Leibniz-Institute for Molecular Pharmacology, Berlin, Germany.
J Am Soc Nephrol. 2010 Oct;21(10):1645-56. doi: 10.1681/ASN.2009111190. Epub 2010 Aug 19.
Arginine-vasopressin (AVP) modulates the water channel aquaporin-2 (AQP2) in the renal collecting duct to maintain homeostasis of body water. AVP binds to vasopressin V2 receptors (V2R), increasing cAMP, which promotes the redistribution of AQP2 from intracellular vesicles into the plasma membrane. cAMP also increases AQP2 transcription, but whether altered degradation also modulates AQP2 protein levels is not well understood. Here, elevation of cAMP increased AQP2 protein levels within 30 minutes in primary inner medullary collecting duct (IMCD) cells, in human embryonic kidney (HEK) 293 cells ectopically expressing AQP2, and in mouse kidneys. Accelerated transcription or translation did not explain this increase in AQP2 abundance. In IMCD cells, cAMP inhibited p38-mitogen-activated protein kinase (p38-MAPK) via activation of protein kinase A (PKA). Inhibition of p38-MAPK associated with decreased phosphorylation (serine 261) and polyubiquitination of AQP2, preventing proteasomal degradation. Our results demonstrate that AVP enhances AQP2 protein abundance by altering its proteasomal degradation through a PKA- and p38-MAPK-dependent pathway.
精氨酸加压素（AVP）调节肾脏集合管中的水通道 aquaporin-2（AQP2），以维持体内水的平衡。AVP 与加压素 V2 受体（V2R）结合，增加 cAMP，促进 AQP2 从细胞内囊泡重新分布到质膜。cAMP 还增加 AQP2 的转录，但改变降解是否也调节 AQP2 蛋白水平尚不清楚。在这里，cAMP 的升高在原代内髓集合管（IMCD）细胞、异位表达 AQP2 的人胚肾（HEK）293 细胞和小鼠肾脏中在 30 分钟内增加了 AQP2 蛋白水平。加速转录或翻译并不能解释 AQP2 丰度的这种增加。在 IMCD 细胞中，cAMP 通过激活蛋白激酶 A（PKA）抑制丝裂原活化蛋白激酶 p38（p38-MAPK）。p38-MAPK 的抑制与 AQP2 的磷酸化（丝氨酸 261）和多泛素化减少以及蛋白酶体降解减少相关。我们的结果表明，AVP 通过 PKA 和 p38-MAPK 依赖性途径改变其蛋白酶体降解来增强 AQP2 蛋白丰度。
