Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.3.16 (calcineurin)
 17,112 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The phosphorylation of the Hsp27 complex is rapidly altered in MRC-5 cells when they are exposed to mitogens, cytokines, stress, or serine/threonine protein phosphatase inhibitors. Here we performed experiments to identify which cellular protein phosphatase (PP1, PP2A, or PP2B) is responsible for the in vivo phosphorylation/dephosphorylation of Hsp27. In their purified forms, PP2A dephosphorylates Hsp27 more effectively than PP2B, whereas PP1 is weakly active. Measurements of enzyme activity of lysates derived from inhibitor-treated cells indicated that Hsp27 phosphatase activity is equally sensitive to okadaic acid (PPI/PP2A inhibitor) and cyclosporin (PP2B inhibitor) and that both okadaic acid and cyclosporin treatment inhibited Hsp27 phosphatase activity additively. Together the in vitro data suggest that both PP2A and PP2B can dephosphorylate Hsp27. However, the phosphorylation of Hsp27 in vivo is only affected when cells are treated with PP1 and PP2A inhibitors (okadaic acid, calyculin A) or cantharidin (PP2A inhibitor), but not the PP2B inhibitor, cyclosporin A, suggesting PP2A to be the main enzyme dephosphorylating Hsp27 in the cells. Purification and immunoblotting of Hsp27 phosphatase from MRC-5 cells also suggest it to be PP2A and not PP1 or PP2B. The ability of PP2A to dephosphorylate Hsp27 is shown to be regulated by the phosphorylation state of PP2A itself.
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PMID:Dephosphorylation of the small heat shock protein Hsp27 in vivo by protein phosphatase 2A. 751 Jul 4

Inhibitors of phosphotyrosyl protein phosphatases, pervanadate and phenylarsine oxide, abrogate tumor necrosis factor (TNF)-induced nuclear factor kappa B (NF-kappa B) nuclear translocation in transformed cell lines (U-937 and Jurkat) and primary fibroblasts (MRC-5 and REF). The inhibitors also abrogate NF-kappa B activation by the phosphoseryl/threonyl protein phosphatase inhibitor okadaic acid in U-937 cells. Inhibition of NF-kappa B activation is not due to a general inhibitory effect since neither pervanadate nor phenylarsine oxide treatment affected the constitutive DNA-binding activity of the transcription factors octamer-1 and cAMP response element-binding protein in U-937 cells, nor did these compounds inhibit the TNF-induced phosphorylation of proteins, viz. hsp-27, eukaryotic initiation factor 4e, and pp19, in MRC-5 fibroblasts. Overexpression of the protein-tyrosine phosphatase HPTP alpha resulted in a constitutive nuclear NF-kappa B-like DNA-binding activity in REF cells. Conversely, treatment of human protein-tyrosine phosphatase alpha-overexpressing cells with phenylarsine oxide led to a loss of the constitutive NF-kappa B activity. The presence of a tyrosine phosphorylation site on the inhibitor of NF-kappa B (I kappa B-alpha) suggested that it could be a target for TNF/okadaic acid-induced tyrosine dephosphorylation. However, no tyrosine phosphorylation was detected on I kappa B-alpha fron unstimulated cells, while TNF/okadaic acid-treated cells showed increased phosphorylation of I kappa B-alpha exclusively at serine residue(s). Treatment of cells with pervanadate inhibited TNF-induced I kappa B-alpha phosphorylation and degradation, whereas the serine protease inhibitors tosylphenylalanyl chloromethyl ketone and N alpha-p-tosyl-L-lysine chloromethyl ketone prevented TNF-induced I kappa B-alpha degradation and NF-kappa B nuclear translocation, but not the TNF-induced phosphorylation of I kappa B-alpha. The data suggest that TNF and okadaic acid induce the activation of a putative protein-tyrosine phosphatase(s), leading to I kappa B-alpha serine phosphorylation and degradation and NF-kappa B nuclear translocation.
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PMID:Involvement of a putative protein-tyrosine phosphatase and I kappa B-alpha serine phosphorylation in nuclear factor kappa B activation by tumor necrosis factor. 764 44

In this study, we examined whether the production of hepatocyte growth factor (HGF) in fibroblasts is regulated by protein phosphatase(s). Inhibitors of the enzymes okadaic acid and calyculin A were used for this purpose. Both inhibitors markedly stimulated HGF production in human skin fibroblasts in a dose-dependent manner. The effects of okadaic acid and calyculin A were maximal at 25-37.5 and 1.25 nM, respectively. Highly active HGF production in MRC-5 human embryonic lung fibroblasts was also promoted by both inhibitors. The effect of okadaic acid was accompanied by an up-regulation of HGF gene expression. The stimulating effect of okadaic acid on HGF production was synergistic with that of phorbol 12-myristate 13-acetate (PMA) and epidermal growth factor (EGF), whereas it was additive to the effect of cholera toxin. The protein kinase C (PKC) inhibitor GF 109203X inhibited the effect of PMA, but not of okadaic acid and EGF. The effect of okadaic acid as well as EGF was not inhibited, but rather enhanced in human skin fibroblasts pretreated for 24 hr with a high dose of PMA to deplete PKC, as compared with its effect in untreated cells. PD 98059, an inhibitor of mitogen-activated protein (MAP) kinase kinase, suppressed the effects of okadaic acid and EGF, but not those of cholera toxin and 8-bromo-adenosine 3',5'-cyclic monophosphate (cAMP). These results suggest that HGF production in human skin fibroblasts is down-regulated by protein phosphatase(s) and that HGF production stimulated by okadaic acid is, at least in part, dependent on the activation of the MAP kinase cascade.
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PMID:Stimulation of hepatocyte growth factor production in human fibroblasts by the protein phosphatase inhibitor okadaic acid. 1102 Apr 56

Phosphorylation of histone H2AX at serine 139 (gamma-H2AX) represents one of the earliest steps in DNA DSB signaling and repair, but the mechanisms of coupling this histone modification to DSB processing remain to be established. In this work, H2AX phosphorylation-dephosphorylation kinetics induced by low doses of gamma rays in MRC-5 human fibroblasts was studied. The number of gamma-H2AX foci increased rapidly, with the maximum reached 20 min after irradiation. Using calyculin A, a protein phosphatase inhibitor, no significant dephosphorylation was found in this time. At longer times, no further induction of gamma-H2AX foci occurred. This indicates that the number of gamma-H2AX foci scored at 20 min can be used as representative of the initial number of DSBs. Pulsed-field gel electrophoresis (PFGE) was also used to determine whether calyculin A-mediated inhibition of gamma-H2AX dephosphorylation and DSB rejoining are independent phenomena. We found that the maintenance of the phosphate group at Ser 139 in gamma-H2AX does not represent an obstacle for DSB rejoining. Preliminary experiments performed with 62 MeV/nucleon carbon ions have shown a longer persistence of gamma-H2AX foci with respect to gamma rays, consistent with the induction of damage that is more severe and difficult to repair.
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PMID:Induction and repair of DNA double-strand breaks in human cells: dephosphorylation of histone H2AX and its inhibition by calyculin A. 1618 59