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)

Cardiac-specific expression of an activated calcineurin protein in the hearts of transgenic (CLN) mice produces a profound hypertrophy that rapidly progresses to heart failure. While calcineurin is regulated by Ca2+, the potential effects of calcineurin on cardiac myocyte Ca2+ handling has not been evaluated. To this end, we examined L-type Ca2+ currents (I(Ca)) in left ventricular myocytes. CLN myocytes had larger (approximately 80%) cell capacitance and enhanced I(Ca) density (approximately 20%) compared with non-transgenic (NTG) littermates, but no change in the current-voltage relationship, single-channel conductance or protein levels of alpha 1 or beta 2 subunit of L-type Ca2+ channels. Interestingly, the kinetics of I(Ca) inactivation was faster (approximately two-fold) in CLN myocytes compared with NTG myocytes. Ryanodine application slowed the rate of I(Ca) inactivation in both groups and abolished the kinetic difference, suggesting that Ca2+ dependent inactivation is increased in CLN myocytes due to altered SR Ca2+ release. Treatment of CLN mice with Cyclosporine A (CsA), a calcineurin inhibitor, prevented myocyte hypertrophy and changes in I(Ca) activity and inactivation kinetics. However, there was no direct effect of CsA on I(Ca) in either NTG or CLN myocytes, suggesting that endogenous calcineurin activity does not directly regulate Ca2+ channel activity. This interpretation is consistent with the observation that I(Ca) density, inactivation kinetics and regulation by isoproterenol were normal in cardiac-specific transgenic mice expressing calcineurin inhibitory protein domains from either Cain or AKAP79. Taken together these data suggest that chronic activation of calcineurin is associated with myocyte hypertrophy and a secondary enhancement of intracellular Ca2+ handling that is tied to the hypertrophy response itself.
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PMID:Enhanced Ca2+ channel currents in cardiac hypertrophy induced by activation of calcineurin-dependent pathway. 1116 30

Muscarinic acetylcholine receptors in NG108-15 neuroblastoma x glioma cells, and beta-adrenergic or angiotensin II receptors in cortical astrocytes and/or ventricular myocytes, utilize the direct signaling pathway to ADP-ribosyl cyclase within cell membranes to produce cyclic ADP-ribose (cADPR) from beta-NAD+. This signal cascade is analogous to the previously established transduction pathways from bradykinin receptors to phospholipase Cbeta and beta-adrenoceptors to adenylyl cyclase via G proteins. Upon receptor stimulation, the newly-formed cADPR may coordinately function to upregulate the release of Ca2+ from the type II ryanodine receptors as well as to facilitate Ca2+ influx through voltage-dependent Ca2+ channels. cADPR interacts with FK506, an immunosuppressant, at FKBP12.6, FK506-binding-protein, and calcineurin, or ryanodine receptors. cADPR also functions through activating calcineurin released from A-kinase anchoring protein (AKAP79). Thus, some G(q/11)-coupled receptors can control cADPR-dependent modulation in Ca2+ signaling.
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PMID:Signal transduction from bradykinin, angiotensin, adrenergic and muscarinic receptors to effector enzymes, including ADP-ribosyl cyclase. 1125 66

Second messengers regulate synaptic plasticity by influencing the balance between kinase and phosphatase activity. One target of this balance is the phosphorylation state of the AMPA receptor glutamate receptor 1 (GluR1) subunit. Hippocampal long-term depression (LTD) is a calcium-dependent downregulation of synaptic AMPA receptor currents associated with dephosphorylation of Ser845, a cAMP-dependent protein kinase (PKA) site on GluR1. Recruitment of kinases and phosphatases to the AMPA receptor might enable modulation of AMPA receptor function. The neuronal A-kinase anchoring protein AKAP79/150 interacts with PKA and the calcium-dependent protein phosphatase PP2B and is linked to the AMPA receptor GluR1 subunit by synapse-associated protein 97 (SAP97), a membrane-associated guanylate kinase family protein. Here we demonstrate that AKAP79 not only promotes basal phosphorylation of Ser845 but also confers a calcium- and PP2B-mediated downregulation to GluR1 receptor currents. This AKAP79-dependent downregulation is contingent on the local presence of PKA, Ser845 of GluR1, and a PDZ (postsynaptic density 95/Discs large/zona occludens 1)-domain interaction between GluR1 and SAP97, all of which support basal phosphorylation of the receptor. These findings suggest that the AKAP79 signaling complex is sufficient to couple intracellular calcium levels to the PKA phosphorylation state of GluR1. Thus, the integration of intracellular signals relevant for LTD may be transduced to GluR1 by the AKAP79 signaling complex.
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PMID:Regulation of GluR1 by the A-kinase anchoring protein 79 (AKAP79) signaling complex shares properties with long-term depression. 1194 7

At the postsynaptic membrane of glutamatergic synapses, the cAMP-dependent protein kinase (PKA), protein kinase C (PKC), and calcineurin (CaN) anchoring protein AKAP79/150 is recruited to NMDA and AMPA glutamate receptors by postsynaptic density (PSD)-95 family membrane-associated guanylate kinase (MAGUK) scaffold proteins. These signaling scaffold complexes may function to regulate receptor phosphorylation in synaptic plasticity. Thus, it is important to understand regulation of AKAP79/150 targeting to synapses and recruitment to PSD-MAGUK complexes. AKAP79 is targeted to the plasma membrane by an N-terminal basic domain that binds phosphatidylinositol-4,5-bisphosphate (PI-4,5-P(2)) and is regulated by PKC phosphorylation and calmodulin binding. Here we demonstrate that this same domain also binds F-actin in a calmodulin- and PKC-regulated manner, targets to membrane ruffles enriched in F-actin and PI-4,5-P(2) in COS7 cells, and localizes to dendritic spines with F-actin and PSD-MAGUKs in hippocampal neurons. Inhibition of actin polymerization disrupted AKAP79 targeting of PKA and CaN to ruffles in COS7 cells and endogenous AKAP79/150 dendritic spine localization with PKA, CaN, and PSD-MAGUKs in neurons. AKAP79/150 postsynaptic localization was rapidly regulated by NMDA receptors through CaN activation and F-actin remodeling, further suggesting that AKAP79/150 signaling scaffold targeting depends on actin dynamics. NMDA receptor activation also regulated dendritic spine localization of PKA and CaN and association of the AKAP79/150-PKA complex with PSD-MAGUKs. Because AMPA receptor PKA phosphorylation and synaptic localization are regulated by similar NMDA receptor-CaN signaling pathways linked to hippocampal long-term depression, this regulation of AKAP79/150 postsynaptic targeting might be important for synaptic plasticity.
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PMID:Regulation of A-kinase anchoring protein 79/150-cAMP-dependent protein kinase postsynaptic targeting by NMDA receptor activation of calcineurin and remodeling of dendritic actin. 1217

Compartmentalization of protein kinases and phosphatases with substrates is a means to increase the efficacy of signal transduction events. The A-kinase anchoring protein, AKAP79, is a multivalent anchoring protein that maintains the cAMP-dependent protein kinase, protein kinase C, and protein phosphatase-2B (PP2B/calcineurin) at the postsynaptic membrane of excitatory synapses where it is recruited into complexes with N-methyl-d-aspartic acid or alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA)-subtype glutamate receptors. We have used cellular targeting of AKAP79 truncation and deletion mutants as an assay to map the PP2B-binding site on AKAP79. We demonstrate that residues 315-360 are necessary and sufficient for AKAP79-PP2B anchoring in cells. Multiple determinants contained within this region bind directly to the A subunit of PP2B and inhibit phosphatase activity. Peptides spanning the 315-360 region of AKAP79 can antagonize PP2B anchoring in vitro and targeting in transfected cells. Electrophysiological experiments further emphasize this point by demonstrating that a peptide encompassing residues 330-357 of AKAP79 attenuates PP2B-dependent down-regulation of GluR1 receptor currents when perfused into HEK293 cells. We propose that the structural features of this AKAP79-PP2B-binding domain may share similarities with other proteins that serve to coordinate PP2B localization and activity.
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PMID:Mapping the protein phosphatase-2B anchoring site on AKAP79. Binding and inhibition of phosphatase activity are mediated by residues 315-360. 1235 62

Scaffold, anchoring, and adaptor proteins coordinate the assembly and localization of signaling complexes providing efficiency and specificity in signal transduction. The PKA, PKC, and protein phosphatase-2B/calcineurin (CaN) scaffold protein A-kinase anchoring protein (AKAP) 79 is localized to excitatory neuronal synapses where it is recruited to glutamate receptors by interactions with membrane-associated guanylate kinase (MAGUK) scaffold proteins. Anchored PKA and CaN in these complexes could have important functions in regulating glutamate receptors in synaptic plasticity. However, direct evidence for the assembly of complexes containing PKA, CaN, AKAP79, and MAGUKs in intact cells has not been available. In this report, we use immunofluorescence and fluorescence resonance energy transfer (FRET) microscopy to demonstrate membrane cytoskeleton-localized assembly of this complex. Using FRET, we directly observed binding of CaN catalytic A subunit (CaNA) and PKA-RII subunits to membrane-targeted AKAP79. We also detected FRET between CaNA and PKA-RII bound simultaneously to AKAP79 within 50 A of each other, thus providing the first direct evidence of a ternary kinase-scaffold-phosphatase complex in living cells. This finding of AKAP-mediated PKA and CaN colocalization on a nanometer scale gives new appreciation to the level of compartmentalized signal transduction possible within scaffolds. Finally, we demonstrated AKAP79-regulated membrane localization of the MAGUK synapse-associated protein 97 (SAP97), suggesting that AKAP79 functions to organize even larger signaling complexes.
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PMID:Imaging kinase--AKAP79--phosphatase scaffold complexes at the plasma membrane in living cells using FRET microscopy. 1250 94

Cell signalling mediated via GPCRs (G-protein-coupled receptors) is a major paradigm in biology, involving the assembly of receptors, G-proteins, effectors and downstream elements into complexes that approach in design 'solid-state' signalling devices. Scaffold molecules, such as the AKAPs (A-kinase anchoring proteins), were discovered more than a decade ago and represent dynamic platforms, enabling multivalent signalling. AKAP79 and AKAP250 were the first to be shown to bind to membrane-embedded GPCRs, orchestrating the interactions of various protein kinases (including tyrosine kinases), protein phosphatases (e.g. calcineurin) and cytoskeletal elements with at least one member of the superfamily of GPCRs, the prototypical beta2-adrenergic receptor. In this review, the multivalent interactions of AKAP250 with the cell membrane, receptor, cytoskeleton and constituent components are detailed, providing a working model for AKAP-based GPCR signalling complexes. Dynamic regulation of the AKAP-receptor complex is mediated by ordered protein phosphorylation.
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PMID:AKAPs (A-kinase anchoring proteins) and molecules that compose their G-protein-coupled receptor signalling complexes. 1471 81

Calcineurin is a phosphoprotein phosphatase that channels intracellular Ca signals into multiple biological pathways. Calcineurin is known to interact directly with its substrate nuclear factor of activated T cells (NFAT or NFATc), with other substrates, and with several targeting and scaffold proteins including AKAP79 and Cabin1/cain. The calcineurin-NFAT interaction depends on recognition of a PxIxIT sequence motif present in NFAT-family proteins and in certain other calcineurin-interacting proteins. Here, we define the structural basis for the interaction of calcineurin with NFAT and with other proteins possessing the PxIxIT motif. The calcineurin-PxIxIT contact has a direct parallel in the contact of protein phosphatase 1 with its regulatory proteins, suggesting that the evolution of these related phosphatases involved local remodelling of an ancestral docking site.
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PMID:Structural delineation of the calcineurin-NFAT interaction and its parallels to PP1 targeting interactions. 1536 89

A-kinase-anchoring protein (AKAP) 79/150 organizes a scaffold of cAMP-dependent protein kinase (PKA), protein kinase C (PKC), and protein phosphatase 2B/calcineurin that regulates phosphorylation pathways underlying neuronal long-term potentiation and long-term depression (LTD) synaptic plasticity. AKAP79/150 postsynaptic targeting requires three N-terminal basic domains that bind F-actin and acidic phospholipids. Here, we report a novel interaction of these domains with cadherin adhesion molecules that are linked to actin through beta-catenin (beta-cat) at neuronal synapses and epithelial adherens junctions. Mapping the AKAP binding site in cadherins identified overlap with beta-cat binding; however, no competition between AKAP and beta-cat binding to cadherins was detected in vitro. Accordingly, AKAP79/150 exhibited polarized localization with beta-cat and cadherins in epithelial cell lateral membranes, and beta-cat was present in AKAP-cadherin complexes isolated from epithelial cells, cultured neurons, and rat brain synaptic membranes. Inhibition of epithelial cell cadherin adhesion and actin polymerization redistributed intact AKAP-cadherin complexes from lateral membranes to intracellular compartments. In contrast, stimulation of neuronal pathways implicated in LTD that depolymerize postsynaptic F-actin disrupted AKAP-cadherin interactions and resulted in loss of the AKAP, but not cadherins, from synapses. This neuronal regulation of AKAP79/150 targeting to cadherins may be important in functional and structural synaptic modifications underlying plasticity.
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PMID:Association of an A-kinase-anchoring protein signaling scaffold with cadherin adhesion molecules in neurons and epithelial cells. 1593 Jan 26

In many non-excitable cells, the predominant mode of agonist-activated Ca(2+) entry switches from the arachidonic acid-regulated Ca(2+) (ARC) channels at low agonist concentrations, to store-operated channels at high concentrations. Underlying this process is the inhibition of the ARC channels by a calcineurin-mediated dephosphorylation, which inhibits the ability of arachidonic acid to activate the channels. Following such a dephosphorylation, we found that restoration of the sensitivity of the ARC channels to arachidonic acid, as well as to low concentrations of carbachol, was specifically dependent on protein kinase A (PKA) activity. Inhibition of protein kinase C, protein kinase G or calmodulin-activated kinase had no effect. This action of PKA was unaffected by prolonged intracellular dialysis, whilst disruption of the binding of PKA to A-kinase anchoring proteins (AKAPs) inhibited currents through ARC channels, and blocked the PKA-dependent effects. AKAP79, a protein which scaffolds both PKA and calcineurin, was shown to be present in the cells. These data illustrate the significance of PKA-dependent phosphorylation and calcineurin-dependent dephosphorylation in the overall regulation of ARC channel activity, and indicate the key role of an AKAP, possibly AKAP79, in the spatial organization these processes.
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PMID:Arachidonate-regulated Ca2+-selective (ARC) channel activity is modulated by phosphorylation and involves an A-kinase anchoring protein. 1599 85


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