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 histidine decarboxylase (HDC) gene is regulated transcriptionally by gastrin and phorbol 12-myristate 13-acetate (PMA) through a protein kinase C (PKC)-related pathway. To determine the role of AP-1 (fos/jun) in the regulation of the HDC promoter, gastric cancer (AGS-B) cells stably expressing the cholecystokinin-B/ gastrin receptor and the 1.8-kb human (h) HDC-luciferase (luc) construct were cotransfected with constructs expressing c-fos and c-jun. Overexpression of c-fos and c-jun activated the HDC promoter in a dose-dependent fashion in 1.8-kb hHDC-luc/AGS-B cells as well as in transfected F9 embryonal carcinoma cells, which lack endogenous AP-1 activity. PMA was unable to activate the HDC promoter in F9 cells, which were not transfected with c-fos and c-jun. Gastrin stimulation increased c-fos and c-jun mRNA abundance and AP-1-dependent transcriptional activity, as assessed by a reporter construct in which the CAT reporter gene is under the control of a 12-O-tetradecanoylphorbol-13-acetate response element multimer. Gastrin-stimulated HDC promoter activity was blocked by transfection of c-fos antisense and dominant negative c-jun expression constructs. Finally, overexpression of c-fos and c-jun activated the hHDC promoter through a downstream cis-acting element (gastrin response element), which does not bind AP-1. In conclusion, activation of AP-1 is essential for gastrin-stimulated HDC transcription, but the mechanism appears to be indirect.
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PMID:Gastrin regulates the human histidine decarboxylase promoter through an AP-1-dependent mechanism. 914 14

The proliferative effects of gastrin on normal and neoplastic gastro-intestinal tissues have been shown to be mediated by the gastrin/CCKB (G/CCKB) G-protein-coupled receptors. We have recently reported that gastrin stimulates the tyrosine phosphorylation of Shc proteins and their subsequent association with the Grb2/Sos complex, leading to mitogen-activated protein kinase (MAPK) activation, a pathway known to play an important role in cell proliferation. We undertook the present study to characterize the signalling pathways used by this receptor to mediate the activation of the Shc/Grb2 complex. Since G/CCKB receptor occupancy leads to the activation of the phospholipase C (PLC)/protein kinase C (PKC) pathway, we examined whether PKC stimulation and Ca2+ mobilization contribute to the phosphorylation of Shc proteins and their association with Grb2 in response to gastrin. Our results indicate that Shc proteins are tyrosine phosphorylated and associate with Grb2 in response to phorbol esters, suggesting that activation of PKC is a potential signalling pathway leading to activation of the Shc/Grb2 complex. Inhibition of PKC by GF109203X completely blocked the effect of PMA on Shc tyrosine phosphorylation and its subsequent association with Grb2, but had a partial inhibitory effect on the response to gastrin. Depletion of the intracellular Ca2+ pools by treatment with thapsigargin blocked the increase in intracellular free calcium concentration induced by gastrin and diminished the ability of the peptide to stimulate Shc phosphorylation and recruitment of Grb2. In addition, removal of extracellular Ca2+ partially inhibited the effect of gastrin on Shc phosphorylation as well as its association with Grb2, indicating that the effects of gastrin are also mediated by Ca2+-dependent mechanisms. Furthermore, we show that blockage of the two major early signals generated by activation of PLC, which induced the activation of the Shc/Grb2 complex, also blocked gastrin-induced MAPK activation.
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PMID:Ca2+ and protein kinase C-dependent mechanisms involved in gastrin-induced Shc/Grb2 complex formation and P44-mitogen-activated protein kinase activation. 923 Jan 17

Bombesin-like peptides, including the mammalian homologue gastrin-releasing peptides, are highly expressed and secreted by neuroendocrine cells in prostate carcinoma (PCa) tissues and are likely to be related to the progression of this disease. In the present study, we show that bombesin enhances the migration of androgen-independent PCa cells (PC-3) in vitro, while not affecting their adhesion to extracellular matrix proteins. The bombesin-increased motility of PC-3 cells occurs through its receptor, and, as shown with inhibitors, it likely requires activation of both protein tyrosine kinases (PTKs) and protein kinases C (PKCs). Because the focal adhesion kinase pp125FAK plays a key role in adhesion/motility and is highly expressed in advanced PCa, we examined whether in PC-3 cells bombesin signal transduction triggers the tyrosine phosphorylation of this PTK and of associated integrins and signaling proteins likely to be present in focal adhesion plaques. pp125FAK tyrosine phosphorylation was stimulated by bombesin and mimicked by PKC activation with the tumor-promotor phorbol 12-myristate-13-acetate (PMA). Moreover, this effect of bombesin on pp125FAK tyrosine phosphorylation requires the presence of both active PKC and cytoskeleton integrity since this signal was abolished by down-regulating PKCs induced by prolonged PMA treatment or by PKC inhibition with GF 109203X, as well as by disruption of the cytoskeleton with cytochalasin D. We also show that bombesin increases the tyrosine phosphorylation of a 95-kDa protein (pp95) which was co-immunoprecipitated with the alpha v and beta (3 and 5) subunits, forming integrin receptors with alpha v in PC-3 cells. The protein pp95 is distinct from the endogenously tyrosine-phosphorylated beta3 subunit. In addition, upon bombesin treatment, the beta1, beta3 and beta5 integrin subunits co-immunoprecipitated with pp125FAK and major phosphotyrosine (pY)-containing proteins of 125 and 68-70 kDa, likely corresponding to pp125FAK and paxillin. Together our data suggest that, in addition to PKC activation, tyrosine phosphorylation of pp125FAK and integrin-associated proteins may play an important role in bombesin signaling, triggering the processes of PCa cell motility and invasion.
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PMID:Bombesin stimulates the motility of human prostate-carcinoma cells through tyrosine phosphorylation of focal adhesion kinase and of integrin-associated proteins. 924 95

Isolated canine G cells in primary culture have been used to study calcium, protein kinase C (PKC), and rho/cytoskeletal-dependent intracellular pathways involved in bombesin- stimulated gastrin release. A method to obtain highly purified G cells by culture (64% G cells) after flow cytometry on elutriated fractions of cells from digested canine gastric antral mucosa has been developed. Pretreatment of G cells with thapsigargin (10(-8)-10(-6) M) and release experiments in Ca2+-containing or -depleted media showed that influx of Ca2+ into the cells and not acute release from intracellular stores plays an important role in bombesin-stimulated gastrin release. Inhibition of PKC by the specific inhibitor GF 109 203X did not affect bombesin-stimulated release. Rho, a small GTP-binding protein that regulates the actin cytoskeleton, is specifically antagonized by Clostridium botulinum C3 exoenzyme. C3 (10 microg/ml) enhanced basal and bombesin-stimulated gastrin release by 315 and 266%, respectively. The importance of the cytoskeleton for regulation of gastrin release was emphasized by a more pronounced release of gastrin when the organization of the actin cytoskeleton was disrupted by cytochalasin D (5 x 10(-)7 and 10(-)6 M). Wortmannin, a potent inhibitor of phosphoinositide-3-kinase, did not alter bombesin-stimulated gastrin release. Thus, it is concluded that bombesin-induced gastrin release from canine G cells is stimulated by Ca2+ but not by PKC, and is enhanced by disruption of rho/cytoskeletal pathways.
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PMID:Bombesin-induced gastrin release from canine G cells is stimulated by Ca2+ but not by protein kinase C, and is enhanced by disruption of rho/cytoskeletal pathways. 927 20

Protein kinase D (PKD) is a serine/threonine protein kinase that is activated by phorbol esters via protein kinase C in intact cells. To assess the physiological significance of this putative pathway, we examined the regulation of PKD in living cells by mitogenic regulatory peptides and by platelet-derived growth factors (PDGF). Our results demonstrate that bombesin rapidly induces PKD activation in Swiss 3T3 cells, as shown by autophosphorylation and syntide-2 phosphorylation assays. Maximum PKD activation (14-fold above base-line levels) was obtained 90 s after bombesin stimulation. Bombesin also induced PKD activation in Rat-1 cells stably transfected with the bombesin/gastrin releasing peptide (GRP) receptor and in COS-7 cells transiently co-transfected with PKD and bombesin/GRP receptor expression constructs. No inducible kinase activity was demonstrated when COS-7 cells were transfected with a kinase-deficient PKD mutant. Bombesin-mediated PKD activation was prevented by treatment of Swiss 3T3 cells with the protein kinase C inhibitors GF 1092030X and Ro 31-8220. In contrast, these compounds did not inhibit PKD activity when added directly in vitro. Vasopressin, endothelin, and bradykinin also activated PKD in Swiss 3T3 cells through a PKC-dependent pathway. Platelet-derived growth factor-stimulated PKD activation in Swiss 3T3 cells and in porcine aortic endothelial cells stably transfected with PDGF-beta receptors. Treatment with GF 1092030X or Ro 31-8220 inhibited PKD activation induced by PDGF. Thus, our results indicate that PKD is activated by multiple signaling peptides through a protein kinase C-dependent signal transduction pathway in a variety of cell types.
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PMID:Bombesin, vasopressin, endothelin, bradykinin, and platelet-derived growth factor rapidly activate protein kinase D through a protein kinase C-dependent signal transduction pathway. 929 46

We have previously observed that gastrin has a cholecystokinin B (CCK-B) receptor-mediated growth-promoting effect on the AR42J rat pancreatic acinar cell line and that this effect is paralleled by induction of expression of the early response gene c-fos. We undertook these experiments to elucidate the mechanism for induction of c-fos and the linkage of this action to the trophic effects of gastrin. Gastrin (0.1-10 nM) dose dependently induced luciferase activity in AR42J cells transfected with a construct consisting of a luciferase reporter gene coupled to the serum response element (SRE) of the c-fos promoter. This effect was blocked by the specific CCK-B receptor antagonist D2 but not by the specific CCK-A receptor antagonist L-364,718 or by pertussis toxin, indicating that gastrin targets the SRE via specific CCK-B receptors through a mechanism independent of Gi. Inhibition of protein kinase C (PKC) either by prolonged (24 h) exposure of the cells to the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (100 nM) or by incubation with the selective inhibitor GF-109203X (3.5 microM) resulted in an 80% reduction in luciferase activity. Similar results were observed in the presence of the specific extracellular signal-regulated kinase (ERK) kinase (MEK) inhibitor PD-98059 (50 microM). We measured ERK2 activity in AR42J cells via in-gel kinase assays and observed that gastrin (1 pM-100 nM) induced ERK2 enzyme activity in a dose-dependent manner. Addition of GF-109203X and PD-98059, either alone or in combination, produced, respectively, partial and total inhibition of gastrin-induced ERK2 activity. Gastrin induction of ERK2 activity also resulted in a threefold increase in the transcriptional activity of Elk-1, a factor known to bind to the c-fos SRE and to be phosphorylated and activated by ERK2. PD-98059 blocked the growth-promoting effect of gastrin on the AR42J cells, demonstrating that this effect depends on activation of MEK. Our data lead us to conclude that the trophic actions of gastrin are mediated by ERK2-induced c-fos gene expression via PKC-dependent and -independent pathways.
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PMID:Molecular mechanisms for the growth factor action of gastrin. 935 32

The parietal cell has three types of activating receptors for acid secretion on its basolateral membrane, i.e., histamine H2, acetylcholine M3, and gastrin CCKB. Activation of acid secretion is achieved by two concomitant functional changes namely: (i) tubulovesicles fuse with the apical secretory membrane, thus recruiting functional pumps to the expanded microvillar surface, and (ii) the apical membrane acquires a permeability to KCl. The major path for parietal cell stimulation is via H2-receptor-mediated adenylate cyclase and elevation of cAMP to activate protein kinase A (PKA), which phosphorylates key effector proteins, e.g., ezrin, a membrane-cytoskeletal linker, apical Cl- or K(+)-channels. Ca2+ is liberated from intracellular stores by IP3, which in turn is the result of M3-, CCKB-, or possibly H2-coupled activation of phospholipase C. The resulting protein kinase C activation may have both inhibitory and excitatory roles. Elevated Ca2+ activates calmodulin-dependent kinases, e.g., calmodulin kinase II and myosin light chain kinase, that could promote vesicular motor activity. Ezrin is considered to play a main role in the vesicular transport system of the parietal cell. The regulation might be conducted through the phosphorylation of the molecule to modify its property to interact with the cytoskeletal components, membranes or membrane proteins.
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PMID:[Signal transduction and intracellular recruitment of gastric proton pump in the parietal cell]. 950 88

Oxidant stress is thought to play a role in the pathogenesis of many gastric disorders. We have recently reported that histidine decarboxylase (HDC) promoter activity is stimulated by gastrin through a protein kinase C- and extracellular signal-regulating kinase (ERK)-dependent pathway in gastric cancer (AGS-B) cells, and this transcriptional response is mediated by a downstream cis-acting element, the gastrin response element (GAS-RE). To study the mechanism through which oxidant stress affects gastric cells, we examined the effects of hydrogen peroxide (H2O2) on HDC promoter activity and intracellular signaling in AGS-B cells. H2O2 (10 mM) specifically activated the HDC promoter 10-12-fold, and this activation was blocked by both mannitol and N-acetylcysteine. Hydrogen peroxide treatment of AGS-B cells increased the phosphorylation and kinase activity of ERK-1 and ERK-2, but did not affect Jun kinase tyrosine phosphorylation or kinase activity. In addition, treatment of AGS-B cells with H2O2 resulted in increased c-fos/c-jun mRNA expression and AP-1 activity, and also led to increased phosphorylation of epidermal growth factor receptor (EGFR) and Shc. H2O2-dependent stimulation of HDC promoter activity was completely inhibited by kinase-deficient ERKs, dominant-negative (N17 and N15) Ras, and dominant-negative Raf, and partially blocked by a dominant-negative EGFR mutant. In contrast, protein kinase C blockade did not inhibit H2O2-dependent induction of the HDC promoter. Finally, deletion analysis demonstrated that the H2O2 response element could be mapped to the GAS-RE (nucleotides 2 to 24) of the basal HDC promoter. Overall, these studies suggest that oxidant stress activates the HDC promoter through the GAS-RE, and through an Ras-, Raf-, and ERK-dependent pathway at least partially involving the EGFR.
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PMID:Oxidative stress activates the human histidine decarboxylase promoter in AGS gastric cancer cells. 972 30

We previously observed that the trophic actions of gastrin (G17) on the AR42J rat acinar cell line are mediated by mitogen-activated protein kinase (MAPK)-induced c-fos gene transcription via protein kinase C (PKC)-dependent and -independent pathways. In this study, we further investigated the signaling pathways that target c-fos in response to G17. G17 led to a sixfold induction in luciferase activity in cells transfected with plasmids containing the -356+109 sequence of the murine c-fos promoter, which includes the Sis-inducible element (SIE), serum response element (SRE), and the Ca2+/cAMP response element (CRE) regulatory elements. Addition of either the selective PKC inhibitor GF-109203X or the MAPK/extracellular signal-regulated kinase inhibitor PD-98059 resulted in an 80% reduction in luciferase activity. G17 induced the transcriptional activity of both Elk-1 and Sap-1a, transcription factors that bind to the E26 transformation specific (Ets) DNA sequence of the SRE, and this effect was inhibited by both GF-109203X and PD-98059. Point mutations in the Ets sequence led to a 4-fold induction of c-fos transcription stimulated by G17 and to a 1.3-fold induction in response to epidermal growth factor (EGF). In contrast, mutations in the CA rich G (CArG) sequence of the SRE prevented transcriptional activation by both G17 and EGF. G17 induction of the Ets mutant construct was unaffected by either GF-109203X or PD-98059. Because activation of the SRE involves the small GTP-binding protein Rho A, we examined the role of Rho A in G17 induction of c-fos transcription. Inactivation of Rho A by either the specific inhibitor C3 or by expression of a dominant negative Rho A gene inhibited G17 induction of both the wild-type and the Ets mutant constructs by 60%. C3 also inhibited G17-stimulated AR42J cell proliferation. Thus G17 targets the c-fos promoter CArG sequence via Rho A-dependent pathways, and Rho A appears to play an important role in the regulation of the trophic action of G17.
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PMID:Gastrin induces c-fos gene transcription via multiple signaling pathways. 995 Aug 15

Two of the most effective stimuli of gastrin release from human antral G cells are bombesin and phorbol esters. Both agonists result in activation of the protein kinase C family of isozymes, however, the exact contribution of protein kinase C to the resultant release of gastrin has been difficult to assess, possibly due to the presence of multiple protein kinase C isozymes in the G cells. The results of the present study demonstrated that the human antral G cells expressed 6 protein kinase C isozymes alpha, gamma, theta, epsilon, zeta, and mu. Of these protein kinase C, gamma and theta were translocated by stimulation of the cells by either 10 nM bombesin or 1 nM phorbol ester. Inhibition of protein kinase Cmu (localized to the Golgi complex) did not decrease bombesin-stimulated gastrin release indicating that this isozyme was not involved in the secretory process. The use of selective antagonists of the calcium-sensitive conventional protein kinase C subgroup resulted in an increase in bombesin-stimulated gastrin release and indicated that protein kinase Cgamma was involved in the desensitization of the bombesin response.
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PMID:The role of protein kinase C isozymes in bombesin-stimulated gastrin release from human antral gastrin cells. 1042 25


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