STUDIES OF P2X ATP RECEPTORS

配体门控离子通道对大脑功能至关重要。这些 蛋白质通过开放离子，快速传递从一个神经元到下一个神经元的信号。 表面膜上的选择性孔对结合的响应 神经递质，从而引发引起电刺激的离子流 或者是抑制。当配基门控通道花费太多或太少时间时 打开时，大脑无法正确处理信息。此外，更改 在配基门控通道活动中会导致明显的神经疾病， 包括癫痫和神经退行性疾病。因此，重要的是要 了解允许通道正确打开的分子机制。这个 这里描述的工作的重点是一类由 细胞外的ATP，被称为P2X受体。编码七种基因 不同的P2X受体在哺乳动物的大脑中表达。了解 特异性P2X受体在正常脑功能和脑疾病中的作用 由于亚基特异性配体的缺失而受阻。尤其是， P2X2亚基在大脑中广泛表达，但其作用尚不清楚。 在目标1中，我们将使用一种新的随机突变策略来获取信息 关于P2X受体的结构和功能。这种方法应该 产生大量新的突变受体，这些受体不能被识别 任何其他策略。特别是，这些实验将提供重要的新的 有关ATP结合位点的信息，这将在 开发新的、更有选择性的试剂。 在目标2中，我们将探索ATP能够打开P2X2的机制 野生型和突变型受体中受体通道的详细研究 频道录制。这些单通道录音将允许我们测试 不同的受体激活模式。了解P2X2通道是如何打开的 而CLOSE对于了解脑损伤具有潜在的重要意义。 大量证据表明，NMDA类谷氨酸的过度活性 受体是脑损伤的主要原因。与NMDA受体一样，P2X2受体 形成受低pH和高锌调节的钙离子通透通道。 然而，这些调节剂抑制通过NMDA受体的电流，但 增强通过P2X2受体的电流。许多神经元共同表达NMDA和 P2X2受体。因此，P2X2受体和NMDA受体的比例可能是一个关键 癫痫发作后脑环境变化的决定因素 缺血会导致兴奋性过强或过低。这有重要的后果 由于这些情况，神经元容易受到损害， 以及试图防止这种损害的策略。

Ligand-gated ion channels are critical to brain function. These proteins mediate rapid signaling from one neuron to the next, by opening ion selective pores in the surface membrane in response to the binding of neurotransmitter, and thus eliciting ion flows that cause electrical excitation or inhibition. When ligand-gated channels spend too much or too little time open, the brain cannot process information correctly. Furthermore, alterations in ligand-gated channel activity can result in overt neurological disease, including epilepsy and neurodegenerative diseases. It is thus important to understand the molecular mechanisms that allow channels to open properly. The focus of the work described here is on a class of channels gated by extracellular ATP, which are referred to as P2X receptors. Genes encoding seven different P2X receptors are expressed in the mammalian brain. Understanding the role of specific P2X receptors in normal brain function and in brain disease has been impeded by the absence of subunit specific ligands. In particular, the P2X2 subunit is widely expressed in the brain, but its role is unclear. In Goal 1 we will use a novel random mutagenesis strategy to gain information about the structure and function of P2X receptors. This approach should generate a large number of new mutant receptors that could not be identified by any other strategy. In particular, these experiments will provide important new information about the ATP binding site, which will be of tremendous use in developing new, more selective agents. In Goal 2, we will explore the mechanism by which ATP is able to open P2X2 receptor channels in wild type and mutant receptors in detail using single channel recording. These single channel recordings will allow us to test distinct models of receptor activation. Understanding how P2X2 channels open and close is potentially of great significance for understanding brain injury. A great deal of evidence suggests that overactivity of NMDA-class glutamate receptors is a major cause of brain injury. Like NMDA receptors, P2X2 receptors form calcium permeable channels that are modulated by low pH and elevated Zn. However, these modulators inhibit current through NMDA receptors, but potentiate current through P2X2 receptors. Many neurons co-express NMDA and P2X2 receptors. Thus the ratio of P2X2 receptors to NMDA receptors may be a key determinant of whether changes in the brain environment following seizures or ischemia result in hyper or hypoexcitability. This has important ramifications for which neurons are susceptible to damage as a result of these conditions, and for strategies to try to prevent this damage.