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

We examined the role of the platelet product ATP in regulating replication and secretory activity of cultured rat mesangial cells (MCs). Extracellular ATP (25-100 microM) significantly increased [3H]thymidine uptake of growth-arrested MCs 2.1-fold; cell counts increased by 35.1%. Addition of ATP to MCs in combination with other platelet products, such as platelet-derived growth factor, isoform BB (100 ng/ml), and serotonin (1 microM), resulted in strong synergistic mitogenicity (up to 45.6-fold over control). As immediate signaling events following stimulation with ATP, we found increased production of inositol phosphates (3.2-fold increase for inositol bisphosphate and 1.6-fold increase for inositol trisphosphate by 30 s) and release of prostaglandin E2 (PGE2, 9.2-fold increase by 5 min). When we studied the rank order of potency of various ATP analogues for the production of inositol phosphates and PGE2, ATP, UTP, and adenosine 5'-O-(3-thio)triphosphate (ATP gamma S) were the most potent agonists. Although ATP and ATP gamma S were also strong mitogens, UTP was not. Additional inhibitor studies indicated that protein kinase C or cyclooxygenase products were not involved in the mitogenic effects of ATP. In summary, the major platelet product ATP is a potent comitogen for cultured MCs and strongly synergizes with other growth factors. The experiments with ATP analogues point to different receptors mediating mitogenesis, generation of inositol phosphates, and PGE2 production. The precise mechanism of the mitogenic action of ATP on MCs remains to be characterized.
Am J Physiol 1992 Sep
PMID:Extracellular ATP stimulates proliferation of cultured mesangial cells via P2-purinergic receptors. 141 66

Neutrophils from newborn calves have been shown to be deficient in ability to generate superoxide anion (O2-) after stimulation of the respiratory burst enzyme with the phorbol ester, phorbol 12-myristate 13-acetate (PMA). This compound activates the O(2-)-generating enzyme of bovine neutrophils through a pathway involving protein kinase C (PKC). To investigate the biochemical basis underlying this functional difference between neutrophils from newborn and adult cattle, we measured and compared the activity of the enzyme PKC in nonstimulated and PMA-stimulated bovine neutrophils. Neutrophils from newborn calves (n = 5) and adult cows (n = 5) were stimulated with various concentrations of PMA (0, 10, 100, and 500 ng/ml) for 3 minutes, and PKC activity was assayed in the cytosolic and the membrane fractions. In nonstimulated cells, most PKC activity was detected in the cytosolic fraction of neutrophils from newborn and adult cattle. Activity of PKC in the cytosol was dependent on the presence of added calcium and phospholipids, whereas membrane-associated PKC in nonstimulated cells did not have such dependence. Significant differences in PKC activity were not observed between newborn and adult cattle in either the cytosolic or the membrane fractions from nonstimulated cells. Stimulation with PMA caused redistribution of PKC activity in the cell (translocation) in newborns and adults, consisting of decrease in cytosolic PKC activity and increase in membrane-associated PKC activity. Similar to that in nonstimulated cells, PKC activity in cytosolic fractions from PMA-stimulated neutrophils was dependent on the presence of cofactors (calcium and phospholipids), whereas PKC activity in the membrane did not have such requirement.(ABSTRACT TRUNCATED AT 250 WORDS)
Am J Vet Res 1992 Sep
PMID:Protein kinase-C activity in phorbol myristate acetate-stimulated neutrophils from newborn and adult cattle. 141 76

This enzyme activity was examined in bone cells cultured for 8-10 days; the calcium concentration was 1.87 +/- 0.05 (n = 10) mM in the control medium and 0.34 +/- 0.02 (n = 10) mM in the low-calcium medium. The activity was significantly lower in the low-calcium group than in the control (p less than 0.01). The cytosolic fraction decreased more than the membranous fraction. After restoration to a regular calcium environment, the protein kinase C activity recovered rapidly to near the control value. The extent of recovery was greater in the membranous than in the cytosolic fraction. These results suggest that the enzyme was inhibited in bone cells placed in a low-calcium environment, while the sensitivity in the membrane was enhanced.
Arch Oral Biol 1992 Sep
PMID:Changes in protein kinase C activity in rat calvarial bone cells cultured in a low-calcium environment. 141 20

The roles of protein kinase C (PKC) and Exo1 in exocytosis from digitonin-permeabilized adrenal chromaffin cells were explored by using exogenous purified proteins in a run-down/reconstitution system. The stimulatory action of Exo1 on exocytosis from run-down cells was found to be completely dependent on the continuous presence of exogenous MgATP, suggesting that it acts on the slow phase of exocytosis [Holz, Bittner, Peppers, Senter & Eberhard (1989), J. Biol. Chem. 264, 5412-5419]. Partially purified rat brain PKC was found to be able to stimulate Ca(2+)-dependent exocytosis from run-down cells in a dose-dependent manner. This effect was indeed due to PKC and not a contaminant in the PKC fraction, since the PKC activator phorbol 12-myristate 13-acetate (PMA), under conditions in which control secretion was not affected, potentiated the effect of the exogenous PKC in stimulating secretion. Furthermore, although either PKC or Exo1 alone could stimulate exocytosis from run-down cells, the effect of combining the fractions was synergistic, as had previously been observed using PMA treatment combined with Exo1 incubation [Morgan & Burgoyne (1992) Nature (London) 355, 833-836]. The observed synergy between PKC and Exo1 was not due to PKC-mediated phosphorylation of Exo1, and Exo1 was found not to affect PKC activity in enzyme assays. We conclude that PKC and Exo1 act synergistically in the slow phase of Ca(2+)-dependent exocytosis from adrenal chromaffin cells. Furthermore, PKC does not directly affect Exo1, but rather enhances the activity of Exo1 by a putative phosphorylation of another, unidentified, component of the exocytotic machinery which facilitates the action of Exo1 in exocytosis.
Biochem J 1992 Sep 15
PMID:Interaction between protein kinase C and Exo1 (14-3-3 protein) and its relevance to exocytosis in permeabilized adrenal chromaffin cells. 141 40

The U937 human monocyte-macrophage cell line was used to examine the effect of thrombin, an ill-defined chemoattractant, on the polymerization of actin, a process essential for cell motility. In differentiated macrophage-like U937 cells, thrombin (0.5-50 units/ml) caused a rapid dose-dependent increase in the formation of filamentous (F-) actin, detected by the staining of F-actin with the fluorescent toxin, 7-nitrobenz-2-oxa-1,3-diazole-phallacidin. In contrast with other chemoattractants such as N-formylmethionyl-leucylphenylalanine or C5a, actin polymerization in response to thrombin occurred via a pertussis-toxin-insensitive G1-(inhibitory G-protein) independent signalling pathway. Further, this response was not affected by the Ca2+ chelator EGTA or by the specific protein kinase C (PKC) inhibitor RO-31-8220. The response to thrombin was not mimicked by the Ca2+ ionophore ionomycin or by the direct PKC activator phorbol 12-myristate 13-acetate. The thrombin response was, however, inhibited by the non-specific protein kinase inhibitor staurosporine. The present results suggest that in U937 cells thrombin stimulates the formation of F-actin via a signalling pathway independent of (i) the activation of PKC, (ii) the mobilization of intracellular Ca2+ and (iii) the activation of Ca(2+)-dependent protein kinases, but dependent on the activation of an undefined staurosporine-sensitive protein kinase.
Biochem J 1992 Sep 15
PMID:Thrombin promotes actin polymerization in U937 human monocyte-macrophage cells. Analysis of the signalling mechanisms mediating actin polymerization. 141 54

The 39-43 residue polypeptide (amyloid beta protein, beta A4) deposited as amyloid in Alzheimer's disease (AD) is derived from a set of 695-770 residue precursors referred to as the amyloid beta A4 protein precursor (beta APP). In each of the 695, 751, and 770 residue precursors, the 43 residue beta A4 is an internal peptide that begins 99 residues from the COOH-terminus of the beta APP. Each holoform is normally cleaved within the beta A4 to produce a large secreted derivative as well as a small membrane associated fragment. Neither of these derivatives can produce amyloid because neither contains the entire beta A4 peptide. In this study, we employ cells stably transfected with full length beta APP695, beta APP751, or beta APP770 expression constructs to show that phorbol ester activation of protein kinase C substantially increases the production of secreted forms from each isoform. By increasing processing of beta APP in the secretory pathway, PKC phosphorylation may help to prevent amyloid deposition.
Biochem Biophys Res Commun 1992 Sep 30
PMID:Secretory processing of the Alzheimer amyloid beta/A4 protein precursor is increased by protein phosphorylation. 141 5

Incubation of purified protein kinase C with H2O2 results in the generation of a persistently activated form of the enzyme which is no longer dependent on Ca2+ or lipid cofactors. This oxidative activation of purified protein kinase C requires added Fe2+ in the incubation medium. Treatment of the soluble fraction of hippocampal homogenates with H2O2 also leads to persistent activation of protein kinase C; however, oxidative activation of protein kinase C under these conditions does not require the addition of Fe2+. The persistently activated form of protein kinase C appears as a novel peak of activity on DE52 anion exchange columns, suggesting a modification of the charge character of the enzyme. Thus, oxidative modification of protein kinase C can result in its persistent activation, and this mechanism may constitute a pathway for physiological activation of the enzyme in the hippocampus.
Biochem Biophys Res Commun 1992 Sep 30
PMID:Oxidation-induced persistent activation of protein kinase C in hippocampal homogenates. 141 20

The addition of granulocyte-macrophage colony-stimulating factor (GM-CSF) to human peripheral blood neutrophils primes phospholipase D (PLD) to subsequent stimulation by N-formyl-methionyl-leucyl-phenylalanine (fMLP) or phorbol myristate acetate (PMA). The present investigation was directed at the elucidation of the pathway(s) involved in the regulation of the activity of PLD in untreated as well as in GM-CSF-primed neutrophils. Pretreatment with pertussis toxin (PT) totally inhibited fMLP-induced activation of PLD in control or GM-CSF-treated cells. PT did not affect the activation of PLD by PMA but inhibited the priming effect of GM-CSF. Activation of PLD by fMLP was dose-dependently inhibited by erbstatin, an inhibitor of tyrosine kinases. Furthermore, pre-incubation with GM-CSF accelerated the tyrosine phosphorylation response to fMLP (as analysed by protein immunoblot with antiphosphotyrosine antibodies). In PMA-stimulated neutrophils, erbstatin antagonized the priming effect of GM-CSF on PLD without affecting the direct effects of the phorbol ester. Buffering cytoplasmic calcium with the chelator BAPTA inhibited fMLP-induced activation of PLD as monitored by the formation of phosphatidylethanol. The stimulation of PLD by PMA was partially attenuated in BAPTA-loaded cells while the priming effect of GM-CSF was abolished. Thus, priming of human neutrophil PLD by GM-CSF may be mediated by G-proteins, by increases in the levels of cytosolic free calcium, and by stimulation of protein kinase C and/or tyrosine kinase(s).
Cell Signal 1992 Sep
PMID:Granulocyte-macrophage colony-stimulating factor primes phospholipase D activity in human neutrophils in vitro: role of calcium, G-proteins and tyrosine kinases. 141 87

Rat mesangial cells contain both calcium-dependent protein kinase C (PKC) activity, which phosphorylates histone H1 and endogenous proteins, and calcium-independent, phospholipid-dependent PKC activity, which phosphorylates only endogenous proteins. The calcium-dependent PKC was identified as PKC alpha by immunoblot analysis and hydroxyapatite chromatography (HPLC). The calcium-insensitive, phospholipid-dependent isoform was identified as PKC delta using similar techniques. The inhibition of these two PKC isoforms by the protein kinase inhibitor H7 [1-(iso-quinolinyl sulphonyl)-2-methyl piperazine] was examined using both histone H1 and endogenous proteins as substrates. Phosphorylations catalyzed by the calcium-dependent PKC isoform alpha were almost 90% inhibited when histone H1 was used, and only 55% when endogenous proteins were the substrate. In contrast, the phosphorylation of endogenous proteins catalysed by the calcium-insensitive, phospholipid-dependent PKC delta was not significantly affected by the inhibitor.
Cell Signal 1992 Sep
PMID:Immunological identification of protein kinase C-alpha and protein kinase C-delta in cultured rat mesangial cells: differential sensitivity of the two isoforms towards the protein kinase inhibitor H7. 141 92

Cell lines stably overexpressing protein kinase C (PKC)-alpha were previously described by us. These cell lines were generated by the introduction of the full length cDNA coding for PKC-alpha into Swiss/3T3 cells. Here we show that activation of PKC-alpha by phorbol-esters induced in these cells specific phosphorylation of two cellular proteins p90 and p52. Phosphorylation of p80 (MARCKS protein), previously identified as a substrate for PKC, was also enhanced. Phosphorylated p90 and p52 proteins were associated with particulate membrane-enriched fractions and were extractable with the use of nonionic detergents. Time course analysis of phorbol-ester induced phosphorylation of p90 and p52 revealed maximal stimulation of phosphorylation after 15-30 min. Phosphamino acid analysis showed that phosphorylation of p90 and p52 occurred mainly on serine residues. Phosphorylation of p52 was also on threonine residues. Whereas, phorbol ester activation induced phosphorylation of both p90 and p52, the mitogens platelet-derived growth factor (PDGF) and fibroblast growth factor (FGF) enhanced phosphorylation of p90, but not p52. Thus, our studies showed the involvement of PKC-alpha in the regulation of p90 and p52 phosphorylation and provided direct evidence for the role of PKC-alpha in cellular signaling by PDGF and FGF. Moreover, the fact that phosphorylation of p52 was specific to phorbol ester activation may suggest its involvement in tumor promotion. Characterization of p90 and p52 will enable us to reveal the phosphorylation cascade activated downstream to PKC-alpha and to determine their role in mitogenic signaling and tumor promotion.
Mol Biol Cell 1992 Sep
PMID:Phosphorylation of p90 and p52 in response to phorbol-esters in Swiss/3T3 cells overexpressing protein kinase C-alpha. 142 77


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