In mammalian cells, IR-IGF-IR signaling through PI 3-kinase/AKT (protein kinase B) is crucial for inhibition of certain metabolic pathways (inhibition of PEPCK and IGFBP-1 gene transcription) as well as apoptosis. However, the physiologically relevant transcription regulators down stream of PI 3-kinase/PKB have not been identified. In C-elegans defects in either the insulin like receptor (DAF-2) or phosphatidylinositol-3 kinase (AGE-1) genes prolongs life span by two fold. Inactivation of the DAF-16 gene abolishes this extra longevity and alleviates the need for Akt signaling. This indicates that DAF-16 gene product lies downstream of the DAF-2/AGE-1 in the insulin-like signaling pathway and that the role of Akt is to antagonize DAF-16 function. The investigator proposes to examine the role of DAF-16 MS in mediating the negative effect of insulin on genes that control gluconeogenesis in the liver, such as PEPCK, and genes that control apoptosis in neurons and islet, such as Fas/Fas ligand. The goal of the work proposed is to characterize the C-elegans DAF-16 protein and its mammalian homologues and to assess the effect of insulin on the activity/expression of DAF-16 MS and their target genes in liver and pancreas. They will Examine the effect of insulin/nutritional manipulations on expression of DAF-16 MS in rat liver and pancreas. Characterize known DNA binding sites in targets of DAF-16 MS, such as PEPCK and amylase. Examine the effect of insulin/nutritional manipulations on the phosphorylation activity and cellular location of DAF-16 MS so as to understand the consequences of insulin sufficiency/lack on expression of genes that regulate gluconeogenesis in the liver and apoptosis in pancreas and neuronal cells.
|Cahill, C M; Tzivion, G; Nasrin, N et al. (2001) Phosphatidylinositol 3-kinase signaling inhibits DAF-16 DNA binding and function via 14-3-3-dependent and 14-3-3-independent pathways. J Biol Chem 276:13402-10|