Loss of calcineurin Aα results in altered trafficking of AQP2 and in nephrogenic diabetes insipidus
Loss of calcineurin Aα results in altered trafficking of AQP2 and in nephrogenic diabetes insipidus
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DOI：
10.1242/jcs.02971
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发表时间：
2006-06-15
影响因子：
4
通讯作者：
Toro, Juan J.
中科院分区：
文献类型：
--
作者：
Gooch, Jennifer L.;Guler, Rebecca L.;Toro, Juan J.
丝氨酸/苏氨酸磷酸酶钙调神经磷酸酶是参与肾脏发育和功能的重要信号分子。钙调神经磷酸酶作用的一个潜在靶点是水通道水通道蛋白2(AQP2)。在这项研究中，我们在体内检测了钙调神经磷酸酶Aα(CNAα)缺失对AQP2功能的影响。CNAα基因缺失的小鼠出生后排尿能力有缺陷，对加压素的排尿反应受损。AQP2的表达是正常的，但矛盾的是，与野生型相比，血管加压素介导的通道磷酸化水平降低，并且AQP2没有在顶膜上积累。在内髓集合管小泡中发现钙调神经磷酸酶的蛋白和活性，钙调神经磷酸酶的表达和活性的丧失与小泡部分AQP2的丢失有关。因此，血管加压素介导的AQP2磷酸化缺失可能是AQP2正常转运到心尖靶向小泡的缺陷所致。同样，用环孢菌素A抑制钙调神经磷酸酶治疗野生型小鼠，会产生类似的对加压素的尿浓缩反应以及AQP2磷酸化和运输的改变。这些实验表明，CNAα是AQP2正常细胞内运输所必需的，钙调神经磷酸酶蛋白或活性的丧失会扰乱AQP2的功能。
The serine/threonine phosphatase calcineurin is an important signaling molecule involved in kidney development and function. One potential target of calcineurin action is the water channel aquaporin 2 (AQP2). In this study, we examined the effect of loss of calcineurin A alpha (CnA alpha) on AQP2 function in vivo. CnA alpha null mice were found to have defective post-natal urine-concentrating ability and an impaired urine-concentrating response to vasopressin. Expression of AQP2 is normal but, paradoxically, vasopressin-mediated phosphorylation of the channel is decreased compared with wild-type littermates and there is no accumulation of AQP2 in the apical membrane. Calcineurin protein and activity was found in innermedullary collecting duct vesicles, and loss of calcineurin expression and activity was associated with a loss of AQP2 in the vesicle fraction. As such, the lack of vasopressin-mediated phosphorylation of AQP2 might be the result of a defect in normal trafficking of AQP2 to apical-targeted vesicles. Likewise, treatment of wild-type mice with cyclosporin A to inhibit calcineurin produces a similarly impaired urine-concentrating response to vasopressin and alterations in AQP2 phosphorylation and trafficking. These experiments demonstrate that, CnA alpha is required for normal intracellular trafficking of AQP2 and loss of calcineurin protein or activity disrupts AQP2 function.