GABA Transporters: Trafficking and Regulation

大脑中的神经递质水平对正常的大脑功能至关重要。神经递质水平异常，导致不适当的神经信号，是一系列大脑疾病的基础。例如，癫痫、兴奋性毒性细胞死亡、抑郁和许多与药物滥用有关的疾病都与大脑中递质水平异常有关。神经递质转运蛋白是位于神经元和神经胶质细胞上的蛋白质，其部分功能是将递质从细胞外环境输送到细胞内。因此，它们在调节突触信号方面起着核心作用。有趣的是，我们知道转运蛋白本身受到一些信号转导级联反应的调节，部分是通过转运蛋白的亚细胞重新分配。然而，这种调控的机制，信号转导通路如何相互作用来控制转运蛋白的表达，以及转运蛋白重新分布的生理相关性还没有得到彻底的研究。这项应用的主要目标是确定调节大脑主要GABA转运体GAT1运输的信号通路，并评估这种调节形式的生理学相关性。具体目的1是验证GAT1重新分布通过调节含有神经递质的突触小泡循环的相同机制发生的假说。具体目的2是验证这样的假设，即调节GAT1重分布的信号转导级联是通过直接转运体磷酸化和随后内吞速率的改变来实现的。具体目标3将通过检验GAT1转运中的变化调节大脑中的GABAA能信号的假设来检验GAT1再分布调节的生理学相关性。这些研究很重要，因为它们将(I)确定参与转运体贩运的细胞机制；(Ii)确定调节转运体贩运的信号；(Iii)确定这种形式的调节的生理相关性；以及(Iv)提供可用于旨在调节转运体功能的策略中的数据，以治疗与递质水平异常有关的疾病。

Neurotransmitter levels in brain are critical for normal brain function. Abnormal levels of neurotransmitter, resulting in inappropriate neural signaling, underlie a diverse set of brain disorders. For example, epilepsy, excitotoxic cell death, depression, and a number of conditions related to drug abuse are all associated with abnormal transmitter levels in brain. Neurotransmitter transporters are proteins, located on neurons and glia, that function in part to transport transmitter from the extracellular milieu into cells. As such, they play a central role in regulating synaptic signaling. Interestingly, we know that transporters themselves are subject to regulation by a number of signal transduction cascades, in part through a subcellular redistribution of the transporter. However, the mechanisms underlying this regulation, how the signal transduction pathways interact to control transporter expression, and the physiological relevance of transporter redistribution have yet to be thoroughly examined. The major goals of this application are to determine the signalling pathways that regulate trafficking of the predominant brain GABA transporter GAT1, and to evaluate the physiological relevance of this form of regulation. Specific Aim 1 is to test the hypothesis that GAT1 redistribution occurs via the identical mechanisms that mediate the recycling of neurotransmitter- containing synaptic vesicles. Specific Aim 2 is to test the hypothesis that signal transduction cascades which regulate GAT1 redistribution do so by direct transporter phosphorylation and subsequent alterations in rates of endocytosis. Specific Aim 3 will examine the physiological relevance of the regulation of GAT1 redistribution by testing the hypothesis that alterations in GAT1 trafficking regulate GABAergic signaling in brain. These studies are important because they will (i) define the cellular machinery that participates in transporter trafficking; (ii) determine the signals that regulate transporter trafficking; (iii) determine the physiological relevance of this form of regulation; and (iv) provide data that could be useful in strategies aimed at regulating transporter function in the treatment of disorders related to abnormal transmitter levels.