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At least 523 records · Page 29Linked to original sources
PubMed2004

Increased nuclear proteins in muscle satellite cells in aged animals as compared to young growing animals.

Evidence implies that satellite cells could play some limiting role in aged muscle undergoing repair or maintenance of mass, which is of potential clinical concern as this could contribute to sarcopenia. Further, insufficient information is available concerning the cellular mechanisms responsible for the lower rat satellite cell proliferation in old animals. Thus, it was hypothesized that the following proteins would be increased in nuclei of satellite cells from old rat skeletal muscle: the cyclin-dependent kinase (CDK) inhibitors p21(WAF1/CIP1) and p27(Kip1) as well as the transcription factors p53 and Forkhead box, subgroup O1 (FOXO1). In addition, the NAD(+)-dependent histone deacetylase SIRT1, the mammalian ortholog of the yeast SIR2 (silence information regulator 2) and a member of the Sirtuin family, was hypothesized to decrease in satellite cell nuclei of old rats. Old satellite cells (30-months old) exhibited a lesser number of BrdU-positive cells as compared to satellite cells (3-months old) from young growing animals. Western blot analysis demonstrated that nuclei of old satellite cells accumulated the cell cycle inhibitors p21(WAF1/CIP1) and p27(Kip1). In addition, nuclear p53 and FOXO1 proteins were also higher in old satellite cells than in cells from young growing animals. These data indicated both p53/p21(WAF1/CIP1)- and FOXO1/p27(Kip1)-dependent pathways might contribute to the age-associated decrease in satellite cell proliferation. Cytoplasmic manganese superoxide dismutase (MnSOD), a gene driven by FOXO1, was higher in old satellite cells. Unexpectedly, nuclear SIRT1 was also increased in old satellite cells compared with satellite cells from young growing animals. The physiological significance of enhanced nuclear SIRT1 expression in old satellite cells remains elusive at this time. In summary, satellite cells in old rats have nuclear accumulation of proteins inhibiting the cell cycle as compared to young, growing animals.

Aging↗
PubMed2005

Cytokine mediated suppression of TF-1 apoptosis requires PI3K activation and inhibition of Bim expression.

Phosphatidylinositol 3-kinase (PI3K) and its effector protein kinase B (PKB/c-akt) have been implicated as critical mediators of cytokine-induced survival signals. In this study, we have utilized an IL-5 dependent hematopoietic cell line (TF-1) to investigate the signaling events involved in cytokine-dependent erythroblast survival. We demonstrate that IL-5 rescues TF-1 cells from apoptosis through a PI3K/PKB-dependent signaling pathway. Cytokine-withdrawal leads to activation of the Forkhead transcription factor FOXO3a and subsequent expression of the pro-apoptotic Bcl-2 family member Bim. Bim is itself sufficient to induce apoptosis in these cells. Importantly, activation of an inducible active FOXO3a mutant is alone sufficient for upregulation of Bim expression and induction of apoptosis. These data define a mechanism by which survival factors inhibit the default apoptotic pathway and can regulate TF-1 erythroblast survival.

Apoptosis↗
PubMed2006

Blepharophimosis, ptosis, and epicanthus inversus syndrome: clinical and molecular analysis of a case.

Blepharophimosis-ptosis-epicanthus inversus syndrome (OMIM #U10100) is a rare autosomal-dominant disorder in which an eyelid malformation is associated (type I) or not (type H) with premature ovarian failure in the affected female. It is invariably characterized by 4 major features: (1) bilaterally shortened horizontal palpebral fissure (blepharophimosis); (2) severe impairment of the superior palpebral levator (ptosis); (3) a vertical skin fold arising from the lower eyelid, which inserts medially in the upper lid (epicanthus inversus) and (4) an increased inner can-thal distance with a normal outer canthal distance (telecanthus). The mutations causing this disorder are found in the FOXL2 gene, a forkhead transcription factor, located in 3q23. Although many patients with blepharophimosis-ptosis-epicanthus inversus syndrome have an affected parent, a conspicuous number of sporadic cases also have been reported. We describe here a sporadic case with a mutation in the FOXL2 gene that was well characterized both clinically and molecularly.

Adult↗
PubMed2005

Cannabinoid receptor I activation markedly inhibits human decidualization.

The role of cannabinoid receptor I (CBR-1) in the induction of decidualization was examined using decidual fibroblasts and human endometrial stromal cells as model systems. Decidual fibroblasts decidualized in vitro for 3 and 6 days in the presence of the CBR-1 agonist R(+)-WIN 55,212-2 mesylate (WIN, 0.1-10 microM) expressed less of the decidualization-specific markers prolactin, CBR-1, forkhead (FKHR), TIMP-3, laminin, endometrial bleeding associated factor (EBAF), decorin and insulin-like growth factor binding protein-1 (IGFBP-1) mRNA levels compared to control cells. The maximal decrease for each transcript was in the range of 50-99%. In contrast, cells exposed to the CBR-1 inhibitor AM-251 (1 microM) expressed about two-fold higher levels of the decidualization-specific marker gene mRNAs. The WIN-exposed cells showed a marked decrease in intracellular cAMP levels and a progressive, concentration-dependent increase in DNA fragmentation (TUNEL assay) and caspase 3 levels during decidualization compared to control cells. These studies strongly suggest that activation of CBR-1 inhibits human decidualization and stimulates apoptosis by a cAMP-dependent mechanism.

Apoptosis↗
PubMed2004

Regulation of FOXO3a by brain-derived neurotrophic factor in differentiated human SH-SY5Y neuroblastoma cells.

FOXO3a is a ubiquitously expressed mammalian forkhead transcription factor with a high expression level in adult brain. The activity of FOXO3a is inhibited by growth factors through activation of phosphatidylinositol 3-kinase (PI3K)/Akt signaling, which phosphorylates FOXO3a and decreases the level of FOXO3a in the nucleus. In the present study, we examined the regulation of FOXO3a by brain-derived neurotrophic factor (BDNF) in retinoic acid (RA)-differentiated human SH-SY5Y neuroblastoma cells. BDNF caused a rapid and time-dependent decrease of nuclear FOXO3a with a corresponding increase of cytosolic FOXO3a. The rate of the BDNF-induced nuclear/cytosolic redistribution was consistent with the time course of BDNF-induced threonine32-phosphorylation of FOXO3a, and was mediated by the PI3K/Akt signaling pathway. Active FOXO3a rapidly increased the level of Bcl-2-interacting mediator (bim) in differentiated SH-SY5Y cells, and BDNF decreased the FOXO3a-induced increase of bim through activation of both PI3K/Akt and Erk signaling pathways. Thapsigargin, an endoplasmic reticulum (ER) stress-inducing agent, significantly decreased threonine32-phosphorylation of FOXO3a, and increased nuclear and decreased cytosolic FOXO3a, suggesting that thapsigargin activates FOXO3a. Treatment with BDNF completely reversed and blocked the thapsigargin-induced dephosphorylation and nuclear accumulation of FOXO3a. In addition, protein phosphatase 1/2A inhibitors increased threonine32-phosphorylation of FOXO3a, decreased nuclear FOXO3a, and blocked thapsigargin-induced activity of FOXO3a. The regulatory effect of BDNF on FOXO3a and its target genes may play a significant role in the BDNF-mediated neuronal survival, differentiation, and plasticity.

Apoptosis Regulatory Proteins↗
PubMed2004

A novel insertion mutation in the FOXL2 gene is detected in a big Chinese family with blepharophimosis-ptosis-epicanthus inversus.

Blepharophimosis-ptosis-epicanthus inversus syndrome (BPES), an autosomal dominant syndrome in which an eyelid malformation is associated (type I) or not (type II) with premature ovarian failure (POF), has recently been ascribed to mutations in the forkhead transcription factor 2 (FOXL2) gene. In this work, we reveal a novel insertion mutation in the 3'UTR of the FOXL2 gene in a big Chinese family which is to our knowledge the first BPES (type II) family reported in China. It is the first time that a 3'UTR mutation in the FOXL2 gene has ever been found to demonstrate a close correlation between genotype and BPES. Our result gains a greater insight into the function of 3'UTR in the FOXL2 gene.

Base Sequence↗
PubMed2005

Sense and antisense Foxl2 transcripts in mouse.

FOXL2 is a forkhead transcription factor involved in eyelid development and in the development and adult function of the ovary in mammals. In mouse, we have previously suggested the existence of two mRNA isoforms of Foxl2 that result from an alternative polyadenylation. In this study, we characterize in depth the structure and expression of these two variants. We also describe an antisense transcript that overlaps the whole Foxl2 transcription unit. This antisense transcript, called Foxl2OS (for opposite strand), yields several isoforms resulting from alternative splicing. No significant coding region was found in the Foxl2OS sequence. Foxl2OS displays a pattern of expression very similar to that of Foxl2 in the gonads during development and at the adult age. RNA FISH experiments show that both transcripts are expressed in the same cells at the same time. We suggest that Foxl2OS is a noncoding antisense RNA that may be involved in the regulation of Foxl2. All in all our results provide new insights about the organization of the murine Foxl2 locus. This might help us understand its regulation and function.

Alternative Splicing↗
PubMed2006

Analysis of FOXO1A as a candidate gene for type 2 diabetes.

The human forkhead box O1A (FOXO1A) gene on chromosome 13q14.1 is a key transcription factor in insulin signaling in liver and adipose tissue and plays a central role in the regulation of key pancreatic beta-cell genes including IPF1. We hypothesized that sequence variants of FOXO1A contribute to the observed defects in hepatic and peripheral insulin action and altered beta-cell compensation that characterize type 2 diabetes (T2DM). To test this hypothesis, we screened the three exons, 3' untranslated region, and 5' flanking region for sequence variants in Caucasian and African-American individuals with early onset (<45 years) T2DM. We identified only six variants; none altered the coding sequence, and except for one variant in the 3' untranslated region, they were rare or absent in Caucasians. To increase coverage of the gene, we selected seven additional variants in the large first intron and 5' flanking region, thus providing 13 variants that spanned 116.4kb. Based on frequency and linkage disequilibrium patterns in a subset of individuals, we selected eight SNPs to type in a Caucasian population comprising 192 unrelated nondiabetic control individuals and 192 individuals with T2DM, and 10 SNPs to type in 182 controls and 352 diabetic individuals of African-American ancestry. No variant was associated with T2DM (African-Americans, p>0.08; Caucasians, p>0.09). Of the 8 Caucasian SNPs, six comprised a single haplotype block spanning over 100kb and including most of the large first intron. In contrast, no block was observed among SNPs typed in African-Americans. No haplotype was associated with T2DM. FOXO1A variation is rare and is unlikely to contribute to T2DM in either Caucasian or African-American populations.

Black or African American↗
PubMed2006

Foxl2 function in ovarian development.

Foxl2 is a forkhead transcription factor essential for proper reproductive function in females. Human patients carrying mutations in the FOXL2 gene display blepharophimosis/ptosis/epicanthus inversus syndrome (BPES), an autosomal dominant disease associated with eyelid defects and premature ovarian failure in females. Recently, animal models for BPES have been developed that in combination with a catalogue of human FOXL2 mutations provide further insight into its molecular function. Mice homozygous mutant for Foxl2 display craniofacial malformations and female infertility. The analysis of the murine phenotype has revealed that Foxl2 is required for granulosa cell function. These ovarian somatic cells surround and nourish the oocyte and play an important role in follicle formation and activation. Mutations upstream of FOXL2 in humans, not affecting the coding sequence itself, have also been shown to cause BPES, which points to the existence of a distant regulatory element necessary for proper gene expression. The same regulatory sequences may be deleted in the goat polled intersex syndrome (PIS), in which FoxL2 expression is severely reduced. Sequence comparison of FoxL2 from several vertebrate species has shown that it is a highly conserved gene involved in ovary development. Thus, the detailed understanding of Foxl2 function and regulation and the identification of its transcriptional targets may open new avenues for the treatment of female infertility in the future.

Abnormalities, Multiple↗
PubMed2001

Over-expression of FoxM1 stimulates cyclin B1 expression.

FoxM1 (previously named WIN, HFH-11 or Trident) is a Forkhead box (Fox) transcription factor widely expressed in proliferating cells. Various findings, including a recent analysis of FoxM1 knockout mice, suggest that FoxM1 is required for normal S-M coupling during cell cycle progression. To study the regulatory role of FoxM1 and its downstream regulatory targets, three stably transfected HeLa lines that display doxycycline (dox)-inducible FoxM1 expression were established. Over-expression of FoxM1 by dox induction facilitates growth recovery from serum starvation. Quantitation of cyclin B1 and D1 levels using flow cytometric, Western and Northern analyses reveals that elevated FoxM1 levels lead to stimulation of cyclin B1 but not cyclin D1 expression. Transient reporter assays in the dox-inducible lines and upon co-transfection with a constitutive FoxM1 expression plasmid suggest that FoxM1 can activate the cyclin B1 promoter.

Animals↗
PubMed2003

Estrogen regulation of Pak1 and FKHR pathways in breast cancer cells.

Stimulation of p21-activated kinase-1 (Pak1) and estradiol-estrogen receptor-alpha in mammary cancer cells promotes cell survival. We sought to determine whether estrogen stimulates the Pak1 pathway. We found that estrogen rapidly activated Pak1 kinase activity in a phosphatidylinositol 3-kinase-insensitive manner. Furthermore, estrogen induced phosphorylation and perinuclear localization of the cell survival forkhead transcription factor FKHR in the cytoplasm in a Pak1-dependent manner. In addition, Pak1 directly interacted with FKHR and phosphorylated it. The noticed phosphorylation-dependent exclusion of FKHR from the nucleus impaired the ability of FKHR to activate its target Fas ligand promoter containing the FKHR binding motif (FRE) in cells treated with estrogen or expressing catalytically active Pak1. In contrast, expression of the dominant-negative auto-inhibitory domain of Pak1 (Pak amino acids 83-149) promoted the ability of FKHR to activate transcription from FRE. Together, these results identify a novel signaling pathway linking estrogen action to Pak1 signaling, and Pak1 to FKHR, suggesting that Pak1 is an important mediator of estrogen's cell survival functions.

Animals↗
PubMed2004

Activation of protein kinase B (Akt) signaling after electroconvulsive shock in the rat hippocampus.

Akt (protein kinase B, PKB) is one of the major downstream pathways of neurotrophin signaling and plays important roles in the cell survival and synaptic plasticity of the central nervous system. Electroconvulsive shock (ECS) has neurotrophic effect and it affects the synaptic plasticity. It can activate another major pathway of neurotrophin signaling, i.e., Ras-Raf-MEK-Erk cascade. In this paper, the authors investigated whether ECS can activate Akt signaling in the rat hippocampus. After a single ECS, the phosphorylation of Akt was increased, as were the signals detected by phospho-PDK1 substrate antibody, which suggests the activation of PDK1, an upstream molecule of Akt. The phosphorylation of downstream molecules of Akt, forkhead transcription factors (FKHR), endothelial nitric oxide synthase (eNOS), and glycogen synthase kinase-3beta (GSK-3beta) was also increased. The increased phosphorylation of Akt appeared within 5 min of ECS and its time frame paralleled that of the phosphorylation of Erks. Taken together, these results suggest that ECS activates Akt signaling over a similar time scale to that of Erks in the rat hippocampus.

Animals↗
PubMed2003

Characterization of cis-elements mediating the stimulation of glucose-6-phosphate transporter promoter activity by glucocorticoids.

The endoplasmatic glucose-6-phosphate transporter is involved in the control of hepatic glucose production and blood glucose homeostasis. In this study, the expression of a luciferase reporter gene under the control of the glucose-6-phosphate transporter gene promoter was examined in transiently transfected hepatoma cells. The promoter activity was stimulated approximately 2.5-fold by dexamethasone. Mutational analyses demonstrated that the regions nucleotide (nt) -215/-209 and nt -197/-183 relative to the translation start site were critical for this regulation. In gel electrophoretic mobility shift assays the transcription factor Fox O1, also called forkhead in rhabdomyosarcoma (FKHR), overexpressed in 293 cells, bound to a probe with the sequence nt -215/-209. The overexpression of Fox O1 stimulated the induction of glucose-6-phosphate transporter promoter activity by dexamethasone via nt -215/-209 in hepatoma cells. Recombinant glucocorticoid receptor DNA binding domain protein bound to a probe with the sequence of nt -197/-183 in gel electrophoretic mobility shift assays and an oligonucleotide with this sequence transferred glucocorticoid responsiveness to a heterologous promoter. The data indicate that the glucose-6-phosphate transporter promoter contains a glucocorticoid response unit consisting of binding sites for Fox O1 and the glucocorticoid receptor.

Animals↗
PubMed2003

Ceramide-induced neuronal apoptosis is associated with dephosphorylation of Akt, BAD, FKHR, GSK-3beta, and induction of the mitochondrial-dependent intrinsic caspase pathway.

Neuronal apoptosis has been implicated as an important mechanism of cell death in acute and chronic neurodegenerative disorders. Ceramide is a product of sphingolipid metabolism which induces neuronal apoptosis in culture, and ceramide levels increase in neurons during various conditions associated with cell death. In this study we investigate the mechanism of ceramide-induced apoptosis in primary cortical neuronal cells. We show that ceramide treatment initiates a cascade of biochemical alterations associated with cell death: earliest signal transduction changes involve Akt dephosphorylation and inactivation followed by dephosphorylation of proapoptotic regulators such as BAD (proapoptotic Bcl-2 family member), Forkhead family transcription factors, glycogen synthase kinase 3-beta, mitochondrial depolarization and permeabilization, release of cytochrome c into the cytosol, and caspase-3 activation. Bongkrekic acid, an agent that inhibits mitochondrial depolarization, significantly reduces ceramide-induced cell death and correlated caspase-3 activation. Together, these data demonstrate the importance of the mitochondrial-dependent intrinsic pathway of caspase activation for ceramide-induced neuronal apoptosis.

Animals↗
PubMed2001

A fork in the road to fertility.

Haploinsufficiency of FOXL2, a new forkhead transcription factor, causes blepharophimosis/ptosis/epicanthus inversus syndrome (BPES), a rare developmental disorder affecting the eyelid and sometimes the ovary. A new study implicates FOXL2 as the first human gene required for the maintenance of ovarian follicles. The discovery of FOXL2 may provide insight into the causes of idiopathic premature ovarian failure, a disease that burdens many infertile couples.

Blepharophimosis↗
PubMed2003

Insulin-regulated hepatic gluconeogenesis through FOXO1-PGC-1alpha interaction.

Hepatic gluconeogenesis is absolutely required for survival during prolonged fasting or starvation, but is inappropriately activated in diabetes mellitus. Glucocorticoids and glucagon have strong gluconeogenic actions on the liver. In contrast, insulin suppresses hepatic gluconeogenesis. Two components known to have important physiological roles in this process are the forkhead transcription factor FOXO1 (also known as FKHR) and peroxisome proliferative activated receptor-gamma co-activator 1 (PGC-1alpha; also known as PPARGC1), a transcriptional co-activator; whether and how these factors collaborate has not been clear. Using wild-type and mutant alleles of FOXO1, here we show that PGC-1alpha binds and co-activates FOXO1 in a manner inhibited by Akt-mediated phosphorylation. Furthermore, FOXO1 function is required for the robust activation of gluconeogenic gene expression in hepatic cells and in mouse liver by PGC-1alpha. Insulin suppresses gluconeogenesis stimulated by PGC-1alpha but co-expression of a mutant allele of FOXO1 insensitive to insulin completely reverses this suppression in hepatocytes or transgenic mice. We conclude that FOXO1 and PGC-1alpha interact in the execution of a programme of powerful, insulin-regulated gluconeogenesis.

Animals↗
PubMed2004

Foxa2 regulates lipid metabolism and ketogenesis in the liver during fasting and in diabetes.

The regulation of fat and glucose metabolism in the liver is controlled primarily by insulin and glucagon. Changes in the circulating concentrations of these hormones signal fed or starvation states and elicit counter-regulatory responses that maintain normoglycaemia. Here we show that in normal mice, plasma insulin inhibits the forkhead transcription factor Foxa2 by nuclear exclusion and that in the fasted (low insulin) state Foxa2 activates transcriptional programmes of lipid metabolism and ketogenesis. In insulin-resistant or hyperinsulinaemic mice, Foxa2 is inactive and permanently located in the cytoplasm of hepatocytes. In these mice, adenoviral expression of Foxa2T156A, a nuclear, constitutively active Foxa2 that cannot be inhibited by insulin, decreases hepatic triglyceride content, increases hepatic insulin sensitivity, reduces glucose production, normalizes plasma glucose and significantly lowers plasma insulin. These changes are associated with increased expression of genes encoding enzymes of fatty acid oxidation, ketogenesis and glycolysis. Chronic hyperinsulinaemia in insulin-resistant syndromes results in the cytoplasmic localization and inactivation of Foxa2, thereby promoting lipid accumulation and insulin resistance in the liver. Pharmacological intervention to inhibit phosphorylation of Foxa2 may be an effective treatment for type 2 diabetes.

Animals↗
PubMed2005

FoxM1 is required for execution of the mitotic programme and chromosome stability.

Transcriptional induction of cell-cycle regulatory proteins ensures proper timing of subsequent cell-cycle events. Here we show that the Forkhead transcription factor FoxM1 regulates expression of many G2-specific genes and is essential for chromosome stability. Loss of FoxM1 leads to pleiotropic cell-cycle defects, including a delay in G2, chromosome mis-segregation and frequent failure of cytokinesis. We show that transcriptional activation of cyclin B by FoxM1 is essential for timely mitotic entry, whereas CENP-F, another direct target of FoxM1 identified here, is essential for precise functioning of the mitotic spindle checkpoint. Thus, our data uncover a transcriptional cluster regulated by FoxM1 that is essential for proper mitotic progression.

Animals↗