Functions of a novel astrocyte calcium signal

描述（由申请人提供）：星形胶质细胞遍布大脑，并发挥有据可查的生理作用。星形胶质细胞的新兴作用包括向神经元和从神经元发出信号以及调节局部血流。某些星形胶质细胞功能与细胞溶质钙瞬变相关或受其调节，这是一种生理信号。在上一个资助周期中，我们开发并使用了一种称为Lck-GCaMP 3的膜系遗传编码钙指示剂，目的是测量星形胶质细胞钙瞬变。使用Lck-GCaMP 3，我们偶然发现了星形胶质细胞中由TRPA 1离子通道介导的跨膜通量引起的新型钙信号。此外，我们正在进行的实验表明，TRPA 1介导的钙通量引起频繁和高度局部化的近膜钙信号，其不仅在单个星形胶质细胞内，而且在细胞培养物中的星形胶质细胞和神经元网络中以及急性脑切片中显著地促进星形胶质细胞的静息钙水平。我们的初步数据还表明，TRPA 1通道的药理学阻断或遗传缺失降低了对中间神经元的抑制性突触功效和对锥体神经元的Schaffer侧支突触的长时程突触增强。我们有三个具体的目标，我们寻求进一步扩展这些发现，测试新的假设和评估星形胶质细胞TRPA 1介导的钙信号的功能。在目标1中，我们将研究海马脑片内星形胶质细胞的近膜钙信号。在目标2中，我们将采用各种方法系统地评估为什么阻断星形胶质细胞TRPA 1通道或缓冲星形胶质细胞钙水平低于静息状态会降低对中间神经元的抑制性突触功效，但不会降低对放射层（s.r.）中锥体神经元的抑制性突触功效。海马体的一部分。在目标3中，我们将研究如何通过阻断TRPA 1通道来降低长时程增强（LTP）。通过完成这些实验，我们将提供新的星形胶质细胞钙信号的功能的新信息。这些信息将大大有助于我们 这一发现有助于理解神经元网络中的星形胶质细胞，并使我们和其他人能够测试关于近膜Ca 2+信号在星形胶质细胞-神经元信号传导中的作用的新假设，并为确定TRPA 1通道是否是涉及星形胶质细胞的脑疾病中的有效药物靶标奠定基础。

DESCRIPTION (provided by applicant): Astrocytes are found throughout the brain and play well documented physiological roles. Emerging roles for astrocytes include signaling to and from neurons and regulation of local blood flow. Certain astrocyte functions are correlated with or regulated by cytosolic calcium transients, which are a physiological signal. During the previous grant cycle, we developed and used a membrane tethered genetically encoded calcium indicator called Lck-GCaMP3 with the aim of measuring astrocyte calcium transients. Using Lck-GCaMP3 we made the serendipitous discovery of a novel calcium signal in astrocytes due to transmembrane fluxes mediated by TRPA1 ion channels. Moreover, our ongoing experiments show that TRPA1 mediated calcium fluxes give rise to frequent and highly localized near membrane calcium signals that contribute significantly to the resting calcium levels of astrocytes not only within a single astrocyte, but also in a network of astrocytes and neurons in cell cultures, as well as in acute brain slices. Our preliminary data also show that pharmacological block or genetic deletion of TRPA1 channels reduced inhibitory synapse efficacy onto interneurons and long term synaptic potentiation of Schaffer collateral synapses onto pyramidal neurons. We have three specific aims with which we seek to further extend these findings, test novel hypotheses and evaluate the function of astrocyte TRPA1 mediated calcium signals. In Aim 1 we will study near membrane calcium signals in astrocytes within hippocampal slices. In Aim 2 we will employ a variety of methods to systematically evaluate why blocking astrocyte TRPA1 channels or buffering astrocyte calcium levels below rest reduces inhibitory synapse efficacy onto interneurons, but not pyramidal neurons in the stratum radiatum (s.r.) of the hippocampus. In Aim 3 we will study how long-term potentiation (LTP) is reduced by blocking TRPA1 channels. By completing these experiments we will provide new information on the function of a novel astrocyte calcium signal. This information will contribute significantly to our understanding of astrocytes in neuronal networks and allow us and others to test novel hypotheses on the roles of near membrane Ca2+ signals in astrocyte-neuron signaling, and lay the foundations for determining if TRPA1 channels are valid drug targets in brain disorders that involve astrocytes.