CaMKII in neuronal signaling and degeneration

描述（由申请人提供）：钙信号传导在神经元的功能中起着中心但令人惊讶的灵活作用，有助于神经传递、突触可塑性和神经元死亡。钙-钙调蛋白依赖性蛋白激酶II（CaMKII）是一种多功能的丝氨酸/苏氨酸蛋白激酶，在正常海马突触可塑性中起重要作用 和小鼠的空间学习能力。CaMKII被认为将钙瞬变（即神经元活性）的频率解码为分级的活性水平。与CaMK II在生理钙信号传导中的作用不同，其在病理钙信号传导中的作用在很大程度上是未知的。异常的钙信号传导伴随着多种与谷氨酸（大脑中主要的兴奋性神经递质）相关的疾病状态。过量的谷氨酸盐释放伴随急性疾病状态（例如缺血和脑创伤）以及慢性神经退行性疾病（具有缺血和癫痫的迟发性神经元死亡）。CaMKII在兴奋性毒性中的确切作用尚不清楚;然而，有一些线索值得注意。首先，CaMKII在对兴奋性毒性高度敏感的大脑区域中高度表达（占总蛋白的1-2%）。其次，缺血持续时间与CaMKII失活和神经元死亡相关。第三，在兴奋性毒性期间防止CaMKII活化防止神经元死亡;这一过程也防止CaMKII经历活性依赖性失活和聚集。第四，我们最近发表了抑制CaMKII通过钙调节异常和对异常谷氨酸信号的过度兴奋直接诱导神经元凋亡。在此应用中，我们建议了解CaMKII底物磷酸化，失活和聚集在高度控制的生化实验和活细胞中的新机制。此外，我们建议确定星形胶质细胞中的CaMKII失活是否会破坏正常的神经胶质细胞-神经元通讯;我们的初步数据表明，这一过程会导致星形胶质细胞变性。这些实验不仅将推进我们对病理性钙信号传导过程中CaMKII信号传导的理解，而且还将揭示与CaMKII结构、底物磷酸化和蛋白质聚集相关的基本机制。这些研究的结论也可能确定新的治疗靶点和机制，以破坏谷氨酸兴奋性毒性诱导的神经元和神经胶质细胞死亡。

DESCRIPTION (provided by applicant): Calcium signaling plays a central yet surprisingly flexible role in the function of neurons, contributing to neurotransmission, synaptic plasticity, ad neuronal death. Calcium-calmodulin (CaM)-dependent protein kinase II (CaMKII) is a multifunctional Ser/Thr protein kinase that is essential for normal hippocampal synaptic plasticity and spatial learning in mice. CaMKII is believed to decode the frequency of calcium transients (i.e. neuronal activity) in to graded levels of activity. Unlike the role of CaMKII in physiologica calcium signaling, its role in pathological calcium signaling is largely unknown. Aberrant calcium signaling accompanies multiple disease states associated with glutamate, the major excitatory neurotransmitter in the brain. Excessive glutamate release accompanies acute disease states (e.g. ischemia and brain trauma) as well as chronic neurodegenerative disorders (delayed neuronal death with ischemia and epilepsy). Exactly what CaMKII is doing in excitotoxicity is unknown; however, there are clues worth noting. First, CaMKII is highly expressed (1-2% of total protein) in regions of the brain highly susceptible to excitotoxicity. Second, ischemic duration correlates to CaMKII inactivation and neuronal death. Third, preventing CaMKII from activating during excitotoxicity prevents neuronal death; a process that also prevents CaMKII from undergoing activity-dependent inactivation and aggregation. Fourth, we have recently published that inhibiting CaMKII directly induces neuronal apoptosis via calcium dysregulation and hyperexcitability to aberrant glutamate signaling. In this application, we propose to understand novel mechanisms underlying CaMKII substrate phosphorylation, inactivation and aggregation in both highly controlled biochemical experiments and in living cells. In addition, we propose to determine if CaMKII inactivation in astrocytes disrupts normal glial-neuronal communication; a process our preliminary data indicates leads to astrocyte degeneration. These experiments will not only advance our understanding of CaMKII signaling during pathological calcium signaling, but they will also shed new light on basic mechanisms related to CaMKII structure, substrate phosphorylation, and protein aggregation. Conclusions from these studies may also identify novel therapeutic targets and mechanisms to disrupt neuronal and glia death induced by glutamate excitotoxicity.