Calcium-dependent functions in Hair Cells and Spiral Ganglion Neurons

 描述(申请人提供)：CA2通过各种钙通道(Cav)亚型以及非特异性阳离子通道进入细胞，如机械门控通道。钙离子进入后，调节毛细胞(HCs)和螺旋神经节神经元(SGN)的电和生化特性。我们实验室和其他实验室的前期研究在识别HCS和SGN中的多种钙介导信号方面取得了重要的新发现。然而，这种由钙介导的功能的细胞机制仍不清楚。此外，钙通过尚不清楚的机制激活几种外向通道电流，如钙激活的氯离子通道。这项提案的总体目标是部署创新的分子生物学、电生理和成像技术，其中许多技术来自以前的钙通道研究，以发现SGN中钙介导的生理学的基本和新的可及领域。这一提议推动了三个目标，以解决HC和SGN钙介导的生理问题，每个目标都具有基础和治疗意义。总的假设是，钙流入SGN调节不同的功能，从短期的膜兴奋性到长期的发育过程。其目的是：1)明确地解析SGN中不同亚型的钙通道的功能。2)确定听前向听后SGN特征转化的钙介导机制；3)确定SGN在听力开始前对HCs异位神经支配进行重组的机制。我们预测，在最初的不分青红皂白的接触后，突触前和突触后的联合活动会加强内侧HC(IHC)型1-SGN突触。该项目将使用不同的小鼠模型和相应的年龄匹配的对照组，以及生理、成像和生化工具。总体而言，这项建议将回答钙离子介导的HC和SGN生理学中的电和生化变化的基本未知问题。事实上，我们的发现可能揭示病理性听觉现象的机制，并通过这样做，促进我们设计新的治疗策略的努力。发育中的SGN是自发活跃的，这一发现可能会改变SGN的生长模式以及突触的形成，这可能会对新的人工耳蜗的设计产生可测量的影响，提高了精确度和准确度。

 DESCRIPTION (provided by applicant): Ca2+ enters into cells through a variety of Ca2+ channel (Cav) subtypes, as well as non-specific cationic channels, such as mechanically-gated channels. Upon entry, Ca2+ regulates the electrical and biochemical properties of hair cells (HCs) and spiral ganglion neurons (SGNs). Previous studies from our laboratory and others have made important new discoveries on the identification of the multiple Ca2+-mediated signaling in HCs and SGNs. However, the cellular mechanism of this Ca2+-mediated functions remains unclear. Additionally Ca2+ activates several outward channel currents, such as Ca2+-activated Cl- channels through mechanisms that still remains unknown. The overall goal of this proposal is to deploy innovative molecular biological, electrophysiological, and imaging techniques, many inspired from previous Ca2+ channel studies, for the discovery of fundamental and newly accessible arenas of Ca2+-mediated physiology in SGNs. This proposal drives three aims that address the HC and SGN Ca2+-mediated physiology, each with fundamental and therapeutic implications. The overall hypothesis is Ca2+ inflow into SGNs regulates distinct functions, ranging from short-term membrane excitability to long-term developmental processes. The Aims are: 1) To unequivocally resolve the functions of distinct subtypes of Ca2+ channels in SGNs. 2) To determine Ca2+-mediated mechanisms underlying the transformation of the features of pre- to post-hearing SGNs and finally 3) To determine the mechanisms underlying the reorganization of promiscuous innervation of HCs by SGNs prior to hearing onset. We predict that combined pre- and post-synaptic activities strengthen inner HC (IHC)-type 1-SGN synapse following initial indiscriminate contacts. The project will be conducted using different mouse models and their corresponding age-matched controls, as well as physiological, imaging and biochemical tools. Overall, this proposal will answer fundamental unknowns of Ca2+-mediated electrical and biochemical changes in HC and SGN physiology. Indeed, our findings are likely to reveal the mechanisms of pathological auditory phenomena, and in doing so, facilitate our efforts to design new therapeutic strategies. The discovery that developing SGNs are spontaneously active, and that this may alter SGN growth pattern as well as synapse formation are likely to have measurable impact in the design of new cochlear implants with increased precision and accuracy.