New Modulators of Na, K-ATPase in the CNS

描述（由申请人提供）：本提案旨在测试一种用于调节中枢神经系统钠泵的创新新范例。钠泵（Na， k - atp酶）消耗了大脑消耗的全部能量的一半。它在缺血组织中被稳定抑制，从而增强兴奋毒性。它通过对Na和K的调节以及对膜电位的电性贡献来参与神经和胶质生理。有很多证据表明，它是由递质和激素积极调节的，但令人沮丧的是，其机制在分子和生化水平上仍然难以捉摸。我们最近表明，肾脏的Na， k - atp酶“γ亚基”作为辅助蛋白，通过降低Na和k的亲和力来调节Na， k - atp酶。其他研究表明，同源物CHIF对肾钠泵特性具有功能相反的作用，两者在不同的肾单元段中表达。这些蛋白质在大脑中不表达，但我们已经确定了另外五种同源蛋白。我们将测试新的假设，即它们都是Na， k - atp酶调节因子。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作用和不同的调控机制。在我们的初步数据中，我们表明其中一个同源物仅限于小脑皮层分子层，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酶异构体相互作用，并对Na， k - atp酶特性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，需要试点数据来实现从序列到生物学的过渡。这项工作有望在大脑运输和能量代谢的调节方面取得重大突破，并可能导致神经保护疗法，从而恢复中风后高危组织中的钠泵活性。

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.