The Neurotransporter Group, Department of Anatomy, Institute of Basic Medical Sciences, University of Oslo , Oslo , Norway.
Front Endocrinol (Lausanne). 2013 Nov 11;4:165. doi: 10.3389/fendo.2013.00165. eCollection 2013.
The mammalian genome contains four genes encoding GABA transporters (GAT1, slc6a1; GAT2, slc6a13; GAT3, slc6a11; BGT1, slc6a12) and five glutamate transporter genes (EAAT1, slc1a3; EAAT2, slc1a2; EAAT3, slc1a1; EAAT4, slc1a6; EAAT5, slc1a7). These transporters keep the extracellular levels of GABA and excitatory amino acids low and provide amino acids for metabolic purposes. The various transporters have different properties both with respect to their transport functions and with respect to their ability to act as ion channels. Further, they are differentially regulated. To understand the physiological roles of the individual transporter subtypes, it is necessary to obtain information on their distributions and expression levels. Quantitative data are important as the functional capacity is limited by the number of transporter molecules. The most important and most abundant transporters for removal of transmitter glutamate in the brain are EAAT2 (GLT-1) and EAAT1 (GLAST), while GAT1 and GAT3 are the major GABA transporters in the brain. EAAT3 (EAAC1) does not appear to play a role in signal transduction, but plays other roles. Due to their high uncoupled anion conductance, EAAT4 and EAAT5 seem to be acting more like inhibitory glutamate receptors than as glutamate transporters. GAT2 and BGT1 are primarily expressed in the liver and kidney, but are also found in the leptomeninges, while the levels in brain tissue proper are too low to have any impact on GABA removal, at least in normal young adult mice. The present review will provide summary of what is currently known and will also discuss some methodological pitfalls.
哺乳动物基因组包含四个编码 GABA 转运体的基因（GAT1，slc6a1；GAT2，slc6a13；GAT3，slc6a11；BGT1，slc6a12）和五个谷氨酸转运体基因（EAAT1，slc1a3；EAAT2，slc1a2；EAAT3，slc1a1；EAAT4，slc1a6；EAAT5，slc1a7）。这些转运体将 GABA 和兴奋性氨基酸的细胞外水平保持在较低水平，并为代谢提供氨基酸。各种转运体在其转运功能和作为离子通道的能力方面都具有不同的特性。此外，它们的表达受到调节。为了了解单个转运体亚型的生理作用，有必要获得有关其分布和表达水平的信息。定量数据很重要，因为功能容量受转运体分子数量的限制。对于大脑中去除递质谷氨酸的最重要和最丰富的转运体是 EAAT2（GLT-1）和 EAAT1（GLAST），而 GAT1 和 GAT3 是大脑中的主要 GABA 转运体。EAAT3（EAAC1）似乎在信号转导中不起作用，但发挥其他作用。由于其高的未偶联阴离子电导，EAAT4 和 EAAT5 似乎更像是抑制性谷氨酸受体，而不是谷氨酸转运体。GAT2 和 BGT1 主要在肝脏和肾脏中表达，但也存在于软脑膜中，而脑组织中的水平太低，不足以对 GABA 的去除产生任何影响，至少在正常年轻成年小鼠中是如此。本综述将提供目前已知的概述，并将讨论一些方法学上的陷阱。
