Ion Channel Regulation of Excitability in Immature Brain

描述(申请人提供)：建议的研究集中在未成熟海马神经元兴奋性的信号通路调节的分子机制。信号级联激活蛋白激酶，蛋白激酶通过磷酸化对底物蛋白进行生化修饰。离子通道亚基的激酶磷酸化是一种很好的调节神经元通道功能的方法，因此，膜的兴奋性。尽管有这些见解，但调节未成熟神经元膜属性的分子机制仍不清楚。我们认为，未成熟海马神经元兴奋性的神经调节的一个重要位点是通过磷酸化来调节K+通道的活性。本研究主要针对钙激活的K+通道，即小电导SK通道。这些亚基构成了电流的一种成分，称为后超极化(AHP)。AHP遵循单个动作电位或一系列动作电位。因此，AHP在海马神经元早期电反应的形成中起着关键作用，而这一电流的调节可以极大地影响神经元的兴奋性。鉴于K+通道对神经元兴奋性的调节至关重要，K+通道表达和激酶调节的发育差异可能在未成熟脑的正常可塑性和病理过程中发挥作用，如癫痫。对于这些研究，我们将集中在SK2和它所支持的电流，阿帕明敏感的AHP。这一设想的核心假设是，cAMP依赖的蛋白激酶(PKA)途径通过直接磷酸化来调节SK2通道的功能，这种翻译后机制以及SK2通道表达的发育调节和潜在的mAHP参与了发育中海马神经元兴奋性的调节。作为我们研究的一部分，我们将调查在SK2通道亚单位和对apamin敏感的AHP的表达和调节方面存在发育差异的可能性，这可能是未成熟大脑表现出兴奋性增加时期的良好特征观察的基础。这一特征可能有助于中枢神经系统发育中的正常可塑性以及病理，例如未成熟脑中癫痫敏感性的增加。

DESCRIPTION (provided by applicant): The proposed studies focus on molecular mechanisms of signaling pathway modulation of excitability in neurons of immature hippocampus. Signaling cascades activate protein kinases, which biochemically modify substrate proteins via phosphorylation. Kinase phosphorylation of ion channel subunits is a well- characterized means of regulating channel function in neurons and therefore, membrane excitability. Despite these insights, the molecular mechanisms underlying the regulation of the membrane properties of immature neurons remain unclear. We propose that an important locus for mediating neuromodulation of excitability of neurons from immature hippocampus is through regulation of potassium (K+) channel activity by phosphorylation. This proposal focuses on Ca2+-activated K+ channels known as the small conductance SK channels. These subunits contribute to a component of the current known as the afterhyperpolarization (AHP). The AHP follows a single action potential or a series of action potentials. Therefore, the AHP plays a critical role in shaping the electrical responsiveness of hippocampal neurons beginning early in life, and modulation of this current can dramatically affect neuronal excitability. Given that K+ channels are critical to the regulation of neuronal excitability, developmental differences in K+ channel expression and kinase regulation may play a role in normal plasticity and pathological processes such as epilepsy in the immature brain. For these studies we will focus on SK2 and the current that it underlies, the apamin-sensitive AHP. The central hypothesis of this proposal is that the cAMP-dependent protein kinase (PKA) pathway regulates SK2 channel function through direct phosphorylation and that this post-translational mechanism as well as the developmental regulation of the expression of SK2 channels and the underlying mAHP contributes to the regulation of neuronal excitability in developing hippocampus. As part of our studies we will investigate the possibility that there are developmental differences in the expression and regulation of SK2 channel subunits and the apamin-sensitive AHP that may underlie the well-characterized observation that immature brain exhibits periods of increased excitability. This feature likely contributes to normal plasticity in developing CNS as well as pathology, such as increased seizure susceptibility in immature brain.