Importance of Pannexin to Astrocyte and Neuronal ATP

 描述(申请人提供)：星形胶质细胞与所有类型的神经细胞相互作用，通过缝隙连接建立直接的细胞-细胞接触和/或通过释放调节突触活动、大脑微循环以及神经炎症和代谢反应的神经递质。在各种旁分泌信号中，嘌呤能ATP介导的信号是星形胶质细胞相互作用以及与神经元相互作用的最重要的机制。这是因为神经细胞释放并对三磷酸腺苷做出反应。细胞通过不同的机制释放三磷酸腺苷，包括离子通道。最近，无脊椎动物缝隙连接蛋白的脊椎动物同源基因PAnnexin1(Panx1)被发现形成了我们和其他人提出的释放ATP的通道。Pannexins在中枢神经系统中大量表达，在神经胶质细胞和神经元中都有表达，它们与缺血性神经元死亡和癫痫样活动有关。与已提出的Panx1通道在多动中的作用相一致，我们最近发现，使用两个Panx1全局缺失的不同小鼠系，通过这些通道释放的ATP有助于延长癫痫持续状态的临床表现。然而，关于导致Panx1介导的癫痫发作的细胞类型(星形胶质细胞或神经元)，还有一个有待回答的主要问题。因此，这项授权申请的总体目标是确定关于中枢神经系统中通过PAnnexin1通道进行的细胞间通信的关键缺失信息，包括这些通道的生物物理特性以及导致和导致Panx1激活的信号转导事件。为此，我们将使用新获得的条件性Panx1缺失小鼠，直接评估星形胶质细胞或神经元Panx1通道通过释放ATP而导致癫痫持续状态的程度，并提供对这一新类型通道的门控和信号转导事件的新机制理解。

 DESCRIPTION (provided by applicant): Astrocytes interact with all types of neural cells by establishing direct cell-cell contacts through gap junctions and/or by releasing gliotransmitters which modulate synaptic activity, brain microcirculation, as well as neuroinflammatory and metabolic responses. Among the various types of paracrine signals, purinergic ATP-mediated signaling is emerging as the most prominent mechanism by which astrocytes interact among themselves and with neurons. This is because neural cells release and respond to ATP. ATP release from cells occurs through distinct mechanisms including ion channels. Recently, Pannexin1 (Panx1), a vertebrate ortholog of invertebrate gap junction protein, was found to form channels that we and others have proposed to be the site for ATP release. Pannexins are abundantly expressed in the CNS, both in glia and neurons, where they have been implicated in ischemic neuronal death and epileptiform activity. In concordance with the proposed role of Panx1 channels in hyperactivity, we recently found, using two different mouse lines with global Panx1 deletion that ATP release through these channels contributes to prolong the clinical manifestations of status epilepticus. A main question that remains to be answered, however, regards the cell type (astrocyte or neuron) that contributes to Panx1-mediated seizures. Thus, the overall aim of this grant application is to determine key missing information regarding cell-cell communication via Pannexin1 channels in the CNS, including the biophysical properties of these channels and the signal transduction events both leading to and resulting from Panx1 activation. For that we will use newly available conditional Panx1-null mice to directly evaluate the extent to which astrocyte or neuronal Panx1 channels contribute to status epilepticus by releasing ATP and to provide new mechanistic understanding of gating and signal transduction events of this new type of channel.