Dexamethasone increases aquaporin-2 protein expression in ex vivo inner medullary collecting duct suspensions.
Dexamethasone increases aquaporin-2 protein expression in ex vivo inner medullary collecting duct suspensions.
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DOI：
10.3389/fphys.2015.00310
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发表时间：
2015
影响因子：
4
通讯作者：
Chen G
中科院分区：
文献类型：
--
作者：
Chen M;Cai H;Klein JD;Laur O;Chen G
水通道蛋白-2 （Aquaporin-2, AQP2）是抗利尿激素调控的水通道，控制肾脏水分重吸收，在维持机体水分稳态中起重要作用。过量的糖皮质激素常见于库欣综合征，可引起水潴留。然而，糖皮质激素是否以及如何调节AQP2仍不清楚。在本研究中，我们检测了地塞米松对AQP2蛋白表达和活性的直接影响。地塞米松增加大鼠髓内集管（IMCD）悬液中AQP2蛋白丰度。这在转染AQP2 cDNA的HEK293细胞中得到证实。细胞表面蛋白生物素化使地塞米松诱导的细胞膜AQP2表达增加，这种作用被糖皮质激素受体拮抗剂RU486阻断。在功能上，通过观察细胞在低渗透溶液中的破裂时间（地塞米松组为66±13秒，对照组为101±11秒，n = 15）来判断，注射AQP2 cRNA的卵母细胞在地塞米松处理下增加了水转运活性。我们进一步发现，地塞米松治疗降低了AQP2蛋白的降解，这可能导致AQP2蛋白的增加。有趣的是，地塞米松促进细胞膜AQP2向浮力较小的脂筏亚微域移动。综上所述，我们的数据表明地塞米松主要通过抑制AQP2蛋白的降解来促进AQP2蛋白的表达并增加水的渗透性。AQP2活性的增加促进水重吸收，这可能有助于糖皮质激素诱导的水潴留和高血压。
Aquaporin-2 (AQP2) is the vasopressin-regulated water channel that controls renal water reabsorption and plays an important role in the maintenance of body water homeostasis. Excessive glucocorticoid as often seen in Cushing's syndrome causes water retention. However, whether and how glucocorticoid regulates AQP2 remains unclear. In this study, we examined the direct effect of dexamethasone on AQP2 protein expression and activity. Dexamethasone increased AQP2 protein abundance in rat inner medullary collecting duct (IMCD) suspensions. This was confirmed in HEK293 cells transfected with AQP2 cDNA. Cell surface protein biotinylation showed an increase of dexamethasone-induced cell membrane AQP2 expression and this effect was blocked by glucocorticoid receptor antagonist RU486. Functionally, dexamethasone treatment of oocytes injected with an AQP2 cRNA increased water transport activity as judged by cell rupture time in a hypo-osmotic solution (66 ± 13 s in dexamethasone vs. 101 ± 11 s in control, n = 15). We further found that dexamethasone treatment reduced AQP2 protein degradation, which could result in an increase of AQP2 protein. Interestingly, dexamethasone promoted cell membrane AQP2 moving to less buoyant lipid raft submicrodomains. Taken together, our data demonstrate that dexamethasone promotes AQP2 protein expression and increases water permeability mainly via inhibition of AQP2 protein degradation. The increase in AQP2 activity promotes water reabsorption, which may contribute to glucocorticoid-induced water retention and hypertension.