Mechanism and function of Kv channel targeting

描述（由申请人提供）：长期目标是了解电压门控钾（Kv）通道如何定位于适当的亚细胞区室，以及它们的定位如何影响神经元兴奋性，从而开发治疗神经系统疾病的新策略。KV通道功能障碍导致脑、心脏和肌肉疾病。KV通道是治疗癫痫、心律失常、神经性疼痛和多发性硬化症的药物干预的主要靶点。由于在许多细胞类型中广泛的通道表达，阻断剂或激活剂通常会带来严重的副作用。最近的研究表明，每个Kv通道在神经元中显示出不同的极化靶向模式。这是一个新兴的主题，这种极化靶向影响神经元的兴奋性。然而，Kv通道靶向的确切机制和功能仍然是个谜。Kv 3（Shaw）通道在Kv通道中具有独特的高激活阈值和快速失活动力学。它们是快速尖峰所必需的，并参与树突整合和递质释放。由Kv3.3基因突变引起的成人型共济失调证明了其重要功能。反映其不同的功能，Kv 3通道显示复杂的靶向模式，由未知的机制。我们的初步研究表明，Kv3.1的两个剪接变体具有相同的通道特性，但差异调节动作电位放电。有趣的是，它们在轴突树突靶向方面不同。基于我们的初步数据，我们提出了一个新的模型，即动作电位放电是由Kv 3通道靶向调节的，而Kv 3通道靶向又是由选择性剪接和蛋白磷酸化调节的。我们将在这个模型中测试三个假设，有三个目标。本研究采用电生理学、影像学、分子生物学和蛋白质生物化学等多学科的方法，旨在确定：（目的1）Kv通道的极化靶向是否对动作电位放电至关重要;（目的2）轴突起始段的锚蛋白G是否对Kv 3剪接变异体起条件性屏障作用;（目的3）蛋白磷酸化调节Kv 3通道靶向，从而调节动作电位放电。我们的研究将有助于产生新的治疗策略，并揭示新的药物靶点，用于特异性控制神经元中的Kv 3通道功能，例如开发小肽和激酶抑制剂，用于治疗共济失调，癫痫和睡眠障碍。

DESCRIPTION (provided by applicant): The long-term objectives are to understand how voltage-gated potassium (Kv) channels are localized into the proper subcellular compartments and how their localization affects neuronal excitability, and thus to develop new strategies for treating neurological diseases. Kv channel dysfunction causes diseases of brain, heart and muscle. Kv channels are the primary targets of pharmaceutical interventions to treat epilepsies, arrhythmias, neuropathic pain, and multiple sclerosis. Due to broad channel expression in many cell types, blockers or activators often bring severe side effects. Recent studies show that each Kv channel displays a distinct pattern of polarized targeting in neurons. It is the emerging theme that such polarized targeting affects neuronal excitability. However, the exact mechanism and function of Kv channel targeting remain mystery. Kv3 (Shaw) channels are unique among Kv channels in their high activation threshold and rapid deactivation kinetics. They are required for rapid spiking and involved in dendritic integration and transmitter release. Human adult-onset ataxia caused by mutations in Kv3.3 gene is a testament for their important functions. Reflecting their diverse functions, Kv3 channels display complex targeting patterns that are governed by unknown mechanisms. Our preliminary studies show that the two splice variants of Kv3.1 have identical channel properties but differentially regulate action potential firing. Interestingly, they differ in axon-dendrite targeting. Based on our preliminary data, we propose a new model that action potential firing is regulated by Kv3 channel targeting, which is in turn regulated by alternative splicing and protein phosphorylation. We will test three hypotheses in this model with three aims. By taking a multidisciplinary approach that includes electrophysiology, imaging, molecular biology and protein biochemistry techniques, we will determine whether: (Aim 1) polarized targeting of Kv channels is critical for action potential firing; (Aim 2) ankyrin G at the axon initial segment functions as a conditional barrier for Kv3 splice variants; (Aim 3) protein phosphorylation regulates Kv3 channel targeting and hence action potential firing. Our research will contribute to generate a new therapeutic strategy and reveal new drug targets for specifically controlling Kv3 channel functions in neurons, e.g. developing small peptides and kinase inhibitors as the treatment of ataxia, epilepsy and sleeping disorders.