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Activity of glycogen synthase kinase-3beta is down-regulated during transient differentiation of human colon cancer
Z Tuhackova1, E Sloncova, J Hlavacek
1Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 166 37 Praha 6, Czech Republic.
Abstract:
The increased phosphorylation and activity of protein kinase B (PKB/Akt) was found early upon butyrate treatment of HT-29 cells with a potent differentiating agent, sodium butyrate. It was accompanied by the increased phosphorylation of glycogen synthase kinase-3 (GSK-3) and the inhibition of the activity of GSK-3beta to catalyze phosphorylation of its substrate, translation initiation factor eIF2B. Phosphorylation of PKB and GSK-3 in HT-29 cells was reduced by wortmannin, the inhibitor of phosphatidylinositol-3' kinase (PI3'-kinase), which is upstream activator of PKB and GSK-3 in the intracellular signalling. Modulation of the activity and phosphorylation of these protein kinases during transient in vitro differentiation of HT-29 cells indicates that control of the PI3'-kinase/PKB-dependent signalling pathway may be implicated very early in the changes of malignant phenotype of HT-29 cells.
Insights
Sodium butyrate treatment increases protein kinase B (PKB/Akt) and glycogen synthase kinase-3 (GSK-3) phosphorylation in HT-29 cells. This suggests the phosphatidylinositol-3
Area of Science:
- Cellular biology
- Molecular signaling
- Cancer research
Background:
- Sodium butyrate is a potent differentiating agent used in cancer research.
- HT-29 cells are a human colorectal adenocarcinoma cell line often used to study differentiation.
- Protein kinase B (PKB/Akt) and glycogen synthase kinase-3 (GSK-3) are key intracellular signaling molecules.
Purpose of the Study:
- To investigate the early effects of sodium butyrate on intracellular signaling pathways in HT-29 cells.
- To determine the role of the phosphatidylinositol-3' kinase (PI3'-kinase)/PKB signaling pathway in butyrate-induced differentiation.
Main Methods:
- Treatment of HT-29 cells with sodium butyrate.
- Assessment of protein phosphorylation and kinase activity using biochemical assays.
- Inhibition of phosphatidylinositol-3' kinase (PI3'-kinase) with wortmannin.
Main Results:
- Early increase in protein kinase B (PKB/Akt) and glycogen synthase kinase-3 (GSK-3) phosphorylation upon butyrate treatment.
- Inhibition of GSK-3beta activity towards its substrate, translation initiation factor eIF2B.
- Wortmannin reduced PKB and GSK-3 phosphorylation, indicating PI3'-kinase pathway involvement.
Conclusions:
- The PI3'-kinase/PKB-dependent signaling pathway is modulated early during transient in vitro differentiation of HT-29 cells.
- Control of this pathway may be implicated in the early changes of the malignant phenotype of HT-29 cells.
- These findings highlight a potential therapeutic target for colorectal cancer.