Calcium-sensing Receptor Signaling and Epilepsy

描述（由申请人提供）： 细胞外钙敏感受体（CaSR）广泛分布于脑中，通过外部钙浓度（[Ca 2 +]o）的变化来调节，并以多种方式影响神经元活动。除了抑制神经末梢中的非选择性阳离子通道、抑制动作电位诱发的递质释放和刺激自发神经传递（所有这些都可能改变癫痫发作发生的倾向）之外，还提出CaSR转导钙介导的神经元兴奋性变化。需要解决的问题是，CaSR信号变化导致神经元活动变化的详细机制是什么？CaSR激活是否影响癫痫发作？此外，作为本提案的一部分，我们将确定：1）CaSR激活是否同等地影响自发和诱发传递，2）CaSR信号传导是否是介导神经元兴奋性[Ca 2 +] o依赖性变化的途径，以及3）这些变化中的哪一种可能介导CaSR激动剂的抗癫痫作用？假设CaSR是一种G蛋白偶联受体（GPCR），是新型抗癫痫药物的重要靶点。该项目旨在验证这一假设，并使用以下四部分方法确定CaSR突变影响CaSR信号传导和神经元活动的机制。首先，将确定野生型和突变型CaSR如何影响新皮层神经元响应[Ca 2 +]o变化的兴奋性。这些实验将采用来自表达wt CaSR的单个神经元的生物物理测量。其次，我们将使用直接记录从神经末梢，以确定是否在终端和索马使用相同的机制CaSR信号。第三，我们将确定CaSR信号传导如何影响神经元-神经元通信。在这里，实验将允许在抑制性和兴奋性突触的诱发和自发传输的CaSR信号的影响进行比较。第四，我们将评估CaSR激动剂是否在两种小鼠模型中减少癫痫发作。这项提案的成功完成将通过增加我们对大脑中钙调节的理解，并扩大我们对CaSR信号如何用于治疗癫痫和其他形式癫痫发作的理解，对该领域产生重大影响。

DESCRIPTION (provided by applicant): The extracellular calcium-sensing receptor (CaSR) is widely distributed in the brain, is modulated by changes in the external calcium concentration ([Ca2+]o), and impacts neuronal activity in a number of ways. In addition to inhibiting a non-selective cation channel in nerve terminals, inhibiting action potential evoked transmitter release, and stimulating spontaneous neurotransmission, all of which may change the predisposition for seizures to occur, it has also been proposed that CaSR transduces calcium-mediated changes in neuronal excitability. The questions to be addressed are, what are the detailed mechanisms by which CaSR signaling change result in changes of neuronal activity and does CaSR activation impact seizures? In addition as part of this proposal we will determine: 1) if CaSR activation impacts spontaneous and evoked transmission equally, 2) if CaSR signaling is the pathway that mediates [Ca2+]o-dependent changes in neuronal excitability, and 3) which of these changes is likely to mediate an antiepileptic action of CaSR agonists? The hypothesis is that CaSR, a G-protein coupled receptor (GPCR), is an important target for novel antiepileptic drugs. The proposed project is designed to test this hypothesis and determine the mechanism by which the CaSR mutations affect CaSR signaling and neuronal activity using the following four-part approach. First, it will be determined how wild-type and mutant CaSR affect the excitability of neocortical neurons in response to changes in [Ca2+]o. These experiments will employ biophysical measurements from single neurons that are expressing wt CaSR. Second we will use direct recordings from nerve terminals to determine if CaSR signaling at the terminal and soma use the same mechanisms. Third we will determine how CaSR signaling impacts neuron-neuron communication. Here experiments will allow comparison of the effects of CaSR signaling on evoked and spontaneous transmission at inhibitory and excitatory synapses. Fourth we will evaluate if CaSR agonists reduce seizures in two mouse models. Successful completion of this proposal will substantially impact the field by increasing our understanding of calcium regulation in the brain and expanding our understanding of how CaSR signaling might be utilized to treat epilepsy and other forms of seizures.