Transcriptional regulation and cellular trafficking of aquaporin-2 water channel

我们在体外和体内系统中研究了水通道蛋白-2（AQP-2）的水通道调控机制。(1)体外研究：将小鼠AQP-2基因5 ′侧翼区的多个片段（约9.5kb）克隆到荧光素酶（Luc）报告质粒中，并将它们瞬时转染MDCK或mIMCD 3细胞。高渗反应增强子至少存在于两个区段，即张力反应增强子（TonE）（-570 bp-560 bp）和AQP-2基因5 '侧翼区-6.1 ~-4.3 kb的未知区。后者具有与TonE不同的结构和高渗反应机制。它们独立于精氨酸加压素（AVP）调节AQP-2的转录调节。在-6.1 ~-4.3kb之间的区域主要接受高渗信号，但其调节作用进一步与TonE协同激活AQP-2基因的转录。相反，TonE本身可能参与低渗调节的AQP-2转录。 ...更多信息 低渗本身不改变Luc的基础活性，但减弱cAMP诱导的Luc活性。该作用通过JNK介导。这些结果表明，张力反应增强子位于AQP-2的5 '侧翼区域，并调节高和低张力诱导的AQP-2转录。(2)体内研究：我们检测了衰老是否影响糖皮质激素缺乏大鼠肾脏AQP-2的表达。糖皮质激素缺乏大鼠的水排泄功能也受到影响，但老年大鼠的水排泄功能受损较青年大鼠更为严重。老年大鼠肾脏AQP-2表达减少。糖皮质激素缺乏大鼠血浆AVP未被充分抑制，肾脏AQP-2 mRNA和蛋白表达在糖皮质激素缺乏老年大鼠中显著上调。目前的研究结果表明，AQP-2的上调对衰老起着至关重要的作用，在水排泄的持续损害，依赖于非抑制释放的AVP，在老年大鼠糖皮质激素缺乏症。少

We had examined the regulatory mechanism of aquaporin-2 (AQP-2) water channel in both in vitro and in vivo systems. (1) in vitro study : Various fragments of 5'-flanking region of murine AQP-2 gene up to -9.5 kb were cloned into a luciferase (Luc) reporter plasmid, and they were transiently transfected into MDCK or mIMCD3 cells. Hypertonicity-response enhancers were at least resided at two segments, namely tonicity-response enhancer (TonE)(-570〜-560bp) and unknown region between -6.1 and -4.3 kb of the 5'-flanking region of AQP-2 gene. The latter had the different structure and mechanism of response to hypertonicity from those of TonE. They regulated AQP-2 transcriptional regulation independently of arginine vasopressin (AVP). The region between -6.1 and -4.3 kb dominantly received hypertonicity signal, but its regulation further collaborated with TonE to activate the transcription of AQP-2 gene. On the contrary, TonE per se could be involved in hypotonicity-regulated AQP-2 transcripti … More on. Hypotonicity per se did not alter basal activity of Luc, but attenuated cAMP-induced Luc activity. This action was mediated through JNK. These findings indicate that tonicity-response enhancers are located at the 5'-flanking region of AQP-2, and regulate hyper- and hypotonicity-induced AQP-2 transcription. (2) in vivo study : We examined whether aging affects kidney expression of AQP-2 in glucocorticoid-deficient rats. Impaired water excretion was found in glucocorticoid-deficient rats, but its impairment was much serious in the aged rats compared with the young ones. Kidney AQP-2 expression was reduced in the aged rats. Plasma AVP was not sufficiently suppressed in the glucocorticoid-deficient t rats, and the expression of kidney AQP-2 mRNA and protein were rather upregulated in the aged rats with glucocorticoid deficiency. The present findings indicate that the upregulation of AQP-2 against aging plays a crucial role in persistent impairment in water excretion, dependent upon non-suppressible release of AVP, in aged rats with glucocorticoid deficiency. Less