Vesicular uptake and exocytosis of L-aspartate is independent of sialin.
Vesicular uptake and exocytosis of L-aspartate is independent of sialin.
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L-天冬氨酸的囊泡摄取和胞吐作用不依赖于唾液酸蛋白。
DOI：
10.1096/fj.12-206300
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
Gundersen,Vidar
中科院分区：
文献类型：
--
作者：
Morland,Cecilie;Nordengen,Kaja;Larsson,Max;Prolo,LauraM;Farzampour,Zoya;Reimer,RichardJ;Gundersen,Vidar
L-天冬氨酸作为中枢神经递质的释放机制和作用存在争议。 L-天冬氨酸的囊泡释放机制一直难以证明，因为直到发现唾液酸蛋白在重配成脂质体时可以转运L-天冬氨酸和L-谷氨酸之前，尚未鉴定出囊泡L-天冬氨酸转运蛋白。我们试图通过将分离的突触小泡中的 L-天冬氨酸摄取研究与海马切片的免疫细胞化学研究相结合来阐明 L-天冬氨酸的释放机制以及唾液酸蛋白在此过程中的作用。我们发现放射性标记的 L-天冬氨酸被吸收到突触小泡中。相对于 L-谷氨酸的摄取，海马中的囊泡 L-天冬氨酸摄取量是全脑、纹状体、内嗅和额叶皮质的两倍，并且不受 L-谷氨酸的抑制。我们进一步表明，唾液酸蛋白对于 L-天冬氨酸的胞吐作用不是必需的，因为唾液酸蛋白敲除小鼠和野生型小鼠的突触小泡中 ATP 依赖性 L-天冬氨酸摄取没有差异。此外，PC12细胞中唾液酸蛋白的表达不会导致囊泡对L-天冬氨酸的显着摄取，并且在唾液酸蛋白敲除小鼠和野生型小鼠的海马切片中，去极化诱导的海马神经末梢L-天冬氨酸的消耗是相似的。此外，没有证据表明 L-天冬氨酸通过体积调节阴离子通道或质膜兴奋性氨基酸转运蛋白进行非囊泡释放。这表明L-天冬氨酸在通过唾液酸蛋白以外的转运蛋白在囊泡积聚后从神经末梢胞吐释放。-Morland, C.、Nordengen, K.、Larsson, M.、Prolo, L. M.、Farzampour, Z.、Reimer, R. J.、Gundersen, V. L-天冬氨酸的囊泡摄取和胞吐作用独立于唾液酸蛋白。
The mechanism of release and the role of l-aspartate as a central neurotransmitter are controversial. A vesicular release mechanism for l-aspartate has been difficult to prove, as no vesicular l-aspartate transporter was identified until it was found that sialin could transport l-aspartate and l-glutamate when reconstituted into liposomes. We sought to clarify the release mechanism of l-aspartate and the role of sialin in this process by combining l-aspartate uptake studies in isolated synaptic vesicles with immunocyotchemical investigations of hippocampal slices. We found that radiolabeled l-aspartate was taken up into synaptic vesicles. The vesicular l-aspartate uptake, relative to the l-glutamate uptake, was twice as high in the hippocampus as in the whole brain, the striatum, and the entorhinal and frontal cortices and was not inhibited by l-glutamate. We further show that sialin is not essential for exocytosis of l-aspartate, as there was no difference in ATP-dependent l-aspartate uptake in synaptic vesicles from sialin-knockout and wild-type mice. In addition, expression of sialin in PC12 cells did not result in significant vesicle uptake of l-aspartate, and depolarization-induced depletion of l-aspartate from hippocampal nerve terminals was similar in hippocampal slices from sialin-knockout and wild-type mice. Further, there was no evidence for nonvesicular release of l-aspartate via volume-regulated anion channels or plasma membrane excitatory amino acid transporters. This suggests that l-aspartate is exocytotically released from nerve terminals after vesicular accumulation by a transporter other than sialin.—Morland, C., Nordengen, K., Larsson, M., Prolo, L. M., Farzampour, Z., Reimer, R. J., Gundersen, V. Vesicular uptake and exocytosis of l-aspartate is independent of sialin.
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