Aquaporin-2 (AQP2) Regulation by AMP-activated kinase(AMPK) in the Kidney Collec

描述（由申请方提供）：肾集合管上皮主细胞中表达的水通道蛋白-2（AQP 2）对于维持总体积稳态至关重要。激素精氨酸加压素（AVP;或抗利尿激素）作为对血清渗透压升高或血压降低的正常反应从下丘脑/垂体分泌。在主细胞中，AVP通过血管加压素受体II型（V2 R）起作用，导致涉及cAMP/PKA、AQP 2磷酸化、含AQP 2囊泡的顶膜插入和水从尿液重吸收到回肠的级联反应。AQP 2的运输和亚细胞定位是由AQP 2 C-末端的几个Ser残基的磷酸化状态以及泛素化状态介导的。事实上，对AQP 2调节的研究已经揭示了诸如肾源性尿崩症（NDI）、SIADH和心力衰竭等疾病的发病机制。我们的初步数据表明，代谢传感器AMP激活的激酶（AMPK），这是上调代谢应激（例如，在缺血期间），防止肾切片中离体的急性PKA介导的AQP 2顶端积累。此外，显性负性AMPK加速AQP 2介导的卵母细胞在低渗休克时的肿胀，表明AMPK活性的抑制刺激AQP 2功能。我们假设AMPK通过直接磷酸化或调节PKA介导的AQP 2磷酸化诱导细胞内AQP 2的积累，并在代谢应激期间促进AQP 2泛素化和降解。我们的目的是研究AMPK依赖性磷酸化调节AQP 2运输和功能的机制，并研究AMPK在增强AQP 2的泛素化、胞质再分布和降解中的作用。我们将确定哪些AQP 2残基被AMPK通过质谱磷酸化，以及这些残基在卵母细胞和mpkCCDc 14细胞中对该水通道的亚细胞定位和活性的作用。我们还将确定AMPK是否增加肾脏切片和mpkCCDc 14细胞中AQP 2的泛素化和降解。最后，我们将确定AMPK抑制是否阻止AQP 2在肾切片和mpkCCDc 14细胞化学缺血后的再分布和/或降解。这一提议提出了一种新的潜在机制，即缺血期间发生的代谢应激调节AQP 2。我们的研究可能有助于更好地了解体内水分平衡如何与心脏和肾脏等重要器官的代谢和病理学相结合。 公共卫生相关性：水通道蛋白-2（AQP 2）是一种表达于肾脏上皮细胞的水通道，对维持总体积的动态平衡至关重要。AQP 2的研究为肾性尿崩症、抗利尿激素释放不当综合征和心力衰竭的发病机制提供了新的线索。我们推测AMPK在急性肾缺血时被缺血激活，调节AQP 2的丰度和功能。我们的研究应该有助于更好地了解体内水分平衡如何与代谢和肾脏病理学相结合。此外，它还可以为治疗重要的身体水分平衡紊乱，如肾源性尿崩症提供见解。

DESCRIPTION (provided by applicant): Aquaporin-2 (AQP2) expressed in kidney collecting duct epithelial principal cells is essential for the maintenance of total body volume homeostasis. The hormone arginine vasopressin (AVP; or antidiuretic hormone) is secreted from the hypothalamus/pituitary as a normal response to increased serum osmolality or decreased blood pressure. In principal cells, AVP acts via the vasopressin receptor type II (V2R), leading to a cascade involving cAMP/PKA, AQP2 phosphorylation, apical membrane insertion of AQP2-containing vesicles and water reabsorption from the urine into the interstitium. AQP2 trafficking and subcellular localization are mediated by the phosphorylation status of several Ser residues in the AQP2 C-terminus as well as by ubiquitination status. Indeed, research on AQP2 regulation has shed light on the pathogenesis of diseases such as nephrogenic diabetes insipidus (NDI), SIADH and heart failure. Our preliminary data show that the metabolic sensor AMP-activated kinase (AMPK), which is upregulated by metabolic stress (e.g., during ischemia), prevents acute PKA-mediated AQP2 apical accumulation ex vivo in kidney slices. In addition, dominant-negative AMPK accelerates AQP2-mediated oocyte swelling upon hypotonic shock, suggesting that inhibition of AMPK activity stimulates AQP2 function. We hypothesize that AMPK induces intracellular accumulation of AQP2, either via direct phosphorylation or by modulating PKA-mediated AQP2 phosphorylation, and promotes AQP2 ubiquitination and degradation during periods of metabolic stress. Our aims are to examine the mechanisms by which AMPK-dependent phosphorylation regulates AQP2 trafficking and function and to examine the role of AMPK in enhancing the ubiquitination, cytoplasmic redistribution, and degradation of AQP2. We will determine which AQP2 residues are phosphorylated by AMPK by mass spectrometry and the role of those residues on the subcellular localization and activity of this water channel in oocytes and mpkCCDc14 cells. We will also determine whether AMPK increases AQP2 ubiquitination and degradation in kidney slices and in mpkCCDc14 cells. Finally, we will determine whether AMPK inhibition prevents AQP2 redistribution and/or degradation in kidney slices and mpkCCDc14 cells following chemical ischemia. This proposal addresses a novel potential mechanism by which metabolic stress, as occurs during ischemia, regulates AQP2. Our research will likely contribute to a better understanding of how body water homeostasis may be coupled to metabolism and pathology of vital organs such as heart and kidney. PUBLIC HEALTH RELEVANCE: Aquaporin-2 (AQP2), a water channel expressed in kidney epithelium, is essential for the maintenance of total body volume homeostasis. Research on AQP2 has shed light on the pathogenesis of nephrogenic diabetes insipidus, the syndrome of inappropriate antidiuretic hormone release, and heart failure. We hypothesize that AMPK, which is activated by ischemia, regulates AQP2 abundance and function during acute kidney ischemia. Our research should contribute to a better understanding of how body water homeostasis may be coupled to metabolism and kidney pathology. In addition, it may provide insight into the treatment of important body water balance disorders like nephrogenic diabetes insipidus.