Articoli di riviste: "Phosphoprotein phosphatases"

1

Shacter, Emily, Joseph A. McClure, Edward D. Korn e P. Boon Chock. "Immunological characterization of phosphoprotein phosphatases". Archives of Biochemistry and Biophysics 242, n. 2 (novembre 1985): 523–31. http://dx.doi.org/10.1016/0003-9861(85)90239-5.

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Li, Qiang, Minglong Li, Huiying Ma, Man Xue, Tong Chen, Xiaodong Ding, Shuzhen Zhang e Jialei Xiao. "Quantitative Phosphoproteomic Analysis Provides Insights into the Sodium Bicarbonate Responsiveness of Glycine max". Biomolecules 13, n. 10 (13 ottobre 2023): 1520. http://dx.doi.org/10.3390/biom13101520.

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Sodium bicarbonate stress caused by NaHCO3 is one of the most severe abiotic stresses affecting agricultural production worldwide. However, little attention has been given to the molecular mechanisms underlying plant responses to sodium bicarbonate stress. To understand phosphorylation events in signaling pathways triggered by sodium bicarbonate stress, TMT-labeling-based quantitative phosphoproteomic analyses were performed on soybean leaf and root tissues under 50 mM NaHCO3 treatment. In the present study, a total of 7856 phosphopeptides were identified from cultivated soybeans (Glycine max L. Merr.), representing 3468 phosphoprotein groups, in which 2427 phosphoprotein groups were newly identified. These phosphoprotein groups contained 6326 unique high-probability phosphosites (UHPs), of which 77.2% were newly identified, increasing the current soybean phosphosite database size by 43.4%. Among the phosphopeptides found in this study, we determined 67 phosphopeptides (representing 63 phosphoprotein groups) from leaf tissue and 554 phosphopeptides (representing 487 phosphoprotein groups) from root tissue that showed significant changes in phosphorylation levels under sodium bicarbonate stress (fold change >1.2 or <0.83, respectively; p < 0.05). Localization prediction showed that most phosphoproteins localized in the nucleus for both leaf and root tissues. GO and KEGG enrichment analyses showed quite different enriched functional terms between leaf and root tissues, and more pathways were enriched in the root tissue than in the leaf tissue. Moreover, a total of 53 different protein kinases and 7 protein phosphatases were identified from the differentially expressed phosphoproteins (DEPs). A protein kinase/phosphatase interactor analysis showed that the interacting proteins were mainly involved in/with transporters/membrane trafficking, transcriptional level regulation, protein level regulation, signaling/stress response, and miscellaneous functions. The results presented in this study reveal insights into the function of post-translational modification in plant responses to sodium bicarbonate stress.

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Vincent, John B., e Bruce A. Averill. "Sequence homology between purple acid phosphatases and phosphoprotein phosphatases". FEBS Letters 263, n. 2 (24 aprile 1990): 265–68. http://dx.doi.org/10.1016/0014-5793(90)81389-6.

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Zhang, Qingxiu, e Francois X. Claret. "Phosphatases: The New Brakes for Cancer Development?" Enzyme Research 2012 (31 ottobre 2012): 1–11. http://dx.doi.org/10.1155/2012/659649.

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The phosphatidylinositol 3-kinase (PI3K) pathway plays a pivotal role in the maintenance of processes such as cell growth, proliferation, survival, and metabolism in all cells and tissues. Dysregulation of the PI3K/Akt signaling pathway occurs in patients with many cancers and other disorders. This aberrant activation of PI3K/Akt pathway is primarily caused by loss of function of all negative controllers known as inositol polyphosphate phosphatases and phosphoprotein phosphatases. Recent studies provided evidence of distinct functions of the four main phosphatases—phosphatase and tensin homologue deleted on chromosome 10 (PTEN), Src homology 2-containing inositol 5′-phosphatase (SHIP), inositol polyphosphate 4-phosphatase type II (INPP4B), and protein phosphatase 2A (PP2A)—in different tissues with respect to regulation of cancer development. We will review the structures and functions of PTEN, SHIP, INPP4B, and PP2A phosphatases in suppressing cancer progression and their deregulation in cancer and highlight recent advances in our understanding of the PI3K/Akt signaling axis.

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Miller, W. Todd. "Tyrosine Phosphoprotein Phosphatases. Barry J. Goldstein". Quarterly Review of Biology 74, n. 4 (dicembre 1999): 464–65. http://dx.doi.org/10.1086/394141.

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Moorhead, Greg B. G., Veerle De Wever, George Templeton e David Kerk. "Evolution of protein phosphatases in plants and animals". Biochemical Journal 417, n. 2 (23 dicembre 2008): 401–9. http://dx.doi.org/10.1042/bj20081986.

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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.

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Miskei, Márton, Csaba Ádám, László Kovács, Zsolt Karányi e Viktor Dombrádi. "Molecular Evolution of Phosphoprotein Phosphatases in Drosophila". PLoS ONE 6, n. 7 (15 luglio 2011): e22218. http://dx.doi.org/10.1371/journal.pone.0022218.

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Butler, Trent, Jonathan Paul, Nick Europe-Finner, Roger Smith e Eng-Cheng Chan. "Role of serine-threonine phosphoprotein phosphatases in smooth muscle contractility". American Journal of Physiology-Cell Physiology 304, n. 6 (15 marzo 2013): C485—C504. http://dx.doi.org/10.1152/ajpcell.00161.2012.

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The degree of phosphorylation of myosin light chain 20 (MLC20) is a major determinant of force generation in smooth muscle. Myosin phosphatases (MPs) contain protein phosphatase (PP) 1 as catalytic subunits and are the major enzymes that dephosphorylate MLC20. MP regulatory targeting subunit 1 (MYPT1), the main regulatory subunit of MP in all smooth muscles, is a key convergence point of contractile and relaxatory pathways. Combinations of regulatory mechanisms, including isoform splicing, multiple phosphorylation sites, and scaffolding proteins, modulate MYPT1 activity with tissue and agonist specificities to affect contraction and relaxation. Other members of the PP1 family that do not target myosin, as well as PP2A and PP2B, dephosphorylate a range of proteins that affect smooth muscle contraction. This review discusses the role of phosphatases in smooth muscle contractility with a focus on MYPT1 in uterine smooth muscle. Myometrium shares characteristics of vascular and other visceral smooth muscles yet, during healthy pregnancy, undergoes hypertrophy, hyperplasia, quiescence, and labor as physiological processes. Myometrium presents an accessible model for the study of normal and pathological smooth muscle function, and a better understanding of myometrial physiology may allow the development of novel therapeutics for the many disorders of myometrial physiology from preterm labor to dysmenorrhea.

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Garvanska, Dimitriya H., e Jakob Nilsson. "Specificity determinants of phosphoprotein phosphatases controlling kinetochore functions". Essays in Biochemistry 64, n. 2 (5 giugno 2020): 325–36. http://dx.doi.org/10.1042/ebc20190065.

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Abstract Kinetochores are instrumental for accurate chromosome segregation by binding to microtubules in order to move chromosomes and by delaying anaphase onset through the spindle assembly checkpoint (SAC). Dynamic phosphorylation of kinetochore components is key to control these activities and is tightly regulated by temporal and spatial recruitment of kinases and phosphoprotein phosphatases (PPPs). Here we focus on PP1, PP2A-B56 and PP2A-B55, three PPPs that are important regulators of mitosis. Despite the fact that these PPPs share a very similar active site, they target unique ser/thr phosphorylation sites to control kinetochore function. Specificity is in part achieved by PPPs binding to short linear motifs (SLiMs) that guide their substrate specificity. SLiMs bind to conserved pockets on PPPs and are degenerate in nature, giving rise to a range of binding affinities. These SLiMs control the assembly of numerous substrate specifying complexes and their position and binding strength allow PPPs to target specific phosphorylation sites. In addition, the activity of PPPs is regulated by mitotic kinases and inhibitors, either directly at the activity level or through affecting PPP–SLiM interactions. Here, we discuss recent progress in understanding the regulation of PPP specificity and activity and how this controls kinetochore biology.

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Sahin, Ali, Francesca G. Tencalla, Daniel R. Dietrich, Konstanze Mez e Hanspeter Naegeli. "Enzymatic analysis of liver samples from rainbow trout for diagnosis of blue-green algae-induced toxicosis". American Journal of Veterinary Research 56, n. 8 (1 agosto 1995): 1110–15. http://dx.doi.org/10.2460/ajvr.1995.56.08.1110.

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SUMMARY Microcystin and related toxic peptides produced by cyanobacteria (blue-green algae) are potent and selective inhibitors of protein phosphatases 1 and 2A. We adapted existing enzymatic techniques to analyze the liver of rainbow trout after oral administration of hepatotoxic cyanobacteria. Liver tissue was removed 3 and 12 hours after treatment, and phosphatase activity was determined in liver extracts, using a specific phosphoprotein substrate. In all samples from fish exposed to toxic cyanobacteria, phosphatase activity was suppressed, whereas the control enzyme, lactate dehydrogenase, present in the same liver extract, was not affected by cyanobacteria. Thus, experimental poisoning by hepatotoxic cyanobacteria resulted in an abnormally low ratio of phosphatase to lactate dehydrogenase activity in the liver extracts. These results indicate that specific inhibition of phosphatases 1 and 2A may provide a useful diagnostic tool to determine the early effects of cyanobacteria toxic peptides directly in liver samples from poisoned animals. Although this test was developed with rainbow trout, it should be possible to extend the analysis of liver phosphatase activity to other species, including sheep and cattle, which are frequently affected by hepatotoxic cyanobacteria.

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MISTRY, Sucharita J., Heng-Chun LI e George F. ATWEH. "Role for protein phosphatases in the cell-cycle-regulated phosphorylation of stathmin". Biochemical Journal 334, n. 1 (15 agosto 1998): 23–29. http://dx.doi.org/10.1042/bj3340023.

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Stathmin is a major cytosolic phosphoprotein that regulates microtubule dynamics during the assembly of the mitotic spindle. The activity of stathmin itself is regulated by changes in its state of phosphorylation during the transition from interphase to metaphase. For a better understanding of the regulation of stathmin activity during the cell cycle, we explored the mechanism(s) responsible for the decrease in the level of phosphorylation of stathmin as cells complete mitosis and enter a new G1 phase. We show that stathmin mRNA and protein are expressed constitutively throughout the different phases of the cell cycle. This suggests that the non-phosphorylated stathmin that predominates during G1 is not generated by degradation of phosphorylated stathmin in mitosis and synthesis of new unphosphorylated stathmin as cells enter a new G1 phase. This suggested that protein phosphatases might be responsible for dephosphorylating stathmin as cells enter a new cell cycle. Okadaic acid-mediated inhibition of protein phosphatases in vivoshowed a major increase in the level of phosphorylation of stathmin. Dephosphorylation studies in vitro showed differential patterns of site-specific dephosphorylaton of stathmin to protein phosphatase type 1, protein phosphatase type 2A and protein phosphatase type 2B. Thus stathmin might be a target for okadaic acid-sensitive protein phosphatase(s), and its activity in eukaryotic cells might be modulated by the sequential activity of specific protein kinases and phosphatases.

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Wheeler-Jones, Caroline P. D., Rebecca A. Houliston e Jeremy D. Pearson. "Inhibitors of phosphoprotein phosphatases modulate p42mapk phosphorylation in endothelium". Blood Coagulation & Fibrinolysis 6, n. 2 (aprile 1995): 173. http://dx.doi.org/10.1097/00001721-199504000-00068.

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Burns, Chris J., Shân L. Gyles, Shanta J. Persaud, David Sugden, Barbara J. Whitehouse e Peter M. Jones. "Phosphoprotein Phosphatases Regulate Steroidogenesis by Influencing StAR Gene Transcription". Biochemical and Biophysical Research Communications 273, n. 1 (giugno 2000): 35–39. http://dx.doi.org/10.1006/bbrc.2000.2890.

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Ford, S. L., D. R. E. Abayasekara, S. J. Persaud e P. M. Jones. "Role of phosphoprotein phosphatases in the corpus luteum: I Identification and characterisation of serine/threonine phosphoprotein phosphatases in isolated rat luteal cells". Journal of Endocrinology 150, n. 2 (agosto 1996): 205–11. http://dx.doi.org/10.1677/joe.0.1500205.

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Abstract Although the role of protein kinases and phosphorylation in steroidogenesis has received much attention, very little is known about the activities of phosphoprotein phosphatases (PP) and dephosphorylation in steroidogenic tissues. The aims of the present study were therefore to identify which of those serine/threonine PPs more commonly involved in intracellular signalling are expressed in rat luteal cells; to quantify, in vitro, the effects of inhibitors on PP activity extracted from purified rat luteal cells; and to measure the effects of PP inhibitors on the phosphorylation of endogenous luteal cell proteins. Polyclonal antibodies raised against the catalytic subunits of PP types 1 and 2A, and a monoclonal antibody raised against the Ca2+-binding subunit of PP2B, were used to identify immunoreactive proteins that migrated on SDS-PAGE with approximate molecular masses of 37, 34 and 16 kDa, corresponding well with the reported molecular mass of PP1, PP2A and PP2B respectively. Five selective inhibitors of PP1/PP2A: okadaic acid, calyculin A, cantharidin, tautomycin and microcystin-RR, each caused a dose-dependent decrease in the activity of PPs in luteal cell homogenates, and also enhanced 32P incorporation into numerous luteal cell proteins; most notably, proteins with approximate molecular masses of 20 and 22 kDa. The results of this study suggest that PPs may play an important role in the regulation of rat luteal cell functions. Journal of Endocrinology (1996) 150, 205–211

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Moradi, Atieh, Shuaijian Dai, Emily Oi Ying Wong, Guang Zhu, Fengchao Yu, Hon-Ming Lam, Zhiyong Wang et al. "Isotopically Dimethyl Labeling-Based Quantitative Proteomic Analysis of Phosphoproteomes of Soybean Cultivars". Biomolecules 11, n. 8 (16 agosto 2021): 1218. http://dx.doi.org/10.3390/biom11081218.

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Isotopically dimethyl labeling was applied in a quantitative post-translational modification (PTM) proteomic study of phosphoproteomic changes in the drought responses of two contrasting soybean cultivars. A total of 9457 phosphopeptides were identified subsequently, corresponding to 4571 phosphoprotein groups and 3889 leading phosphoproteins, which contained nine kinase families consisting of 279 kinases. These phosphoproteins contained a total of 8087 phosphosites, 6106 of which were newly identified and constituted 54% of the current soybean phosphosite repository. These phosphosites were converted into the highly conserved kinase docking sites by bioinformatics analysis, which predicted six kinase families that matched with those newly found nine kinase families. The overly post-translationally modified proteins (OPP) occupies 2.1% of these leading phosphoproteins. Most of these OPPs are photoreceptors, mRNA-, histone-, and phospholipid-binding proteins, as well as protein kinase/phosphatases. The subgroup population distribution of phosphoproteins over the number of phosphosites of phosphoproteins follows the exponential decay law, Y = 4.13e−0.098X − 0.04. Out of 218 significantly regulated unique phosphopeptide groups, 188 phosphoproteins were regulated by the drought-tolerant cultivar under the water loss condition. These significantly regulated phosphoproteins (SRP) are mainly enriched in the biological functions of water transport and deprivation, methionine metabolic processes, photosynthesis/light reaction, and response to cadmium ion, osmotic stress, and ABA response. Seventeen and 15 SRPs are protein kinases/phosphatases and transcription factors, respectively. Bioinformatics analysis again revealed that three members of the calcium dependent protein kinase family (CAMK family), GmSRK2I, GmCIPK25, and GmAKINβ1 kinases, constitute a phosphor-relay-mediated signal transduction network, regulating ion channel activities and many nuclear events in this drought-tolerant cultivar, which presumably contributes to the development of the soybean drought tolerance under water deprivation process.

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Abbasian, Nima, James O. Burton, Karl E. Herbert, Barbara-Emily Tregunna, Jeremy R. Brown, Maryam Ghaderi-Najafabadi, Nigel J. Brunskill, Alison H. Goodall e Alan Bevington. "Hyperphosphatemia, Phosphoprotein Phosphatases, and Microparticle Release in Vascular Endothelial Cells". Journal of the American Society of Nephrology 26, n. 9 (5 marzo 2015): 2152–62. http://dx.doi.org/10.1681/asn.2014070642.

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Rietz, A., e JP Spiers. "The relationship between the MMP system, adrenoceptors and phosphoprotein phosphatases". British Journal of Pharmacology 166, n. 4 (17 maggio 2012): 1225–43. http://dx.doi.org/10.1111/j.1476-5381.2012.01917.x.

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Taylor, William P., e Theodore S. Widlanski. "Charged with meaning: the structure and mechanism of phosphoprotein phosphatases". Chemistry & Biology 2, n. 11 (novembre 1995): 713–18. http://dx.doi.org/10.1016/1074-5521(95)90098-5.

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Mivechi, N. F., L. D. Trainor e G. M. Hahn. "Purified Mammalian HSP-70 kDa Activates Phosphoprotein Phosphatases in Vitro". Biochemical and Biophysical Research Communications 192, n. 2 (aprile 1993): 954–63. http://dx.doi.org/10.1006/bbrc.1993.1508.

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Smith, Robert D., e John C. Walker. "Expression of multiple type 1 phosphoprotein phosphatases in Arabidopsis thaliana". Plant Molecular Biology 21, n. 2 (gennaio 1993): 307–16. http://dx.doi.org/10.1007/bf00019946.

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Pereira, Susana R., Vítor M. Vasconcelos e Agostinho Antunes. "The phosphoprotein phosphatase family of Ser/Thr phosphatases as principal targets of naturally occurring toxins". Critical Reviews in Toxicology 41, n. 2 (febbraio 2011): 83–110. http://dx.doi.org/10.3109/10408444.2010.515564.

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DESDOUITS, Frédéric, C. Julio SICILIANO, C. Angus NAIRN, Paul GREENGARD e Jean-Antoine GIRAULT. "Dephosphorylation of Ser-137 in DARPP-32 by protein phosphatases 2A and 2C: different roles in vitro and in striatonigral neurons". Biochemical Journal 330, n. 1 (15 febbraio 1998): 211–16. http://dx.doi.org/10.1042/bj3300211.

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DARPP-32 (dopamine- and cAMP-regulated phosphoprotein, Mr = 32000) is highly expressed in striatonigral neurons in which its phosphorylation is regulated by several neurotransmitters including dopamine and glutamate. DARPP-32 becomes a potent inhibitor of protein phosphatase 1 when it is phosphorylated on Thr-34 by cAMP- or cGMP-dependent protein kinases. DARPP-32 is also phosphorylated on Ser-137 by protein kinase CK1 (CK1), in vitro and in vivo. This phosphorylation has an important regulatory role since it inhibits the dephosphorylation of Thr-34 by calcineurin in vitro and in striatonigral neurons. Here, we show that DARPP-32 phosphorylated by CK1 is a substrate in vitro for protein phosphatases 2A and 2C, but not protein phosphatase 1 or calcineurin. However, in substantia nigra slices, dephosphorylation of Ser-137 was markedly sensitive to decreased temperature, and not detectably affected by the presence of okadaic acid under conditions in which dephosphorylation of Thr-34 by protein phosphatase 2A was inhibited. These results suggest that, in neurons, phospho-Ser-137-DARPP-32 is dephosphorylated by protein phosphatase 2C, but not 2A. Thus, DARPP-32 appears to be a component of a regulatory cascade of phosphatases in which dephosphorylation of Ser-136 by protein phosphatase 2C facilitates dephosphorylation of Thr-34 by calcineurin, removing the cyclic nucleotide-induced inhibition of protein phosphatase 1.

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Palmer, Frederick B. St C. "Identification of the phosphomonoesterases that hydrolyze lysopolyphosphoinositides in rat brain and liver". Biochemistry and Cell Biology 65, n. 10 (1 ottobre 1987): 890–98. http://dx.doi.org/10.1139/o87-115.

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The phosphatase activities responsible for the sequential dephosphorylation of lysophosphatidylinositol 4,5-bisphosphate (lysoPtdIns(4,5)P2) to lysophosphatidylinositol that precedes reacylation in rat brain and liver microsomes were characterized. LysoPtdIns(4,5)P2 and the intermediate lysophosphatidylinositol 4-phosphate (lysoPtdIns4P) were hydrolyzed by two distinct phosphatase activities which were distinguishable by their substrate and cation requirements. The lysoPtdIns(4,5)P2 phosphatase activity was Mg2+ dependent and partially inhibited by Ca2+, excess Mg2+, and cationic detergent (cetyltrimethylammonium bromide). Activity was maximal at neutral (brain) or slightly alkaline (liver) pH when the Mg2+/lysoPtdIns(4,5)P2 molar ratio was 1.0 in the presence of bovine serum albumin (1 mg∙mL−1). LysoPtdIns4P phosphatase activity did not require divalent cations (not inhibited by EDTA). This activity was inhibited by Ca2+, Mg2+, and substrate concentrations above 0.2 mM. Maximum activity was observed over a broad pH range (6.0–8.5). Both activities were inhibited by lysophosphatidylinositol and lysophosphatidylcholine, but not other lysophospholipids. The lysopolyphosphoinositides are most likely hydrolyzed by the same phosphatases that act on the diacylpolyphosphoinositides, since PtdIns(4,5)P2 and PtdIns4P were also hydrolysed by Mg2+-dependent and cation-independent phosphatases, respectively. Activities with the diacylpolyphosphoinositides differed only in their requirement of detergents for maximum activity in vitro. Specific activities for the diacyl and "lyso" forms of each substrate were very similar when suitably optimized reaction mixtures were used. The subcellular distributions of the two phosphatase activities in both brain and liver were the same when acting on diacyl- or lyso-polyphosphoinositides, as was their response to inhibitors. Alkaline, acid, phosphoprotein, and inositol-1-phosphate phosphatases did not contribute substantially to the hydrolysis of either lysoPtdIns4P or lysoPtdIns(4,5)P2, since the activities were not significantly inhibited by cysteine, dithiothreitol, NaF, or LiCl. Lack of inhibition by 2,3-bisphosphoglycerate and absence of stimulation by cysteine or dithioerythritol, as well as a different subcellular distribution in liver, excluded inositol-1,4,5-trisphosphate and inositol-1,4-bisphosphate phosphatases as sources of the lysoPtdIns(4,5)P2 and lysoPtdIns4P phosphatase activities.

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Ohno, J., K. Fukuyama, A. Hara e W. L. Epstein. "Immuno- and enzyme-histochemical detection of phosphoprotein phosphatase in rat epidermis." Journal of Histochemistry & Cytochemistry 37, n. 5 (maggio 1989): 629–34. http://dx.doi.org/10.1177/37.5.2539408.

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A phosphoprotein phosphatase (PPase: EC 3.1.3.2) was recently purified from rat epidermis. The enzyme dephosphorylates phosphoprotein, and its properties, such as pH optimum, inhibitor spectrum, and Fe2+ activation, differ from those of other soluble phosphatases. We investigated in 2-day-old rat skin the distribution of immunologically detectable PPase and intracellular localization of PPase activity. The reaction of rabbit monospecific anti-PPase IgG was identified in granular and cornified cells by the avidin-biotin complex method. For activity staining, basic principles of the Gomori lead-salt method and azo dye technique with the substrates p-nitrophenylphosphate (p-NPP) and alpha-naphthyl phosphate (NP), respectively, were modified according to the biochemical properties of PPase activity which is resistant to formalin, Na tartrate, and NaF. Activity was detectable in granular cells including keratohyalin granules and the lower strata of cornified cells. The activity was inhibited by 1 mM CuSO4 and enhanced by a mixture of 0.5 mM FeSO4 and 1 mM ascorbic acid. We consider that PPase may be involved in dephosphorylation of histidine-rich proteins in granular and cornified cells and may play a key role in intracellular catabolism associated with epidermal cell differentiation.

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Pazy, Y., M. A. Motaleb, M. T. Guarnieri, N. W. Charon, R. Zhao e R. E. Silversmith. "Identical phosphatase mechanisms achieved through distinct modes of binding phosphoprotein substrate". Proceedings of the National Academy of Sciences 107, n. 5 (14 gennaio 2010): 1924–29. http://dx.doi.org/10.1073/pnas.0911185107.

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Two-component signal transduction systems are widespread in prokaryotes and control numerous cellular processes. Extensive investigation of sensor kinase and response regulator proteins from many two-component systems has established conserved sequence, structural, and mechanistic features within each family. In contrast, the phosphatases which catalyze hydrolysis of the response regulator phosphoryl group to terminate signal transduction are poorly understood. Here we present structural and functional characterization of a representative of the CheC/CheX/FliY phosphatase family. The X-ray crystal structure of Borrelia burgdorferi CheX complexed with its CheY3 substrate and the phosphoryl analogue reveals a binding orientation between a response regulator and an auxiliary protein different from that shared by every previously characterized example. The surface of CheY3 containing the phosphoryl group interacts directly with a long helix of CheX which bears the conserved (E - X2 - N) motif. Conserved CheX residues Glu96 and Asn99, separated by a single helical turn, insert into the CheY3 active site. Structural and functional data indicate that CheX Asn99 and CheY3 Thr81 orient a water molecule for hydrolytic attack. The catalytic residues of the CheX·CheY3 complex are virtually superimposable on those of the Escherichia coli CheZ phosphatase complexed with CheY, even though the active site helices of CheX and CheZ are oriented nearly perpendicular to one other. Thus, evolution has found two structural solutions to achieve the same catalytic mechanism through different helical spacing and side chain lengths of the conserved acid/amide residues in CheX and CheZ.

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Mukhopadhyay, Subhendu, Vinayak Kapatral, Wenbin Xu e A. M. Chakrabarty. "Characterization of a Hank’s Type Serine/Threonine Kinase and Serine/Threonine Phosphoprotein Phosphatase inPseudomonas aeruginosa". Journal of Bacteriology 181, n. 21 (1 novembre 1999): 6615–22. http://dx.doi.org/10.1128/jb.181.21.6615-6622.1999.

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ABSTRACT Pseudomonas aeruginosa is an opportunistic pathogen that causes infections in eye, urinary tract, burn, and immunocompromised patients. We have cloned and characterized a serine/threonine (Ser/Thr) kinase and its cognate phosphoprotein phosphatase. By using oligonucleotides from the conserved regions of Ser/Thr kinases of mycobacteria, an 800-bp probe was used to screenP. aeruginosa PAO1 genomic library. A 20-kb cosmid clone was isolated, from which a 4.5-kb DNA with two open reading frames (ORFs) were subcloned. ORF1 was shown to encode Ser/Thr phosphatase (Stp1), which belongs to the PP2C family of phosphatases. Overlapping with the stp1 ORF, an ORF encoding Hank’s type Ser/Thr kinase was identified. Both ORFs were cloned in pGEX-4T1 and expressed in Escherichia coli. The overexpressed proteins were purified by glutathione-Sepharose 4B affinity chromatography and were biochemically characterized. The Stk1 kinase is 39 kDa and undergoes autophosphorylation and can phosphorylate eukaryotic histone H1. A site-directed Stk1 (K86A) mutant was shown to be incapable of autophosphorylation. A two-dimensional phosphoamino acid analysis of Stk1 revealed strong phosphorylation at a threonine residue and weak phosphorylation at a serine residue. The Stp1 phosphatase is 27 kDa and is an Mn2+-, but not a Ca2+- or a Mg2+-, dependent Ser/Thr phosphatase. Its activity is inhibited by EDTA and NaF, but not by okadaic acid, and is similar to that of PP2C phosphatase.

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Perry, M. D., e G. I. Sandle. "Regulation of colonic apical potassium (BK) channels by cAMP and somatostatin". American Journal of Physiology-Gastrointestinal and Liver Physiology 297, n. 1 (luglio 2009): G159—G167. http://dx.doi.org/10.1152/ajpgi.00132.2009.

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High-conductance apical K+(BK) channels are present in surface colonocytes of mammalian (including human) colon. Their location makes them well fitted to contribute to the excessive intestinal K+losses often associated with infective diarrhea. Since many channel proteins are regulated by phosphorylation, we evaluated the roles of protein kinase A (PKA) and phosphatases in the modulation of apical BK channel activity in surface colonocytes from rat distal colon using patch-clamp techniques, having first increased channel abundance by chronic dietary K+enrichment. We found that PKA activation using 50 μmol/l forskolin and 5 mmol/l 3-isobutyl-1-methylxanthine stimulated BK channels in cell-attached patches and the catalytic subunit of PKA (200 U/ml) had a similar effect in excised inside-out patches. The antidiarrheal peptide somatostatin (SOM; 2 μmol/l) had a G protein-dependent inhibitory effect on BK channels in cell-attached patches, which was unaffected by pretreatment with 10 μmol/l okadaic acid (an inhibitor of protein phosphatase type 1 and type 2A) but completely prevented by pretreatment with 100 μmol/l Na+orthovanadate and 10 μmol/l BpV (inhibitors of phosphoprotein tyrosine phosphatase). SOM also inhibited apical BK channels in surface colonocytes in human distal colon. We conclude that cAMP-dependent PKA activates apical BK channels and may enhance colonic K+losses in some cases of secretory diarrhea. SOM inhibits apical BK channels through a phosphoprotein tyrosine phosphatase-dependent mechanism, which could form the basis of new antidiarrheal strategies.

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Lajarín-Cuesta, Rocío, Raquel L. Arribas e Cristóbal De Los Ríos. "Ligands for Ser/Thr phosphoprotein phosphatases: a patent review (2005-2015)". Expert Opinion on Therapeutic Patents 26, n. 3 (7 febbraio 2016): 389–407. http://dx.doi.org/10.1517/13543776.2016.1135903.

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29

Ádám, Csaba, László Henn, Márton Miskei, Miklós Erdélyi, Péter Friedrich e Viktor Dombrádi. "Conservation of male-specific expression of novel phosphoprotein phosphatases in Drosophila". Development Genes and Evolution 220, n. 3-4 (15 luglio 2010): 123–28. http://dx.doi.org/10.1007/s00427-010-0332-6.

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30

Pidoux, Guillaume, e Kjetil Taskén. "Specificity and spatial dynamics of protein kinase A signaling organized by A-kinase-anchoring proteins". Journal of Molecular Endocrinology 44, n. 5 (11 febbraio 2010): 271–84. http://dx.doi.org/10.1677/jme-10-0010.

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Abstract (sommario):

Protein phosphorylation is the most common post-translational modification observed in cell signaling and is controlled by the balance between protein kinase and phosphatase activities. The cAMP–protein kinase A (PKA) pathway is one of the most studied and well-known signal pathways. To maintain a high level of specificity, the cAMP–PKA pathway is tightly regulated in space and time. A-kinase-anchoring proteins (AKAPs) target PKA to specific substrates and distinct subcellular compartments providing spatial and temporal specificity in the mediation of biological effects controlled by the cAMP–PKA pathway. AKAPs also serve as scaffolding proteins that assemble PKA together with signal terminators such as phosphoprotein phosphatases and cAMP-specific phosphodiesterases as well as components of other signaling pathways into multiprotein-signaling complexes.

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31

Turowski, Patric, Timothy Myles, Brian A. Hemmings, Anne Fernandez e Ned J. C. Lamb. "Vimentin Dephosphorylation by Protein Phosphatase 2A Is Modulated by the Targeting Subunit B55". Molecular Biology of the Cell 10, n. 6 (giugno 1999): 1997–2015. http://dx.doi.org/10.1091/mbc.10.6.1997.

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The intermediate filament protein vimentin is a major phosphoprotein in mammalian fibroblasts, and reversible phosphorylation plays a key role in its dynamic rearrangement. Selective inhibition of type 2A but not type 1 protein phosphatases led to hyperphosphorylation and concomitant disassembly of vimentin, characterized by a collapse into bundles around the nucleus. We have analyzed the potential role of one of the major protein phosphatase 2A (PP2A) regulatory subunits, B55, in vimentin dephosphorylation. In mammalian fibroblasts, B55 protein was distributed ubiquitously throughout the cytoplasm with a fraction associated to vimentin. Specific depletion of B55 in living cells by antisense B55 RNA was accompanied by disassembly and increased phosphorylation of vimentin, as when type 2A phosphatases were inhibited using okadaic acid. The presence of B55 was a prerequisite for PP2A to efficiently dephosphorylate vimentin in vitro or to induce filament reassembly in situ. Both biochemical fractionation and immunofluorescence analysis of detergent-extracted cells revealed that fractions of PP2Ac, PR65, and B55 were tightly associated with vimentin. Furthermore, vimentin-associated PP2A catalytic subunit was displaced in B55-depleted cells. Taken together these data show that, in mammalian fibroblasts, the intermediate filament protein vimentin is dephosphorylated by PP2A, an event targeted by B55.

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32

Seok, Seung-Hyeon. "Structural Insights into Protein Regulation by Phosphorylation and Substrate Recognition of Protein Kinases/Phosphatases". Life 11, n. 9 (13 settembre 2021): 957. http://dx.doi.org/10.3390/life11090957.

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Protein phosphorylation is one of the most widely observed and important post-translational modification (PTM) processes. Protein phosphorylation is regulated by protein kinases, each of which covalently attaches a phosphate group to an amino acid side chain on a serine (Ser), threonine (Thr), or tyrosine (Tyr) residue of a protein, and by protein phosphatases, each of which, conversely, removes a phosphate group from a phosphoprotein. These reversible enzyme activities provide a regulatory mechanism by activating or deactivating many diverse functions of proteins in various cellular processes. In this review, their structures and substrate recognition are described and summarized, focusing on Ser/Thr protein kinases and protein Ser/Thr phosphatases, and the regulation of protein structures by phosphorylation. The studies reviewed here and the resulting information could contribute to further structural, biochemical, and combined studies on the mechanisms of protein phosphorylation and to drug discovery approaches targeting protein kinases or protein phosphatases.

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33

Whalley, T., I. Crossley e M. Whitaker. "Phosphoprotein inhibition of calcium-stimulated exocytosis in sea urchin eggs." Journal of Cell Biology 113, n. 4 (15 maggio 1991): 769–78. http://dx.doi.org/10.1083/jcb.113.4.769.

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We have investigated the role of protein phosphorylation in the control of exocytosis in sea urchin eggs by treating eggs with a thio-analogue of ATP. ATP gamma S (adenosine 5'-O-3-thiotriphosphate) is a compound which can be used as a phosphoryl donor by protein kinases, leading to irreversible protein thiophosphorylation (Gratecos, D., and E.H. Fischer. 1974. Biochem. Biophys. Res. Commun. 58:960-967). Microinjection of ATP gamma S inhibits cortical granule exocytosis, but has no effect on the sperm-egg signal transduction mechanisms which normally cause exocytosis by generating an increase in [Ca2+]i. ATP gamma S requires cytosolic factors for its inhibition of cortical granule exocytosis: it does not affect exocytosis when applied directly to the isolated exocytotic apparatus. Our data suggest that ATP gamma S irreversibly inhibits exocytosis via thiophosphorylation of proteins associated with the egg cortex. We have identified two thiophosphorylated proteins (33 and 27 kD) that are associated with the isolated exocytotic apparatus. They may mediate the inhibition of exocytosis by ATP gamma S. In addition, we show that okadaic acid, an inhibitor of phosphoprotein phosphatases, prevents cortical granule exocytosis at fertilization without affecting calcium mobilization. Like ATP gamma S, okadaic acid has no effect on exocytosis in vitro. Our results suggest that an inhibitory phosphoprotein can obstruct calcium-stimulated exocytosis in sea urchin eggs; on the other hand, they do not readily support the idea that a protein phosphatase is an essential component of the mechanism controlling exocytosis.

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34

Al-Nedawi, K. N., Z. Pawłowska e C. S. Cierniewski. "Interferon gamma bound to endothelial cells is phosphorylated by ecto-protein kinases." Acta Biochimica Polonica 46, n. 3 (30 settembre 1999): 693–702. http://dx.doi.org/10.18388/abp.1999_4141.

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The presence of protein kinase activity and its phosphorylated products has been demonstrated on the outer surface of the plasma membrane of endothelial cells. Extracellular phosphorylation was detected by incubation of primary endothelial cells (HUVEC's) and endothelial cell line EA.hy 926 with [gamma-32P]ATP. The reaction products were subjected to SDS/PAGE, autoradiography and scanning densitometry. Under the experimental conditions, five proteins with apparent molecular masses of 19, 23, 55, 88, and 110 kDa were prominently phosphorylated in both types of cells. Phosphorylation of the 19 kDa protein was the most rapid reaching maximum after 60 s and then the protein became dephosphorylated. Ecto-protein kinases responsible for the surface labeling of membrane proteins were characterized by using (a) protein kinase C inhibitors: K-252b, chelerythrine chloride, and [Ala113] myelin basic protein (104-118), (b) protein kinase A inhibitor Kemptide 8334, and (c) casein kinase II inhibitor 5,6-dichloro-1-beta-D-ribofuranosyl benzimidazole (DRB). Stimulation of endothelial cells with tumor necrosis factor alpha (TNF alpha) and interferon gamma (IFN gamma) is associated with 20-80% reduction of extracellular phosphorylation of all membrane proteins. IFN gamma bound to membrane receptors becomes rapidly phosphorylated. Only in the case of IFN gamma it was associated with the appearance of a strongly phosphorylated band of 17 kDa corresponding to IFN gamma itself. Phosphorylation of this 17 kDa exogenous substrate was prevented by an ecto-kinase inhibitor K-252b. The existence of ecto-phosphoprotein phosphatase activity in endothelial cells was evidenced by testing the effect of microcystin LR--a membrane impermeable reagent that inhibits both PP-1 and PP-2a phosphoprotein phosphatases. The extent of phosphorylation of 19 kDa and 110 kDa phosphoproteins significantly increased in the presence of microcystin. Our results suggest the presence of at least two ecto-kinase activities on endothelial cells that may play a significant role(s) in the regulation of cytokines function.

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35

Comolli, J., W. Taylor, J. Rehman e J. W. Hastings. "Inhibitors of Serine/Threonine Phosphoprotein Phosphatases Alter Circadian Properties in Gonyaulax polyedra". Plant Physiology 111, n. 1 (1 maggio 1996): 285–91. http://dx.doi.org/10.1104/pp.111.1.285.

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36

Macaulay, S. L., Julie D. Newman, J. D. Mc Armstrong e J. Bornstein. "Activation of phosphoprotein phosphatases by growth hormone sequences with insulin-like activity". Molecular and Cellular Biochemistry 74, n. 1 (marzo 1987): 95–101. http://dx.doi.org/10.1007/bf00221916.

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37

Wasserman, Jason S., Felicity Feiser, Seren Palacio, Kishan Patel, Joy Gonzalez, Holly Fowle e Xavier Graña. "Protocol to assess substrate dephosphorylation by serine/threonine phosphoprotein phosphatases in vitro". STAR Protocols 4, n. 2 (giugno 2023): 102148. http://dx.doi.org/10.1016/j.xpro.2023.102148.

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38

Polanowska-Grabowska, Renata, Carl G. Simon, Rocco Falchetto, Jeffrey Shabanowitz, Donald F. Hunt e Adrian R. L. Gear. "Platelet Adhesion to Collagen Under Flow Causes Dissociation of a Phosphoprotein Complex of Heat-Shock Proteins and Protein Phosphatase 1". Blood 90, n. 4 (15 agosto 1997): 1516–26. http://dx.doi.org/10.1182/blood.v90.4.1516.

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Abstract (sommario):

AbstractPhosphorylation/dephosphorylation events in human blood platelets were investigated during their adhesion to collagen under flow conditions. Using 32P-labeled platelets and one-dimensional gel electrophoresis, we found that adhesion to collagen mediated primarily by the α2β1 integrin resulted in a strong dephosphorylation of several protein bands. Neither adhesion to polylysine nor thrombin-induced aggregation caused similar protein dephosphorylation. In addition, treatment with okadaic acid (OA), an inhibitor of serine/threonine protein phosphatases type 1 (PP1) and 2A (PP2A), caused significant inhibition of adhesion, suggesting that adhesion is regulated by OA-sensitive phosphatases. Recent studies indicate that phosphatases may be associated with the heat-shock proteins. Immunoprecipitations with antibodies against either the heat-shock cognate protein 70 (hsc70) or heat-shock protein 90 (hsp90) showed the presence of a phosphoprotein complex in 32P-labeled, resting human platelets. Antibody probing of this complex detected hsc70, hsp90, two isoforms of the catalytic subunit of PP1, PP1Cα and PP1Cδ, as well as the M regulatory subunit of PP1 (PP1M). OA, at concentrations that markedly blocked platelet adhesion to collagen, caused hyperphosphorylation of the hsc70 complex. In platelets adhering to collagen, hsc70 was completely dephosphorylated and hsp90, PP1α, and PP1M were dissociated from the complex, suggesting involvement of heat-shock proteins and protein phosphatases in platelet adhesion.

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39

Polanowska-Grabowska, Renata, Carl G. Simon, Rocco Falchetto, Jeffrey Shabanowitz, Donald F. Hunt e Adrian R. L. Gear. "Platelet Adhesion to Collagen Under Flow Causes Dissociation of a Phosphoprotein Complex of Heat-Shock Proteins and Protein Phosphatase 1". Blood 90, n. 4 (15 agosto 1997): 1516–26. http://dx.doi.org/10.1182/blood.v90.4.1516.1516_1516_1526.

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Abstract (sommario):

Phosphorylation/dephosphorylation events in human blood platelets were investigated during their adhesion to collagen under flow conditions. Using 32P-labeled platelets and one-dimensional gel electrophoresis, we found that adhesion to collagen mediated primarily by the α2β1 integrin resulted in a strong dephosphorylation of several protein bands. Neither adhesion to polylysine nor thrombin-induced aggregation caused similar protein dephosphorylation. In addition, treatment with okadaic acid (OA), an inhibitor of serine/threonine protein phosphatases type 1 (PP1) and 2A (PP2A), caused significant inhibition of adhesion, suggesting that adhesion is regulated by OA-sensitive phosphatases. Recent studies indicate that phosphatases may be associated with the heat-shock proteins. Immunoprecipitations with antibodies against either the heat-shock cognate protein 70 (hsc70) or heat-shock protein 90 (hsp90) showed the presence of a phosphoprotein complex in 32P-labeled, resting human platelets. Antibody probing of this complex detected hsc70, hsp90, two isoforms of the catalytic subunit of PP1, PP1Cα and PP1Cδ, as well as the M regulatory subunit of PP1 (PP1M). OA, at concentrations that markedly blocked platelet adhesion to collagen, caused hyperphosphorylation of the hsc70 complex. In platelets adhering to collagen, hsc70 was completely dephosphorylated and hsp90, PP1α, and PP1M were dissociated from the complex, suggesting involvement of heat-shock proteins and protein phosphatases in platelet adhesion.

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40

Nilsson, Jakob. "Protein phosphatases in the regulation of mitosis". Journal of Cell Biology 218, n. 2 (16 novembre 2018): 395–409. http://dx.doi.org/10.1083/jcb.201809138.

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Abstract (sommario):

The accurate segregation of genetic material to daughter cells during mitosis depends on the precise coordination and regulation of hundreds of proteins by dynamic phosphorylation. Mitotic kinases are major regulators of protein function, but equally important are protein phosphatases that balance their actions, their coordinated activity being essential for accurate chromosome segregation. Phosphoprotein phosphatases (PPPs) that dephosphorylate phosphoserine and phosphothreonine residues are increasingly understood as essential regulators of mitosis. In contrast to kinases, the lack of a pronounced peptide-binding cleft on the catalytic subunit of PPPs suggests that these enzymes are unlikely to be specific. However, recent exciting insights into how mitotic PPPs recognize specific substrates have revealed that they are as specific as kinases. Furthermore, the activities of PPPs are tightly controlled at many levels to ensure that they are active only at the proper time and place. Here, I will discuss substrate selection and regulation of mitotic PPPs focusing mainly on animal cells and explore how these actions control mitosis, as well as important unanswered questions.

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41

Zgajnar, Nadia R., Cristina Daneri-Becerra, Ana Cauerhff e Mario D. Galigniana. "The Scaffold Immunophilin FKBP51 Is a Phosphoprotein That Undergoes Dynamic Mitochondrial-Nuclear Shuttling". Cells 11, n. 23 (25 novembre 2022): 3771. http://dx.doi.org/10.3390/cells11233771.

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The immunophilin FKBP51 forms heterocomplexes with molecular chaperones, protein-kinases, protein-phosphatases, autophagy-related factors, and transcription factors. Like most scaffold proteins, FKBP51 can use a simple tethering mechanism to favor the efficiency of interactions with partner molecules, but it can also exert more complex allosteric controls over client factors, the immunophilin itself being a putative regulation target. One of the simplest strategies for regulating pathways and subcellular localization of proteins is phosphorylation. In this study, it is shown that scaffold immunophilin FKBP51 is resolved by resolutive electrophoresis in various phosphorylated isoforms. This was evidenced by their reactivity with specific anti-phosphoamino acid antibodies and their fade-out by treatment with alkaline phosphatase. Interestingly, stress situations such as exposure to oxidants or in vivo fasting favors FKBP51 translocation from mitochondria to the nucleus. While fasting involves phosphothreonine residues, oxidative stress involves tyrosine residues. Molecular modeling predicts the existence of potential targets located at the FK1 domain of the immunophilin. Thus, oxidative stress favors FKBP51 dephosphorylation and protein degradation by the proteasome, whereas FK506 binding protects the persistence of the post-translational modification in tyrosine, leading to FKBP51 stability under oxidative conditions. Therefore, FKBP51 is revealed as a phosphoprotein that undergoes differential phosphorylations according to the stimulus.

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42

Wagner, Volker, Gunther Geßner, Ines Heiland, Marc Kaminski, Susan Hawat, Kai Scheffler e Maria Mittag. "Analysis of the Phosphoproteome of Chlamydomonas reinhardtii Provides New Insights into Various Cellular Pathways". Eukaryotic Cell 5, n. 3 (marzo 2006): 457–68. http://dx.doi.org/10.1128/ec.5.3.457-468.2006.

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ABSTRACT The unicellular flagellated green alga Chlamydomonas reinhardtii has emerged as a model organism for the study of a variety of cellular processes. Posttranslational control via protein phosphorylation plays a key role in signal transduction, regulation of gene expression, and control of metabolism. Thus, analysis of the phosphoproteome of C. reinhardtii can significantly enhance our understanding of various regulatory pathways. In this study, we have grown C. reinhardtii cultures in the presence of an inhibitor of Ser/Thr phosphatases to increase the phosphoprotein pool. Phosphopeptides from these cells were enriched by immobilized metal-ion affinity chromatography and analyzed by nano-liquid chromatography-electrospray ionization-mass spectrometry (MS) with MS-MS as well as neutral-loss-triggered MS-MS-MS spectra. In this way, we were able to identify 360 phosphopeptides from 328 different phosphoproteins of C. reinhardtii, thus providing new insights into a variety of cellular processes, including metabolic and signaling pathways. Comparative analysis of the phosphoproteome also yielded new functional information on proteins controlled by redox regulation (thioredoxin target proteins) and proteins of the chloroplast 70S ribosome, the centriole, and especially the flagella, for which 32 phosphoproteins were identified. The high yield of phosphoproteins of the latter correlates well with the presence of several flagellar kinases and indicates that phosphorylation/dephosphorylation represents one of the key regulatory mechanisms of eukaryotic cilia. Our data also provide new insights into certain cilium-related mammalian diseases.

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Chen, Lei, Qingling He, Yamin Liu, Yafei Wu, Dongsheng Ni, Jianing Liu, Yanxia Hu et al. "PPP3CB Inhibits Migration of G401 Cells via Regulating Epithelial-to-Mesenchymal Transition and Promotes G401 Cells Growth". International Journal of Molecular Sciences 20, n. 2 (11 gennaio 2019): 275. http://dx.doi.org/10.3390/ijms20020275.

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PPP3CB belongs to the phosphoprotein phosphatases (PPPs) group. Although the majority of the PPP family play important roles in the epithelial-to-mesenchymal transition (EMT) of tumor cells, little is known about the function of PPP3CB in the EMT process. Here, we found PPP3CB had high expression in kidney mesenchymal-like cells compared with kidney epithelial-like cells. Knock-down of PPP3CB downregulated epithelial marker E-cadherin and upregulated mesenchymal marker Vimentin, promoting the transition of cell states from epithelial to mesenchymal and reorganizing the actin cytoskeleton which contributed to cell migration. Conversely, overexpression of PPP3CB reversed EMT and inhibited migration of tumor cells. Besides, in vitro and in vivo experiments indicated that the loss of PPP3CB suppressed the tumor growth. However, the deletion of the phosphatase domain of PPP3CB showed no effect on the expression of E-cadherin, migration, and G401 cell proliferation. Together, we demonstrate that PPP3CB inhibits G401 cell migration through regulating EMT and promotes cell proliferation, which are both associated with the phosphatase activity of PPP3CB.

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Lu, D. J., A. Takai, T. L. Leto e S. Grinstein. "Modulation of neutrophil activation by okadaic acid, a protein phosphatase inhibitor". American Journal of Physiology-Cell Physiology 262, n. 1 (1 gennaio 1992): C39—C49. http://dx.doi.org/10.1152/ajpcell.1992.262.1.c39.

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We determined the effects of okadaic acid (OA), a specific inhibitor of protein phosphatases 1 (PP1) and 2A (PP2A), on protein phosphorylation and on the activation of the NADPH oxidase in human neutrophils. In otherwise unstimulated cells, OA induced phosphoprotein accumulation, revealing the presence of constitutively active protein kinases. Pulse-chase experiments in electropermeabilized cells confirmed that this effect was due, at least in part, to inhibition of dephosphorylation. OA potentiated phosphoprotein accumulation induced by phorbol esters and by the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP). In phorbol ester-stimulated cells, OA prolonged the respiratory response after inhibition of protein kinase C (PKC) with staurosporine, consistent with a reduced rate of dephosphorylation of active phosphorylated components. Similarly, OA delayed the inactivation of the burst after displacement of FMLP from its receptor by a competitive antagonist. This suggests that the substrates of the protein kinases activated by FMLP are dephosphorylated by PP1 and/or PP2A. That phosphatases control the intensity and duration of the respiratory response is suggested by the finding that OA magnified and prolonged the oxidative burst elicited by FMLP. In contrast, pretreatment with OA produced a time-dependent inhibition of the phorbol ester-induced respiratory burst. Under conditions where inhibition of the phorbol ester response was nearly complete, activation by the chemoattractant peptide not only persisted but was in fact accentuated. These findings provide strong evidence that receptor-mediated stimulation of the NADPH oxidase can occur by pathways not involving PKC.

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45

Kochinyan, Samvel, Luo Sun, Inca Ghosh, Tanya Barshevsky, Jie Xu e Ming-Qun Xu. "Use of intein-mediated phosphoprotein arrays to study substrate specificity of protein phosphatases". BioTechniques 42, n. 1 (gennaio 2007): 63–69. http://dx.doi.org/10.2144/000112311.

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46

Lyons, Scott P., Nicole P. Jenkins, Isha Nasa, Meng S. Choy, Mark E. Adamo, Rebecca Page, Wolfgang Peti, Greg B. Moorhead e Arminja N. Kettenbach. "A Quantitative Chemical Proteomic Strategy for Profiling Phosphoprotein Phosphatases from Yeast to Humans". Molecular & Cellular Proteomics 17, n. 12 (18 settembre 2018): 2448–61. http://dx.doi.org/10.1074/mcp.ra118.000822.

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47

Vickroy, Thomas W., Wendi L. Malphurs e Marie L. Carriger. "Regulation of stimulus-dependent hippocampal acetylcholine release by okadaic acid-sensitive phosphoprotein phosphatases". Neuroscience Letters 191, n. 3 (maggio 1995): 200–204. http://dx.doi.org/10.1016/0304-3940(95)11576-i.

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48

Matta, Csaba, Ali Mobasheri, Pál Gergely e Róza Zákány. "Ser/Thr-phosphoprotein phosphatases in chondrogenesis: neglected components of a two-player game". Cellular Signalling 26, n. 10 (ottobre 2014): 2175–85. http://dx.doi.org/10.1016/j.cellsig.2014.06.013.

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49

Nasa, Isha, Lauren E. Cressey, Thomas Kruse, Emil P. T. Hertz, Jiang Gui, Lee M. Graves, Jakob Nilsson e Arminja N. Kettenbach. "Quantitative kinase and phosphatase profiling reveal that CDK1 phosphorylates PP2Ac to promote mitotic entry". Science Signaling 13, n. 648 (8 settembre 2020): eaba7823. http://dx.doi.org/10.1126/scisignal.aba7823.

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Abstract (sommario):

The reciprocal regulation of phosphoprotein phosphatases (PPPs) by protein kinases is essential to cell cycle progression and control, particularly during mitosis for which the role of kinases has been extensively studied. PPPs perform much of the serine/threonine dephosphorylation in eukaryotic cells and achieve substrate selectivity and specificity through the interaction of distinct regulatory subunits with conserved catalytic subunits in holoenzyme complexes. Using a mass spectrometry–based chemical proteomics approach to enrich, identify, and quantify endogenous PPP holoenzyme complexes combined with kinase profiling, we investigated the phosphorylation-dependent regulation of PPP holoenzymes in mitotic cells. We found that cyclin-dependent kinase 1 (CDK1) phosphorylated a threonine residue on the catalytic subunit of the phosphatase PP2A, which disrupted its holoenzyme formation with the regulatory subunit B55. The consequent decrease in the dephosphorylation of PP2A-B55 substrates promoted mitotic entry. This direct phosphorylation by CDK1 was in addition to a previously reported indirect mechanism, thus adding a layer to the interaction between CDK1 and PP2A in regulating mitotic entry.

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Nasa, Isha, e Arminja N. Kettenbach. "Effects of carboxyl-terminal methylation on holoenzyme function of the PP2A subfamily". Biochemical Society Transactions 48, n. 5 (14 ottobre 2020): 2015–27. http://dx.doi.org/10.1042/bst20200177.

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Abstract (sommario):

Phosphoprotein Phosphatases (PPPs) are enzymes highly conserved from yeast and human and catalyze the majority of the serine and threonine dephosphorylation in cells. To achieve substrate specificity and selectivity, PPPs form multimeric holoenzymes consisting of catalytic, structural/scaffolding, and regulatory subunits. For the Protein Phosphatase 2A (PP2A)-subfamily of PPPs, holoenzyme assembly is at least in part regulated by an unusual carboxyl-terminal methyl-esterification, commonly referred to as ‘methylation’. Carboxyl-terminal methylation is catalyzed by Leucine carboxyl methyltransferase-1 (LCMT1) that utilizes S-adenosyl-methionine (SAM) as the methyl donor and removed by protein phosphatase methylesterase 1 (PME1). For PP2A, methylation dictates regulatory subunit selection and thereby downstream phosphorylation signaling. Intriguingly, there are four families of PP2A regulatory subunits, each exhibiting different levels of methylation sensitivity. Thus, changes in PP2A methylation stoichiometry alters the complement of PP2A holoenzymes in cells and creates distinct modes of kinase opposition. Importantly, selective inactivation of PP2A signaling through the deregulation of methylation is observed in several diseases, most prominently Alzheimer's disease (AD). In this review, we focus on how carboxyl-terminal methylation of the PP2A subfamily (PP2A, PP4, and PP6) regulates holoenzyme function and thereby phosphorylation signaling, with an emphasis on AD.

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