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)

Cationic polypeptides are released by activated leukocytes and may play an important role in the regulation of vascular tone. Effects of cationic polypeptides on cerebral vascular tone have not been studied. The present experiments were designed to determine if synthetic cationic polypeptides, poly-L-arginine and poly-L-lysine, affect the function of cerebral arteries. Rings of canine basilar arteries with and without endothelium were suspended for isometric force recording. Poly-L-arginine (10(-8)-10(-7) M) and poly-L-lysine (10(-8)-10(-7).M) caused endothelium-dependent relaxations. A nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl ester (10(-4) M), and a nitric oxide scavenger, oxyhemoglobin (3 x 10(-6) M), inhibited relaxations in response to cationic polypeptides. Negatively charged molecules, heparin (1 U/ml) and dextran sulfate (10 mg/ml), also inhibited relaxations to poly-L-arginine or poly-L-lysine. Higher concentrations of poly-L-arginine (10(-6)-10(-5) M) and poly-L-lysine (10(-6)-10(-5) M) induced endothelium-independent contractions. A protein kinase C inhibitor, staurosporine (10(-8) M), abolished these contractions. Heparin (10 U/ml) and dextran sulfate (100 mg/ml) inhibited the contractile effect of cationic polypeptides but did not affect contractions to phorbol 12,13-dibutyrate. Poly-L-arginine (10(-6) M) and poly-L-lysine (10(-6) M) abolished endothelium-dependent relaxations in response to bradykinin (10(-10)-10(-6) M) or calcium ionophore A23187 (10(-9)-10(-6) M). Heparin (50 U/ml) and dextran sulfate (200 mg/ml) restored endothelium-dependent relaxations to bradykinin (10(-10)-10(-6) M) in arteries exposed to poly-L-arginine (10(-6) M) or poly-L-lysine (10(-6) M). These studies demonstrate that in the lower concentration range (10(-8)-10(-7) M), poly-L-arginine and poly-L-lysine induce endothelium-dependent relaxations by production of nitric oxide via charge-dependent activation of endothelial nitric oxide synthase. In the higher concentration range (10(-6)-10(-5) M), cationic polypeptides cause endothelium-independent contractions as well as impairment of endothelium-dependent relaxations in response to bradykinin and A23187. These contractions and inhibition of endothelium-dependent relaxations are also mediated by a charge-dependent mechanism and may involve activation of protein kinase C.
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PMID:Nitric oxide and effects of cationic polypeptides in canine cerebral arteries. 914 30

Proliferation of vascular smooth muscle cells (SMCs) is implicated in pathological events, including atherosclerosis and intimal hyperplasia following angioplasty. The glycosaminoglycan heparin is a growth inhibitor of SMCs in vitro and in vivo. The underlying mechanism, however, is still poorly understood. In the present study, we report that heparin inhibited the activation of the mitogen-activated protein kinase (MAPK) in baboon SMCs by serum but not by platelet-derived growth factor (PDGF). When fibroblast growth factor was used, heparin had a stimulatory effect on MAPK. The only MAPK-activating kinase found in SMCs was MAPK kinase (MAPKK)-1, although MAPKK-2 was present in comparable amounts. Activation of MAPKK-1 and DNA synthesis were affected by heparin in a similar fashion. Heparin does not appear to exert its effects through members of the protein kinase C family, which are downregulated by phorbol esters, because it was still capable of inhibiting MAPK/MAPKK-1 stimulation by FCS in phorbol ester-pretreated cells. The present findings support the conclusions that the effects of heparin depend on the nature of the mitogen and that heparin inhibits SMC proliferation by preventing activation of MAPKK-1.
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PMID:Diverse effects of heparin on mitogen-activated protein kinase-dependent signal transduction in vascular smooth muscle cells. 920 Oct 23

Heparin and heparan are potent inhibitors of vascular smooth muscle cell (VSMC) proliferation. To investigate the mechanisms by which heparin suppresses growth factor stimulated mitogenesis, the present experiments investigated the effects of heparin on platelet-derived growth factor (PDGF) stimulated signal transduction pathways. Heparin treatment substantially inhibited PDGF-BB stimulated rat VSMC growth. Western analysis showed a 30 min PDGF-BB treatment of VSMC induced the tyrosine phosphorylation of multiple protein bands; cotreatment with heparin inhibited mitogen-activated protein (MAP) kinase tyrosine phosphorylation but had little effect on PDGF receptor tyrosine phosphorylation. In-gel kinase assays demonstrated that heparin inhibited PDGF-BB stimulated MAP kinase activity at late (25 min) but not early (10 min) time points. These data indicate that heparin does not inhibit the initial signalling events after PDGF-BB binding but instead acts through an alternate mechanism to inhibit MAP kinase. To investigate if heparin directly stimulates tyrosine phosphatase-mediated suppression of MAP kinase, we treated VSMC with orthovanadate, a tyrosine phosphatase inhibitor. Heparin inhibited MAP kinase tyrosine phosphorylation after orthovanadate treatment, indicating that heparin does not suppress MAP kinase by enlistment of a tyrosine phosphatase. Experiments were performed to investigate signalling pathways upstream of MAP kinase. To determine if protein kinase C (PKC) mediates PDGF-BB, serum, and EGF stimulation of MAP kinase, we treated VSMC overnight with phorbol ester (PMA) to downregulate PKC. Abolition of conventional and novel PKC activity significantly suppressed both serum and PDGF-BB induced MAP kinase activation, indicating protein kinase C is an important mediator for these mitogens. In contrast, downregulation of these PKC isoforms had little effect on EGF stimulation of MAP kinase. As heparin inhibits PDGF and serum but not EGF stimulation of MAP kinase, there data precisely correlate heparin inhibition of MAP kinase with activation through PKC-dependent pathways. Immunoprecipitation analysis found that heparin inhibited serum, PMA, and PDGF but not EGF induced raf-1 phosphorylation. These studies demonstrate that heparin did not block PDGF-BB receptor activation, which initiates the mitogenic signalling cascade. Heparin did inhibit specific postreceptor second messenger signals, such as the late phase activation of MAP kinase, which may be mediated by suppression of PKC-dependent pathways.
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PMID:Mechanisms of inhibition by heparin of PDGF stimulated MAP kinase activation in vascular smooth muscle cells. 920 27

Glycosaminoglycans regulate angiogenesis by affecting the availability of different growth factors for the endothelial cell (EC). However, little is known about the molecular and functional consequences resulting from direct interaction of these polyelectrolytes with the EC. Here we show that heparin markedly inhibited serum-stimulated DNA synthesis and ornithine decarboxylase (ODC) mRNA expression in human endothelial cells (HEC). About 50% of the serum effect on DNA synthesis and ODC gene expression was prevented by the selective protein kinase C (PKC) inhibitor chelerythrine or by PKC down-regulation. Heparin was ineffective in counteracting that part of the effect of serum that was resistant to PKC inhibition or down-regulation. In serum-free cultured HEC, heparin completely abolished the increase in DNA synthesis and ODC mRNA expression elicited by a number of PKC activators. Cell exposure to difluoromethylornithine, an irreversible inhibitor of ODC enzyme, dramatically antagonised both serum- and phorbol 12-myristate 13-acetate (PMA)-stimulated DNA synthesis. These results suggest that inhibition of PKC-mediated ODC gene expression by glycosaminoglycans may represent an important mechanism in the regulation of HEC proliferation.
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PMID:Heparin inhibits phorbol ester-induced ornithine decarboxylase gene expression in endothelial cells. 950 49

1. To approach the mechanisms underlying desensitization of the opioid receptor-mediated Ca2+ channel inhibition, the effects of prolonged application of [D-Ala2, D-Leu5]enkephalin (DADLE) on Ba2+ currents (I(Ba)) through Ca2+ channels were analysed in NG108-15 neuroblastoma x glioma hybrid cells. 2. Inhibition of I(Ba) by 100 nM DADLE desensitized by 57% with a time constant of 4.4 min. 3. Maximal desensitization of the delta-opioid receptor-Ca2+ channel coupling was attained by 1 microM DADLE. The EC50 value for desensitization was estimated to be 78 nM. 4. RNA blot hybridization analysis and immunoblot analysis revealed the expression of beta-adrenoceptor kinase-1 (betaARK1) in NG108-15 cells. 5. Heparin, an inhibitor of betaARK, significantly reduced the magnitude and rate of desensitization, whereas Rp-cyclic AMPS and PKI (14-24)amide, inhibitors of cyclic AMP-dependent protein kinase (PKA), or long-term treatment with phorbol 12-myristate 13-acetate to induce down-regulation of protein kinase C (PKC) had no significant effect. 6. Recovery from desensitization (resensitization) proceeded with a time constant of 6.7 min. Okadaic acid, an inhibitor of serine/threonine phosphatases 1 and 2A, significantly attenuated the degree of resensitization. 7. In summary, we have characterized the time course and concentration-dependence of the desensitization of DADLE-induced I(Ba) inhibition in NG108-15 cells. This desensitization was reversible after removal of DADLE. It is suggested that betaARK, but neither PKA nor PKC, is involved in desensitization, while serine/threonine phosphatases mediate resensitization.
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PMID:Desensitization and resensitization of delta-opioid receptor-mediated Ca2+ channel inhibition in NG108-15 cells. 955 94

Vascular smooth muscle cell (VSMC) migration is an important process in the development of vascular occlusive disease. To investigate mitogen regulation of VSMC migration, a cell-layer-scrape assay was used to measure migration 20 h after stimulation of VSMC with platelet-derived growth factor-BB (PDGF-BB), insulin-like growth factor I (IGF-I), or phorbol 12-myristate 13-acetate (PMA). The contributions of cell proliferation were eliminated by treatment of VSMC with hydroxyurea, which suppressed DNA synthesis.PDGF-BB stimulated VSMC migration 2.5-fold, while PMA and IGF-I stimulated migration 1.7- and 1.5-fold, respectively. The importance of protein kinase C (PKC), ERK, and phosphoinositide-3' kinase (PI3 kinase) in mitogen-stimulated migration was investigated, using specific inhibitors of these signaling molecules. PDGF-BB-stimulated migration was inhibited by the general PKC inhibitor RO 31-8220 (40%), the MEK inhibitor PD98059 (31%), and the PI3 kinase inhibitor wortmannin (22%) but not by PMA-induced downregulation of conventional and novel PKC isoforms. IGF-I-stimulated migration was inhibited by RO 31-8220 (34%) and wortmannin (37%) but was much less affected by PD98059 (19%) or PKC downregulation (10%). PMA-stimulated migration was inhibited by RO 31-8220 (53%), PD98059 (50%), wortmannin (45%), and PKC downregulation (47%). Western analysis confirmed that ERK was strongly activated by PDGF-BB and PMA but not by IGF-I. To examine potential in vivo negative regulators of VSMC migration, we analyzed the ability of heparin, an analogue of heparan sulfate, and TGFbeta to attenuate mitogen-stimulated migration. Heparin but not TGFbeta inhibited VSMC migration stimulated by all three mitogens. Delayed-addition experiments showed that RO 31-8220 retained substantial inhibitory activity even if added 3 h after PMA or IGF-I stimulation and 5 h after PDGF-BB addition, suggesting that sustained PKC activation is important for migration. The MEK inhibitor retained some effectiveness for 5 h after PDGF-BB stimulation but only 1 h after PMA addition. Western analysis showed ERK activation was transient after PMA treatment but sustained for 6 h after PDGF-BB treatment. Heparin strongly inhibited migration even if added 5-7 h after mitogen stimulation, suggesting that heparin may inhibit both short- and long-term signals necessary for migration. The present studies indicate that PMA and IGF-I activate a limited number of second messengers resulting in moderate stimulation of migration; in contrast PDGF-BB stimulates multiple signaling pathways resulting in strong stimulation of migration and lessened sensitivity to inhibitory signals.
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PMID:Platelet-derived growth factor-BB, insulin-like growth factor-I, and phorbol ester activate different signaling pathways for stimulation of vascular smooth muscle cell migration. 968 41

In rat cerebellar slices, repetitive parallel fiber stimulation evokes an inward, postsynaptic current in Purkinje cells with a fast component mediated by alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate receptors and a slower component mediated by metabotropic glutamate receptors (mGluR). The mGluR-mediated excitatory postsynaptic current (mGluR-EPSC) is evoked selectively by parallel fiber stimulation; climbing fiber stimulation is ineffective. The mGluR-EPSC is elicited most effectively with increasing frequencies of parallel fiber stimulation, from a threshold of 10 Hz to a maximum response at approximately 100 Hz. The amplitude of the mGluR-EPSC is a linear function of the number of stimulus pulses without any apparent saturation, even with >10 pulses. Thus mGluRs at the parallel fiber-Purkinje cell synapse can function as linear detectors of the number of spikes in a burst of activity in parallel fibers. The mGluR-EPSC is present from postnatal day 15 and persists into adulthood. It is inhibited by the generic mGluR antagonist (RS)-a-methyl-4-carboxyphenylglycine and by the group I mGluR antagonist (RS)-1-aminoindan-1,5-dicarboxylic acid at a concentration selective for mGluR1. Although the intracellular transduction pathway involves a G protein, the putative mediators of mGluR1 (phospholipase C and protein kinase C) are not directly involved, indicating that the mGluR-EPSC studied here is mediated by a different and still unidentified second-messenger pathway. Heparin, a nonselective antagonist of inositol-trisphosphate (IP3) receptors, has no significant effect on the mGluR-EPSC, suggesting that also IP3 might be not required for the response. Buffering intracellular Ca2+ with a high concentration of bis-(o-aminophenoxy)-N,N,N', N'-tetraacetic acid partially inhibits the mGluR-EPSC, indicating that Ca2+ is not directly responsible for the response but that resting Ca2+ levels exert a tonic potentiating effect on the mGluR-EPSC.
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PMID:Postsynaptic current mediated by metabotropic glutamate receptors in cerebellar Purkinje cells. 970 47

Overexpression of protein kinase C-alpha and protein kinase C-delta has been shown to modulate a number of biological effects, including the cell growth and differentiation. We hypothesized that heparin, a potent antimitogenic drug, could affect the cell proliferation by inhibiting the expression of specific protein kinase C genes. Heparin, markedly but not completely, inhibited the serum-stimulated protein kinase C-alpha and -delta mRNA expression. Protein kinase C inhibition or down-regulation significantly decreased the serum-induced protein kinase C isoenzyme gene expression. Heparin failed to inhibit the residual effect of serum that was resistant to the above-mentioned treatments. Phorbol 12-myristate 13-acetate elicited an increase of protein kinase C isoenzyme gene expression that was completely prevented by protein kinase C inhibition or down-regulation. Heparin dose-dependently counteracted and ultimately abolished the increase in the protein kinase C isoenzyme gene expression elicited by phorbol 12-myristate 13-acetate. These results suggest that the inhibition of an autoregulatory role wielded by protein kinase C on the protein kinase C-alpha and -delta gene expression might represent a possible mechanism by which glycosaminoglycans modulate the cell growth.
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PMID:Heparin down-regulates the phorbol ester-induced protein kinase C gene expression in human endothelial cells: enzyme-mediated autoregulation of protein kinase C-alpha and -delta genes. 1033 19

Smooth muscle cells (SMCs) of the intima are generally quiescent and non proliferative. Their proliferation due to different stimulations occurs in myointimal hyperplasia and is regularly present in atherogenesis or after transluminal angioplasty leading to vascular occlusive stenosis. In the course of these pathologies, the Tissue Factor (TF) synthesis was upregulated and rapidly expressed at the membrane of the SMCs. Heparin is known to inhibit SMCs proliferation induced by FCS. We evaluated the inhibitory effect of heparin on the expression of TF induced by various mitogenic (FCS, PDGF-BB and EGF) and non-mitogenic (bacterial LPS) agents. Inhibition by heparin of SMCs proliferation induced by the same agonists was also determined. Quiescent human vascular SMCs from normal adult arteries were treated for 1 h by heparin and related sulfated polysaccharides before stimulation by the agonists. All the agonists up-regulated the expression of TF antigen and activity. TF expression induced by the growth factors was inhibited by heparin (IC 50: 10-30 microg/ml), and other sulfated polysaccharides (IC 50: 1-5 microg/ml). SMCs proliferation, late activation of the extracellular signal-regulated kinases (ERK1/2), and PKC activity were inhibited by heparin (IC 50: 30-50 microg/ml) in SMCs stimulated by FCS but not in SMCs treated by PDGF or EGF. In contrast, heparin had no effect on LPS-induced TF expression nor on LPS-induced PKC activation. These results indicate that, besides its well known effect on SMC proliferation, heparin displays an inhibitory effect on cell mediated blood clotting processes through regulation of the TF expression.
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PMID:Effects of heparin and related sulfated polysaccharides on tissue factor expression induced by mitogenic and non-mitogenic factors in human vascular smooth muscle cells. 1034 8

Low density lipoprotein (LDL) is a well-established risk factor for atherosclerosis, stimulating vascular smooth muscle cell (SMC) differentiation and proliferation, but the signal transduction pathways between LDL stimulation and cell proliferation are poorly understood. Because mitogen-activated protein kinases (MAPKs) play a crucial role in mediating cell growth, we studied the effect of LDL on the induction of MAPK phosphatase-1 (MKP-1) in human SMCs and found that LDL stimulated induction of MKP-1 mRNA and proteins in a time- and dose-dependent manner. Heparin, inhibiting LDL-receptor binding, did not influence LDL-stimulated MKP-1 mRNA expression, and human LDL also induced MKP-1 expression in rat SMCs and fibroblasts derived from LDL receptor-deficient mice, indicating an LDL receptor-independent process. Pretreatment of SMCs with pertussis toxin markedly inhibited LDL-induced MKP-1 expression. Depletion of protein kinase C (PKC) by phorbol 12-myristate 13 acetate or inhibition of PKC by calphostin C blocked MKP-1 induction, but the phospholipase C inhibitor U73122 had no effect. Pretreatment of SMCs with genistein or herbimycin A abrogated LDL-stimulated MKP-1 induction. The MAPK kinase inhibitor PD98059 abolished LDL-stimulated activation of extracellular signal-regulated protein kinases (ERKs) but not MKP-1 induction. Furthermore, constitutive expression of MKP-1 in vivo reduced LDL-induced expression of Elk-1-dependent reporter genes, and SMC lines overexpressing recombinant MKP-1 exhibited decreased ERK activities and retarded proliferation in response to LDL. Our findings demonstrate that LDL induces MKP-1 expression in SMCs via activation of PKC and tyrosine kinases, independent of LDL receptors and ERK-MAPKs, and that MKP-1 plays an important role in the regulation of LDL-initiated signal transductions leading to SMC proliferation.
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PMID:LDL stimulates mitogen-activated protein kinase phosphatase-1 expression, independent of LDL receptors, in vascular smooth muscle cells. 1044 64


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