Reconstitution of calyculin-inhibited K-Cl cotransport in dog erythrocyte ghosts by exogenous PP-1

1996 ◽  
Vol 270 (3) ◽  
pp. C898-C902 ◽  
Author(s):  
T. Krarup ◽  
P. B. Dunham
Keyword(s):  
Protein Phosphatase ◽  
Direct Evidence ◽  
Potent Inhibitor ◽  
Protein Phosphatases ◽  
Calyculin A ◽  
Osmotic Swelling ◽  
Maximal Activation ◽  
Resealed Ghosts ◽  
K Transport

Osmotic swelling of dog and other mammalian erythrocytes activates Cl-dependent K transport, K-Cl cotransport. This activation can be abolished by nanomolar concentrations of calyculin, a potent inhibitor of serine-threonine protein phosphatases. Therefore, K-Cl cotransport is probably activated by dephosphorylation by a type 1 and/or type 2A protein phosphatase (PP-1 and PP-2A, respectively). This was tested directly by incorporating exogenous protein phosphatases into resealed ghosts made from dog erythrocytes previously exposed to calyculin. K-Cl cotransport was nearly completely inhibited in the ghosts. Incorporation of PP-1 reconstituted K-Cl cotransport. Maximal reconstitution was up to 90% of the control flux in the ghosts and 0.1 U PP-1/ml lysate gave half-maximal reconstitution of cotransport. In contrast, PP-2A had no effect. This result with PP-1 provides direct evidence that K-Cl cotransport is activated by PP-1 in dog erythrocytes. Half-maximal activation of K-Cl cotransport required approximately 180 molecules of PP-1 per ghost.

scholarly journals Identification of Novel Serine/Threonine Protein Phosphatases inTrypanosoma cruzi: a Potential Role in Control of Cytokinesis and Morphology

2000 ◽  
Vol 68 (3) ◽  
pp. 1350-1358 ◽  
Author(s):  
George A. Orr ◽  
Craig Werner ◽  
Jun Xu ◽  
Marcia Bennett ◽  
Louis M. Weiss ◽  
...  
Keyword(s):  
Cell Division ◽  
Okadaic Acid ◽  
Blot Analysis ◽  
Protein Phosphatase ◽  
Protein Phosphatases ◽  
Growth Arrest ◽  
Human Protein ◽  
Protein Phosphatase 1 ◽  
Calyculin A ◽  
Metacyclic Trypomastigote

ABSTRACT We cloned two novel Trypanosoma cruzi proteins by using degenerate oligonucleotide primers prepared against conserved domains in mammalian serine/threonine protein phosphatases 1, 2A, and 2B. The isolated genes encoded proteins of 323 and 330 amino acids, respectively, that were more homologous to the catalytic subunit of human protein phosphatase 1 than to those of human protein phosphatase 2A or 2B. The proteins encoded by these genes have been tentatively designated TcPP1α and TcPP1β. Northern blot analysis revealed the presence of a major 2.3-kb mRNA transcript hybridizing to each gene in both the epimastigote and metacyclic trypomastigote developmental stages. Southern blot analysis suggests that each protein phosphatase 1 gene is present as a single copy in the T. cruzi genome. The complete coding region for TcPP1β was expressed inEscherichia coli by using a vector, pTACTAC, with thetrp-lac hybrid promoter. The recombinant protein from the TcPP1β construct displayed phosphatase activity toward phosphorylasea, and this activity was preferentially inhibited by calyculin A (50% inhibitory concentration [IC50], ∼2 nM) over okadaic acid (IC50, ∼100 nM). Calyculin A, but not okadaic acid, had profound effects on the in vitro replication and morphology of T. cruzi epimastigotes. Low concentrations of calyculin A (1 to 10 nM) caused growth arrest. Electron microscopic studies of the calyculin A-treated epimastigotes revealed that the organisms underwent duplication of organelles, including the flagellum, kinetoplast, and nucleus, but were incapable of completing cell division. At concentrations higher than 10 nM, or upon prolonged incubation at lower concentrations, the epimastigotes lost their characteristic elongated spindle shape and had a more rounded morphology. Okadaic acid at concentrations up to 1 μM did not result in growth arrest or morphological alterations to T. cruziepimastigotes. Calyculin A, but not okadaic acid, was also a potent inhibitor of the dephosphorylation of 32P-labeled phosphorylase a by T. cruzi epimastigotes and metacyclic trypomastigote extracts. These inhibitor studies suggest that in T. cruzi, type 1 protein phosphatases are important for the completion of cell division and for the maintenance of cell shape.

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.

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 Blocking Protein Phosphatase 1 [PP1] Prevents Loss of Tether Elasticity in Anaphase Crane-Fly Spermatocytes

2021 ◽  
Vol 8 ◽  
Author(s):  
Arthur Forer ◽  
Aisha Adil ◽  
Michael W. Berns
Keyword(s):  
Protein Phosphatase ◽  
Chromosome Pair ◽  
Protein Phosphatases ◽  
Protein Phosphatase 1 ◽  
Calyculin A ◽  
Early Anaphase ◽  
In Cells

In normal anaphase cells, telomeres of each separating chromosome pair are connected to each other by tethers. Tethers are elastic at the start of anaphase: arm fragments cut from anaphase chromosomes in early anaphase move across the equator to the oppositely-moving chromosome, telomere moving toward telomere. Tethers become inelastic later in anaphase as the tethers become longer: arm fragments no longer move to their partners. When early anaphase cells are treated with Calyculin A (CalA), an inhibitor of protein phosphatases 1 (PP1) and 2A (PP2A), at the end of anaphase chromosomes move backward from the poles, with telomeres moving toward partner telomeres. Experiments described herein show that in cells treated with CalA, backwards movements are stopped in a variety of ways, by cutting the tethers of backwards moving chromosomes, by severing arms of backwards moving chromosomes, by severing arms before the chromosomes reach the poles, and by cutting the telomere toward which a chromosome is moving backwards. Measurements of arm-fragment velocities show that CalA prevents tethers from becoming inelastic as they lengthen. Since treatment with CalA causes tethers to remain elastic throughout anaphase and since inhibitors of PP2A do not cause the backwards movements, PP1 activity during anaphase causes the tethers to become inelastic.

scholarly journals The Usefulness of Calyculin A for Cytogenetic Prenatal Diagnosis

2005 ◽  
Vol 53 (3) ◽  
pp. 391-394 ◽  
Author(s):  
Malgorzata I. Srebniak ◽  
Gizela G. Trapp ◽  
Angelika K. Wawrzkiewicz ◽  
Wojciech Kaźmierczak ◽  
Andrzej K. Wiczkowski
Keyword(s):  
Cell Cycle ◽  
Prenatal Diagnosis ◽  
Amniotic Fluid ◽  
Protein Phosphatases ◽  
Genetic Material ◽  
Chromosome Condensation ◽  
Calyculin A ◽  
Premature Chromosome Condensation ◽  
Chromosomal Breaks

An increased number of chromosome plates can be obtained by use of calyculin A (CLA). CLA is an inhibitor of protein phosphatases (type 1 and type 2A serine/threonine). Inactivation of these phosphatases leads to premature chromosome condensation (PCC) in all phases of the cell cycle; thus, it is possible to investigate both metaphase and G2-PCC chromosomes. Amniotic fluid (AF) cultures were treated with calyculin A (CLA). GTG banding was obtained. Using this method it is possible to investigate all cell cycle phases, GTG banding, chromosomal breaks, and rates of PCD on the same preparation. Analyses of AF cultures treated with CLA allow complex studies on fetal genetic material. This work presents potential usefulness of CLA for cytogenetic prenatal diagnosis.

scholarly journals The protein phosphatase inhibitor calyculin A stimulates chemokine production by human synovial cells

1995 ◽  
Vol 311 (1) ◽  
pp. 89-95 ◽  
Author(s):  
N J Jordan ◽  
M L Watson ◽  
J Westwick
Keyword(s):  
Gene Expression ◽  
Mrna Expression ◽  
Protein Phosphatase ◽  
Synovial Fibroblasts ◽  
Tnf Alpha ◽  
Synovial Cells ◽  
Calyculin A ◽  
Chemokine Gene ◽  
Chemokine Gene Expression

Cultured human synovial fibroblasts express mRNA for the chemotactic cytokines (chemokines) interleukin-8 (IL-8), monocyte chemotactic protein 1 (MCP-1) and regulated upon activation normal T-cell expressed and presumably secreted (RANTES), when stimulated with IL-1 or tumour necrosis factor alpha (TNF alpha). Calyculin A, a potent type 1/2A protein serine/threonine phosphatase inhibitor, was used to examine the role of protein phosphatases in the regulation of chemokine gene expression. Calyculin A (1 nM) mimicked IL-1 by inducing IL-8 and MCP-1 mRNA expression in synovial cells. IL-8 mRNA was induced over a similar time period (1-6 h) in response to IL-1 or calyculin A, whereas MCP-1 mRNA was induced more rapidly (1-2 h) by calyculin A than by IL-1 (4-6 h). Expression of RANTES mRNA occurred in response to TNF alpha, but could not be induced by stimulation with calyculin A alone. These results suggest that inhibition of protein phosphatase type 1/2A may have a differential role in the regulation of the expression of each of the chemokine genes. Synovial fibroblasts also secreted IL-8 and IL-6 peptide when stimulated with either IL-1/TNF alpha or calyculin A. The amount of IL-8 and IL-6 peptide produced in response to calyculin A was significantly increased above that produced by untreated synovial cells, though it was much less than the amount induced by IL-1 or TNF alpha. Calyculin A also acted synergistically with IL-1 or TNF alpha to cause a 2-fold potentiation of IL-1- or TNF alpha-induced IL-8 mRNA and peptide and RANTES mRNA expression. These results suggest that although inhibition of a protein phosphatase may be able to regulate the magnitude of IL-1-induced chemokine gene expression, the IL-1 signal transduction pathway involves components in addition to phosphatase inhibition, possibly including the activation of a protein kinase, the action of which may be opposed by a protein phosphatase inhibited by calyculin A.

K-Cl cotransport in rabbit red cells: further evidence for regulation by protein phosphatase type 1

1993 ◽  
Vol 264 (1) ◽  
pp. C118-C124 ◽  
Author(s):  
L. C. Starke ◽  
M. L. Jennings
Keyword(s):  
Okadaic Acid ◽  
Protein Phosphatase ◽  
Inhibitory Concentration ◽  
Cell Swelling ◽  
Calyculin A ◽  
Phosphatase Inhibitor ◽  
Protein Phosphatase Type 1 ◽  
Pharmacological Studies ◽  
Protein Phosphatase Type

We have examined inhibition of swelling-induced K-Cl cotransport in rabbit red blood cells by calyculin A, a potent serine-threonine protein phosphatase inhibitor, to determine whether transport is regulated by phosphatase type 1 or type 2A. Calyculin A blocks K(Rb) influx [half-maximal inhibitory concentration (IC50) = 3-6 nM] 10 times more potently than a second phosphatase inhibitor, okadaic acid (IC50 = 40 nM), consistent with earlier pharmacological studies showing that calyculin A inhibits phosphatase type 1 10 times more effectively than does okadaic acid. Calyculin A always inhibits Rb influx when added either before or after cell swelling, indicating that the phosphatase must operate continually to first activate and then maintain high transport rates in swollen cells. Similarly, N-ethylmaleimide (NEM) fails to stimulate K-Cl cotransport only when added to cells pretreated with calyculin A. Therefore, like cell swelling, activation of K-Cl cotransport by NEM involves a phosphatase sensitive to calyculin A. We conclude that cell swelling and NEM activate K-Cl cotransport via a net dephosphorylation that appears to involve protein phosphatase type 1.

scholarly journals Characterization of microcystin-LR, a potent inhibitor of type 1 and type 2A protein phosphatases.

1990 ◽  
Vol 265 (32) ◽  
pp. 19401-19404 ◽  
Author(s):  
R E Honkanen ◽  
J Zwiller ◽  
R E Moore ◽  
S L Daily ◽  
B S Khatra ◽  
...  
Keyword(s):  
Potent Inhibitor ◽  
Protein Phosphatases

Serine/threonine protein phosphatases and regulation of K-Cl cotransport in human erythrocytes

1999 ◽  
Vol 277 (5) ◽  
pp. C926-C936 ◽  
Author(s):  
Isabel Bize ◽  
Birol Güvenç ◽  
Aeisha Robb ◽  
Guido Buchbinder ◽  
Carlo Brugnara
Keyword(s):  
Ionic Strength ◽  
Protein Phosphatase ◽  
Protein Phosphatases ◽  
Human Erythrocytes ◽  
Phosphatase Inhibitors ◽  
Pp2a Activity ◽  
Highly Sensitive ◽  
Protein Phosphatase Inhibitors ◽  
Membrane Bound

Activation of K-Cl cotransport is associated with activation of membrane-bound serine/threonine protein phosphatases (S/T-PPases). We characterize red blood cell S/T-PPases and K-Cl cotransport activity regarding protein phosphatase inhibitors and response to changes in ionic strength and cell size. Protein phosphatase type 1 (PP1) activity is highly sensitive to calyculin A (CalA) but not to okadaic acid (OA). PP2A activity is highly sensitive to CalA and OA. CalA completely inhibits K-Cl cotransport activity, whereas OA partially inhibits K-Cl cotransport. Membrane PP1 and membrane PP2A activities are elevated in cells suspended in hypotonic solutions, where K-Cl cotransport is elevated. Increases in membrane PP1 activity (62 ± 10% per 100 meq/l) result from decreases in intracellular ionic strength and correlate with increases in K-Cl cotransport activity (54 ± 10% per 100 meq/l). Increases in membrane PP2A activity (270 ± 77% per 100 mosM) result from volume increases and also correlate with increases in K-Cl cotransport activity (420 ± 47% per 100 mosM). The characteristics of membrane-associated PP1 and PP2A are consistent with a role for both phosphatases in K-Cl cotransport activation in human erythrocytes.

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.

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