Role of SGK2 in Sodium Transport in the Kidney

描述(申请人提供)：本研究计划的总体目标是了解血清和糖皮质激素诱导的激酶2(Sgk2)的表达、调节和功能，以及它在钠(Na+)跨肾单位运输中所起的确切作用。醛固酮诱导肾单位钠离子转运的分子基础尚未完全阐明。最近，SGK1被认为是早期醛固酮效应和上皮细胞Na+通道介导的Na+转运之间的中枢调节因子。最近，又发现了SGK的另外两种亚型，sgk2和sgk3。将通过注射醛固酮和地塞米松来定位sgk2的表达并评估激素介导的sgk2调节，随后通过原位杂交和免疫细胞化学分析sgk2的表达。通过非洲爪哇卵母细胞与sgk2和肾单位段特异的Na+共转运蛋白的共表达分析，将鉴定sgk2的下游效应。最后，将构建一个四环素可诱导的(Tet-on)sgk2在A6细胞中的表达系统，以时间依赖的方式分离sgk2对Na+转运的特异性影响。考虑到不适当的Na+处理可导致细胞外液体体积膨胀和高血压，了解介导醛固酮诱导的肾脏Na+转运的信号通路具有重要的临床意义。

DESCRIPTION (provided by applicant): The overall goal of this research proposal is to understand the expression, regulation, and function of serum and glucocorticoid induced kinase 2 (sgk2) and the precise role it plays in sodium (Na+) transport across the nephron. The molecular basis underlying aldosterone-induced Na+ transport in the nephron has not been fully elucidated. Recently, sgk1 has been identified as a central mediator between early aldosterone effects and epithelial Na+ channel-mediated Na+ transport. Even more recently, two additional isoforms of sgk, sgk2 and sgk3, have been discovered. Localization of sgk2 expression and assessment of hormone-mediated sgk2 regulation will be performed through aldosterone and dexamethasone infusion in rats with subsequent sgk2 expression analyses by in situ hybridization and immunocytochemistry. Identification of downstream effectors of sgk2 will be performed through co-expression assays of Xenopus laevis oocytes with sgk2 and nephron segment-specific Na+ co-transporters. Finally, a tetracycline-inducible (Tet-On) sgk2 expression system in A6 cells will be constructed to isolate the specific effects of sgk2 on Na+ transport in a time-dependent manner. Given that inappropriate Na+ handling can result in extracellular fluid volume expansion and hypertension in humans, understanding the signaling pathways mediating aldosterone-induced Na+ transport in the kidney is clinically important.