scholarly journals Protein phosphatase 2A regulatory subunit B56α limits phosphatase activity in the heart

2015 ◽  
Vol 8 (386) ◽  
pp. ra72-ra72 ◽  
Author(s):  
Sean C. Little ◽  
Jerry Curran ◽  
Michael A. Makara ◽  
Crystal F. Kline ◽  
Hsiang-Ting Ho ◽  
...  
Keyword(s):  
Phosphatase Activity ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Regulatory Subunit ◽  
Phosphatase 2A

scholarly journals Loss of a Protein Phosphatase 2A Regulatory Subunit (Cdc55p) Elicits Improper Regulation of Swe1p Degradation

2000 ◽  
Vol 20 (21) ◽  
pp. 8143-8156 ◽  
Author(s):  
Haifeng Yang ◽  
Wei Jiang ◽  
Matthew Gentry ◽  
Richard L. Hallberg
Keyword(s):  
Phosphatase Activity ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Cell Types ◽  
Regulatory Subunit ◽  
Cyclin Dependent Kinase ◽  
Wild Type ◽  
Phosphatase 2A

ABSTRACT CDC55 encodes a Saccharomyces cerevisiaeprotein phosphatase 2A (PP2A) regulatory subunit.cdc55-null cells growing at low temperature exhibit a failure of cytokinesis and produce abnormally elongated buds, butcdc55-null cells producing the cyclin-dependent kinase Cdc28-Y19F, which is unable to be inhibited by Y19 phosphorylation, show a loss of the abnormal morphology. Furthermore,cdc55-null cells exhibit a hyperphosphorylation of Y19. For these reasons, we have examined in wild-type and cdc55-null cells the levels and activities of the kinase (Swe1p) and phosphatase (Mih1p) that normally regulate the extent of Cdc28 Y19 phosphorylation. We find that Mih1p levels are comparable in the two strains, and an estimate of the in vivo and in vitro phosphatase activity of this enzyme in the two cell types indicates no marked differences. By contrast, while Swe1p levels are similar in unsynchronized and S-phase-arrested wild-type and cdc55-null cells, Swe1 kinase is found at elevated levels in mitosis-arrestedcdc55-null cells. This excess Swe1p incdc55-null cells is the result of ectopic stabilization of this protein during G2 and M, thereby accounting for the accumulation of Swe1p in mitosis-arrested cells. We also present evidence indicating that, in cdc55-null cells, misregulated PP2A phosphatase activity is the cause of both the ectopic stabilization of Swe1p and the production of the morphologically abnormal phenotype.

scholarly journals Drosophila mutants in the 55 kDa regulatory subunit of protein phosphatase 2A show strongly reduced ability to dephosphorylate substrates of p34cdc2

1994 ◽  
Vol 107 (9) ◽  
pp. 2609-2616 ◽  
Author(s):  
R.E. Mayer-Jaekel ◽  
H. Ohkura ◽  
P. Ferrigno ◽  
N. Andjelkovic ◽  
K. Shiomi ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Phosphatase Activity ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Regulatory Subunit ◽  
Gene Encoding ◽  
Brain Extracts ◽  
Drosophila Protein ◽  
Phosphatase 2A ◽  
Drosophila Mutants

The 55 kDa regulatory subunit of Drosophila protein phosphatase 2A is located in the cytoplasm at all cell cycle stages, by the criterion of immunofluorescence. We are unable to detect significant change in protein phosphatase activity during the nuclear division cycle of syncytial embryos. However, cell cycle function of the enzyme is suggested by the mitotic defects exhibited by two Drosophila mutants, aar1 and twinsP, defective in the gene encoding the 55 kDa subunit. The reduced levels of the 55 kDa subunit correlate with the loss of protein phosphatase 2A-like, okadaic acid-sensitive phosphatase activity of brain extracts against caldesmon and histone H1 phosphorylated by p34cdc2/cyclin B kinase, but not against phosphorylase a. Thus the mitotic defects of aar1 and twinsP are likely to result from the lack of dephosphorylation of specific substrates by protein phosphatase 2A.

scholarly journals Molecular cloning, expression, and characterization of PTPA, a protein that activates the tyrosyl phosphatase activity of protein phosphatase 2A.

1994 ◽  
Vol 269 (22) ◽  
pp. 15668-15675 ◽  
Author(s):  
X. Cayla ◽  
C. Van Hoof ◽  
M. Bosch ◽  
E. Waelkens ◽  
J. Vandekerckhove ◽  
...  
Keyword(s):  
Molecular Cloning ◽  
Phosphatase Activity ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Phosphatase 2A

scholarly journals Structure and expression of a 72-kDa regulatory subunit of protein phosphatase 2A. Evidence for different size forms produced by alternative splicing

1993 ◽  
Vol 268 (20) ◽  
pp. 15267-15276
Author(s):  
P. Hendrix ◽  
R.E. Mayer-Jackel ◽  
P. Cron ◽  
J. Goris ◽  
J. Hofsteenge ◽  
...  
Keyword(s):  
Alternative Splicing ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Regulatory Subunit ◽  
Phosphatase 2A

scholarly journals Regulatory Subunit B′γ of Protein Phosphatase 2A Prevents Unnecessary Defense Reactions under Low Light in Arabidopsis

2011 ◽  
Vol 156 (3) ◽  
pp. 1464-1480 ◽  
Author(s):  
Andrea Trotta ◽  
Michael Wrzaczek ◽  
Judith Scharte ◽  
Mikko Tikkanen ◽  
Grzegorz Konert ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Regulatory Subunit ◽  
Low Light ◽  
Defense Reactions ◽  
Phosphatase 2A ◽  
Subunit B

scholarly journals Protein Phosphatase 2A Regulatory Subunit B56α Associates with c-Myc and Negatively Regulates c-Myc Accumulation

2006 ◽  
Vol 26 (7) ◽  
pp. 2832-2844 ◽  
Author(s):  
Hugh K. Arnold ◽  
Rosalie C. Sears
Keyword(s):  
Tumor Suppressor ◽  
Protein Phosphatase ◽  
Cell Function ◽  
Cell Transformation ◽  
Protein Phosphatase 2A ◽  
Regulatory Subunit ◽  
Suppressor Activity ◽  
Tumor Suppressor Activity ◽  
Structural Subunit ◽  
Phosphatase 2A

ABSTRACT Protein phosphatase 2A (PP2A) plays a prominent role in controlling accumulation of the proto-oncoprotein c-Myc. PP2A mediates its effects on c-Myc by dephosphorylating a conserved residue that normally stabilizes c-Myc, and in this way, PP2A enhances c-Myc ubiquitin-mediated degradation. Stringent regulation of c-Myc levels is essential for normal cell function, as c-Myc overexpression can lead to cell transformation. Conversely, PP2A has tumor suppressor activity. Uncovering relevant PP2A holoenzymes for a particular target has been limited by the fact that cellular PP2A represents a large heterogeneous population of trimeric holoenzymes, composed of a conserved catalytic subunit and a structural subunit along with a variable regulatory subunit which directs the holoenzyme to a specific target. We now report the identification of a specific PP2A regulatory subunit, B56α, that selectively associates with the N terminus of c-Myc. B56α directs intact PP2A holoenzymes to c-Myc, resulting in a dramatic reduction in c-Myc levels. Inhibition of PP2A-B56α holoenzymes, using small hairpin RNA to knock down B56α, results in c-Myc overexpression, elevated levels of c-Myc serine 62 phosphorylation, and increased c-Myc function. These results uncover a new protein involved in regulating c-Myc expression and reveal a critical interconnection between a potent oncoprotein, c-Myc, and a well-documented tumor suppressor, PP2A.

scholarly journals A Novel Interaction of the Catalytic Subunit of Protein Phosphatase 2A with the Adaptor Protein CIN85 Suppresses Phosphatase Activity and Facilitates Platelet Outside-in αIIbβ3 Integrin Signaling

2016 ◽  
Vol 291 (33) ◽  
pp. 17360-17368 ◽  
Author(s):  
Tanvir Khatlani ◽  
Subhashree Pradhan ◽  
Qi Da ◽  
Tanner Shaw ◽  
Vladimir L. Buchman ◽  
...  
Keyword(s):  
Phosphatase Activity ◽  
Protein Interactions ◽  
Protein Phosphatase ◽  
Thrombus Formation ◽  
Protein Phosphatase 2A ◽  
Adaptor Protein ◽  
Fibrin Clot ◽  
Catalytic Subunit ◽  
Clot Retraction ◽  
Phosphatase 2A

The transduction of signals generated by protein kinases and phosphatases are critical for the ability of integrin αIIbβ3 to support stable platelet adhesion and thrombus formation. Unlike kinases, it remains unclear how serine/threonine phosphatases engage the signaling networks that are initiated following integrin ligation. Because protein-protein interactions form the backbone of signal transduction, we searched for proteins that interact with the catalytic subunit of protein phosphatase 2A (PP2Ac). In a yeast two-hybrid study, we identified a novel interaction between PP2Ac and an adaptor protein CIN85 (Cbl-interacting protein of 85 kDa). Truncation and alanine mutagenesis studies revealed that PP2Ac binds to the P3 block (396PAIPPKKPRP405) of the proline-rich region in CIN85. The interaction of purified PP2Ac with CIN85 suppressed phosphatase activity. Human embryonal kidney 293 αIIbβ3 cells overexpressing a CIN85 P3 mutant, which cannot support PP2Ac binding, displayed decreased adhesion to immobilized fibrinogen. Platelets contain the ∼85 kDa CIN85 protein along with the PP2Ac-CIN85 complex. A myristylated cell-permeable peptide derived from residues 395–407 of CIN85 protein (P3 peptide) disrupted the platelet PP2Ac-CIN85 complex and decreased αIIbβ3 signaling dependent functions such as platelet spreading on fibrinogen and thrombin-mediated fibrin clot retraction. In a phospho-profiling study P3 peptide treated platelets also displayed decreased phosphorylation of several signaling proteins including Src and GSK3β. Taken together, these data support a role for the novel PP2Ac-CIN85 complex in supporting integrin-dependent platelet function by dampening the phosphatase activity.

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