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。 神经递质的异常水平，导致不适当的神经信号，是各种大脑疾病的基础。 例如，癫痫、兴奋性毒性细胞死亡、抑郁症和许多与药物滥用有关的疾病都与大脑中异常的递质水平有关。神经递质转运蛋白是位于神经元和胶质细胞上的蛋白质，其部分功能是将递质从细胞外环境转运到细胞内。 因此，它们在调节突触信号传导中发挥核心作用。 有趣的是，我们知道转运蛋白本身受到许多信号转导级联的调节，部分是通过转运蛋白的亚细胞再分布。 然而，这种调节的机制，信号转导通路如何相互作用，以控制转运蛋白的表达，以及转运蛋白再分布的生理相关性尚未得到彻底的研究。本申请的主要目标是确定调节主要脑GABA转运蛋白GAT 1的运输的信号通路，并评估这种形式的调节的生理相关性。 具体目标1是检验GAT 1再分布通过介导含有神经递质的突触囊泡的再循环的相同机制发生的假设。 具体目标2是测试的假设，信号转导级联调节GAT 1再分配这样做的直接转运蛋白磷酸化和随后的改变率的内吞。 具体目标3将通过检验GAT 1转运的改变调节脑中GABA能信号传导的假设来检查GAT 1再分布调节的生理相关性。这些研究是重要的，因为它们将（i）定义参与转运蛋白运输的细胞机制;（ii）确定调节转运蛋白运输的信号;（iii）确定这种形式的调节的生理相关性;（iv）提供数据，这些数据可能有助于在治疗与异常递质水平相关的疾病时调节转运蛋白功能的策略。

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.