The Experts below are selected from a list of 27291 Experts worldwide ranked by ideXlab platform
Ronald A Depinho - One of the best experts on this subject based on the ideXlab platform.
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foxo function is essential for maintenance of autophagic flux and neuronal morphogenesis in adult neurogenesis
Neuron, 2018Co-Authors: Iris Schaffner, Georgia Minakaki, Amir M Khan, Elli Anna Balta, Ursula Schlotzerschrehardt, Tobias J Schwarz, Ruth Beckervordersandforth, Beate Winner, Ashley E Webb, Ronald A DepinhoAbstract:Autophagy is a conserved catabolic pathway with emerging functions in mammalian neurodevelopment and human neurodevelopmental diseases. The mechanisms controlling autophagy in neuronal development are not fully understood. Here, we found that conditional deletion of the Forkhead Box O transcription factors FoxO1, FoxO3, and FOXO4 strongly impaired autophagic flux in developing neurons of the adult mouse hippocampus. Moreover, FoxO deficiency led to altered dendritic morphology, increased spine density, and aberrant spine positioning in adult-generated neurons. Strikingly, pharmacological induction of autophagy was sufficient to correct abnormal dendrite and spine development of FoxO-deficient neurons. Collectively, these findings reveal a novel link between FoxO transcription factors, autophagic flux, and maturation of developing neurons.
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hepatic suppression of foxo1 and foxo3 causes hypoglycemia and hyperlipidemia in mice
Endocrinology, 2012Co-Authors: Kebin Zhang, Ronald A Depinho, Ling Li, Yajuan Qi, Travis AverittAbstract:Dysregulation of blood glucose and triglycerides are the major characteristics of type 2 diabetes mellitus. We sought to identify the mechanisms regulating blood glucose and lipid homeostasis. Cell-based studies established that the Foxo forkhead transcription factors Forkhead box O (Foxo)-1, Foxo3, and FOXO4 are inactivated by insulin via a phosphatidylinositol 3-kinase/Akt-dependent pathway, but the role of Foxo transcription factors in the liver in regulating nutrient metabolism is incompletely understood. In this study, we used the Cre/LoxP genetic approach to delete the Foxo1, Foxo3, and FOXO4 genes individually or a combination of two or all in the liver of lean or db/db mice and assessed the role of Foxo inactivation in regulating glucose and lipid homeostasis in vivo. In the lean mice or db/db mice, hepatic deletion of Foxo1, rather than Foxo3 or FOXO4, caused a modest reduction in blood glucose concentrations and barely affected lipid homeostasis. Combined deletion of Foxo1 and Foxo3 decreased bl...
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hepatic suppression of foxo1 and foxo3 causes hypoglycemia and hyperlipidemia in mice
Endocrinology, 2012Co-Authors: Kebin Zhang, Ronald A Depinho, Travis Averitt, Xiaoping Zhu, Boyi Gan, Shaodong GuoAbstract:Dysregulation of blood glucose and triglycerides are the major characteristics of type 2 diabetes mellitus. We sought to identify the mechanisms regulating blood glucose and lipid homeostasis. Cell-based studies established that the Foxo forkhead transcription factors Forkhead box O (Foxo)-1, Foxo3, and FOXO4 are inactivated by insulin via a phosphatidylinositol 3-kinase/Akt-dependent pathway, but the role of Foxo transcription factors in the liver in regulating nutrient metabolism is incompletely understood. In this study, we used the Cre/LoxP genetic approach to delete the Foxo1, Foxo3, and FOXO4 genes individually or a combination of two or all in the liver of lean or db/db mice and assessed the role of Foxo inactivation in regulating glucose and lipid homeostasis in vivo. In the lean mice or db/db mice, hepatic deletion of Foxo1, rather than Foxo3 or FOXO4, caused a modest reduction in blood glucose concentrations and barely affected lipid homeostasis. Combined deletion of Foxo1 and Foxo3 decreased blood glucose levels, elevated serum triglyceride and cholesterol concentrations, and increased hepatic lipid secretion and caused hepatosteatosis. Analysis of the liver transcripts established a prominent role of Foxo1 in regulating gene expression of gluconeogenic enzymes and Foxo3 in the expression of lipogenic enzymes. Our findings indicate that Foxo1 and Foxo3 inactivation serves as a potential mechanism by which insulin reduces hepatic glucose production and increases hepatic lipid synthesis and secretion in healthy and diabetic states.
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hepatic foxos regulate lipid metabolism via modulation of expression of the nicotinamide phosphoribosyltransferase gene
Journal of Biological Chemistry, 2011Co-Authors: Rongya Tao, Ronald A Depinho, Dan Wei, Hanlin Gao, Yunlong Liu, Charlie X DongAbstract:FoxO transcription factors have been implicated in lipid metabolism; however, the underlying mechanisms are not well understood. Here, in an effort to elucidate such mechanisms, we examined the phenotypic consequences of liver-specific deletion of three members of the FoxO family: FoxO1, FoxO3, and FOXO4. These liver-specific triply null mice, designated LTKO, exhibited elevated triglycerides in the liver on regular chow diet. More remarkably, LTKO mice developed severe hepatic steatosis following placement on a high fat diet. Further analyses revealed that hepatic NAD+ levels and Sirt1 activity were decreased in the liver of the LTKO mice relative to controls. At the mechanistic level, expression profile analyses showed that LTKO livers had significantly down-regulated expression of the nicotinamide phosphoribosyltransferase (Nampt) gene encoding the rate-limiting enzyme in the salvage pathway of NAD+ biosynthesis. Luciferase reporter assays and chromatin immunoprecipitation analyses demonstrated that Nampt is a transcriptional target gene of FoxOs. Significantly, overexpression of Nampt gene reduced, whereas knockdown increased, hepatic triglyceride levels in vitro and in vivo. Thus, FoxOs control the Nampt gene expression and the NAD+ signaling in the regulation of hepatic triglyceride homeostasis.
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foxo transcription factors promote cardiomyocyte survival upon induction of oxidative stress
Journal of Biological Chemistry, 2011Co-Authors: Arunima Sengupta, Ronald A Depinho, Jihye Paik, Jeffery D Molkentin, Katherine E YutzeyAbstract:Transcriptional regulatory mechanisms of cardiac oxidative stress resistance are not well defined. FoxO transcription factors are critical mediators of oxidative stress resistance in multiple cell types, but cardioprotective functions have not been reported previously. FoxO function in oxidative stress resistance was investigated in cultured cardiomyocytes and in mice with cardiomyocyte-specific combined deficiency of FoxO1 and FoxO3 subjected to myocardial infarction (MI) or acute ischemia/reperfusion (I/R) injury. Induction of oxidative stress in cardiomyocytes promotes FoxO1 and FoxO3 nuclear localization and target gene activation. Infection of cardiomyocytes with a dominant-negative FoxO1(Δ256) adenovirus results in a significant increase in reactive oxygen species and cell death, whereas increased FoxO1 or FoxO3 expression reduces reactive oxygen species and cell death. Mice generated with combined conditional deletion of FoxO1 and FoxO3 specifically in cardiomyocytes were subjected to I/R or MI. Loss of FoxO1 and FoxO3 in cardiomyocytes results in a significant increase in infarct area with decreased expression of the antiapoptotic molecules, PTEN-induced kinase1 (PINK1) and CBP/P300-interacting transactivator (CITED2). Expressions of the antioxidants catalase and manganese superoxide dismutase-2 (SOD2) and the autophagy-related proteins LC3II and Gabarapl1 also are decreased following I/R compared with controls. Mice with cardiomyocyte-specific FoxO deficiency subjected to MI have reduced cardiac function, increased scar formation, induction of stress-responsive signaling, and increased apoptotic cell death relative to controls. These data support a critical role for FoxOs in promoting cardiomyocyte survival during conditions of oxidative stress through induction of antioxidants and cell survival pathways.
Tomas Obsil - One of the best experts on this subject based on the ideXlab platform.
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forkhead domains of foxo transcription factors differ in both overall conformation and dynamics
Cells, 2019Co-Authors: Tomas Obsil, Veronika Obsilova, Katarina Psenakova, Klara Kohoutova, Michael J Ausserlechner, Vaclav VeverkaAbstract:FOXO transcription factors regulate cellular homeostasis, longevity and response to stress. FOXO1 (also known as FKHR) is a key regulator of hepatic glucose production and lipid metabolism, and its specific inhibition may have beneficial effects on diabetic hyperglycemia by reducing hepatic glucose production. Moreover, all FOXO proteins are considered potential drug targets for drug resistance prevention in cancer therapy. However, the development of specific FOXO inhibitors requires a detailed understanding of structural differences between individual FOXO DNA-binding domains. The high-resolution structure of the DNA-binding domain of FOXO1 reported in this study and its comparison with structures of other FOXO proteins revealed differences in both their conformation and flexibility. These differences are encoded by variations in protein sequences and account for the distinct functions of FOXO proteins. In particular, the positions of the helices H1, H2 and H3, whose interface form the hydrophobic core of the Forkhead domain, and the interactions between hydrophobic residues located on the interface between the N-terminal segment, the H2-H3 loop, and the recognition helix H3 differ among apo FOXO1, FOXO3 and FOXO4 proteins. Therefore, the availability of apo structures of DNA-binding domains of all three major FOXO proteins will support the development of FOXO-type-specific inhibitors.
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structure of the human FOXO4 dbd dna complex at 1 9 a resolution reveals new details of foxo binding to the dna
Acta Crystallographica Section D-biological Crystallography, 2010Co-Authors: Evzen Boura, Tomas Obsil, Veronika Obsilova, Lenka Rezabkova, Jiri BryndaAbstract:FOXO4 is a member of the FOXO subgroup of forkhead transcription factors that constitute key components of a conserved signalling pathway that connects growth and stress signals to transcriptional control. Here, the 1.9 A resolution crystal structure of the DNA-binding domain of human FOXO4 (FOXO4-DBD) bound to a 13 bp DNA duplex containing a FOXO consensus binding sequence is reported. The structure shows a similar recognition of the core sequence as has been shown for two other FOXO proteins. Helix H3 is docked into the major groove and provides all of the base-specific contacts, while the N-terminus and wing W1 make additional contacts with the phosphate groups of DNA. In contrast to other FOXO-DBD–DNA structures, the loop between helices H2 and H3 has a different conformation and participates in DNA binding. In addition, the structure of the FOXO4-DBD–DNA complex suggests that both direct water–DNA base contacts and the unique water-network interactions contribute to FOXO-DBD binding to the DNA in a sequence-specific manner.
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14 3 3 protein masks the dna binding interface of forkhead transcription factor FOXO4
Journal of Biological Chemistry, 2009Co-Authors: Jan Silhan, Petr Herman, Veronika Obsilova, Jaroslav Vecer, Jan Teisinger, Petr Vacha, Pavla Strnadova, M Sulc, Tomas ObsilAbstract:The role of 14-3-3 proteins in the regulation of FOXO forkhead transcription factors is at least 2-fold. First, the 14-3-3 binding inhibits the interaction between the FOXO and the target DNA. Second, the 14-3-3 proteins prevent nuclear reimport of FOXO factors by masking their nuclear localization signal. The exact mechanisms of these processes are still unclear, mainly due to the lack of structural data. In this work, we used fluorescence spectroscopy to investigate the mechanism of the 14-3-3 protein-dependent inhibition of FOXO4 DNA-binding properties. Time-resolved fluorescence measurements revealed that the 14-3-3 binding affects fluorescence properties of 5-(((acetylamino)ethyl)amino) naphthalene-1-sulfonic acid moiety attached at four sites within the forkhead domain of FOXO4 that represent important parts of the DNA binding interface. Observed changes in 5-(((acetylamino)ethyl)amino) naphthalene-1-sulfonic acid fluorescence strongly suggest physical contacts between the 14-3-3 protein and labeled parts of the FOXO4 DNA binding interface. The 14-3-3 protein binding, however, does not cause any dramatic conformational change of FOXO4 as documented by the results of tryptophan fluorescence experiments. To build a realistic model of the FOXO4·14-3-3 complex, we measured six distances between 14-3-3 and FOXO4 using Forster resonance energy transfer time-resolved fluorescence experiments. The model of the complex suggests that the forkhead domain of FOXO4 is docked within the central channel of the 14-3-3 protein dimer, consistent with our hypothesis that 14-3-3 masks the DNA binding interface of FOXO4.
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14-3-3 Protein interacts with nuclear localization sequence of forkhead transcription factor FOXO4.
Biochemistry, 2005Co-Authors: Veronika Obsilova, Petr Herman, Jaroslav Vecer, Anna Pabianova, Miroslav Sulc, Jan Teisinger, Evzen Boura, Tomas ObsilAbstract:The 14-3-3 proteins are a family of regulatory signaling molecules that interact with other proteins in a phosphorylation-dependent manner. 14-3-3 proteins are thought to play a direct role in the regulation of subcellular localization of FoxO forkhead transcription factors. It has been suggested that the interaction with the 14-3-3 protein affects FoxO binding to the target DNA and interferes with the function of nuclear localization sequence (NLS). Masking or obscuring of NLS could inhibit interaction between FoxO factors and nuclear importing machinery and thus shift the equilibrium of FoxO localization toward the cytoplasm. According to our best knowledge, there is no experimental evidence showing a direct interaction between the 14-3-3 protein and NLS of FoxO. Therefore, the main goal of this work was to investigate whether the phosphorylation by protein kinase B, the 14-3-3 protein, and DNA binding affect the structure of FOXO4 NLS. We have used site-directed labeling of FOXO4 NLS with the extrinsic fluorophore 1,5-IAEDANS in conjunction with steady-state and time-resolved fluorescence spectroscopy to study conformational changes of FOXO4 NLS in vitro. Our data show that the 14-3-3 protein binding significantly changes the environment around AEDANS-labeled NLS and reduces its flexibility. On the other hand, the phosphorylation itself and the binding of double-stranded DNA have a small effect on the structure of this region. Our results also suggest that the DNA-binding domain of FOXO4 remains relatively mobile while bound to the 14-3-3 protein.
Katherine E Yutzey - One of the best experts on this subject based on the ideXlab platform.
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foxo1 and foxm1 transcription factors have antagonistic functions in neonatal cardiomyocyte cell cycle withdrawal and igf1 gene regulation
Circulation Research, 2013Co-Authors: Arunima Sengupta, Vladimir V Kalinichenko, Katherine E YutzeyAbstract:Rationale: In the mammalian heart, cardiomyocytes withdraw from the cell cycle and initiate hypertrophic growth soon after birth, but the transcriptional regulatory mechanisms that control these neonatal transitions are not well-defined. Objective: Forkhead family transcription factors have been implicated as positive (forkhead box [Fox] transcription factor M1) and negative (FoxO1 and FoxO3) regulators of cardiomyocyte proliferation prenatally, but their regulatory interactions and functions in neonatal cell-cycle withdrawal have not been reported previously. Potential regulators of Fox activity, including the metabolic indicator AMP-activated protein kinase (AMPK), and Fox transcriptional targets ( p21 , p27 , insulin-like growth factor 1 [ IGF1 ]) also were examined. Methods and Results: In cultured neonatal rat cardiomyocytes, AMPK activates FoxOs, and AMPK inhibition is sufficient to induce cell proliferation. In vivo, combined loss of FoxO1 and FoxO3 specifically in cardiomyocytes leads to delayed cell-cycle withdrawal and increased expression of IGF1 and FoxM1 . Conversely, cardiomyocyte-specific loss of FoxM1 results in decreased neonatal cardiomyocyte cell proliferation, decreased expression of IGF1 , and increased expression of cell-cycle inhibitors p21 and p27 . IGF1 is a direct downstream target of cardiac Fox transcription factors, which is negatively regulated by FoxOs and positively regulated by FoxM1, dependent on AMPK activation status. Conclusions: These data support a regulatory mechanism whereby the balance of FoxO and FoxM1 transcription factors integrates metabolic status, mediated by AMPK, and cell-cycle regulation, through competitive regulation of target genes, including IGF1 , in neonatal cardiomyocytes.
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foxo transcription factors promote cardiomyocyte survival upon induction of oxidative stress
Journal of Biological Chemistry, 2011Co-Authors: Arunima Sengupta, Ronald A Depinho, Jihye Paik, Jeffery D Molkentin, Katherine E YutzeyAbstract:Transcriptional regulatory mechanisms of cardiac oxidative stress resistance are not well defined. FoxO transcription factors are critical mediators of oxidative stress resistance in multiple cell types, but cardioprotective functions have not been reported previously. FoxO function in oxidative stress resistance was investigated in cultured cardiomyocytes and in mice with cardiomyocyte-specific combined deficiency of FoxO1 and FoxO3 subjected to myocardial infarction (MI) or acute ischemia/reperfusion (I/R) injury. Induction of oxidative stress in cardiomyocytes promotes FoxO1 and FoxO3 nuclear localization and target gene activation. Infection of cardiomyocytes with a dominant-negative FoxO1(Δ256) adenovirus results in a significant increase in reactive oxygen species and cell death, whereas increased FoxO1 or FoxO3 expression reduces reactive oxygen species and cell death. Mice generated with combined conditional deletion of FoxO1 and FoxO3 specifically in cardiomyocytes were subjected to I/R or MI. Loss of FoxO1 and FoxO3 in cardiomyocytes results in a significant increase in infarct area with decreased expression of the antiapoptotic molecules, PTEN-induced kinase1 (PINK1) and CBP/P300-interacting transactivator (CITED2). Expressions of the antioxidants catalase and manganese superoxide dismutase-2 (SOD2) and the autophagy-related proteins LC3II and Gabarapl1 also are decreased following I/R compared with controls. Mice with cardiomyocyte-specific FoxO deficiency subjected to MI have reduced cardiac function, increased scar formation, induction of stress-responsive signaling, and increased apoptotic cell death relative to controls. These data support a critical role for FoxOs in promoting cardiomyocyte survival during conditions of oxidative stress through induction of antioxidants and cell survival pathways.
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foxo transcription factors promote autophagy in cardiomyocytes
Journal of Biological Chemistry, 2009Co-Authors: Arunima Sengupta, Jeffery D Molkentin, Katherine E YutzeyAbstract:In the heart, autophagy is required for normal cardiac function and also has been implicated in cardiovascular disease. FoxO transcription factors promote autophagy in skeletal muscle and have additional roles in regulation of cell size, proliferation, and metabolism. Here we investigate the role of FoxO transcription factors in regulating autophagy and cell size in cardiomyocytes. In cultured rat neonatal cardiomyocytes, glucose deprivation leads to decreased cell size and induction of autophagy pathway genes LC3, Gabarapl1, and Atg12. Likewise, overexpression of either FoxO1 or FoxO3 reduces cardiomyocyte cell size and induces expression of autophagy pathway genes. Moreover, inhibition of FoxO activity by dominant negative FoxO1 (Δ256) blocks cardiomyocyte cell size reduction upon starvation, suggesting the necessity of FoxO function in cardiomyocyte cell size regulation. Under starvation conditions, endogenous FoxO1 and FoxO3 are localized to the nucleus and bind to promoter sequences of Gabarapl1 and Atg12. In vivo studies show that cellular stress, such as starvation or ischemia/reperfusion in mice, results in induction of autophagy in the heart with concomitant dephosphorylation of FoxO, consistent with increased activity of nuclear FoxO transcription factors. Together these results provide evidence for an important role for FoxO1 and FoxO3 in regulating autophagy and cell size in cardiomyocytes.
Jihye Paik - One of the best experts on this subject based on the ideXlab platform.
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foxo transcription factors promote cardiomyocyte survival upon induction of oxidative stress
Journal of Biological Chemistry, 2011Co-Authors: Arunima Sengupta, Ronald A Depinho, Jihye Paik, Jeffery D Molkentin, Katherine E YutzeyAbstract:Transcriptional regulatory mechanisms of cardiac oxidative stress resistance are not well defined. FoxO transcription factors are critical mediators of oxidative stress resistance in multiple cell types, but cardioprotective functions have not been reported previously. FoxO function in oxidative stress resistance was investigated in cultured cardiomyocytes and in mice with cardiomyocyte-specific combined deficiency of FoxO1 and FoxO3 subjected to myocardial infarction (MI) or acute ischemia/reperfusion (I/R) injury. Induction of oxidative stress in cardiomyocytes promotes FoxO1 and FoxO3 nuclear localization and target gene activation. Infection of cardiomyocytes with a dominant-negative FoxO1(Δ256) adenovirus results in a significant increase in reactive oxygen species and cell death, whereas increased FoxO1 or FoxO3 expression reduces reactive oxygen species and cell death. Mice generated with combined conditional deletion of FoxO1 and FoxO3 specifically in cardiomyocytes were subjected to I/R or MI. Loss of FoxO1 and FoxO3 in cardiomyocytes results in a significant increase in infarct area with decreased expression of the antiapoptotic molecules, PTEN-induced kinase1 (PINK1) and CBP/P300-interacting transactivator (CITED2). Expressions of the antioxidants catalase and manganese superoxide dismutase-2 (SOD2) and the autophagy-related proteins LC3II and Gabarapl1 also are decreased following I/R compared with controls. Mice with cardiomyocyte-specific FoxO deficiency subjected to MI have reduced cardiac function, increased scar formation, induction of stress-responsive signaling, and increased apoptotic cell death relative to controls. These data support a critical role for FoxOs in promoting cardiomyocyte survival during conditions of oxidative stress through induction of antioxidants and cell survival pathways.
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foxo proteins cooperatively control the differentiation of foxp3 regulatory t cells
Nature Immunology, 2010Co-Authors: Weiming Ouyang, Jihye Paik, Omar Beckett, Ronald A DepinhoAbstract:CD4(+) regulatory T cells (T(reg) cells) characterized by expression of the transcription factor Foxp3 have a pivotal role in maintaining immunological tolerance. Here we show that mice with T cell-specific deletion of both the Foxo1 and Foxo3 transcription factors (collectively called 'Foxo proteins' here) developed a fatal multifocal inflammatory disorder due in part to T(reg) cell defects. Foxo proteins functioned in a T(reg) cell-intrinsic manner to regulate thymic and transforming growth factor-beta (TGF-beta)-induced Foxp3 expression, in line with the ability of Foxo proteins to bind to Foxp3 locus and control Foxp3 promoter activity. Transcriptome analyses showed that Foxo proteins regulated the expression of additional T(reg) cell-associated genes and were essential for inhibiting the acquisition of effector T cell characteristics by T(reg) cells. Thus, Foxo proteins have crucial roles in specifying the T(reg) cell lineage.
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foxo mediated defense against oxidative stress in osteoblasts is indispensable for skeletal homeostasis in mice
Cell Metabolism, 2010Co-Authors: Elena Ambrogini, Ronald A Depinho, Jihye Paik, Maria Almeida, Marta Martinmillan, Li Han, Joseph J Goellner, Robert S Weinstein, Robert L Jilka, Charles A ObrienAbstract:Aging increases oxidative stress and osteoblast apoptosis and decreases bone mass, whereas forkhead box O (FoxO) transcription factors defend against oxidative stress by activating genes involved in free radical scavenging and apoptosis. Conditional deletion of FoxO1, FoxO3, and FOXO4 in 3-month-old mice resulted in an increase in oxidative stress in bone and osteoblast apoptosis and a decrease in the number of osteoblasts, the rate of bone formation, and bone mass at cancellous and cortical sites. The effect of the deletion on osteoblast apoptosis was cell autonomous and resulted from oxidative stress. Conversely, overexpression of a FoxO3 transgene in mature osteoblasts decreased oxidative stress and osteoblast apoptosis and increased osteoblast number, bone formation rate, and vertebral bone mass. We conclude that FoxO-dependent oxidative defense provides a mechanism to handle the oxygen free radicals constantly generated by the aerobic metabolism of osteoblasts and is thereby indispensable for bone mass homeostasis.
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forkhead box class o transcription factors in brain regulation and behavioral manifestation
Biological Psychiatry, 2009Co-Authors: Abigail M Polter, Ronald A Depinho, Jihye Paik, Sufen Yang, Anna A Zmijewska, Thomas Van Groen, Stanford L Peng, Richard S JopeAbstract:Background The mammalian forkhead box, class O (FoxO) transcription factors function to regulate diverse physiological processes. Emerging evidence that both brain-derived neurotrophic factor (BDNF) and lithium suppress FoxO activity suggests a potential role of FoxOs in regulating mood-relevant behavior. Here, we investigated whether brain FoxO1 and FoxO3a can be regulated by serotonin and antidepressant treatment and whether their genetic deletion affects behaviors. Methods C57BL/6 mice were treated with d-fenfluramine to increase brain serotonergic activity or with the antidepressant imipramine. The functional status of brain FoxO1 and FoxO3a was audited by immunoblot analysis for phosphorylation and subcellular localization. The behavioral manifestations in FoxO1- and FoxO3a-deficient mice were assessed via the Elevated Plus Maze Test, Forced Swim Test, Tail Suspension Test, and Open Field Test. Results Increasing serotonergic activity by d-fenfluramine strongly increased phosphorylation of FoxO1 and FoxO3a in several brain regions and reduced nuclear FoxO1 and FoxO3a. The effect of d-fenfluramine was mediated by the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway. Chronic, but not acute, treatment with the antidepressant imipramine also increased the phosphorylation of brain FoxO1 and FoxO3a. When FoxO1 was selectively deleted from brain, mice displayed reduced anxiety. In contrast, FoxO3a-deficient mice presented with a significant antidepressant-like behavior. Conclusions FoxOs may be a transcriptional target for anxiety and mood disorder treatment. Despite their physical and functional relatedness, FoxO1 and FoxO3a influence distinct behavioral processes linked to anxiety and depression. Findings in this study reveal important new roles of FoxOs in brain and provide a molecular framework for further investigation of how FoxOs may govern mood and anxiety disorders.
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forkhead transcription factors foxos promote apoptosis of insulin resistant macrophages during cholesterol induced endoplasmic reticulum stress
Diabetes, 2008Co-Authors: Takafumi Senokuchi, Chien Ping Liang, Michihiro Matsumoto, Domenico Accili, Ronald A Depinho, Jihye Paik, Ira Tabas, Alexander S. Banks, Tracie A Seimon, Alan R TallAbstract:OBJECTIVE— Endoplasmic reticulum stress increases macrophage apoptosis, contributing to the complications of atherosclerosis. Insulin-resistant macrophages are more susceptible to endoplasmic reticulum stress–associated apoptosis probably contributing to macrophage death and necrotic core formation in atherosclerotic plaques in type 2 diabetes. However, the molecular mechanisms of increased apoptosis in insulin-resistant macrophages remain unclear. RESEARCH DESIGN AND METHODS— The studies were performed in insulin-resistant macrophages isolated from insulin receptor knockout or ob/ob mice. Gain- or loss-of-function approaches were used to evaluate the roles of forkhead transcription factors (FoxOs) in endoplasmic reticulum stress–associated macrophage apoptosis. RESULTS— Insulin-resistant macrophages showed attenuated Akt activation and increased nuclear localization of FoxO1 during endoplasmic reticulum stress induced by free cholesterol loading. Overexpression of active FoxO1 or FoxO3 failed to induce apoptosis in unchallenged macrophages but exacerbated apoptosis in macrophages with an active endoplasmic reticulum stress response. Conversely, macrophages with genetic knockouts of FoxO1, -3, and -4 were resistant to apoptosis in response to endoplasmic reticulum stress. FoxO1 was shown by chromatin immunoprecipitation and promoter expression analysis to induce inhibitor of κBe gene expression and thereby to attenuate the increase of nuclear p65 and nuclear factor-κB activity during endoplasmic reticulum stress, with proapoptotic and anti-inflammatory consequences. CONCLUSIONS— Decreased Akt and increased FoxO transcription factor activity during the endoplasmic reticulum stress response leads to increased apoptosis of insulin-resistant macrophages. FoxOs may have a dual cellular function, resulting in either proapoptotic or anti-inflammatory effects in an endoplasmic reticulum stress–modulated manner. In the complex plaque milieu, the ultimate effect is likely to be an increase in macrophage apoptosis, plaque inflammation, and destabilization.
Boudewijn M T Burgering - One of the best experts on this subject based on the ideXlab platform.
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activation of forkhead box o transcription factors by oncogenic braf promotes p21cip1 dependent senescence
Cancer Research, 2010Co-Authors: Peter L. J. De Keizer, Arjan B. Brenkman, Niels J. F. Van Den Broek, Leisl M Packer, Anna A Szypowska, Paulien E Riedlpolderman, Alain De Bruin, Tobias B Dansen, Richard Marais, Boudewijn M T BurgeringAbstract:Oncogene-induced senescence (OIS) is a potent tumor-suppressive mechanism that is thought to come at the cost of aging. The Forkhead box O (FOXO) transcription factors are regulators of life span and tumor suppression. However, whether and how FOXOs function in OIS have been unclear. Here, we show a role for FOXO4 in mediating senescence by the human BRAFV600E oncogene, which arises commonly in melanoma. BRAFV600E signaling through mitogen-activated protein kinase/extracellular signal-regulated kinase kinase resulted in increased reactive oxygen species levels and c-Jun NH 2 terminal kinase-mediated activation of FOXO4 via its phosphorylation on Thr223, Ser226, Thr447, and Thr451. BRAFV600E-induced FOXO4 phosphorylation resulted in p21cip1-mediated cell senescence independent of p16 ink4a or p27kip1. Importantly, melanocyte-specific activation of BRAFV600E in vivo resulted in the formation of skin nevi expressing Thr223/Ser226-phosphorylated FOXO4 and elevated p21cip1. Together, these findings support a model in which FOXOs mediate a trade-off between cancer and aging.
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The DNA damage repair protein Ku70 interacts with FOXO4 to coordinate a conserved cellular stress response
FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 2010Co-Authors: Arjan B. Brenkman, Niels J. F. Van Den Broek, Peter L. J. De Keizer, Dik C. Van Gent, Boudewijn M T BurgeringAbstract:In this study, we searched for proteins regulating the tumor suppressor and life-span regulator FOXO4. Through an unbiased tandem-affinity purification strategy combined with mass spectrometry, we identified the heterodimer Ku70/Ku80 (Ku), a DNA double-strand break repair component. Using biochemical interaction studies, we found Ku70 to be necessary and sufficient for the interaction. FOXO4 mediates its tumor-suppressive function in part through transcriptional regulation of the cell cycle arrest p27(kip1) gene. Immunoblotting, luciferase reporter assays, and flow cytometry showed that Ku70 inhibited FOXO4-mediated p27(kip1) transcription and cell cycle arrest induction by >40%. In contrast, Ku70 RNAi but not control RNAi significantly increased p27(kip1) transcription. In addition, in contrast to wild-type mouse embryonic stem (ES) cells, Ku70(-/-) ES cells showed significantly increased FOXO activity, which was rescued by Ku70 reexpression. Immunofluorescence studies demonstrated that Ku70 sequestered FOXO4 in the nucleus. Interestingly, the Ku70-FOXO4 interaction stoichiometry followed a nonlinear dose-response curve by hydrogen peroxide-generated oxidative stress. Low levels of oxidative stress increased interaction stoichiometry up to 75%, peaking at 50 μM, after which dissociation occurred. Because the Ku70 ortholog in the roundworm Caenorhabditis elegans was shown to regulate life span involving C. elegans FOXO, our findings suggest a conserved critical Ku70 role for FOXO function toward coordination of a survival program, regulated by the magnitude of oxidative damage.
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mdm2 induces mono ubiquitination of FOXO4
PLOS ONE, 2008Co-Authors: Arjan B. Brenkman, Niels J. F. Van Den Broek, Peter L. J. De Keizer, A G Jochemsen, Boudewijn M T BurgeringAbstract:Background The Forkhead box O (FOXO) class of transcription factors are involved in the regulation of several cellular responses including cell cycle progression and apoptosis. Furthermore, in model organisms FOXOs act as tumor suppressors and affect aging. Previously, we noted that FOXOs and p53 are remarkably similar within their spectrum of regulatory proteins [1]. For example, the de-ubiquitinating enzyme USP7 removes ubiquitin from both FOXO and p53. However, Skp2 has been identified as E3 ligase for FOXO1, whereas Mdm2 is the prime E3 ligase for p53. Principal Findings/Methodology Here we provide evidence that Mdm2 acts as an E3 ligase for FOXO as well. In vitro incubation of Mdm2 and FOXO results in ATP-dependent (multi)mono-ubiquitination of FOXO similar to p53. Furthermore, in vivo co-expression of Mdm2 and FOXO induces FOXO mono-ubiquitination and consistent with this result, siRNA-mediated depletion of Mdm2 inhibits mono-ubiquitination of FOXO induced by hydrogen peroxide. Regulation of FOXO ubiquitination by Mdm2 is likely to be direct since Mdm2 and FOXO co-immunoprecipitate. In addition, Mdm2-mediated ubiquitination regulates FOXO transcriptional activity. Conclusions/Significance These data identify Mdm2 as a novel E3 ligase for FOXOs and extend the analogous mode of regulation between FOXO and p53.
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foxo transcription factor activation by oxidative stress mediated by the small gtpase ral and jnk
The EMBO Journal, 2004Co-Authors: Marieke A G Essers, Sanne Weijzen, Ingrid Saarloos, Nancy D De Ruiter, Alida M M De Vriessmits, Boudewijn M T BurgeringAbstract:Forkhead transcription factors of the FOXO class are negatively regulated by PKB/c-Akt in response to insulin/IGF signalling, and are involved in regulating cell cycle progression and cell death. Here we show that, in contrast to insulin signalling, low levels of oxidative stress generated by treatment with H2O2 induce the activation of FOXO4. Upon treatment of cells with H2O2, the small GTPase Ral is activated and this results in a JNK-dependent phosphorylation of FOXO4 on threonine 447 and threonine 451. This Ral-mediated, JNK-dependent phosphorylation is involved in the nuclear translocation and transcriptional activation of FOXO4 after H2O2 treatment. In addition, we show that this signalling pathway is also employed by tumor necrosis factor α to activate FOXO4 transcriptional activity. FOXO members have been implicated in cellular protection against oxidative stress via the transcriptional regulation of manganese superoxide dismutase and catalase gene expression. The results reported here, therefore, outline a homeostasis mechanism for sustaining cellular reactive oxygen species that is controlled by signalling pathways that can convey both negative (PI-3K/PKB) and positive (Ras/Ral) inputs.
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cell cycle and death control long live forkheads
Trends in Biochemical Sciences, 2002Co-Authors: Boudewijn M T Burgering, Geert J P L KopsAbstract:The FOXO family of Forkhead transcription factors, FKHR (FOXO1), FKHR-L1 (FOXO3a) and AFX (FOXO4), are regulated by the phosphoinositide-3-kinase-protein-kinase-B (PI3K-PKB/c-Akt) pathway. Direct phosphorylation by PKB results in cytoplasmic retention and inactivation, inhibiting the expression of FOXO-regulated genes, which control the cell cycle, cell death, cell metabolism and oxidative stress. This pathway appears to be well conserved throughout evolution. In the nematode Caenorhabditis elegans, it affects lifespan and controls dauer formation. Recent discoveries about FOXO regulation by PI3K-PKB signalling suggest that the PI3K-PKB-FOXO pathway might participate in similar processes in higher eukaryotes.
