Ubiquitin mediated Na,K-ATPase degradation

描述（由申请人提供）：急性呼吸窘迫综合征（ARDS）患者的肺毛细血管水肿使其气道充盈，从而影响从气道到体循环的氧气转移。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的生存中的重要性。Na，K-ATP酶调节肺泡上皮细胞的水肿清除。研究表明，缺氧抑制离子转运，并通过尚不清楚的机制损害肺水肿清除。我们试图研究缺氧是否通过泛素/蛋白酶体或溶酶体途径诱导肺泡上皮细胞（AEC）的Na，K-ATP酶降解。我们的初步数据表明，Na，K-ATP酶的半衰期在缺氧（1.5%O2）的存在下降低，其降解被蛋白酶体和溶酶体抑制剂阻断。本提案的具体目标是具体目标#1：确定缺氧是否通过泛素途径增加Na，K-ATP酶降解。具体目标#2：确定缺氧是否通过溶酶体或蛋白酶体系统增加Na，K-ATP酶降解。具体目标#3：确定参与Na，K-ATP酶降解过程的E-2s和E-3s酶。拟定研究的完成将提供有关缺氧影响的新信息，特别是与Na，K-ATP酶抑制和降解机制以及逆转Na，K-ATP酶抑制的途径有关的信息，这可能与设计增加低氧性呼吸衰竭患者肺泡液体清除率的新策略相关。

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.