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Decrease of mRNA levels and biosynthesis of sucrase-isomaltase but not dipeptidylpeptidase IV in forskolin or
D Darmoul1, L Baricault, C Sapin
1Unité de Recherches sur la différenciation cellulaire intestinale, Institut National de la Santé et de la Recherche Médicale, U178, Villejuif, France.
Abstract:
Treatment for 48 h of differentiated, confluent Caco-2 cells with 2.5 10(-5) M forskolin or 10(-6) M monensin, which produces a significant decrease of the de novo biosynthesis of sucrase-isomaltase, does not change quantitatively the de novo biosynthesis of dipeptidylpeptidase IV. Western blot analysis and silver nitrate staining indicate that neither drug induces any modification in the steady state expression of these two brush border hydrolases. Northern blot analysis shows that the level of dipeptidylpeptidase IV mRNA does not change in treated as compared to control Caco-2 cells. In contrast, forskolin and monensin dramatically decrease the level of sucrase-isomaltase mRNA. These observations suggest a separate regulation of biosynthesis for sucrase-isomaltase and dipeptidylpeptidase IV in intestinal cells. The mechanisms responsible for such a difference are discussed. Among them, the role of glucose metabolism, which is perturbed by both drugs, appears to be of crucial importance.
Insights
Forskolin and monensin treatments affect intestinal cell enzyme production differently. Sucrase-isomaltase biosynthesis and mRNA levels decrease, while dipeptidylpeptidase IV remains unchanged, suggesting distinct regulatory pathways.
Area of Science:
- Cell Biology
- Biochemistry
- Molecular Biology
Background:
- Caco-2 cells are a widely used model for studying intestinal epithelial cell differentiation and function.
- Brush border hydrolases, such as sucrase-isomaltase and dipeptidylpeptidase IV, play crucial roles in nutrient digestion and absorption.
- Understanding the regulation of these enzymes is vital for comprehending intestinal physiology and disease.
Purpose of the Study:
- To investigate the differential regulation of sucrase-isomaltase and dipeptidylpeptidase IV biosynthesis in differentiated Caco-2 cells.
- To determine the impact of forskolin and monensin on the expression and mRNA levels of these two brush border hydrolases.
- To elucidate potential mechanisms underlying the separate regulation of these enzymes, particularly the role of glucose metabolism.
Main Methods:
- Treatment of differentiated Caco-2 cells with forskolin or monensin for 48 hours.
- Quantitative assessment of de novo biosynthesis for sucrase-isomaltase and dipeptidylpeptidase IV.
- Western blot analysis to evaluate steady-state protein expression.
- Silver nitrate staining for protein expression analysis.
- Northern blot analysis to measure mRNA levels.
Main Results:
- Forskolin and monensin significantly decreased the de novo biosynthesis of sucrase-isomaltase.
- Neither drug altered the quantitative de novo biosynthesis of dipeptidylpeptidase IV.
- Protein expression levels of both enzymes remained unchanged by the treatments.
- Forskolin and monensin dramatically reduced sucrase-isomaltase mRNA levels.
- Dipeptidylpeptidase IV mRNA levels were unaffected by the drug treatments.
Conclusions:
- Sucrase-isomaltase and dipeptidylpeptidase IV biosynthesis are regulated separately in intestinal cells.
- Forskolin and monensin primarily affect sucrase-isomaltase expression at the mRNA level.
- Perturbation of glucose metabolism by these drugs may be a crucial factor in the differential regulation observed.
- These findings highlight distinct molecular mechanisms controlling the expression of brush border hydrolases.