Insights into the Regulation of the Glycine Transporter 1 (GlyT1)

描述（由申请人提供）：甘氨酸是脑干和脊髓中的主要抑制性神经递质，在那里它在特异性士的宁敏感性甘氨酸受体处起作用。此外，甘氨酸在含有N-甲基-D-天冬氨酸（NMDA）受体的突触中作为谷氨酸的重要共激动剂参与兴奋性神经传递;因此，NMDA受体激活受到突触前神经元和邻近神经胶质细胞中存在的质膜甘氨酸转运蛋白1（GlyT 1）活性的紧密调节。功能性NMDA受体数量的改变被认为是精神分裂症的一些症状的基础，主要是认知功能。GlyT 1一直是精神分裂症药物开发的主要目标;然而，转运蛋白如何调节仍然知之甚少。已知单胺转运蛋白家族的几个成员的转运活性与蛋白激酶C（PKC）的活化有关;然而，在脑中的调节机制是有争议的或未知的。鉴于临床和药理学数据表明精神分裂症中谷氨酸受体功能障碍的强度以及甘氨酸转运蛋白作为潜在药物靶点的作用，在本研究中，我们的目标是使用两种表达系统表征GlyT 1的调节机制：（a）在模型细胞系中表达的小鼠GlyTIa（HeLa和猪主动脉内皮细胞，PAE）和（B）来自大鼠海马的原代培养物中的内源性GlyT 1。基于我们实验室的初步数据，表明增强PKC依赖的泛素化和内吞作用获得表达GlyT 1在HeLa细胞中，我们假设PKC激活结果GlyT 1泛素化和下调在大脑中，有助于调节甘氨酸转运蛋白。这项研究将为治疗精神分裂症等神经系统疾病提供新的潜在药理学靶点。

DESCRIPTION (provided by applicant): Glycine is the major inhibitory neurotransmitter in the brainstem and spinal cord, where it functions at specific strychnine-sensitive glycine receptors. In addition, glycine participates in excitatory neurotransmission as an essential co-agonist of glutamate at N-methyl-D-aspartate (NMDA) receptor containing synapses; therefore, NMDA receptor activation is tightly modulated by the activity of the plasma membrane glycine transporter 1 (GlyT1) present in presynaptic neurons and neighboring glial cells. Altered numbers of functional NMDA receptors have been suggested to underlie some of the symptoms in schizophrenia, primarily in cognitive functions. The GlyT1 has been the main target for drug development in schizophrenia; however, how the transporter is regulated remains poorly understood. It is known for several members of the monoamine transporter family that transport activity is linked to activation of Protein Kinase C (PKC); however, the mechanism of regulation is controversial or unknown in the brain. Given the strength of clinical and pharmacological data suggesting glutamate receptor dysfunction in schizophrenia and the role of the glycine transporter as a potential drug target, in this study our goal is to characterize the regulatory mechanism of the GlyT1 using two expression systems: (a) mouse GlyTIa expressed in model cell lines (HeLa and Porcine Aortic Endothelial cells, PAE) and (b) endogenous GlyT1 in primary cultures from rat hippocampus. Based on preliminary data from our laboratory that suggest enhanced PKC-dependent ubiquitination and endocytosis obtained by expressing GlyT1 in HeLa cells, we hypothesize that PKC activation results in GlyT1 ubiquitination and down-regulation in the brain, contributing to the regulation of the glycine transporter. This research will offer new potential pharmacological targets to treat neurological disorders, such as schizophrenia.