ACTIVITY-DRIVEN PLASTICITY OF THE HAIR CELL CYTOSKELETON

活动驱动的毛细胞细胞骨架的可塑性

基本信息

批准号：
10748106
负责人：
Alejandra Catalina Velez Ortega
金额：
$ 44.2万
依托单位：
UNIVERSITY OF KENTUCKY
依托单位国家：
美国
项目类别：
财政年份：
2023
资助国家：
美国
起止时间：
2023-06-07 至 2028-05-31
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10748106
关键词：
Actins Adult Affect Architecture Auditory Cells Cochlea Crosslinker Cytoskeleton Data Development Exhibits F-Actin Filament Fluorescence Recovery After Photobleaching Freeze Substitution Freezing Hair Hair Cells Hearing Height Impairment In Situ Ions Knowledge Label Labyrinth Lead Length Link Maintenance Measures Mediating Microfilaments Molecular Morphology Mus Myosin ATPase Natural regeneration Noise-Induced Hearing Loss Organelles Organism Pattern Physiological Polymers Process Protein Isoforms Proteins Rattus Reporting Rest Sampling Scanning Electron Microscopy Sensory Shapes Stereocilium Structure Supporting Cell Testing Transmission Electron Microscopy beta Actin cellular microvillus congenital deafness crosslink depolymerization experimental study gamma Actin hearing impairment mutant mouse model new therapeutic target noise exposure polymerization postnatal sound tomography vibration

项目摘要

PROJECT SUMMARY/ABSTRACT The mechanosensitivity of the inner ear hair cells depends on cellular projections known as stereocilia, organized in rows of increasing height, with mechano-electrical transduction (MET) channels located at the tips of shorter row stereocilia. The core of stereocilia consists of a highly crosslinked paracrystalline array of actin filaments. While crosslinker proteins are constantly renewed, the renewal of actin is limited to the stereocilia tips. We previously reported that the stereocilia actin core exhibits activity-dependent plasticity (Velez-Ortega, et al., eLife 2017). We showed that the blockage of MET channels or the breakage of the tip links that gate these channels lead to the selective shortening of transducing stereocilia (i.e. the stereocilia that harbor MET channels), while the non-transducing tallest row stereocilia remain unaffected. Once the MET blockage is removed or the tip links regenerate, the stereocilia regrow. Our preliminary data also show that this MET-dependent stereocilia remodeling can affect the resting tension within the MET machinery in seconds. Thus, this process may dynamically regulate the sensitivity of hair cells to sound-induced vibrations and, hence, the sensitivity of our hearing. Yet, the exact mechanisms of MET-dependent stereocilia remodeling are still obscure. It is unknown even whether the activity-dependent plasticity of the stereocilia cytoskeleton is limited to the regions of active actin renewal or can expand beyond this region into the “stable” part of the stereocilia shaft. Here, we hypothesize that the MET activity regulates the extent of the stereocilia cytoskeleton undergoing active actin remodeling. To test this, Aim 1 will evaluate MET-dependent changes in actin dynamics within the stereocilia and the cuticular plate, an actin-rich structure supporting the stereocilia bundle. Aim 2 will evaluate MET-driven changes in the ultrastructural organization of stereocilia actin with transmission electron microscopy tomography. Since the MET-dependent stereocilia remodeling was studied so far only in young postnatal hair cells, Aim 3 will assess whether this phenomenon is present also in the mature adult auditory hair cells. In Aim 4, we begin to explore the molecular players involved in the MET-driven stereocilia remodeling, by evaluating the expression of so-called “stereocilia row identity proteins” in a mutant mouse model that exhibits MET-dependent actin remodeling not only in transducing stereocilia but also, unexpectedly, in non-transducing stereocilia. The study is significant, because it may clarify how exactly a hair cell performs fine adjustments of the architecture of the stereocilia bundle, thereby maintaining the sensitivity of our hearing throughout a lifetime. In addition, stereocilia shortening—and perhaps their eventual disappearance—could occur after noise exposure (when the MET current is reduced due to tip link breakage) or in certain cases of congenital deafness (due to impaired MET current). Therefore, this study will expand our knowledge of the molecular mechanisms of various types of hearing loss.

项目概要/摘要内耳毛细胞的机械敏感性取决于细胞投射，称为静纤毛，排列成高度不断增加的行，具有机电传导 (MET) 通道位于较短行静纤毛的尖端。静纤毛的核心由高度交联的结构组成。当交联蛋白不断更新时，肌动蛋白丝的晶状阵列也会不断更新。肌动蛋白仅限于静纤毛尖端。我们之前报道过静纤毛肌动蛋白核心表现出活动依赖性可塑性（Velez-Ortega 等人，eLife 2017）。或者控制这些通道的尖端链接的断裂导致换能的选择性缩短静纤毛（即含有 MET 通道的静纤毛），而非转导最高行静纤毛一旦 MET 堵塞被移除或尖端链接再生，静纤毛就会重新生长。我们的初步数据还表明，这种依赖于 MET 的静纤毛重塑会影响静息状态。 MET 机器内的张力在几秒钟内因此，该过程可以动态调节灵敏度。毛细胞对声音引起的振动的影响，从而影响我们听觉的敏感性。 MET 依赖性静纤毛重塑的机制仍然不清楚。静纤毛细胞骨架的活动依赖性可塑性仅限于活跃肌动蛋白更新的区域或者可以扩展到这个区域之外，进入静纤毛轴的“稳定”部分。 MET 活性调节静纤毛细胞骨架进行主动肌动蛋白重塑的程度。为了测试这一点，目标 1 将评估静纤毛和肌动蛋白内肌动蛋白动力学的 MET 依赖性变化。角质板是一种支持静纤毛束的富含肌动蛋白的结构，Aim 2 将评估 MET 驱动的情况。透射电子显微镜观察静纤毛肌动蛋白超微结构的变化由于迄今为止仅在年轻的产后研究了 MET 依赖性静纤毛重塑。毛细胞，Aim 3 将评估这种现象是否也存在于成熟的成年听毛中在目标 4 中，我们开始探索 MET 驱动的静纤毛中涉及的分子参与者。通过评估突变小鼠中所谓的“立体纤毛行识别蛋白”的表达来进行重塑该模型不仅在转导静纤毛方面表现出 MET 依赖性肌动蛋白重塑，而且，出乎意料的是，在非转导静纤毛中，这项研究意义重大，因为它可能阐明究竟是如何发生的。毛细胞对静纤毛束的结构进行精细调整，从而维持此外，我们一生中听力的敏感性也会缩短——也许还有它们的缩短。最终消失——可能在噪声暴露后发生（当 MET 电流因尖端而减少时）链接断裂）或在某些先天性耳聋的情况下（由于 MET 电流受损）。研究将扩大我们对各种类型听力损失的分子机制的了解。