Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.12.2 (MEK)
18,161 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

OSU03012, a Celecoxib derivative, has been shown to inhibit proliferation and induce apoptosis in human cancer cell lines. However, its underlying mechanisms are not completely understood. In our study, the relationship between cell cycle inhibition and apoptosis induced by OSU03012 was investigated in human oral cancer cell lines. In the premalignant and malignant cell lines, OSU03012-induced growth inhibition, S-phase arrest, and apoptosis were accompanied by a marked increase in the activity of Erk1/2 and Cdk2/cyclin A. Inhibition of Cdks by roscovitine partially blocked OSU03012-induced growth inhibition and apoptosis. Although the activity of cdc2/cyclin B was reduced, expression of constructively active cdc2AF did not reverse OSU03012-induced S-phase arrest. When Erk1/2 was inhibited by U0126 before addition of OSU03012, growth inhibition and apoptosis induced by OSU03012 were attenuated. The levels of the Cdk2/cyclin A were reduced and cells accumulated in the G(0)/G(1) phase. When cells were allowed to accumulate in S-phase before addition of U0126, apoptosis also was attenuated suggesting that Erk1/2 is required for both progression of cells into the S-phase and apoptosis. Expression of constructively active MEK enhanced OSU03012-induced apoptosis. OSU03012 selectively inhibited the proliferation in premalignant and malignant, but not normal human oral cell lines. In conclusion, we show that OSU03012 has potent anti-proliferative and apoptotic activity against premalignant and malignant human oral cells through activation of Erk1/2, and Cdks. OSU0312 may provide unique opportunities for cancer prevention and sensitization of cancer cells to S-phase modalities.
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PMID:OSU03012 activates Erk1/2 and Cdks leading to the accumulation of cells in the S-phase and apoptosis. 1879 57

This study examined how L-leucine affected DNA synthesis and cell cycle regulatory protein expression in cultured primary chicken hepatocytes. L-Leucine promoted DNA synthesis in a dose- and time-dependent manner, with concomitant increases in cyclin D1 and cyclin E expression. Phospholipase C (PLC) and protein kinase C (PKC) mediated the L-leucine-induced increases in [3H]-thymidine incorporation and cyclin D1/CDK4 and cyclin E/CDK2 expression, as U73122 (a PLC inhibitor) or bisindolylmaleimide I (a PKC blocker) inhibited these effects. L-Leucine also increased PKC phosphorylation and intracellular Ca2+ levels. L-Leucine-mediated increases in [3H]-thymidine incorporation and cyclin/CDK expression were sensitive to LY 294002 (PI3K inhibitor), Akt inhibitor, PD 98059 (MEK inhibitor). It was also observed that L-leucine-induced increases of cyclin/CDK expression were inhibited by PI3K siRNA and ERK siRNA; L-leucine increased extracellular signal-regulated kinases 1/2 (ERK1/2) and Akt phosphorylation levels. Bisindolylmaleimide I attenuated L-leucine-induced phosphorylation of ERK1/2 but did not influence Akt phosphorylation, and PI3K siRNA and LY 294002 inhibited L-leucine-induced ERK1/2 phosphorylation, suggesting some cross-talk between the PKC and ERK1/2 or PI3K/Akt and ERK1/2 pathways. L-Leucine also increased the levels of phosphorylated molecular target of rapamycin (mTOR) and two of its targets, ribosomal protein S6 kinase (p70S6K), and 4E binding protein 1 (4E-BP1); furthermore, rapamycin (an mTOR inhibitor) blocked all of the mitogenic effects of L-leucine. In addition, Akt inhibitor blocked L-leucine-induced mTOR phosphorylation. In conclusion, L-leucine stimulated DNA synthesis and promoted cell cycle progression in primary cultured chicken hepatocytes through PKC, ERK1/2, PI3K/Akt, and mTOR.
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PMID:L-leucine increases [3H]-thymidine incorporation in chicken hepatocytes: involvement of the PKC, PI3K/Akt, ERK1/2, and mTOR signaling pathways. 1898 Feb 46

Activation of the double-stranded RNA-dependent protein kinase (PKR) has been implicated in the pathogenesis of several neurodegenerative diseases. We find that a compound widely used as a pharmacological inhibitor of this enzyme, referred to as PKR inhibitor (PKRi), {8-(imidazol-4-ylmethylene)-6H-azolidino[5,4-g]benzothiazol-7-one}, protects against the death of cultured cerebellar granule and cortical neurons. PKRi also prevents striatal neurodegeneration and improves behavioral outcomes in a chemically induced mouse model of Huntington's disease. Surprisingly, PKRi fails to block the phosphorylation of eIF2alpha, a downstream target of PKR, and does not reduce the autophosphorylation of PKR enzyme immunoprecipitated from neurons. Furthermore, neurons lacking PKR are fully protected from apoptosis by PKRi, demonstrating that neuroprotection by this compound is not mediated by PKR inhibition. Using in vitro kinase assays we investigated whether PKRi affects any other protein kinase. These analyses demonstrated that PKRi has no major inhibitory effect on pro-apoptotic kinases such as the c-Jun N-terminal kinases, the p38 MAP kinases and the death-associated protein kinases, or on other kinases including c-Raf, MEK1, MKK6 and MKK7. PKRi does, however, inhibit the activity of certain cyclin-dependent kinases (CDKs), including CDK1, CDK2 and CDK5 both in vitro and in low potassium-treated neurons. Consistent with its inhibitory action on mitotic CDKs, the treatment of HT-22 and HEK293T cell lines with PKRi sharply reduces the rate of cell cycle progression. Taken together with the established role of CDK activation in the promotion of neurodegeneration, our results suggest that PKRi exerts its neuroprotective action by inhibiting CDK.
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PMID:A chemical compound commonly used to inhibit PKR, {8-(imidazol-4-ylmethylene)-6H-azolidino[5,4-g] benzothiazol-7-one}, protects neurons by inhibiting cyclin-dependent kinase. 1904 82

We have shown that heightened AKT activity sensitized multiple myeloma cells to the antitumor effects of the mammalian target of rapamycin inhibitor CCI-779. To test the mechanism of the AKT regulatory role, we stably transfected U266 multiple myeloma cell lines with an activated AKT allele or empty vector. The AKT-transfected cells were more sensitive to cytostasis induced in vitro by rapamycin or in vivo by its analogue, CCI-779, whereas cells with quiescent AKT were resistant. The ability of mammalian target of rapamycin inhibitors to down-regulate D-cyclin expression was significantly greater in AKT-transfected multiple myeloma cells due, in part, to the ability of AKT to curtail cap-independent translation and internal ribosome entry site (IRES) activity of D-cyclin transcripts. Similar AKT-dependent regulation of rapamycin responsiveness was shown in a second myeloma model: the PTEN-null OPM-2 cell line transfected with wild-type PTEN. Because extracellular signal-regulated kinase (ERK)/p38 activity facilitates IRES-mediated translation of some transcripts, we investigated ERK/p38 as regulators of AKT-dependent effects on rapamycin sensitivity. AKT-transfected U266 cells showed significantly decreased ERK and p38 activity. However, only an ERK inhibitor prevented D-cyclin IRES activity in resistant "low-AKT" myeloma cells. Furthermore, the ERK inhibitor successfully sensitized myeloma cells to rapamycin in terms of down-regulated D-cyclin protein expression and G1 arrest. However, ectopic overexpression of an activated MEK gene did not increase cap-independent translation of D-cyclin in "high-AKT" myeloma cells, indicating that mitogen-activated protein kinase/ERK kinase/ERK activity was required, but not sufficient, for activation of the IRES. These data support a scenario where heightened AKT activity down-regulates D-cyclin IRES function in multiple myeloma cells and ERK facilitates activity.
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PMID:Regulation of D-cyclin translation inhibition in myeloma cells treated with mammalian target of rapamycin inhibitors: rationale for combined treatment with extracellular signal-regulated kinase inhibitors and rapamycin. 1913 16

Cyclin I is an atypical cyclin because it is most abundant in postmitotic cells. We previously showed that cyclin I does not regulate proliferation, but rather controls survival of podocytes, terminally differentiated epithelial cells that are essential for the structural and functional integrity of kidney glomeruli. Here, we investigated the mechanism by which cyclin I safeguards against apoptosis and found that cyclin I bound and activated cyclin-dependent kinase 5 (Cdk5) in isolated mouse podocytes and neurons. Cdk5 activity was reduced in glomeruli and brain lysates from cyclin I-deficient mice, and inhibition of Cdk5 increased in vitro the susceptibility to apoptosis in response to cellular damage. In addition, levels of the prosurvival proteins Bcl-2 and Bcl-XL were reduced in podocytes and neurons from cyclin I-deficient mice, and restoration of Bcl-2 or Bcl-XL expression prevented injury-induced apoptosis. Furthermore, we found that levels of phosphorylated MEK1/2 and ERK1/2 were decreased in cyclin I-deficient podocytes and that inhibition of MEK1/2 restored Bcl2 and Bcl-XL protein levels. Of interest, this pathway was also defective in mice with experimental glomerulonephritis. Taken together, these data suggest that a cyclin I-Cdk5 complex forms a critical antiapoptotic factor in terminally differentiated cells that functions via MAPK signaling to modulate levels of the prosurvival proteins Bcl-2 and Bcl-XL.
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PMID:Cyclin I activates Cdk5 and regulates expression of Bcl-2 and Bcl-XL in postmitotic mouse cells. 1972 34

Neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and Huntington's disease and conditions such as ischemic stroke affect millions of individuals annually and exert an enormous financial burden on society. A hallmark of these conditions is the abnormal loss of neurons. Currently, there are no effective strategies to prevent neuronal death in these pathologies. We report that several 2-arylidine and 2-hetarylidin derivatives of the 1,4-benzoxazines class of compounds are highly protective in tissue culture models of neurodegeneration. Results obtained using pharmcalogical inhibitors indicate that neuroprotection by these compounds does not involve the Raf-MEK-ERK or PI-3 kinase-Akt signaling pathways nor other survival-promoting molecules such as protein kinase A (PKA), calcium calmodulin kinase A (CaMK), and histone deacetylases (HDACs). We tested one of these compounds, (Z)-6-amino-2-(3',5'-dibromo-4'-hydroxybenzylidene)-2H-benzo[b][1,4]oxazin-3(4H)-one, designated as HSB-13, in the 3-nitropropionic acid (3-NP)-induced mouse model of Huntington's disease. HSB-13 reduced striatal degeneration and improved behavioral performance in mice administered with 3-NP. Furthermore, HSB-13 was protective in a Drosophila model of amyloid precursor protein (APP) toxicity. To understand how HSB-13 and other 1,4-benzoxazines protect neurons, we performed kinase profiling analyses. These analyses showed that HSB-13 inhibits GSK3, p38 MAPK, and cyclin-dependent kinases (CDKs). In comparison, another compound, called ASK-2a, that protects cerebellar granule neurons against low-potassium-induced death inhibits GSK3 and p38 MAPK but not CDKs. Despite its structural similarity to HSB-13, however, ASK-2a is incapable of protecting cortical neurons and HT22 cells against homocysteic acid (HCA)-induced or Abeta toxicity, suggesting that protection against HCA and Abeta depends on CDK inhibition. Compounds described in this study represent a novel therapeutic tool in the treatment of neurodegenerative diseases.
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PMID:Identification of novel 1,4-benzoxazine compounds that are protective in tissue culture and in vivo models of neurodegeneration. 2014 21

Hepatocellular carcinoma (HCC) is the sixth most common malignancy and the third leading cause of cancer deaths worldwide. Proper classification and early identification of HCC and precursor lesions is essential to the successful treatment and survival of HCC patients. Recent molecular genetic, pathologic, and clinical data have led to the stratification of hepatic adenomas into three subgroups: those with mutant TCF1/HNF1 alpha gene, those with mutant beta-catenin, and those without mutations in either of these loci. Hepatic adenomas with alpha-catenin mutations have a significantly greater risk for malignant transformation in comparison with the other two subgroups. Telangiectatic focal nodular hyperplasia has now been reclassified as telangiectatic adenoma due to the presence of non-random methylation patterns, consistent with the monoclonal origin which is similar to hepatic adenoma and HCC. HCC precursor lesions demonstrate unique molecular alterations of HSP70, CAP2, glypican 3, and glutamine synthetase that have proven useful in the histologic diagnosis of early HCC. Though specific genetic alterations depend on HCC etiology, the main proteins affected include cell membrane receptors (in particular tyrosine kinase receptors) as well as proteins involved in cell signaling (specifically Wnt/beta-catenin, Ras/Raf/MEK/ERK and PI3K/Akt/mTOR pathways), cell cycle regulation (i.e. p53, p16/INK4, cyclin/cdk complex), invasiveness (EMT, TGF-beta) and DNA metabolism. Advances in gene expression profiling have provided new insights into the molecular genetics of HCC. HCCs can now be stratified into two clinically relevant groups: Class A, the low survival subclass (overall survival time 30.3+/- 8.02 months), shows strong expression signatures of cell proliferation and antiapoptosis genes (such as PNCA and cell cycle regulators CDK4, CCNB1, CCNA2, and CKS2) as well as genes involving ubiquitination and sumoylation; Class B, the high survival subclass (overall survival time 83.7 +/-10.3 months), does not have the above expression signature. In fact, insights into HCC-specific alterations of signal transduction pathways and protein expression patterns have led to the development of new therapeutic agents with molecular targets such as EGFR, VEGF, or other multi-kinase inhibitors. In the future, these specific molecular alterations in HCC can potentially serve as diagnostic tools, prognostic markers, and/or therapeutic targets with the potential to alter clinical outcomes.
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PMID:Molecular genetics of hepatocellular neoplasia. 2018 87

G-protein-coupled receptor-30 (GPR30) shows estrogen-binding affinity and mediates non-genomic signaling of estrogen to regulate cell growth. We here showed for the first time, in contrast to the reported promoting action of GPR30 on the growth of breast and ovarian cancer cells, that activation of GPR30 by the receptor-specific, non-estrogenic ligand G-1 inhibited the growth of androgen-dependent and androgen-independent prostate cancer (PCa) cells in vitro and PC-3 xenografts in vivo. However, G-1 elicited no growth or histological changes in the prostates of intact mice and did not inhibit growth in quiescent BPH-1, an immortalized benign prostatic epithelial cell line. Treatment of PC-3 cells with G-1 induced cell-cycle arrest at the G(2) phase and reduced the expression of G(2)-checkpoint regulators (cyclin-A2, cyclin-B1, cdc25c, and cdc2) and phosphorylation of their common transcriptional regulator NF-YA in PC-3 cells. With extensive use of siRNA-knockdown experiments and the MEK inhibitor PD98059 in this study, we dissected the mechanism underlying G-1-induced inhibition of PC-3 cell growth, which was mediated through GPR30, followed by sustained activation of Erk1/2 and a c-jun/c-fos-dependent upregulation of p21, resulting in the arrest of PC-3 growth at the G(2) phase. The discovery of this signaling pathway lays the foundation for future development of GPR30-based therapies for PCa.
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PMID:Activation of GPR30 inhibits the growth of prostate cancer cells through sustained activation of Erk1/2, c-jun/c-fos-dependent upregulation of p21, and induction of G(2) cell-cycle arrest. 2020 90

Cdk5 has long been recognized to play an important role in development, maturation and apoptosis of postmitotic and terminally differentiated cells. Activation of Cdk5 is tightly regulated by specific activators. Cyclin I was recently characterized as the first cyclin protein that binds to and activates Cdk5. Cyclin I-Cdk5 activates the MEK-ERK pathway and results in increased Bcl-2 and Bcl-X(L) mRNA and protein levels. Lack of Cyclin I renders podocytes more susceptible to apoptosis. Interestingly, activation of Cdk5 by p35 is also involved in the podocytes' response to injury. In the absence of p35, podocytes are more prone to undergo apoptosis. Here, we propose a new model where Cdk5 plays a central role in the cellular response machinery against injury-induced apoptosis of post-mitotic cells. While Cyclin I-Cdk5 regulates Bcl-2 family proteins through activation of the MEK-ERK pathway, p35-Cdk5 directly phosphorylates and stabilizes Bcl-2.
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PMID:Cyclin I-Cdk5 governs survival in post-mitotic cells. 2040 35

Esculetin, a phenolic compound, has been shown to inhibit the growth of colon tumors in animal studies. However, the roles of signaling pathways and cell cycle regulation in the esculetin-induced inhibition of cancer cell growth, remain to be elucidated. The present study suggests a novel mechanism for the Ras/ERK1/2 pathway in esculetin-treated human colon cancer HCT116 cells. The treatment of cells with esculetin resulted in significant growth inhibition and G1 phase cell cycle arrest, which led to the down-regulation of cyclin and cyclin-dependent kinase (CDK) expressions. This G1 phase cell cycle arrest was associated with the up-regulation of p27KIP expression. In addition, ERK1/2 was activated by esculetin. The pre-treatment of cells with the MEK1/2-specific inhibitor, PD98059, blocked the p27KIP expression induced by esculetin. Blockage of the ERK1/2 function consistently prevented the inhibition of cell proliferation and decreased G1 phase cell cycle protein levels. Furthermore, Ras activation was increased by the esculetin treatment. Transient transfection of the dominant negative Ras (RasN17) mutant gene abolished both the ERK1/2 activity and p27KIP expression induced by esculetin. Finally, the overexpression of RasN17 suppressed the esculetin-induced reduction in cell proliferation and cell cycle proteins. In conclusion, these results indicate that the Ras/ERK1/2 pathway is mediated by the p27KIP1 induction, leading to a reduction in cyclin/CDK complexes in the esculetin-induced inhibition of colon cancer cell growth. Overall, these findings indicate that the molecular action of esculetin has therapeutic potential for the treatment of colon malignancies.
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PMID:Esculetin inhibits cell proliferation through the Ras/ERK1/2 pathway in human colon cancer cells. 2110 80


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