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

We investigated the effects of the protein phosphatase inhibitors okadaic acid and microcystin-LR upon transport of newly synthesized proteins through the exocytic pathway. Treatment of CHO cells with 1 microM okadaic acid rapidly inhibited movement of a marker protein (vesicular stomatitis virus G protein) from the endoplasmic reticulum to the Golgi compartment. Both okadaic acid and microcystin-LR also inhibited transport in an in vitro assay reconstituting movement to the Golgi compartment, at concentrations equivalent to those required to inhibit phosphorylase phosphatase activity. Inhibition both in vivo and in vitro could be antagonized by protein kinase inhibitors, suggesting that protein phosphorylation was directly responsible for this effect. An early stage in the transport reaction associated with vesicle formation or targeting was inhibited by protein phosphorylation, which could be reversed by fractions enriched in protein phosphatase 2A. Protein kinase antagonists did not inhibit transport between sequential compartments of the exocytic pathway in vitro, suggesting that protein phosphorylation is not itself required for vesicular transport. During mitosis, vesicular transport is inhibited simultaneous to the activation of maturation-promoting factor. It is proposed that the inhibition caused by okadaic acid and microcystin-LR involves a similar mechanism to that responsible for the mitotic arrest of vesicular transport.
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PMID:Evidence for the regulation of exocytic transport by protein phosphorylation. 131 11

Two antipeptide antibodies (designated type 1 antibody and type 2A antibody) were raised against synthetic peptides, Cys-Thr-Pro-Pro-Arg-Asn-Ser-Ala-Lys-Ala-Lys-Lys and Cys-Val-Thr-Arg-Arg-Thr-Pro-Asp-Try-Phe-Leu, corresponding to the carboxyl termini of the catalytic subunits of protein phosphatase 1 and phosphatase 2A (Cys was added for specific coupling to carrier protein). These antipeptide antibodies were highly specific and were useful in discriminating between protein phosphatase 1 and phosphatase 2A in crude extracts or purified preparations. Type 2A antibody reacted with both native and denatured protein phosphatase 2A whereas under the same condition type 1 antibody reacted only with denatured protein phosphatase 1.
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PMID:Antibodies directed against synthetic peptides distinguish between the catalytic subunits of protein phosphatases 1 and 2A. 131 44

The relative potencies of four main types of okadaic acid class compounds as inhibitors of the catalytic subunits of protein serine/threonine phosphatases 1 and 2A and the protein tyrosine phosphatase 1 were determined. These four types of compounds are okadaic acid, calyculin A, microcystin-LR, and tautomycin, which are isolated from different natural sources, a black sponge Halichondria okadai, a marine sponge Discodermia calyx, a blue-green alga Microcystis aeruginosa, and Streptomyces spirover ticillatus, respectively. While okadaic acid was a more effective inhibitor of protein phosphatase 2A (IC50, 0.07 nM) than protein phosphatase 1 (IC50, 3.4 nM), other compounds of the okadaic acid class were equally effective against the two protein serine/threonine phosphatases. The order of potency was microcystin greater than calyculin A greater than tautomycin, and the IC50S ranged from 0.1 to 0.7 nM. None of the okadaic acid class compounds inhibited protein tyrosine phosphatase 1 activity at concentrations up to 0.01 mM. These results indicate that the compounds of the okadaic acid class are selective inhibitors of protein serine/threonine but not tyrosine phosphatases.
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PMID:Structurally different members of the okadaic acid class selectively inhibit protein serine/threonine but not tyrosine phosphatase activity. 132 38

A method has been developed for measuring specific protein phosphatase activity in biological samples using synthetic, phospho-Kemptide and phospho-GS-peptide. This method uses ion-exchange chromatography to determine phosphatase activity by quantifying the release of [32P]phosphate directly. The method was used to measure phosphatase activity of rat kidney, adrenals, heart, and liver cytosol and the activity of purified alkaline phosphatases, protein phosphatase 1, and protein phosphatase 2A. Ion-exchange chromatography was also used for the preparation of the radiolabeled phosphopeptide substrates. This method results in high recovery and specific activity of the labeled peptides. These techniques should be useful in isolating and characterizing specific protein phosphatases found in cells.
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PMID:Measurement of protein phosphatase activity in biological samples using synthetic phosphopeptides. 132 21

Previous results indicated that SV40 small t is essential for SV40-induced transformation of diploid cells but dispensable for the transformation of cells with a deletion on the short arm of chromosome 11 (del-11 cells). From these results we concluded that del-11 cells contain a cellular 'SV40 small t-like' factor, which is able to transactivate the HPV16 long control region (LCR) and to complement SV40 large T in transformation. Since SV40 small t and the regulatory 55 kDa subunit (PR55) of protein phosphatase 2A (PP2A), have been shown to inhibit the enzyme activity of PP2A, the PR55 beta subunit could be the putative 'small t-like' factor. In accordance with this hypothesis, we show that the PR55 beta subunit is highly expressed in del-11 but not in diploid cells and is able to trans-activate the HPV16 LCR in diploid cells. Moreover, inhibition of PP2A by okadaic acid resulted in trans-activation of the HPV16 LCR in diploid cells. Alignment of PR55 and SV40 small t showed a common four amino acid motif DKGG. We present evidence that the integrity of this motif is necessary for the PP2A-mediated ability of SV40 small t to trans-activate the HPV16 LCR.
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PMID:The 55 kDa regulatory subunit of protein phosphatase 2A plays a role in the activation of the HPV16 long control region in human cells with a deletion in the short arm of chromosome 11. 133 May 40

The paired helical filament (PHF), which comprises the major fibrous element of the neurofibrillary tangle of Alzheimer's disease, is composed of abnormally phosphorylated microtubule-associated protein tau. Here we show that p42 MAP kinase phosphorylates recombinant tau and converts it to a form which is similar to PHF tau. Of the major serine/threonine protein phosphatases found in mammalian tissues only protein phosphatase 2A (PP2A) could dephosphorylate tau phosphorylated in this manner, with PP2A1 being the most effective form of the enzyme.
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PMID:p42 MAP kinase phosphorylation sites in microtubule-associated protein tau are dephosphorylated by protein phosphatase 2A1. Implications for Alzheimer's disease [corrected]. 133 Jun 87

Purified preparations of a protamine protein kinase from bovine kidney cytosol [Damuni, Amick & Sneed (1989) J. Biol. Chem. 264, 6412-6416] were inactivated after incubation with near-homogeneous preparations of protein phosphatase 2A1 and protein phosphatase 2A2. These protein phosphatase 2A-mediated inactivations of the protamine kinase were unaffected by highly purified preparations of inhibitor 2, but were prevented when the incubations were performed in the presence of 100 nM microcystin-LR, 100 nM okadaic acid or 0.2 mM-ATP. By contrast, highly purified preparations of protein phosphatase 2B, protein phosphatase 2C, the catalytic subunit of protein phosphatase 1, and two forms of a protein tyrosine phosphatase, designated PTPase 1B and T-cell PTPase, had little effect, if any, on protamine kinase activity. Purified preparations of the protamine kinase did not react with anti-phosphotyrosine antibodies, as determined by Western blotting and immunoprecipitation analysis. The results indicate that protein phosphatase 2A is a specific protamine-kinase-inactivating phosphatase.
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PMID:Protein phosphatase 2A is a specific protamine-kinase-inactivating phosphatase. 133 80

We have used a monoclonal antibody (MAb E12), one of several such antibodies raised against theophylline-treated Necturus gallbladder epithelial cells, to isolate a chloride channel protein by the use of an immunoaffinity column and FPLC. This protein (M(r) 219,000) has been reconstituted into a planar lipid bilayer, where it behaves as a chloride-selective channel (PCl/PNa = 20.2; PNa/PK = 1) whose unit conductance is 62.4 +/- 4.6 pS. Antibody added to the trans side (there is no effect from the cis side) causes channel open probability to drop to virtually zero, but has no effect on the conductance or the selectivity of single channels. To test the role of phosphorylation in the activity of the native channel, we studied the effects of the protein phosphatase inhibitor okadaic acid (OA) on intact gallbladders, and showed that channels opened by theophylline treatment and closed by antibody are reopened reversibly by OA (0.01-1.0 microM). Addition of the catalytic subunit of protein phosphatase 2A (PP-2A) to the cis side of a bilayer containing reconstituted chloride channels caused closure of the channels after a delay, and subsequent addition of ATP and the catalytic subunit of cAMP-dependent protein kinase (PKA) caused immediate reopening. These data indicate that (a) this chloride channel protein inserts in a directed way into the bilayer such that the cis side is 'intracellular', (b) the purified channel protein is phosphorylated, and (c) gating from the cellular side is controlled by the direct phosphorylation and dephosphorylation of the channel protein.
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PMID:Reconstitution and regulation of an epithelial chloride channel. 133 26

The toxic effects of cantharidin from blister beetles and its analogs, including the herbicide endothall, are attributable to their high affinity and specificity for a cantharidin-binding protein (CBP). An ammonium sulfate precipitate of mouse liver cytosol was purified by five chromatographic steps to isolate CBP in 14% yield and > 99% purity as monitored by [3H]cantharidin-binding activity. The purification factor of 2230-fold corresponds to a CBP content of 0.045% of the liver cytosolic protein. CBP is a heterodimer consisting of a 61-kDa alpha subunit and a 39-kDa beta subunit. Amino acid sequences of four peptides from CBP-alpha and three peptides from CBP-beta are identical with deduced amino acid sequences for the A alpha regulatory and C beta catalytic subunits, respectively, of protein phosphatase 2A (PP2A). This assignment of CBP as PP2A-AC from structural evidence is supported by biochemical studies with selective substrates and inhibitors. CBP dephosphorylation of phosphorylase alpha is sensitive not only to okadaic acid, as with PP2A, but also to cantharidin and its analogs, consistent with their potency in blocking the radioligand binding site of CBP. Okadaic acid is a potent inhibitor of [3H]cantharidin binding to CBP. PP2A is present in many mammalian tissues and in plants and is involved in regulatory phosphorylation-dephosphorylation events which modulate multiple cellular functions. Inhibition of PP2A activity may account for the diverse effects and toxicity of cantharidin and its analogs, including the herbicide endothall, in mammals and possibly plants.
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PMID:Cantharidin-binding protein: identification as protein phosphatase 2A. 133 51

Atrial natriuretic peptide (ANP) binds to the guanylyl cyclase-A (GC-A) receptor found in tissues such as the kidney and adrenal gland, resulting in marked elevations of the intracellular signaling molecule, cGMP. Here, GC-A is shown to exist as a phosphoprotein when expressed in human embryonic 293 cells. The 32P is principally associated with phosphoserine, with only trace amounts of phosphothreonine. The addition of ANP causes a time-dependent dephosphorylation of the receptor, as well as desensitization, which is not due to an ANP-mediated decrease in the amount of receptor protein. The mobility of GC-A on sodium dodecyl sulfate-polyacrylamide gel electrophoresis increases after treatment of cells with ANP, and protein phosphatase 2A induces the same mobility shift. The protein phosphatase also catalyzes dephosphorylation of GC-A, and this is directly correlated with decreases in ANP-stimulatable guanylyl cyclase activity. Okadaic acid, an inhibitor of protein phosphatase 2A, blocks both the dephosphorylation and the desensitization. Therefore, in contrast to many other cell surface receptors, GC-A is desensitized by ligand-induced dephosphorylation.
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PMID:Dephosphorylation of the guanylyl cyclase-A receptor causes desensitization. 135 76


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