Faculty Opinions recommendation of Protein phosphatase 2A associates with and regulates atypical PKC and the epithelial tight junction complex.

Evidence indicates that PP2A (protein phosphatase 2A) interacts with epithelial tight junctions and negatively regulates the integrity of the tight junction. In the present study, the role of PP2A in the hydrogen peroxide-induced disruption of the tight junction was examined in Caco-2 cell monolayers. Hydrogen peroxide-induced decrease in electrical resistance and increase in inulin permeability was associated with the dephosphorylation of occludin on threonine residues. The hydrogen peroxide-induced decrease in electrical resistance, increase in inulin permeability and redistribution of occludin and ZO (zonula occludens)-1 from the intercellular junctions were significantly attenuated by selective inhibitors of PP2A (okadaic acid and fostriecin) and by knockdown of PP2A-Cα (the catalytic subunit of PP2A). The PP2A-Cα protein and PP2A activity were co-immunoprecipitated with occludin, and this co-immunoprecipitation was rapidly increased by hydrogen peroxide. Hydrogen peroxideinduced increase in co-immunoprecipitation of PP2A-Cα with occludin was prevented by PP2, a Src kinase inhibitor. GST (glutathione transferase)-pull down assays using recombinant GST–Occludin-C (C-terminal tail of occludin) and the purified PP2A showed that PP2A binds to the C-terminal domain of occludin; Src-induced tyrosine phosphorylation of GST–Occludin-C enhanced this binding. The present study shows that hydrogen peroxide increases the association of PP2A with occludin by a Src kinase-dependent mechanism, and that PP2A activity is involved in hydrogen peroxide-induced disruption of tight junctions in Caco-2 cell monolayers.

Download Full-text

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

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00297.2006 ◽

2007 ◽

Vol 292 (1) ◽

pp. G124-G133 ◽

Cited By ~ 37

Author(s):

Sigrid A. Rajasekaran ◽

Sonali P. Barwe ◽

Jegan Gopal ◽

Sergey Ryazantsev ◽

Eveline E. Schneeberger ◽

...

Keyword(s):

Epithelial Cells ◽

Tight Junction ◽

Tight Junctions ◽

Protein Phosphatase ◽

Mammalian Cells ◽

Protein Phosphatase 2A ◽

Epithelial Cell Line ◽

Phosphatase 2A ◽

Apical Junctions ◽

Well Differentiated

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.

Download Full-text

Protein phosphatase 2A associates with and regulates atypical PKC and the epithelial tight junction complex

The Journal of Cell Biology ◽

10.1083/jcb.200206114 ◽

2002 ◽

Vol 158 (5) ◽

pp. 967-978 ◽

Cited By ~ 184

Author(s):

Viyada Nunbhakdi-Craig ◽

Thomas Machleidt ◽

Egon Ogris ◽

Dennis Bellotto ◽

Charles L. White ◽

...

Keyword(s):

Okadaic Acid ◽

Protein Phosphatase ◽

Paracellular Permeability ◽

Major Protein ◽

Calcium Dependent ◽

Atypical Pkc ◽

Phosphatase 2A ◽

Epithelial Tight Junction ◽

And Function ◽

Darby Canine Kidney

Tight junctions (TJs) play a crucial role in the establishment of cell polarity and regulation of paracellular permeability in epithelia. Here, we show that upon calcium-induced junction biogenesis in Madin-Darby canine kidney cells, ABαC, a major protein phosphatase (PP)2A holoenzyme, is recruited to the apical membrane where it interacts with the TJ complex. Enhanced PP2A activity induces dephosphorylation of the TJ proteins, ZO-1, occludin, and claudin-1, and is associated with increased paracellular permeability. Expression of PP2A catalytic subunit severely prevents TJ assembly. Conversely, inhibition of PP2A by okadaic acid promotes the phosphorylation and recruitment of ZO-1, occludin, and claudin-1 to the TJ during junctional biogenesis. PP2A negatively regulates TJ assembly without appreciably affecting the organization of F-actin and E-cadherin. Significantly, inhibition of atypical PKC (aPKC) blocks the calcium- and serum-independent membrane redistribution of TJ proteins induced by okadaic acid. Indeed, PP2A associates with and critically regulates the activity and distribution of aPKC during TJ formation. Thus, we provide the first evidence for calcium-dependent targeting of PP2A in epithelial cells, we identify PP2A as the first serine/threonine phosphatase associated with the multiprotein TJ complex, and we unveil a novel role for PP2A in the regulation of epithelial aPKC and TJ assembly and function.

Download Full-text