Subunit dependent properties of kainate receptors

描述(申请人提供)：红藻氨酸受体是谷氨酸门控离子通道，在中枢神经系统中介导突触传递和调节细胞兴奋性。它们通过参与行为相关频率的海马神经元节律振荡的产生来促进认知过程。海人藻酸受体还与许多神经系统疾病有关，包括颞叶癫痫、精神分裂症、自闭症和神经病理性疼痛。针对这些受体的新疗法的合理开发依赖于对它们功能的更好理解。红藻氨酸受体是四聚体，由低亲和力的GluR5-7和高亲和力的KA1和Ka2亚基组成。褐藻土受体的功能特性取决于它们的亚基组成。特别是，含有Ka2的海人藻酸受体在神经元兴奋中发挥着独特的作用。含Ka2的海人藻酸受体上的电流比不含Ka2的海人酸受体上的电流表现出更高的电导和更慢的衰减。此外，含有KA2的海人藻酸受体通过非典型的代谢性作用增强神经元的兴奋性。可能是因为它们在神经元兴奋中的重要性，含有Ka2亚单位的受体对包括质子、多胺和锌在内的各种内源性物质的调节表现出显著的敏感性。虽然最近的研究已经阐明了含有Ka2的海人酸受体在生理条件下的作用，但关于海人酸受体亚单位的表达或这些受体在疾病中的功能作用如何变化，人们知之甚少。长期以来，海人藻酸受体一直被认为与颞叶癫痫的发病机制有关。更好地了解红藻氨酸受体的性质和调控在颞叶癫痫中是如何改变的，将为设计这种疾病的新疗法提供有价值的信息。本项目将研究KA2亚单位在海人酸受体中在生理条件和癫痫中的作用。目的1将使用重组受体来确定KA2亚基对红藻氨酸受体的功能贡献。目的2将利用慢病毒载体和药物来确定Ka2亚单位表达的变化对KAR介导的神经传递的影响。目的应用实时荧光定量定量聚合酶链式反应(QRT-PCR)和免疫组织化学方法检测匹罗卡品致癫痫持续状态(SE)后大鼠海马区KAR亚单位RNA和蛋白表达的变化。然后，海马片电生理学结合药理学药物和慢病毒载体，将确定SE诱导的亚单位表达的变化如何在这些相同的时间点改变红藻氨酸受体的功能特性。与公共健康相关：海人藻酸受体是谷氨酸门控离子通道，对突触传递至关重要，可导致神经疾病，如颞叶癫痫、精神分裂症、自闭症和神经病理性疼痛。本研究的目的是研究这些受体的亚基依赖特性，以及亚基组成的变化对海马区功能的影响。更好地了解红藻氨酸受体的特性对于合理开发针对这些受体的新型治疗药物是至关重要的。

DESCRIPTION (provided by applicant): Kainate receptors are glutamate-gated ion channels that mediate synaptic transmission and regulate cellular excitability in the central nervous system. They contribute to cognitive processing by participating in the generation of rhythmic oscillations of hippocampal neurons at behaviorally relevant frequencies. Kainate receptors have also been implicated in a number of neurological disorders including temporal lobe epilepsy, schizophrenia, autism, and neuropathic pain. Rational development of novel therapies targeting these receptors depends upon a better understanding of their function. Kainate receptors are tetrameric and comprised of low affinity GluR5-7 and high affinity KA1 and KA2 subunits. Functional properties of kainite receptors depend upon their subunit composition. In particular, KA2-containing kainate receptors play a distinctive role in neuronal excitation. Current at KA2-containing kainate receptors exhibits a higher conductance and slower decay than that at KA2-lacking kainate receptors. In addition, KA2-containing kainate receptors enhance intrinsic neuronal excitability through a noncanonical metabotropic action. Perhaps because of their importance in neuronal excitation, receptors containing the KA2 subunit exhibit significantly increased sensitivity to modulation by a variety of endogenous agents, including protons, polyamines and zinc. While recent studies have shed light on the roles of KA2-containing kainate receptors in physiological conditions, little is known about how the expression of kainate receptor subunits or the functional role of these receptors changes in disease. Kainate receptors have long been implicated in mechanisms underlying temporal lobe epilepsy. A better understanding of how the properties and regulation of kainate receptors change in temporal lobe epilepsy would provide valuable information in the design of novel therapies for this disease. This project will examine the role of the KA2 subunit in kainate receptors in physiological conditions and in epilepsy. Aim 1 will use recombinant receptors to define the functional contribution of KA2 subunits to kainate receptors. Aim 2 will use lentiviral vectors and pharmacological agents to determine the effect of changes in KA2 subunit expression on KAR-mediated neurotransmission. Aim 3 will use quantitative real time qRT-PCR and immunohistochemistry to determine the time course of changes in KAR subunit RNA and protein in the hippocampus during the development of epilepsy after pilocarpine-induced status epilepticus (SE). Hippocampal slice electrophysiology combined with pharmacological agents and lentiviral vectors will then define how SE-induced alterations in subunit expression change functional properties of kainate receptors at these same time points. PUBLIC HEALTH RELEVANCE: Kainate receptors are glutamate-gated ion channels that are critical for synaptic transmission and can contribute to neurological diseases, such as temporal lobe epilepsy, schizophrenia, autism, and neuropathic pain. The goals of this study are to examine subunit dependent properties of these receptors and the impact of changes in subunit composition on hippocampal function. A better understanding of kainate receptor properties is essential in the rational development of novel therapeutic agents targeted at these receptors.