Cellular and Ion Channel Mechanisms Underlying the Sense of Light Touch in Mammals

摘要： 触觉对于日常工作至关重要，包括触觉辨别、社交和 环境探索。这个项目的总体目标是确定细胞和分子 哺乳动物触觉的潜在机制。此前的研究表明，默克尔的光盘，一种 触觉末端器官的主要类型，在触觉中起着核心作用。默克尔的圆盘位于接触中 全身的敏感点，特别是人类指尖和非灵长类动物的胡须毛囊 哺乳动物。默克尔视盘由一个默克尔细胞和一个β-传入结尾(默克尔结尾)组成 突触样结构。我们和其他人之前已经证明，默克尔细胞上的Piezo2通道是 触觉传感器。我们进一步证明，触觉刺激激活默克尔细胞中的Piezo2通道，从而导致 β-动作电位，导致A-CA2-传入冲动和行为触觉反应。然而， 触觉诱发的Merkel细胞兴奋信号传递到Merkel终末的机制 仍然难以捉摸，也是此次续签申请的重点。我们的中心假设是酸感离子 通道(ASIC)是兴奋性突触后受体，质子是介导的主要递质 兴奋性突触后电流与Merkel间盘的突触传递。我们将测试这部小说 有以下具体目的的假设。目标1.描述默克尔的EPSC的基本性质 Aβ-传入纤维的终末。目的2.证明EPSCs是由位于默克尔的ASIC介导的 结局。目的3.阐明质子激活ASICs是导致EPSCs产生的原因 默克尔的结局。目的4.确定在Merkel末端介导EPSCs的功能ASICs的亚型。 压力膜片钳记录将应用于啮齿动物胡须毛的默克尔末端的半结处 记录机械刺激和包括突触在内的其他技术引起的EPSCs的卵泡 生理学、药理学、免疫组织化学和小鼠遗传学将用来实现上述目标。 目标。通过实现上述目标，我们将揭示出一种新的调解基本机制 默克尔视盘触觉信号的突触传递。这将大大促进科学知识的发展。 关于触觉背后的分子机制。它还可能在以下方面产生重要影响 在下列临床情况下出现的机械性感觉功能障碍(例如，触觉丧失) 糖尿病和化疗。

ABSTRACT: The sense of touch is critical for daily tasks including tactile discrimination, social interaction, and environmental exploration. The overall objective of this project is to identify the cellular and molecular mechanisms underlying the sense of touch in mammals. Previous studies have shown that Merkel discs, a main type of tactile end organ, play a central role in the sense of touch. Merkel discs are located in touch sensitive spots throughout the body especially at human fingertips and whisker hair follicles of non-primate mammals. A Merkel disc consists of a Merkel cell and an Aβ-afferent ending (Merkel ending) to form a synapse-like structure. We and others have previous shown that the Piezo2 channel on Merkel cells is the sensor of touch. We have further shown that tactile stimuli activate Piezo2 channels in Merkel cells to result in Ca2+-action potentials, which leads to Aβ-afferent impulses and behavioral tactile responses. However, the mechanism by which tactile-induced excitatory signals on Merkel cells are transmitted to Merkel endings remains elusive and is the focus of this renewal application. Our central hypothesis is that acid sensing ion channels (ASICs) are the excitatory postsynaptic receptors and proton is the principal transmitter to mediate excitatory postsynaptic currents (EPSCs) and synaptic transmission at Merkel discs. We will test this novel hypothesis with the following specific aims. Aim 1. Characterize the fundamental nature of EPSCs at Merkel endings of Aβ-afferent fibers. Aim 2. Demonstrate that EPSCs are mediated by ASICs located at Merkel endings. Aim 3. Elucidate that activation of ASICs by protons is responsible for the generation of EPSCs at Merkel endings. Aim 4. Identify the isoform of functional ASICs that mediate EPSCs at Merkel endings. Pressure-patch-clamp recordings will be applied at the heminode of Merkel endings in rodent whisker hair follicles to record EPSCs that are evoked by mechanical stimulation, and other techniques including synaptic physiology, pharmacology, immunohistochemistry, and mouse genetics will be used to achieve the above aims. By completing the above aims, we will have uncovered a new fundamental mechanism mediating synaptic transmission of tactile signals at Merkel discs. This will significantly advance scientific knowledge about molecular mechanisms underlying the sense of touch. It may also have important implications in mechanical sensory dysfunctions (e.g., loss of touch sensation) seen under clinical conditions such as diabetes and chemotherapy.