Inhibition of protein synthesis is believed to be mediated through ..

15/07/2009 · Protein synthesis inhibition ..

Thesis and Essay: CHX protein synthesis inhibition …

Didemnin B (DB) is one member of a class of natural cyclic depsipeptides that display potent cytotoxicity in vitro. The detailed mechanism of action of DB is unknown, although it appears to involve the inhibition of protein biosynthesis. Additional activities of DB have established DB as a rapid and potent inducer of apoptosis in HL-60 cells. Our aim was to determine if the induction of apoptosis by DB is mediated through inhibition of protein synthesis in MCF-7 human breast carcinoma cells. Apoptosis was observed only at ≥ 100 nM DB, even though inhibition of protein synthesis occurred at much lower DB concentrations (IC50 = 12 nM). DB-induced apoptosis was mediated by caspase activation, since cleavage of the caspase substrate poly(ADP-ribose) polymerase was observed as early as 6 hr after DB exposure. Two additional protein synthesis inhibitors, cycloheximide (CHX) and emetine (ET), failed to induce apoptosis at concentrations that completely inhibited protein synthesis. Moreover, DB-induced apoptosis was enhanced only slightly by pre- and co-treatment with CHX and ET. Thus, inhibition of protein synthesis alone was not sufficient to induce apoptosis in these cells. As a measure of antiproliferative potential, DB (1-5 nM) inhibited the colony forming ability of MCF7 cells regardless of pretreatment with CHX. In conclusion, additional effects of DB, independent of protein synthesis inhibition, are proposed to account for its ability to induce apoptosis and prevent cell proliferation. Copyright (C) 1999 Elsevier Science Inc.

T1 - A Quantitative regional analysis of protein synthesis inhibition in the rat brain following localized injection of cycloheximide

of CHX and LTM on protein synthesis ..

Mycalamide B (MycB) is a marine sponge-derived natural product with potent antitumor activity. Although it has been shown to inhibit protein synthesis, the molecular mechanism of action by MycB remains incompletely understood. We verified the inhibition of translation elongation by in vitro HCV IRES dual luciferase assays, ribosome assembly, and in vivo [ 35S]methinione labeling experiments. Similar to cycloheximide (CHX), MycB inhibits translation elongation through blockade of eEF2-mediated translocation without affecting the eEF1A-mediated loading of tRNA onto the ribosome, AUG recognition, or dipeptide synthesis. Using chemical footprinting, we identified the MycB binding site proximal to the C3993 28S rRNA residue on the large ribosomal subunit. However, there are also subtle, but significant differences in the detailed mechanisms of action of MycB and CHX. First, MycB arrests the ribosome on the mRNA one codon ahead of CHX. Second, MycB specifically blocked tRNA binding to the E-site of the large ribosomal subunit. Moreover, they display different polysome profiles in vivo. Together, these observations shed new light on the mechanism of inhibition of translation elongation by MycB. Published by Cold Spring Harbor Laboratory Press.

T1 - Differential impairment of auditory and contextual fear conditioning by protein synthesis inhibition in C57BL/6N mice

AB - Background/Aims: Inflammatory cytokines may enhance renal injury in post-diarrheal hemolytic uremic syndrome (Stx HUS) by enhancing the cytotoxic effect of Shiga toxins (Stx). The sources of inflammatory cytokines in Stx HUS are unclear. Since Stx-1 potently inhibits protein synthesis by glomerular epithelial cells (GEC) and increases cytokine release by renal epithelial cells, we examined Stx-1 regulation of cytokine production by human GEC. Methods: Stx-1 (and cycloheximide (CHX), another protein synthesis inhibitor) cytotoxicity, protein synthesis inhibition, and effect on interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor (TNF) release and mRNA levels were determined. Results: Stx-1 alone had a modest stimulatory effect on inflammatory cytokine production by GEC that occurred at toxin concentrations ranging from minimal to 50% inhibition of protein synthesis. CHX, at concentrations that produced similar inhibition of protein synthesis, increased IL-1, IL-6, and TNF protein release and mRNA accumulation, but in a different time- and dose-dependent pattern than Stx. Lipopolysaccharide (LPS) did not change IL-1, but stimulated IL-6 and TNF production. LPS and Stx-1 combined stimulated production of all three cytokines to a greater extent than either toxin alone. Conclusion: These data indicate that: (1) Stx-1 alone modestly stimulates GEC inflammatory cytokine production; (2) LPS and Stx-1 combined can potently enhance GEC cytokine release, and (3) this action of Stx-1 may relate in part to inhibition of protein synthesis but cannot be fully attributed to this effect.

T1 - Aurintricarboxylic acid inhibits protein synthesis independent, sanguinarine-induced apoptosis and oncosis


Protein synthesis inhibition ..

N2 - Didemnin B (DB) is one member of a class of natural cyclic depsipeptides that display potent cytotoxicity in vitro. The detailed mechanism of action of DB is unknown, although it appears to involve the inhibition of protein biosynthesis. Additional activities of DB have established DB as a rapid and potent inducer of apoptosis in HL-60 cells. Our aim was to determine if the induction of apoptosis by DB is mediated through inhibition of protein synthesis in MCF-7 human breast carcinoma cells. Apoptosis was observed only at ≥ 100 nM DB, even though inhibition of protein synthesis occurred at much lower DB concentrations (IC50 = 12 nM). DB-induced apoptosis was mediated by caspase activation, since cleavage of the caspase substrate poly(ADP-ribose) polymerase was observed as early as 6 hr after DB exposure. Two additional protein synthesis inhibitors, cycloheximide (CHX) and emetine (ET), failed to induce apoptosis at concentrations that completely inhibited protein synthesis. Moreover, DB-induced apoptosis was enhanced only slightly by pre- and co-treatment with CHX and ET. Thus, inhibition of protein synthesis alone was not sufficient to induce apoptosis in these cells. As a measure of antiproliferative potential, DB (1-5 nM) inhibited the colony forming ability of MCF7 cells regardless of pretreatment with CHX. In conclusion, additional effects of DB, independent of protein synthesis inhibition, are proposed to account for its ability to induce apoptosis and prevent cell proliferation. Copyright (C) 1999 Elsevier Science Inc.

Cycloheximide inhibit protein synthesis

AB - The effects of intraventricular cycloheximide (CHX) pretreatment were examined on the ability of rats to recall a light position discrimination task. The CHX pretreatment used inhibited brain protein synthesis at the time of training by 71%. Following treatment with CHX the animals demonstrated no retention of the task 18 hr later. Free feeding for 24 hr prior to treatment with cerebro-spinal-like fluid (CSF) produced similar effects as CHX. It is proposed that the amnesic effect of CHX in this behavioral paradigm may be a nonspecific action resulting from decreased motivation. Both the CHX-treated and satiated animals exhibited low responding levels during training, despite comparable behavioral activity levels for the CHX- and CSF-treated groups.