New Modulators of Na, K-ATPase in the CNS

描述（由申请人提供）：本提案旨在测试CNS钠泵调节的创新新范例。钠泵（Na，K-ATP酶）消耗大脑中使用的所有能量的一半。它在缺血组织中被稳定抑制，这增强了兴奋性毒性。它通过调节Na和K及其对膜电位的产电作用而对神经和神经胶质生理学做出贡献。有很多证据表明，它是积极调节的递质和激素，但机制仍然令人沮丧的难以捉摸的分子和生化水平。我们最近发现，肾脏的Na，K-ATP酶“γ亚基”作为辅助蛋白，通过降低其对Na和K的亲和力来调节Na，K-ATP酶。其他人已经表明，同源物CHIF对肾钠泵特性具有功能上相反的作用，并且两者在不同的肾单位节段中表达。这些蛋白质在大脑中不表达，但我们已经确定了其他五种同源物。我们将测试新的假设，它们都是Na，K-ATP酶调节剂。同源物（FXYD基因家族）共享一个保守的中央膜结构域，但具有不同的细胞外和细胞内结构域。这预示着它们具有不同的功能效应，并受到不同调节机制的靶向。在我们的初步数据中，我们发现其中一个同源物仅限于小脑皮质分子层，并且它确实与Na，K-ATP酶相关。我们将确定其他同源物是否具有不同的细胞分布，与不同的Na，K-ATP酶同工型相互作用，以及对Na，K-ATP酶性质具有不同的功能影响。其中两个是在我们的基因组研究中首次发现的新基因产物，需要试点数据才能实现从序列到生物学的过渡。这项工作有望为大脑中运输和能量代谢的调节提供重大突破，并可能导致神经保护治疗，可以恢复中风后危险组织中的钠泵活性。

DESCRIPTION (provided by applicant): This proposal aims to test an innovative new paradigm for the regulation of the sodium pump in the CNS. The sodium pump (Na,K-ATPase) consumes half of all the energy used in the brain. It is stably inhibited in ischemic tissue, which potentiates excitotoxicity. It contributes to neural and glial physiology through its regulation of Na and K and its electrogenic contribution to membrane potential. There is much evidence that it is actively regulated by transmitters and hormones, but the mechanisms remain frustratingly elusive at the molecular and biochemical level. We have recently shown that the Na,K-ATPase "gamma subunit" of the kidney acts as an accessory protein, modulating the Na,K-ATPase by reducing its affinity for Na and K. Others have shown that a homologue, CHIF, has a functionally opposite effect on kidney sodium pump properties, and the two are expressed in different nephron segments. These proteins are not expressed in the brain, but we have identified five other homologs that are. We will test the new hypothesis that they are all Na,K-ATPase regulators. The homologs (the FXYD gene family) share a conserved central membrane domain, but have divergent extracellular and intracellular domains. This predicts that they have different functional effects and are targeted by different regulatory mechanisms. In our preliminary data we show that one of the homologs is restricted to the cerebellar cortex molecular layer, and that it indeed associates with Na, K-ATPase. We will determine whether the other homologs have different cellular distributions, interact with different Na,K-ATPase isoforms, and have different functional effects on Na, K-ATPase properties. Two of them are new gene products that were first identified in our genomic studies, and pilot data are needed to make the transition from sequence to biology. The work promises to provide a significant breakthrough in the regulation of transport and energy metabolism in the brain, and may lead to neuroprotective therapy that could restore sodium pump activity in tissue-at-risk after stroke.