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Am J Physiol Gastrointest Liver Physiol 292: G124-G133, 2007. First published September 7, 2006; doi:10.1152/ajpgi.00297.2006
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MUCOSAL BIOLOGY

Na-K-ATPase regulates tight junction permeability through occludin phosphorylation in pancreatic epithelial cells

¹Department of Pathology and Laboratory Medicine, ²Department of Biological Chemistry, ³Molecular Biology Institute, ⁴Jonsson Comprehensive Cancer Center, David Geffen School of Medicine, University of California, Los Angeles, California; and ⁵Molecular Pathology Unit, Massachusetts General Hospital East, Charlestown, Massachusetts

Submitted 6 July 2006 ; accepted in final form 28 August 2006

Tight junctions are crucial for maintaining the polarity and vectorial transport functions of epithelial cells. We and others have shown that Na-K-ATPase plays a key role in the organization and permeability of tight junctions in mammalian cells and analogous septate junctions in Drosophila. However, the mechanism by which Na-K-ATPase modulates tight junctions is not known. In this study, using a well-differentiated human pancreatic epithelial cell line HPAF-II, we demonstrate that Na-K-ATPase is present at the apical junctions and forms a complex with protein phosphatase-2A, a protein known to be present at tight junctions. Inhibition of Na-K-ATPase ion transport function reduced protein phosphatase-2A activity, hyperphosphorylated occludin, induced rearrangement of tight junction strands, and increased permeability of tight junctions to ionic and nonionic solutes. These data suggest that Na-K-ATPase is required for controlling the tight junction gate function.

Na-K-ATPase ₁-subunit; Na-K-ATPase ₁-subunit; protein phosphatase-2A; pancreas

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