Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.24 (mitogen-activated protein kinase)
 95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of c-Jun in apoptosis evoked by human amylin was investigated using human and rat insulinoma beta-cell lines. Two transient increases in the levels of c-jun mRNA were detected at 30 minutes and eight hours after treatment with human amylin. The level of c-Jun protein was also up-regulated in a time-dependent manner, reaching maximal levels after eight hours of exposure. However, no c-Jun induction was detected in cells treated with vehicle only or with rat amylin, indicating that the amyloidogenic feature of the human peptide may be important for c-Jun induction. We found that c-Jun was activated by phosphorylation specifically at Ser63 at four hours, but not at Ser73, after treatment with human amylin, preceding increased c-Jun protein. Furthermore, expression of an antisense c-jun (AS-c-jun), which suppressed protein levels of both c-Jun and phosphorylated-c-Jun, caused a marked reduction in apoptotic cell death, whereas the corresponding sense c-jun (S-c-jun) had no effect on changes of either c-Jun production or apoptosis. This indicated that increased expression and activation of c-Jun is required for human amylin-induced apoptosis. Immunocytochemical studies showed a significant increase in nuclear staining for c-Jun, phosphorylated-c-Jun (Ser63) and phosphorylated-JNK, suggesting that c-Jun may be activated through activation of JNK. In addition, electrophoretic mobility-shift assays showed that the increase in expression and phosphorylation of c-Jun was associated with increased AP-1 DNA binding activity. Supershift assays demonstrated that c-Jun, c-Fos and ATF-2 are part of the AP-1 complex, indicating that activated c-Jun is dimerized with c-Fos or ATF-2 for control of its target gene expression. Finally, we showed that human amylin triggers AP-1-mediated transcriptional activation. Our results suggest strongly that human amylin induces apoptosis through stimulation of expression and activation of c-Jun, and that co-expression and dimerization of c-Jun and c-fos or ATF-2 may be important for activation of the downstream apoptotic process.
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PMID:Increased expression and activation of c-Jun contributes to human amylin-induced apoptosis in pancreatic islet beta-cells. 1244 Nov 6

The activation of the glucagon-like peptide-1 (GLP-1) receptor has been shown to have an important role in the functional activity of islet beta-cells and in the expansion of the islet cell mass. Constant remodeling of islet cell mass is mediated in vivo by proliferative and apoptotic stimuli to ensure a dynamic response to a changing demand for insulin. The present study was undertaken to investigate the biological activity of GLP-1 when cells were challenged by a proapoptotic stimulus. We have shown that activation of the GLP-1 receptor inhibits H(2)O(2)-induced apoptosis in a cultured mouse insulinoma cell line, termed MIN6. GLP-1 reduced DNA fragmentation and improved cell survival. This was mediated by an increased expression of the antiapoptotic proteins Bcl-2 and Bcl-xL. GLP-1 also prevented the H(2)O(2)-dependent cleavage of poly-(ADP-ribose)-polymerase. Inhibition of the GLP-1-dependent increase of cAMP by Rp-cAMP blocked the antiapoptotic action of GLP-1, as determined by DNA fragmentation and poly-(ADP-ribose)-polymerase assays and by detection of Bcl-2 and Bcl-xL protein levels. Investigation of the role of the protein kinases, PI-3 kinase (PI3K) and MAPK, by use of the inhibitors PD098059 and LY294002 demonstrated that the activation of PI3K, but not MAPK, was required to prevent proapoptotic events in cells exposed to H(2)O(2). The present study provides evidence that GLP-1 has an antiapoptotic action mediated by a cAMP- and PI3K-dependent signaling pathway.
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PMID:Glucagon-like peptide-1 inhibits apoptosis of insulin-secreting cells via a cyclic 5'-adenosine monophosphate-dependent protein kinase A- and a phosphatidylinositol 3-kinase-dependent pathway. 1263 28

The stress-activated protein kinase c-Jun NH2-terminal kinase (JNK) is a central signal for interleukin-1beta (IL-1beta)-induced apoptosis in insulin-producing beta-cells. The cell-permeable peptide inhibitor of JNK (JNKI1), that introduces the JNK binding domain (JBD) of the scaffold protein islet-brain 1 (IB1) inside cells, effectively prevents beta-cell death caused by this cytokine. To define the molecular targets of JNK involved in cytokine-induced beta-cell apoptosis we investigated whether JNKI1 or stable expression of JBD affected the expression of selected pro- and anti-apoptotic genes induced in rat (RIN-5AH-T2B) and mouse (betaTC3) insulinoma cells exposed to IL-1beta. Inhibition of JNK significantly reduced phosphorylation of the specific JNK substrate c-Jun (p<0.05), IL-1beta-induced apoptosis (p<0.001), and IL-1beta-mediated c-fos gene expression. However, neither JNKI1 nor JBD did influence IL-1beta-induced NO synthesis or iNOS expression or the transcription of the genes encoding mitochondrial manganese superoxide dismutase (MnSOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase rho (GSTrho), heat shock protein (HSP) 70, IL-1beta-converting enzyme (ICE), caspase-3, apoptosis-inducing factor (AIF), Bcl-2 or Bcl-xL. We suggest that the anti-apoptotic effect of JNK inhibition by JBD is independent of the transcription of major pro- and anti-apoptotic genes, but may be exerted at the translational or posttranslational level.
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PMID:The JNK binding domain of islet-brain 1 inhibits IL-1 induced JNK activity and apoptosis but not the transcription of key proapoptotic or protective genes in insulin-secreting cell lines. 1456 87

Therapeutic options to inhibit the growth and spread of neuroendocrine (NE) gastrointestinal tumours are still limited. Since gefitinib (4-(3-chloro-4-fluoroanilino)-7-methoxy-6-(3-morpholinopropoxy)quinazoline), an inhibitor of epidermal growth factor receptor-sensitive tyrosine kinase (EGFR-TK), had been shown to suppress potently the growth of various non-NE tumour entities, we studied the antineoplastic potency of gefitinib in NE gastrointestinal tumour cells. In human insulinoma (CM) cells, in human pancreatic carcinoid (BON) cells and in NE tumour cells of the gut (STC-1), gefitinib induced a time- and dose-dependent growth inhibition by almost 100%. The antiproliferative potency of gefitinib correlated with the proliferation rate of the tumour cells. So the IC(50) value of gefitinib was 4.7+/-0.6 microM in the fast-growing CM cells, still 16.8+/-0.4 microM in the moderate-growing BON cells, and up to 31.5+/-2.5 microM in the slow-growing STC-1 cells. Similarly, the induction of apoptosis and cell-cycle arrest by gefitinib differed according to growth characteristics: fast-growing CM cells displayed a strong G0/G1 arrest in response to gefitinib, while no significant cell-cycle alterations were seen in the slow-growing STC-1. Vice versa, the proapoptotic effects of gefitinib, as determined by caspase-3 activation and DNA fragmentation, were most pronounced in the slow-growing STC-1 cells. Using cDNA microarrays, we found extensive changes in the expression of genes involved in the regulation of apoptosis and cell cycle after incubation with gefitinib. Among them, an upregulation of the growth arrest and DNA damage-inducible gene GADD153 was observed. Phosphorylation of ERK1/2, which inhibits GADD153 expression, was reduced in a time-dependent manner. However, no gefitinib-induced activation of the GADD153-inducing p38 mitogen-activated protein kinase was detected. Our data demonstrate that the inhibition of EGFR-TK by gefitinib induces growth inhibition, apoptosis and cell-cycle arrest in NE gastrointestinal tumour cells. Thus, EGFR-TK inhibition appears to be a promising novel approach for the treatment of NE tumour disease.
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PMID:A novel approach in the treatment of neuroendocrine gastrointestinal tumours. Targeting the epidermal growth factor receptor by gefitinib (ZD1839). 1458 82

Oligonucleotide microarrays were used to define oleic acid (OA)-regulated gene expression and proteomic technology to screen protein kinases in MIN6 insulinoma cells. The effects of oxidative stress caused by OA and potential protective effects of N-acetyl-L-cysteine (NAC), a scavenger of reactive oxygen species (ROS), on global gene expression and beta-cell function were investigated. Long-term exposure of MIN6 cells to OA led to a threefold increase in basal insulin secretion, a 50% decrease in insulin content, an inhibition of glucose-stimulated insulin secretion (GSIS), and a twofold increase in the level of ROS. The addition of NAC normalized both the OA-induced insulin content and ROS elevation, but it failed to restore GSIS. Microarray studies and subsequent quantitative PCR analysis showed that OA consistently regulated the expression of 45 genes involved in metabolism, cell growth, signal transduction, transcription, and protein processing. The addition of NAC largely normalized the expression of the OA-regulated genes involved in cell growth and differentiation but not other functions. A protein kinase screen showed that OA regulated the expression and/or phosphorylation levels of kinases involved in stress-response mitogen-activated protein kinase, phosphatidylinositol 3-kinase, and cell cycle control pathways. Importantly, these findings indicate that chronic OA exposure can impair beta-cell function through ROS-dependent and -independent mechanisms.
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PMID:Gene and protein kinase expression profiling of reactive oxygen species-associated lipotoxicity in the pancreatic beta-cell line MIN6. 1469 7

Glucagon-like peptide 1 (GLP-1), a gut incretin hormone that stimulates insulin secretion, also activates antiapoptotic signaling pathways such as phosphoinositide 3-kinase and mitogen-activated protein kinase in pancreatic and insulinoma cells. Since these kinases have been shown to protect against myocardial injury, we hypothesized that GLP-1 could directly protect the heart against such injury via these prosurvival signaling pathways. Both isolated perfused rat heart and whole animal models of ischemia/reperfusion were used, with infarct size measured as the end point of injury. In both studies, GLP-1 added before ischemia demonstrated a significant reduction in infarction compared with the valine pyrrolidide (an inhibitor of its breakdown) or saline groups. This protection was abolished in the in vitro hearts by the GLP-1 receptor antagonist exendin (9-39), the cAMP inhibitor Rp-cAMP, the PI3kinase inhibitor LY294002, and the p42/44 mitogen-activated protein kinase inhibitor UO126. Western blot analysis demonstrated the phosphorylation of the proapoptotic peptide BAD in the GLP-1-treated groups. We show for the first time that GLP-1 protects against myocardial infarction in the isolated and intact rat heart. This protection appears to involve activating multiple prosurvival kinases. This finding may represent a new therapeutic potential for this class of drug currently undergoing clinical trials in the treatment of type 2 diabetes.
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PMID:Glucagon-like peptide 1 can directly protect the heart against ischemia/reperfusion injury. 1561 22

The leptin receptor (LEPR) is a class I cytokine receptor signalling via both the janus kinase/signal transducer and activator of transcription (JAK/STAT) and the MAP kinase pathways. In addition, leptin has been shown previously to activate AMP-activated kinase (AMPK) in skeletal muscle. To enable a detailed analysis of leptin signalling in pancreatic beta cells, LEPR point mutants with single or combined exchanges of the three intracellular tyrosines were expressed in HIT-T15 insulinoma cells. Western blots with activation state-specific antibodies recognizing specific signalling molecules revealed that the wild-type receptor activated STAT1, STAT3, STAT5 and ERK1/2 but failed to alter the phosphorylation of AMPK. Each of the three intracellular tyrosine residues in LEPR exhibited different signalling capacities: Tyr985 was necessary and sufficient for leptin-induced activation of ERK1/2; Tyr1077 induced tyrosyl phosphorylation of STAT5; and Tyr1138 was capable of activating STAT1, STAT3 and STAT5. Consistent results were obtained in reporter gene assays with STAT3 or STAT5-responsive promoter constructs, respectively. Furthermore, the sequence motifs surrounding the three tyrosine residues are conserved in LEPR from mammals, birds and in a LEPR-like cytokine receptor from pufferfish. Mutational analysis of the box3 motif around Tyr1138 identified Met1139 and Gln1141 as important determinants that define specificity towards the different STAT factors. These data indicate that all three conserved tyrosines are involved in LEPR function and define the pleiotropy of signal transduction via STAT1/3, STAT5 or ERK kinases. Activation and inhibition of AMPK appears to require additional components of the signalling pathways that are not present in beta cells.
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PMID:Pleiotropy of leptin receptor signalling is defined by distinct roles of the intracellular tyrosines. 1563 36

NeuroD/BETA2 (referred to as NeuroD hereafter) is a basic helix-loop-helix (bHLH) transcription factor that is required for the development and survival of a subset of neurons and pancreatic endocrine cells in mice. Gain-of-function analyses demonstrated that NeuroD can (i) convert epidermal fate into neuronal fate when overexpressed in Xenopus embryos, and (ii) activate the insulin promoter in pancreatic beta cell lines in response to glucose stimulation. In glucose-stimulated INS-1 pancreatic beta cells, mutations of S259, S266, and S274 to alanines inhibited the ability of NeuroD to activate the insulin promoter. Phosphorylation of those serine residues by ERK1/2 was required for NeuroD activity in that assay. To determine whether the same residues are implicated in the neurogenic activity of NeuroD, we mutated the conserved S259, S266, and S274 of Xenopus NeuroD to alanines (S259A, S266A, and S274A), and performed an ectopic neurogenesis assay in Xenopus embryos. In contrast to what has been observed in the pancreatic beta cell line, the S266A and S274A mutant forms of Xenopus NeuroD displayed significantly increased abilities to form ectopic neurons, while S259A had little effect. In addition, S266A and S274A of Xenopus NeuroD resulted in increased accumulation of protein in the injected embryos while the corresponding mutations on mouse NeuroD did not have the same effect in an insulinoma cell line. Our results demonstrate that the consequence of NeuroD protein modification is context-dependent at both the molecular and functional levels.
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PMID:Context-dependent regulation of NeuroD activity and protein accumulation. 1579 19

The influence of the proinflammatory cytokine interleukin (IL)-17 on inducible nitric oxide (NO) synthase (iNOS)-mediated NO release was investigated in the mouse insulinoma cell line MIN6 and mouse pancreatic islets. IL-17 markedly augmented iNOS mRNA/protein expression and subsequent NO production induced in MIN6 cells or pancreatic islets by different combinations of interferon-gamma, tumor necrosis factor-alpha, and IL-1beta. The induction of iNOS by IL-17 was preceded by phosphorylation of p38 mitogen-activated protein kinase (MAPK), and inhibition of p38 MAPK activation completely abolished IL-17-stimulated NO release. IL-17 enhanced the NO-dependent toxicity of proinflammatory cytokines toward MIN6 cells, while IL-17-specific neutralizing antibody partially reduced the NO production and rescued insulinoma cells and pancreatic islets from NO-dependent damage induced by activated T cells. Finally, a significant increase in blood IL-17 levels was observed in a multiple low-dose streptozotocin model of diabetes, suggesting that T cell-derived IL-17 might be involved in NO-dependent damage of beta cells in this disease.
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PMID:Interleukin-17 stimulates inducible nitric oxide synthase-dependent toxicity in mouse beta cells. 1626 Dec 64

Understanding mechanisms underlying apoptotic destruction of insulin-secreting cells is critical to validate therapeutic targets for type 1 diabetes mellitus. We recently reported insulin-like growth factor binding protein-3 (IGFBP-3) as a novel mediator of apoptosis in insulin-secreting cells. In light of emerging IGF-independent roles for IGFBP-3, we investigated the mechanisms underlying actions of the novel, recombinant human mutant G(56)G(80)G(81)-IGFBP-3, which lacks intrinsic IGF binding affinity. Using the rat insulinoma RINm5F cell line, we report the first studies in insulin-secreting cells that IGFBP-3 selectively suppresses multiple, key intracellular phosphorelays. By immunoblot, we demonstrate that G(56)G(80)G(81)-IGFBP-3 suppresses phosphorylation of c-raf-MEK-ERK pathway and p38 kinase in time-dependent and dose-dependent manners. SAPK/JNK signaling was unaffected. These data delineate several novel intracellular sites of action for IGFBP-3 in insulin-secreting cells.
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PMID:Novel actions of IGFBP-3 on intracellular signaling pathways of insulin-secreting cells. 1627 48


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