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)

Recently, we reported that in mouse mastocytoma P-815 cells the cytosol contains some factor(s) which promotes the release of GTP-activated Gi2 alpha from the membrane, and that thrombin induces the translocation of Gi2 alpha from the membrane to the cytosol (Takahashi, S., Negishi, M. and Ichikawa, A. (1991) J. Biol. Chem. 266, 5367-5370). Here we investigated the mechanism underlying the thrombin-induced translocation of Gi2 alpha in mastocytoma cells. Thrombin induced a rapid and transient increase in the intracellular Ca2+ concentration ([Ca2+]i) within 1 min, attenuated pertussis toxin-catalyzed ADP-ribosylation of Gi2 in the membrane, and caused the subsequent translocation of Gi2 alpha. Thrombin induced the translocation of protein kinase C from the cytosol to the membrane, and a protein kinase C inhibitor, staurosporine, completely inhibited the thrombin-induced translocation of Gi2 alpha. When cells were treated with thrombin, the ability of the cytosol to release Gi2 alpha from the membrane in the presence of GTP gamma S markedly increased. This stimulatory effect of thrombin on the ability of the cytosol was mimicked by 12-O-tetradecanoylphorbol 13-acetate (TPA), but not by the Ca2+ ionophore, ionomycin. The thrombin- and TPA-induced potentiation of the ability of the cytosol to release Gi2 alpha was completely abolished by staurosporine. Furthermore, phosphorylation of the cytosol by protein kinase C markedly potentiated the ability of the cytosol to release Gi2 alpha. These results together demonstrate that the thrombin-induced translocation of Gi2 alpha is due to enhancement of the ability of the cytosol to release Gi2 alpha via activation of protein kinase C.
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PMID:Involvement of protein kinase C in thrombin-induced translocation of Gi2 alpha from the membrane to the cytosol in mouse mastocytoma P-815 cells. 154 55

smg p21A and -B (smg p21s) are ras p21-like small GTP-binding proteins (G proteins) with the same putative effector domain as ras p21s. Both smg p21A mRNA and smg p21B mRNA were detected in CMK, a human megakaryocytic leukemia cell line, and their levels were markedly elevated by treatment with 12-O-tetradecanoyl-phorbol-13-acetate (TPA), which caused the differentiation of this cell line into more mature megakaryocytes. The smg p21 protein molecules also increased during the TPA-induced differentiation of CMK cells. The mRNA level of glycoprotein IIb (GPIIb), a typical marker of the megakaryocytes, was increased by this treatment, but the time course of the increase in the smg p21 mRNA levels as more rapid than that of the increase in the GPIIb mRNA level. Ha-ras p21 mRNA was undetectable, but both Ki- and N-ras p21 mRNAs were detected in CMK cells and their levels were also increased during TPA-induced differentiation of CMK cells, although to a lesser extent than those of smg p21 mRNAs. Protein kinase C inhibitors inhibited the basal and TPA-induced smg p21A mRNA level, but cyclic AMP-elevating prostaglandin E1 or Ca(2+)-mobilizing ionomycin did not inhibit them. Cycloheximide enhanced the basal and TPA-induced smg p21A mRNA levels. Actinomycin D blocked the TPA-induced smg p21A mRNA levels, but showed no detectable effect on the elevated smg p21A mRNA level which was induced by pretreatment with TPA. A dramatic increase in the smg p21 mRNA levels was also observed in other leukemia cell lines during TPA-induced differentiation. These results suggest that TPA stimulated expression of the smg p21A gene, presumably through the action of protein kinase C at the transcriptional level rather than at the post-transcriptional level, in hematopoietic leukemia cells.
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PMID:Induction of smg p21/rap1A p21/krev-1 p21 gene expression during phorbol ester-induced differentiation of a human megakaryocytic leukemia cell line. 154 53

Muscarinic cholinergic receptors (mAChR) purified from chick heart were phosphorylated by protein kinase C (PKC) and reconstituted with the purified GTP-binding regulatory protein Go. The effects of PKC phosphorylation on the interaction of mAChR with Go were assessed by monitoring for agonist-stimulated guanosine-5'-O-(3-thiotriphosphate) (GTP gamma S) binding to Go, agonist-stimulated GTPase activity of Go, and the capability of Go to induce high affinity agonist binding to mAChR. Both the receptor-stimulated GTP gamma S binding and GTPase activity of Go were markedly diminished as a result of PKC-mediated phosphorylation of the mAChR, whereas the ability of Go to induce high affinity agonist binding to the receptors was unaffected. When mAChR were first reconstituted with Go and then subjected to phosphorylation with PKC, a complete inhibition of the phosphorylation of mAChR by PKC was observed. The inhibitory effect of Go on mAChR phosphorylation was concentration-dependent and was prevented by the presence of GTP gamma S in the reaction mixtures. Taken together, these results indicate that the phosphorylation of mAChR by PKC modulates receptor/G-protein interactions and that the ability of the receptors to act as substrates for PKC may be regulated by receptor/G-protein interactions.
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PMID:Functional effects of protein kinase C-mediated phosphorylation of chick heart muscarinic cholinergic receptors. 157 82

Stimulation of phospholipase D (PLD) by cell surface receptors has been observed in many cell types. We have investigated the mechanism of activation of this enzyme in undifferentiated HL60 cells. GTP analogues and Ca2+ (buffered in the nanomolar to micromolar range) were introduced into HL60 cells in the presence of the permeabilizing agent, streptolysin O. We report that guanosine 5'-[gamma-thio]triphosphate (GTP[S]) is a potent activator of phospholipase D when Ca2+ is available at micromolar levels. Phorbol 12-myristate 13-acetate or Ca2+ alone can also stimulate PLD, but to a limited extent. The activation of PLD by GTP[S] can be partially dissociated from GTP[S]-stimulated phosphoinositide-specific phospholipase C, suggesting that a G-protein may be directly involved in regulating PLD. However, maximal activation of PLD only occurs under conditions that are permissive to phospholipase C stimulation. We conclude that PLD activation is under dual control, i.e. protein kinase C- as well as G-protein-mediated regulation. Synergistic activation occurs when both pathways are simultaneously stimulated. We conclude that full activation of PLD requires protein kinase C, increased Ca2+ and a GTP-binding protein. Evidence for cytosolic components that may also be involved in obtaining full activation of PLD is also presented.
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PMID:Synergistic activation of phospholipase D by protein kinase C- and G-protein-mediated pathways in streptolysin O-permeabilized HL60 cells. 159 36

To determine the role of protein tyrosine phosphorylation in the activation of phospholipase D (PLD), electropermeabilized HL-60 cells labeled in [3H]alkyl-phosphatidylcholine were treated with vanadate derivatives. Micromolar concentrations of vanadyl hydroperoxide (V(4+)-OOH) induced accumulation of tyrosine-phosphorylated proteins. Concomitantly, V(4+)-OOH or a combination of vanadate and NADPH elicited a concentration- and time-dependent accumulation of phosphatidic acid (PtdOH). In the presence of ethanol a sustained formation of phosphatidylethanol was observed, indicating that a type D phospholipase was activated. A good correlation was found to exist between the accumulation of tyrosine-phosphorylated proteins and activation of PLD. The V(4+)-OOH concentration dependence of the two responses was nearly identical, and the time course of activation was similar, with tyrosine phosphorylation preceding PLD activation by approximately 1 min. The ability of V(4+)-OOH to induce both responses was found to be strictly dependent on the presence of ATP and/or Mg2+, suggesting that PLD activation involves phosphotransferase reactions. Accordingly, ST638, a tyrosine kinase inhibitor, reduced concomitantly tyrosine phosphorylation and PLD activation elicited by V(4+)-OOH. The mechanism of action of V(4+)-OOH was investigated. The diacylglycerol kinase inhibitors, dioctanoylethylene glycol and R59022 potentiated PLD stimulation by exogenous diacylglycerol but not by V(4+)-OOH. Moreover, stimulation by V(4+)-OOH and by phorbol esters was synergystic. Therefore, diacylglycerol-induced activation of protein kinase C is unlikely to mediate the effects of V(4+)-OOH. The response of PLD to V(4+)-OOH was larger than that to guanosine 5'-(gamma-thio)triphosphate. Moreover, the effects of GTP gamma S and V(4+)-OOH were additive. Hence, activation of G proteins cannot account for the stimulation of PLD by V(4+)-OOH. V(4+)-OOH also triggers a burst of O2 consumption by the NADPH oxidase. Inhibition of PtdOH accumulation by addition of ethanol or by ST638 abolished this respiratory burst. Together, the results establish a strong correlation between tyrosine phosphorylation, PLD activation, and stimulation of the NADPH oxidase in HL-60 cells, suggesting a causal relationship.
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PMID:Peroxides of vanadate induce activation of phospholipase D in HL-60 cells. Role of tyrosine phosphorylation. 160 60

T-lymphocyte activation via the antigen receptor complex (TCR) results in accumulation of p21ras in the active GTP-bound state. Stimulation of protein kinase C (PKC) can also activate p21ras, and it has been proposed that the TCR effect on p21ras occurs as a consequence of TCR regulation of PKC. To test the role of PKC in TCR regulation of p21ras, a permeabilized cell system was used to examine TCR regulation of p21ras under conditions in which TCR activation of PKC was blocked, first by using a PKC pseudosubstrate peptide inhibitor and second by using ionic conditions that prevent phosphatidyl inositol hydrolysis and hence diacylglycerol production and PKC stimulation. The data show that TCR-induced p21ras activation is not mediated exclusively by PKC. Thus, in the absence of PKC stimulation, the TCR was still able to induce accumulation of p21ras-GTP complexes, and this stimulation correlated with an inactivation of p21ras GTPase-activating proteins. The protein tyrosine kinase inhibitor herbimycin could prevent the non-PKC-mediated, TCR-induced stimulation of p21ras. These data indicate that two mechanisms for p21ras regulation coexist in T cells: one PKC mediated and one not. The TCR can apparently couple to p21ras via a non-PKC-controlled route that may involve tyrosine kinases.
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PMID:Role of protein kinase C in T-cell antigen receptor regulation of p21ras: evidence that two p21ras regulatory pathways coexist in T cells. 162 Jan 32

Sphingosine displays multiple biochemical and biological effects, in particular inhibition and activation of protein kinases. To determine the predominant interaction of sphingosine with cellular kinases, the effects of sphingosine on endogenous protein phosphorylation in Jurkat T lymphoblastic cells were investigated in vitro. Sphingosine was found to cause prominent phosphorylation of a number of cytosolic proteins ranging in molecular mass from 18 to 165 kDa. Phosphorylation was calcium-independent. Phosphorylation of substrates was increased in response to concentrations of sphingosine as low as 10 microM and peaked at concentrations of 20-200 microM. Multiple lines of evidence suggested that sphingosine activated more than one protein kinase: 1) the concentration dependence on sphingosine differed from substrate to substrate, 2) phosphorylation of one group of substrates required ATP as the phosphate donor, whereas a second group showed no preference between ATP and GTP, and 3) phosphorylation of some substrates was inhibited by heparin, whereas other substrates were resistant. Activation of these kinases demonstrated a very specific requirement for D-erythro-sphingoid bases. DL-erythro-dihydrosphingosine was partially active, whereas DL-threo-dihydrosphingosine was not. Other related molecules such as stearylamine, sphingomyelin, and C2-ceramide were not active. Sphingosine-activated kinase(s) were distinct from protein kinase C, cyclic nucleotide-activated kinases, and calcium-dependent kinases. These observations demonstrate the existence of multiple sphingosine-activated protein kinases with high specificity for D-erythro-sphingosine, suggesting physiologic regulation of protein phosphorylation by sphingosine.
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PMID:Sphingosine activation of protein kinases in Jurkat T cells. In vitro phosphorylation of endogenous protein substrates and specificity of action. 163 54

Lysophosphatidic acid (LPA) is a simple phospholipid that possesses hormone- and growth-factor-like properties. LPA initiates its action by inducing GTP-dependent phosphoinositide hydrolysis and inhibiting adenylate cyclase [van Corven, Groenink, Jalink, Eichholtz & Moolenaar (1989) Cell 59, 45-54]. Here we show that LPA stimulates rapid breakdown of phosphatidylcholine (PC) in Rat-1 fibroblasts. LPA-induced PC breakdown occurs through activation of phospholipase D (PLD), as measured by the formation of free choline and phosphatidic acid and by transphosphatidylation in the presence of butan-1-ol. LPA also stimulates generation of diacylglycerol, but there is no detectable formation of phosphocholine, suggesting that a PC-specific phospholipase C (PLC) is not involved. The response to LPA was compared with that to endothelin, a potent inducer of phospholipid hydrolysis but a poor mitogen for Rat-1 cells. Our results indicate that: (1) LPA is less efficient than endothelin in inducing phosphoinositide and PC breakdown; (2) LPA-induced PLD activation is short-lived, levelling off after 2 min, whereas the endothelin-stimulated increase in PLD activity persists for at least 1 h; (3) the effect of LPA on PLD, like that of endothelin, is blocked by long-term pretreatment of the cells with phorbol ester, suggesting that PLD activation occurs through a protein kinase C-dependent mechanism. Furthermore, our results support the notion that there is no simple causal relationship between the degree of agonist-induced phospholipid hydrolysis and the magnitude of the mitogenic response.
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PMID:The biologically active phospholipid, lysophosphatidic acid, induces phosphatidylcholine breakdown in fibroblasts via activation of phospholipase D. Comparison with the response to endothelin. 163 5

Human myeloid leukemia cells (i.e., HL-60, U937, THP-1) which are induced to differentiate along the monocytic pathway by 12-O-tetradecanoylphorbol-13-acetate (TPA), revert back to the undifferentiated phenotype after 3 to 4 weeks. During this differentiation and retrodifferentiation process the cells obviously establish a distinct sequence of biological processes which is integrally regulated to simultaneously control differentiation and cell growth. Thus, induction of monocytic markers by TPA is associated with a down-regulation of cell cycle genes and cessation of proliferation. In particular, crosstalk between the TPA-induced translocation of protein kinase C (PKC) and the activation of transcription factors, especially AP-1, enhances the expression of genes associated with the monocytic phenotype. This is accompanied by induction of intermediate filament proteins, surface glycoproteins, changes in membrane properties and intracellular metabolism. In parallel, the cells cease to divide, and genes associated with cell cycle progression including cdc2, cyclins, cdc25, and histones are down-regulated. Although signals responsible for arrested cell growth remain unclear, there are several control mechanisms regarding cell cycle genes and differentiation parameters (for a review, see Nigg, E. A., Seminars in Cell Biol., 2, 262-270, 1991). For example, activated p34cdc2 kinase is involved in lamina disassembly by direct phosphorylation of lamin proteins which may contribute to nuclear envelope breakdown during mitosis (Enoch, T., M. Peter, P. Nurse, J. Cell Biol. 112, 797-807 (1991)). Moreover, endomembrane traffic is arrested by a cdc2-like kinase probably via phosphorylation of members of the rab protein family which contributes to vesiculation and membrane transport by hydrolyzing GTP (Tuomikoski, T., et al., Nature 342, 942-945 (1989)). Although there are several reports on a possible feedback control between differentiation and cell cycle, including phosphorylation of cyclins and activation of a ubiquitin-dependent proteolytic degradation, signaling pathways and possible mechanisms for retrodifferentiation and reentry into the cell cycle remain unclear. While some terminally differentiated cells are committed to die, the major part of the differentiated monocytic population undergoes retrodifferentiation. All cellular signals characterized so far are reverted during retrodifferentiation: Redistribution of PKC and down-regulation of c-fos and c-jun contribute to an interruption of the differentiation-associated transsignaling cascade. Thus, down-regulation of markers associated with monocytic differentiation in combination with metabolic changes restore the original cell phenotype. At the same time cell cycle genes are up-regulated, and the cells regain proliferative capacity. Finally, retrodifferentiated and untreated control cells demonstrate indistinguishable properties.
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PMID:Retrodifferentiation--an alternative biological pathway in human leukemia cells. 164 56

Limited tryptic proteolysis of homogeneous protein kinase C induces the formation of a catalytically active fragment of 50 kDa (kinase M) which, unlike native PK C acquires the ability to phosphorylate PIP. Both ATP and GTP were found to be capable of serving as phosphate donors in this process. Incubation of purified kinase M with a preparation of rat brain membrane fraction enhanced the level of phosphorylation of PIP in the presence and in the absence of exogenous PIP. A scheme of the interrelationship of phosphoinositide metabolism and the proteolytic processing of protein kinase C is proposed.
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PMID:Proteolytic fragment of protein kinase C (kinase M) phosphorylates in vitro phosphatidylinositol-4-phosphate. 164 34


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