1,721,043 research outputs found
Involvement of thiol transferase- and thioredoxin-dependent systems in the protection of 'essential' thiol groups of ornithine decarboxylase
No full textOrnithine decarboxylase (ODC), an enzyme with 'essential' thiol group(s), may be inactivated in vitro by removal of thiol reducing agents and re-activated by soluble factors from rat liver in the presence of NADPH or GSH. The NADPH- and GSH-dependent reducing systems were sepated and resolved into three components, called factors A, B1 and B2, by chromatographic techniques. Factor B1 (M(r) 12000) could reactivate ODC in the presence of GSH of co-purified with thiol transferase activity. Factor B2 (M(r) 12000) and factor A (M(r) approx. 110000) were both needed to re-activate ODC in the presence of NADPH, and co-purified with thioredoxin and thioredoxin reductase activity respectively. In an attempt to investigate the physiological role of the 'essential' thiol group(s) of ODC, erythroleukemia cells were incubated with NN-bis-(2-chloroethyl)-N'-nitrosourea, t-butyl hydroperoxide and vinblastine, which are known to increase the cellular GSSG/GSH ratio, azelaic acid, an inhibitor of thioredoxin reductase, and sodium arsenite, a strong inhibitor of the ODC-re-activating factors. All these compounds were able to decrease significantly the ODC activity induced in these cells. These results suggest that the thiol transferase- and thioredoxin-dependent systems may be physiologically relevant in maintaining ODC in the active, reduced, state
Zinc is required for the expression of ornithine decarboxylase in a difluoromethylornithine-resistant cell line
No full textDilution of quiescent L1210-DFMO(r) (difluoromethylornithine-resistant) cells in fresh medium containing serum led to the induction of ornithine decarboxylase (ODC) and to the expression of its mRNA, as determined by a sensitive solution-hybridization-RNAase-protection assay. Addition of the chelating agent diethylenetriaminepenta-acetic acid (DTPA) at seeding time caused an inhibition of the induction of ODC activity by up to 90%, and only Zn2+ of the bivalent metal ions tested was effective in reversing this effect. The inhibition of the induction of ODC activity was accompanied by a marked decrease, prevented by Zn2+ supplementation, of the accumulation of immunoreactive ODC protein and ODC mRNA. DTPA treatment also caused a slight acceleration of ODC turnover. These results indicate that a restricted Zn2+ availability in L1210-DFMO(r) cells impairs ODC induction remarkably, mainly by affecting the expression of the messenger
Effect of sodium arsentie on the induction and turnover of ornithine decarboxylase activity in erythroleukemia cells
No full textSodium arsenite proved effective in preventing the induction of ornithine decarboxylase (ODC) activity elicited by dilution of Friend erythroleukemia cells in fresh medium. A 50 per cent inhibition was produced at approximately 1 μM arsenite and complete inhibition was obtained at concentrations above 10 μM. However, addition of arsenite 5 h after cell dilution, i.e. when ODC was already induced, appeared to stabilize the enzyme. The half‐life of ODC activity, measured after cycloheximide treatment, increased almost six‐fold after addition of sodium arsenite. Agents known to provoke oxidative alteration of the thiol‐redox status in cells, also caused a similar effect on the induction and stability of ODC. Copyright © 1989 John Wiley & Sons Ltd
Stabilization of ornithine decarboxylase in erythroleukemia cells depleted of ATP
No full textOrnithine decarboxylase activity in Friend erythroleukemia cells decayed with a half-life of 50 minutes after addition of cycloheximide and at a faster rate after addition of spermidine. Incubation with a medium containing dinitrophenol and 2-deoxyglucose in place of glucose caused ATP depletion and blocked the turnover of ornithine decarboxylase, even after addition of spermidine. Dinitrophenol in the presence of glucose was able to provoke only a slight increase of the half-life of the enzyme. These results suggest that degradation of ornithine decarboxylase in erythroleukemia cells is ATP-dependent. © 1989
Myocarditis in COVID-19 patients: current problems
No full textMyocarditis has been reported as a possible clinical presentation or complication in patients with coronavirus disease (COVID)-19 due to SARS-CoV-2. Despite the alarm that this possibility generated among physicians, there is paucity of information about mechanisms, prevalence, prognosis, diagnosis and therapy of myocarditis in the context of COVID-19. This brief review has the goal to revise and summarize current knowledge on myocarditis in COVID-19 patients and underline problems especially related to diagnosis and treatment
Location of the phosphorylation site for casein kinase-2 within the amino acid sequence of ornithine decarboxylase.
No full textEffect of ATP depletion and phenanthroline on the spermidine-mediated decay of ornithine decarboxylase in erythroleukemia cells
No full textAddition of spermidine to Friend erythroleukemia cells caused a rapid decay of ornithine decarboxylase (ODC) activity and the accumulation of a ODC-antizyme complex. The induction of antizyme only partially accounted for the decrease of ODC activity by a direct inhibition of the enzyme. However, the antizyme induction was accompanied by a marked reduction of the half-life of ODC. Shift of the cells to an ATP-depleting medium prevented the spermidine-elicited decay of ODC activity as well as the accumulation of ODC-antizyme complex. However, ODC appeared to be stabilized even when ATP depletion was performed 40 min after spermidine addition, in the presence of high levels of antizyme. Similar results were obtained by treating the cells with phenanthroline, a heavy metal chelator and protease inhibitor. These findings indicate that ATP and some metalloprotease(s) may be involved in the degradation pathway of ODC, even in the presence of high levels of polyamines. © 1990
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