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.

Protein phosphatase 2A-mediated cross-talk between p38 MAPK and ERK in apoptosis of cardiac myocytes

2004 ◽  
Vol 286 (6) ◽  
pp. H2204-H2212 ◽  
Author(s):  
Qinghang Liu ◽  
Polly A. Hofmann
Keyword(s):  
Oxidative Stress ◽  
P38 Mapk ◽  
Cross Talk ◽  
Protein Phosphatase ◽  
Ventricular Myocytes ◽  
Protein Phosphatase 2A ◽  
Erk Phosphorylation ◽  
Phosphatase 2A ◽  
Induced Apoptosis ◽  
Cardiac Ventricular Myocytes

Mitogen-activated protein kinases (MAPKs) play different regulatory roles in signaling oxidative stress-induced apoptosis in cardiac ventricular myocytes. The regulation and functional role of cross-talk between p38 MAPK and extracellular signal-regulated kinase (ERK) pathways were investigated in cardiac ventricular myocytes in the present study. We demonstrated that inhibition of p38 MAPK with SB-203580 and SB-239063 enhanced H2O2-stimulated ERK phosphorylation, whereas preactivation of p38 MAPK with sodium arsenite reduced H2O2-stimulated ERK phosphorylation. In addition, pretreatment of cells with the protein phosphatase 2A (PP2A) inhibitors okadaic acid and fostriecin increased basal and H2O2-stimulated ERK phosphorylation. We also found that PP2A coimmunoprecipitated with ERK and MAPK/ERK (MEK) in cardiac ventricular myocytes, and H2O2increased the ERK-associated PP2A activity that was blocked by inhibition of p38 MAPK. Finally, H2O2-induced apoptosis was attenuated by p38 MAPK or PP2A inhibition, whereas it was enhanced by MEK inhibition. Thus the present study demonstrated that p38 MAPK activation decreases H2O2-induced ERK activation through a PP2A-dependent mechanism in cardiac ventricular myocytes. This represents a novel cellular mechanism that allows for interaction of two opposing MAPK pathways and fine modulation of apoptosis during oxidative stress.

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 Oxidative Stress Induces Protein Phosphatase 2A-dependent Dephosphorylation of the Pocket Proteins pRb, p107, and p130

2003 ◽  
Vol 278 (21) ◽  
pp. 19509-19517 ◽  
Author(s):  
Lucia Cicchillitti ◽  
Pasquale Fasanaro ◽  
Paolo Biglioli ◽  
Maurizio C. Capogrossi ◽  
Fabio Martelli
Keyword(s):  
Oxidative Stress ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Pocket Proteins ◽  
Phosphatase 2A

scholarly journals Inactivation of the protein phosphatase 2A regulatory subunit A results in morphological and transcriptional defects in Saccharomyces cerevisiae

1992 ◽  
Vol 12 (11) ◽  
pp. 4946-4959
Author(s):  
W van Zyl ◽  
W Huang ◽  
A A Sneddon ◽  
M Stark ◽  
S Camier ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Rna Polymerase ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Rna Polymerase Iii ◽  
Regulatory Subunit ◽  
Predicted Amino Acid Sequence ◽  
Major Protein ◽  
Polymerase Iii ◽  
Phosphatase 2A

We have determined that TPD3, a gene previously identified in a screen for mutants defective in tRNA biosynthesis, most likely encodes the A regulatory subunit of the major protein phosphatase 2A species in the yeast Saccharomyces cerevisiae. The predicted amino acid sequence of the product of TPD3 is highly homologous to the sequence of the mammalian A subunit of protein phosphatase 2A. In addition, antibodies raised against Tpd3p specifically precipitate a significant fraction of the protein phosphatase 2A activity in the cell, and extracts of tpd3 strains yield a different chromatographic profile of protein phosphatase 2A than do extracts of isogenic TPD3 strains. tpd3 deletion strains generally grow poorly and have at least two distinct phenotypes. At reduced temperatures, tpd3 strains appear to be defective in cytokinesis, since most cells become multibudded and multinucleate following a shift to 13 degrees C. This is similar to the phenotype obtained by overexpression of the protein phosphatase 2A catalytic subunit or by loss of CDC55, a gene that encodes a protein with homology to a second regulatory subunit of protein phosphatase 2A. At elevated temperatures, tpd3 strains are defective in transcription by RNA polymerase III. Consistent with this in vivo phenotype, extracts of tpd3 strains fail to support in vitro transcription of tRNA genes, a defect that can be reversed by addition of either purified RNA polymerase III or TFIIIB. These results reinforce the notion that protein phosphatase 2A affects a variety of biological processes in the cell and provide an initial identification of critical substrates for this phosphatase.

scholarly journals Inactivation of the protein phosphatase 2A regulatory subunit A results in morphological and transcriptional defects in Saccharomyces cerevisiae.

1992 ◽  
Vol 12 (11) ◽  
pp. 4946-4959 ◽  
Author(s):  
W van Zyl ◽  
W Huang ◽  
A A Sneddon ◽  
M Stark ◽  
S Camier ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Rna Polymerase ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Rna Polymerase Iii ◽  
Regulatory Subunit ◽  
Predicted Amino Acid Sequence ◽  
Major Protein ◽  
Polymerase Iii ◽  
Phosphatase 2A

We have determined that TPD3, a gene previously identified in a screen for mutants defective in tRNA biosynthesis, most likely encodes the A regulatory subunit of the major protein phosphatase 2A species in the yeast Saccharomyces cerevisiae. The predicted amino acid sequence of the product of TPD3 is highly homologous to the sequence of the mammalian A subunit of protein phosphatase 2A. In addition, antibodies raised against Tpd3p specifically precipitate a significant fraction of the protein phosphatase 2A activity in the cell, and extracts of tpd3 strains yield a different chromatographic profile of protein phosphatase 2A than do extracts of isogenic TPD3 strains. tpd3 deletion strains generally grow poorly and have at least two distinct phenotypes. At reduced temperatures, tpd3 strains appear to be defective in cytokinesis, since most cells become multibudded and multinucleate following a shift to 13 degrees C. This is similar to the phenotype obtained by overexpression of the protein phosphatase 2A catalytic subunit or by loss of CDC55, a gene that encodes a protein with homology to a second regulatory subunit of protein phosphatase 2A. At elevated temperatures, tpd3 strains are defective in transcription by RNA polymerase III. Consistent with this in vivo phenotype, extracts of tpd3 strains fail to support in vitro transcription of tRNA genes, a defect that can be reversed by addition of either purified RNA polymerase III or TFIIIB. These results reinforce the notion that protein phosphatase 2A affects a variety of biological processes in the cell and provide an initial identification of critical substrates for this phosphatase.

scholarly journals Cancerous inhibitor of protein phosphatase 2A determines bortezomib-induced apoptosis in leukemia cells

Haematologica ◽  
2012 ◽  
Vol 98 (5) ◽  
pp. 729-738 ◽  
Author(s):  
C.-Y. Liu ◽  
C.-W. Shiau ◽  
H.-Y. Kuo ◽  
H.-P. Huang ◽  
M.-H. Chen ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Leukemia Cells ◽  
Phosphatase 2A ◽  
Induced Apoptosis
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