IRBIT governs epithelial secretion in mice by antagonizing the WNK/SPAK kinase pathway

Dongki Yang, Qin Li, Insuk So, Chou Long Huang, Hideaki Ando, Akihiro Mizutani, George Seki, Katsuhiko Mikoshiba, Philip J. Thomas, Shmuel Muallem

Research output: Contribution to journalArticlepeer-review

78 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)956-965
Number of pages10
JournalJournal of Clinical Investigation
Issue number3
StatePublished - Mar 1 2011

ASJC Scopus subject areas

  • Medicine(all)


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