Roles of K channels in spiral ganglia neurons in health, diseases and aging.

描述（由申请人提供）：迄今为止，对影响我们老龄化人群的进行性听力损失（PHL）的潜在细胞和分子机制知之甚少。毛细胞和螺旋神经节神经元（SGN）的变性是PHL的常见表型。K+通道在内耳中的重要性得到了以下证据的支持：通道的特定突变导致人类毛细胞（HC）和SGN的变性。在这里，我们假设SGN中的K+通道调节静息膜电位及其兴奋性，以调节细胞内Ca 2+（Ca 2 +i）的通量，其作为关键的第二信使，决定SGN的发育、功能和存活。然而，过度的[Ca 2 +i]可诱导神经元死亡。我们进一步预测，在衰老过程中，在与SGN进行性变性相关的几种K+通道病中，K+通道的表达发生了深刻的变化，导致膜去极化，Ca 2+内流过度增加，从而引发Ca 2+诱导的凋亡性神经元死亡。该提案将确定K+通道的同源和异源多聚体如何赋予K+电流的多样性，以及孔形成α亚基的突变如何产生K+电流的深刻改变。我们还将了解细胞内和单程辅助亚基如何控制SGN中的K+通道。五个具体目标考虑; SGN中K+通道的基本特征赋予其作为K+转运蛋白的作用（目的1）;哪些K+通道亚基构成天然SGN K+电流（目的2）;可溶性胞质蛋白，K+通道相互作用蛋白（KChIP）如何调节K+通道电流的表面表达和性质（目的3）; K+通道的单通道亚基KCNE如何在健康和疾病中决定特定的K+通道功能（目的4）;以及在衰老过程中发生的介导PHL的生物化学和功能变化（目的5）。该提案使用正常和基因改变的小鼠作为实验模型，并利用经典技术（电生理学，生物化学和电子显微镜）和新的策略，使强大的分子生物学的最新进展（例如，siRNA敲除和病毒介导的基因转移）。对听觉科学特别重要的是，随着我们对通道的门控、渗透和药理学的理解变得更加精细，可能实现K+通道亚型特异性药物的合理设计。 公共卫生相关性：螺旋神经节神经元（SGN）是以电信号的形式将声音信息从内耳传递到大脑的初级神经元。这些神经元以惊人的精确度和灵敏度传递声音信息。多种疾病和衰老与SGN进行性变性相关，导致听力损失。我们的目标是了解K+通道蛋白如何调节SGNs的电活性和生物化学。我们小组和其他人的研究表明，在衰老过程中和几种疾病状态下，K+通道的表达发生变化，可能是SGN电活动变化的基础，导致神经元变性。在细胞和分子水平上，我们对K+通道及其改变如何触发SGN变性知之甚少，尽管其具有潜在的治疗效果。来自我们实验室和其他实验室的数据的有力证据激发了我们的整体假设。我们推测SGN中的K+通道调节其电活动。然而，在衰老和几种疾病状态下，这些K+通道的功能发生改变，引发神经元死亡。我们的最终目标是设计药物，可能有助于减轻/预防我们老龄化人口和影响内耳的几种疾病中的神经元死亡。

DESCRIPTION (provided by applicant): To date, little is known about the underlying cellular and molecular mechanisms of progressive hearing loss (PHL) that affects our aging population. Degeneration of hair cells and spiral ganglia neurons (SGNs) are common phenotypes associated with PHL. The importance of K+ channels in the inner ear is underpinned by evidence that specific mutations of the channel result in degeneration of hair cells (HCs) and SGNs in humans. Here, we hypothesize that K+ channels in SGNs regulate the resting membrane potential and their excitability in order to modulate fluxes of intracellular Ca2+ (Ca2+i), which serves as a key second messenger, determining the development, function, and survival of SGNs. However, undue [Ca2+i] may induce neuronal death. We further predict that during aging and in several K+ channelopathies associated with progressive degeneration of SGNs, the expression of K+ channels are profoundly altered leading to membrane depolarization, excessive increased in Ca2+ influx, which triggers Ca2+- induced apoptotic neuronal death. The proposal will identify how homo- and hetero- multimers of K+ channels confer diversity of K+ currents, and how mutations of the pore- forming a-subunit may produce profound alterations of K+ currents. We will also learn how intracellular and single-pass accessory subunits control K+ channels in SGNs. Five specific aims consider; what elementary features of K+ channels in SGNs confer their roles as K+ transporters (Aim 1); what K+ channel subunits constitute native SGN K+ currents (Aim 2); how soluble cytoplasmic proteins, K+ channel interacting proteins (KChIP), regulate the surface expression and properties of K+ channel currents (Aim 3); how single-pass subunits of K+ channels, KCNEs, dictate specific K+ channel functions in health and disease (Aim 4); and the ensuing biochemical and functional changes that occur during aging (Aim 5) that mediates PHL. The proposal uses normal and genetically altered mice as the experimental models, and exploit classical techniques (electrophysiology, biochemistry and electron microscopy) and novel strategies made powerful by recent advances in molecular biology (e.g, siRNA knockdown and viral- mediated gene transfer). Of particular importance to auditory science is the possibility that a rational design of K+ channel subtype-specific drugs may be realized, as our understanding of the gating, permeation, and pharmacology of the channels becomes more refined. PUBLIC HEALTH RELEVANCE: Spiral ganglia neurons (SGNs) are the primary neurons that convey sound information in the form of electrical signals from the inner ear to the brain. These neurons transmit sound information with remarkable precision and sensitivity. Several diseases and aging are associated with progressive degeneration of SGNs leading to hearing loss. Our objectives are to understand how K+ channel proteins regulate the electrical activity and biochemistry of SGNs. Studies from our group and others have demonstrated that during the aging process and in several diseased states the expression of K+ channels are altered and may underlie changes in electrical activity in SGNs that leads to degeneration of the neurons. At the cellular and molecular level, we know very little about the how K+ channels and their alterations trigger SGN degeneration, despite its potential therapeutic ramifications. Strong evidence from data from our laboratory and others motivates our overall hypothesis. We hypothesize that K+ channels in SGNs regulate their electrical activity. However, during aging and several diseased states the functions of these K+ channels are altered, triggering neuronal death. Our ultimate goal is to design drugs that may help alleviate/prevent neuronal death in our aging population and in several diseases affecting the inner ear.