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The American Journal of Physiology Jan 1996The effects of pkadaic acid (OKA) and calyculin A (CLA), inhibitors of protein phosphatases type 1 (PrPase1) and type 2A (PrPase2A), an acid secretion were examined in...
The effects of pkadaic acid (OKA) and calyculin A (CLA), inhibitors of protein phosphatases type 1 (PrPase1) and type 2A (PrPase2A), an acid secretion were examined in rabbit isolated gastric gland, CLA, but not OKA, strongly stimulated acid secretion by itself without affecting glandular adenosine 3',5'-cyclic monophosphate (cAMP) contents. CLA-induced secretion was suggested to be mainly due to the increase in the phosphorylation of protein kinase A substrates via the inhibition of PrPase1 in the parietal cell, since 1) CLA-induced secretion was not inhibited by cimetidine or atropine, 2) a protein kinase A inhibitor inhibited the secretion, whereas a protein kinase C inhibitor did not, 3) CLA augmented dibutyryl cAMP-induced secretion in some cases, and 4) OKA, which is 100 times more selective to PrPase2A than to PrPase1, was not a secretagogue. Unexpectedly, CLA did not augment the secretion by histamine, possibly because the inhibitor augmented the phosphorylation-mediating negative feedback pathway as well. Both CLA and OKA markedly increased phosphorylation of ezrin, a putative protein kinase A substrate, in the course of secretory activation.
Topics: 4-Nitrophenylphosphatase; Animals; Cyclic AMP; Gastric Acid; Gastric Mucosa; In Vitro Techniques; Marine Toxins; Okadaic Acid; Oxazoles; Phosphoprotein Phosphatases; Phosphorylation; Proteins; Rabbits; Stimulation, Chemical
PubMed: 8772507
DOI: 10.1152/ajpgi.1996.270.1.G103 -
Ciba Foundation Symposium 1992Fission yeast has at least ten protein phosphatase genes that appear to play distinct roles in cell cycle control. Because of functional overlap, a clear lethal... (Review)
Review
Fission yeast has at least ten protein phosphatase genes that appear to play distinct roles in cell cycle control. Because of functional overlap, a clear lethal phenotype can be obtained only after multiple genetic alterations. Cells that have lost the protein phosphatase 1 (PP1)-like dis2/sds21 phosphatase activities prematurely enter mitosis and remain in a defective mitotic state with high H1 kinase activity and without sister chromatid disjunction. The same phenotype can be obtained in the presence of hydroxyurea. Overexpression of PP1-like phosphatase, on the other hand, delays the entry into mitosis. Cells that have lost PP2A-like ppa2 phosphatase activity also prematurely enter mitosis with a reduction in cell size. This semi-wee phenotype is enhanced in delta ppa2 mutants treated with the phosphatase inhibitor, okadaic acid. Genetic interactions between ppa2 and mitotic regulators suggest that ppa1/ppa2 phosphatase may directly or indirectly inhibit p34cdc2/cyclin kinase. Thus both PP1- and PP2A-like phosphatases in fission yeast may negatively regulate entry into mitosis. The major property of the dis2/sds21 mutant which is distinct from those of the ppa2/ppa1 mutant is its failure to inactivate the p34cdc2/cyclin complex after entry into mitosis. A novel phosphatase regulator encoded by sds22+ binds to dis2 phosphatase and controls the substrate specificity which appears to become essential in the progression from metaphase to anaphase.
Topics: Cell Division; Phenotype; Phosphoprotein Phosphatases; Protein Phosphatase 1; Schizosaccharomyces
PubMed: 1336448
DOI: 10.1002/9780470514320.ch9 -
European Journal of Immunology Feb 1994Group I Burkitt's lymphoma cell lines and the B104 lymphoma cell line which expresses a phenotype of immature B cells undergo apoptosis after cross-linking of their...
Group I Burkitt's lymphoma cell lines and the B104 lymphoma cell line which expresses a phenotype of immature B cells undergo apoptosis after cross-linking of their surface immunoglobulin (Ig) receptors or after exposure to a calcium ionophore, while protein kinase C (PKC)-activating phorbol esters prevent such apoptosis. We show here that blockade of the phosphoprotein phosphatase calcineurin or phosphatase 2B by cyclosporin A (CsA) also protects these B cell lines against Ca(2+)-dependent apoptosis but not against apoptosis triggered by the PKC inhibitor chelerythrine or by serum deprivation. Okadaic acid, an inhibitor of phosphatases 1, 2A and 2C was ineffective. Among a series of human cytokines tested, only interferon-alpha and tumor necrosis factor-alpha were shown to protect against Ca(2+)-dependent apoptosis when used alone or in combination with CsA. In contrast to phorbol esters which block the progression into the S/G2 phases of the cell cycle, CsA partially restored the proliferation of cells exposed to the calcium ionophore. Altogether these data provide indirect evidence for the control of B cell apoptosis by the serine/threonine phosphorylation status of yet undefined key cellular substrates.
Topics: Antibodies, Anti-Idiotypic; Apoptosis; B-Lymphocytes; Calcineurin; Calcium; Calmodulin-Binding Proteins; Cell Line; Cyclosporine; Humans; Immunoglobulin M; In Vitro Techniques; Interferon-alpha; Ionomycin; Phosphoprotein Phosphatases; Protein Kinase C; Tumor Necrosis Factor-alpha
PubMed: 8299681
DOI: 10.1002/eji.1830240208 -
Metabolism: Clinical and Experimental Mar 1983Phosphoprotein phosphatases (phosphoprotein phosphohydrolase, EC 3.1.3.16) were partially purified from bovine thyroid with phosphorylated mixed histones, H1 histone and...
Phosphoprotein phosphatases (phosphoprotein phosphohydrolase, EC 3.1.3.16) were partially purified from bovine thyroid with phosphorylated mixed histones, H1 histone and casein as substrates. Utilizing DEAE-cellulose chromatography, (NH4)2SO4 precipitation, gel filtration before and after freeze-thawing in 0.2 M 2-mercaptoethanol and histone-Sepharose chromatography, four fractions of enzyme activity were obtained and were designated as phosphatases I, IIA, IIB, and III. Phosphatases I had an apparent molecular weight of 155,000 and was dependent on Mn2+ for maximal activity. The enzyme had the greatest activity with histone H1 and was greatly stimulated by NaCl with phosphohistones as substrate. Phosphatases IIA and IIB had a molecular weight of about 70,000, were stimulated over 5-fold by Mn2+ and had much higher activities with phosphohistones than with casein in the presence of the cation. Phosphatase III, a possible catalytic subunit of larger molecular weight forms, had an apparent molecular weight of 30,000, was generally independent of Mn2+ and had high activities using all three substrates. Phosphatases I, IIA, and III were inhibited in a dose-dependent manner by sodium pyrophosphate (PPi), ATP, potassium phosphate (Pi) and sodium fluoride (NaF) when they were added directly to the reaction mixture with phosphorylated mixed histones as substrate. PPi was the most potent inhibitor and phosphatase III was the most sensitive to inhibition. PPi, ATP and NaF probably inactivated phosphatase III activity by removing an essential metal ion. After extensive dialysis to remove these inhibitors, the inactivated enzyme could be fully activated by Mn2+, but not by Mg2+, Ba2+, Cu2+, Cd2+, Ca2+, Zn2+ and Fe2+. Whereas the enzyme pretreated with Pi retained about 80% activity after dialysis, its activity was not further stimulated by Mn2+. The inactivated (demetallized) enzyme was less reactivated by Mn2+ in the presence of mM concentration of Pi. Moreover, the Mn2+-reactivated enzyme was again inactivated by Pi, NaF and ATP. Among them Pi was the most potent inactivator. These results suggest that Pi may have another inhibitory effect on metal ion binding besides on substrate binding and also that phosphatase III might be a metalloenzyme. In bovine thyroid, there are at least two major phosphoprotein phosphatases which may have different properties. Metal ion stimulation of phosphatase I and IIA activities may be through an interaction with the substrate or with a metal ion binding site on the regulatory subunit. The lowest molecular weight enzyme (phosphatase III) probably does not exist naturally in the cell.
Topics: Adenosine Triphosphate; Animals; Catalysis; Cattle; Chemical Phenomena; Chemistry; Enzyme Activation; Hydrogen-Ion Concentration; Magnesium; Manganese; Phosphates; Phosphoprotein Phosphatases; Sodium Chloride; Sodium Fluoride; Substrate Specificity; Thyroid Gland
PubMed: 6298568
DOI: 10.1016/0026-0495(83)90196-8 -
Recent Advances in Studies on Cardiac...Similar time courses were obtained for decreases in the rate of calcium transport by cardiac sarcoplasmic reticulum vesicles previously phosphorylated by cAMP-dependent...
Similar time courses were obtained for decreases in the rate of calcium transport by cardiac sarcoplasmic reticulum vesicles previously phosphorylated by cAMP-dependent protein kinase and dephosphorylation of the 22,000-dalton phosphoprotein in these membranes. Dephosphorylation of the 22,000-dalton phosphoprotein can be attributed to a phosphoprotein phosphatase in the sarcoplasmic reticular membranes. This membrane-bound phosphoprotein phosphatase may play a role in the reversal of the relaxation-promoting effect of catecholamines on the heart.
Topics: Animals; Biological Transport, Active; Calcium; Kinetics; Membrane Proteins; Membranes; Microsomes; Molecular Weight; Myocardium; Osmolar Concentration; Phosphoprotein Phosphatases; Phosphoproteins; Protein Kinases; Sarcoplasmic Reticulum
PubMed: 201987
DOI: No ID Found -
Current Topics in Cellular Regulation 1982
Review
Topics: Alkaline Phosphatase; Allosteric Regulation; Animals; Cations; Glutathione; Glutathione Disulfide; Glycogen-Synthase-D Phosphatase; Immunoglobulin G; Isoenzymes; Liver; Membrane Proteins; Molecular Weight; Muscles; Phosphoprotein Phosphatases; Phosphotyrosine; Pyruvate Dehydrogenase Complex; Rabbits; Rats; Substrate Specificity; Tyrosine
PubMed: 6183053
DOI: No ID Found -
Archives of Biochemistry and Biophysics Apr 1986A fluoride-insensitive, non-metal-requiring pyruvate dehydrogenase phosphatase has been purified 730-fold from pigeon liver acetone powder and proven to be a convenient...
A fluoride-insensitive, non-metal-requiring pyruvate dehydrogenase phosphatase has been purified 730-fold from pigeon liver acetone powder and proven to be a convenient reagent for studies of pyruvate dehydrogenase complex and its activation (phosphorylation) state in brain and other tissues. This phosphatase is a cytoplasmic enzyme (Mr = 80,000), and fits the functional definition of a type 1 phosphoprotein phosphatase. The pigeon liver phosphatase can be used to activate pyruvate dehydrogenase complex in vitro in brain and other crude tissue homogenates. Addition of the cytoplasmic pigeon liver phosphatase to a homogenate from rat or mouse brain frozen in situ activated pyruvate dehydrogenase to levels comparable to that found in ischemic brain. The fluoride insensitivity of this phosphatase was used to develop a convenient technique for stopping the pyruvate dehydrogenase activation state in situ in cultured skin fibroblasts and then fully activating the complex in vitro in 5 min. The use of this phosphatase as a reagent can facilitate the study of pyruvate dehydrogenase activation defects in mammalian tissues including cultured cells in normal and disease states.
Topics: Animals; Brain; Cells, Cultured; Columbidae; Cytoplasm; Enzyme Activation; Fibroblasts; Liver; Mice; Phosphoprotein Phosphatases; Pyruvate Dehydrogenase (Lipoamide)-Phosphatase; Pyruvate Dehydrogenase Complex; Rats
PubMed: 3008658
DOI: 10.1016/0003-9861(86)90483-2 -
The Biochemical Journal Jan 2009Protein phosphorylation appears to be a universal mechanism of protein regulation. Genomics has provided the means to compile inventories of protein phosphatases across... (Review)
Review
Protein phosphorylation appears to be a universal mechanism of protein regulation. Genomics has provided the means to compile inventories of protein phosphatases across a wide selection of organisms and this has supplied insights into the evolution of this group of enzymes. Protein phosphatases evolved independently several times yielding the groups we observe today. Starting from a core catalytic domain, phosphatases evolved by a series of gene duplication events and by adopting the use of regulatory subunits and/or fusion with novel functional modules or domains. Recent analyses also suggest that the serine/threonine specific enzymes are more ancient than the PTPs (protein tyrosine phosphatases). It is likely that the latter played a key role at the onset of metazoan evolution in conjunction with the tremendous expansion of tyrosine kinases and PTPs at this point. In the present review, we discuss the evolution of the PTPs, the serine/threonine specific PPP (phosphoprotein phosphatase) and PPM (metallo-dependent protein phosphatase) families and the more recently discovered phosphatases that utilize an aspartate-based catalytic mechanism. We will also highlight examples of convergent evolution and several phosphatases which are unique to plants.
Topics: Animals; Enzyme Activation; Evolution, Molecular; Humans; Phosphoprotein Phosphatases; Plants; Protein Subunits; Substrate Specificity
PubMed: 19099538
DOI: 10.1042/BJ20081986 -
European Journal of Biochemistry Sep 1979The phosphorylation of Ser-32, in addition to Ser-36 of H2B histone, stimulated the rate of Pi release from Ser-36 by the small form (Mr 31 000) of pig heart...
The phosphorylation of Ser-32, in addition to Ser-36 of H2B histone, stimulated the rate of Pi release from Ser-36 by the small form (Mr 31 000) of pig heart phosphoprotein phosphatase both in the absence and presence of 50 mM magnesium acetate. By phosphorylation at Ser-32, the Km value for Ser-36 phosphate in H2B histone was increased from 0.38 microM to 1.16 microM in the absence of magnesium acetate, but not significantly changed (from 37.4 microM to 26.2 microM) in the presence of magnesium acetate. With the large form (Mr 224000) of the phosphoprotein phosphatase, however, the phosphorylation at Ser-32 suppressed the rate of Pi release from Ser-36 both in the absence and presence of magnesium acetate. The Km value of the large form for Ser-36 phosphatase in H2B histone was nevertheless increased by phosphorylation at Ser-32, from 1.2 microM to 5.3 microM in the presence of magnesium acetate, but not changed (from 0.26 microM to 0.23 microM) in the absence of magnesium acetate.
Topics: Animals; Cattle; Histones; Kinetics; Phosphoprotein Phosphatases; Phosphorylation; Serine
PubMed: 227681
DOI: 10.1111/j.1432-1033.1979.tb13270.x -
Cellular and Molecular Life Sciences :... Oct 2009PPEF/PP7 represents one of the five subfamilies of the PPP protein Ser/Thr phosphatases. Studies published in recent years point to a role of plant PP7 at a crossroad of... (Review)
Review
PPEF/PP7 represents one of the five subfamilies of the PPP protein Ser/Thr phosphatases. Studies published in recent years point to a role of plant PP7 at a crossroad of different pathways of light and stress signalling. In animals, PPEFs are highly expressed in sensory neurons, and Drosophila PPEF phosphatase, rdgC, is essential for dephosphorylation of rhodopsin. Expression profiling suggests that mammalian PPEF may play a role in stress-protective responses, cell survival, growth, proliferation, and oncogenesis. Despite structural similarities of the catalytic domains and the fact that some of these phosphatases are involved in light perception both in animals and in plants, the plant and non-plant representatives of this group have distinct domain architecture and appear not to be orthologues.
Topics: Animals; Binding Sites; EF Hand Motifs; Humans; Phosphoprotein Phosphatases; Plant Proteins; Protein Structure, Tertiary
PubMed: 19662497
DOI: 10.1007/s00018-009-0110-7