Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Par (partitioning-defective) genes were originally identified in Caenorhabditis elegans as determinants of anterior/posterior polarity. However, neither their function in vertebrate development nor their action mechanism has been fully addressed. Here we show that two members of Par proteins, 14-3-3 (Par-5) and atypical PKC (aPKC), regulate the serine/threonine kinase Par-1 to control Xenopus gastrulation. We find first that Xenopus Par-1 (xPar-1) is essential for gastrulation but not for cell fate specification during early embryonic development. We then find that xPar-1 binds to 14-3-3 in an aPKC-dependent manner. Our analyses identify two aPKC phosphorylation sites in xPar-1, which are essential for 14-3-3 binding and for proper gastrulation movements. The aPKC phosphorylation-dependent binding of xPar-1 to 14-3-3 does not markedly affect the kinase activity of xPar-1, but induces relocation of xPar-1 from the plasma membranes to the cytoplasm. Finally, we show that Xenopus aPKC and its binding partner Xenopus Par-6 are also essential for gastrulation. Thus, our results identify a requirement of Par proteins for Xenopus gastrulation and reveal a novel interrelationship within Par proteins that may provide a general mechanism for spatial control of Par-1.
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PMID:The polarity-inducing kinase Par-1 controls Xenopus gastrulation in cooperation with 14-3-3 and aPKC. 1534 71

Exposure of 3T3/A31 cells to serum-free medium, one type of apoptotic stimulus, causes a rapid increase in the sphingosine (Sph) level, which initiates a series of processes: (i) activation of caspase 3 through an enhanced "cascade" of caspases, (ii) release of the C-terminal-half kinase domain of PKCdelta (PKCdelta KD) by caspase 3, and (iii) activation of Sph-dependent kinase 1 (SDK1), which was previously identified as PKCdelta KD. The activation of caspase 3 and release of PKCdelta KD are inhibited strongly by the incubation of cells with the ceramidase inhibitor D-erythro-2-tetradecanoylamino-1-phenyl-1-propanol and, to a much lesser extent, by L-cycloserine, an inhibitor of de novo ceramide synthesis. Exogenous addition of Sph or N,N-dimethyl-Sph to U937 cells causes caspase 3 activation and release of PKCdelta KD (SDK1), leading to apoptosis. The Sph-induced apoptotic process associated with activation of caspase 3 and release of PKCdelta KD (SDK1) may promote the proapoptotic effect of BAD or BAX through an increase of phosphorylated 14-3-3. In addition, Sph induces apoptosis through a separate process: the blocking of "survival signal" through the Akt kinase pathway induced by alpha3beta1-mediated cell adhesion to laminin 10/11 in extracellular matrix. We hereby propose a unified concept of Sph-dependent apoptosis based on these multiple mechanisms operating in concert.
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PMID:Sphingosine-dependent apoptosis: a unified concept based on multiple mechanisms operating in concert. 1546

Mammalian Par3alpha and Par3beta/Par3L participate in cell polarity establishment and localize to tight junctions of epithelial cells; Par3alpha acts via binding to atypical PKC (aPKC). Here we show that Par3beta as well as Par3alpha interacts with 14-3-3 proteins in a phosphorylation-dependent manner. In the interaction, Ser-746 of Par3beta and the corresponding residue of Par3alpha (Ser-814) likely play a crucial role, since replacement of these residues by unphosphorylatable alanine results in a loss of interacting activity. The mutant Par3 proteins with the replacement are correctly recruited to tight junctions of MDCK cells and to membrane ruffles induced by an active form of the small GTPase Rac in HeLa cells. Thus, the interaction with 14-3-3 appears to be dispensable to Par3 localization. Consistent with this, the Par3alpha-14-3-3 interaction does not inhibit the Par3alpha-aPKC association required for the Par3alpha localization, although the aPKC-binding site lies close to the Ser-814-containing, 14-3-3-interacting region.
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PMID:Phosphorylation-dependent binding of 14-3-3 to Par3beta, a human Par3-related cell polarity protein. 1572 Dec 95

Although both tumor necrosis factor (TNF) and H2O2 induce activation of c-Jun N-terminal kinase (JNK) kinase cascades, it is not known whether they utilize distinct intracellular signaling pathways. In this study, we first examined a variety of pharmacological inhibitors on TNF and H2O2-induced JNK activation. Go6983 or staurosporine, which inhibits protein kinase C isoforms had no effects on TNF or H2O2-induced JNK activation. However, Go6976 and calphostin, which can inhibit protein kinase C as well as protein kinase D (PKD), blocked H2O2- but not TNF-induced JNK activation, suggesting that PKD may be specifically involved in H2O2-induced JNK activation. Consistently, H2O2, but not TNF, induced phosphorylation of PKD and translocation of PKD from endothelial cell membrane to cytoplasm where it associates with the JNK upstream activator, apoptosis signal-regulating kinase 1 (ASK1). The association is mediated through the pleckstrin homology domain of PKD and the C-terminal domain of ASK1. Inhibition of PKD by Go6976 or by small interfering RNA of PKD blocked H2O2-induced ASK1-JNK activation and endothelial cell apoptosis. Interestingly, H2O2 induced 14-3-3 binding to PKD via the phospho-Ser-205/208 and phospho-Ser-219/223 and H2O2-induced 14-3-3 binding of PKD was specifically blocked by Go6976 but not by Go6983. More significantly, the 14-3-3-binding defective forms of PKD failed to associate with ASK1 and to activate JNK signaling, highlighting the importance of 14-3-3 binding of PKD in H2O2-induced activation of ASK1-JNK cascade. Thus, our data have identified PKD as a critical mediator in H2O2- but not TNF-induced ASK1-JNK signaling.
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PMID:Protein kinase D specifically mediates apoptosis signal-regulating kinase 1-JNK signaling induced by H2O2 but not tumor necrosis factor. 1575 22

Diabetic cardiomyopathy is associated with cardiac hypertrophy and fibrosis. Activation of protein kinase C (PKC) has been implicated in the diabetes-induced cardiovascular complications. PKCbeta2 isoform is preferentially found to be activated in the diabetic myocardium. However, the role of PKCbeta2 in diabetic cardiomyopathy is not clear. 14-3-3 family members are dimeric phosphoserine-binding proteins that regulate signal transduction, apoptotic and checkpoint control pathways, and have been shown to bind with PKC isozymes and negatively regulate their enzymatic activities. The present study tests whether 14-3-3 protein regulates cardiac hypertrophy and fibrosis in streptozotocin (STZ)-induced diabetic mice, using transgenic mice with cardiac specific over-expression of dominant negative (DN) 14-3-3 protein. In addition, we examined the relationship between 14-3-3 protein and PKCbeta2 in the diabetic myocardium. Cardiac myocyte diameter, content of cardiac fibrosis, left ventricular tissue expressions of atrial natriuretic peptide, transforming growth factor beta1, collagen III and PKCbeta2 were significantly elevated 28 and 56 d after STZ injection in transgenic DN-14-3-3 mice, when compared to their non-transgenic counterparts. These results clearly demonstrate that the functional inactivation of 14-3-3 protein in DN-14-3-3 mice exacerbates diabetes-induced cardiac hypertrophy and fibrosis. The exacerbations of cardiac hypertrophy and fibrosis were significantly and positively correlated with the enhanced expression of PKCbeta2 in DN-14-3-3 mice. Our results indicate for the first time that 14-3-3 protein negatively regulates cardiac hypertrophy and fibrosis, possibly through controlling the expression of PKCbeta2 in the diabetic myocardium.
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PMID:Inactivation of 14-3-3 protein exacerbates cardiac hypertrophy and fibrosis through enhanced expression of protein kinase C beta 2 in experimental diabetes. 1593 Jul 26

PDE3A (phosphodiesterase 3A) was identified as a phosphoprotein that co-immunoprecipitates with endogenous 14-3-3 proteins from HeLa cell extracts, and binds directly to 14-3-3 proteins in a phosphorylation-dependent manner. Among cellular stimuli tested, PMA promoted maximal binding of PDE3A to 14-3-3 proteins. While p42/p44 MAPK (mitogen-activated protein kinase), SAPK2 (stress-activated protein kinase 2)/p38 and PKC (protein kinase C) were all activated by PMA in HeLa cells, the PMA-induced binding of PDE3A to 14-3-3 proteins was inhibited by the non-specific PKC inhibitors Ro 318220 and H-7, but not by PD 184352, which inhibits MAPK activation, nor by SB 203580 and BIRB0796, which inhibit SAPK2 activation. Binding of PDE3A to 14-3-3 proteins was also blocked by the DNA replication inhibitors aphidicolin and mimosine, but the PDE3A-14-3-3 interaction was not cell-cycle-regulated. PDE3A isolated from cells was able to bind to 14-3-3 proteins after in vitro phosphorylation with PKC isoforms. Using MS/MS of IMAC (immobilized metal ion affinity chromatography)-enriched tryptic phosphopeptides and phosphospecific antibodies, at least five sites on PDE3A were found to be phosphorylated in vivo, of which Ser428 was selectively phosphorylated in response to PMA and dephosphorylated in cells treated with aphidicolin and mimosine. Phosphorylation of Ser428 therefore correlated with 14-3-3 binding to PDE3A. Ser312 of PDE3A was phosphorylated in an H-89-sensitive response to forskolin, indicative of phosphorylation by PKA (cAMP-dependent protein kinase), but phosphorylation at this site did not stimulate 14-3-3 binding. Thus 14-3-3 proteins can discriminate between sites in a region of multisite phosphorylation on PDE3A. An additional observation was that the cytoskeletal cross-linker protein plectin-1 coimmunoprecipitated with PDE3A independently of 14-3-3 binding.
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PMID:Phosphodiesterase 3A binds to 14-3-3 proteins in response to PMA-induced phosphorylation of Ser428. 1615 82

Protein kinase C (PKC)-alpha exerts a regulatory function on insulin action. We showed by overlay blot that PKCalpha directly binds a 180-kDa protein, corresponding to IRS-1, and a 30-kDa molecular species, identified as 14-3-3epsilon. In intact NIH-3T3 cells overexpressing insulin receptors (3T3-hIR), insulin selectively increased PKCalpha co-precipitation with IRS-1, but not with IRS-2, and with 14-3-3epsilon, but not with other 14-3-3 isoforms. Overexpression of 14-3-3epsilon in 3T3-hIR cells significantly reduced IRS-1-bound PKCalpha activity, without altering IRS-1/PKCalpha co-precipitation. 14-3-3epsilon overexpression also increased insulin-stimulated insulin receptor and IRS-1 tyrosine phosphorylation, followed by increased activation of Raf1, ERK1/2, and Akt/protein kinase B. Insulin-induced glycogen synthase activity and thymidine incorporation were also augmented. Consistently, selective depletion of 14-3-3epsilon by antisense oligonucleotides caused a 3-fold increase of IRS-1-bound PKCalpha activity and a similarly sized reduction of insulin receptor and IRS-1 tyrosine phosphorylation and signaling. In turn, selective inhibition of PKCalpha expression by antisense oligonucleotides reverted the negative effect of 14-3-3epsilon depletion on insulin signaling. Moreover, PKCalpha inhibition was accompanied by a >2-fold decrease of insulin degradation. Similar results were also obtained by overexpressing 14-3-3epsilon. Thus, in NIH-3T3 cells, insulin induces the formation of multimolecular complexes, including IRS-1, PKCalpha, and 14-3-3epsilon. The presence of 14-3-3epsilon in the complex is not necessary for IRS-1/PKCalpha interaction but modulates PKCalpha activity, thereby regulating insulin signaling and degradation.
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PMID:Protein kinase C-alpha regulates insulin action and degradation by interacting with insulin receptor substrate-1 and 14-3-3 epsilon. 1621 80

Proliferation in cardiac fibroblasts (CFs) can be induced by a wide variety of growth factors that recruit multiple signal transduction pathways, including mitogen-activated protein kinase, phosphatidylinositol 3-kinase and protein kinase C. As a family of dimeric phophoserine-binding proteins, 14-3-3s are associated with a multitude of proteins that regulate signal transduction, apoptosis and checkpoint control pathways. However, it remains unknown whether the 14-3-3 proteins play an active role in cardiac proliferation and alter their expression patterns in response to growth factors in CFs. R18 peptide, an isoform-independent 14-3-3 inhibitor, was used to disrupt 14-3-3 function by adenovirus-mediated transfer of R18-EYFP (AdR18). Our results demonstrate that the 14-3-3 isoforms gamma, zeta and epsilon were highly expressed in CFs and the expression of 14-3-3 epsilon was elevated following serum stimulation. Inhibition of 14-3-3 proteins by AdR18 potentiated mitogen-induced DNA synthesis in CFs. This potentiation was presumably due to the increased inactivated glycogen synthase kinase-3 beta by Ser9 phosphorylation and nuclear factor of activated T-cell nuclear accumulation. However, AdR18 had no effect on extracellular signal-regulated kinase phosphorylation and reduced p70 S6 kinase (p70S6K) phosphorylation upon mitogenic stimulation. Furthermore, though R18 can block 14-3-3 binding abilities, it did not affect the serum-induced upregulation of 14-3-3 epsilon protein. Collectively, these findings reveal that the expression of 14-3-3 epsilon can be upregulated by serum in CFs and 14-3-3s may exert an inhibitory effect on serum-induced proliferation.
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PMID:Inhibitory effect of 14-3-3 proteins on serum-induced proliferation of cardiac fibroblasts. 1627 Jul 52

Stannin (Snn) was discovered using subtractive hybridization methodology designed to find gene products related to selective organotin toxicity and apoptosis. The cDNAs for Snn were first isolated from brain tissues sensitive to trimethyltin, and were subsequently used to localize, characterize, and identify genomic DNA, and other gene products of Snn. Snn is a highly conserved, 88 amino acid protein found primarily in vertebrates. There is a minor divergence in the C-terminal sequence between amphibians and primates, but a nearly complete conservation of the first 60 residues in all vertebrates sequenced to date. Snn is a membrane-bound protein and is localized, in part, to the mitochondria and other vesicular organelles, suggesting that both localization and conservation are significant for the overall function of the protein. The structure of Snn in a micellar environment and its architecture in lipid bilayers have been determined using a combination of solution and solid-state NMR, respectively. Snn structure comprised a single transmembrane domain (residues 10-33), a 28-residue linker region from residues 34-60 that contains a conserved CXC metal binding motif and a putative 14-3-3xi binding region, and a cytoplasmic helix (residues 61-79), which is partially embedded into the membrane. Of primary interest is understanding how this highly-conserved peptide with an interesting structure and cellular localization transmits both normal and potentially toxic signals within the cell. Evidence to date suggests that organotins such as trimethyltin interact with the CXC region of Snn, which is vicinal to the putative 14-3-3 binding site. In vitro transfection analyses and microarray experiments have inferred a possible role of Snn in several key signaling systems, including activation of the p38-ERK cascade, p53-dependent pathways, and 14-3-3xi protein-mediated processes. TNFalpha can induce Snn mRNA expression in endothelial cells in a PKC-epsilon dependent manner. Studies with Snn siRNA suggest that this protein may be involved in growth regulation, since inhibition of Snn expression alone leads to reduced endothelial cells growth and induction of COP-1, a negative regulator of p53 function. A key piece of the puzzle, however, is how and why such a highly-conserved protein, localized to mitochondria, interacts with other regulatory proteins to alter growth and apoptosis. By knowing the structure, location, and possible signaling pathways involved, we propose that Snn constitutes an important sensor of mitochondrial damage, and plays a key role in the mediation of cross-talk between mitochondrial and nuclear compartments in specific cell types.
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PMID:Functional and structural properties of stannin: roles in cellular growth, selective toxicity, and mitochondrial responses to injury. 1645 79

Glycogen synthase kinase (GSK) 3beta is a multifunctional protein that positively regulates myocardial apoptosis and negatively regulates hypertrophy. However, the role of GSK3beta in the diabetic myocardium is largely unknown. We found that GSK3beta became more active (less phosphorylated at serine 9) via decreased Akt phosphorylation, in parallel to c-Jun NH2 terminal kinase activation, which correlated with increased activated caspase 3 and myocardial apoptosis 3 days after streptozotocin (STZ) injection in mice. However, 28 days after STZ injection, GSK3beta became inactive, which correlated with the enhanced protein kinase C beta2 and p38 mitogen activated protein kinase expression, nuclear translocation of nuclear factor of activated T cells c3, cardiac hypertrophy and fibrosis. All of the above parameters were exacerbated in dominant-negative 14-3-3 transgenic mice. Our results suggest that GSK3beta together with 14-3-3 protein plays essential roles in the signaling of diabetic cardiomyopathy, and treatment with either losartan or tempol prevents these changes.
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PMID:Glycogen synthase kinase 3beta together with 14-3-3 protein regulates diabetic cardiomyopathy: effect of losartan and tempol. 1653 Jan 86


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