Cellular and molecular mechanisms of cold-adapted mechanosensation in the hibernating squirrel

项目总结 十三行地松鼠是一种专属的冬眠动物，它会季节性地将体温从 在活动状态下为37°C，在昏迷期间为2-4℃。虽然这样的温度通常会抑制外周信号 哺乳动物，迟钝的松鼠仍然对触觉信号敏感，并能被触觉唤醒 (机械传感)。然而，其中涉及的神经生物学机制仍不清楚。长期的 这项研究的目标是确定提供耐寒能力的细胞和分子特征 支持哺乳动物极端耐热性的机械感觉。 压力刺激是由背根神经节(DRG)中一个特殊的神经元亚群感知的，称为 机械感受器。机械门控离子通道，如Piezo2，将压力转换为离子电流， 激活电压门控离子通道，该通道通过动作电位(AP)向下游传递信号。 Piezo2和电压门控离子通道具有进化的温度依赖动力学 允许热阻的操控。这项研究将在戴维斯博士的实验室进行。 耶鲁大学的Elena Gracheva和Slav Bagriantsev评估了离子通道的中心假说 机械感受器的修饰是十三行地面冷适应机械感觉的基础 松鼠。 Gracheva和Bagriantsev实验室过去的工作表明，这个物种表现出结构性的低 麻木状态下伤害性AP机械的温度敏感性和功能下降。我们的前期工作也 显示机械敏感电流在昏迷期间保持不变。因此，我们使用中的组合 用原位杂交、RNA测序和电生理学方法评价松鼠背根神经节神经元是否有 与小鼠相比，选择性地增强了机械敏感性，代价是其他感觉方式 背根神经节神经元(目标1)。此外，冷暴露会扩大AP并扰乱典型的 哺乳动物神经元由于Na+/K+ATPase泵的动力学减慢。相比之下，我们的前期工作 结果表明，冷暴露的迟钝神经元表现为AP加宽减少，静息膜电位完整。 根据这些数据，我们使用全细胞和体外电生理学来评估松鼠 机械感受器具有耐寒的发电机械(目标2)。 据我们所知，这项研究是首次尝试剖析感冒的细胞机制-- 适应哺乳动物的机械感觉。阐明极端寒冷中的神经功能有可能 为对抗临床低温手术后的神经元损伤提供新的靶点。

PROJECT SUMMARY The thirteen-lined ground squirrel is an obligate hibernator that seasonally drops its body temperature from 37° in the active state to 2-4°C during torpor. While such temperatures typically inhibit peripheral signaling in mammals, torpid squirrels remain sensitive to tactile cues and can be awakened by the sense of touch (mechanosensation). However, the neurobiological mechanisms involved remain unknown. The long-term goal of this study is to identify the cellular and molecular signatures that afford cold-resistant mechanosensation to support extreme thermal tolerance in mammals. Pressure stimuli are sensed by a specialized subset of neurons in the dorsal root ganglion (DRG) known as mechanoreceptors. Mechanically gated ion channels such as Piezo2 convert pressure into ionic current that activates voltage-gated ion channels, which relay the signal downstream through action potentials (APs). Piezo2 and voltage-gated ion channels have temperature-dependent dynamics ripe for evolutionary manipulations permitting thermal resistance. This study, which will be conducted at the laboratories of Drs. Elena Gracheva and Slav Bagriantsev at Yale University, assesses the central hypothesis that ion channel modifications in mechanoreceptors underlie cold-adapted mechanosensation in the thirteen-lined ground squirrel. Past work from the Gracheva and Bagriantsev labs has shown that this species shows constitutively low thermosensitivity and decreased function of nociceptive AP machinery during torpor. Our preliminary work also shows that mechanosensitive currents are preserved during torpor. Accordingly, we use a combination of in situ hybridization, RNA sequencing and electrophysiology to assess whether squirrel DRG neurons have selectively potentiated mechanosensitivity at the cost of other sensory modalities, relative to mouse DRG neurons (Aim 1). Moreover, cold exposure widens APs and disrupts voltage gradients in typical mammalian neurons due to slowed kinetics of the Na+/K+ ATPase pump. In contrast, our preliminary work shows that cold-exposed torpid neurons show decreased AP widening and intact resting membrane potential. In light of these data, we use whole-cell and ex vivo electrophysiology to assess whether squirrel mechanoreceptors have cold-resistant electrogenic machinery (Aim 2). To the best of our knowledge, this study represents the first attempt to dissect cellular mechanisms of cold- adapted mechanosensation in mammals. Elucidating neural function in extreme cold has the potential to provide novel targets for combatting neuronal damage following clinical hypothermic procedures.