Search results for "Enzyme Activation"
showing 10 items of 304 documents
Escherichia coli cytolethal distending toxin blocks the HeLa cell cycle at the G2/M transition by preventing cdc2 protein kinase dephosphorylation an…
1997
Cytolethal distending toxins (CDT) constitute an emerging heterogeneous family of bacterial toxins whose common biological property is to inhibit the proliferation of cells in culture by blocking their cycle at G2/M phase. In this study, we investigated the molecular mechanisms underlying the block caused by CDT from Escherichia coli on synchronized HeLa cell cultures. To this end, we studied specifically the behavior of the two subunits of the complex that determines entry into mitosis, i.e., cyclin B1, the regulatory unit, and cdc2 protein kinase, the catalytic unit. We thus demonstrate that CDT causes cell accumulation in G2 and not in M, that it does not slow the progression of cells th…
Apoptosis induced in hepatoblastoma HepG2 cells by the proteasome inhibitor MG132 is associated with hydrogen peroxide production, expression of Bcl-…
2002
This report is focused on the apoptotic effect induced by MG132, an inhibitor of 26S proteasome, in human hepatoma HepG2 cells. The results were compared with those obtained with non-transformed human Chang liver cells. MG132 reduced the viability of HepG2 cells in a time- and dose-dependent manner. The effect was in tight connection with the induction of apoptosis, as indicated by fluorescence microscopy and cytometric analysis, and was accompanied by a remarkable increase in the production of H2O2 and a reduction in mitochondrial transmembrane potential (Deltapsim). In addition cell death was prevented by antioxidants such as GSH, N-acetylcysteine or catalase. Western blot analysis showed…
Staurosporine-induced apoptosis in Chang liver cells is associated with down-regulation of Bcl-2 and Bcl-XL.
2004
A potent inhibitor of serine/threonine kinases, staurosporine exerts antiproliferative and apoptotic effects in many cancer cells, although the exact mechanism of its action is still unclear. This study examines the effects of staurosporine on Chang liver cells, an immortalized non-tumor cell line, in comparison with those caused in HuH-6 and HepG2 cells, two human hepatoma cell lines. Our results provide evidence that staurosporine promotes apoptosis in Chang liver cells as observed by flow cytometric analysis and acridine orange/ethidium bromide staining. The effect appeared already after 8 h of treatment and increased with treatment time and dose. After 48 h of exposure to 200 nM stauros…
Selective Stimulation of Hepatitis C Virus and Pestivirus NS5B RNA Polymerase Activity by GTP
1999
NS5B of the hepatitis C virus is an RNA template-dependent RNA polymerase and therefore the key player of the viral replicase complex. Using a highly purified enzyme expressed with recombinant baculoviruses in insect cells, we demonstrate a stimulation of RNA synthesis up to 2 orders of magnitude by high concentrations of GTP but not with ATP, CTP, UTP, GDP, or GMP. Enhancement of RNA synthesis was found with various heteropolymeric RNA templates, with poly(C)-oligo(G)12 but not with poly(A)-oligo(U)12. Several amino acid substitutions in polymerase motifs B, C, and D previously shown to be crucial for RdRp activity were tested for GTP stimulation of RNA synthesis. Most of these mutations, …
ΔNp73β is oncogenic in hepatocellular carcinoma by blocking apoptosis signaling via death receptors and mitochondria
2010
p73 belongs to the p53 family of transcription factors known to regulate cell cycle and apoptosis. The Trp73 gene has two promoters that drive the expression of two major p73 isoform subfamilies: TA and ΔN. In general, TAp73 isoforms show proapoptotic activities, whereas members of the N-terminally truncated (ΔN) p73 subfamily that lack the transactivation domain show antiapoptotic functions. We found that upregulation of ΔNp73 in hepatocellular carcinoma (HCC) correlated with reduced survival. Here, we investigated the molecular mechanisms accounting for the oncogenic role of ΔNp73 in HCC.ΔNp73β can directly interfere with the transcriptional activation function of the TA (containing the t…
A disintegrin-metalloproteinase prevents amyloid plaque formation and hippocampal defects in an Alzheimer disease mouse model
2004
Alzheimer disease (AD) is characterized by excessive deposition of amyloid beta-peptides (A beta peptides) in the brain. In the nonamyloidogenic pathway, the amyloid precursor protein (APP) is cleaved by the alpha-secretase within the A beta peptide sequence. Proteinases of the ADAM family (adisintegrin and metalloproteinase) are the main candidates as physiologically relevant alpha-secretases, but early lethality of knockout animals prevented a detailed analysis in neuronal cells. To overcome this restriction, we have generated transgenic mice that overexpress either ADAM10 or a catalytically inactive ADAM10 mutant. In this report we show that a moderate neuronal overexpression of ADAM10 i…
Interventions to Slow Aging in Humans: Are We Ready?
2015
The workshop entitled 'Interventions to Slow Aging in Humans: Are We Ready?' was held in Erice, Italy, on October 8-13, 2013, to bring together leading experts in the biology and genetics of aging and obtain a consensus related to the discovery and development of safe interventions to slow aging and increase healthy lifespan in humans. There was consensus that there is sufficient evidence that aging interventions will delay and prevent disease onset for many chronic conditions of adult and old age. Essential pathways have been identified, and behavioral, dietary, and pharmacologic approaches have emerged. Although many gene targets and drugs were discussed and there was not complete consens…
IκB kinase-driven nuclear factor-κB activation in patients with asthma and chronic obstructive pulmonary disease.
2011
Background Nuclear factor-κB (NF-κB) is a transcriptional factor of different inflammatory patterns involved in asthma and chronic obstructive pulmonary disease (COPD) that is tightly controlled by IκB kinase (IKK) complex. Objective We investigated the dysregulation of IKK-driven NF-κB activation in patients with asthma and COPD. Methods We assessed IKKα and IKKβ expression and activation, their regulation by glucocorticosteroids, and their involvement in IL-8 synthesis in PBMCs isolated from asthmatic patients, healthy smokers (HSs), patients with COPD, and control subjects. PBMCs from control subjects were stimulated with TNF-α and cigarette smoke extract in the presence or absence of fl…
Design, Synthesis and Biological Evaluation of 7-Chloro-9
2019
Glycogen synthase kinase-3β (GSK-3β) represents a relevant drug target for the treatment of neurodegenerative pathologies including Alzheimer’s disease. We herein report on the optimization of a novel class of GSK-3β inhibitors based on the tofacitinib-derived screen hit 3-((3R,4R)-3-((7-chloro-9H-pyrimido[4,5-b]indol-4-yl)(methyl)amino)-4-methylpiperidin-1-yl)-3-oxopropanenitrile (1). We synthesized a series of 19 novel 7-chloro-9H-pyrimido[4,5-b]indole-based derivatives and studied their structure–activity relationships with focus on the cyanoacetyl piperidine moiety. We unveiled the crucial role of the nitrile group and its importance for the activity of this compound series. A successfu…
Maturation of barley cysteine endopeptidase expressed in Trichoderma reesei is distorted by incomplete processing
2002
Maturation of barley cysteine endopeptidase B (EPB) in Trichoderma reesei was studied with metabolic inhibitors, Western blotting, and immuno microscopy. The inactive 42-kDa recombinant EPB proprotein, first detected in apical cells, was sequentially processed in a time-dependent manner to a secreted polypeptide of 38.5 kDa, and thereafter, to polypeptides of 37.5, 35.5, and 32 kDa exhibiting enzyme activity both in the hyphae and culture medium. The sizes of the different forms of recombinant EPB were in accordance with molecular masses calculated from the deduced amino acid sequence, assuming cleavage at four putative Kex2p sites present in the 42-kDa proprotein. Both the liquid and the z…