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Growth factor-stimulated protein synthesis is inhibited by sodium orthovanadate
F Viñals1, F R McKenzie, J Pouysségur
1Institute of Signaling, Developmental Biology and Cancer Research, Nice, France. fvinals@bell.ub.es
Abstract:
The study of intracellular signaling pathways has been aided by the use of sodium orthovanadate, a cell-permeable inhibitor of tyrosine phosphatases. However, long-term addition of sodium orthovanadate is often cytotoxic. In this study we demonstrate that the growth factor-mediated increase in the rate of protein synthesis was inhibited by sodium orthovanadate. This effect of sodium orthovanadate was dose-dependent, with an IC50 of 40 microM and maximal inhibition obtained at 100 microM. As a consequence, the fetal bovine serum-mediated induction of the immediate-early genes, c-Fos and MKP-1, at the protein level was inhibited by orthovanadate. Orthovanadate's ability to attenuate protein synthesis was partially reversible, and was no longer evident when the agent was added 6 h after addition of growth factor to cells. Analysis of several elements of signaling pathways which are known to regulate protein synthesis in a positive manner (p42/p44 MAPK, AKT and p70 S6K stimulation, and hyperphosphorylation of PHAS-I) were not inhibited but rather were stimulated by orthovanadate. Thus, sodium orthovanadate is a potent inhibitor of growth factor-stimulated protein synthesis independent of p42/p44 MAPK or PI3K-p70 S6K activation.
Insights
Sodium orthovanadate inhibits protein synthesis by blocking growth factor signaling. This tyrosine phosphatase inhibitor
Area of Science:
- Cellular Biology
- Molecular Biology
- Biochemistry
Background:
- Sodium orthovanadate is a cell-permeable tyrosine phosphatase inhibitor used to study intracellular signaling.
- Prolonged use of sodium orthovanadate can lead to cytotoxicity.
- Growth factor signaling pathways regulate protein synthesis.
Purpose of the Study:
- To investigate the effect of sodium orthovanadate on growth factor-mediated protein synthesis.
- To determine the dose-dependency and reversibility of orthovanadate's effect on protein synthesis.
- To elucidate the impact of orthovanadate on key signaling pathways regulating protein synthesis.
Main Methods:
- Treatment of cells with varying concentrations of sodium orthovanadate.
- Measurement of protein synthesis rates.
- Analysis of immediate-early gene expression (c-Fos, MKP-1) at the protein level.
- Assessment of signaling pathway activation (MAPK, AKT, p70 S6K, PHAS-I phosphorylation).
Main Results:
- Sodium orthovanadate inhibited growth factor-stimulated protein synthesis in a dose-dependent manner (IC50 = 40 microM).
- Orthovanadate suppressed the protein induction of c-Fos and MKP-1.
- The inhibition of protein synthesis was partially reversible and dependent on the timing of orthovanadate addition.
- Key signaling molecules (p42/p44 MAPK, AKT, p70 S6K) and PHAS-I were stimulated, not inhibited, by orthovanadate.
Conclusions:
- Sodium orthovanadate is a potent inhibitor of growth factor-stimulated protein synthesis.
- This inhibition is independent of p42/p44 MAPK or PI3K-p70 S6K pathway activation.
- Orthovanadate offers a tool to dissect protein synthesis regulation, despite potential cytotoxicity concerns.