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)

There are many precedents for the production from a single precursor of multiple peptides, with independent receptors and different bioactivities. Gastrin-releasing peptide (GRP) is initially synthesized as amino acids 1-27 of a 125-residue precursor, proGRP, and is subsequently cleaved and amidated to form GRP18-27. We investigated the hypothesis that C-terminal proGRP peptides are also biologically active. Human proGRP18-125 was expressed in Escherichia coli as a glutathione S-transferase fusion protein. Recombinant proGRP18-125 stimulated proliferation and migration of the human colorectal carcinoma cell line DLD-1. The observations that an antagonist selective for the GRP receptor did not inhibit activity in either proliferation or migration assays and that the recombinant peptide did not bind to either the GRP receptor or orphan receptor BRS-3 indicated that neither activity was mediated by the known GRP receptors. Recombinant human proGRP31-125 and proGRP42-98 were also prepared and shown to stimulate proliferation of DLD-1 cells and the human prostate carcinoma cell line DU145. The synthetic peptides proGRP47-68 and [Tyr79]proGRP80-97 stimulated inositol phosphate production, MAPK kinase activity, and proliferation and migration of DLD-1 cells. Binding sites for both radioiodinated synthetic peptides were demonstrated on DLD-1 cells. Each peptide was able to compete with the other for binding, and a GRP receptor antagonist did not inhibit binding of either peptide. We conclude that peptides derived from the C terminus of proGRP are biologically active and that their activity is mediated by a receptor distinct from the two known GRP receptors.
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PMID:C-terminal fragments of the gastrin-releasing peptide precursor stimulate cell proliferation via a novel receptor. 1712 80

Activating mutations of the RAS family of small GTPases are among the most common genetic events in human tumorigenesis. Constitutive activation of the three canonical family members, KRAS, NRAS, and HRAS segregate strongly by tissue type. Of these, KRAS mutations predominate in human tumors, including those arising from the colon and lung. We sought to compare the oncogenic contributions of different RAS isoforms in a comparable genetic setting and to explore downstream molecular changes that may explain the apparent differential oncogenic effects of the various RAS family members. We utilized colorectal cancer cell lines characterized by oncogenic KRAS in parallel with isogenically derived lines in which the mutant allele has been disrupted. We additionally attempted to reconstitute the isogenic derivatives with oncogenic forms of other RAS family members and analyze them in parallel. Pairwise analysis of HCT 116 and DLD-1 cell lines as well as their isogenic derivatives reveals distinct K-RAS(G13D) signatures despite the genetic similarities of these cell lines. In DLD-1, for example, oncogenic K-RAS enhances the motility of these cells by downregulation of Rap1 activity, yet is not associated with increased ERK1/2 phosphorylation. In HCT 116, however, ERK1/2 phosphorylation is elevated relative to the isogenic derivative, but Rap1 activity is unchanged. K-RAS is uniquely oncogenic in the colonic epithelium, though the molecular aspects of its oncogenic contribution are not necessarily conserved across cell lines. We therefore conclude that the oncogenic contribution of K-RAS is a function of its multifaceted functionality and is highly context-dependent.
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PMID:Oncogenic KRAS provides a uniquely powerful and variable oncogenic contribution among RAS family members in the colonic epithelium. 1713 51

Tautomycetin is an antifungal antibiotic retaining potent immunosuppressive function. We have identified the roles of tautomycetin on cellular proliferation and transformation of colorectal cancer cells. The proliferation and anchorage-independent growth of HCT-15, HT-29, and DLD-1 colorectal cancer cells were efficiently inhibited without induction of apoptosis by 150 nmol tautomycetin. These growth inhibitory effects were dependent on p21Cip/WAF induction via the extracellular signal-regulated kinase pathway, and the tautomycetin effects were abolished in HCT-116 colon cells and eight other types of cells that did not induce p21Cip/WAF by 150 nmol tautomycetin. The crucial role of p21Cip/WAF1 in the extracellular signal-regulated kinase pathway-dependent antiproliferative responses by tautomycetin was confirmed by using p21Cip/WAF1 gene-deleted HCT-116 cells. The growth inhibitory effect of tautomycetin was acquired by regulation of Raf-1 activity through inhibition of protein phosphatase type 1 and protein phosphatase type 2A with high preference toward protein phosphatase type 1. Tautomycetin could be a potential drug for colorectal cancer.
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PMID:Tautomycetin inhibits growth of colorectal cancer cells through p21cip/WAF1 induction via the extracellular signal-regulated kinase pathway. 1717 26

The cellular functions regulated by 17beta-estradiol (E2) start after the hormone binds to its receptors (i.e., ERalpha and ERbeta). These act as ligand-dependent transcription factor transactivating target genes. In addition, E2 induces non-genomic actions, whose activation is triggered by a fraction of the ERs localized at the plasma membrane. Palmitoylation allows ERalpha to localize at the plasma membrane, to associate with caveolin-1, and, upon E2 stimulation, to activate rapid signals relevant for cell proliferation. The existence of a mechanism, which allows ERbeta localization at the plasma membrane and its putative role in anti-proliferative E2 effects is completely unknown. Here, the susceptibility of ERbeta to undergo palmitoylation and the role played by this process has been analyzed in DLD-1 containing endogenous ERbeta or in HeLa cells transiently transfected with ERbeta or ERalpha expression vectors. As for ERalpha, palmitoylation is necessary for ERbeta localization at the plasma membrane and its association with caveolin-1 but, in contrast to ERalpha, the E2 binding increases ERbeta association with caveolin-1 and the p38 member of MAPK family. Moreover, the palmitoyl acyl transferase (PAT) inhibitor blocks the ability of ERbeta-E2 complex to activate p38 impairing the receptor-dependent activation of downstream proapoptotic cascade (i.e., caspase-3 activation and poly(ADP-ribose)polymerase (PARP) cleavage). Consequently, palmitoylation must be considered to be a molecular device for ERbeta, which allows these receptors to interact with the plasma membrane and to regulate E2-induced non-genomic functions relevant to the anti-proliferative effect of this hormone.
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PMID:Role of ERbeta palmitoylation in the inhibition of human colon cancer cell proliferation. 1739 84

Estrogen receptors (ERalpha and ERbeta) mediate opposite functions on cancer growth induced by 17beta-estradiol (E2). E2 binding to ERalpha induces a cancer promoting response, whereas E2 binding to ERbeta exerts a protective action against cancer growth. Moreover, E2 can diversely modulate the ERalpha and ERbeta levels intensifying or decreasing their actions in target tissues. Only molecular mechanisms at the root of E2 ability to down-regulate the ERalpha levels are known. Here, we report the first molecular mechanism underlying E2-induced ERbeta up-regulation in DLD-1 colon cancer cells. E2 induces a short term (2 and 4h after stimulation) translation of ERbeta mRNA followed by a late (24h after stimulation) enhanced transcription. Both processes required the E2-induced persistent and palmitoylation-dependent p38/MAPK activation. Overall, our data suggest a finely tuned control exerted by rapid signals on different cellular molecular events important for the protective effects of E2 against colon cancer growth.
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PMID:17Beta-estradiol induces ERbeta up-regulation via p38/MAPK activation in colon cancer cells. 1752 58

Our laboratory has been investigating the use of compounds which disrupt beta-catenin/T cell factor (TCF) binding to treat human colon cancer. There are several cysteine residues on the surface of beta-catenin where it binds to TCF. Some bis[2-(acylamino)phenyl] disulfides might have the ability to form a disulfide bond with the cysteine residues of beta-catenin, leading to inhibition of the growth of human colon cells. Bis[2-(acylamino)phenyl] disulfides were screened to inhibit the growth of cancer cells. Among them, bis[2-(2,2-dimethylpropanoylamino)phenyl] disulfide (1) had promising inhibitory effects (HCT116, IC50: 9.7 microM; DLD-1, IC50: 6.9 microM) on cell proliferation, and did not show any cytotoxicity among normal human fibroblast CCD-1059SK cells even at 200 microM. This derivative reduced the beta-catenin/TCF4 association in the HCT116 cells to ca. 50% at 150 microM. Furthermore, it activated markedly the phosphorylation of c-Jun N-terminal kinase (JNK) connected to stress-activated apoptosis at a lower concentration (30 microM). In view of cell cycle analyses, Hoechst staining, and terminal deoxynucleotidyl transferase-mediated dUTP-biotin Nick end-labeling (TUNEL) assays along with the above results, it is likely that 1 inhibited the growth of HCT116 cells through pathways including the JNK-mediated apoptosis.
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PMID:Growth inhibition of human colon cancer cell line HCT116 by bis[2-(acylamino)phenyl] disulfide and its action mechanism. 1845 18

Mitogen activated protein kinase phosphatase-3 (MKP-3) is a putative tumor suppressor. When transiently overexpressed, MKP-3 dephosphorylates and inactivates extracellular signal regulated kinase (ERK) 1/2. Little is known about the roles of endogenous MKP-3, however. We previously showed that MKP-3 is upregulated in cell lines that express oncogenic Ras. Here we tested the roles of endogenous MKP-3 in modulating ERK1/2 under conditions of chronic stimulation of the Ras/Raf/MEK1/2/ERK1/2 pathway by expression of oncogenic Ras. We used two cell lines: H-ras MCF10A, breast epithelial cells engineered to express H-Ras, and DLD-1, colon cancer cells that express endogenous Ki-Ras. First, we found that MKP-3 acts in a negative feedback loop to suppress basal ERK1/2 when oncogenic Ras stimulates the Ras/Raf/MEK1/2/ERK1/2 cascade. ERK1/2 was required to maintain elevated MKP-3, indicative of a negative feedback loop. Accordingly, knockdown of MKP-3, via siRNA, increased ERK1/2 phosphorylation. Second, by using siRNA, we found that MKP-3 helps establish the sensitivity of ERK1/2 to extracellular activators by limiting the duration of ERK1/2 phosphorylation. Third, we found that the regulation of ERK1/2 by MKP-3 is countered by the complex regulation of MKP-3 by ERK1/2. Potent ERK1/2 activators stimulated the loss of MKP-3 within 30 min due to an ERK1/2-dependent decrease in MKP-3 protein stability. MKP-3 levels recovered within 120 min due to ERK1/2-dependent resynthesis. Preventing MKP-3 resynthesis, via siRNA, prolonged ERK1/2 phosphorylation. Altogether, these results suggest that under the pressure of oncogenic Ras expression, MKP-3 reins in ERK1/2 by serving in ERK1/2-dependent negative feedback pathways.
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PMID:Reciprocal regulation of extracellular signal regulated kinase 1/2 and mitogen activated protein kinase phosphatase-3. 1877 77

Proline oxidase (POX), a flavoenzyme localized at the inner mitochondrial membrane, catalyzes the first step of proline degradation by converting proline to pyrroline-5-carboxylate (P5C). POX is markedly elevated during p53-induced apoptosis and generates proline-dependent reactive oxygen species (ROS), specifically superoxide radicals, to induce apoptosis through both mitochondrial and death receptor pathways. These previous studies also showed suppression of the mitogen-activated protein kinase pathway leading us to broaden our exploration of proliferative signaling. In our current report, we used DLD-1 colorectal cancer cells stably transfected with the POX gene under the control of a tetracycline-inducible promoter and found that three pathways which cross talk with each other were downregulated by POX: the cyclooxygenase-2 (COX-2) pathway, the epidermal growth factor receptor (EGFR) pathway and the Wnt/beta-catenin pathway. First, POX markedly reduced COX-2 expression, suppressed the production of prostaglandin E2 (PGE(2)) and importantly, the growth inhibition by POX was partially reversed by treatment with PGE(2.) Phosphorylation of EGFR was decreased with POX expression and the addition of EGF partially reversed the POX-dependent downregulation of COX-2. Wnt/beta-catenin signaling was decreased by POX in that phosphorylation of glycogen synthase kinase-3beta (GSK-3beta) was decreased on the one hand and phosphorylation of beta-catenin was increased on the other. There changes led to decreased accumulation of beta-catenin and decreased beta-catenin/TCF/LEF-mediated transcription. Our newly described POX-mediated suppression of proliferative signaling together with the previously reported induction of apoptosis suggested that POX could function as a tumor suppressor. Indeed, in human colorectal tissue samples, immunohistochemically-monitored POX was dramatically decreased in tumors compared with normal counterparts. Thus, POX metabolism of substrate proline affects multiple signaling pathways, modulating both apoptosis and tumor growth, and could be an attractive target to metabolically control the cancer phenotypes.
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PMID:Proline oxidase, a p53-induced gene, targets COX-2/PGE2 signaling to induce apoptosis and inhibit tumor growth in colorectal cancers. 1879 9

Scaffold proteins for MAP kinase (MAPK) signalling modules play an important role in the specific and efficient signal transduction of the relevant MAPK cascades. Here, we investigated the function of the scaffolding protein c-Jun NH(2)-terminal kinase (JNK)-associated leucine zipper protein (JLP) by depleting it in cultured cells using a short hairpin RNA (shRNA) against human JLP. HeLa and DLD-1 cells stably expressing the shRNA showed a defect in cell migration. The re-expression of full-length shRNA-resistant mouse JLP rescued the impaired cell migration of the JLP-depleted HeLa cells; whereas, a C-terminal deletion mutant of mouse JLP, which failed to bind the G protein G(alpha13), showed little or no effect on the cell migration defect. Furthermore, although a constitutively active G(alpha13) enhanced the migration of control HeLa cells, the G(alpha13)-induced cell migration was significantly suppressed in the JLP-depleted HeLa cells. Taken together, these results suggest that JLP regulates cell migration through an interaction with G(alpha13).
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PMID:The scaffold protein c-Jun NH2-terminal kinase-associated leucine zipper protein regulates cell migration through interaction with the G protein G(alpha 13). 1882 71

Activated EGF receptor (EGFR) plays an oncogenic role in several human malignancies. Although the intracellular effects of EGFR are well studied, its ability to induce and modulate tumor angiogenesis is less understood. We found previously that oncogenic EGFR can be shed from cancer cells as cargo of membrane microvesicles (MVs), which can interact with surfaces of other cells. Here we report that MVs produced by human cancer cells harboring activated EGFR (A431, A549, DLD-1) can be taken up by cultured endothelial cells, in which they elicit EGFR-dependent responses, including activation of MAPK and Akt pathways. These responses can be blocked by annexin V and its homodimer, Diannexin, both of which cloak phosphatidylserine residues on the surfaces of MVs. Interestingly, the intercellular EGFR transfer is also accompanied by the onset of VEGF expression in endothelial cells and by autocrine activation of its key signaling receptor (VEGF receptor-2). In A431 human tumor xenografts in mice, angiogenic endothelial cells stain positively for human EGFR and phospho-EGFR, while treatment with Diannexin leads to a reduction of tumor growth rate and microvascular density. Thus, we propose that oncogene-containing tumor cell-derived MVs could act as a unique form of angiogenesis-modulating stimuli and are capable of switching endothelial cells to act in an autocrine mode.
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PMID:Endothelial expression of autocrine VEGF upon the uptake of tumor-derived microvesicles containing oncogenic EGFR. 1923 31


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