Insulin-like Growth Factor-1-induced Phosphorylation of the Forkhead Family Transcription Factor FKHRL1 Is Mediated by Akt Kinase in PC12 Cells

作者：Wenhua Zheng, Satyabrata Kar, Rémi Quirion · 发表于：Journal of Biological Chemistry · 年份：2000 · DOI：10.1074/jbc.m002417200 · 被引用次数：153 · 研究领域：FOXO transcription factor regulation、Pancreatic function and diabetes、Endoplasmic Reticulum Stress and Disease

The Forkhead family transcription factor FKHRL1, a mammalian homolog of DAF16 in the nematode Caenorhabditis elegans, is an inducer of apoptosis in its unphosphorylated form and was recently reported as a substrate of Akt kinases. Insulin-like growth factor (IGF-1) is a potent stimulant of Akt kinase, leading to inhibition of the apoptotic pathway. In this study, we characterized the phosphorylation of FKHRL1 induced by IGF-1 in PC12 cells and various neuronal cell types and examined the potential role of Akt in this regard. IGF-1 rapidly induced the phosphorylation of Akt and FKHRL1 in PC12 cells. The phosphorylation of Akt and FKHRL1 induced by 10 nm IGF-1 was inhibited by the phosphatidylinositide 3-kinase (PI3K) inhibitors wortmannin (0.25-2 microm) and LY294002 (12.5-100 microm), but not by the MEK inhibitor PD98059 (50 microm) or the p70 S6 kinase pathway inhibitor rapamycin (50 nm), suggesting that the phosphorylation of FKHRL1 induced by IGF-1 is mediated by the PI3K pathway. As observed for IGF-1, an in vitro kinase assay with purified active Akt kinase demonstrated that the kinase is capable of directly phosphorylating FKHRL1 at Thr(32) and Ser(253), leading to inhibition of its pro-apoptotic properties. Moreover, transient expression of constitutively active Akt (MS-Akt, where MS is a myristylation signal) increased the phosphorylation of FKHRL1, whereas the expression of kinase-dead Akt (M179A Akt) attenuated the phosphorylation of FKHRL1 induced by 10 nm IGF-1 in...