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)

Phosphatidylserine (PS) synthesis was studied in glioma C6 cells with [14C]serine and in the presence or absence of the phorbol ester, 12-O-tetradecanoylphorbol 13-acetate (TPA). It was found that incubation of the cells with 10 nM or 100 nM TPA for 1 h inhibited PS formation by 30% and 60%, respectively. Long-term (18 h) treatment of the cells with 100 nM TPA diminished PS formation and further addition of TPA to down-regulated cells did not affect PS synthesis. The data show that the changes in PS synthesis can be associated with alterations in morphology of cell and the actin cytoskeleton organization. The role of protein kinase C in this process is discussed.
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PMID:Phosphatidylserine synthesis in phorbol ester treated glioma C6 cells. 754 66

Recently this group found an endogenous substrate protein for Ca(2+)-independent novel protein kinase C (nPKC), i.e. KP-10 (pI 4.7/25,500 M(r)), in primary cultured mouse epidermal cells [Nishikawa, K. et al. (1992) Cell. Signal. 4, 757-776]. In the present study, the nPKC isozymes which phosphorylate KP-10 in these cells were determined. Western blot analysis revealed that PKC alpha, eta and zeta were present in epidermal cell 105,000 g supernatants and that the content of PKC zeta was much higher than those of PKC alpha and eta. Neither PKC beta, delta nor epsilon was detected in the 105,000 g supernatants. Phosphatidylserine and phorbol 12-myristate 13-acetate (PMA)-dependent KP-10 phosphorylating activity was immunoprecipitated by anti-PKC eta and zeta antibodies, but not by antiPKC alpha antibody. These results suggest that PKC eta and/or zeta phosphorylate KP-10 and play pivotal roles in intracellular signal pathways in intact epidermal cells.
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PMID:KP-10, a novel protein kinase C substrate in intact mouse epidermal cells, is phosphorylated by novel protein kinase C eta and/or zeta. 781 86

Phosphatidylserine (PS), an activator of protein kinase C (PKC) in the assay of protein phosphorylation, inhibited this enzyme in a time-dependent manner following preincubation in the absence of Ca2+. The phospholipid-induced inactivation of kinase activity was dependent on the PS content and on the charge density of liposomes. This inactivation of PKC could be reduced, but not completely eliminated, by addition of Ca2+. In the present work the effect of a naturally occurring polyamine (spermine) on the PS-induced inactivation of PKC was investigated. The presence of spermine during preincubation without Ca2+ was effective in suppressing the PS-induced inactivation of PKC over the period (20 min) required for PS to inhibit the enzyme by 95%. PKC exists in two membrane-bound states: a reversible one which can be dissociated by Ca2+ chelators (membrane-associated form) and an irreversible one which is chelator-stable (membrane-inserted form). Gel filtration experiments on the PKC-PS complex formed in the presence of Ca2+ indicated that less insertion of enzyme into liposomes occurred in the presence of spermine and that the kinase activity of the reversibly membrane-associated PKC was protected from PS inactivation.
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PMID:Spermine protects protein kinase C from phospholipid-induced inactivation. 795 72

A cardiolipin- and protease-activated protein kinase (PAK) has been isolated from cytoplasmic extracts of rat liver. The enzyme (PAK-1) phosphorylates the ribosomal protein S6-(229-239) peptide analogue and can be activated by limited proteolysis. Partial amino acid sequences of tryptic peptides derived from both the purified 116-kDa PAK-1 holoenzyme and its active catalytic fragment reveal that the catalytic domain is most related (50-58% identity) to the protein kinase C family. PAK-1 has protein and peptide substrate specificities distinct from those of known protein kinase C isoforms and is insensitive to inhibition by the protein kinase C-alpha-(19-31) pseudosubstrate peptide. Phosphatidylserine, diacylglycerol, and phorbol ester do not activate PAK-1 toward the S6 peptide substrate. However, other acidic phospholipids, the most effective being cardiolipin, activate PAK-1 to a similar extent as trypsin. The PAK-1 catalytic activities generated through activation by cardiolipin or limited proteolysis were kinetically similar, with Km values of 3.6 and 3.4 microM, respectively, for the S6-(229-239) peptide substrate. However, differences were observed in the catalytic activities with protamine sulfate and the glycogen synthase-(1-12) peptide analogue as substrates. It was concluded that PAK-1 is a phospholipid-regulated protein kinase with a primary structure, substrate specificity, and mechanism of regulation in vitro distinct from those of any known member of the protein kinase C superfamily.
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PMID:A cardiolipin-activated protein kinase from rat liver structurally distinct from the protein kinases C. 805 Oct 89

Phosphatidylserine, which is necessary for protein kinase C activity, is synthesized in mammalian tissues by the Ca(2+)-dependent base exchange enzyme. The synthesis of phosphatidylserine is greater in slices or homogenates of rat cerebral cortex subjected to hypoxia by N2 treatment when compared with O2 plus 5% CO2. An intermediate effect was observed when the treatment was done with N2 plus 5% CO2. Incorporation rates were dependent on Ca2+ in Krebs-Henseleit Ringer bicarbonate medium, being greater with 2 mM Ca2+ than with the same medium prepared without Ca2+. The increase of phosphatidylserine synthesis, due to hypoxia, was, on the contrary, more evident in the medium lacking added Ca2+. Similar results were obtained with the homogenates. This suggests that elevation of intracellular Ca2+, caused by hypocapnia and hypoxia, may be responsible for the greater incorporation of serine into phosphatidylserine. In both cerebrocortical slices and homogenate, [14C]serine incorporation decreased with development both in O2 plus 5% CO2 and N2-treated preparations. However, in younger rats (14-18 days) hypoxia induced a lesser increase of phosphatidylserine than in 40 day old animals. We suggest that a regulatory mechanism for phosphatidylserine synthesis is established during development and that N2-treatment can increase phosphatidylserine synthesis by interfering with this regulatory mechanism.
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PMID:Phosphatidylserine synthesis in rat cerebral cortex: effects of hypoxia, hypocapnia and development. 830 87

The regulation of the Ca(2+)- and phorbol ester-insensitive zeta isozyme of protein kinase C (PKC zeta) by phospholipids was studied. Phosphatidylserine (PS) stimulated the activity to the same extent as proteolysis by calpain. However, the PS stimulation was abolished by phosphatidylethanolamine (PE) or phosphatidylcholine. Phosphatidylinositol-3,4,5-P3 (PIP3) produced a large stimulation of PKC zeta in the absence or presence of PS plus PE that was equal to that seen with PS alone. In the presence of PS plus PE, PIP3 was half-maximally effective at 50 nM. Phosphatidylinositol-3,4-P2 also fully activated PKC zeta, but higher concentrations (0.5 microM) of phosphatidylinositol-3-P, phosphatidylinositol-4-P, and phosphatidylinositol-4,5-P2 produced only partial (11-30%) activation of the enzyme. In contrast, when tested with "conventional" PKC purified from rat brain, none of the inositol phospholipids produced more than one-third of the stimulation seen with PS plus Ca2+ plus phorbol ester, and there was little difference between the efficacy of PIP3 and that of the other phospholipids. PIP3 produced a marked stimulation of the autophosphorylation of PKC zeta, indicating that it interacted with the enzyme directly. These results suggest that PKC zeta may be a target for PIP3 and thus may be involved in the signaling mechanism(s) for growth factors and oncogenes that increase phosphatidylinositol 3-kinase activity.
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PMID:Activation of the zeta isozyme of protein kinase C by phosphatidylinositol 3,4,5-trisphosphate. 838 Jan 53

A major in vivo substrate of Ca(2+)-phospholipid-dependent protein kinase (MARCKS) shows phosphorylation-dependent translocation between the cytoplasmic and the membrane fractions. The mechanism of the translocation was studied with purified MARCKS and various membranes. MARCKS was found to bind to pure phospholipid membranes as well as to the synaptic vesicle membranes. Although the interaction of MARCKS with the latter was phosphorylation-dependent, phosphorylation by protein kinase C showed no significant effect on the binding to the phosphatidylcholine liposomes. However, when phosphatidylserine was included in the membranes, the association became phosphorylation-dependent. A synthetic phosphorylation domain peptide showed a similar phosphorylation-dependent interaction with the negatively charged liposomes. Phosphatidylserine but not phosphatidylcholine inhibited phosphorylation of MARCKS by protein kinase C. MARCKS seems to bind to the biomembranes through two binding sites: the N-terminal myristoyl moiety and the basic phosphorylation domain of amphiphilic nature. Phosphorylation of this domain lowers its affinity to phosphatidylserine and makes the whole molecule strongly negatively charged, which causes its dissociation from the membranes.
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PMID:Interaction of myristoylated alanine-rich protein kinase C substrate (MARCKS) with membrane phospholipids. 848 22

The phospholipid-dependent protein kinase C is implicated in the regulation of cellular motility and energy metabolism. Phosphatidylserine, a main cofactor of protein kinase C, is involved in the regulation of glyceraldhehyde-3-phosphate dehydrogenase, which as actin, was shown to be phosphorylated by purified protein kinase C. Here, we study the effect of phosphatidylserine on the enzyme-substrate interaction of protein kinase C with glyceraldhehyde-3-phosphate dehydrogenase and actin. The stoichiometry of glyceraldhehyde-3-phosphate dehydrogenase phosphorylation is not affected by varying the level of phosphatidylserine. However, actin phosphorylation is dependent on phosphatidylserine level, peaking at high phosphatidylserine concentration. Moreover, if actin and glyceraldhehyde-3-phosphate dehydrogenase are cophosphorylated at high phosphatidylserine concentration, actin phosphorylation is favored, despite lower affinity for protein kinase C. Hence, phosphatidylserine directs differential phosphorylation of these key proteins of glycolysis and cellular motility and might be capable of recruiting protein kinase C for preferential actin phosphorylation. The sedimentation of phosphorylated actin is increased 3.8 fold and total actin 1.7 fold, suggesting that phosphorylation promotes actin polymerization.
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PMID:Phosphatidylserine directs differential phosphorylation of actin and glyceraldehyde-3-phosphate dehydrogenase by protein kinase C: possible implications for regulation of actin polymerization. 898 31

Transduction of extracellular signals through the membrane involves both the lipid and protein moiety. Phosphatidylserine participates to these processes as a cofactor for protein kinase C activity and thus the existence of a regulatory mechanism for its synthesis ought to be expected. In plasma membranes from rat cerebral cortex, the activity of serine base exchange enzyme, that is mainly responsible for phosphatidylserine synthesis in mammalian tissues, was reduced by the addition to the incubation mixture of AlF4- or GTP-gamma-S, known activators of G proteins, whereas ATP was almost uneffective. GTP-gamma-S inhibited the enzyme activity only at relatively high concentration (> 0.5 mM). When the synthesis of phosphatidylserine in the same cerebral area was investigated by measuring the incorporation of labelled serine into the phospholipid in the homogenate buffered at pH 7.6, ATP had an inhibitory effect as GTP-gamma-S and AlF4-. Heparin activated both serine base exchange enzyme in plasma membranes and phosphatidylserine synthesis in the homogenate. The preincubation of plasma membranes in the buffer without any other addition at 37 degrees C for 15 min reduced by 30% serine base exchange enzyme activity. The remaining activity responded to the addition of GTP-gamma-S but was insensitive to 5 mM AlF-4, a concentration that inhibited by 60% the enzyme assayed without preincubation. These results indicate the existence of different regulatory mechanisms, involving ATP and G proteins, possibly acting on different enzymes responsible for the synthesis of phosphatidylserine. Since previous studies have shown that hypoxia increases the synthesis of this phospholipid in brain slices or homogenate (Mozzi et al. Mol Cell Biochem 126: 101-107, 1993), it is possible that hypoxia may interfere with at least one of these mechanisms. This hypothesis is supported by the observation that in hypoxic homogenate 20 mM AlF-4 was not able to reduce the synthesis of phosphatidylserine as in normoxic samples. A similar difference between oxygenated and hypoxic samples, concerning their response to AlF4-, was observed when the incorporation of ethanolamine into phosphatidylethanolamine was studied. The incorporation of choline into phosphatidilcholine was, on the contrary, inhibited at a similar extent in both experimental conditions.
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PMID:Different mechanisms regulate phosphatidylserine synthesis in rat cerebral cortex. 906 92

Phosphatidylserine is one of the PKC modulators and thus it may play an important role in signal transduction. Regulation of the synthesis of this phospholipid is not yet clarified. The contrasting reports are possibly related to the existence of different enzymes which, in mammalian tissues, catalyse the exchange between free serine and the nitrogen base of a membrane phospholipid. This study demonstrates that serine base exchange reactions of commercially available lyophilised porcine platelets exhibit similar pH optima, temperature and Ca2+ dependence as observed in fresh tissues. Analysis of fatty acids composition of the three phospholipid classes involved in base exchange reactions also demonstrated a similarity with fresh platelets. Serine and ethanolamine base exchange enzyme activities were assayed in parallel in platelet lysate subjected to preincubation at various temperatures (30-60 degrees C). When dithioerithrol was omitted from the incubation medium, the two base exchange reactions were inhibited with a similar temperature-dependent pattern. Addition of the reducing agent enhanced the sensitivity to preincubation only for the serine base exchange reaction which was inhibited by 80% after preincubation at 45 degrees C. With respect to its regulation, porcine platelet serine base exchange enzyme(s) was inhibited by fluoroalluminate, a widely used G-protein activator, and stimulated by unfractionated heparin. Low mol. wt. heparin did not influence enzyme activity. Unfractionated heparin greatly stimulated SBEE activity assayed at pH 7.4, a pH value far from the optimal pH.
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PMID:Serine base exchange enzyme in porcine lyophilised platelets: enzyme properties and modulation by AlF4- and different types of heparin. 1072 47


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