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)通道如何定位到适当的亚细胞室，以及它们的定位如何影响神经元的兴奋性，从而开发治疗神经疾病的新策略。KV通道功能障碍会导致脑、心脏和肌肉疾病。KV通道是治疗癫痫、心律失常、神经病理性疼痛和多发性硬化症的药物干预的主要目标。由于广泛的通道表达在多种细胞类型，阻滞剂或激活剂往往会带来严重的副作用。最近的研究表明，每个Kv通道在神经元中都显示出不同的极化靶向模式。这种极化靶向影响神经元的兴奋性，这是一个新兴的主题。然而，Kv通道靶向的确切机制和功能仍然是个谜。Kv3(Shaw)通道以其高激活阈值和快速失活动力学在Kv通道中独一无二。它们是快速突起所必需的，并参与树突整合和递质释放。Kv3.3基因突变引起的人类成人性共济失调是其重要功能的证明。Kv3通道表现出复杂的靶向模式，反映了它们的不同功能，这些模式受到未知机制的支配。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，但对动作电位的激活有不同的调节作用。有趣的是，它们在轴突-树突靶向方面有所不同。基于我们的初步数据，我们提出了一个新的模型，即动作电位的激发受Kv3通道靶向的调节，Kv3通道靶向又受选择性剪接和蛋白质磷酸化的调节。我们将在这个模型中测试三个假设，目的有三个。通过采用包括电生理学、成像、分子生物学和蛋白质生物化学技术在内的多学科方法，我们将确定：(1)Kv通道的极化靶向对动作电位激发至关重要；(2)轴突起始段的Anyrin G作为Kv3剪接变异体的条件性屏障；(目标3)蛋白质磷酸化调节Kv3通道靶向，从而调节动作电位激发。我们的研究将有助于开发一种新的治疗策略，并揭示专门控制神经元Kv3通道功能的新药物靶点，例如开发小肽和激酶抑制剂作为治疗共济失调、癫痫和睡眠障碍的药物。

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.