Molecular Pathopbysiological Reseatch of ubiquitin ligase,human Nodd4L, for the development ofessentialhyportension

人体的净钠平衡是通过沿着整个肾单位表达的各种离子转运蛋白来维持的。在这些离子转运体中，位于沿着的醛固酮敏感性远端肾单位（ASDN）的上皮钠通道（ENaC）在钠的稳态中起着关键作用。平衡这一点得到了遗传性高血压疾病分析的支持，显示编码ENaC和其他调节蛋白的基因引起遗传性高血压，如Liddle综合征。在各种调节蛋白中，E8泛素连接酶Nedd4L结合ENaC COOH末端的PY基序并催化蛋白质的NH末端的泛素化用于随后的降解。Nedd4L是一种隐性剪接变异体，其编码的C2结构域既有进化上的保守结构域，又有进化上的新结构域。本文以SNP（rs4149601）产生的亚型Ⅰ为研究对象，采用分子生物学、免疫组织化学和电生理学方法，研究了其表达及其与其他亚型的相互作用。我们发现，亚型I可能与其他人类亚型在显性负性的方式。这些相互作用可能会异常增加钠重吸收。综上所述，我们的分析表明，人类Nedd4L基因，特别是进化上新的亚型I，是高血压的候选基因。

Net sodium balances in humans are maintained through various ion transporters expressed along the entire nephron. Among these ion transporters, epithelial sodium channels (ENaC) located along the aldosterone-sensitive distal nephron(ASDN)play a pivotal role in the homeostasis of sodium. balance. This is supported by analyses of inherited hypertensive disorders, showing that genes encoding ENaC and other modulatory proteins cause hereditary hypertension, such as Liddle's syndrome. Among various modulating proteins, E8 ubiquitin ligase, Nedd4L, binds the PY motif of ENaC COOH terminals and catalyzes ubiquitilation of the NH terminal of the protein for subsequent degradation. Both evolutionarily conserved and evolutionarily new C2 domains of human Nedd4L, a cryptic splice variant resulting in a disrupted isoform product formed by a frame shift mutation, were reported previously, We focused on one of the isoforms, isoform I, generated by SNP (rs4149601), and studied its expression and interactions with other isoforms by molecular biological, immmohistochemical, and electrophysiological methods. We found that isoform I may interact with other human isoforms in a dominant-negative fashion. Such interactions might abnormally increase sodium reabsorption, Taken together, our analyses suggest that the human Nedd4L gene, especially the evolutionerily new isoform I, is a candidate gene for hypertension.