Chronic Intermittent Ethanol and Kv4.2 Channels

 描述(由申请人提供)：大量饮酒与海马体功能障碍有关。有证据表明，酗酒者的海马区依赖认知障碍是复发率高和治疗结果差的一个促成因素。慢性酒精暴露会重塑谷氨酸能突触，这些结构和功能上的神经适应与学习和记忆障碍有关。然而，我们对酒精相关认知下降的神经机制的了解存在着很大的差距。在海马区CA1区锥体神经元中，由Kv4.2a亚基组成的电压依赖性钾(Kv)通道在远端树突中丰富，是亚阈值瞬变A-型钾电流(ISA)的基础。Kv4.2通道通过调节突触整合和可塑性，对神经元信号进行关键调节。以前的工作表明，Kv4.2的表面表达是通过与一组称为K+通道相互作用蛋白(KChIP)的蛋白质相互作用来促进的。新的证据表明，Kv4.2通道和NMDA受体之间存在功能上的偶联，这可能是可塑性的关键，并受KChIP3的调节。我们的初步数据表明，器官型海马片培养的慢性乙醇处理降低了Kv4.2通道功能和表面表达，并增强了CA1锥体神经元远端顶端树突的反向传播动作电位(BAPS)诱发的钙瞬变。此外，慢性乙醇显著降低KChIP3的表达，增加NMDA受体的表达。在成年大鼠中，慢性间歇性乙醇(CIE)暴露下调了Kv4.2通道的表达，并损害了在海马依赖任务中的表现。因此，我们的初步数据已经确定Kv4.2通道和KChIP3是慢性酒精暴露后CA1锥体神经元异常信号处理的潜在分子靶点。我们设计了一套全面而有重点的研究来检验这一假设的主导假设，即慢性乙醇暴露导致Kv4.2通道功能降低和NMDA受体上调，导致BaP信号增强、可塑性异常和海马区功能障碍。拟议的研究涉及生物化学、切片电生理学、多电极记录、光遗传学和病毒载体技术，以检验下列假说：目的1)验证CIE通过调节KChIP3双向改变海马区Kv4.2通道和NMDA受体表达的假说；目的2)测试CIE在急性脑片制备中降低Kv4.2通道的表达和功能并改变峰时序依赖的突触可塑性的假说；目的3)确定CIE是否改变了海马区的认知功能，并在体内诱导异常的海马可塑性。这些研究将促进我们对酒精导致突触可塑性和认知功能损害的神经机制的了解，并为更有效地治疗酒精中毒和酒精相关问题确定新的治疗靶点。

 DESCRIPTION (provided by applicant): Heavy alcohol consumption is associated with hippocampal dysfunction. Evidence suggests that hippocampal-dependent cognitive impairments in alcoholics are a contributing factor in high relapse rates and poor treatment outcomes. Chronic alcohol exposure remodels glutamatergic synapses, and these structural and functional neuroadaptations have been implicated in learning and memory deficits. However, there is a substantial gap in our knowledge about the neural mechanisms that underlie alcohol-associated cognitive decline. In CA1 pyramidal neurons of the hippocampus, voltage-dependent potassium (Kv) channels comprised of Kv4.2 a subunits are enriched in distal dendrites and underlie the subthreshold transient A-type K+ current (ISA). Kv4.2 channels function to critically regulate neuronal signaling by modulating synaptic integration and plasticit. Previous work has shown that surface expression of Kv4.2 is promoted through interaction with a group of proteins called K+ channel interacting proteins (KChIPs). Emerging evidence suggests that there is a functional coupling between Kv4.2 channels and NMDA receptors that may be critical for plasticity and is regulated by KChIP3. Our preliminary data demonstrate that chronic ethanol treatment of organotypic hippocampal slice cultures reduces Kv4.2 channel function and surface expression and enhances Ca2+ transients evoked by back-propagating action potentials (bAPs) in distal apical dendrites of CA1 pyramidal neurons. In addition, chronic ethanol significantly reduced KChIP3 expression and increased NMDA receptor expression. In adult rats, chronic intermittent ethanol (CIE) exposure down-regulates Kv4.2 channel expression and impairs performance on hippocampal-dependent tasks. Thus, our preliminary data have identified Kv4.2 channels and KChIP3 as promising molecular targets that underlie aberrant signal processing in CA1 pyramidal neurons in following chronic alcohol exposure. We have designed a comprehensive yet focused set of studies to test the overarching hypothesis of this proposal that the reduction in Kv4.2 channel function and up-regulation of NMDA receptors by chronic ethanol exposure contributes to enhanced bAP signaling, aberrant plasticity and hippocampal dysfunction. The proposed studies involve a multifaceted approach that involves biochemistry, slice electrophysiology, multielectrode recording, optogenetics, and viral vector technologies to test the following hypotheses: Aim 1) Test the hypothesis that CIE bidirectionally alters expression of Kv4.2 channels and NMDA receptors in the hippocampus through modulation of KChIP3; Aim 2) Test the hypothesis that CIE reduces expression and function of Kv4.2 channels and alters spike timing- dependent synaptic plasticity in the acute slice preparation; and Aim 3) Determine whether CIE alters the cognitive function of the hippocampus and induces aberrant hippocampal plasticity in vivo. These studies will advance our knowledge of the neural mechanisms contributing to ethanol-associated impairments in synaptic plasticity and cognitive function and identify novel therapeutic targets for more effective treatment of alcoholism and alcohol-related problems.