IRBIT governs epithelial secretion in mice by antagonizing the WNK/SPAK kinase pathway
IRBIT governs epithelial secretion in mice by antagonizing the WNK/SPAK kinase pathway
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DOI：
10.1172/jci43475
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发表时间：
2011-03-01
影响因子：
15.9
通讯作者：
Muallem, Shmuel
中科院分区：
文献类型：
--
作者：
Yang, Dongki;Li, Qin;Muallem, Shmuel
液体和HCO 3-分泌是上皮细胞的基本功能，并决定体液体积和离子组成等。分泌腺中导管液和HCO 3-的分泌是由基底外侧溶质载体家族4成员4（NBCe 1-B）介导的Na+/HCO 3-共转运和由管腔溶质载体家族26成员6（S1 c 26 a 6）和CFTR介导的Cl-/HCO 3-交换来提供动力的。然而，控制导管分泌的机制尚不清楚。在这里，我们已经表明，在小鼠胰腺导管分泌抑制NBCe 1-B/CFTR激活剂肌醇-1，4，5-三磷酸（IP 3）受体结合蛋白（伊尔比特）与IP 3（IRBIT）释放的沉默和蛋白磷酸酶1（PP 1）的抑制。与此相反，沉默无赖氨酸（WNK）激酶和Ste 20相关的脯氨酸/丙氨酸丰富的激酶（SPAK）增加分泌。分子分析显示，WNK激酶作为支架募集SPAK，SPAK磷酸化CFTR和NBCe 1-B，降低它们的细胞表面表达。伊尔比特通过将PP 1募集到复合物中以使CFTR和NBCe 1-B去磷酸化，恢复它们的细胞表面表达，以及刺激它们的活性来对抗WNK和SPAK的作用。由于单独沉默伊尔比特，在相同导管中沉默SPAK和伊尔比特拯救了导管分泌。这些发现强调了伊尔比特在上皮液和HCO 3-分泌中的关键作用，并提供了伊尔比特协调这些过程的分子机制。它们还与参与全身液体稳态、高血压和囊性纤维化的WNK/SPAK激酶调节过程有关。
Fluid and HCO3- secretion are fundamental functions of epithelia and determine bodily fluid volume and ionic composition, among other things. Secretion of ductal fluid and HCO3- in secretory glands is fueled by Na+/HCO3- cotransport mediated by basolateral solute carrier family 4 member 4 (NBCe1-B) and by Cl-/HCO3- exchange mediated by luminal solute carrier family 26, member 6 (S1c26a6) and CFTR. However, the mechanisms governing ductal secretion are not known. Here, we have shown that pancreatic ductal secretion in mice is suppressed by silencing of the NBCe1-B/CFTR activator inositol-1,4,5-trisphosphate (IP3) receptor-binding protein released with IP3 (IRBIT) and by inhibition of protein phosphatase 1 (PP1). In contrast, silencing the with-no-lysine (WNK) kinases and Ste20-related proline/alanine-rich kinase (SPAK) increased secretion. Molecular analysis revealed that the WNK kinases acted as scaffolds to recruit SPAK, which phosphorylated CFTR and NBCe1-B, reducing their cell surface expression. IRBIT opposed the effects of WNKs and SPAK by recruiting PP1 to the complex to dephosphorylate CFTR and NBCe1-B, restoring their cell surface expression, in addition to stimulating their activities. Silencing of SPAK and IRBIT in the same ducts rescued ductal secretion due to silencing of IRBIT alone. These findings stress the pivotal role of IRBIT in epithelial fluid and HCO3- secretion and provide a molecular mechanism by which IRBIT coordinates these processes. They also have implications for WNK/SPAK kinase-regulated processes involved in systemic fluid homeostasis, hypertension, and cystic fibrosis.