HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Online-Only Appendix All Versions of this Article: db07-0343v1 56/9/2218    most recent Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Logie, L. Articles by Sutherland, C. Search for Related Content PubMed PubMed Citation Articles by Logie, L. Articles by Sutherland, C. Social Bookmarking                What's this?

Characterisation of a protein kinase B inhibitor in vitro and in insulin treated liver cells.

Division of Pathology and Neuroscience,
*MRC Protein Phosphorylation Unit,
^$Division of Biological Chemistry, University of Dundee, Dundee, Scotland.

Correspondence: c.d.sutherland{at}dundee.ac.uk

Key Words: PKB • AKT • PEPCK • insulin • Akti-1/2 • diabetes.

Objective:Abnormal expression of the hepatic gluconeogenic genes (glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK)) contributes to hyperglycemia. These genes are repressed by insulin but this process is defective in diabetes. Protein kinase B (PKB) is implicated in this action of insulin. An inhibitor of PKB, termed Akti-1/2, was recently reported, however the specificity and efficacy against insulin induced PKB was not reported. Our aim was to characterise the specificity and efficacy of Akti-1/2 in cells exposed to insulin and then establish whether inhibition of PKB is sufficient to prevent regulation of hepatic gene expression by insulin.

Design:Akti-1/2 was assayed against seventy kinases in vitro, and its ability to block PKB activation in cells exposed to insulin fully characterised.

Results:Akti-1/2 exhibits high selectivity toward PKB and PKBß. Complete inhibition of PKB activity is achieved in liver cells incubated with 1 to 10µM Akti-1/2 and this blocks insulin regulation of PEPCK and G6Pase expression. Our data demonstrates that only 5-10% of maximal insulin induced PKB is required to fully repress PEPCK and G6Pase expression. Finally, we demonstrate reduced insulin sensitivity of these gene promoters in cells exposed to sub-maximal concentrations of Akti-1/2, however full repression of the genes can still be achieved by high concentrations of insulin.

Conclusion:This work establishes the requirement for PKB activity in the insulin regulation of PEPCK, G6Pase and a third insulin regulated gene, IGFBP1, suggests a high degree of functional reserve and identifies Akti-1/2 as a useful tool to delineate PKB function in the liver.

CiteULike

Del.icio.us

Digg

Reddit

Technorati