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1

Protein phosphatase 2A: Variety of forms and diversity of functions

100%

Lechward K., Awotunde O. S., Swiatek W., Muszynska G.

Acta Biochimica Polonica

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2001

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tom 48

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nr 4

Protein phosphatase 2A (PP2A) comprises a diverse family of phosphoserine- and phosphothreonine-specific phosphatases present in all eukaryotic cells. All forms of PP2A contain a catalytic subunit (PP2Ac) which forms a stable complex with thestructural subunit PR65/A. The heterodimer PP2Ac-PR65/A associates with regulatory proteins, termed variable subunits, in order to form trimeric holoenzymes attributed with distinct substrate specificity and targeted to different subcellular compartments. PP2Ac activity can be modulated by reversible phosphorylation on Tyr307 and methylation on C-terminal Leu309. Studies on PP2A have shown that this enzyme may be implicated in the regulation of metabolism, transcription, RNA splicing, translation, differentiation, cell cycle, oncogenic transformation and signal transduction.

2

Rat brain Ca2plus - ATPase is a substrate for protein phosphatases PP1 and PP2A

100%

Zylinska L., Gromadzinska E., Lachowicz L.

Cellular and Molecular Biology Letters

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1999

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tom 04

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nr 4

A possible role of serine/threonine protein phosphatases PP1 and PP2A in the regulation in vitro of the plasma membrane Ca2+-ATPase purified from rat cortical and cerebellar synaptosomal membranes was investigated. Calcium pump, the enzyme responsible for the maintenance of intracellular calcium homeostasis, is regulated by several mechanisms, including phosphorylation by protein kinases. Here we demonstrate that the protein phosphatases action decreased the activity of native Ca2+-ATPase, and increased the stimulatory effect of calmodulin. Moreover, the calcium pump dephosphorylated by PP1 and PP2A revealed the presence of the additional sites, accessible for a PKA-mediated phosphorylation. The subsequent PKA or PKC phosphorylation of the dephosphorylated cortical and cerebellar Ca2+-ATPase differentially regulated its hydrolytic activity. This study confirms that Ca2+-ATPase in nervous cell is phosphorylated in vivo, and shows for the first time that its activity may be directly regulated by PP1 and PP2A.

3

Theoretical models of catalytic domains of protein phosphatases 1 and 2A with Zn2plus and Mn2plus metal dications and putative bioligands in their catalytic centers

100%

Wozniak-Celmer E., Oldziej S., Ciarkowski J.

Acta Biochimica Polonica

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2001

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tom 48

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nr 1

The oligomeric metalloenzymes protein phosphatases dephosphorylate OH groups of Ser/Thr or Tyr residues of proteins whose actions depend on the phosphorus signal. The catalytic units of Ser/Thr protein phosphatases 1, 2A and 2B (PP1c, PP2Ac and PP2Bc, respectively), which exhibit about 45% sequence similarity, have their active centers practically identical. This feature strongly suggests that the unknown structure of PP2Ac could be successfully homology-modeled from the known structures of PP1c and/or PP2Bc. Initially, a theoretical model of PP1c was built, including a phosphate and a metal dication in its catalytic site. The latter was modeled, together with a structural hydroxyl anion, as a triangular pseudo-molecule (Zno or Mno), composed of two metal cations (dou ble Zn2+ or Mn2+ , respectively) and the OH- group. To the free PP1c two inhibitor sequences R29RRRPpTPAMLFR40 of DARPP-32 and R30RRRPpTPATLVLT42 of Inhibitor-1, and two putative substrate sequences LRRApSVA and QRRQRKpRRTI were subsequently docked. In the next step, a free PP2Ac model was built via homology re-modeling of the PP1c template and the same four sequences were docked to it. Thus, together, 20 starting model complexes were built, allowing for combination of the Zno and Mno pseudo-molecules, free enzymes and the peptide ligands docked in the catalytic sites of PP1c and PP2Ac. All models were subsequently subjected to 250-300 ps molecular dynamics using the AMBER 5.0 program. The equilibrated trajectories of the final 50 ps were taken for further analyses. The theoretical models of PP1c complexes, irrespective of the dication type, exhibited increased mobilities in the following residue ranges: 195-200, 273-278, 287-209 for the inhibitor sequences and 21-25, 194-200, 222-227, 261, 299–302 for the substrate sequences. Paradoxically, the analogous PP2Ac models appeared much more stable in similar simulations, since only their “prosegment” residues 6–10 and 14–18 exhibited an increased mobility in the inhibitor complexes while no areas of increased mobility were found in the substrate complexes. Another general observation was that the complexes with Mn dications were more stable than those with Zn dications for both PP1c and PP2Ac units.

4

Positive and negative regulatory mechanisms in high-affinity IgE receptor-mediated mast cell activation

84%

Roth K., Chen W.-M., Lin T.-J.

Archivum Immunologiae et Therapiae Experimentalis

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2008

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tom 56

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nr 6

385-399

5

Effect of OA-inhibitor of protein phosphatases PP1 and PP2A - on initiation of DNA replication and mitosis in Vicia faba root meristems

84%

Polit J., Maszewski J.

Acta Physiologiae Plantarum

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2005

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tom 27

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nr 3A

According to the principal control point (PCP) hypothesis, experiments with excised, carbohydrate-starved stationary root meristems of Vicia faba var. minor have demonstrated that cells which previously divided asynchronously were preferentially blocked in G1 (PCP1) and G2 (PCP2) phases. When stationary phase meristems are supplied with exogenous carbohydrate (2 % sucrose), the G1- and G2-arrested cells start out DNA replication and mitotic divisions, respectively. The resumption of DNA synthesis and mitosis is not immediate and the delays of Gi - and G2-arrested cells are found different. Using this model, we examined the effects of 4 pulse incubations with okadaic acid (OA), a specific inhibitor of PP1 and PP2A, on the duration of intervals elapsing between the provision of sucrose and the first appearance of S- and M-phase cells. We have found that depending on the period during which OA had been applied, the release from G1 and G2 phase arrest-points becomes prolonged, showing different time-course modifications The obtained data provide evidence that activation of PP1 and PP2A is required to allow the cells for both PCP1→S and PCP2→M transitions in root meristems of V. faba.

6

The opposite effects of cyclic AMP-protein kinase a signal transduction pathway on renal cortical and medullary Naplus, Kplus-ATPase activity

84%

Beltowski J., Marciniak A., Wojcicka G., Gorny D.

Journal of Physiology and Pharmacology

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2002

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tom 53

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nr 2

Cyclic AMP-protein kinase A (PKA) pathway plays an important role in signal transduction in renal tubular cells, however, its role in transport regulation is not completely established. The aim of this study was to investigate in vivo the effect of PKA on renal Na+, K+-ATPase activity. The study was performed in male Wistar rats. The animals were anaesthetized with pentobarbital and investigated drugs were infused through the catheter inserted into the abdominal aorta. Na+,K+-ATPase activity was assayed in an isolated microsomal fraction of the renal cortex and medulla. Cell-permeable cAMP analogue, dibutyryl-cAMP (db-cAMP), dose-dependently stimulated Na+,K+-ATPase in the renal cortex and inhibited in the renal medulla. Maximal stimulation (+38.5%) and inhibition (-46.8%) were observed at a dose of 10-6 mol/kg/min. Measurement of Na+,K+-ATPase activity at different Na+ concentrations revealed that in the renal cortex db-cAMP increased Vmax of the enzyme without any effect on sodium affinity, whereas in the renal medulla decrease in Vmax was accompanied by decreased sodium affinity, evidenced by elevated K0.5 for sodium. The effect of db-cAMP was mimicked by the infusion of either adenylate cyclase activator, forskolin, or inhibitor of phosphodiesterase, IBMX. Both stimulatory and inhibitory effects of db-cAMP were prevented by pretreatment with protein kinase A inhibitor, KT 5720 (10-8 mol/kg/min) but not by inhibitor of protein kinase G, KT 5823. The inhibitory effect in the renal medulla was partially blocked by pretreatment with either ethoxyresorufin or 17-ODYA – two nonspecific inhibitors of cytochrome P450-dependent arachidonate metabolism, whereas an inhibitor of epoxygenase, miconazole, was not effective. Infusion of 20-hydroxyeicosatetraenoic acid (20-HETE) at a dose of 10-10 mol/kg/min decreased medullary Na+,K+-ATPase activity by 24.2%. Exogenous protein phosphatases inhibitor, okadaic acid (OA, 10-8-10-7 mol/kg/min) caused dose-dependent decrease in renal medullary Na+,K+-ATPase activity, maximally by 31.9%, but had no effect in the renal cortex. The effects of OA and db-cAMP in the renal medulla were not additive. When OA administration (10-7 mol/kg/min) was followed by 20-HETE (10-10 mol/kg/min), medullary Na+,K+-ATPase activity decreased by 48.6% and was similar as after db-cAMP. We conclude, that cAMP-PKA pathway activates Na+,K+-ATPase in the renal cortex and inhibits in the renal medulla. The inhibitory effect is partially mediated by cytochrome P450-dependent arachidonate metabolites and possibly also by PKA-dependent inhibition of protein phosphatases.

7

The 35 kDa acid metallophosphatase of the frog Rana esculenta liver: studies on its cellular localization and protein phosphatase activity

84%

Szalewicz A., Strzelczyk B., Sopel M., Kubicz A.

Acta Biochimica Polonica

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2003

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tom 50

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nr 2

The cellular localization of the 35 kDa, low molecular mass acid metallophosphatase (LMW AcPase) from the frog (Rana esculenta) liver and its activity towards P-Ser and P-Tyr phosphorylated peptides were studied. This enzyme was localized to the cytoplasm of hepatocytes but did not appear in other cells of liver tissue (endothelium, macrophages, blood cells). This LMW AcPase does not display activity towards 32P-phosphorylase a under conditions standard for the enzymes of PPP family. Proteins containing P-Ser: rabbit 32P-phosphorylase a and phosvitin are hydrolysed only at acidic pH and are poor substrates for this enzyme. The frog AcPase is not inhibited by okadaic acid and F- ions, the Ser/Thr protein phosphatase inhibitors. Moreover, the frog enzyme does not cross-react with specific antisera directed against N-terminal fragment of human PP2A and C-terminal conserved fragment of the eukaryotic PP2A catalytic subunits. These results exclude LMW AcPase from belonging to Ser/Thr protein phosphatases: PP1c or PP2Ac. In addition to P-Tyr, this enzyme hydrolyses efficiently at acidic pH P-Tyr phosphorylated peptides (hirudin and gastrin fragments). Km value for the hirudin fragment (7.55 ± 1.59 10–6M) is 2–3 orders of magnitude lower in comparison with other substrates tested. The enzyme is inhibited competitively by typical inhibitors of protein tyrosine phosphatases (PTPases): sodium orthovanadate, molybdate and tungstate. These results may suggest that the LMW AcPase of frog liver can act as PTPase in vivo. A different cellular localization and different response to inhibition by tetrahedral oxyanions (molybdate, vanadate and tungstate) provide further evidence that LMW AcPase of frog liver is distinct from the mammalian tartrate-resistant acid phosphatases.

8

De novo synthesis of protein phosphatase 1A, magnesium dependent, alpha isoform (PPM1A) during oocyte maturation

67%

Chuderland D., Dvashi Z., Kaplan-Kraicer R., Ben-Meir D., Shalgi R., Lavi S.

Cellular and Molecular Biology Letters

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2012

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tom 17

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nr 3

Oocyte maturation in mammals is a multiple-stage process that generates fertilizable oocytes. Ovarian oocytes are arrested at prophase of the first meiotic division characterized by the presence of a germinal vesicle. Towards ovulation, the oocytes resume meiosis and proceed to the second metaphase in a process known as maturation; they undergo nuclear and cytoplasmic changes that are accompanied by translation and degradation of mRNA. Protein phosphatase 1A, magnesium dependent, alpha isoform (PPM1A), which belongs to the metal-dependent serine/threonine protein phosphatase family, is highly conserved during evolution. PPM1A plays a significant role in many cellular functions such as cell cycle progression, apoptosis and cellular differentiation. It works through diverse signaling pathways, including p38 MAP kinase JNK and transforming growth factor beta (TGF-β). Herein we report that PPM1A is expressed in mouse oocytes and that its mRNA level rises during oocyte maturation. Using quantitative real-time polymerase chain reaction (qPCR) and western blot analysis, we found that PPM1A mRNA is synthesized at the beginning of the maturation process and remains elevated in the mature oocytes, promoting the accumulation of PPM1A protein. Since PPM1A function is mainly affected by its level, we propose that it might have an important role in oocyte maturation.

9

Lokalizacja fosfataz bialkowych w subfrakcjach jader komorkowych watroby prawidlowej i watrobiaka Kirkmana-Robbins chomika

67%

Rozalski M., Krajewska U.

Bromatologia i Chemia Toksykologiczna

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1995

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tom 28

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nr 1

87-92

Badano aktywność fosfataz białkowych wobec dwu substratów i w obecności specyficznych inhibitorów w różnych przedziałach jąder komórkowych wątroby i wątrobiaka Kirkmana-Robbins w celu zaklasyfikowania zlokalizowanych tam enzymów.

10

The decrease in JNK- and p38-MAP kinase activity is accompanied by the enhancement of PP2A phosphatase level in the brain of prenatally stressed rats

67%

Budziszewska B., Szymanska M., Leskiewicz M., Basta-Kaim A., Jaworska-Feil L., Kubera M., Jantas D., Lason W.

Journal of Physiology and Pharmacology

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2010

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tom 61

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nr 2

Our previous study suggests that in prenatal stress model of depression glucocorticoid receptor (GR) function in adult rats is enhanced. However, the long-term consequences of stress, a causal factor in depression, on intracellular elements involved into the regulation of GR function is poorly examined. Mitogen-activated protein kinases (MAPKs), activity of which is disturbed in depression, are important regulators of GR action, so they can mediate the effect of stress on GR function. Therefore, the aim of the present study was to investigate the levels of active phosphorylated forms of extracellular signal-regulated kinases (ERK), Jun N-terminal kinases (JNK) and the p38 kinase in the hippocampus and frontal cortex in rats subjected to prenatal stress. The concentration of MAP kinase phosphatase (MKP-1, MKP-2) and protein phosphatase-2A (PP2A), which dephosphorylate all forms of MAP kinases, were also determined. During verification of the applied model of depression, we found that prenatally stressed rats displayed high level of immobility in the Porsolt test and that the administration of imipramine, fluoxetine, mirtazapine and tianeptine for 21 days normalized this parameter. Western blot study revealed that rats subjected to prenatal stress had decreased levels of p-JNK1 and p-JNK2 in the hippocampus and p-p38 in the frontal cortex, but the concentrations of p-ERK1 and p-ERK2 were not changed. Chronic treatment with imipramine inhibited the stress-induced decrease in p-JNK1/2, while imipramine, fluoxetine and mirtazapine blocked changes in p-p38. PP2A phosphatase level was higher in the hippocampus and frontal cortex in prenatally stressed animals than in control rats. Chronic treatment with antidepressant drugs attenuated the stress-induced increase in the level of this phosphatase, but had no effect on its concentration in control animals. There was no significant difference in MKP-1 and in MKP-2 levels in both brain structures between control and prenatally stressed rats. The obtained results showed that prenatal stress decreased the levels of active form of JNK and p38, but enhanced PP2A phosphatase expression and most of these changes were reversed by antidepressant drugs. Since p-JNK and p-p38 are known to inhibit GR function their lowered levels may enhance glucocorticoid action. Furthermore, the increased PP2A concentration may intensify GR action not only by inhibition of JNK and p38 phosphorylation, but also by a direct influence on the process of GR translocation.

11

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Bioaccumulation of microcystins in invasive bivalves: A case study from the boreal lagoon ecosystem

67%

Paldaviciene A., Zaiko A., Mazur-Marzec H., Razinkovas-Baziukas A.

Oceanologia

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2015

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tom 57

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nr 1

12

Induction of premature mitosis in root meristem cells of Vicia faba and Pisum sativum by various agents is correlated with an increased level of protein phosphorylation

67%

Rybaczek D., Polit J., Luchniak P., Maszewski J.

Folia Histochemica et Cytobiologica

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2002

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tom 40

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nr 1

13

Wplyw lacznego podania menadionu i metotreksatu na aktywnosc fosfataz bialkowych jader komorkowych watrobiaka Kirkmana-Robbins u chomikow obarczonych tym nowotworem

59%

Rozalski M., Krajewska U.

Bromatologia i Chemia Toksykologiczna

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1997

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tom 30

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nr 1

99-106

Podanie menadionu łącznie z małą dawką metotreksatu powodowało znaczne hamowanie rozrostu wątrobiaka Kirkmana-Robbins u chomików. Towarzyszyło temu obniżenie zawartości zredukowanego glutationu (GSH) w tkance wątrobiaka. Zastosowane leki antynowotworowe przyczyniały się do obniżenia aktywności jądrowych fosfataz białkowych wątrobiaka - enzymów odgrywających rolę w regulacji cyklu komórkowego. Spośród indywidualnych jądrowych substratów szczególnie słabo defosforyłowane były 32P-fosfoproteiny o małych masach cząsteczkowych.

Ograniczanie wyników

Protein phosphatase 2A: Variety of forms and diversity of functions

Rat brain Ca2plus - ATPase is a substrate for protein phosphatases PP1 and PP2A

Theoretical models of catalytic domains of protein phosphatases 1 and 2A with Zn2plus and Mn2plus metal dications and putative bioligands in their catalytic centers

Positive and negative regulatory mechanisms in high-affinity IgE receptor-mediated mast cell activation

Effect of OA-inhibitor of protein phosphatases PP1 and PP2A - on initiation of DNA replication and mitosis in Vicia faba root meristems

The opposite effects of cyclic AMP-protein kinase a signal transduction pathway on renal cortical and medullary Naplus, Kplus-ATPase activity

The 35 kDa acid metallophosphatase of the frog Rana esculenta liver: studies on its cellular localization and protein phosphatase activity

De novo synthesis of protein phosphatase 1A, magnesium dependent, alpha isoform (PPM1A) during oocyte maturation

Lokalizacja fosfataz bialkowych w subfrakcjach jader komorkowych watroby prawidlowej i watrobiaka Kirkmana-Robbins chomika

The decrease in JNK- and p38-MAP kinase activity is accompanied by the enhancement of PP2A phosphatase level in the brain of prenatally stressed rats

Bioaccumulation of microcystins in invasive bivalves: A case study from the boreal lagoon ecosystem

Induction of premature mitosis in root meristem cells of Vicia faba and Pisum sativum by various agents is correlated with an increased level of protein phosphorylation

Wplyw lacznego podania menadionu i metotreksatu na aktywnosc fosfataz bialkowych jader komorkowych watrobiaka Kirkmana-Robbins u chomikow obarczonych tym nowotworem