Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Arachidonic acid (AA) increased, at constant Ca2+, the levels of force and 20-kDa myosin light chain (MLC20) phosphorylation in permeabilized smooth muscle, and slowed relaxation and MLC20 dephosphorylation. The Ca(2+)-sensitizing effect of AA was not inhibited by inhibitors of AA metabolism (indomethacin, nordihydroguaiaretic acid, or propyl gallate), of protein kinase C (pseudopeptide) or by guanosine-5'-O-(beta-thiodiphosphate) and was abolished by oxidation of AA in air. A non-metabolizable AA analog, 5,8,11,14-eicosatetraynoic acid) also had Ca(2+)-sensitizing effects. Extensive treatment with saponin abolished the Ca(2+)-sensitizing effects of phorbol 12,13-dibutyrate and guanosine-5'-O-(gamma-thiotriphosphate), but not that of AA. A purified, oligomeric MLC20 phosphatase isolated from gizzard smooth muscle was dissociated into subunits by AA, and its activity was inhibited toward heavy meromyosin but not phosphorylase. We conclude that AA may act as a messenger-promoting protein phosphorylation through direct inhibition of the form of protein phosphatase(s) that dephosphorylate MLC20 in vivo.
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PMID:Arachidonic acid inhibits myosin light chain phosphatase and sensitizes smooth muscle to calcium. 132 35

Arachidonate activation of the NADPH-oxidase in intact neutrophils and in a cell-free O2- generation system was compared to synergistic activation in response to arachidonate and agents that effect protein phosphorylation. In intact neutrophils, suboptimal doses of retinal which increase protein phosphorylation, or 4B-phorbol 12-myristate 13-acetate (PMA) an activator of protein kinase C, induced minimal O2- release, but primed neutrophils to release enhanced amounts of O2- in response to 2.5 microM arachidonate. In contrast to retinal or PMA, okadaic acid, a specific inhibitor of serine/threonine protein phosphatases, did not induce any release of O2-, but significantly increased the maximal rate and duration of O2- release in response to arachidonate. In the cell-free system, only arachidonate induced O2- generation. Consistent with previous findings, activation of the cell-free system was dependent of the presence of light membranes, cytosol, NADPH, Mg2+, and 82 microM arachidonate. Pretreatment of neutrophils with suboptimal doses of PMA or retinal had little effect on the arachidonate-stimulated release of O2- in cell-free preparations of these cells. However, cytosol (but not light membranes) from PMA or retinal-primed neutrophils was more effective in completing resting membrane NADPH-oxidase activity when compared to cytosol from resting cells. The addition of protein kinase C inhibitors staurosporine and 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine decreased the effectiveness of PMA-primed cytosol to complete the cell-free system, but had little effect on cytosol obtained from cells primed with retinal. The addition of protein phosphatase inhibitors, p-nitrophenyl phosphate or okadaic acid to neutrophil cavitates increased 3-fold the release of O2- in cell-free preparations of these cells. Okadaic acid and p-nitrophenyl phosphate also increased the effectiveness of both cytosol and light membranes to complete the cell-free system when combined with cytosol or light membranes from resting neutrophils, respectively, indicating that both fractions are affected by the inhibition of protein phosphatase activity. These data indicate that increases in protein phosphorylation alone do not lead to the activation of the NADPH-oxidase, but in addition to the requirement of an anionic amphiphile, the release of O2- from intact neutrophils or in the cell-free system is increased by stimulus activation of protein kinase C or more impressively by inhibition of protein phosphatase activity.
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PMID:Arachidonate activation of the neutrophil NADPH-oxidase. Synergistic effects of protein phosphatase inhibitors compared with protein kinase activators. 165 30

1. Exogenous arachidonic acid (AA) inhibits the protein phosphatase that dephosphorylates smooth muscle myosin, thus sensitizing the contractile response to Ca2+; it also inhibits voltage-gated Ca2+ channels in smooth muscle. The purpose of the present study was to determine whether endogenous AA is increased by agonists in a manner consistent with its role as a messenger regulating myosin phosphatase and Ca2+ channels. Both AA and diacylglycerol (DAG) were measured in [3H]AA-labelled intact and permeabilized (with staphylococcal alpha-toxin) rabbit femoral arteries stimulated with the alpha 1-adrenergic agonist phenylephrine (PE) (intact and permeabilized smooth muscles) or by guanosine-5'-O-(3-thiotriphosphate (GTP gamma S; permeabilized smooth muscles in which the [Ca2+] was maintained constant). Arachidonic acid mass was determined with gas chromatography and mass spectrometry (GC-MS). 2. In intact smooth muscle, PE increased both AA and DAG levels significantly, to 210 and 145% of baseline values, respectively. Another Ca2+-sensitizing agent, the thromboxane analogue U46619, caused a similar increase in AA and DAG levels in rabbit pulmonary artery. 3. In permeabilized smooth muscle at constant [Ca2+](pCa 6.5) GTP gamma S-induced AA and DAG release preceded force development and GTP gamma S (50 microM, 10 min) increased AA mass to 61-88 microM. 4. Phorbol-12,13-dibutyrate (PDBu), another Ca2+-sensitizing agent, also increased both AA and DAG levels in permeabilized smooth muscle at pCa 6.5, whereas the inactive analogue, 4 alpha-phorbol, did not have a Ca2+-sensitizing effect, nor did it increase AA and DAG levels. 5. In the virtual absence of Ca2+ (pCa > 8) GTP gamma S also increased AA and DAG levels by 3.5- and 1.6-fold, respectively. The effect of free Ca2+ itself on AA and DAG release was modest in the physiological range (pCa 7.0 to pCa 6.0), but pCa 4.5 caused an approximately 3- to 4-fold increase in AA and DAG levels, compared with the levels at pCa 8. In permeabilized ileum smooth muscle maintained at constant [Ca2+] (pCa 6.0), carbachol also significantly increased AA to 1.75 times its original value within 1 min of its application. 6. Our results are consistent with, although do not prove, the roles of AA and DAG as second and/or co-messenger(s) in smooth muscle, while the increases in AA and DAG levels induced by PDBu raise the possibility that they contribute to some of the cellular effects of phorbol esters.
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PMID:Arachidonic acid and diacylglycerol release associated with inhibition of myosin light chain dephosphorylation in rabbit smooth muscle. 756 27

Arachidonic acid (AA), a cis-unsaturated fatty acid that activates certain subspecies of protein kinase C (PKC), has been proposed to act as a retrograde messenger in modifying the efficacy of synapses during long-term potentiation (LTP). One prominent PKC substrate of the nerve terminal membrane, GAP-43 (F1, B-50, neuromodulin), shows an increase in phosphorylation that correlates with the persistence of LTP. The present study investigated whether AA might exert its effects on presynaptic endings by modulating the phosphorylation of GAP-43 and other membrane-bound proteins. Using synaptosomal membranes from the rat cerebrocortex, in which in vivo relationships between protein kinases and their native substrates are likely to be preserved, we found that in the absence of Ca2+, AA exerted a modest effect on the phosphorylation of GAP-43 and several other proteins; however, when AA was applied in conjunction with Ca2+, GAP-43 showed a particularly striking response: at Ca2+ levels likely to exist at the nerve terminal membrane during synaptic activity (10(-7) to 10(-5) M), AA (50 microM) increased the sensitivity of GAP-43 phosphorylation to Ca2+ by an order of magnitude, and increased its maximal level of phosphorylation by 50%. At resting Ca2+ levels, AA potentiated the stimulation in GAP-43 phosphorylation produced by 4 beta-phorbol 12,13-dibutyrate, a diacylglycerol (DAG) analog. The stimulatory effect of AA and its synergistic interaction with Ca2+ were found to be mediated by PKC, since they were blocked by a specific peptide inhibitor of PKC, [Ala25]PKC(19-31), but were unaffected by an inhibitor of protein phosphatase activity or by scavengers of free radicals. Since GAP-43 has been implicated in the development and plasticity of synaptic relationships, the synergistic effects of AA and the intracellular signals Ca2+ and DAG on the phosphorylation of GAP-43 may serve as an AND gate to modify presynaptic function and/or structure in response to coincident pre- and postsynaptic activity.
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PMID:Activation of protein kinase C by arachidonic acid selectively enhances the phosphorylation of GAP-43 in nerve terminal membranes. 841 Jan 92

Stimulation of platelet-activating factor (PAF) receptor induces activation of extracellular signal-regulated kinase (ERK) and cytosolic phospholipase A2 (cPLA2) and release of arachidonic acid in Chinese hamster ovary cells. To determine whether the dual-specificity protein phosphatase PYST1/MKP-3 inhibits phosphorylation of cPLA2, we have generated a cell line that conditionally expresses PYST1 under the control of a tetracycline-regulated inducible system. We found that induction of PYST1 suppressed phosphorylation and activation of cPLA2 as well as ERK. Arachidonic acid release was also reduced by about 30%. Pretreatment of cells with an MEK inhibitor, PD98059, had similar effects on PAF-induced cPLA2 phosphorylation and arachidonic acid release. These experiments demonstrate that expression of PYST1 prevents phosphorylation of a cytoplasmic substrate for ERK. Thus, this inducible system may offer a valuable means of investigating physiological roles of ERK in vivo.
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PMID:Conditional expression of the dual-specificity phosphatase PYST1/MKP-3 inhibits phosphorylation of cytosolic phospholipase A2 in Chinese hamster ovary cells. 987 62

The Galpha subunits of the G(12) family of heterotrimeric G proteins, defined by Galpha(12) and Galpha(13), are involved in many signaling pathways and diverse cellular functions. In an attempt to elucidate downstream effectors of Galpha(12) for cellular functions, we have performed a yeast two-hybrid screening of a rat brain cDNA library and revealed that Ser/Thr protein phosphatase type 5 (PP5) is a novel effector of Galpha(12) and Galpha(13). PP5 is a newly identified phosphatase and consists of a C-terminal catalytic domain and an N-terminal regulatory tetratricopeptide repeat (TPR) domain [2]. Arachidonic acid was recently shown to activate PP5 phosphatase activity by binding to its TPR domain, however the precise regulatory mechanism of PP5 phosphatase activity is not fully determined. In this study, we show that active forms of Galpha(12) and Galpha(13) specifically interact with PP5 through its TPR domain and activate its phosphatase activity about 2.5-fold. Active forms of Galpha(12) and Galpha(13) also enhance the arachidonic acid-stimulated PP5 phosphatase activity about 2.5-fold. Moreover, we demonstrate that the active form of Galpha(12) translocates PP5 to the cell periphery and colocalizes with PP5. These results propose a new signaling pathway of G(12) family G proteins.
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PMID:Galpha(12) and Galpha(13) interact with Ser/Thr protein phosphatase type 5 and stimulate its phosphatase activity. 1217 67

Ceramide is a lipid second messenger that acts on multiple-target enzymes, some of which are involved in other signal-transduction systems. We have previously demonstrated that endogenous ceramide modifies the metabolism of brain ethanolamine plasmalogens. The mechanism involved was studied. On the basis of measurements of breakdown products, specific inhibitor effects, and previous findings, we suggest that a plasmalogen-selective phospholipase A2 is the ceramide target. Arachidonate-rich pools of the diacylphosphatidylethanolamine subclass were also affected by ceramide, but the most affected were plasmalogens. Concomitantly with production of free arachidonate, increased 1-O-arachidonoyl ceramide formation was observed. Quinacrine (phospholipase A2 inhibitor) and 1-O-octadecyl-2-O-methyl-rac-glycerol-3-phosphocholine (CoA-independent transacylase inhibitor) prevented all of these ceramide-elicited effects. Therefore, phospholipase and transacylase activities are tightly coupled. Okadaic acid (phosphatase 2A inhibitor) and PD 98059 (mitogen-activated protein kinase inhibitor) modified basal levels of ceramide and sphingomyelinase-induced accumulation of ceramide, respectively. Therefore, they provided no evidence to determine whether there is a sensitive enzyme downstream of ceramide. The evidence shows that there are serine-dependent and thiol-dependent enzymes downstream of ceramide generation. Furthermore, experiments with Ac-DEVD-CMK (caspase-3 specific inhibitor) have led us to conclude that caspase-3 is downstream of ceramide in activating the brain plasmalogen-selective phospholipase A2.
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PMID:Signaling events mediating activation of brain ethanolamine plasmalogen hydrolysis by ceramide. 1249 73

Arachidonic acid (AA) regulates intracellular calcium concentration ([Ca2+]i) in a variety of cell types including salivary cells. In the present study, the effects of serine/threonine phosphatases on AA-induced Ca(2+) signaling in mouse parotid acini were determined. Mice were euthanized with CO2. Treatment of acini with the serine/threonine phosphatase inhibitor calyculin A blocked both thapsigargin- and carbachol-induced Ca2+ entry but resulted in an enhancement of AA-induced Ca2+ release and entry. Effects were mimicked by the protein phosphatase-1 (PP1) inhibitor tautomycin but were inhibited by the PP2A inhibitor okadaic acid. The protein kinase A (PKA) inhibitor PKI(14-22) significantly attenuated AA-induced enhancement of Ca2+ release and entry in the presence of calyculin A, whereas it had no effect on calyculin A-induced inhibition of thapsigargin-induced Ca2+ responses. The ryanodine receptor (RyR) inhibitor, tetracaine, and StHt-31, a peptide known to competitively inhibit type II PKA regulatory subunit binding to PKA-anchoring protein (AKAP), abolished calyculin A enhancement of AA-induced Ca2+ release and entry. StHt-31 also abolished forskolin potentiation of 4-chloro-3-ethylphenol (4-CEP) and AA on Ca2+ release but had no effect on 8-(4-methoxyphenylthio)-2'-O-methyladenosine-3',5'-cAMP potentiation of 4-CEP responses. Results suggest that inhibition of PP1 results in an enhancement of AA-induced [Ca2+]i via PKA, AKAP, and RyRs.
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PMID:Inhibition of serine/threonine phosphatase enhances arachidonic acid-induced [Ca2+]i via protein kinase A. 1898 53

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