CaMKII and Neuronal Excitability Changes in Learning

描述(申请人提供)：拟议实验的目标是了解钙/钙调素依赖的蛋白激酶II(CaMKII)在调节海马神经元兴奋性的学习相关变化中的功能作用。众所周知，CaMKII是学习和记忆所必需的关键分子。以前的遗传学和药理学研究已经提供了CaMKII依赖的突触强度在学习过程中改变的证据，尽管人们对CaMKII在神经元兴奋性调节中的作用知之甚少，神经元兴奋性是学习和记忆的另一种重要细胞机制。神经元的兴奋性主要由离子通道的特性决定：特别是K+通道是调节神经元膜兴奋性的关键成分。有待检验的工作假说是，CaMKII不仅控制海马区突触的可塑性，而且还调节K+通道的特性，这是学习和记忆巩固过程中海马神经元兴奋性增加的原因。对AlphaCaMKII突变小鼠的分析将确定CaMKII作为负责学习相关兴奋性变化的分子成分所起的作用。我们将使用的突变小鼠是一只在αCaMKII基因(T286A)的自动磷酸化位点上携带点突变的小鼠，因此失去了这种激酶的功能。本研究将阐明αCaMKII在CA1区锥体神经元兴奋性增加中的作用，这表现为在获得海马依赖的联想学习(示踪眨眼条件作用)和空间学习(水迷宫)任务时后超极化(AHP)减少。全细胞电压钳记录将确定外向钾电流的哪些成分(SlAHP、IAHP、IM、IC、IA或IH)在αCaMKII介导的CA1神经元兴奋性调节中发挥关键作用。我们用行为、生物物理、生化和药物遗传学方法对αCaMKII T2sBA突变体进行的综合分析将评估αCaMKII介导的毒鼠神经传递后K通道亚基的磷酸化可能通过调节神经元的兴奋性而促进海马区学习过程的分子机制。进一步了解CaMKII如何在大脑中建立学习和记忆，将有助于更好地理解学习缺陷或痴呆的潜在机制，并开发治疗学习障碍的新策略。

DESCRIPTION (provided by applicant): The goal of the proposed experiments is to understand the functional role of calcium/calmodulin-dependent protein kinase II (CaMKII) in regulating learning-associated changes in excitability of hippocampal neurons. It is well established that CaMKII is a key molecule required for learning and memory. Previous genetic and pharmacological studies have provided evidence for CaMKII-dependent modifications of synaptic strength during learning, although little is known about its role in the modulation of neuronal excitability, another important cellular mechanism of learning and memory. Neuronal excitability is primarily determined by the properties of ion channels: K+-channels, in particular, are key components in tuning of the membrane excitability of neurons. The working hypothesis to be tested is that CaMKII not only controls hippocampal synaptic plasticity but also modulates K+-channel properties accounting for an increase in hippocampal neuronal excitability during learning and memory consolidation. Analysis of alphaCaMKII mutant mice will determine the role of CaMKII as a molecular constituent responsible for learning-related excitability changes. The mutant mouse we will use is one that carries a point mutation at an autophosphorylation site in the alphaCaMKII gene (T286A) and consequently loses the function of this kinase. This study will clarify the role of alphaCaMKII in the increase in excitability of CA1 pyramidal neurons as evidenced by reduced afterhyperpolarization (AHP) during the acquisition of hippocampus-dependent associative learning (trace eyeblink conditioning) and spatial learning (water maze) tasks. Whole cell voltage-clamp recording will determine which components of outward potassium currents (SlAHP,IAHP, IM, IC, IA or IH) play a critical role in alphaCaMKII -mediated regulation of CA1 neuron excitability during hippocampal learning. Our integrated analyses of alphaCaMKII T2sBA mutants with behavioral, biophysical, biochemical and pharmacogenetic approaches will evaluate a molecular mechanism by which alphaCaMKII -mediated phosphorylation of K-channel subunits following muscarinic neurotransmission could contribute to hippocampal learning processes by regulating neuronal excitability. Further understanding of how CaMKII functions to establish learning and memory in brain will have relevance to the better understanding of mechanisms underlying learning deficits or dementia, and to developing novel strategies to treat learning disorders.