Ubiquitin mediated Na,K-ATPase degradation

描述(申请人提供)：急性呼吸窘迫综合征(ARDS)患者的呼吸空间充斥着来自肺毛细血管的水肿，从而影响氧气从呼吸空间向体循环的转移。最近的研究表明，主动钠转运和肺水肿清除在呼吸衰竭患者生存中的重要性。Na，K-ATPase调节肺泡上皮细胞的水肿清除。已有研究表明，低氧抑制离子转运，损害肺水肿清除，其机制尚不清楚。我们试图研究低氧是否通过泛素/蛋白酶体或溶酶体途径诱导肺泡上皮细胞(AEC)Na，K-ATPase降解。我们的初步数据显示，在低氧(1.5%O2)存在时，Na，K-ATPase的半衰期减少，其降解被蛋白酶体和溶酶体抑制剂阻断。这项建议的具体目的是具体目标1：确定缺氧是否通过泛素途径增加Na，K-ATPase的降解。具体目标#2：确定低氧是否通过溶酶体或蛋白酶体系统增加Na，K-ATPase的降解。具体目的#3：确定参与Na，K-ATPase降解过程的E-2S和E-3S酶。这些研究的完成将为低氧的影响提供新的信息，特别是关于Na，K-ATPase的抑制和降解的机制以及逆转Na，K-ATPase抑制的途径，这可能对设计新的策略来增加缺氧性呼吸衰竭患者的肺泡液清除有关。

DESCRIPTION (provided by applicant): Patient with acute respiratory distress syndrome (ARDS) have their airspaces flooded with edema from pulmonary capillaries thus compromising oxygen transfer from the airspaces into the systemic circulation. Recent investigations have demonstrated the importance of active sodium transport and lung edema clearance in the survival of patients with respiratory failure. The Na,K-ATPase regulates edema clearance across the alveolar epithelium. It has been shown that hypoxia inhibits ion transport and impairs lung edema clearance by yet unclear mechanisms. We sought to study whether hypoxia induces Na,K-ATPase degradation in alveolar epithelial cells (AEC) via the ubiquitin/proteasome or lysosomal pathways. Our preliminary data shows that Na,K-ATPase half life is decreased in the presence of hypoxia (1.5% O2) and its degradation is blocked by proteasomal and lysosomal inhibitors. The specific aims of this proposal are Specific aim # 1:To determine whether hypoxia increases Na,K-ATPase degradation via ubiquitin pathway. Specific aim #2: To determine whether hypoxia increases Na,K-ATPase degradation via the lysosome or proteasome system. Specific aim #3: To determine the E-2s and E-3s enzymes involved in the degradation process of the Na,K-ATPase. Completion of the proposed studies will provide novel information on the effects of hypoxia, specifically as it pertains to mechanisms of inhibition and degradation of the Na,K-ATPase as well as pathways of reversal Na,K-ATPase inhibitions, which may be of relevance for the design of novel strategies to increase alveolar fluid clearance in patients with hypoxemic respiratory failure.