Canonical Transient Receptor Potential (TRPC) subfamily function in Hippocampus.

描述(申请人提供)：离子通道亚单位的典型瞬时受体潜力家族由7个不同的基因产物(TRPC1-7)组成，其中大部分在中枢神经系统中表达。这一类的三个亚家族成员(TRPC1、TRPC4和TRPC5)在海马区高表达。这些离子通道亚基形成具有不同特征的同质和异质通道。此外，磷脂酶C通过G蛋白偶联受体亚型和酪氨酸激酶受体亚型激活或增强由这些蛋白介导的电流。特别是，与GQ/11相关的受体，如1型代谢性谷氨酸和M1、M3和M5受体，通过改变质膜PIP2和增加细胞内钙离子浓度来激活这些电流。TRPC1/4/5亚家族在海马区的功能尚不清楚。我们假设，海马体功能是由激活或增强这些兴奋性离子通道的受体调节的。我们已经培育出缺乏TRPC4、TRPC5、TRPC4和TRPC5基因的小鼠，获得了TRPC1基因敲除小鼠，并正在培育TRPC1/4/5三重敲除小鼠。在这里，我们建议使用这些小鼠通过蛋白质定位、行为学研究、海马区急性脑片记录和分离的海马神经元记录来了解这些离子通道在海马区的功能。这些研究的结果应该阐明受体介导的海马体介导的空间和上下文记忆的改变，并确定影响海马体的疾病和手术的新的治疗靶点。 与公共健康相关：长期记忆和空间导航依赖于海马体的功能，海马体是大脑中位于皮质表面之下的一大片区域。缺氧、脑炎、内侧颞叶癫痫、肿瘤和阿尔茨海默病对海马体的损伤可能会导致健忘症，即无法形成或保留新的记忆。海马体(和大脑)的基本功能单位是高度可修改的突触，一个神经元将信息传递给另一个神经元的点。突触被赋予了密集的蛋白质阵列，从而实现了一系列的调节影响。在调节突触功能的蛋白质中，最重要的是离子通道。这些蛋白质的功能是启动和控制从一个突触到另一个突触的信息流，特别是启动控制神经递质释放的细胞内钙的变化。海马区突触功能所必需的离子通道在很大程度上是已知的。鲜为人知的是被称为Trp通道的调节性离子通道的功能。这些离子通道被特殊类别的受体激活，并允许钙直接流入神经元。在这份提案中，我们概述了我们将如何确定由TRPC1、TRPC4和TRPC5组成的TRPC通道亚基的规范亚家族的功能。目前还没有专门阻断这些通道的药物。我们有缺乏所有这些基因的转基因小鼠，以及缺乏所有3个基因组合的小鼠。我们将对这些转基因小鼠进行实验，以了解海马体功能的变化，这是通过对正常表达这些通道的神经元的行为研究和详细的电生理研究确定的。这类研究的长期实际好处是更好地了解海马体的工作原理，并确定潜在的新治疗靶点，这些靶点可能用于改善发育过程中发生的学习和记忆障碍、出生时缺氧、中枢神经系统手术和癌症以及阿尔茨海默氏症等情况。

DESCRIPTION (provided by applicant): The Canonical Transient Receptor Potential family of ion channel subunits comprise 7 distinct gene products (TRPC1-7), most of which are expressed in the central nervous system. Three subfamily members of this class (TRPC1, TRPC4, and TRPC5) are highly expressed in the hippocampus. These ion channel subunits forms homomeric and heteromeric channels with distinct characteristics. In addition, the currents mediated by these proteins are activated or potentiated by phospholipase C via subtypes of G protein-coupled receptors and tyrosine kinase receptors. In particular, Gq/11-linked receptors such as the type 1 metabotropic glutamate and M1, M3, and M5 muscarinic receptors, activate these currents by altering plasma membrane PIP2 and increasing intracellular Ca2+ concentrations. The function of the TRPC1/4/5 subfamily in hippocampus is not known. We hypothesize that hippocampal function is modulated by receptors that activate or potentiate these excitatory ion channels. We have generated mice lacking the TRPC4, TRPC5, both TRPC4 and TRPC5 genes, obtained the TRPC1 knockout mouse, and are breeding TRPC1/4/5 triple knockout mice. Here we propose to use these mice to understand the function of these ion channels in the hippocampus using protein localization, behavioral studies, acute brain slice recordings of hippocampus, and recordings of isolated hippocampal neurons. The results of these studies should clarify receptor-mediated alteration of hippocampal-mediated spatial and contextual memory, and identify new therapeutic targets for diseases and surgeries that affect the hippocampus. PUBLIC HEALTH RELEVANCE: Long term memory and spatial navigation rely upon the function of the hippocampus, a large region of the brain located beneath the cortical surface. Damage to the hippocampus, from oxygen starvation, encephalitis, medial temporal lobe epilepsy, tumors, and Alzheimer's disease, may result in amnesia, the inability to form or retain new memories. The basic functional unit of the hippocampus (and brain) is the richly modifiable synapse, the point where one neuron passes information to another. Synapses are endowed with a dense array of proteins that enable a panoply of modulatory influences. Foremost among the proteins that mediate synaptic function are ion channels. The function of these proteins is to initiate and control information flow from one synapse to another, and in particular, to initiate changes in intracellular calcium that control neurotransmitter release. The ion channels that are absolutely required for synaptic function in the hippocampus are largely known. Less well known are the functions of modulatory ion channels, known as TRP channels. These ion channels are activated by special classes of receptors and allow calcium to flow directly into neurons. In this proposal, we outline how we will determine the function of the canonical subfamily of TRPC channel subunits comprised of TRPC1, TRPC4, and TRPC5. Currently there are no pharmacological agents that specifically block these channels. We have genetically modified mice that lack each of these genes, as well as mice lacking combinations of all 3 of the genes. We will conduct experiments with these genetically modified mice in order to understand changes in function of the hippocampus, as determined by behavioral studies and detailed electrophysiological studies of the neurons normally expressing these channels. The long term practical benefit of such studies is to better understand how the hippocampus works, as well as define potentially new therapeutic targets that may be used to ameliorate conditions such as learning and memory deficits that occur in development, oxygen starvation during birth, central nervous system surgeries and cancers, and Alzheimer's disease.