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)

Incubation of rat glomerular mesangial cells with potent proinflammatory cytokines like interleukin 1beta, (IL- 1beta) triggers the expression of a non-pancreatic secretory phospholipase A2 (sPLA2) and increases the formation of prostaglandin E2. We show here that sPLA2 acts in an autocrine fashion on mesangial cells and induces a rapid activation of protein kinase C (PKC) isoenzymes delta and epsilon and of p42 mitogen-activated protein kinase (MAPK), two putative activators of cytosolic phospholipase A2 (cPLA2). sPLA2 also activates Raf-1 kinase in mesangial cells which integrates the signals coming from PKC for further processing along the MAPK cascade. Subsequently a phosphorylation and activation of cPLA2 is observed, thus arguing for a cross-talk between the two classes of PLA2. Pretreatment of cells with either the highly specific PKC inhibitor Ro-318220 or the highly specific MAPK kinase (MEK) inhibitor PD 98059 completely blocked the sPLA2-induced cPLA2 activation, indicating that both kinases are essential for the cross-talk between the two types of PLA2. The effect of sPLA2 is mimicked by lysophosphatidylcholine (LPC), a reaction product of sPLA2 activity. LPC stimulates PKC-epsilon, Raf-1 kinase and MAPK activation as well as cPLA2 activation with a subsequent increase in arachidonic acid release from mesangial cells. These data suggest that sPLA2 by cleaving membrane phospholipids and generating LPC and other lysophospholipids activates cPLA2 via the PKC/Raf-1/MAPK signalling pathway. Hence a network of interactions between different PLA2s is operative in mesangial cells and may contribute to the progression of glomerular inflammatory processes.
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PMID:Cross-talk between secretory phospholipase A2 and cytosolic phospholipase A2 in rat renal mesangial cells. 936 43

Apoptosis and survival of diverse cell types are under hormonal control, but intracellular mechanisms regulating cell death are unclear. The Bcl-2/Ced-9 family of proteins contains conserved Bcl-2 homology regions that mediate the formation of homo- or heterodimers important for enhancing or suppressing apoptosis. Unlike most other members of the Bcl-2 family, BAD (Bcl-xL/Bcl-2 associated death promoter), a death enhancer, has no C-terminal transmembrane domain for targeting to the outer mitochondrial membrane and nuclear envelope. We hypothesized that BAD, in addition to binding Bcl-xL and Bcl-2, may interact with proteins outside the Bcl-2 family. Using the yeast two-hybrid system to search for BAD-binding proteins in an ovarian fusion cDNA library, we identified multiple cDNA clones encoding different isoforms of 14-3-3, a group of evolutionally conserved proteins essential for signal transduction and cell cycle progression. Point mutation of BAD in one (S137A), but not the other (S113A), putative binding site found in diverse 14-3-3 interacting proteins abolished the interaction between BAD and 14-3-3 without affecting interactions between BAD and Bcl-2. Because the S137A BAD mutant presumably resembles an underphosphorylated form of BAD, we used this mutant to screen for additional BAD-interacting proteins in the yeast two-hybrid system. P11, a nerve growth factor-induced neurite extension factor and member of the calcium-binding S-100 protein family, interacted strongly with the mutant BAD but less effectively with the wild type protein. In Chinese hamster ovary (CHO) cells, transient expression of wild type BAD or its mutants increased apoptotic cell death, which was blocked by cotransfection with the baculovirus-derived cysteine protease inhibitor, P35. Cotransfection with 14-3-3 suppressed apoptosis induced by wild type or the S113A mutant BAD but not by the S137A mutant incapable of binding 14-3-3. Furthermore, cotransfection with P11 attenuated the proapoptotic effect of both wild type BAD and the S137A mutant. For both 14-3-3 and P11, direct binding to BAD was also demonstrated in vitro. These results suggest that both 14-3-3 and P11 may function as BAD-binding proteins to dampen its apoptotic activity. Because the 14-3-3 family of proteins could interact with key signaling proteins including Raf-1 kinase, protein kinase C, and phosphatidyl inositol 3 kinase, whereas P11 is an early response gene induced by the neuronal survival factor, nerve growth factor, the present findings suggest that BAD plays an important role in mediating communication between different signal transduction pathways regulated by hormonal signals and the apoptotic mechanism controlled by Bcl-2 family members.
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PMID:Interference of BAD (Bcl-xL/Bcl-2-associated death promoter)-induced apoptosis in mammalian cells by 14-3-3 isoforms and P11. 936 53

We investigated the activation of the Ras/ERK signaling pathway by 12-O-tetradecanoylphorbol-13-acetate (TPA) in NIH3T3 fibroblasts. Interestingly, the activation was suppressed not only by dominant negative Raf-1 but also by dominant negative Ras and SOS. Further analysis revealed that TPA treatment induced, dependently on protein kinase C, the mobility shift of p66(shc) in SDS-polyacrylamide gel electrophoresis, which could be prevented by treatment of the Shc immunoprecipitate with serine/threonine-specific protein phosphatase 1 (PP1) or 2A (PP2A). Phosphoamino acid analysis of Shc showed that unlike growth factor-induced Shc phosphorylation, where Shc is mainly phosphorylated at tyrosine residues, TPA-induced phosphorylation was only at serine residues. Like growth factor-induced Shc phosphorylation, which leads to the association of Shc with Grb2, TPA also induced this association, but, correspondingly to the above results, the TPA-induced association was disrupted by in vitro treatment of the Shc immunoprecipitate with PP1. Taken together, these results suggest that the TPA signal was fed at or upstream of Shc to activate the Ras/ERK signaling pathway involving serine phosphorylation of Shc.
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PMID:12-O-Tetradecanoylphorbol-13-acetate activates the Ras/extracellular signal-regulated kinase (ERK) signaling pathway upstream of SOS involving serine phosphorylation of Shc in NIH3T3 cells. 938 90

The GT1-1 GnRH neuronal cell lines exhibit highly differentiated properties of GnRH neurons. We have used GT1-1 cells to study the roles of norepinephrine (NE), membrane depolarization, calcium influx, and phorbol esters in the regulation of mitogen-activated protein (MAP) kinase. NE, which is known to stimulate the release of GnRH, induced MAP kinase activity, the tyrosine phosphorylation of MAP kinase, and MAP kinase kinase activity. Forskolin led to activation of MAP kinase comparable with that induced by NE, and a selective inhibitor of cAMP-dependent protein kinase, H8, attenuated the NE-induced activation of MAP kinase. On the other hand, elimination of extracellular calcium by EGTA completely blocked NE-induced tyrosine phosphorylation of MAP kinase, and a selective inhibitor of calcium/calmodulin-dependent protein kinase, KN-62, attenuated the NE-induced activation of MAP kinase. Furthermore, depolarization of GT1-1 cells with 75 mM KCl, 10 microM BayK 8644, or 1 microM calcium ionophore (A23187) induced rapid tyrosine phosphorylation of MAP kinase. The omission of calcium from the extracellular medium completely abolished these effects of tyrosine phosphorylation of MAP kinase. Phorbol 12-myristate 13-acetate (PMA) also induced MAP kinase activity, but pretreatment of the cultured cells with PMA to down-regulate protein kinase C did not abolish the activation of MAP kinase by NE. In addition, although phosphorylation of Raf-1 kinase was stimulated by PMA, this phosphorylation was not induced by either NE or A23187. These results demonstrate that NE activates MAP kinase directly in GT1-1 cells, and that the effect of NE is mediated by increase in the cAMP level and by calcium influx, but not by PMA-sensitive protein kinase C or Raf-1 kinase.
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PMID:Norepinephrine stimulates mitogen-activated protein kinase activity in GT1-1 gonadotropin-releasing hormone neuronal cell lines. 938 11

The signaling pathway involved in low density lipoprotein (LDL) receptor gene expression induced by the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) was investigated in the human hepatoma HepG2 cell line. Treatment of HepG2 cells with 100 nM TPA resulted in an approximately 20-fold increase in LDL receptor mRNA level, as determined by RT-PCR, which peaked at 2-4 h of treatment and subsequently declined. The protein kinase C (PKC) inhibitors calphostin C and staurosporine prevented TPA-mediated LDL receptor mRNA induction. In contrast, TPA did not affect squalene synthase mRNA expression. Immunoblotting of cell extracts with isozyme-specific PKC antibodies revealed that HepG2 cells expressed PKC alpha, which was mainly cytosolic, and PKC beta, PK epsilon, and PKC zeta, all of which were present in both the cytosolic and particulate fractions. Treatment of HepG2 cells with 100 nM TPA resulted in translocation of cytosolic PKC alpha to the particulate fraction, with a maximum at 30 min-2 h of treatment, but was without effect on the subcellular distribution of the other isozymes. TPA treatment also led to activation of the mitogen-activated protein kinase (MAPK) ERK cascade. The specific MAPK pathway inhibitor PD98059 blocked TPA-induced ERK activation. Furthermore, pretreatment of cells with PD98059 inhibited TPA-induced LDL receptor mRNA induction. Moreover, pretreatment of cells with calphostin C inhibited TPA-mediated ERK activation and LDL receptor mRNA induction in a dose-dependent fashion. Based on a close kinetic correlation between PKC alpha translocation and ERK activation, and the effects of specific inhibitors, these findings suggest that translocation/activation of PKC alpha, and subsequent activation of the Raf-1/MEK/ERK MAPK cascade, represent key events in the transcriptional induction of LDL receptor gene by TPA in HepG2 cells.
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PMID:Phorbol ester-induced low density lipoprotein receptor gene expression in HepG2 cells involves protein kinase C-mediated p42/44 MAP kinase activation. 939 22

Several observations indicate that the Raf-1 kinase is a downstream effector of protein kinase C-epsilon (PKC epsilon). We recently have shown that Raf-1 is constitutively activated in PKC epsilon transformed Rat6 fibroblasts, and transformation can be reverted by expression of a dominant negative Raf-1, but not a dominant negative Ras mutant (Cacace et al., 1996). Cai et al. (1997) demonstrated that PKC epsilon induced proliferation of NIH3T3 cells is independent of Ras or Src, but depends on Raf-1. These authors further suggested that PKC epsilon activates Raf-1 by direct phosphorylation. Here we have investigated the functional interaction between PKC epsilon and Raf-1. PKC epsilon, but not PKC alpha, was found to bind to the Raf-1 kinase domain. The association appeared to be direct, as it could be reconstituted in vitro with purified proteins. Raf-1 and PKC epsilon could be co-precipitated from Sf-9 insect cells and PKC epsilon transformed NIH313 cells (NIH/epsilon). The association was negatively regulated by ATP in vitro and by TPA treatment in NIH/epsilon cells, but not in Sf-9 insect cells. Raf-1 was constitutively activated in NIH/epsilon cells. However, using coexpression experiments in Sf-9 cells and transiently transfected A293 cells we did not obtain any evidence for a direct activation of Raf-1 by PKC epsilon. PKC epsilon did not induce translocation of Raf-1 to the membrane. Furthermore, PKC epsilon did not activate Raf-1 nor enhance the kinase activity of Raf-1 that had been pre-activated by coexpression of Ras or the Lck tyrosine kinase. In contrast, conditioned media from PKC epsilon transformed cells induced a robust activation of Raf-1. This activation could be partially reproduced by recombinant TGFbeta, a growth factors secreted by PKC epsilon transformed Rat6 cells. In conclusion, our results suggest that PKC epsilon stimulates Raf-1 indirectly by inducing the production of autocrine growth factors.
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PMID:Protein kinase C-epsilon associates with the Raf-1 kinase and induces the production of growth factors that stimulate Raf-1 activity. 941 35

Eosinophils are potent effector cells contributing to allergic inflammation and asthma. The differentiation, recruitment, and effector functions of eosinophils are greatly affected by interleukin (IL)-5. In the eosinophil, signal transduction pathways including Jak-STAT and Ras-Raf-MAP kinase are stimulated by IL-5 and enzymatic activation of tyrosine kinases Jak-2 and Lyn has been demonstrated. The participation of adapter proteins in the responses of the Ras-Raf-MAP kinase pathway has been documented in many cytokine family receptors but the expression and activation of these proteins have not been demonstrated in eosinophils. In these studies, we have found three isoforms of the adapter protein, Shc, to be expressed in eosinophils. One of these isoforms, p52 Shc, was tyrosine phosphorylated following IL-5 treatment of eosinophils. A second adapter protein, Grb2, coimmunoprecipitated with Shc following IL-5 stimulation of eosinophils. Furthermore, p52 Shc was increasingly associated with a cell fraction resistant to detergent solubilization, following IL-5 administration. This cell fraction of limited detergent solubility is a complex mixture of proteins and the adapter protein Grb2, the tyrosine kinases Jak-2 and Lyn, the nucleotide exchange factor Vav, and the serine-threonine kinases p45 MAP kinase, Raf-1, and PKCbeta, were distributed either wholly or partially in the same fraction, as were the cytoskeletal proteins actin and vimentin. Only p52 Shc, however, demonstrated discernibly increased association with this fraction following IL-5 stimulation of eosinophils. These data suggest that IL-5 activates a signal transduction pathway utilizing the adapter proteins Shc and Grb2 in the human eosinophil.
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PMID:Interleukin 5 signals through Shc and Grb2 in human eosinophils. 944 48

Leukotriene D4 (LTD4) is a major lipid mediator involved in inflammatory and allergic disorders including bronchial asthma. Despite its potent biological activity, little is known about the receptor and intracellular signaling pathways. Here we analyzed the signal transduction mechanisms through LTD4 receptors using human monocytic leukemia THP-1 cells. When these cells were stimulated with LTD4, intracellular calcium concentration was increased and mitogen-activated protein kinase (MAP kinase) was activated severalfold. This activation was inhibited by staurosporine or GF109203X treatment or abolished by protein kinase C depletion. Cytosolic protein kinase Calpha was translocated to the membrane, and Raf-1 was activated by LTD4 treatment in a similar time course. LTD4-induced Raf-1 activation was diminished by protein kinase C depletion in the cells. A chemotactic response of THP-1 cells toward LTD4 was observed which was inhibited by pertussis toxin (PTX) pretreatment. Thus, LTD4 has at least two distinct signaling pathways in THP-1 cells, a PTX-insensitive mitogen-activated protein kinase activation through protein kinase Calpha and Raf-1 and a PTX-sensitive chemotactic response. This cellular signaling can explain in part the versatile activities of LTD4 in macrophages under inflammatory and allergic conditions.
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PMID:Leukotriene D4 activates mitogen-activated protein kinase through a protein kinase Calpha-Raf-1-dependent pathway in human monocytic leukemia THP-1 cells. 947 29

Angiotensin II (Ang II) induces hypertrophy of cardiac myocytes and hyperplasia of cardiac fibroblasts. To determine the molecular mechanism by which Ang II displayed different effects on cardiac myocytes and fibroblasts, we examined signal transduction pathways leading to activation of extracellular signal-regulated kinases (ERKs). Ang II-induced ERK activation was abolished by pretreatment with pertussis toxin and by overexpression of the Gbetagamma subunit-binding domain of the beta-adrenergic receptor kinase 1 in cardiac fibroblasts but not in cardiac myocytes. Inhibition of protein kinase C strongly inhibited activation of ERKs by Ang II in cardiac myocytes, whereas inhibitors of tyrosine kinases but not of protein kinase C abolished Ang II-induced ERK activation in cardiac fibroblasts. Overexpression of C-terminal Src kinase (Csk), which inactivates Src family tyrosine kinases, suppressed the activation of transfected ERK in cardiac fibroblasts. Ang II rapidly induced phosphorylation of Shc and association of Shc with Grb2. Cotransfection of the dominant-negative mutant of Ras or Raf-1 kinase abolished Ang II-induced ERK activation in cardiac fibroblasts. Overexpression of Csk or the dominant-negative mutant of Ras had no effects on Ang II-induced ERK activation in cardiac myocytes. These findings suggest that Ang II-evoked signal transduction pathways differ among cell types. In cardiac fibroblasts, Ang II activates ERKs through a pathway including the Gbetagamma subunit of Gi protein, tyrosine kinases including Src family tyrosine kinases, Shc, Grb2, Ras, and Raf-1 kinase, whereas Gq and protein kinase C are important in cardiac myocytes.
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PMID:Cell type-specific angiotensin II-evoked signal transduction pathways: critical roles of Gbetagamma subunit, Src family, and Ras in cardiac fibroblasts. 948 62

Erythropoietin (EPO) is a hormone, as well as a hematopoietic growth factor, that specifically regulates the proliferation and differentiation of erythroid progenitor cells. Although the membrane-bound receptor for EPO has no intrinsic kinase activity, it triggers the activation of protein kinases via phospholipases A2, C, and D. A cascade of serine and threonine kinases, including Raf-1, MAP kinase and protein kinase C (PKC) is activated following tyrosine phosphorylation. In this study, we have examined whether changes in nuclear PKC and 1,2-diacylglycerol (DAG) are induced following EPO treatment of the murine target cell line, B6SUt.EP. Western blot analysis using isoform-specific antibodies demonstrated the presence of PKC beta II, but not PKC alpha, beta I, gamma, epsilon, delta, eta, or zeta in the nuclei of cells stimulated with EPO. The increase in nuclear beta II levels was accompanied by an immediate rise in DAG mass levels with both of the increases peaking by 1 min. These rapid increases in nuclear DAG and PKC beta II expression suggest a mechanism for EPO-induced changes in gene expression necessary for cell proliferation.
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PMID:Erythropoietin stimulates nuclear localization of diacylglycerol and protein kinase C beta II in B6SUt.EP cells. 952 23


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