ORCID Profile
0000-0002-6065-663X
Current Organisation
Deakin University
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: American Association for Cancer Research (AACR)
Date: 03-04-2023
DOI: 10.1158/1535-7163.22523091
Abstract: Supplementary figure 4 shows phosphorylated ERK staining in an adenoma from a ACDX2 mouse
Publisher: Springer Science and Business Media LLC
Date: 22-10-2007
Publisher: Elsevier BV
Date: 04-2004
DOI: 10.1016/S1535-6108(04)00087-X
Abstract: The Raf/MEK/ERK pathway is a conserved signaling module controlling cell growth, proliferation, apoptosis, and differentiation. Constitutive activation of this pathway is involved in malignant transformation by several oncogenes, most notably, Ras. The recent discovery by Davies et al. of somatic mutations in the B-RAF gene in human tumors has generated enormous interest in how Raf kinases are regulated and how mutations in B-RAF lead to transformation. A recent study in Cell by Wan et al. reports the crystal structure of the B-Raf kinase domain, providing important new insights into these questions.
Publisher: Springer Science and Business Media LLC
Date: 10-11-2014
DOI: 10.1038/ONC.2014.374
Publisher: Elsevier BV
Date: 05-2023
Publisher: Elsevier BV
Date: 08-2000
Publisher: Elsevier
Date: 2006
Publisher: Elsevier BV
Date: 09-2014
Publisher: American Association for Cancer Research (AACR)
Date: 03-04-2023
DOI: 10.1158/1535-7163.C.6543591.V1
Abstract: Abstract The EGFR/RAS/MEK/ERK signaling pathway (ERK/MAPK) is hyperactivated in most colorectal cancers. A current limitation of inhibitors of this pathway is that they primarily induce cytostatic effects in colorectal cancer cells. Nevertheless, these drugs do induce expression of proapoptotic factors, suggesting they may prime colorectal cancer cells to undergo apoptosis. As histone deacetylase inhibitors (HDACis) induce expression of multiple proapoptotic proteins, we examined whether they could synergize with ERK/MAPK inhibitors to trigger colorectal cancer cell apoptosis. Combined MEK/ERK and HDAC inhibition synergistically induced apoptosis in colorectal cancer cell lines and patient-derived tumor organoids i in vitro /i , and attenuated i Apc /i -initiated adenoma formation i in vivo /i . Mechanistically, combined MAPK/HDAC inhibition enhanced expression of the BH3-only proapoptotic proteins BIM and BMF, and their knockdown significantly attenuated MAPK/HDAC inhibitor–induced apoptosis. Importantly, we demonstrate that the paradigm of combined MAPK/HDAC inhibitor treatment to induce apoptosis can be tailored to specific MAPK genotypes in colorectal cancers, by combining an HDAC inhibitor with either an EGFR, KRAS sup G12C /sup or BRAF sup V600 /sup inhibitor in i KRAS/BRAF sup WT /sup /i i KRAS sup G12C /sup /i , i BRAF sup V600E /sup /i colorectal cancer cell lines, respectively. These findings identify a series of ERK/MAPK genotype-tailored treatment strategies that can readily undergo clinical testing for the treatment of colorectal cancer. /
Publisher: American Association for Cancer Research (AACR)
Date: 15-02-2005
DOI: 10.1158/0008-5472.CAN-04-1911
Abstract: RAS oncogenes are thought to play a role at multiple stages of tumorigenesis. The role and mechanisms by which RAS oncogenes maintain the transformed state of human cancer cells are poorly understood. Here, we have studied the role of oncogenic K-RAS in maintaining cytoskeletal disruption, cell adhesion and motility in metastatic colon carcinoma cells. Targeted deletion of K-RASG13D from HCT116 colon carcinoma cells restored their ability to assemble stress fibers and focal adhesions/complexes, accompanied by increased cell-matrix adhesion and reduced motility. We further show that oncogenic K-Ras induces high Rho activity, but uncouples Rho from stress fiber formation. This uncoupling required the maintenance of high levels of the activator protein-1 family member, Fra-1, via a mitogen-activated protein/extracellular signal-regulated kinase–dependent pathway. We also show that PI3-kinase signaling is required for the motility of HCT116 cells downstream of oncogenic K-Ras. Our findings suggest that mutated K-RAS oncogenes are essential for maintenance of the transformed and invasive phenotype of human colon cancer cells.
Publisher: Springer Science and Business Media LLC
Date: 25-03-2021
Publisher: American Association for Cancer Research (AACR)
Date: 03-04-2023
DOI: 10.1158/1535-7163.22523085
Abstract: Supplementary table 1
Publisher: American Association for Cancer Research (AACR)
Date: 03-04-2023
DOI: 10.1158/1535-7163.C.6543591
Abstract: Abstract The EGFR/RAS/MEK/ERK signaling pathway (ERK/MAPK) is hyperactivated in most colorectal cancers. A current limitation of inhibitors of this pathway is that they primarily induce cytostatic effects in colorectal cancer cells. Nevertheless, these drugs do induce expression of proapoptotic factors, suggesting they may prime colorectal cancer cells to undergo apoptosis. As histone deacetylase inhibitors (HDACis) induce expression of multiple proapoptotic proteins, we examined whether they could synergize with ERK/MAPK inhibitors to trigger colorectal cancer cell apoptosis. Combined MEK/ERK and HDAC inhibition synergistically induced apoptosis in colorectal cancer cell lines and patient-derived tumor organoids i in vitro /i , and attenuated i Apc /i -initiated adenoma formation i in vivo /i . Mechanistically, combined MAPK/HDAC inhibition enhanced expression of the BH3-only proapoptotic proteins BIM and BMF, and their knockdown significantly attenuated MAPK/HDAC inhibitor–induced apoptosis. Importantly, we demonstrate that the paradigm of combined MAPK/HDAC inhibitor treatment to induce apoptosis can be tailored to specific MAPK genotypes in colorectal cancers, by combining an HDAC inhibitor with either an EGFR, KRAS sup G12C /sup or BRAF sup V600 /sup inhibitor in i KRAS/BRAF sup WT /sup /i i KRAS sup G12C /sup /i , i BRAF sup V600E /sup /i colorectal cancer cell lines, respectively. These findings identify a series of ERK/MAPK genotype-tailored treatment strategies that can readily undergo clinical testing for the treatment of colorectal cancer. /
Publisher: American Association for Cancer Research (AACR)
Date: 03-04-2023
DOI: 10.1158/1535-7163.22523088
Abstract: Supplementary figure 5 shows mouse weight during treatment in two of the mouse studies
Publisher: Portland Press Ltd.
Date: 13-08-2010
DOI: 10.1042/BJ20100425
Abstract: The JNKs (c-Jun N-terminal kinases) are stress-activated serine/threonine kinases that can regulate both cell death and cell proliferation. We have developed a cell system to control JNK re-expression at physiological levels in JNK1/2-null MEFs (murine embryonic fibroblasts). JNK re-expression restored basal and stress-activated phosphorylation of the c-Jun transcription factor and attenuated cellular proliferation with increased cells in G1/S-phase of the cell cycle. To explore JNK actions to regulate cell proliferation, we evaluated a role for the cytosolic protein, STMN (stathmin)/Op18 (oncoprotein 18). STMN, up-regulated in a range of cancer types, plays a crucial role in the control of cell ision through its regulation of microtubule dynamics of the mitotic spindle. In JNK1/2-null or c-Jun-null MEFs or cells treated with c-Jun siRNA (small interfering RNA), STMN levels were significantly increased. Furthermore, a requirement for JNK/cJun signalling was demonstrated by expression of wild-type c-Jun, but not a phosphorylation-defective c-Jun mutant, being sufficient to down-regulate STMN. Critically, shRNA (small hairpin RNA)-directed STMN down-regulation in JNK1/2-null MEFs attenuated proliferation. Thus JNK/c-Jun regulation of STMN levels provides a novel pathway in regulation of cell proliferation with important implications for understanding the actions of JNK as a physiological regulator of the cell cycle and tumour suppressor protein.
Publisher: Elsevier BV
Date: 11-2019
Publisher: American Association for Cancer Research (AACR)
Date: 06-2016
DOI: 10.1158/1535-7163.MCT-15-0724
Abstract: Inhibitors of the bromodomain and extraterminal domain (BET) protein family attenuate the proliferation of several tumor cell lines. These effects are mediated, at least in part, through repression of c-MYC. In colorectal cancer, overexpression of c-MYC due to hyperactive WNT/β-catenin/TCF signaling is a key driver of tumor progression however, effective strategies to target this oncogene remain elusive. Here, we investigated the effect of BET inhibitors (BETi) on colorectal cancer cell proliferation and c-MYC expression. Treatment of 20 colorectal cancer cell lines with the BETi JQ1 identified a subset of highly sensitive lines. JQ1 sensitivity was higher in cell lines with microsatellite instability but was not associated with the CpG island methylator phenotype, c-MYC expression or lification status, BET protein expression, or mutation status of TP53, KRAS/BRAF, or PIK3CA/PTEN. Conversely, JQ1 sensitivity correlated significantly with the magnitude of c-MYC mRNA and protein repression. JQ1-mediated c-MYC repression was not due to generalized attenuation of β-catenin/TCF-mediated transcription, as JQ1 had minimal effects on other β-catenin/TCF target genes or β-catenin/TCF reporter activity. BETi preferentially target super-enhancer–regulated genes, and a super-enhancer in c-MYC was recently identified in HCT116 cells to which BRD4 and effector transcription factors of the WNT/β−catenin/TCF and MEK/ERK pathways are recruited. Combined targeting of c-MYC with JQ1 and inhibitors of these pathways additively repressed c-MYC and proliferation of HCT116 cells. These findings demonstrate that BETi downregulate c-MYC expression and inhibit colorectal cancer cell proliferation and identify strategies for enhancing the effects of BETi on c-MYC repression by combinatorial targeting the c-MYC super-enhancer. Mol Cancer Ther 15(6) 1217–26. ©2016 AACR.
Publisher: Informa UK Limited
Date: 11-2001
Publisher: American Association for Cancer Research (AACR)
Date: 07-11-2023
DOI: 10.1158/1535-7163.MCT-22-0101
Abstract: The EGFR/RAS/MEK/ERK signaling pathway (ERK/MAPK) is hyperactivated in most colorectal cancers. A current limitation of inhibitors of this pathway is that they primarily induce cytostatic effects in colorectal cancer cells. Nevertheless, these drugs do induce expression of proapoptotic factors, suggesting they may prime colorectal cancer cells to undergo apoptosis. As histone deacetylase inhibitors (HDACis) induce expression of multiple proapoptotic proteins, we examined whether they could synergize with ERK/MAPK inhibitors to trigger colorectal cancer cell apoptosis. Combined MEK/ERK and HDAC inhibition synergistically induced apoptosis in colorectal cancer cell lines and patient-derived tumor organoids in vitro, and attenuated Apc-initiated adenoma formation in vivo. Mechanistically, combined MAPK/HDAC inhibition enhanced expression of the BH3-only proapoptotic proteins BIM and BMF, and their knockdown significantly attenuated MAPK/HDAC inhibitor–induced apoptosis. Importantly, we demonstrate that the paradigm of combined MAPK/HDAC inhibitor treatment to induce apoptosis can be tailored to specific MAPK genotypes in colorectal cancers, by combining an HDAC inhibitor with either an EGFR, KRASG12C or BRAFV600 inhibitor in KRAS/BRAFWT KRASG12C, BRAFV600E colorectal cancer cell lines, respectively. These findings identify a series of ERK/MAPK genotype-tailored treatment strategies that can readily undergo clinical testing for the treatment of colorectal cancer.
Publisher: Springer Science and Business Media LLC
Date: 05-03-2015
DOI: 10.1038/ONC.2014.460
Publisher: Springer Science and Business Media LLC
Date: 29-01-2018
DOI: 10.1038/S41598-018-20176-9
Abstract: The ERK signalling pathway regulates key cell fate decisions in the intestinal epithelium and is frequently dysregulated in colorectal cancers (CRCs). Variations in the dynamics of ERK activation can induce different biological outcomes and are regulated by multiple mechanisms, including activation of negative feedback loops involving transcriptional induction of dual-specificity phosphatases (DUSPs). We have found that the nuclear ERK-selective phosphatase DUSP5 is downregulated in colorectal tumours and cell lines, as previously observed in gastric and prostate cancer. The DUSP5 promoter is methylated in a subset of CRC cell lines and primary tumours, particularly those with a CpG island methylator phenotype (CIMP). However, this epigenetic change alone could not account for reduced DUSP5 expression in CRC cells. Functionally, DUSP5 depletion failed to alter ERK signalling or proliferation in CRC cell lines, and its transgenic overexpression in the mouse intestine had minimal impact on normal intestinal homeostasis or tumour development. Our results suggest that DUSP5 plays a limited role in regulating ERK signalling associated with the growth of colorectal tumours, but that methylation the DUSP5 gene promoter can serve as an additional means of identifying CIMP-high colorectal cancers.
Publisher: American Association for Cancer Research (AACR)
Date: 03-04-2023
DOI: 10.1158/1535-7163.22523088.V1
Abstract: Supplementary figure 5 shows mouse weight during treatment in two of the mouse studies
Publisher: American Association for the Advancement of Science (AAAS)
Date: 18-08-2015
DOI: 10.1126/SCISIGNAL.AAB1111
Abstract: The transcriptional regulator c-JUN is a key mediator of the metastatic potential and drug resistance in melanoma.
Publisher: Frontiers Media SA
Date: 13-02-2015
Publisher: American Association for Cancer Research (AACR)
Date: 03-04-2023
DOI: 10.1158/1535-7163.22523094.V1
Abstract: Supplementary figure 3 shows combining trametinib with different classes of HDAC inhibitors in COLO 201 cells
Publisher: Cold Spring Harbor Laboratory
Date: 15-06-2020
DOI: 10.1101/2020.06.15.151456
Abstract: Excitotoxicity, a neuronal death process in neurological disorders, is initiated by over-stimulation of neuronal ionotropic glutamate receptors. The over-stimulated receptors dysregulate proteases, protein kinases and phosphatases, which in turn modify target neuronal proteins to induce cell death. To decipher this cell death mechanism, we used quantitative proteomics, phosphoproteomics and N-terminomics to identify modified proteins in excitotoxic neurons. Data, available in ProteomeXchange (identifiers: PXD019527 and PXD019211), enabled us to identify over one thousand such proteins with calpains, cathepsins and over twenty protein kinases as their major modifiers. These protein modification events can potentially perturb signalling pathways governing cell survival, synaptogenesis, axonal guidance and mRNA processing. Importantly, blocking the modification of Src protein kinase, a signalling hub in excitotoxic neurons, protected against neuronal loss in vivo in a rat model of neurotoxicity. Besides offering new insights into excitotoxic neuronal death mechanism, our findings suggest potential neuroprotective therapeutic targets for treating neurological disorders. Multi-dimensional proteomic analysis identified proteins modified by proteolysis and altered phosphorylation in neurons undergoing excitotoxic cell death. Calpains, cathepsins and over twenty protein kinases are major modifiers of these proteins. These protein modification events are predicted to impact cell survival, axonal guidance, synaptogenesis and mRNA processing. Blocking modification of an identified protein Src, which acts as a major signalling hub in neurons, was protective against excitotoxic injury in vivo . Using multidimensional proteomic approaches, Ameen, et al . mapped the changes of proteome, phosphoproteome and N-terminome of cultured primary neurons during excitotoxicity, a crucial neuronal death process in neurological disorders. These proteomic changes document new excitotoxicity-associated molecular events, and offer insights into how these events are organized to induce neuronal death. Potential therapeutic relevance of these molecular events is illustrated by the demonstration that in vivo blockade of one of these events could protect against excitotoxic neuronal loss.
Publisher: Wiley
Date: 04-1996
Publisher: Elsevier BV
Date: 08-2001
DOI: 10.1016/S0376-8716(00)00219-2
Abstract: Between one- and two-thirds of all alcohol abusers have impairment of muscle function that may be accompanied by biochemical lesions and/or the presence of a defined myopathy characterised by selective atrophy of Type II fibres. Perturbations in protein metabolism are central to the effects on muscle and account for the reductions in muscle mass and fibre diameter. Ethanol abuse is also associated with abnormalities in carbohydrate (as well as lipid) metabolism in skeletal muscle. Ethanol-mediated insulin resistance is allied with the inhibitory effects of ethanol on insulin-stimulated carbohydrate metabolism. It acutely impairs insulin-stimulated glucose and lipid metabolism, although it is not known whether it has an analogous effect on insulin-stimulated protein synthesis. In alcoholic cirrhosis, insulin resistance occurs with respect to carbohydrate metabolism, although the actions of insulin to suppress protein degradation and stimulate amino acid uptake are unimpaired. In acute alcohol-dosing studies defective rates of protein synthesis occur, particularly in Type II fibre-predominant muscles. The relative amounts of mRNA-encoding contractile proteins do not appear to be adversely affected by chronic alcohol feeding, although subtle changes in muscle protein isoforms may occur. There are also rapid and sustained reductions in total (largely ribosomal) RNA in chronic studies. Loss of RNA appears to be related to increases in the activities of specific muscle RNases in these long-term studies. However, in acute dosing studies (less than 1 day), the reductions in muscle protein synthesis are not due to overt loss of total RNA. These data implicate a role for translational modifications in the initial stages of the myopathy, although changes in transcription and/or protein degradation may also be superimposed. These events have important implications for whole-body metabolism.
Publisher: American Association for Cancer Research (AACR)
Date: 13-06-2017
DOI: 10.1158/1078-0432.CCR-17-0466
Abstract: Histone deacetylase inhibitors (HDACi) are epigenome-targeting small molecules approved for the treatment of cutaneous T-cell lymphoma and multiple myeloma. They have also demonstrated clinical activity in acute myelogenous leukemia, non–small cell lung cancer, and estrogen receptor–positive breast cancer, and trials are underway assessing their activity in combination regimens including immunotherapy. However, there is currently no clear strategy to reliably predict HDACi sensitivity. In colon cancer cells, apoptotic sensitivity to HDACi is associated with transcriptional induction of multiple immediate-early (IE) genes. Here, we examined whether this transcriptional response predicts HDACi sensitivity across tumor type and investigated the mechanism by which it triggers apoptosis. Fifty cancer cell lines from erse tumor types were screened to establish the correlation between apoptotic sensitivity, induction of IE genes, and components of the intrinsic apoptotic pathway. We show that sensitivity to HDACi across tumor types is predicted by induction of the IE genes FOS, JUN, and ATF3, but that only ATF3 is required for HDACi-induced apoptosis. We further demonstrate that the proapoptotic function of ATF3 is mediated through direct transcriptional repression of the prosurvival factor BCL-XL (BCL2L1). These findings provided the rationale for dual inhibition of HDAC and BCL-XL, which we show strongly cooperate to overcome inherent resistance to HDACi across erse tumor cell types. These findings explain the heterogeneous responses of tumor cells to HDACi-induced apoptosis and suggest a framework for predicting response and expanding their therapeutic use in multiple cancer types.
Publisher: Elsevier BV
Date: 09-1996
Publisher: Public Library of Science (PLoS)
Date: 21-03-2014
Publisher: American Association for Cancer Research (AACR)
Date: 03-04-2023
DOI: 10.1158/1535-7163.22523100.V1
Abstract: Supplementary figure 2 shows the effect of trametinib plus panobinostat on colony formation in HCT 116 cells
Publisher: Elsevier BV
Date: 08-2002
DOI: 10.1016/S0003-9861(02)00244-8
Abstract: The Raf-1 kinase is the entry point to the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK-1/2) signaling pathway, which controls fundamental cellular functions including proliferation, differentiation, and survival. As such, Raf-1 is regulated by complex mechanisms that are incompletely understood. Recent results have shown that release from repression is an important event that facilitates the interaction of Raf-1 with the Ras activator and its substrate, MAPK/ERK-1/2 kinase. A number of distinct activation steps contribute in a combinatorial fashion to regulate and adjust Raf-1 activity. The efficiency of downstream signal transmission is modulated by protein:protein interactions, and new data consolidate an important role for kinase suppressor of ras (KSR) as a scaffolding protein. KSR is a dynamic scaffold whose function and localization is regulated by phosphorylation.
Publisher: Springer Science and Business Media LLC
Date: 30-03-2015
Publisher: American Association for Cancer Research (AACR)
Date: 03-04-2023
DOI: 10.1158/1535-7163.22523085.V1
Abstract: Supplementary table 1
Publisher: EMBO
Date: 05-2004
Publisher: The Company of Biologists
Date: 15-06-2021
DOI: 10.1242/DEV.199542
Abstract: Ets homologous factor (EHF) is a member of the epithelial-specific Ets (ESE) family of transcription factors. To investigate its role in development and epithelial homeostasis, we generated a series of novel mouse strains in which the Ets DNA-binding domain of Ehf was deleted in all tissues (Ehf−/−) or specifically in the gut epithelium. Ehf−/− mice were born at the expected Mendelian ratio, but showed reduced body weight gain, and developed a series of pathologies requiring most Ehf−/− mice to reach an ethical endpoint before reaching 1 year of age. These included papillomas in the facial skin, abscesses in the preputial glands (males) or vulvae (females), and corneal ulcers. Ehf−/−mice also displayed increased susceptibility to experimentally induced colitis, which was confirmed in intestinal-specific Ehf knockout mice. Gut-specific Ehf deletion also impaired goblet cell differentiation, induced extensive transcriptional reprogramming in the colonic epithelium and enhanced Apc-initiated adenoma development. The Ets DNA-binding domain of EHF is therefore essential for postnatal homeostasis of the epidermis and colonic epithelium, and its loss promotes colonic tumour development.
Publisher: American Association for Cancer Research (AACR)
Date: 03-04-2023
DOI: 10.1158/1535-7163.22523103.V1
Abstract: Supplementary Figure 1 shows the synergistic effect of trametinib plus panobinostat in CRC cell lines and PDTO's
Publisher: Springer Science and Business Media LLC
Date: 06-08-2006
DOI: 10.1038/NCB1465
Abstract: The Raf-MEK-ERK pathway couples growth factor, mitogenic and extracellular matrix signals to cell fate decisions such as growth, proliferation, migration, differentiation and survival. Raf-1 is a direct effector of the Ras GTPase and is the initiating kinase in this signalling cascade. Although Raf-1 activation is well studied, little is known about how Raf-1 is inactivated. Here, we used a proteomic approach to identify molecules that may inactivate Raf-1 signalling. Protein phosphatase 5 (PP5) was identified as an inactivator that associates with Raf-1 on growth factor stimulation and selectively dephosphorylates an essential activating site, Ser 338. The PP5-mediated dephosphorylation of Ser 338 inhibited Raf-1 activity and downstream signalling to MEK, an effect that was prevented by phosphomimetic substitution of Ser 338, or by ablation of PP5 catalytic function. Furthermore, depletion of endogenous PP5 increased cellular phospho-Ser 338 levels. Our results suggest that PP5 is a physiological regulator of Raf-1 signalling pathways.
Publisher: Springer Science and Business Media LLC
Date: 08-08-2011
DOI: 10.1038/ONC.2011.336
Abstract: Fos-related antigen 1 (Fra-1) is a Fos family member overexpressed in several types of human cancers. Here, we report that Fra-1 is highly expressed in the muscle-invasive form of the carcinoma of the bladder (80%) and to a lesser extent in superficial bladder cancer (42%). We demonstrate that in this type of cancer Fra-1 is regulated via a C-terminal instability signal and C-terminal phosphorylation. We show that manipulation of Fra-1 expression levels in bladder cancer cell lines affects cell morphology, motility and proliferation. The gene coding for AXL tyrosine kinase is directly upregulated by Fra-1 in bladder cancer and in other cell lines. Importantly, our data demonstrate that AXL mediates the effect of Fra-1 on tumour cell motility but not on cell proliferation. We suggest that AXL may represent an attractive therapeutic target in cancers expressing high Fra-1 levels.
Publisher: American Association for Cancer Research (AACR)
Date: 03-04-2023
DOI: 10.1158/1535-7163.22523100
Abstract: Supplementary figure 2 shows the effect of trametinib plus panobinostat on colony formation in HCT 116 cells
Publisher: American Association for Cancer Research (AACR)
Date: 03-04-2023
DOI: 10.1158/1535-7163.22523103
Abstract: Supplementary Figure 1 shows the synergistic effect of trametinib plus panobinostat in CRC cell lines and PDTO's
Publisher: Elsevier BV
Date: 11-2009
DOI: 10.1016/J.CELLSIG.2009.07.001
Abstract: The Raf-1 protein kinase is a major activator of the ERK MAPK pathway, which links signaling by a variety of cell surface receptors to the regulation of cell proliferation, survival, differentiation and migration. Signaling by Raf-1 is regulated by a complex and poorly understood interplay between phosphorylation events and protein-protein interactions. One important mode of Raf-1 regulation involves the phosphorylation-dependent binding of 14-3-3 proteins. Here, we have examined the mechanism whereby the C-terminal 14-3-3 binding site of Raf-1, S621, controls the activation of MEK-ERK signaling. We show that phosphorylation of S621 turns over rapidly and is enriched in the activated pool of endogenous Raf-1. The phosphorylation on this site can be mediated by Raf-1 itself but also by other kinase(s). Mutations that prevent the binding of 14-3-3 proteins to S621 render Raf-1 inactive by specifically disrupting its capacity to bind to ATP, and not by gross conformational alteration as indicated by intact MEK binding. Phosphorylation of S621 correlates with the inhibition of Raf-1 catalytic activity in vitro, but 14-3-3 proteins can completely reverse this inhibition. Our findings suggest that 14-3-3 proteins function as critical cofactors in Raf-1 activation, which induce and maintain the protein in a state that is competent for both ATP binding and MEK phosphorylation.
Publisher: Elsevier BV
Date: 10-1998
DOI: 10.1016/S0026-0495(98)90320-1
Abstract: Epidemiological studies suggest that alcohol consumption is an independent risk factor for the development of non-insulin-dependent diabetes mellitus (NIDDM). Alcoholism is known to be associated with increased plasma levels of two novel diols, 2,3-butanediol and 1,2-propanediol, metabolites known to impair insulin action in isolated adipocytes. This study examines whether 2,3-butanediol and 1,2-propanediol have the capacity to impair insulin action acutely in vivo in the rat. Using the euglycemic-hyperinsulinemic cl , it is shown that the two diols reduce whole-body glucose utilization (by approximately 30%), with the onset of insulin resistance in vivo occurring at plasma concentrations of 2,3-butanediol (33 micromol/L) at least one order of magnitude (P < .001) lower than 1,2-propanediol (432 micromol/L). Tracer methodologies using [U-14C]glucose and 2-deoxy[1-(3)H]glucose indicate that the reduction in whole-body glucose utilization is accompanied by a reduction in glucose uptake and glycogen synthesis in the skeletal muscle and heart. The association between elevated plasma diol levels and insulin resistance demonstrated in this report raises the question of whether there is a link between the high plasma diol levels in alcohol abusers and their increased susceptibility to NIDDM.
Publisher: Springer Science and Business Media LLC
Date: 29-08-2011
DOI: 10.1038/ONC.2011.375
Abstract: Fos-related antigen-1 (Fra-1) is a member of the Activator Protein-1 (AP-1) transcription factor superfamily that is overexpressed in a variety of cancers, including colon, breast, lung, bladder and brain. High Fra-1 levels are associated with enhanced cell proliferation, survival, migration and invasion. Despite its frequent overexpression, the molecular mechanisms that regulate the accumulation of Fra-1 proteins in tumour cells are not well understood. Here, we show that turnover of Fra-1, which does not require ubiquitylation, is cooperatively regulated by two distinct mechanisms-association with the 19S proteasomal subunit, TBP-1, and by a C-terminal degron, which acts independently of TBP-1, but is regulated by RAS-ERK (extracellular signal-regulated kinase) signalling. TBP-1 depletion stabilized Fra-1 and further increased its levels in tumour cells expressing RAS-ERK pathway oncogenes. These effects correlated with increased AP-1 transcriptional activity. We suggest that during Fra-1 degradation, association with TBP-1 provides a mechanism for ubiquitin-independent proteasomal recognition, while the C terminus of the protein regulates its subsequent proteolytic processing.
Publisher: American Association for Cancer Research (AACR)
Date: 04-2023
DOI: 10.1158/1535-7163.22523091.V1
Abstract: Supplementary figure 4 shows phosphorylated ERK staining in an adenoma from a ACDX2 mouse
Publisher: Wiley
Date: 1996
Publisher: Elsevier BV
Date: 06-2015
Publisher: Informa UK Limited
Date: 2007
DOI: 10.4161/CC.6.1.3593
Abstract: The Raf-1 kinase is an effector of Ras GTPases that lies at the apex of the three-tier Raf/MEK/ERK pathway. Raf-1 activation is a complex process that entails two major events--relief of autoinhibition imposed by the regulatory domain and kinase domain activation. Recent studies indicate that the transition of Raf-1 from an active to an inactive state bears similar complexity to the activation process. Both these events require dynamic changes in Raf-1 phosphorylation. Here, we discuss the critical role of phosphatases and feedback phosphorylation during activation and inactivation of Raf-1 signaling.
Publisher: Frontiers Media SA
Date: 02-02-2015
Publisher: Springer Science and Business Media LLC
Date: 17-03-2014
DOI: 10.1038/ONC.2014.26
Abstract: The proto-oncogene c-Jun is a component of activator protein-1 (AP-1) transcription factor complexes that regulates processes essential for embryonic development, tissue homeostasis and malignant transformation. Induction of gene expression by c-Jun involves stimulation of its transactivation ability and upregulation of DNA binding capacity. While it is well established that the former requires JNK-mediated phosphorylation of S63/S73, the mechanism(s) through which binding of c-Jun to its endogenous target genes is regulated remains poorly characterized. Here we show that interaction of c-Jun with chromatin is positively regulated by protein phosphatase 2A (PP2A) complexes targeted to c-Jun by the PR55α regulatory subunit. PR55α-PP2A specifically dephosphorylates T239 of c-Jun, promoting its binding to genes regulating tumour cell migration and invasion. PR55α-PP2A also enhanced transcription of these genes, without affecting phosphorylation of c-Jun on S63. These findings suggest a critical role for interplay between JNK and PP2A pathways determining the functional activity of c-Jun/AP-1 in tumour cells.
Publisher: Wiley
Date: 15-01-2002
Abstract: The Raf-1 kinase is regulated by phosphorylation, and Ser259 has been identified as an inhibitory phosphorylation site. Here we show that the dephosphorylation of Ser259 is an essential part of the Raf-1 activation process, and further reveal the molecular role of Ser259. The fraction of Raf-1 that is phosphorylated on Ser259 is refractory to mitogenic stimulation. Mutating Ser259 elevates kinase activity because of enhanced binding to Ras and constitutive membrane recruitment. This facilitates the phosphorylation of an activating site, Ser338. The mutation of Ser259 also increases the functional coupling to MEK, augmenting the efficiency of MEK activation. Our results suggest that Ser259 regulates the coupling of Raf-1 to upstream activators as well as to its downstream substrate MEK, thus determining the pool of Raf-1 that is competent for signalling. They also suggest a new model for Raf-1 activation where the release of repression through Ser259 dephosphorylation is the pivotal step.
Publisher: Wiley
Date: 10-1996
Publisher: Informa UK Limited
Date: 03-2003
Publisher: Cold Spring Harbor Laboratory
Date: 16-02-2021
DOI: 10.1101/2021.02.15.431252
Abstract: The EGFR/RAS/MEK/ERK signalling pathway (ERK/MAPK) is hyper-activated in most colorectal cancers (CRCs). A current limitation of inhibitors of this pathway is that they primarily induce cytostatic effects in CRC cells. Nevertheless, these drugs do induce expression of pro-apoptotic factors, suggesting they may prime CRC cells to undergo apoptosis. As histone deacetylase inhibitors (HDACi) induce expression of multiple pro-apoptotic proteins, we examined whether they could synergize with ERK/MAPK inhibitors to trigger CRC cell apoptosis. Combined MEK/ERK and HDAC inhibition synergistically induced apoptosis in CRC cell lines and patient-derived tumour organoids in vitro, and attenuated Apc -initiated adenoma formation in vivo . Mechanistically this effect was mediated through induction of the BH3-only pro-apoptotic proteins BIM and BMF. Importantly, we demonstrate that this treatment paradigm can be tailored to specific MAPK genotypes in CRCs, by combining HDACi with EGFR, KRAS G12C or BRAF V600 inhibitors in KRAS/BRAF WT KRAS G12C , BRAF V600E CRC cell lines respectively. These findings identify a novel ERK/MAPK genotype-targeted treatment paradigm for colorectal cancer.
Publisher: Informa UK Limited
Date: 05-2002
Publisher: American Association for Cancer Research (AACR)
Date: 03-04-2023
DOI: 10.1158/1535-7163.22523094
Abstract: Supplementary figure 3 shows combining trametinib with different classes of HDAC inhibitors in COLO 201 cells
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 2011
End Date: 2013
Funder: National Health and Medical Research Council
View Funded ActivityStart Date: 2012
End Date: 2014
Funder: National Health and Medical Research Council
View Funded ActivityStart Date: 2009
End Date: 2011
Funder: National Health and Medical Research Council
View Funded ActivityStart Date: 2013
End Date: 2015
Funder: National Health and Medical Research Council
View Funded ActivityStart Date: 2008
End Date: 2011
Funder: National Health and Medical Research Council
View Funded ActivityStart Date: 2018
End Date: 2021
Funder: National Health and Medical Research Council
View Funded Activity