Sodium Leak Channels and Regulation by Neurotransmitters

描述（由申请人提供）：在本次续期申请中，我们建议扩展我们在之前资助期内对NALCN、UNC79和UNC80离子通道蛋白复合物的发现。我们发现NALCN蛋白在哺乳动物大脑中与UNC79和UNC80形成复合物，是神经元基础钠泄漏电导的主要贡献者。该通道也由神经肽通过G蛋白偶联受体控制，但以不依赖G蛋白的方式控制。敲除Nalcn或Unc79会导致新生儿死亡，并且突变的神经元不容易兴奋。UNC79和UNC80是物种间保守性较好的大型新蛋白。它们是离子通道功能所必需的。尽管它们的大小很大（约3000个氨基酸），但它们没有可识别的结构域。我们将使用生化和电生理研究来定义每个蛋白质上的相互作用域，并找出它们对离子通道功能的贡献（目标1和2）。NALCN的G蛋白非依赖性激活是非常独特的，它为剖析G蛋白偶联受体这种不寻常的离子通道激活途径提供了机会。在目标3中，我们通过揭示该途径重要的蛋白质结构域和信号传导步骤来研究这种激活的机制。这些研究的结果将帮助我们了解在自闭症、瘫痪、癫痫和癫痫等生理和病理生理条件下，神经元兴奋性是如何在分子水平上调控的。

DESCRIPTION (provided by applicant): In this renewal application, we propose to extend our discoveries during the previous funding period on the ion channel protein complex of NALCN, UNC79 and UNC80. We discovered that the NALCN protein forms a complex with UNC79 and UNC80 in mammalian brain and is a major contributor the basal sodium leak conductance in the neurons. The channel is also controlled by neuro-peptides through G protein-coupled receptors but in a G protein-independent fashion. Knocking out Nalcn or Unc79 leads to neonatal lethality and the mutant neurons are less excitable. UNC79 and UNC80 are large novel proteins well conserved among species. They are required for the ion channel function. Despite their large sizes (~3,000 amino acids), they do not have recognizable domains. We will use biochemical and electrophysiological studies to define the interaction domains on each of the proteins, and find out their contribution to the ion channel function (aims 1 and 2). NALCN's G protein-independent activation is quite unique and it provides an opportunity to dissect this unusual ion channel activation pathway by G protein-coupled receptors. In aim 3, we study the mechanisms of this activation by revealing the protein domains and the signaling steps important for the pathway. Results from these studies will help us understand how neuronal excitability is regulated at the molecular level under physiological and pathophysiological conditions such as autism, paralysis, seizure and epilepsy.