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)

The release of arachidonic acid, and its subsequent conversion to thromboxane A2, is an important component of platelet activation. The precise mechanism of arachidonic acid release is unknown although cytosolic phospholipase A2 (cPLA2) has been implicated. In the present study the effects of three agonists, the serine protease thrombin, the protein kinase C stimulant PMA and the calcium ionophore A23187 have been examined on the translocation and phosphorylation of cPLA2 and these have been correlated with arachidonic acid release. Thrombin, but neither PMA nor A23187, caused the release of [14C]-arachidonic acid from unstirred, prelabeled platelets. Immunoblot analysis was carried out on cytosolic and membrane fractions from control and activated platelets using an anti-cPLA2 antibody. In platelets stimulated by thrombin or A23187, but not by PMA, there was a translocation of cPLA2 to the membrane fraction. Immunoprecipitation of cPLA2 from [32P]-ortho-phosphate-prelabeled platelets, indicated enhanced phosphorylation on serine residues of cPLA2 from thrombin- or PMA-stimulated platelets. These results are consistent with two synergistic pathways mediating cPLA2 activity. Increased cytosolic calcium causes the translocation of cPLA2 to the membrane, and protein kinase either directly, or indirectly, phosphorylates the enzyme. Activation of both pathways, as occurs in response to thrombin, is required for arachidonic acid liberation.
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PMID:Translocation and phosphorylation of cytosolic phospholipase A2 in activated platelets. 978 70

Expression of tissue factor (TF), a cellular initiator of the extrinsic coagulation cascade, is a feature of many malignant tumours and is intimately involved in the process of metastasis. SW-480 human colon adenocarcinoma cells responded to thrombin (1 U ml(-1)) or phorbol 12-myristate 13-acetate (PMA, 0.1 microM) with a 6.0-fold and a 7.7-fold increase in their procoagulant activity (PCA), respectively, after 4-6 h incubation in serum-free medium. The thrombin-enhanced PCA was significantly inhibited by complexing of thrombin with hirudin, or by serine protease inhibition with 3,4-dichloroisocoumarin. Both effects of thrombin and PMA on PCA in SW-480 cells were blocked by pretreatment of cells with cycloheximide or actinomycin D, indicating that the response required de novo protein and RNA synthesis. The thrombin-enhanced PCA depended on the activation of protein kinase C (PKC) as it was diminished by staurosporine and calphostin C. Moreover, stimulation of SW-480 cells by thrombin or PMA led to a significant increase in TF mRNA within 3 h as measured by the reverse-transcription PCR method, which was also dependent on the activation of PKC. The unaltered decay rate of thrombin-enhanced TF mRNA, evaluated after the addition of staurosporine, suggested that its inhibitory effect occurred at a transcription level. Our data suggest that thrombin enhances TF gene expression and protein synthesis in tumour cells in vitro via PKC activation. The induction of TF expression in tumour cells by thrombin indicates that tumour-associated PCA might have a positive-feedback effect on in vivo local propagation of thrombus by thrombin formation.
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PMID:Tissue factor activity of SW-480 human colon adenocarcinoma cells is modulated by thrombin and protein kinase C activation. 982 Jan 66

Our prior work shows that cultured BR cells derived from dog mastocytomas secrete the 92-kDa proenzyme form of gelatinase B. We provided a possible link between mast cell activation and metalloproteinase-mediated matrix degradation by demonstrating that alpha-chymase, a serine protease released from secretory granules by degranulating mast cells, converts progelatinase B to an enzymatically active form. The current work shows that these cells also secrete gelatinase A. Furthermore, gelatinases A and B both colocalize to alpha-chymase-expressing cells of canine airway, suggesting that normal mast cells are a source of gelatinases in the lung. In BR cells, gelatinase B and alpha-chymase expression are regulated, whereas gelatinase A expression is constitutive. Progelatinase B mRNA and enzyme expression are strongly induced by the critical mast cell growth factor, kit ligand, which is produced by fibroblasts and other stromal cells. Induction of progelatinase B is blocked by U-73122, Ro31-8220, and thapsigargin, implicating phospholipase C, protein kinase C, and Ca2+, respectively, in the kit ligand effect. The profibrotic cytokine TGF-beta virtually abolishes the gelatinase B mRNA signal and also attenuates kit ligand-mediated induction of gelatinase B expression, suggesting that an excess of TGF-beta in inflamed or injured tissues may alter mast cell expression of gelatinase B, which is implicated in extracellular matrix degradation, angiogenesis, and apoptosis. In summary, these data provide the first evidence that normal mast cells express gelatinases A and B and suggest pathways by which their regulated expression by mast cells can influence matrix remodeling and fibrosis.
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PMID:Mast cell expression of gelatinases A and B is regulated by kit ligand and TGF-beta. 1022 34

Bile acids were shown previously to inhibit proliferation and to induce monocytic differentiation in HL60 human acute promyelocytic leukemia cells (A. Zimber et al., Int. J. Cancer, 59: 71-77, 1994). In this report, we hypothesized that bile acids may exert a positive cooperativity with two known inducers of leukemic cell differentiation, all-trans retinoic acid and 1,25(OH)2-vitamin D3. Our results provide evidence that bile acids induced the monocytic differentiation of HL60 and THP-1 human leukemia cells exposed to ineffective concentrations of these inducers. The protein kinase C (PKC) inhibitors H-7 (10 and 20 microM) and staurosporine (5 and 20 nM) modulated the effects of bile acids on HL60 cell differentiation. Most interestingly, bile acids are shown herein to down-regulate the expression of the serine protease myeloblastin gene involved in the differentiation of myeloid hematopoietic cells. In agreement with the recent identification of nuclear receptors for bile acids, our data suggest that functional interactions between nuclear bile acid signaling pathways, PKC, and nuclear receptors for retinoic acid and vitamin D3 are involved in the down-regulation of the myeloblastin gene and the induction of cell differentiation in human leukemic cells.
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PMID:Functional interactions between bile acids, all-trans retinoic acid, and 1,25-dihydroxy-vitamin D3 on monocytic differentiation and myeloblastin gene down-regulation in HL60 and THP-1 human leukemia cells. 1067 52

In the present study, we investigated the role of caspase-3/CPP32 and serine protease(s) in cell death induced by TNF-alpha in SNU-16 human gastric adenocarcinoma cells. Apoptosis induced in SNU-16 cells by TNF-alpha was accompanied by the activation of caspase-3/CPP32. After treatment with TNF-alpha, PKCdelta cleaved to its characteristic 40 kDa fragment in a caspase-3/CPP32 dependent manner. Incubation with z-DEVD-fmk completely abrogated TNF-alpha-induced DNA fragmentation, indicating that activation of caspase-3/CPP32 was crucially involved in TNF-alpha-induced apoptosis. In addition, serine protease inhibitor, 4-(2-aminoethyl)benzenesulfonyl fluoride (AEBSF), clearly inhibited all the features of apoptosis including DNA fragmentation and chromatin condensation. Furthermore, in the AEBSF treated SNU-16 cells, only intact PKCdelta was detected by immunoblot analysis, suggesting that activation of caspase-3/CPP32 was blocked. Thus, the AEBSF-sensitive step may involve an upstream caspase-3/CPP32 protease activation. Taken together, these results suggest that both caspase-3/CPP32 and serine protease(s) are activated and play an important role in TNF-alpha induced apoptosis in SNU-16 cells.
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PMID:TNF-alpha induces apoptosis mediated by AEBSF-sensitive serine protease(s) that may involve upstream caspase-3/CPP32 protease activation in a human gastric cancer cell line. 1081 2

The serine proteinases plasmin and thrombin convert proenzyme matrix metalloproteinases (MMPs) into catalytically active forms. In addition, we demonstrate that plasmin(ogen) and thrombin induce a significant increase in secretion of activated murine macrophage elastase (MMP-12) protein. Active serine protease is responsible for induction, as demonstrated by the absence of MMP-12 induction in plasminogen(Plg)-treated urokinase-type plasminogen activator-deficient macrophages. Since increased MMP-12 protein secretion was not accompanied by an increase in MMP-12 mRNA, we examined post-translational mechanisms. Protein synthesis was not required for early release of MMP-12 but was required for later secretion of activated enzyme. Immunofluorescent microscopy demonstrated basal expression in macrophages that increased following serine proteinase exposure. Inhibition of MMP-12 secretion by hirudin and pertussis toxin demonstrated a role for the thrombin G protein-coupled receptor (protease-activated receptor 1 (PAR-1)). PAR-1-activating peptides were able to induce MMP-12 release. Investigation of signal transduction pathways involved in this response demonstrate the requirement for protein kinase C, but not tyrosine kinase, activity. These data demonstrate that plasmin and thrombin regulate MMP-12 activity through distinct mechanisms: post-translational secretion of preformed MMP-12 protein, induction of protein secretion that is protein kinase C-mediated, and extracellular enzyme activation. Most importantly, we show that serine proteinase MMP-12 regulation in macrophages occurs via the protein kinase C-activating G protein-coupled receptor PAR-1.
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PMID:Proteinase-activated receptor-1 regulation of macrophage elastase (MMP-12) secretion by serine proteinases. 1099 90

Phorbol 12-myristate 13-acetate (PMA) rapidly induced cell death in SNU-16 gastric adenocarcinoma cells. DNA ladder formation and caspase-3/CPP32 activation were observed in PMA treated cells indicating that PMA induces apoptosis. z-DEVD-fmk, specific inhibitor of caspase-3/CPP32, inhibited the induction of apoptosis by PMA, demonstrating that caspase/CPP32 are critically involved in PMA-induced apoptosis. The serine protein inhibitor 4-(2-aminoethyl)benzenesulfonyl fluoride effectively blocked apoptosis, and also prevented caspase-3/CPP32 activation. Go6983, a specific inhibitor of PKC, almost completely suppressed apoptosis and caspase-3/CPP32 activation. Furthermore, 1,2-dihexanoyl-sn-glycerol, an endogenous activator of PKC, induced apoptosis detected by DNA fragmentation and Hoechst 33258 nuclear staining. From these results, we conclude that PMA is not only a tumor promoter, but can also induce apoptosis in gastric cancer cells. PMA-induced apoptosis appears to be mediated through activation of protein kinase C, and the activation of serine protease(s) and caspase-3/CPP32 may be the molecular mechanisms by which PMA induces apoptosis.
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PMID:Protein kinase C activation by PMA rapidly induces apoptosis through caspase-3/CPP32 and serine protease(s) in a gastric cancer cell line. 1129 59

Intraglomerular activation of the coagulation cascade is a common feature of mesangioproliferative glomerulonephritis. Besides thrombin, very little is known about the cellular effects of other components of the coagulation system. This study investigated the effect of activated factor X (FXa) on cultured human mesangial cells. This serine protease induced a significant and dose-dependent increase in DNA synthesis. In addition to its mitogenic effect, FXa caused a striking upregulation of platelet-derived growth factor (PDGF) A and B chain gene expression. Next, the intracellular mitogenic signaling pathways activated by FXa were investigated. FXa induced a rapid spike in cytosolic calcium concentration followed by a sustained plateau. This response was not influenced by the downregulation of thrombin receptors. In addition, FXa stimulated a significant upregulation of different tyrosine-phosphorylated proteins. One of these phosphorylated cellular proteins was represented by the c-jun N-terminal kinase, a member of the mitogen-activated protein kinase family. To evaluate the role of FXa enzymatic activity and of PDGF autocrine secretion, FXa-induced DNA synthesis was studied in the presence of leupeptin, a specific serine protease inhibitor, and neutralizing anti-PDGF antibody. To investigate the role of tyrosine kinase (TK) activation on FXa mitogenic effect, FXa-stimulated thymidine uptake was evaluated in the presence of genistein and herbimycin A, two powerful and specific TK inhibitors. FXa-elicited DNA synthesis was also examined after protein kinase C (PKC) downregulation by prolonged incubation with phorbol-12-myristate-13-acetate to study the influence of the phospholipase C-PKC axis. The proliferative effect of FXa required its proteolytic activity, and the activation of TK was only partially dependent on PKC activation while it was PDGF independent. Finally, it was shown by reverse transcription-PCR that mesangial cells do not express the signaling splicing variant of the putative FXa receptor, effector protease receptor-1. In conclusion, the present study demonstrated that FXa is a powerful mitogenic factor for human mesangial cells, and it induces its cellular effect not through effector protease receptor-1, but most likely by binding a protease-activated receptor and activating phospholipase C-PKC and TK signaling pathways.
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PMID:Activated coagulation factor X: a novel mitogenic stimulus for human mesangial cells. 1131 47

Airway remodeling with smooth muscle cell (SMC) hyperplasia is a feature of chronic asthma. We investigated the potential for tryptase, the major secretory product of human mast cells, to act as a growth factor for human airway SMCs. Because this serine protease can activate proteinase-activated receptor-2 (PAR-2), we also examined the actions of SLIGKV, a peptide agonist of PAR-2. Incubation with lung tryptase provoked a twofold increase in [(3)H]thymidine incorporation; a similar increase in cell numbers was found when we used the MTS assay. The effect was catalytic site dependent, being abolished by the protease inhibitors leupeptin and benzamidine and by heat inactivation of the enzyme. Tryptase-induced DNA synthesis was inhibited by preincubation of the cells with pertussis toxin, calphostin C, or genistein. Transduction mechanisms are thus likely to involve a pertussis toxin-sensitive G protein, protein kinase C, and tyrosine kinase. SLIGKV elicited a response on SMCs similar to that of tryptase. Tryptase could provide an important stimulus for SMC proliferation in asthmatic airways, by acting on PAR-2.
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PMID:Tryptase and agonists of PAR-2 induce the proliferation of human airway smooth muscle cells. 1150 38

Resistance of tumor cells to lysis by complement is generally attributed to several protective mechanisms. The relative impact of these mechanisms in the same tumor cell, however, has not been assessed yet. We have analyzed the interaction of the human erythroleukemia tumor cell line K562 with human complement. K562 cells express the membrane complement regulatory proteins CD59, CD55 and CD46. As shown here for the first time, K562 also spontaneously release the soluble regulators C1 inhibitor, factor H, and soluble CD59. Complement resistance of K562 cells is augmented upon treatment with PMA, TNF or even with sublytic complement. Unlike TNF and sublytic complement, PMA enhanced the expression of membrane-bound CD55 and CD59 and led to increased secretion of soluble CD59. In addition, we show that complement-resistant K562 cells express a membrane-associated proteolytic activity, higher than the complement-sensitive K562/S cells. Treatment of complement-resistant K562 cells with serine protease inhibitors enhance their sensitivity to complement-mediated lysis. Inhibitors of protein kinase C (PKC) also sensitize K562 cells to complement lysis, implicating PKC-mediated signaling in cell resistance to complement. Neutralization of the CD55 and CD59 but not of CD46 regulatory activity with specific antibodies significantly increases complement-mediated K562 cell lysis. Treatment of K562 cells with a mixture of inhibitory reagents results in a significant additive enhancing effect on complement-mediated lysis of K562. In conclusion, K562 cells resist a complement attack by concomitantly using multiple molecular evasion strategies. Future attempts in antibody-based tumor therapy should include strategies to interfere with those resistance mechanisms.
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PMID:K562 erythroleukemic cells are equipped with multiple mechanisms of resistance to lysis by complement. 1151 47


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