Localization and functional relevance of system A neutral amino acid transporters in cultured hippocampal neurons
Localization and functional relevance of system A neutral amino acid transporters in cultured hippocampal neurons
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DOI：
10.1074/jbc.m110942200
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发表时间：
2002-03-22
影响因子：
4.8
通讯作者：
Matteoli, M
中科院分区：
文献类型：
--
作者：
Armano, S;Coco, S;Matteoli, M
谷氨酰胺和丙氨酸是合成谷氨酸的重要前体。这些氨基酸由邻近的星形胶质细胞提供给神经元，并被经典系统 A 氨基酸载体内化。特别是，系统 A 转运蛋白 (SAT1) 是一种高效的谷氨酰胺转运蛋白，而 SAT2 对中性氨基酸表现出广泛的特异性，并优先选择丙氨酸。我们研究了 SAT1 和 SAT2 在海马神经元原代培养物中的定位和功能相关性。这两种载体从早期发育阶段就开始表达，并且均匀分布在所有神经元过程中。然而，虽然 SAT1 存在于轴突生长锥中，并且可以在发育后期的突触接触位点检测到，但 SAT2 似乎在这些区室中没有显着表达。不可代谢的氨基酸类似物 α-(甲基氨基)-异丁酸是系统 A 载体的竞争性抑制剂，可显着降低星形胶质细胞顶部生长的神经元的微型兴奋性突触后电流幅度，在纯神经元培养物中无效。 α-(甲基氨基)-异丁酸不会改变神经元对谷氨酸的反应性，因此排除了突触后效应。这些数据表明，系统A载体在海马神经元中以不同的亚细胞分布表达，并且在控制星形胶质细胞介导的谷氨酸能神经元与神经递质前体的供应中发挥着至关重要的作用。
Glutamine and alanine are important precursors for the synthesis of glutamate. Provided to neurons by neighboring astrocytes, these amino acids are internalized by classical system A amino acid carriers. In particular, System A transporter (SAT1) is a highly efficient glutamine transporter, whereas SAT2 exhibits broad specificity for neutral amino acids with a preference for alanine. We investigated the localization and the functional relevance of SAT1 and SAT2 in primary cultures of hippocampal neurons. Both carriers have been expressed since early developmental stages and are uniformly distributed throughout all neuronal processes. However, whereas SAT1 is present in axonal growth cones and can be detected at later developmental stages at the sites of synaptic contacts, SAT2 does not appear to be significantly expressed in these compartments. The non-metabolizable amino acid analogue alpha-(methylamino)-isobutyric acid, a competitive inhibitor of system A carriers, significantly reduced miniature excitatory postsynaptic current amplitude in neurons growing on top of astrocytes, being ineffective in pure neuronal cultures. alpha-(Methylamino)-isobutyric acid did not alter neuronal responsitivity to glutamate, thus excluding a postsynaptic effect. These data indicate that system A carriers are expressed with a different subcellular distribution in hippocampal neurons and play a crucial role in controlling the astrocyte-mediated supply of glutamatergic neurons with neurotransmitter precursors.