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Query: UNIPROT:P51812 (mitogen-activated protein)
 10,636 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cholecystokinin (CCK) has recently been shown to activate mitogen-activated protein (MAP) kinase in rat pancreatic acini [Duan and Williams, Am. J. Physiol. 267 (Gastrointest. Liver Physiol. 30): G401-G408, 1994]. To evaluate the mechanism of MAP kinase activation, we studied the effects of CCK on MAP kinase kinase (MEK) in rat pancreatic acini. Two forms of MEK were identified by immunoblotting, using antibodies specific to MEK1 and MEK2. MEK activity in acinar extracts and after immunoprecipitation with anti-MEK was detected using a recombinant fusion protein, glutathione S-transferase-MAP kinase, as a substrate. MEK activity rapidly increased after stimulation of acini by CCK, with significant stimulation at 1 min and a maximal effect at 5 min, followed by a slow decline to slightly above control levels after 30 min. The threshold concentration of CCK was approximately 10 pM, and the maximal effect was induced by 1 nM CCK, which increased MEK activity by 120%. In addition to CCK, bombesin and carbachol, but not secretin or vasoactive intestinal peptide, enhanced MEK activity. Phorbol ester mimicked the effect of CCK, whereas ionomycin and thapsigargin failed to activate MEK. We further studied the activation of Ras, an important component leading to activation of MEK by growth factors. Ras in acini was immunoprecipitated and identified by Western blotting. CCK and 12-O-tetradecanoylphorbol-13-acetate stimulated the incorporation of GTP into Ras, a requirement for its activation, reaching a maximum at 10 min of approximately 120% over control. In conclusion, the activation of MAP kinase by CCK can be explained by activation of MEK and may involve the activation of Ras by a protein kinase C-dependent mechanism.
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PMID:Activation of MAP kinase kinase (MEK) and Ras by cholecystokinin in rat pancreatic acini. 761 6

The existence and activation of mitogen-activated protein (MAP) kinase in isolated pancreatic acini have been demonstrated. Immunoblotting and immunoprecipitation revealed two forms of MAP kinase in pancreatic acini, with relative molecular masses of approximately 42 and 44 kDa. Both forms of MAP kinase were activated by cholecystokinin (CCK). The threshold concentration of CCK was approximately 3 pM, and the maximal effect occurred at 1 nM, which enhanced MAP kinase activity by 2.5-fold, as determined in polyacrylamide gel copolymerized with substrate myelin basic protein. Activation of MAP kinase by CCK was rapid, reaching a maximum within 5-10 min that subsequently declined. Bombesin and carbachol but not secretin or vasoactive intestinal peptide also activated MAP kinase. CCK-induced activation of MAP kinase may be mediated by protein kinase C, since 12-O-tetradecanoylphorbol 13-acetate (TPA) mimicked the effect of CCK and staurosporine concentration dependently inhibited the action of CCK. Treatment of acini with thapsigargin, ionomycin, or ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid did not influence MAP kinase, indicating that mobilization of intracellular calcium by CCK is not important in activation of acinar MAP kinase. CCK and TPA increased tyrosine phosphorylation of both 42- and 44-kDa forms. Genistein and tyrphostin 23, the inhibitors of tyrosine kinase, suppressed the activation of MAP kinase by CCK. In conclusion, MAP kinase in pancreatic acini is activated by agonists related to hydrolysis of phosphoinositide, via a mechanism involving protein kinase C and tyrosine kinase.
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PMID:Cholecystokinin rapidly activates mitogen-activated protein kinase in rat pancreatic acini. 794 37

The neuro-intestinal peptide hormone cholecystokinin (CCK)/gastrin has been suggested to have a trophic effect on gastro-intestinal tract in vivo as well as in vitro. In the present study, the human CCK-B/gastrin receptor was expressed in mouse NIH3T3 fibroblasts to investigate the molecular basis of signal transduction pathway of the guanine nucleotide regulatory protein (G protein)-coupled receptor. Human CCK-B/gastrin receptor expressed in NIH3T3 cells coupled efficiently to phosphoinositide hydrolysis and mobilization of intracellular Ca2+, and transduced mitogenic signals assessed by [3H]thymidine incorporation in a dose-dependent manner. Moreover, CCK-8 or gastrin I alone promoted the cell growth in serum-free medium. CCK-8 induced tyrosine phosphorylation of several protein species. Among them, mitogen-activated protein (MAP) kinase was tyrosine phosphorylated and activated in response to CCK-8, as was induced by platelet-derived growth factor (PDGF). In contrast, tyrosine phosphorylation of p125FAK (focal adhesion kinase) was induced by CCK-8 but not by PDGF. CCK-8 as well as gastrin I induced the expression of early responsive genes such as c-fos and c-myc. These results suggest that CCK-B/gastrin receptors might transmit mitogenic signals by cross-talking with the tyrosine kinase cascades.
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PMID:Cholecystokinin-B/gastrin receptor signaling pathway involves tyrosine phosphorylations of p125FAK and p42MAP. 810 29

Stimulation of pancreatic acini from male Sprague-Dawley rats by both cholecystokinin (CCK)-8 and anisomycin caused an increase in p46jnk and p55jnk activities. Both forms of c-Jun amino-terminal kinase (JNK) were slightly activated at 5 min, reached a maximum at 30 min, and remained significantly increased at 60 min of CCK stimulation. By contrast, p42mapkwas activated fully by 5 min. In pancreatic acini stimulated with different concentrations of CCK for 30 min, the minimal and maximal JNK responses were observed at 30 pm and 100 nM CCK, respectively; p42mapk activation was, as previously reported, much more sensitive, with maximal activation by 1 nm CCK. Carbachol and bombesin also stimulated JNK activity, while vasoactive intestinal peptide did not. Neither activating protein kinase C nor increasing intracellular Ca2+ significantly activated JNK. In in vivo experiments, rats were infused intravenously for 5 and 15 min with a secretory (0.1 microg/kg/h) or supramaximal (10 microg/kg/h) dose of the CCK analog caerulein (CER). Secretory doses of CER induced a 4-fold increase of both forms of JNK in pancreatic tissue at 5 and 15 min, while at the same time points, supramaximal stimulation with CER caused 4- and 27-fold increases, respectively, of these kinase activities. The secretory dose of CER slightly increased the activities of both forms of mitogen-activated protein kinase, while the supramaximal dose induced a 10-fold increase of p42mapk at 5 min. In conclusion, JNKs and mitogen-activated protein kinases are rapidly activated in rat pancreatic acini stimulated with CCK as well as in pancreatic tissue during in vivo stimulation with CER. The large response to supramaximal CER stimulation may be of importance in the early pathogenesis of acute pancreatitis.
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PMID:Jun kinases are rapidly activated by cholecystokinin in rat pancreas both in vitro and in vivo. 862 33

We investigated cell proliferation modulated by cholecystokinin (CCK) and somatostatin analogue RC-160 in CHO cells bearing endogenous CCKA receptors and stably transfected by human subtype sst5 somatostatin receptor. CCK stimulated cell proliferation of CHO cells. This effect was suppressed by inhibitor of the soluble guanylate cyclase, LY 83583, the inhibitor of the cGMP dependent kinases, KT 5823, and the inhibitor of mitogen-activated protein (MAP) kinase kinase, PD 98059. CCK treatment induced an increase of intracellular cGMP concentrations, but concomitant addition of LY 83583 virtually suppressed this increase. CCK also activated both phosphorylation and activity of p42-MAP kinase; these effects were inhibited by KT 5823. All the effects of CCK depended on a pertussis toxin-dependent G protein. Somatostatin analogue RC-160 inhibited CCK-induced stimulation of cell proliferation but it did not potentiate the suppressive effect of the inhibitors LY 83583 and KT 5823. RC-160 inhibited both CCK-induced intracellular cGMP formation as well as activation of p42-MAP kinase phosphorylation and activity. This inhibitory effect was observed at doses of RC-160 similar to those necessary to occupy the sst5 recombinant receptor and to inhibit CCK-induced cell proliferation. We conclude that, in CHO cells, the proliferation and the MAP kinase signaling cascade depend on a cGMP-dependent pathway. These effects are positively regulated by CCK and negatively influenced by RC-160, interacting through CCKA and sst5 receptors, respectively. These studies provide a characterization of the antiproliferative signal mediated by sst5 receptor.
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PMID:Characterization of the antiproliferative signal mediated by the somatostatin receptor subtype sst5. 925 84

It was recently found that cholecystokinin (CCK) activates mitogen-activated protein kinases (MAPK) in isolated rat pancreatic acini. The present study evaluates whether one or both types of CCK receptors are capable of MAPK activation in pancreatic AR42J acinar cells as well as CHO cells transfected with CCK-A or CCK-B receptors. CCK significantly increased p44 MAPK and p42 MAPK activities in AR42J cells. Minimal, half-maximal, and maximal responses were observed at 30 and 500 pM and 10 nM, respectively, after CCK-8 stimulation and at 100 pM and 1.5 and 30 nM, respectively, after gastrin stimulation. Glycine-extended gastrin had no effect at 100 nM and a small but significant effect at 1 microM. The CCK-B receptor antagonist L365,260 almost totally blocked MAPK activation in AR42J cells after stimulation with gastrin and glycine-extended gastrin and substantially reduced the activation of both kinases by CCK-8, while the CCK-A receptor antagonist L364,718 was much less effective. The CCK-A-selective agonist A71376, however, was an effective stimulant of MAPK activity. In an alternative approach, stably transfected CHO cells bearing either CCK-A or CCK-B receptors were stimulated with CCK-8. Each receptor induced a time-dependent increase in activity of both MAPKs by five- to sixfold in CCK-A- and CCK-B-bearing cells. In conclusion, both CCK-A and CCK-B receptors activate MAPK in AR42J cells and in transfected CHO cells.
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PMID:Stimulation of both CCK-A and CCK-B receptors activates MAP kinases in AR42J and receptor-transfected CHO cells. 932 63

Bombesin has been reported to stimulate cholecystokinin (CCK) secretion from rat duodeno-jejunal I-cells. Bombesin was shown to activate mitogen-activated protein kinases (MAPKs) in cell types such as Swiss 3T3 fibroblasts and rat pancreatic acinar cells. No information is available on whether MAPK is activated in intestinal endocrine cells upon bombesin stimulation. This was studied by using the CCK-producing enteroendocrine cell line STC-1. Bombesin stimulated markedly and transiently both p42(MAPK) and p44(MAPK), with a maximum at 2 min, and a decrease to basal levels within 10 min. As expected, bombesin stimulated MAPK kinase 1 (MEK-1) activity. Activation of protein kinase C (PKC) with PMA also stimulated p42(MAPK), p44(MAPK) and MEK-1. Treatment of cells with PD 098059 (at 10 microM or 30 microM), which selectively inhibits MEK phosphorylation, blocked bombesin-induced p42(MAPK) and p44(MAPK) activation for at least 90 min. However, PD 098059 inhibited bombesin- and PMA-stimulated CCK secretion during the first 15 min, but failed to significantly reduce CCK release at later times. Inhibition of PKC with staurosporine, or PKC down-regulation by prolonged treatment with PMA, both drastically decreased MEK-1, p42(MAPK) and p44(MAPK) activation upon bombesin stimulation. Additionally, PKC activation appeared to be required for both MAPK-dependent (early) and -independent (late) CCK responses to bombesin. It is concluded that the early CCK secretory response of STC-1 cells to bombesin involves MAPK pathway activation through a PKC-dependent mechanism, whereas the late phase of bombesin-induced CCK secretion, that also requires PKC, appears to result from a MAPK-independent process.
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PMID:Bombesin stimulates cholecystokinin secretion through mitogen-activated protein-kinase-dependent and -independent mechanisms in the enteroendocrine STC-1 cell line. 951 70

Cholecystokinin (CCK) and other pancreatic secretagogues have recently been shown to activate signaling kinase cascades in pancreatic acinar cells, leading to the activation of extracellular signal-regulated kinases and Jun N-terminal kinases. We now show the presence of a third kinase cascade activating p38 mitogen-activated protein (MAP) kinase in isolated rat pancreatic acini. CCK and osmotic stress induced by sorbitol activated p38 MAP kinase within minutes; their effects were dose-dependent, with maximal activation of 2.8- and 4.4-fold, respectively. The effects of carbachol and bombesin on p38 MAP kinase activity were similar to those of CCK, whereas phorbol ester, epidermal growth factor, and vasoactive intestinal polypeptide stimulated p38 MAP kinase by 2-fold or less. Both CCK and sorbitol also increased the tyrosyl phosphorylation of p38 MAP kinase. Using the specific inhibitor of p38 MAP kinase, SB 203580, we found that p38 MAP kinase activity was required for MAP kinase-activated protein kinase-2 activation in pancreatic acini. SB 203580 reduced the level of basal phosphorylation and blocked the increased phosphorylation of Hsp 27 after stimulation with either CCK or sorbitol. CCK treatment induced an initial rapid decrease in total F-actin content of acini, followed by an increase after 40 min. Preincubation with SB 203580 significantly inhibited these changes in F-actin content. Staining of the actin cytoskeleton with rhodamine-conjugated phalloidin and analysis by confocal fluorescence microscopy showed disruption of the actin cytoskeleton after 10 and 40 min of CCK stimulation. Pretreatment with SB 203580 reduced these changes. These findings demonstrate that the activation of p38 MAP kinase is involved not only in response to stress, but also in physiological signaling by gastrointestinal hormones such as CCK, where activation of Gq-coupled receptors stimulates a cascade in which p38 MAP kinase activates MAP kinase-activated protein kinase-2, resulting in Hsp 27 phosphorylation. Activation of p38 MAP kinase, most likely through phosphorylation of Hsp 27, plays a role in the organization of the actin cytoskeleton in pancreatic acini.
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PMID:A role for the p38 mitogen-activated protein kinase/Hsp 27 pathway in cholecystokinin-induced changes in the actin cytoskeleton in rat pancreatic acini. 972 40

We investigated how heat shock protein 27 (HSP27) and its phosphorylation are involved in the action of cholecystokinin (CCK) on the actin cytoskeleton by genetic manipulation of Chinese hamster ovary (CHO) cells stably transfected with the CCK-A receptor. In these cells, as in rat acini, CCK activated p38 mitogen-activated protein (MAP) kinase and increased the phosphorylation of HSP27. This effect could be blocked with the p38 MAP kinase inhibitor SB-203580. Examination by confocal microscopy of cells stained with rhodamine phalloidin showed that CCK dose-dependently induced changes of the actin cytoskeleton, including cell shape changes, which were coincident with actin cytoskeleton fragmentation and formation of actin filament patches in the cells. To further evaluate the role of HSP27, CHO-CCK-A cells were transfected with expression vectors for either wild-type (wt) or mutant (3A, 3G, and 3D) human HSP27. Overexpression of wt-HSP27 and 3D-HSP27 inhibited the effects on the actin cytoskeleton seen after high-dose CCK stimulation. In contrast, overexpression of nonphosphorylatable mutants, 3A- and 3G-HSP27, or inhibition of phosphorylation of HSP27 by preincubation of wt-HSP27 transfected cells with SB-203580 did not protect the actin cytoskeleton. These results suggest that phosphorylation of HSP27 is required to stabilize the actin cytoskeleton and to protect the cells from the effects of high concentrations of CCK.
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PMID:HSP27 expression regulates CCK-induced changes of the actin cytoskeleton in CHO-CCK-A cells. 1060 Jul 53

The pancreatic gland has an enormous potential for growth and regeneration, mainly in rodents. These processes remain mostly under the control of the GI hormone cholecystokinin (CCK). The human pancreas however does not show proliferative properties after partial pancreatectomy, but research in this field has been scarce. Recent studies indicate that CCK might not be the expected trophic agent since its two receptors CCK(A) and CCK(B) were not found on human exocrine pancreas. Therefore, if human pancreas grows and regenerates, it has to be under the influence of some unknown trophic factors. Neuropeptides receiving much attention lately as regulators of pancreatic functions could be among the searched trophic agents. This presentation focus on neuropeptides growth potential: GRP-Bombesin, GABA, PP, PYY, Neurotensin, SP, VIP, PACAP, CGRP and galanin. Some neuropeptides have moderate effects on pancreatic enzymes and electrolytes secretion: SP, VIP, PACAP. However, their trophic effects remain unexplored except for GRP-bombesin and PACAP. PACAP preferentially exhibits its mitogenic and proliferative effects on the pancreatic acinar cells AR4-2J via tyrosine kinase, phospholipase D and ornithine decarboxylase activation but not through adenylate cyclase. The growth promoting action of GRP-bombesin is well documented on rodent's pancreas. However, recent studies indicate that this neuropeptide is potentially trophic for larger mammals' pancreas. Indeed, investigators recently documented that bombesin induced pancreatic regeneration in the pig after partial pancreatectomy through mitogen-activated protein kinases activation as do CCK-8 and caerulein on rat pancreas. Have we found the magic pancreatic trophic factor in large mammals? Further investigations will tell.
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PMID:Intervention of GI neuropeptides in pancreatic growth and regeneration: comparison with cholecystokinin. 1507 55


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