurotransmitter transporters for gamma-aminobutyric acid (GABA), GAT1, and for the excitatory amino acid glutamate, EAAC1, which are driven by the transmembrane Na+ gradient that is regulated by the Na+,K+-ATPase. Brief treatment with Abeta(1-42), up to 80 min, leads to a significant inhibition of ion translocation by the Na+, K+-ATPase (30-40%); also glutamate uptake is inhibited (20%) while GABA uptake is not affected. Since reduced glutamate uptake will result in elevated, neurotoxic concentrations of extracellular glutamate, we investigated the effects of Abeta(1-42) and the smaller fragments, Abeta(12-28) and Abeta(25-35), on EAAC1 in more detail. Prolonged incubation in 1 muM Abeta(1-42) leads to further, strong inhibition of glutamate uptake and EAAC1-mediated current (after 4 h inhibition amounts to more than 80%). Abeta(12-28) is less effective with 50% inhibition after 4 h of incubation at 20 muM. Abeta(1-42) and Abeta(12-28) affect EAAC1-mediated current to a similar extent as the rate of glutamate uptake. The effects on EAAC1-mediated current are irreversible if Abeta were applied for longer time periods. Peptides directly microinjected into the oocyte are ineffective suggesting that the observed effect were mediated by extracellular proteins. Abeta(25-35) hardly affects EAAC1-mediated current or glutamate uptake.The results demonstrate that Abeta specifically inhibits the Na+,K+ pump and EAAC1. The domain between amino acids 12 and 28 of Abeta seems to play a crucial role for inhibition of EAAC1. The inhibition of EAAC1 by neurotoxic, elevated extracellular glutamate levels may contribute to Alzheimer's pathogenesis. (C) 2004 IBRO. Published by Elsevier Ltd. All rights reserved.