Sodium Leak Channels and Regulation by Neurotransmitters

描述（由申请人提供）：本提案的重点是钠泄漏通道（NALCN）及其在神经系统中的神经递质调控。NALCN离子通道与十个电压门控钙离子通道和十个钠离子通道同属一个家族。然而，NALCN通道是非选择性的（可渗透到钠、钙和钾），并且通道的激活与电压无关。在缺乏通道基因的突变小鼠中，存在呼吸节律缺陷，突变动物不能存活超过出生24小时。因此，NALCN是动物生存不可或缺的少数离子通道之一。突变海马神经元缺乏对铯和ttx不敏感的钠泄漏电流，神经元的膜电位对细胞外钠浓度的变化不敏感。利用Northern blot和原位杂交技术，对该基因在动物体内的表达进行定位。目的2将确定NALCN独特离子选择性的分子机制。Aim 3将使用膜片钳比较野生型和突变型神经元的兴奋性，并确定NALCN通道对神经元兴奋性的贡献。目的4将研究NALCN通道如何受神经递质调节。这些研究的结果将揭示这一重要基因的生理作用。它们还可能揭示蛋白质的功能如何影响生理和病理生理条件下的神经元兴奋性，如瘫痪、发作和癫痫。

DESCRIPTION (provided by applicant): This proposal focuses on a sodium leak channel (NALCN) and its regulation by neurotransmitters in the nervous systems. NALCN ion channel belongs to the family that also includes the ten voltage-gated calcium channels and ten sodium channels. However, the NALCN channel is non-selective (permeable to sodium, calcium and potassium), and the channel's activation is voltage-independent. In the mutant mice deficient in the channel gene, there is defect in breathing rhythm and the mutant animals do not survive beyond 24 hours of birth. Thus, NALCN is one of the few ion channels indispensable for animal's survival. The mutant hippocampal neurons lack the cesium and TTX-insensitive sodium leak current and the neurons' membrane potential is little sensitive to changes in extracellular sodium concentrations. Using Northern blot and in situ hybridization, aim 1 will localize the gene expression in the animal. Aim 2 will determine the molecular mechanisms underlying NALCN's unique ion selectivity. Aim 3 will use patch clamp to compare the excitabilities of the wild-type and the mutant neurons and determine the contribution of NALCN channel to neuronal excitability. Aim 4 will examine how the NALCN channel is regulated by neurotransmitters. Results from these studies will reveal the physiological roles of this vital gene. They may also reveal how the function of the protein can influence neuronal excitabilities in physiological and pathophysiological conditions such as paralysis, seizure and epilepsy.