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Insulin-like growth factor-1-induced phosphorylation of transcription factor FKHRL1 is mediated by phosphatidylinositol 3-kinase/Akt kinase and role of this pathway in insulin-like growth factor-1-induced survival of cultured hippocampal neurons.
Mol Pharmacol. 2002 Aug; 62(2):225-33.MP

Abstract

Insulin-like growth factor-1 (IGF-1) is a trophic factor promoting cell survival by activating phosphatidylinositol 3-kinase (PI3K)/Akt kinase pathway. FKHRL1, a member of the Forkhead family of transcription factors possibly involved in cell cycle and apoptosis, is a downstream target of Akt in fibroblasts. However, very little information is available concerning neurons. We report herein that IGF-1 rapidly induced the phosphorylation of endogenous FKHRL1 in hippocampal neurons. The PI3K/Akt kinase pathway mediates this action, as evidenced by the use of different kinase inhibitors, the expression of constitutively active Akt, and in vitro kinase assay. IGF-1 blocked the nuclear translocation of FKHRL1 in hippocampal neurons and promoted survival in parallel to the phosphorylation of Akt and FKHRL1. Similarly, the expression of constitutively active Akt in PC-12 cells increased the phosphorylation of FKHRL1 and promoted survival, whereas the expression of kinase dead Akt attenuated IGF-1-mediated survival of PC-12 cells. Moreover, the overexpression of wild-type FKHRL1 and its nonphosphorylated mutant induced apoptosis in cultured hippocampal neurons. Interestingly, IGF-1 and PI3-kinase inhibitors have no significant effect on the cell cycle inhibitor p27kip1 in hippocampal neurons. This finding suggests that in contrast to fibroblasts, FKHRL1 is unlikely to be involved in cell cycle in neurons. Taken together, these data reveal that endogenous FKHRL1 is a downstream substrate of PI3K/Akt in IGF-1 receptor signaling in hippocampal neurons and suggest that the phosphorylation of this transcription factor may play an important role in the neuronal survival properties of IGF-1.

Authors+Show Affiliations

Department of Psychiatry, Douglas Hospital Research Center, McGill University, Montreal, Quebec, Canada.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

12130673

Citation

Zheng, Wen-Hua, et al. "Insulin-like Growth Factor-1-induced Phosphorylation of Transcription Factor FKHRL1 Is Mediated By Phosphatidylinositol 3-kinase/Akt Kinase and Role of This Pathway in Insulin-like Growth Factor-1-induced Survival of Cultured Hippocampal Neurons." Molecular Pharmacology, vol. 62, no. 2, 2002, pp. 225-33.
Zheng WH, Kar S, Quirion R. Insulin-like growth factor-1-induced phosphorylation of transcription factor FKHRL1 is mediated by phosphatidylinositol 3-kinase/Akt kinase and role of this pathway in insulin-like growth factor-1-induced survival of cultured hippocampal neurons. Mol Pharmacol. 2002;62(2):225-33.
Zheng, W. H., Kar, S., & Quirion, R. (2002). Insulin-like growth factor-1-induced phosphorylation of transcription factor FKHRL1 is mediated by phosphatidylinositol 3-kinase/Akt kinase and role of this pathway in insulin-like growth factor-1-induced survival of cultured hippocampal neurons. Molecular Pharmacology, 62(2), 225-33.
Zheng WH, Kar S, Quirion R. Insulin-like Growth Factor-1-induced Phosphorylation of Transcription Factor FKHRL1 Is Mediated By Phosphatidylinositol 3-kinase/Akt Kinase and Role of This Pathway in Insulin-like Growth Factor-1-induced Survival of Cultured Hippocampal Neurons. Mol Pharmacol. 2002;62(2):225-33. PubMed PMID: 12130673.
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TY - JOUR T1 - Insulin-like growth factor-1-induced phosphorylation of transcription factor FKHRL1 is mediated by phosphatidylinositol 3-kinase/Akt kinase and role of this pathway in insulin-like growth factor-1-induced survival of cultured hippocampal neurons. AU - Zheng,Wen-Hua, AU - Kar,Satyabrata, AU - Quirion,Rémi, PY - 2002/7/20/pubmed PY - 2002/8/6/medline PY - 2002/7/20/entrez SP - 225 EP - 33 JF - Molecular pharmacology JO - Mol Pharmacol VL - 62 IS - 2 N2 - Insulin-like growth factor-1 (IGF-1) is a trophic factor promoting cell survival by activating phosphatidylinositol 3-kinase (PI3K)/Akt kinase pathway. FKHRL1, a member of the Forkhead family of transcription factors possibly involved in cell cycle and apoptosis, is a downstream target of Akt in fibroblasts. However, very little information is available concerning neurons. We report herein that IGF-1 rapidly induced the phosphorylation of endogenous FKHRL1 in hippocampal neurons. The PI3K/Akt kinase pathway mediates this action, as evidenced by the use of different kinase inhibitors, the expression of constitutively active Akt, and in vitro kinase assay. IGF-1 blocked the nuclear translocation of FKHRL1 in hippocampal neurons and promoted survival in parallel to the phosphorylation of Akt and FKHRL1. Similarly, the expression of constitutively active Akt in PC-12 cells increased the phosphorylation of FKHRL1 and promoted survival, whereas the expression of kinase dead Akt attenuated IGF-1-mediated survival of PC-12 cells. Moreover, the overexpression of wild-type FKHRL1 and its nonphosphorylated mutant induced apoptosis in cultured hippocampal neurons. Interestingly, IGF-1 and PI3-kinase inhibitors have no significant effect on the cell cycle inhibitor p27kip1 in hippocampal neurons. This finding suggests that in contrast to fibroblasts, FKHRL1 is unlikely to be involved in cell cycle in neurons. Taken together, these data reveal that endogenous FKHRL1 is a downstream substrate of PI3K/Akt in IGF-1 receptor signaling in hippocampal neurons and suggest that the phosphorylation of this transcription factor may play an important role in the neuronal survival properties of IGF-1. SN - 0026-895X UR - https://www.unboundmedicine.com/medline/citation/12130673/Insulin_like_growth_factor_1_induced_phosphorylation_of_transcription_factor_FKHRL1_is_mediated_by_phosphatidylinositol_3_kinase/Akt_kinase_and_role_of_this_pathway_in_insulin_like_growth_factor_1_induced_survival_of_cultured_hippocampal_neurons_ L2 - http://molpharm.aspetjournals.org/cgi/pmidlookup?view=long&pmid=12130673 DB - PRIME DP - Unbound Medicine ER -