Search results for "Protein"
showing 10 items of 21431 documents
Cytotoxic necrotizing factor type 2 produced by virulent Escherichia coli modifies the small GTP-binding proteins Rho involved in assembly of actin s…
1994
Cytotoxic necrotizing factor type 2 (CNF2) produced by Escherichia coli strains isolated from intestinal and extraintestinal infections is a dermonecrotic toxin of 110 kDa. We cloned the CNF2 gene from a large plasmid carried by an Escherichia coli strain isolated from a lamb with septicemia. Hydropathy analysis of the deduced amino acid sequence revealed a largely hydrophilic protein with two potential hydrophobic transmembrane domains. The N-terminal half of CNF2 showed striking homology (27% identity and 80% conserved residues) to the N-terminal portion of Pasteurella multocida toxin. Methylamine protection experiments and immunofluorescence studies suggested that CNF2 enters the cytosol…
HMG-CoA reductase inhibitors (statins) as anticancer drugs (Review)
2005
Apart from their lipid lowering activity, HMG-CoA reductase inhibitors (statins) impair numerous cellular functions associated with metastasis, e.g. gene expression, angiogenesis, cell adhesion, cell motility and invasiveness. Furthermore, statins have impact on apoptotic cell death and modulate cellular susceptibility to cell killing by anticancer drugs and ionizing radiation. Part of the effects provoked by statins are due to the inhibition of the prenylation of low molecular weight GTPases, in particular Ras and Rho, which play key roles in signaling evoked by stimulation of cell surface receptors. C-terminal lipid modification of Ras/Rho GTPases is essential for their correct intracellu…
Rho GTPases are over-expressed in human tumors.
1999
Small GTPases of the Rho family are involved in the regulation of a variety of cellular processes, such as the organization of the microfilamental network, cell-cell contact and malignant transformation. To address the question of whether Rho proteins are involved in carcinogenesis in man, we compared their expression in tumors from colon, breast and lung with that of the corresponding normal tissue originating from the same patient. As shown by Rho-specific 32P-ADP-ribosylation, as well as Western-blot analysis, the amount of RhoA protein was largely increased in all 3 types of tumors tested. The most dramatic differences in the expression of Rho GTPases were observed in breast tissue. All…
Targeting the mevalonate pathway for improved anticancer therapy.
2009
The mevalonate pathway is important for the generation of isoprene moieties thereby providing the basis for the biosynthesis of molecules required for maintaining membrane integrity, steroid production and cell respiration. Additionally, isoprene precursors are indispensable for the prenylation of regulatory proteins such as Ras and Ras-homologous (Rho) GTPases. These low molecular GTP-binding proteins play key roles in numerous signal transduction pathways stimulated upon activation of cell surface receptors by ligand binding. Thus, Ras/Rho proteins eventually regulate cell proliferation, tumor progression and cell death induced by anticancer therapeutics. Lipid modification of Ras/Rho pro…
Delivery of proteins into living cells by reversible membrane permeabilization with streptolysin-O
2001
The pore-forming toxin streptolysin O (SLO) can be used to reversibly permeabilize adherent and nonadherent cells, allowing delivery of molecules with up to 100 kDa mass to the cytosol. Using FITC-labeled albumin, 10 5 –10 6 molecules were estimated to be entrapped per cell. Repair of toxin lesions depended on Ca 2+ -calmodulin and on intact microtubules, but was not sensitive to actin disruption or to inhibition of protein synthesis. Resealed cells were viable for days and retained the capacity to endocytose and to proliferate. The active domains of large clostridial toxins were introduced into three different cell lines. The domains were derived from Clostridium difficile B-toxin and Clo…
Late Activation of Stress-activated Protein Kinases/c-Jun N-terminal Kinases Triggered by Cisplatin-induced DNA Damage in Repair-defective Cells
2011
Although stress-activated protein kinases/c-Jun N-terminal kinases (SAPK/JNK) are rapidly activated by genotoxins, the role of DNA damage in this response is not well defined. Here we show that the SEK1/MKK4-mediated dual phosphorylation of SAPK/JNK (Thr-183/Tyr-185) correlates with the level of cisplatin-DNA adducts at late times (16–24 h) after drug treatment in both human and mouse cells. Transfection of platinated plasmid DNA also caused SAPK/JNK activation. A defect in transcription-coupled nucleotide excision repair resting on a mutation in Cockayne syndrome group B protein promoted the late SAPK/JNK activation following cisplatin exposure. Signaling to SAPK/JNK was accompanied by act…
Inhibition of small G proteins of the Rho family by statins orClostridium difficiletoxin B enhances cytokine-mediated induction of NO synthase II
2000
In order to investigate the involvement of Ras and/or Rho proteins in the induction of the inducible isoform of nitric oxide synthase (NOS II) we used HMG-CoA reductase inhibitors (statins) and Clostridium difficile toxin B (TcdB) as pharmacological tools. Statins indirectly inhibit small G proteins by preventing their essential farnesylation (Ras) and/or geranylgeranylation (Rho). In contrast, TcdB is a glucosyltransferase and inactivates Rho-proteins directly. Human A549/8- and DLD-1 cells as well as murine 3T3 fibroblasts were preincubated for 18 h with statins (1–100 μM) or TcdB (0.01–10 ng ml−1). Then NOS II expression was induced by cytokines. NOS II mRNA was measured after 4–8 h by R…
Mtlinteracts with members of Egfr signaling and cell adhesion genes in the Drosophila eye
2011
Mtl is a member of the Rho family of small GTPases in Drosophila. It was shown that Mtl is involved in planar cell polarity (PCP) establishment, together with other members of the same family like Cdc42, Rac1, Rac2 and RhoA. However, while Rac1, Rac2 and RhoA function downstream of Dsh in Fz/PCP signaling and upstream of a JNK cassette, Mtl and Cdc42 do not. To determine the functional context of Mtl during PCP establishment in the Drosophila eye, we performed a loss-of-function screen to search for dominant modifiers of a sev>Mtl rough eye phenotype. In addition, genetic interaction assays with candidate genes were also carried out. Our results show that Mtl interacts genetically with memb…
Activation of astroglial phospholipase D activity by phorbol ester involves ARF and Rho proteins.
2000
Primary cultures of rat cortical astrocytes express phospholipase D (PLD) isoforms 1 and 2 as determined by RT-PCR and Western blot. Basal PLD activity was strongly (10-fold) increased by 4beta-phorbol-12beta,13alpha-dibutyrate (PDB) (EC(50): 56 nM), an effect which was inhibited by Ro 31-8220 (0.1-1 microM), an inhibitor of protein kinase C (PKC), and by brefeldin A (10-100 microg/ml), an inhibitor of ADP-ribosylating factor (ARF) activation. Pretreatment of the cultures with Clostridium difficile toxin B-10463 (0.1-1 ng/ml), which inactivates small G proteins of the Rho family, led to a breakdown of the astroglial cytoskeleton; concomitantly, PLD activation by PDB was reduced by up to 50%…
Metabotropic glutamate receptors activate phospholipase D in astrocytes through a protein kinase C-dependent and Rho-independent pathway.
2003
Metabotropic glutamate receptors (mGluRs) are G protein-coupled receptors that mediate phospholipase D (PLD) activation in brain, but the mechanism underlying this response remains unclear. Here we used primary cultures of astrocytes as a cell model to explore the mechanism that links mGluRs to PLD. Glutamate activated both phospholipase C (PLC) and PLD with equal potency and this effect was mimicked by L-cysteinesulfinic acid, a putative neurotransmitter previously shown to activate mGluRs coupled to PLD, but not PLC, in adult brain. PLD activation by glutamate was dependent on Ca(2+) mobilization and fully blocked by both protein kinase C (PKC) inhibitors and PKC down-regulation, suggesti…