The Experts below are selected from a list of 75 Experts worldwide ranked by ideXlab platform
Remi Quirion - One of the best experts on this subject based on the ideXlab platform.
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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
Molecular Pharmacology, 2002Co-Authors: Wenhua Zheng, S Kar, Remi QuirionAbstract: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.
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insulin like growth Factor 1 induced phosphorylation of the forkhead family Transcription Factor FKHRL1 is mediated by akt kinase in pc12 cells
Journal of Biological Chemistry, 2000Co-Authors: Wenhua Zheng, S Kar, Remi QuirionAbstract: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 PC12 cells. Interestingly, FKHRL1 co-immunoprecipitated with Akt in PC12 cells, indicating that these two proteins can associate in these cells. As IGF-1 also induced the phosphorylation of FKHRL1 in primary cortical and cerebellar neuronal cultures, these data, taken together, demonstrate that IGF-1, acting via the PI3K/Akt kinase pathway, can regulate the phosphorylation of FKHRL1, leading to inhibition of this apoptotic Transcription Factor in neuronal cells.
Wenhua Zheng - One of the best experts on this subject based on the ideXlab platform.
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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
Molecular Pharmacology, 2002Co-Authors: Wenhua Zheng, S Kar, Remi QuirionAbstract: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.
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insulin like growth Factor 1 induced phosphorylation of the forkhead family Transcription Factor FKHRL1 is mediated by akt kinase in pc12 cells
Journal of Biological Chemistry, 2000Co-Authors: Wenhua Zheng, S Kar, Remi QuirionAbstract: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 PC12 cells. Interestingly, FKHRL1 co-immunoprecipitated with Akt in PC12 cells, indicating that these two proteins can associate in these cells. As IGF-1 also induced the phosphorylation of FKHRL1 in primary cortical and cerebellar neuronal cultures, these data, taken together, demonstrate that IGF-1, acting via the PI3K/Akt kinase pathway, can regulate the phosphorylation of FKHRL1, leading to inhibition of this apoptotic Transcription Factor in neuronal cells.
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insulin like growth Factor 1 igf 1 a neuroprotective trophic Factor acting via the akt kinase pathway
Journal of Neural Transmission-supplement, 2000Co-Authors: Wenhua Zheng, Sylvain Dore, R QuirionAbstract:Insulin-like growth Factor-I (IGF-I) is a pleiotropic polypeptide with a wide range of actions in both central and peripheral nervous sytems. Over the past few years, we studied the trophic as well as neuromodulatory roles of IGF-I in the brain. Accumulated evidence indicates that IGF-I, apart from regulating growth and development, protects neurons against cell death induced by amyloidogenic derivatives, glucose or serum deprivation via the activation of intracellular pathways implicating phosphatidylinositide 3/Akt kinase, winged-helix family of Transcription Factor FKHRL1 phosphorylation or production of free radicals. The effects of IGF-I on neuroprotection, glucose metabolism and activity-dependent plasticity suggest the potential usefulness of this growth Factor or related mimetics in the treatment of Alzheimer’s disease and other neurodegenerative disorders.
Thomas Dschietzig - One of the best experts on this subject based on the ideXlab platform.
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Relaxin Protects Rat Lungs from Ischemia-Reperfusion Injury via Inducible NO Synthase: Role of ERK-1/2, PI3K, and Forkhead Transcription Factor FKHRL1
PloS one, 2013Co-Authors: Konstantin Alexiou, Manuel Wilbring, Klaus Matschke, Thomas DschietzigAbstract:Introduction Early allograft dysfunction following lung transplantation is mainly an ischemia/reperfusion (IR) injury. We showed that relaxin-2 (relaxin) exerts a protective effect in lung IR, attributable to decreases in endothelin-1 (ET-1) production, leukocyte recruitment, and free radical generation. Here, we summarize our investigations into relaxin’s signalling. Materials and Methods Isolated rat lungs were perfused with vehicle or 5 nM relaxin (n = 6–10 each). Thereafter, experiments were conducted in the presence of relaxin plus vehicle, the protein kinase A inhibitors H-89 and KT-5720, the NO synthase (NOS) inhibitor L-NAME, the iNOS inhibitor 1400W, the nNOS inhibitor SMTC, the extracellular signal-regulated kinase-1/2 (ERK-1/2) inhibitor PD-98059, the phosphatidylinositol-3 kinase (PI3K) inhibitor wortmannin, the endothelin type-B (ETB) antagonist A-192621, or the glucocorticoid receptor (GR) antagonist RU-486. After 90 min ischemia and 90 min reperfusion we determined wet-to-dry (W/D) weight ratio, mean pulmonary arterial pressure (MPAP), vascular release of ET-1, neutrophil elastase (NE), myeloperoxidase (MPO), and malondialdehyde (MDA). Primary rat pulmonary vascular cells were similarly treated. Results IR lungs displayed significantly elevated W/D ratios, MPAP, as well as ET-1, NE, MDA, and MPO. In the presence of relaxin, all of these parameters were markedly improved. This protective effect was completely abolished by L-NAME, 1400W, PD-98059, and wortmannin whereas neither PKA and nNOS inhibition nor ETB and GR antagonism were effective. Analysis of NOS gene expression and activity revealed that the relaxin-induced early and moderate iNOS stimulation is ERK-1/2-dependent and counter-balanced by PI3K. Relaxin-PI3K-related phosphorylation of a forkhead Transcription Factor, FKHRL1, paralleled this regulation. In pulmonary endothelial and smooth muscle cells, FKHRL1 was essential to relaxin-PI3K signalling towards iNOS. Conclusion In this short-time experimental setting, relaxin protects against IR-induced lung injury via early and moderate iNOS induction, dependent on balanced ERK-1/2 and PI3K-FKHRL1 stimulation. These findings render relaxin a candidate drug for lung preservation.
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Relaxin, via PI3K, phosphorylates FKHRL-1.
2013Co-Authors: Konstantin Alexiou, Manuel Wilbring, Klaus Matschke, Thomas DschietzigAbstract:Isolated rat lungs perfused with buffer in recirculatory mode were processed at baseline, after 90(n = 6 each) in order to determine protein expression (panel A) and Ser-253 phosphorylation (panel B) of the forkhead Transcription Factor, FKHRL1. Experiments were carried out in the presence of vehicle (control), 5 nM of relaxin, the ERK-1/2 inhibitor PD-98059 (PD) (50 µmol/l), the PI3K inhibitor wortmannin (WM) (100 nM), and combinations thereof. (A) Representative Western blot from lung homogenates produced after ischemia. (B) Quantification of Western blot data (n = 6 per group). Relaxin causes FKHRL-1 phosphorylation during ischemia in a PI3K (wortmannin)-dependent fashion; there is no dependence of ERK-1/2. P
Norio Komatsu - One of the best experts on this subject based on the ideXlab platform.
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a member of forkhead Transcription Factor FKHRL1 is a downstream effector of sti571 induced cell cycle arrest in bcr abl expressing cells
Journal of Biological Chemistry, 2003Co-Authors: Norio Komatsu, Tomoko Watanabe, Mie Uchida, Masaki Mori, Keita Kirito, Satoru Kikuchi, Qifa Liu, Tetsuzo Tauchi, Keisuke Miyazawa, Hitoshi EndoAbstract:A member of the Forkhead Transcription Factor family, FKHRL1, lies downstream of the phosphatidylinositol 3-kinase-Akt activation pathway in cytokine signaling. Because the phosphatidylinositol 3-kinase-Akt activation pathway is required for BCR-ABL-mediated transformation and survival signaling in chronic myelogenous leukemia (CML), in this study we examined the involvement of FKHRL1 in the BCR-ABL-mediated signaling pathway. FKHRL1 was constitutively phosphorylated in BCR-ABL-expressing cell lines KCL22 and KU812, and its phosphorylation was inhibited by treatment with STI571, a specific inhibitor of BCR-ABL tyrosine kinase. Concomitantly, STI571 induced cell cycle arrest at the G(0)/G(1) phase, accompanied by up-regulation of a cyclin-dependent kinase inhibitor p27/Kip1 in KCL22 cells. In addition, FKHRL1 was constitutively phosphorylated in the TF-1/bcr-abl cell line ectopically expressing BCR-ABL but not in the parent TF-1 cell line. Considering several lines of evidence that phosphorylated FKHRL1 has lost Transcriptional activity and that p27/Kip1 expression is positively regulated by dephosphorylated "active" FKHRL1, BCR-ABL may down-regulate p27/Kip1 expression via the loss of FKHRL1 function as a Transcription Factor. To demonstrate this hypothesis, we generated a tamoxifen-inducible "active FKHRL1" FKHRL1-TM (a triple mutant of FKHRL1, in which all three Akt phosphorylation sites have been mutated), estrogen receptor system in the KCL22 cell line. The addition of tamoxifen inhibited the cell growth indicating that overexpression of FKHRL1 in the nucleus antagonized deregulated proliferation of CML cells. Collectively, FKHRL1 regulates the expression of p27/Kip1 as a downstream molecule of BCR-ABL signaling in CML cells. BCR-ABL-induced loss of FKHRL1 function may be involved in oncogenic transformation of CML partially via the down-regulation of p27/Kip1 proteins.
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Forkhead Family Transcription Factor FKHRL1 Is Expressed in Human Megakaryocytes REGULATION OF CELL CYCLING AS A DOWNSTREAM MOLECULE OF THROMBOPOIETIN SIGNALING
The Journal of biological chemistry, 2001Co-Authors: Masaru Tanaka, Tomoko Watanabe, Mie Uchida, Keita Kirito, Hitoshi Endo, Yoshifumi Kashii, Tomoyuki Endoh, Ken-ichi Sawada, Keiya Ozawa, Norio KomatsuAbstract:Abstract FKHRL1, a member of the Forkhead Transcription Factor family, is one of the downstream molecules of phosphatidylinositol 3-kinase-Akt. This molecule is a mammalian homolog of DAF-16, which plays an important role in the longevity ofCaenorhabditis elegans. In this study we found that Akt and FKHRL1 proteins were detectable in highly purified normal human megakaryocytes and that these molecules were actually phosphorylated by thrombopoietin (TPO). To clarify the functional role of FKHRL1 in TPO signaling, we established a tetracycline-inducible system in the human TPO-dependent leukemia cell line UT-7/TPO. Induced expression of active FKHRL1 led to cell cycle arrest at G0/G1 phase in this cell line. These results suggest that FKHRL1 plays an important role in the cell cycle of megakaryocytic cells as one of the downstream target molecules of phosphatidylinositol 3-kinase-Akt, presumably mediated through the activation or inactivation of cell cycle-associated gene(s).
Hitoshi Endo - One of the best experts on this subject based on the ideXlab platform.
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a member of forkhead Transcription Factor FKHRL1 is a downstream effector of sti571 induced cell cycle arrest in bcr abl expressing cells
Journal of Biological Chemistry, 2003Co-Authors: Norio Komatsu, Tomoko Watanabe, Mie Uchida, Masaki Mori, Keita Kirito, Satoru Kikuchi, Qifa Liu, Tetsuzo Tauchi, Keisuke Miyazawa, Hitoshi EndoAbstract:A member of the Forkhead Transcription Factor family, FKHRL1, lies downstream of the phosphatidylinositol 3-kinase-Akt activation pathway in cytokine signaling. Because the phosphatidylinositol 3-kinase-Akt activation pathway is required for BCR-ABL-mediated transformation and survival signaling in chronic myelogenous leukemia (CML), in this study we examined the involvement of FKHRL1 in the BCR-ABL-mediated signaling pathway. FKHRL1 was constitutively phosphorylated in BCR-ABL-expressing cell lines KCL22 and KU812, and its phosphorylation was inhibited by treatment with STI571, a specific inhibitor of BCR-ABL tyrosine kinase. Concomitantly, STI571 induced cell cycle arrest at the G(0)/G(1) phase, accompanied by up-regulation of a cyclin-dependent kinase inhibitor p27/Kip1 in KCL22 cells. In addition, FKHRL1 was constitutively phosphorylated in the TF-1/bcr-abl cell line ectopically expressing BCR-ABL but not in the parent TF-1 cell line. Considering several lines of evidence that phosphorylated FKHRL1 has lost Transcriptional activity and that p27/Kip1 expression is positively regulated by dephosphorylated "active" FKHRL1, BCR-ABL may down-regulate p27/Kip1 expression via the loss of FKHRL1 function as a Transcription Factor. To demonstrate this hypothesis, we generated a tamoxifen-inducible "active FKHRL1" FKHRL1-TM (a triple mutant of FKHRL1, in which all three Akt phosphorylation sites have been mutated), estrogen receptor system in the KCL22 cell line. The addition of tamoxifen inhibited the cell growth indicating that overexpression of FKHRL1 in the nucleus antagonized deregulated proliferation of CML cells. Collectively, FKHRL1 regulates the expression of p27/Kip1 as a downstream molecule of BCR-ABL signaling in CML cells. BCR-ABL-induced loss of FKHRL1 function may be involved in oncogenic transformation of CML partially via the down-regulation of p27/Kip1 proteins.
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Forkhead Family Transcription Factor FKHRL1 Is Expressed in Human Megakaryocytes REGULATION OF CELL CYCLING AS A DOWNSTREAM MOLECULE OF THROMBOPOIETIN SIGNALING
The Journal of biological chemistry, 2001Co-Authors: Masaru Tanaka, Tomoko Watanabe, Mie Uchida, Keita Kirito, Hitoshi Endo, Yoshifumi Kashii, Tomoyuki Endoh, Ken-ichi Sawada, Keiya Ozawa, Norio KomatsuAbstract:Abstract FKHRL1, a member of the Forkhead Transcription Factor family, is one of the downstream molecules of phosphatidylinositol 3-kinase-Akt. This molecule is a mammalian homolog of DAF-16, which plays an important role in the longevity ofCaenorhabditis elegans. In this study we found that Akt and FKHRL1 proteins were detectable in highly purified normal human megakaryocytes and that these molecules were actually phosphorylated by thrombopoietin (TPO). To clarify the functional role of FKHRL1 in TPO signaling, we established a tetracycline-inducible system in the human TPO-dependent leukemia cell line UT-7/TPO. Induced expression of active FKHRL1 led to cell cycle arrest at G0/G1 phase in this cell line. These results suggest that FKHRL1 plays an important role in the cell cycle of megakaryocytic cells as one of the downstream target molecules of phosphatidylinositol 3-kinase-Akt, presumably mediated through the activation or inactivation of cell cycle-associated gene(s).