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 present study demonstrates that acute activation with either beta-adrenergic receptor agonists or H(2)O(2) treatment increases protein phosphatase 2a (PP2a) activity in ventricular myocytes. PP2a activation occurs concomitant with an increase in methylation of PP2a, changes in localization of a PP2a targeting subunit PP2aB56alpha, and a decrease in phosphorylation of PP2a substrates, such as troponin I (TnI) and ERK in ventricular myocytes. Okadaic acid, a well-established pharmacological inhibitor of PP2a, and the peptide Thr-Pro-Asp-Tyr-Phe-Leu (TPDYFL) were used to block PP2a methylation, localization, and phosphorylations. TPDYFL is a highly conserved sequence of the PP2a catalytic subunit COOH-terminus. Specifically, both okadaic acid and the peptide increased beta-adrenergic-cAMP-dependent phosphorylation of TnI and blocked the beta-adrenergic-cAMP-dependent translocation of PP2aB56alpha. TPDYFL, but not a scrambled version of this sequence, blocked H(2)O(2)-induced changes in PP2a methylation and TnI dephosphorylation. Okadaic acid produces similar inhibition of H(2)O(2) effects. Thus we propose that the novel peptide TPDYFL acts as an inhibitor of PP2a activity and may be a useful tool to increase our understanding of how PP2a is regulated and the role of PP2a in a variety of physiological and pathological processes. In addition, the present study is consistent with acute beta-adrenergic receptor activation and H(2)O(2) exposure, simultaneously activating kinases and PP2a to work on common substrates, such as TnI. We hypothesize that dual activation of opposing enzymes provides for a tighter regulation of substrate phosphorylations in ventricular myocytes.
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PMID:Acute modulation of PP2a and troponin I phosphorylation in ventricular myocytes: studies with a novel PP2a peptide inhibitor. 1701 62

Visceral leishmaniasis (VL) produced in BALB/c mice through intracardial administration of Leishmania donovani amastigotes was accompanied by hepatosplenomegaly with high organ parasite load and lymphadenopathy when followed up to 4-months or so. To elucidate the mechanism of immunosuppression associated with VL, we report here progressive impairment of the proliferative response of lymph node cells (lymphocytes) from infected animals (I-LNC) to in vitro stimulation with the combination of phorbol 12-myristate 13-acetate (PMA) and ionomycin (Io) that could be related to the downregulation of PKC and MAP kinase (ERK 1/2) activation process. Further, pretreatment of I-LNC with the protein phosphatase inhibitor okadaic acid (OA), but not with calyculin A or sodium orthovanadate, significantly restored their proliferative response as well as PMA-induced activation of PKC. A population of LNC (primarily T-lymphocytes) from chronically infected animals was shown to undergo apoptosis, the number of which increased considerably following PMA+ Io stimulation. The apoptotic pathway, which was followed through binding of cells to Annexin V, activation of caspase-3 and fragmentation of DNA, involved destabilization of mitochondria, probably as a result of downregulation of PKC and Bcl-2. Interestingly, prior incubation of I-LNC with OA reversed the state of cell cycle arrest (anergy) and apoptosis through progression of cells from G0/G1 to S and G2/M phases with transcriptional activation of IL-2 and IL-2R genes. Our results suggest that the cellular (immune) dysfunction in VL could be attributed to dephosphorylation of key molecules in the T-lymphocyte signaling pathway by Ser/Thr phosphatase leading to their inactivation.
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PMID:Lymph node cells from BALB/c mice with chronic visceral leishmaniasis exhibiting cellular anergy and apoptosis: involvement of Ser/Thr phosphatase. 1701 55

Members of the B56 family of protein phosphatase 2A (PP2A) regulatory subunits play crucial roles in Drosophila cell survival. Distinct functions of two B56 subunits were investigated using a combination of RNA interference, DNA microarrays, and proteomics. RNA interference-mediated knockdown of the B56-1 subunit (PP2A-B') but not the catalytic (mts) or B56-2 subunit (wdb) of PP2A resulted in increased expression of the apoptotic inducers reaper and sickle. Co-knockdown of B56-1 with reaper, but not with sickle, reduced the apoptosis caused by depletion of the B56 subunits. Two-dimensional gel electrophoresis and mass spectrometry identified proteins modified in cells depleted of PP2A subunits. These included generation of caspase-dependent cleavage products, increases in protein abundance, and covalent modifications. Results suggested that up-regulation of the ribosome-associated protein stubarista can serve as a sensitive marker of apoptosis. Up-regulation of transcripts for multiple glutathione transferases and other proteins suggested that loss of PP2A affected pathways involved in the response to oxidative stress. Knockdown of PP2A elevated basal JNK activity and substantially decreased activation of ERK in response to oxidative stress. The results reveal that the B56-containing isoform of PP2A functions within multiple signaling pathways, including those that regulate expression of reaper and the response to oxidative stress, thus promoting cell survival in Drosophila.
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PMID:A functional genomics analysis of the B56 isoforms of Drosophila protein phosphatase 2A. 1712 11

Adenosine is arguably the most potent and widespread presynaptic modulator in the CNS, yet adenosine receptor signal transduction pathways remain unresolved. Here, we demonstrate a novel mechanism in which adenosine A1 receptor stimulation leads to p38 mitogen-activated protein kinase (MAPK) activation and contributes to the inhibition of synaptic transmission. Western blot analysis indicated that selective A1 receptor activation [with N6-cyclopentyladenosine (CPA)] resulted in rapid increases in phosphorylated p38 (phospho-p38) MAPK immunoreactivity in membrane fractions, and decreases in phospho-p38 MAPK in cytosolic fractions. Immunoprecipitation with a phospho-p38 MAPK antibody revealed constitutive association of this phosphoprotein with adenosine A1 receptors. Phospho-p38 MAPK activation by A1 receptor stimulation induced translocation of PP2a (protein phosphatase 2a) to the membrane. We then examined the actions of p38 MAPK activation in A1 receptor-mediated synaptic inhibition. Excitatory postsynaptic field potentials evoked in area CA1 of the rat hippocampus markedly decreased in response to adenosine (10 microM), the A1 receptor agonist CPA (40 nM), or a 5 min exposure to hypoxia. These inhibitory responses were mediated by A1 receptor activation because the selective antagonist DPCPX (8-cyclopentyl-1,3-dipropylxanthine) (100 nM) prevented them. In agreement with the biochemical analysis, the selective p38 MAPK inhibitor SB203580 [4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)-1H-imidazole] (25 microM) blocked the inhibitory actions of A1 receptor activation, whereas both the inactive analog SB202474 [4-ethyl-2-(p-methoxyphenyl)-5-(4'-pyridyl)-1H-imidazole] (25 microM) and the ERK 1/2 (extracellular signal-regulated kinase 1/2) MAPK inhibitor PD98059 [2'-amino-3'-methoxyflavone] (50 microM) were ineffective. In contrast, the p38 MAPK inhibitors did not inhibit GABA(B)-mediated synaptic depression. These data suggest A1 receptor-mediated p38 MAPK activation is a crucial step underlying the presynaptic inhibitory effect of adenosine on CA3-CA1 synaptic transmission.
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PMID:p38 mitogen-activated protein kinase contributes to adenosine A1 receptor-mediated synaptic depression in area CA1 of the rat hippocampus. 1713 4

The protein phosphatase 2A (PP2A) is a serine/threonine phosphatase involved in the regulation of multiple signaling pathways including the Wnt/beta-catenin and the ERK pathways. To understand the complex signaling networking associated with PP2A, we searched proteins interacting with the catalytic subunit of protein phosphatase 2A (PP2Ac) by a pull-down analysis followed by 2-D gel electrophoresis and proteomic analyses. The probability of identification of the proteins interacting with PP2Ac was increased by searching proteins differently interacting with PP2Ac according to stimulation of Wnt3a, which regulates both the Wnt/beta-catenin and the ERK pathways. Around 100 proteins, pulled-down by His-tagged PP2Ac, were identified in 2-D gels stained with CBB. By MALDI-TOF-MS analyses of 45 protein spots, we identified several proteins that were previously known to interact with PP2A, such as Axin and CaMK IV. In addition, we also identified many proteins that potentially interact with PP2Ac. The interactions of several candidate proteins, such as tuberous sclerosis complex 2, RhoB, R-Ras, and Nm23H2, with PP2Ac, were confirmed by in vitro binding analyses and/or coimmunoprecipitation experiments.
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PMID:Identification of proteins interacting with the catalytic subunit of PP2A by proteomics. 1716 75

Pax-6 is an evolutionarily conserved transcription factor and acts high up in the regulatory hierarchy controlling eye and brain development in humans, mice, zebrafish, and Drosophila. Previous studies have shown that Pax-6 is a phosphoprotein, and its phosphorylation by ERK, p38, and homeodomain-interacting protein kinase 2 greatly enhances its transactivation activity. However, the protein phosphatases responsible for the dephosphorylation of Pax-6 remain unknown. Here, we present both in vitro and in vivo evidence to show that protein serine/threonine phosphatase-1 is a major phosphatase that directly dephosphorylates Pax-6. First, purified protein phosphatase-1 directly dephosphorylates Pax-6 in vitro. Second, immunoprecipitation-linked Western blot revealed that both protein phosphatase-1alpha and protein phosphatase-1beta interact with Pax-6. Third, overexpression of protein phosphatase-1 in human lens epithelial cells leads to dephosphorylation of Pax-6. Finally, inhibition of protein phosphatase-1 activity by calyculin A or knockdown of protein phosphatase-1alpha and protein phosphatase-1beta by RNA interference leads to enhanced phosphorylation of Pax-6. Moreover, our results also demonstrate that dephosphorylation of Pax-6 by protein phosphatase-1 significantly modulates its function in regulating expression of both exogenous and endogenous genes. These results demonstrate that protein phosphatase 1 acts as a major phosphatase to dephosphorylate Pax-6 and modulate its function.
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PMID:Protein phosphatase-1 modulates the function of Pax-6, a transcription factor controlling brain and eye development. 1737 6

Induction of G(2)/M phase transition in mitotic and meiotic cell cycles requires activation by phosphorylation of the protein phosphatase Cdc25. Although Cdc2/cyclin B and polo-like kinase (PLK) can phosphorylate and activate Cdc25 in vitro, phosphorylation by these two kinases is insufficient to account for Cdc25 activation during M phase induction. Here we demonstrate that p42 MAP kinase (MAPK), the Xenopus ortholog of ERK2, is a major Cdc25 phosphorylating kinase in extracts of M phase-arrested Xenopus eggs. In Xenopus oocytes, p42 MAPK interacts with hypophosphorylated Cdc25 before meiotic induction. During meiotic induction, p42 MAPK phosphorylates Cdc25 at T48, T138, and S205, increasing Cdc25's phosphatase activity. In a mammalian cell line, ERK1/2 interacts with Cdc25C in interphase and phosphorylates Cdc25C at T48 in mitosis. Inhibition of ERK activation partially inhibits T48 phosphorylation, Cdc25C activation, and mitotic induction. These findings demonstrate that ERK-MAP kinases are directly involved in activating Cdc25 during the G(2)/M transition.
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PMID:Regulation of Cdc25C by ERK-MAP kinases during the G2/M transition. 1738 81

alpha-4 is an essential gene and is a dominant antiapoptotic factor in various tissues that is a regulatory subunit for type 2A protein phosphatases. A multiplexed phosphorylation site screen revealed that knockdown of alpha-4 by small interfering RNA (siRNA) increased p38 mitogen-activated protein kinase (MAPK) and c-Jun phosphorylation without changes in JNK or ERK. FLAG-alpha-4 coprecipitated hemagglutinin-MEK3 plus endogenous protein phosphatase 2A (PP2A) and selectively enhanced dephosphorylation of Thr193, but not Ser189, in the activation loop of MEK3. Overexpression of alpha-4 suppressed p38 MAPK activation in response to tumor necrosis factor alpha (TNF-alpha). The alpha-4 dominant-negative domain (DND) (residues 220 to 340) associated with MEK3, but not PP2A, and its overexpression sensitized cells to activation of p38 MAPK by TNF-alpha and interleukin-1beta, but not by ansiomycin or sorbitol. The response was diminished by nocodazole or by siRNA knockdown of the Opitz syndrome protein Mid1 that binds alpha-4 to microtubules. Interference by alpha-4 DND or alpha-4 siRNA increased caspase 3/7 activation in response to TNF-alpha. Growth of transformed cells in soft agar was enhanced by alpha-4 and suppressed by alpha-4 DND. The results show that alpha-4 targets PP2A activity to MEK3 to suppress p38 MAPK activation by cytokines, thereby inhibiting apoptosis and anoikis.
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PMID:Cytokine activation of p38 mitogen-activated protein kinase and apoptosis is opposed by alpha-4 targeting of protein phosphatase 2A for site-specific dephosphorylation of MEK3. 1743 31

Myf5 plays a central role in determination of the myogenic lineage, yet the signalling pathways that control its activation remain unclear. In adult muscle, Myf5 is expressed in satellite cells and muscle spindles but not by myonuclei. However, Myf5 expression is activated in myonuclei in response to muscle denervation. This can be modelled in culture using Myf5nlacZ/+ mice, allowing signalling pathways controlling Myf5 to be readily examined. We found that mitogen-rich medium induces activation of the Myf5 locus through calcium, which interacts with calmodulin to promote calcineurin and calmodulin kinase. Calcineurin activates NFAT to control Myf5 activation, while p38/JNK activity prevents activation by this route. Calmodulin kinase however, acts predominately through ERK signalling to activate Myf5. Interestingly, we found that IGF-1 can substitute for mitogen-rich medium and activates Myf5 through calcium, PI3K and ERK pathways. Together these observations show that Myf5 activation in adult muscle is accomplished by a complex signalling pathway, and provides candidates that can be examined for their role in Myf5 regulation during development.
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PMID:Control of Myf5 activation in adult skeletal myonuclei requires ERK signalling. 1748 56

The evaluation of signaling pathways leading to gene induction by VEGF-A and IL-1 in endothelial cells supports the importance of the NF-kappaB pathway for the IL-1-induced gene repertoire, whereas VEGF-A is a strong and preferential trigger of signals via PLC-gamma. This leads (i) via Ca(++) to the activation of calcineurin and NFAT and (ii) via PKC and the MEK/ERK MAPK pathway to the upregulation of EGR-1. Part of the VEGF-triggered gene induction depends on a cooperation of the transcription factors NFAT and EGR-1. Gene activation via PLC-gamma provides VEGF with the potency to induce a wide spectrum of genes including many also upregulated by IL-1. A gene upregulated by VEGF and IL-1 is the DSCR-1 gene, which encodes an inhibitor of calcineurin. DSCR1 is induced by NFAT or NF-kappaB and limits Ca(++) signaling in a negative feed-back loop. Similarly, NAB2, a corepressor of EGR-1, is induced by EGR-1 and limits EGR-1 effects. Adenoviral overexpression of DSCR1 or NAB2 inhibited part of VEGF-induced gene expression and reduced sprouting in angiogenesis models.
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PMID:Signals and genes induced by angiogenic growth factors in comparison to inflammatory cytokines in endothelial cells. 1764 95


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