TY - JOUR
T1 - IRBIT governs epithelial secretion in mice by antagonizing the WNK/SPAK kinase pathway
AU - Yang, Dongki
AU - Li, Qin
AU - So, Insuk
AU - Huang, Chou Long
AU - Ando, Hideaki
AU - Mizutani, Akihiro
AU - Seki, George
AU - Mikoshiba, Katsuhiko
AU - Thomas, Philip J.
AU - Muallem, Shmuel
PY - 2011/3/1
Y1 - 2011/3/1
N2 - 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 (Slc26a6) 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 HCO 3- 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.
AB - 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 (Slc26a6) 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 HCO 3- 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.
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U2 - 10.1172/JCI43475
DO - 10.1172/JCI43475
M3 - Article
C2 - 21317537
AN - SCOPUS:79952205039
SN - 0021-9738
VL - 121
SP - 956
EP - 965
JO - Journal of Clinical Investigation
JF - Journal of Clinical Investigation
IS - 3
ER -