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

2007 ◽  
Vol 292 (1) ◽  
pp. G124-G133 ◽  
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.

scholarly journals Protein phosphatase 2A plays a role in hydrogen peroxide-induced disruption of tight junctions in Caco-2 cell monolayers

2009 ◽  
Vol 421 (1) ◽  
pp. 59-70 ◽  
Author(s):  
Parimal Sheth ◽  
Geetha Samak ◽  
J. Andrew Shull ◽  
Ankur Seth ◽  
Radhakrishna Rao
Keyword(s):  
Hydrogen Peroxide ◽  
Tight Junction ◽  
Tight Junctions ◽  
Protein Phosphatase ◽  
Electrical Resistance ◽  
Protein Phosphatase 2A ◽  
Src Kinase ◽  
Cell Monolayers ◽  
Pp2a Activity ◽  
Phosphatase 2A

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.

scholarly journals PR48, a Novel Regulatory Subunit of Protein Phosphatase 2A, Interacts with Cdc6 and Modulates DNA Replication in Human Cells

2000 ◽  
Vol 20 (3) ◽  
pp. 1021-1029 ◽  
Author(s):  
Zhen Yan ◽  
Sergei A. Fedorov ◽  
Marc C. Mumby ◽  
R. Sanders Williams
Keyword(s):  
Dna Replication ◽  
Protein Phosphatase ◽  
Mammalian Cells ◽  
Cell Cycle Progression ◽  
Protein Phosphatase 2A ◽  
Specific Interaction ◽  
Regulatory Subunit ◽  
Amino Terminal ◽  
Phosphatase 2A ◽  
Initiation Of Dna Replication

ABSTRACT Initiation of DNA replication in eukaryotes is dependent on the activity of protein phosphatase 2A (PP2A), but specific phosphoprotein substrates pertinent to this requirement have not been identified. A novel regulatory subunit of PP2A, termed PR48, was identified by a yeast two-hybrid screen of a human placental cDNA library, using human Cdc6, an essential component of prereplicative complexes, as bait. PR48 binds specifically to an amino-terminal segment of Cdc6 and forms functional holoenzyme complexes with A and C subunits of PP2A. PR48 localizes to the nucleus of mammalian cells, and its forced overexpression perturbs cell cycle progression, causing a G1 arrest. These results suggest that dephosphorylation of Cdc6 by PP2A, mediated by a specific interaction with PR48, is a regulatory event controlling initiation of DNA replication in mammalian cells.

Antitumor antibiotic fostriecin covalently binds to cysteine-269 residue of protein phosphatase 2A catalytic subunit in mammalian cells

2009 ◽  
Vol 17 (23) ◽  
pp. 8113-8122 ◽  
Author(s):  
Toshifumi Takeuchi ◽  
Noriyuki Takahashi ◽  
Kazutomo Ishi ◽  
Tomoe Kusayanagi ◽  
Kouji Kuramochi ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Mammalian Cells ◽  
Protein Phosphatase 2A ◽  
Catalytic Subunit ◽  
Antitumor Antibiotic ◽  
Phosphatase 2A

scholarly journals Activating protein phosphatase 2A (PP2A) enhances tristetraprolin (TTP) anti-inflammatory function in A549 lung epithelial cells

2016 ◽  
Vol 28 (4) ◽  
pp. 325-334 ◽  
Author(s):  
Md. Mostafizur Rahman ◽  
Nowshin N. Rumzhum ◽  
Philip M. Hansbro ◽  
Jonathan C. Morris ◽  
Andrew R. Clark ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Lung Epithelial Cells ◽  
Lung Epithelial ◽  
Phosphatase 2A ◽  
Anti Inflammatory ◽  
A549 Lung

scholarly journals Protein Phosphatase 2A Mediates Oxidative Stress Induced Apoptosis in Osteoblasts

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Chong-xin Huang ◽  
Bo Lv ◽  
Yue Wang
Keyword(s):  
Oxidative Stress ◽  
Lipid Peroxidation ◽  
Protein Phosphatase ◽  
Mammalian Cells ◽  
Protein Phosphatase 2A ◽  
Bone Diseases ◽  
Dna Lesions ◽  
Major Protein ◽  
Phosphatase 2A ◽  
Induced Apoptosis

Osteoporosis is one of the most common bone diseases, which is characterized by a systemic impairment of bone mass and fragility fractures. Age-related oxidative stress is highly associated with impaired osteoblastic dysfunctions and subsequent osteoporosis. In osteoblasts (bone formation cells), reactive oxygen species (ROS) are continuously generated and further cause lipid peroxidation, protein damage, and DNA lesions, leading to osteoblastic dysfunctions, dysdifferentiations, and apoptosis. Although much progress has been made, the mechanism responsible for oxidative stress induced cellular alternations and osteoblastic toxicity is still not fully elucidated. Here, we demonstrate that protein phosphatase 2A (PP2A), a major protein phosphatase in mammalian cells, mediates oxidative stress induced apoptosis in osteoblasts. Our results showed that lipid peroxidation products (4-HNE) may induce dramatic oxidative stress, inflammatory reactions, and apoptosis in osteoblasts. These oxidative stress responses may ectopically activate PP2A phosphatase activity, which may be mediated by inactivation of AKT/mTOR pathway. Moreover, inhibition of PP2A activity by okadaic acid might partly prevent osteoblastic apoptosis under oxidative conditions. These findings may reveal a novel mechanism to clarify the role of oxidative stress for osteoblastic apoptosis and provide new possibilities for the treatment of related bone diseases, such as osteoporosis.

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