Search results for "Proto-Oncogene Proteins c-raf"
showing 10 items of 11 documents
Enhanced expression of the proto-oncogenes fos and raf in the rhabdomyosarcoma cell line BA-HAN-1C after differentiation induction with retinoic acid…
1990
BA-HAN-IC is a clonal rat rhabdomyosarcoma cell line consisting of proliferating mononuclear tumor cells, some of which spontaneously fuse to form terminally differentiated post-mitotic myotubes. Exposure of BA-HAN-IC cells to retinoic acid (RA) or N-methylformamide (NMF) resulted in a significant inhibition of proliferation (p less than 0.001) and in cellular differentiation, as evidenced by a significant increase in the creatine kinase (CK) activity (p less than 0.05) and the number of terminally differentiated post-mitotic myotubes (p less than 0.001). Furthermore, between 5% (NMF) and 30% (RA) of the mononuclear tumor cells exhibited ultrastructural features of rhabdomyogenic differenti…
Efficient Control of raf Gene Expression by CAP and Two Raf Repressors that Bend DNA in Opposite Directions
1999
The plasmid-borne raf operon of Escherichia coli encodes proteins involved in the uptake and utilisation of the trisaccharide raffinose. The operon is subject to dual regulation; to negative control by the binding of RafR repressor to twin operators, O1 and O2, and to positive control by the cAMP-binding protein, CAP. We have identified the CAP binding site (CBS) as a 22 bp palindromic sequence with incomplete dyad symmetry by deletion analysis, DNasel footprinting and electrophoretic mobility shift assays (EMSA) of CAP-DNA complexes. The CBS is centred 60.5 bp upstream of the transcription start point and partially overlaps O1. In vivo, CAP increases rafA (alpha-galactosidase) gene express…
Geldanamycin and its derivatives as Hsp90 inhibitors
2012
The Hsp90 molecule, one of the most abundant heat shock proteins in mammalian cells, maintains homeostasis and prevents stress-induced cellular damage. Hsp90 is expressed under normal conditions at a level of about 1-2 Percent of total proteins, while its expression increases 2-10 fold in cancer cells. The two main constitutively expressed isoforms of Hsp90 are known as Hsp90-alpha and Hsp90-beta, and their upregulation is associated with tumor progression, invasion and formation of metastases, as well as development of drug resistance. The Hsp90 is a key target for many newly established, potent anticancer agents containing Hsp90 N-terminal ATP binding inhibitors, such as geldanamycin, and…
β1D Integrin Inhibits Cell Cycle Progression in Normal Myoblasts and Fibroblasts
1998
Integrins are alphabeta heterodimeric transmembrane receptors involved in the regulation of cell growth and differentiation. The beta1 integrin subunit is widely expressed in vivo and is represented by four alternatively spliced cytoplasmic domain isoforms. beta1D is a muscle-specific variant of beta1 integrin and a predominant beta1 isoform in striated muscles. In the present study we showed that expression of the exogenous beta1D integrin in C2C12 myoblasts and NIH 3T3 or REF 52 fibroblasts inhibited cell proliferation. Unlike the case of the common beta1A isoform, adhesion of beta1D-transfected C2C12 myoblasts specifically via the expressed integrin did not activate mitogen-activated pro…
Quantification of the Raf-C1 Interaction With Solid-Supported Bilayers
2002
By use of the quartz crystal microbalance technique, the interaction of the Raf-Ras binding domain (RafRBD) and the cysteine-rich domain Raf-C1 with lipids was quantified by using solid-supported bilayers immobilized on gold electrodes deposited on 5 MHz quartz plates. Solid-supported lipid bilayers were composed of an initial octanethiol monolayer chemisorbed on gold and a physisorbed phospholipid monolayer varying in its lipid composition as the outermost layer. The integrity of bilayer preparation was monitored by impedance spectroscopy. For binding experiments, a protein construct comprising the RafRBD and Raf-C1 linked to the maltose binding protein and a His tag, termed MBP-Raf-C1, wa…
Synthesis and biological evaluation of cycloalkylidene carboxylic acids as novel effectors of Ras/Raf interaction.
2002
The protooncogenes Ras and Raf play important roles in signal transduction pathways regulated by mitogen-activated protein kinases. Mutations of Ras that arrest the protein in its active state are frequently implicated in tumor formation. We used Ras and Raf proteins in the yeast two-hybrid system to search for natural or synthesized substances capable of modulating Ras/Raf interaction by specifically binding to one of the interacting partners. We found that cycloalkylidene carboxylic acids enhanced Ras/Raf interaction by acting on the cysteine-rich domain of Raf. Several analogues of the active substance 2-cyclohexylidene propanoic acid were synthesized and the importance of the semicyclic…
Dimerization of the kinase ARAF promotes MAPK pathway activation and cell migration.
2014
The RAF family of kinases mediates RAS signaling, and RAF inhibitors can be effective for treating tumors with BRAF V600E mutant protein. However, RAF inhibitors paradoxically accelerate metastasis in RAS -mutant tumors and become ineffective in BRAF V600E tumors because of reactivation of downstream mitogen-activated protein kinase (MAPK) signaling. We found that the RAF isoform ARAF has an obligatory role in promoting MAPK activity and cell migration in a cell type–dependent manner. Knocking down ARAF prevented the activation of MAPK kinase 1 (MEK1) and extracellular signal–regulated kinase 1 and 2 (ERK1/2) and decreased the number of protrusions from tumor cell spheroids in three-dimensi…
Dephosphorylation of p-ERK1/2 in relation to tumor remission after HER-2 and Raf1 blocking therapy in a conditional mouse tumor model
2006
Several studies have shown that HER-2/neu (erbB-2) blocking therapy strategies can cause tumor remission. However, the responsible molecular mechanisms are not yet known. Both ERK1/2 and Akt/PKB are critical for HER-2-mediated signal transduction. Therefore, we used a mouse tumor model that allows downregulation of HER-2 in tumor tissue by administration of anhydrotetracycline (ATc). Switching-off HER-2 caused a rapid tumor remission by more than 95% within 7 d of ATc administration compared to the volume before switching-off HER-2. Interestingly, HER-2 downregulation caused a dephosphorylation of p-ERK1/2 by more than 80% already before tumor remission occurred. Levels of total ERK protein…
B-Raf Acts via the ROCKII/LIMK/Cofilin Pathway To Maintain Actin Stress Fibers in Fibroblasts
2004
Members of the Raf family of serine/threonine protein kinases have been well studied in a variety of organisms ranging from Drosophila to humans. Three raf homologues (raf-1, B-raf, and A-raf) exist in mammals, while a single prototypic homologue exists in lower organisms. A wealth of genetic and biochemical data have indicated that Raf family members are signaling kinases that are integral components of the conserved Ras/Raf/MEK/ERK signaling cascade. Following activation by Ras-dependent mechanisms, Raf protein kinases act as mitogen-activated protein (MAP) kinase kinase kinases, which phosphorylate and activate the type 1/2 MAP kinase kinases, also known as MEK1/2. These dual-specificity…
The mitotic kinase Aurora-A promotes distant metastases by inducing epithelial-to-mesenchymal transition in ERα+ breast cancer cells
2013
In this study, we demonstrate that constitutive activation of Raf-1 oncogenic signaling induces stabilization and accumulation of Aurora-A mitotic kinase that ultimately drives the transition from an epithelial to a highly invasive mesenchymal phenotype in estrogen receptor α-positive (ERα(+)) breast cancer cells. The transition from an epithelial- to a mesenchymal-like phenotype was characterized by reduced expression of ERα, HER-2/Neu overexpression and loss of CD24 surface receptor (CD24(-/low)). Importantly, expression of key epithelial-to-mesenchymal transition (EMT) markers and upregulation of the stemness gene SOX2 was linked to acquisition of stem cell-like properties such as the ab…