scholarly journals Role for protein phosphatases in the cell-cycle-regulated phosphorylation of stathmin

1998 ◽  
Vol 334 (1) ◽  
pp. 23-29 ◽  
Author(s):  
Sucharita J. MISTRY ◽  
Heng-Chun LI ◽  
George F. ATWEH
Keyword(s):  
Cell Cycle ◽  
Okadaic Acid ◽  
Protein Phosphatase ◽  
Protein Phosphatases ◽  
Specific Protein ◽  
G1 Phase ◽  
Major Increase ◽  
Protein Phosphatase Type

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.

Differential expression of protein phosphatase type 1 isotypes and nucleolin during cell cycle arrest

2007 ◽  
Vol 25 (4) ◽  
pp. 369-375 ◽  
Author(s):  
Hiroyuki Morimoto ◽  
Akiko Ozaki ◽  
Hirohiko Okamura ◽  
Kaya Yoshida ◽  
Bruna Rabelo Amorim ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Differential Expression ◽  
Protein Phosphatase ◽  
Cycle Arrest ◽  
Protein Phosphatase Type 1 ◽  
Protein Phosphatase Type

scholarly journals Inhibitory effect of okadaic acid on the p-nitrophenyl phosphate phosphatase activity of protein phosphatases

1991 ◽  
Vol 275 (1) ◽  
pp. 233-239 ◽  
Author(s):  
A Takai ◽  
G Mieskes
Keyword(s):  
Phosphatase Activity ◽  
Okadaic Acid ◽  
Protein Phosphatase ◽  
Protein Phosphatases ◽  
Inhibitory Effect ◽  
Enzyme Concentration ◽  
Alkaline Phosphatases ◽  
Nitrophenyl Phosphate ◽  
Type 1 Phosphatase

The phosphatase activities of type 2A, type 1 and type 2C protein phosphatase preparations were measured against p-nitrophenyl phosphate (pNPP), a commonly used substrate for alkaline phosphatases. Of the three types of phosphatase examined, the type 2A phosphatase exhibited an especially high pNPP phosphatase activity (119 +/- 8 mumol/min per mg of protein; n = 4). This activity was strongly inhibited by pico- to nano-molar concentrations of okadaic acid, a potent inhibitor of type 2A and type 1 protein phosphatases that has been shown to have no effect on alkaline phosphatases. The dose-inhibition relationship was markedly shifted to the right and became steeper by increasing the concentration of the enzyme, as predicted by the kinetic theory for tightly binding inhibitors. The enzyme concentration estimated by titration with okadaic acid agreed well with that calculated from the protein content and the molecular mass for type 2A phosphatase. These results strongly support the idea that the pNPP phosphatase activity is intrinsic to type 2A protein phosphatase and is not due to contamination by alkaline phosphatases. pNPP was also dephosphorylated, but at much lower rates, by type 1 phosphatase (6.4 +/- 8 nmol/min per mg of protein; n = 4) and type 2C phosphatase (1.2 +/- 3 nmol/min per mg of protein; n = 4). The pNPP phosphatase activity of the type 1 phosphatase preparation shows a susceptibility to okadaic acid similar to that of its protein phosphatase activity, whereas it was interestingly very resistant to inhibitor 2, an endogenous inhibitory factor of type 1 protein phosphatase. The pNPP phosphatase activity of type 2C phosphatase preparation was not affected by up to 10 microM-okadaic acid.

24. Protein phosphatase type 1 and cell cycle arrest in mouse osteoblastic cells

1999 ◽  
Vol 53 (6) ◽  
pp. 735-736
Author(s):  
Hiroyuki Morimoto ◽  
Nobuaki Nakamuta ◽  
Kimiko Nomiyama ◽  
Shigeru Kobayashi ◽  
Tatsuji Haneji
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Protein Phosphatase ◽  
Osteoblastic Cells ◽  
Cycle Arrest ◽  
Protein Phosphatase Type 1 ◽  
Protein Phosphatase Type

The protein phosphatase inhibitor okadaic acid induces defects in cytokinesis and organellar genome segregation in Trypanosoma brucei

1994 ◽  
Vol 107 (12) ◽  
pp. 3477-3483 ◽  
Author(s):  
A. Das ◽  
M. Gale ◽  
V. Carter ◽  
M. Parsons
Keyword(s):  
Cell Cycle ◽  
Mitochondrial Dna ◽  
Okadaic Acid ◽  
Protein Phosphatase ◽  
Specific Inhibitor ◽  
Eukaryotic Cell ◽  
Cell Cycles ◽  
African Trypanosomes ◽  
20 Nm

Mitosis and cytokinesis are events that are highly coordinated in most eukaryotic cell cycles. African trypanosomes possess a single mitochondrion and must additionally coordinate the organellar division cycle. Here we report that okadaic acid, a potent and specific inhibitor of protein phosphatases PP1and PP2A, uncouples these cycles in living trypanosomes. Cell cycle analysis of treated cells revealed elevated DNA content. Microscopic examination indicated that okadaic acid treatment yielded multinucleate cells with a single mitochondrial network indicating these cells have undergone mitosis but failed to complete cytokinesis. Immunofluorescence analysis of 5-bromo-2-deoxyuridine incorporation demonstrated that the mitochondrial DNA was replicated but did not segregate. The dose response curve for inhibition of the normal cell cycle paralleled that for the in vitro inhibition of protein phosphatase activities with IC50s of approximately 20 nM okadaic acid. These results suggest the involvement of a PP1/PP2A-like activity in coordinating mitosis, mitochondrial DNA division and cytokinesis in trypanosomes.

scholarly journals Regulation of acrosome reaction of fowl spermatozoa: evidence for the involvement of protein kinase C and protein phosphatase-type 1 and/or -type 2A

Reproduction ◽  
2006 ◽  
Vol 131 (6) ◽  
pp. 1017-1024 ◽  
Author(s):  
K Ashizawa ◽  
G J Wishart ◽  
S Katayama ◽  
D Takano ◽  
A R A H Ranasinghe ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Okadaic Acid ◽  
Protein Phosphatase ◽  
Acrosome Reaction ◽  
Dependent Manner ◽  
Kinase C ◽  
Protein Phosphatase Type 1 ◽  
Protein Phosphatase Type

The signal transduction pathways involved in the regulation of the acrosome reaction and motility of fowl spermatozoa were investigated. The motility and acrosomal integrity of fowl spermatozoa in TES/NaCl buffer, with or without homogenised inner perivitelline layers (IPVL), prepared from laid fowl eggs, was almost negligible at 40 °C. In the presence of 2 mmol CaCl2/l at 40 °C, motility became vigorous and the acrosome reaction was stimulated when IPVL was added. In the absence of Ca2+, motility was stimulated by the addition of calyculin A and okadaic acid, both specific inhibitors of protein phosphatase-type 1 (PP1) and -type 2A (PP2A), but Okadaic acid, which is a weaker inhibitor of PP1, did not completely restore motility at 40 °C. However, the acrosome reaction was significantly and equally stimulated in a dose-dependent manner by both inhibitors in the range of 10–1000 nmol/l, when spermatozoa were incubated with IPVL but without Ca2+. These inhibitors did not stimulate the acrosome reaction in the absence of IPVL. The vigorous motility of spermatozoa, stimulated by the addition of Ca2+, was reduced gradually as the concentrations of SC-9, a selective activator of protein kinase C (PKC), were increased and a similar SC-9-induced inhibition was observed in the acrosome reaction in the presence of Ca2+ and IPVL. These results confirm that IPVL is necessary for the activation of the acrosome reaction in fowl spermatozoa and that Ca2+ plays an important role in the stimulation of motility and acrosomal exocytosis. Furthermore, it appears that the intracellular molecular mechanisms for the regulation of acrosome reaction of fowl spermatozoa are different from those for the restoration of motility, i.e., protein dephosporylation involving PP1 and/or PP2A in the former, and PP1 alone in the latter case. In addition, the activation of PKC may contribute to a decrease in the flagellar movement and acrosome reaction of fowl spermatozoa.

scholarly journals Reconstruction of spatial structure of plant protein phosphatase type 1, 2a and 4 in complexes with microcystin-LR

1970 ◽  
pp. 339-344
Author(s):  
D. A. Samofalova ◽  
P. A. Karpov ◽  
O. V. Raievskyi ◽  
Ya. B. Blume
Keyword(s):  
Molecular Docking ◽  
Spatial Structure ◽  
Protein Phosphatase ◽  
Protein Phosphatases ◽  
Specific Interaction ◽  
Specific Protein ◽  
Plant Protein ◽  
Scoring Functions ◽  
High Level

Aim. The major toxicity of Microcystin-LR (MCLR) has been ascribed to its potent ability to inhibit serine/threonine-specific protein phosphatase 1 (PP1) and protein phosphatase 2A (PP2A). Although MCLR is widely used in animal models its selectivity for these enzymes of plant origin is not still investigated in details for phylogenetically diversified sources. Methods. The spatial structure of plant PP1, PP2A, PP4 protein phosphatases was reconstructed with homology modeling method. Flexible docking of MCLR was performed using CCDC GOLD Suite 5.3. For docking evaluations, GOLD scoring functions were used. Results. Information about amino acids, involved in ligand binding, was obtained from 8 experimentally proved human MCLR-PP1 and PP2A complexes. The sites of microcystin-LR binding with plant protein phosphatases (type-1, 2A and 4) were proved by comparative analysis and molecular docking. A high level of sequence and structure identity of plant and animal phosphatases allow us to conclude similarity of MCLR binding in PP1, PP2A and PP4. Keywords: microcystin-LR, protein phosphatase, specific interaction, molecular docking.

scholarly journals Functional interaction between nuclear inhibitor of protein phosphatase type 1 (NIPP1) and protein phosphatase type 1 (PP1) in Drosophila: consequences of over-expression of NIPP1 in flies and suppression by co-expression of PP1

2002 ◽  
Vol 368 (3) ◽  
pp. 789-797 ◽  
Author(s):  
Louise PARKER ◽  
Sascha GROSS ◽  
Monique BEULLENS ◽  
Mathieu BOLLEN ◽  
Daimark BENNETT ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Developmental Stages ◽  
Physiological Effect ◽  
Nuclear Speckles ◽  
Over Expression ◽  
Protein Phosphatase Type 1 ◽  
Protein Phosphatase Type

The catalytic subunit of type 1 Ser/Thr protein phosphatases (PP1c) forms complexes with many proteins that target it to particular subcellular locations and regulate its activity towards specific substrates. We report the identification of a Drosophila orthologue of nuclear inhibitor of PP1 (NIPP1Dm) through interaction with PP1c in the yeast two-hybrid system. NIPP1Dm shares many properties with mammalian NIPP1 including inhibition of PP1c in vitro, binding to RNA and PP1c, and localization to nuclear speckles. However, the mechanism controlling interaction of PP1c with NIPP1 is not conserved in Drosophila. NIPP1 can function independently of PP1c as a splicing factor, but the relative importance of this function is unknown. Over-expression of NIPP1Dm in Drosophila is cell-lethal in a range of tissues and developmental stages. The effects of ectopic NIPP1Dm are suppressed by co-expression of PP1c, indicating that the only effect of ectopic NIPP1Dm is to affect PP1c function. Co-expression of NIPP1Dm and PP1c does not have any detectable physiological effect in vivo, suggesting that the NIPP1Dm—PP1c holoenzyme is not normally limiting in Drosophila. These data show that NIPP1Dm and PP1c interact in vivo and suggest that NIPP1's role as a phosphatase regulator is conserved in Drosophila.

scholarly journals Characterization of Schistosoma mansoni Sds homologue, a leucine-rich repeat protein that interacts with protein phosphatase type 1 and interrupts a G2/M cell-cycle checkpoint

2006 ◽  
Vol 395 (2) ◽  
pp. 433-441 ◽  
Author(s):  
Wassim Daher ◽  
Katia Cailliau ◽  
Kojiro Takeda ◽  
Christine Pierrot ◽  
Naji Khayath ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Schistosoma Mansoni ◽  
Protein Phosphatase ◽  
Cell Cycle Checkpoint ◽  
M Cell ◽  
Germinal Vesicle Breakdown ◽  
Protein Phosphatase Type 1 ◽  
Cycle Checkpoint ◽  
Protein Phosphatase Type

The suppressor of the dis2 mutant (sds22+) has been shown to be an essential regulator in cell division of fission and budding yeast where its deletion causes mitotic arrest. Its role seems to take place through the activation of PP1 (protein phosphatase type 1) in Schizosaccharomyces pombe. In the trematode Schistosoma mansoni, we have identified the Sds22 homologue (SmSds), and the PP1 (SmPP1). We showed by using a GST (glutathione S-transferase) pull-down assay that the SmSds gene product interacts with SmPP1 and that the SmSds–SmPP1 complex is present in parasite extracts. Furthermore, we observed that SmSds inhibited PP1 activity. Functional studies showed that the microinjection of SmSds into Xenopus oocytes interacted with the Xenopus PP1 and disrupted the G2/M cell-cycle checkpoint by promoting progression to GVBD (germinal vesicle breakdown). Similar results showing the appearance of GVBD were observed when oocytes were treated with anti-PP1 antibodies. Taken together, these observations suggest that SmSds can regulate the cell cycle by binding to PP1.

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