Conferring specificity on the ubiquitous Raf/MEK signalling pathway

O’Neill, Eric; Kölch, Walter

doi:10.1038/sj.bjc.6601488

Cited by 151 publications

(112 citation statements)

References 42 publications

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“…Glycogen synthase kinase 3β is reported to repress Wnt/β-catenin pathway (Zheng et al, 2010). MEK kinase 1 occupies a pivotal role in a network of phosphorylating enzymes integrating cellular responses to mitogenic and metabolic stimuli and mediates the anti-apoptotic effect of the BcrAbl oncogene (O'Neill and Kolch, 2004). In response to TGF-β, Smad4 promotes the binding of the Smad2/ Smad4/FAST-1 complex to DNA and induces apoptosis by modulating Bcl-2/Bax balance (Owens, 2008).…”

Section: Discussionmentioning

confidence: 99%

Effects of Parafibromin Expression on the Phenotypes and Relevant Mechanisms in the DLD-1 Colon Carcinoma Cell Line

Zhao¹,

Sun²,

Zhu³

et al. 2013

Asian Pacific Journal of Cancer Prevention

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Background: Parafibromin is a protein encoded by the HRPT2 (hyperparathyroidism 2) oncosuppressor gene and its down-regulated expression is involved in pathogenesis of parathyroid, breast, gastric and colorectal carcinomas. This study aimed to clarify the effects of parafibromin expression on the phenotypes and relevant mechanisms of DLD-1 colon carcinoma cells. Methods: DLD-1 cells transfected with a parafibromin-expressing plasmid were subjected to examination of phenotype, including proliferation, differentiation, apoptosis, migration and invasion. Phenotype-related proteins were measured by Western blot. Parafibromin and ki-67 expression was detected by immunohistochemistry on tissue microarrays. Results: The transfectants showed higher proliferation by CCK-8, better differentiation by electron microscopy and ALP activity and more apoptotic resistance to cisplatin by DNA fragmentation than controls. There was no difference in early apoptosis by annexin V, capase-3 activity, migration and invasion between DLD-1 cells and their transfectants. Ectopic parafibromin expression resulted in down-regulated expression of smad4, MEKK, GRP94, GRP78, GSK3β-ser9, and Caspase-9. However, no difference was detectable in caspase-12 and -8 expression. A positive relationship was noted between parafibromin and ki-67 expression in colorectal carcinoma. Conclusions: Parafibromin overexpression could promote cell proliferation, apoptotic resistance, and differentiation of DLD-1 cells.

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Section: Discussionmentioning

confidence: 99%

Effects of Parafibromin Expression on the Phenotypes and Relevant Mechanisms in the DLD-1 Colon Carcinoma Cell Line

Zhao¹,

Sun²,

Zhu³

et al. 2013

Asian Pacific Journal of Cancer Prevention

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“…The Ras/Raf/mitogen-activated/extracellular-regulated kinase (MEK)/extracellular signal regulated kinase (ERK) pathway plays a pivotal role in control of proliferation and differentiation and, owing to its role as a gatekeeper of this pathway, Raf appears an attractive therapeutic target (O'Neill and Kolch, 2004;Wilhelm et al, 2004). The Raf-kinase family comprises the A-Raf, B-Raf and Raf-1 isoforms in vertebrates as well as D-Raf and LIN-45 in Drosophila and Caenorhabditis, respectively.…”

Section: Introductionmentioning

confidence: 99%

Functional analysis of the regulatory requirements of B-Raf and the B-RafV600E oncoprotein

et al. 2006

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The BRAF V600E mutation is found in approximately 6% of human cancers and mimics the phosphorylation of the kinase domain activation segment. In wild-type B-Raf (B-Raf wt ), activation segment phosphorylation is thought to cooperate with negative charges within the N-region for full activation. In contrast to Raf-1, the N-region of B-Raf is constitutively negatively charged owing to the presence of residues D447/D448 and the phosphorylation of S446. Therefore, it has been suggested that this hallmark predisposes B-Raf for oncogenic activation. In this study, we demonstrate that neutralizing mutations of these residues (in particular S446 and S447), or uncoupling of B-Raf from Ras-guanine 5 0 -triphosphate (GTP), strongly reduce the biological activity of B-Raf in a PC12 cell differentiation assay. We also confirm that S365 is a 14-3-3 binding site, and determine that mutation of this residue rescues the impaired biological activity of B-Raf proteins with a neutralized N-region, suggesting that the N-region opposes a 14-3-3-mediated transition into an inactive conformation. However, in the case of B-Raf V600E , although complete N-region neutralization resulted in a 2.5-fold reduction in kinase activity in vitro, this oncoprotein strongly induced PC12 differentiation or transformation and epithelial-mesenchymal transition of MCF-10A cells regardless of its N-region charge. Furthermore, the biological activity of B-Raf V600E was independent of its ability to bind Ras-GTP. Our analysis identifies important regulatory differences between B-Raf wt and B-Raf V600E and suggests that B-Raf V600E cannot be inhibited by strategies aimed at blocking S446 phosphorylation or Ras activation. Keywords: Ras; 14-3-3 proteins; b-Catenin; E-cadherin; mammary epithelial cells IntroductionThe Ras/Raf/mitogen-activated/extracellular-regulated kinase (MEK)/extracellular signal regulated kinase (ERK) pathway plays a pivotal role in control of proliferation and differentiation and, owing to its role as a gatekeeper of this pathway, Raf appears an attractive therapeutic target (O'Neill and Kolch, 2004;Wilhelm et al., 2004). The Raf-kinase family comprises the A-Raf, B-Raf and Raf-1 isoforms in vertebrates as well as D-Raf and LIN-45 in Drosophila and Caenorhabditis, respectively. B-Raf, the major ERK activator in vertebrates, is required for the maintenance of basal ERK activity and displays the most potent transforming activity (Papin et al., 1998;Brummer et al., 2002;Mercer and Pritchard, 2003). All isoforms share three highly conserved regions (CRs; Figure 1a): the N-terminal CR1 contains the Ras-guanine 5 0 -triphosphate (GTP)-binding domain (RBD), which initiates the interaction with Ras-GTP through a conserved arginine residue (R188 in B-Raf) that is required for the recruitment and activation of Raf at the plasma membrane. Consequently, mutation of this residue prevents Ras/Raf interaction and renders D-Raf, B-Raf and Raf-1 unresponsive to most extracellular signals (Hou et al., 1995;Marais et al., 1997;Brummer et al., 2002). The ...

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“…These include: Raf kinase inhibitory protein (RKIP), kinase suppressor of Ras, 14-3-3 and Mp-1. [40][41][42][43] Many of these scaffolding proteins serve to modulate the activity of key components. Some scaffolding proteins (for example, Mp-1) serve to promote a complex between MEK and ERK to enhance signal transduction.…”

Section: Overview Of the Ras/raf/mek/erk Pathwaymentioning

confidence: 99%