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)

Mitogen-activated protein (MAP) kinases are regarded as switch kinases in the phosphorylation cascade initiated by various agonists. We have investigated whether endothelins (ET), which are constrictor and mitogenic isopeptides, can increase MAP kinase activity in rat mesangial cells, using bovine myelin basic protein (MBP) as a substrate for an in vitro kinase assay. Treatment of quiescent mesangial cells with ET-1 rapidly stimulated a kinase activity which phosphorylated exogenous MBP. This stimulation was dose-dependent, with threshold responses at 1 nM-ET-1. Epidermal growth factor and thrombin also activated this kinase in mesangial cells. We also examined the ET signal transduction pathways leading to activation of MBP kinase. Pertussis toxin had no effect on ET-stimulated MBP kinase activity. Stimulation of protein kinase C by phorbol ester increased MBP kinase activity, and down-regulation of PKC partially inhibited ET-stimulated MBP kinase as well as phorbol ester-stimulated MBP kinase activity. Interestingly, genestein, an inhibitor of protein tyrosine kinases, partially inhibited MBP kinase stimulated by ET but not by phorbol esters. These results suggest that ET stimulates MBP kinase activity in rat mesangial cells via at least two pathways: one which is protein kinase C-dependent and a second one that involves a protein tyrosine kinase. Finally, by raising rabbit antibodies against the two forms of MAP kinase, p44mapk and p42mapk, we demonstrated that both isoforms are expressed in mesangial cells. Antibody alpha 1 Cp42 specifically immunoprecipitated p42mapk and allowed us to demonstrate that ET stimulates MBP kinase activity in the p42mapk immunocomplex. In conclusion, we have provided evidence that, in rat mesangial cells, MAP kinases are rapidly activated by ET-1, a regulatory process that involves at least protein kinase C activation and also a contribution of a tyrosine kinase not yet characterized.
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PMID:Endothelin rapidly stimulates mitogen-activated protein kinase activity in rat mesangial cells. 128 Jan 3

Cytoskeletal preparation obtained from synaptosome fractions of rat cerebrum contained the activity of kinase C, which phosphorylated 17K Mr protein endogenous to the preparation. The kinase C activity associated with the synaptosome cytoskeletons is greater in the cerebellum and hippocampus than in the cerebrum. The enhancement rates of phosphorylation of the 17K Mr protein were 293%, 544%, and 526% in the Triton X-100-insoluble fractions of synaptosomes prepared from cerebral cortex, hippocampus, and cerebellum, respectively. The 17K Mr protein was distinct from myelin basic protein (MBP) for the following reasons: 1) The electrophoretic mobility of the protein was slightly smaller than that of major MBP of rat in the polyacrylamide gel of 10-20% linear gradient, and the protein was not contained in the purified rat myelin. 2) The isoelectric point of the protein was in neutral range, whereas that of MBP was in alkaline one. 3) The 17K Mr protein did not cross-react with anti-MBP antibody. The protein was shown to be a major substrate contained in the cytoskeletal preparation of synaptosome obtained from cerebrum except for contaminating MBP. Only serine residue of the 17K Mr protein was phosphorylated by the kinase C endogenous to the preparation. The results suggest strongly that the synaptic role of protein kinase C through phosphorylation of the 17K Mr protein.
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PMID:The presence of 17K Mr protein, a major specific substrate for kinase C, found in the triton-insoluble fraction of synaptosome prepared from rat brain. 128 Dec 91

Mitoxantrone, a new anthraquinone, showed inhibitory an effect on protein kinase C (PKC) activity. Its IC50 value was 4.4 micrograms/ml (8.5 microM), which is much lower than those of the well-known anthracyclines daunorubicin and doxorubicin, the IC50 values of which are more than 100 micrograms/ml (> 170 microM). Kinetic studies demonstrated that mitoxantrone inhibited PKC in a competitive manner with respect to histone H1, and its Ki value was 6.3 microM (Ki values of daunorubicin and doxorubicin were 0.89 and 0.15 mM, respectively), and in a non-competitive manner with respect to phosphatidylserine and ATP. Inhibition of phosphorylation by mitoxantrone was observed with various substrates including S6 peptide, myelin basic protein and its peptide substrate derived from the amino-terminal region. Their IC50 values were 0.49 microgram/ml (0.95 microM), 1.8 micrograms/ml (3.5 microM), and 0.82 microgram/ml (1.6 microM), respectively. Mitoxantrone did not markedly inhibit the activity of cyclic AMP-dependent protein kinase, casein kinase I or casein kinase II, at concentrations of less than 10 micrograms/ml. On the other hand, brief exposure (5 min) of HL60 cells to mitoxantrone caused the inhibition of cell growth with an IC50 value of 52 ng/ml (0.1 microM). In HL60 cells, most of the PKC activity (about 90%) was detected in the cytosolic fraction. When HL60 cells exposed to 10 micrograms/ml mitoxantrone for 5 min were observed with fluorescence microscopy, the fluorescence elicited from mitoxantrone was detected in the extranuclear area. These results indicated that mitoxantrone is a potent inhibitor of PKC, and this inhibition may be one of the mechanisms of antitumor activity of mitoxantrone.
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PMID:Inhibitory effect of mitoxantrone on activity of protein kinase C and growth of HL60 cells. 129 84

We have previously demonstrated that growth hormone (GH) promotes an increase in tyrosine kinase activity associated with the GH receptor. To gain insight into the role of GH-dependent tyrosine kinase activity in signaling by GH, we investigated the possibility that GH might stimulate MAP kinase, a serine/threonine/tyrosine kinase thought to be a common element in tyrosine kinase-initiated response cascades. Treatment of 3T3-F442A fibroblasts with 100 ng/ml GH results in a 3-6-fold increase in the ability of cell-free extracts to phosphorylate MAP-2 and myelin basic protein. GH-stimulated kinase activity is unaffected by heparin, H7, or cAMP-dependent protein kinase inhibitor peptide, partially reduced by staurosporin and inhibited by fluoride and calcium ions, indicating that the kinase is not protein kinase C or A, casein kinase, or a calcium/calmodulin-dependent protein kinase. Based on gel permeation chromatography, the molecular mass of the GH-stimulated MAP kinase is approximately kDa. Furthermore, anti-phosphotyrosine antibodies revealed the GH-dependent appearance of two phosphotyrosine-containing proteins in cell-free lysates of GH-treated cells that co-migrate with proteins recognized by anti-MAP kinase antibodies. The GH-dependent increase in MAP kinase activity displays a biphasic time course and is dependent on the concentration of GH applied to the cells. GH-dependent MAP kinase activity, partially purified by Mono-Q chromatography, is inactivated by treatment with alkaline phosphatase. Addition of H7 to the cells prior to the addition of GH has no effect, whereas addition of H8 increases MAP kinase activity in control cells with no effect in GH-treated cells, indicating that protein kinase C is unlikely to be an intermediary in the GH-dependent stimulation of MAP kinase activity. These findings indicate that signaling by GH in 3T3-F443A cells may, at least in part, utilize a kinase cascade similar to those that have been proposed for other membrane receptors with associated tyrosine kinase activity.
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PMID:Stimulation by growth hormone of MAP kinase activity in 3T3-F442A fibroblasts. 131 28

Ovine oligodendrocytes (OLGs) undergo biochemical and morphological changes following attachment to polylysine. Autoradiographs of two-dimensional thin-layer chromatograms of [14C]Gal-labeled OLG cultures revealed that attachment of OLGs to a polylysine substratum and their subsequent morphological differentiation is accompanied by an increased synthesis of multiple forms of galactosylceramide, sulfogalactosylceramide, and both sulfogalactosyl- and galactosyl-diglycerides, together with an array of complex sialoglycosphingolipids, predominantly GM2 ganglioside. As previously reported, overall lipid synthesis measured by [14C]acetate incorporation into glycerophosphatides, sphingomyelin, and neutral lipids also increased dramatically for up to 60 days (last time point examined) following OLG-substratum adhesion, reflecting membrane growth. Attachment was associated with a rapid augmentation in the synthesis of ethanolamine plasmalogen from 12 to 27% within 24 hr to reach a 35% plateau at 30 days and remain constant thereafter. In contrast, the plasmalogen content of phosphatidylcholine remained constant at 3-5%. This rapid increase in lipid synthesis (especially in the ethanolamine plasmalogen content following attachment) closely paralleled increased diacylglycerol (DAG) production and protein kinase C-dependent phosphorylation of both myelin basic protein and 2',3'-cyclic nucleotide phosphohydrolase. Labeling studies indicated that the major source of [3H]arachidonate-labeled DAG following attachment was from phosphatidylinositol turnover (and to a lesser extent phosphatidylcholine) rather than polyphosphoinositides or plasmalogens. Enhanced lipid synthesis is not only required for the production of membranes in these myelin-producing cells but is also a source of second messengers required in the posttranslational modification of key myelin and cellular proteins.
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PMID:Oligodendrocyte-substratum adhesion activates the synthesis of specific lipid species involved in cell signaling. 132 Dec 54

Nerve growth factor-stimulated mitogen-activated protein kinase (pp42/44MAP) kinase was characterized by sequential column chromatography on DEAE-Sephacel, phenyl-Sepharose CL4B, and S-200. The kinase displayed an apparent molecular mass of 42 kDa and reacted with an antiphosphotyrosine antibody. Peptide mapping of myelin basic protein revealed the presence of one phosphopeptide that was phosphorylated on Thr-97. pp42/44MAP kinase activity was dependent on Mg2+ and inhibited by K252a both in vitro and in vivo. Nerve growth factor-stimulated kinase activation was diminished by down-regulation of protein kinase C with 200 nM 12-phorbol 13-myristate acetate or with staurosporine (1 nM), a protein kinase C inhibitor. Genistein, a protein tyrosine kinase inhibitor, blocked nerve growth factor-mediated neurite extension as well as diminished activation of pp42/44MAP kinase. Our data demonstrate that activation of this kinase system by nerve growth factor displays a requirement for both protein kinase C as well as protein tyrosine kinase. In addition, other agents that are capable of promoting neurite outgrowth in PC12 cells, such as fibroblast growth factor or dibutyryl cyclic AMP, do so independently of activating this kinase system.
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PMID:pp42/44MAP kinase is a component of the neurogenic pathway utilized by nerve growth factor in PC12 cells. 132 67

Microtubule-associated protein 2 (MAP2) kinase has been isolated and characterized from rat brain. The enzyme has an apparent M(r) of approximately 42,000 and its pI is 4.9. MAP2 was the preferred substrate, but it also phosphorylated myelin basic protein (MBP), histone V-S, tubulin and the PC12 protein substrate pp250. The enzyme is distinct from protein kinase C, cAMP-dependent kinase and the calcium/calmodulin-dependent kinases, as specific inhibitors of these kinases did not affect MAP2 phosphorylation. The addition of the relatively non-specific protein kinase inhibitor H7 (20 microM) had a modest inhibitory effect. The enzyme was active in both 5 mM Mn2+ and Mg2+, and displayed Kms for MAP2, MBP, and ATP of 56 nM, 254 nM, and 4 microM, respectively. This enzyme, which represents a low abundance protein in whole brain, is analogous to the MAP2 kinase observed in growth factor-stimulated cell lines.
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PMID:Isolation and characterization of microtubule-associated protein 2 (MAP2) kinase from rat brain. 132 16

In cultured vascular smooth muscle cells, angiotensin II (Ang II) stimulated a cytosolic protein kinase activity toward myelin basic protein (MBP) in a time- and dose-dependent manner. Phorbol 12-myristate 13-acetate (PMA) and phorbol 12,13-dibutyrate also increased the MBP kinase activity. Downregulation of protein kinase C by prolonged treatment of the cells with phorbol 12,13-dibutyrate markedly attenuated the Ang II- and PMA-induced MBP kinase activation. The Ang II- and PMA-stimulated MBP kinase activities were resolved almost equally into two distinct fractions on Mono-Q HR5/5 column chromatography (kinase 1 and kinase 2). The kinase assay in polyacrylamide gel revealed that apparent molecular masses of kinase 1 and kinase 2 were 40 and 45 kd, respectively. Microtubule-associated protein 2 also served as a substrate for both the kinases. Immunoblot analysis with an antiphosphotyrosine antibody suggested that both the kinases were tyrosine-phosphorylated during the action of Ang II. Phosphoamino acid analysis revealed that Ang II and PMA induced phosphorylation of both the kinases on serine/threonine as well as tyrosine residues. Phosphopeptide mapping patterns of kinase 1 and kinase 2 isolated from Ang II-stimulated cells were almost identical with those from PMA-stimulated cells. These results indicate that in vascular smooth muscle cells Ang II activates two species of MBP/microtubule-associated protein 2 kinases mainly through the protein kinase C-signaling pathway and suggest that tyrosine and serine/threonine phosphorylation may be involved in this process.
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PMID:Angiotensin II stimulates two myelin basic protein/microtubule-associated protein 2 kinases in cultured vascular smooth muscle cells. 132 34

It has been suggested that phosphorylation of myelin basic protein (MBP) in CNS is catalyzed by protein kinase C (PKC). In order to demonstrate that PKC in the myelin phosphorylates MBP, PKC was partially purified from rat CNS myelin by solubilization with Triton X-100 followed by a DEAE-cellulose column. MBP and histone III-S were phosphorylated in the presence of Ca2+ and phospholipid by rat myelin PKC. High voltage electrophoresis revealed that the phosphoamino acids in MBP by this kinase was serine residue, which is known to be the amino acid phosphorylated by PKC. The activity of PKC extracted from myelin was inhibited by the addition of psychosine to the incubation mixture. To confirm the presence of PKC molecule and to identify the isoform of PKC in the myelin, the solubilized myelin fraction was applied on SDS-PAGE, transferred to a nitrocellulose sheet and stained with anti-PKC monoclonal antibodies. Rat CNS myelin contained the PKC of about 80 kDa (intact PKC), and no proteolytic fragments were observed. PKC isozymes in myelin were type II and III. A developmental study from 14 to 42 postnatal days showed that PKC activity in CNS myelin seemed to parallel the deposition of myelin protein.
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PMID:Protein kinase C in rat brain myelin. 138 Jun 75

Cross-linking of membrane immunoglobulin (mIg), the B lymphocyte antigen receptor, with anti-receptor antibodies stimulates tyrosine phosphorylation of a number of proteins, including one of 42 kDa. Proteins with a similar molecular mass are tyrosine-phosphorylated in response to receptor stimulation in other cell types and have been identified as serine/threonine kinases, termed mitogen-activated protein (MAP) kinases or extracellular signal-regulated kinases (ERKs). The MAP kinases constitute a family of related kinases, at least three of which have molecular masses of 40-45 kDa. In this paper we show that mIg cross-linking stimulated the myelin basic protein phosphotransferase activity characteristic of MAP kinase in both mature and immature murine B cell lines. This enzyme activity co-purified on three different columns with a 42 kDa protein that was tyrosine-phosphorylated (pp42) in response to mIg cross-linking and which reacted with a panel of anti-(MAP kinase) antibodies. Although immunoblotting with the anti-(MAP kinase) antibodies showed that these B cell lines expressed both 42 kDa and 44 kDa forms of MAP kinase, only the 42 kDa form was activated and tyrosine-phosphorylated to a significant extent. Activation of protein kinase C (PKC) with phorbol esters also resulted in selective tyrosine phosphorylation and activation of the 42 kDa MAP kinase. This suggested that mIg-induced MAP kinase activation could be due to stimulation of PKC by mIg. However, mIg-stimulated MAP kinase activation and pp42 tyrosine phosphorylation was only partially blocked by a PKC inhibitor, the staurosporine analogue Compound 3. In contrast, Compound 3 completely blocked the ability of phorbol esters to stimulate MAP kinase activity and induce tyrosine phosphorylation of pp42. Thus mIg may activate MAP kinase by both PKC-dependent and -independent mechanisms.
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PMID:Selective activation of p42 mitogen-activated protein (MAP) kinase in murine B lymphoma cell lines by membrane immunoglobulin cross-linking. Evidence for protein kinase C-independent and -dependent mechanisms of activation. 138 67


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