FoxO regulates expression of decidual protein induced by progesterone (DEPP) in human endothelial cells

Transcriptomic signatures of human single skeletal muscle fibers in response to high-intensity interval exercise

The heterogeneous fiber type composition of skeletal muscle makes it challenging to decipher the molecular signaling events driving the health- and performance benefits of exercise. We developed an optimized workflow for transcriptional profiling of individual human muscle fibers before, immediately after, and after 3 h of recovery from high-intensity interval cycling exercise. From a transcriptional point-of-view, we observe that there is no dichotomy in fiber activation, which could refer to a fiber being recruited or nonrecruited. Rather, the activation pattern displays a continuum with a more uniform response within fast versus slow fibers during the recovery from exercise. The transcriptome-wide response immediately after exercise is characterized by some distinct signatures for slow versus fast fibers, although the most exercise-responsive genes are common between the two fiber types. The temporal transcriptional waves further converge the gene signatures of both fiber types toward a more similar profile during the recovery from exercise. Furthermore, a large heterogeneity among all resting and exercised fibers was observed, with the principal drivers being independent of a slow/fast typology. This profound heterogeneity extends to distinct exercise responses of fibers beyond a classification based on myosin heavy chains. Collectively, our single-fiber methodological approach points to a substantial between-fiber diversity in muscle fiber responses to high-intensity interval exercise.NEW & NOTEWORTHY By development of a single-fiber transcriptomics technology, we assessed the transcriptional events in individual human skeletal muscle fibers upon high-intensity exercise. We demonstrate a large variability in transcriptional activation of fibers, with shared and distinct gene signatures for slow and fast fibers. The heterogeneous fiber-specific exercise response extends beyond this traditional slow/fast categorization. These findings expand on our understanding of exercise responses and uncover a profound between-fiber diversity in muscle fiber activation and transcriptional perturbations.

Endothelial Cell Insulin Signaling Regulates CXCR4 (C-X-C Motif Chemokine Receptor 4) and Limits Leukocyte Adhesion to Endothelium

BACKGROUND

An activated, proinflammatory endothelium is a key feature in the development of complications of obesity and type 2 diabetes and can be caused by insulin resistance in endothelial cells.

METHODS

We analyzed primary human endothelial cells by RNA sequencing to discover novel insulin-regulated genes and used endothelial cell culture and animal models to characterize signaling through CXCR4 (C-X-C motif chemokine receptor 4) in endothelial cells.

RESULTS

CXCR4 was one of the genes most potently regulated by insulin, and this was mediated by PI3K (phosphatidylinositol 3-kinase), likely through FoxO1, which bound to the CXCR4 promoter. CXCR4 mRNA in CD31+ cells was 77% higher in mice with diet-induced obesity compared with lean controls and 37% higher in db/db mice than db/+ controls, consistent with upregulation of CXCR4 in endothelial cell insulin resistance. SDF-1 (stromal cell-derived factor-1)-the ligand for CXCR4-increased leukocyte adhesion to cultured endothelial cells. This effect was lost after deletion of CXCR4 by gene editing while 80% of the increase was prevented by treatment of endothelial cells with insulin. In vivo microscopy of mesenteric venules showed an increase in leukocyte rolling after intravenous injection of SDF-1, but most of this response was prevented in transgenic mice with endothelial overexpression of IRS-1 (insulin receptor substrate-1).

CONCLUSIONS

Endothelial cell insulin signaling limits leukocyte/endothelial cell interaction induced by SDF-1 through downregulation of CXCR4. Improving insulin signaling in endothelial cells or inhibiting endothelial CXCR4 may reduce immune cell recruitment to the vascular wall or tissue parenchyma in insulin resistance and thereby help prevent several vascular complications.

C10orf10/DEPP activates mitochondrial autophagy and maintains chondrocyte viability in the pathogenesis of osteoarthritis

Osteoarthritis (OA), the most prevalent joint disease, is characterized by the progressive loss of articular cartilage. Autophagy, a lysosomal degradation pathway, maintains cellular homeostasis, and autophagic dysfunction in chondrocytes is a hallmark of OA pathogenesis. However, the cause of autophagic dysfunction in OA chondrocytes remains incompletely understood. Recent studies have reported that decidual protein induced by progesterone (C10orf10/DEPP) positively regulates autophagic functions. In this study, we found that DEPP was involved in mitochondrial autophagic functions of chondrocytes, as well as in OA pathogenesis. DEPP expression decreased in human OA chondrocytes in the absence or presence of pro-inflammatory cytokines, and was induced by starvation, hydrogen peroxide (H₂ O₂ ), and hypoxia (cobalt chloride). For functional studies, DEPP knockdown decreased autophagic flux induced by H₂ O₂ , whereas DEPP overexpression increased autophagic flux and maintained cell viability following H₂ O₂ treatment. DEPP was downregulated by knockdown of forkhead box class O (FOXO) transcription factors and modulated the autophagic function regulated by FOXO3. In an OA mouse model by destabilization of the medial meniscus, DEPP-knockout mice exacerbated the progression of cartilage degradation with TUNEL-positive cells, and chondrocytes isolated from knockout mice were decreased autophagic flux and increased cell death following H₂ O₂ treatment. Subcellular fractionation analysis revealed that mitochondria-located DEPP activated mitochondrial autophagy via BCL2 interacting protein 3. Taken together, our data demonstrate that DEPP is a major stress-inducible gene involved in the activation of mitochondrial autophagy in chondrocytes, and maintains chondrocyte viability during OA pathogenesis. DEPP represents a potential therapeutic target for enhancing autophagy in patients with OA.

The Expression of Decidual Protein Induced by Progesterone (DEPP) is Controlled by Three Distal Consensus Hypoxia Responsive Element (HRE) in Hypoxic Retinal Epithelial Cells

Hypoxia affects the development and/or progression of several retinopathies. Decidual protein induced by progesterone (DEPP) has been identified as a hypoxia-responsive gene that may be part of cellular pathways such as autophagy and connected to retinal diseases. To increase our understanding of DEPP regulation in the eye, we defined its expression pattern in mouse and human retina and retinal pigment epithelium (RPE). Interestingly, DEPP expression was increased in an age-dependent way in the central human RPE. We showed that DEPP was regulated by hypoxia in the mouse retina and eyecup and that this regulation was controlled by hypoxia-inducible transcription factors 1 and 2 (HIF1 and HIF2). Furthermore, we identified three hypoxia response elements (HREs) about 3.5 kb proximal to the transcriptional start site that were responsible for hypoxic induction of DEPP in a human RPE cell line. Comparative genomics analysis suggested that one of the three HREs resides in a highly conserved genomic region. Collectively, we defined the molecular elements controlling hypoxic induction of DEPP in an RPE cell line, and provided evidence for an enrichment of DEPP in the aged RPE of human donors. This makes DEPP an interesting gene to study with respect to aging and age-related retinal pathologies.

Forkhead transcription factor FOXO3a mediates interferon-γ-induced MHC II transcription in macrophages

Macrophages are professional antigen-presenting cells relying on the expression of class II major histocompatibility complex (MHC II) genes. Interferon-γ (IFN-γ) activates MHC II transcription via the assembly of an enhanceosome centred on class II trans-activator (CIITA). In the present study, we investigated the role of the forkhead transcription factor FOXO3a in IFN- γ-induced MHC II transcription in macrophages. Knockdown of FOXO3a, but not FOXO1 or FOXO4, diminished IFN-γ-induced MHC II expression in RAW cells. On the contrary, over-expression of FOXO3a, but neither FOXO1 nor FOXO4, enhanced CIITA-mediated trans-activation of the MHC II promoter. IFN-γ treatment promoted the recruitment of FOXO3a to the MHC II promoter. Co-immunoprecipitation and RE-ChIP assays showed that FOXO3a was a component of the MHC II enhanceosome forming interactions with CIITA, RFX5, RFXB and RFXAP. FOXO3a contributed to MHC II transcription by altering histone modifications surrounding the MHC II promoter. Of interest, FOXO3a was recruited to the type IV CIITA promoter and directly activated CIITA transcription by interacting with signal transducer of activation and transcription 1 in response to IFN-γ stimulation. In conclusion, our data unveil a novel role for FOXO3a in the regulation of MHC II transcription in macrophages.

Baicalein induces the apoptosis of HCT116 human colon cancer cells via the upregulation of DEPP/Gadd45a and activation of MAPKs

Baicalein has efficient antitumor properties and has been reported to promote the apoptosis of several human cancer cell lines. Decidual protein induced by progesterone (DEPP), a transcriptional target of Forkhead Box O, was originally identified from the human endometrial stromal cell cDNA library. However, the expression and physiological functions of DEPP in human colon cancer cells remain to be fully elucidated. In the present study, it was reported that baicalein stimulated apoptosis and morphological changes of HCT116, A549 and Panc‑1 cells in a dose-dependent manner. It also upregulated the mRNA and protein levels of DEPP and growth arrest and DNA damage-inducible 45α (Gadd45a). In addition, the overexpression of DEPP promoted mitogen-activated protein kinase (MAPK) phosphorylation. To further investigate the role of DEPP and Gadd45a in baicalein-induced apoptosis, HCT116 cells were transfected with small interfering RNA against either DEPP or Gadd45a as in vitro models. Through an Annexin V/PI double staining assay, it was observed that baicalein-induced apoptosis was impaired by the inactivation of either DEPP or Gadd45a, which in turn restricted the baicalein-induced activation of caspase‑3 and caspase‑9 and phosphorylation of MAPKs. In addition, the inhibition of c‑Jun N‑terminal kinase (JNK)/p38 activity with SP600125/SB203580 decreased the expression of Gadd45a, whereas the inactivation of extracellular signal-regulated kinase with SCH772984 had no effect on the expression of Gadd45a. Taken together, these results demonstrated that baicalein induced the upregulation of DEPP and Gadd45a, which promoted the activation of MAPKs with a positive feedback loop between Gadd45a and JNK/p38, resulting in a marked apoptotic response in human colon cancer cells. These results indicated that baicalein is a potential antitumor drug for the treatment of colon cancer.

DEPP/DEPP1/C10ORF10 regulates hepatic glucose and fat metabolism partly via ROS-induced FGF21

Decidual protein induced by progesterone (DEPP/DEPP1/C10ORF10) is induced by denying access to food and reduced by refeeding in insulin-sensitive organs in vivo. The negative regulation of DEPP by insulin is also proven in several cell lines. However, the functions of DEPP in insulin-sensitive organs remain unknown. In the present study, we investigated the impact of DEPP on hepatic energy metabolism and addressed the underlying mechanisms. The metabolic effects of DEPP were investigated in mice with adenovirus-mediated hepatic overexpression. Liver triglyceride (TG), glycogen, and serum metabolites were detected by biochemical assays. Energy homeostasis was measured by indirect calorimetry. Quantitative PCR was used to examine expression of genes involved in fatty acid oxidation, ketogenesis, lipogenesis, and gluconeogenesis. To evaluate the role of fibroblast growth factor 21 (FGF21) mediating the metabolic effects of DEPP, FGF21 antibody was administrated intraperitoneally to mice at 24 h after the delivery of adenovirus, and the metabolic alterations were examined. Reactive oxygen species (ROS) levels were measured by catalase activity assay, live cell fluorescence, or quantitative PCR. Effects of DEPP on the phenotype of db/db mice were also assessed. Acute hepatic overexpression of DEPP significantly reduced serum glucose and TG levels, dramatically elevated β-hydroxybutyrate levels, and improved glucose clearance. Compared with controls, DEPP overexpression reduced food intake, the energy expenditure rate, and the respiratory quotient. DEPP overexpression significantly increased fatty acid oxidation and ketogenesis but suppressed lipid synthesis and gluconeogenesis. Investigations of the underlying mechanisms revealed that DEPP regulates energy metabolism by inducing oxidative stress. With the impairment of the ROS scavenging system and promotion of ROS formation, DEPP overexpression leads to ROS accumulation. FGF21 is upregulated in response to oxidative stress and mediates the effects of DEPP on fatty acid oxidation, ketogenesis, and lipid synthesis but not gluconeogenesis, as evidenced by the fact that the FGF21 antibody dramatically suppressed a DEPP-induced increase of fatty acid oxidation and ketogenesis, reversed the reduction of lipid synthesis, but did not change the suppression of gluconeogenesis. Moreover, overexpression of DEPP in db/ db mice led to a marked reduction in body weight and serum glucose levels and significantly improved insulin sensitivity. Hepatic overexpression of DEPP in mice promotes fatty acid oxidation and ketogenesis and suppresses lipogenesis and gluconeogenesis, which is partly mediated by FGF21 induced by elevated cellular ROS levels.-Li, W., Ji, M., Lin, Y., Miao, Y., Chen, S., Li, H. DEPP/DEPP1/C10ORF10 regulates hepatic glucose and fat metabolism partly via ROS-induced FGF21.

C10ORF10/DEPP-mediated ROS accumulation is a critical modulator of FOXO3-induced autophagy

Background

Neuroblastoma is the most common solid tumor in childhood and develops from undifferentiated progenitor cells of the sympathetic nervous system. In neuronal tumor cells DNA-damaging chemotherapeutic agents activate the transcription factor FOXO3 which regulates the formation of reactive oxygen species (ROS) and cell death as well as a longevity program associated with therapy resistance.

We demonstrated before that C10ORF10/DEPP, a transcriptional target of FOXO3, localizes to peroxisomes and mitochondria and impairs cellular ROS detoxification. In the present study, we investigated the impact of FOXO3 and DEPP on the regulation of autophagy. Autophagy serves to reduce oxidative damage as it triggers a self-degradative process for the removal of aggregated or misfolded proteins and damaged organelles.

Methods

The effect of FOXO3 and DEPP on autophagy induction was analyzed using live cell fluorescence microscopy and immunoblot analyses of SH-EP cells transfected with a plasmid for EYFP-LC3 and with siRNAs specific for LC3, respectively. ROS steady-state levels were measured with reduced MitoTrackerRed CM-H2XROS. Cellular apoptosis was analyzed by flow cytometry and the caspase 3/7 assay.

Results

We report for the first time that DEPP induces ROS accumulation and thereby mediates the formation of autophagosomes as inhibition of ROS formation by N-acetyl-cysteine completely blocks autophagy. We further demonstrate that H₂O₂-treatment triggers autophagy-induction by FOXO3-mediated DEPP expression. Importantly, knockdown of DEPP was sufficient to efficiently inhibit autophagy-induction under different stress conditions such as serum starvation and genotoxic stress, suggesting that DEPP expression is critical for the initiation of autophagy in neuroblastoma. FOXO3-triggered autophagy partially protects neuroblastoma cells from cell death. Consistent with this concept, we demonstrate that inhibition of autophagy by LC3-knockdown significantly increased etoposide- and doxorubicin-induced apoptosis. These results were also confirmed by the use of the autophagy-inhibitor chloroquine that significantly enhanced the chemotherapeutic effect of etoposide and doxorubicin in neuronal tumor cells.

Conclusion

Targeting FOXO3/DEPP-triggered autophagy is a promising strategy to sensitize neuroblastoma cells to chemotherapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-017-0661-4) contains supplementary material, which is available to authorized users.

Altered gene expression and repressed markers of autophagy in skeletal muscle of insulin resistant patients with type 2 diabetes

This case-control study was designed to investigate the gene expression profile in skeletal muscle from severely insulin resistant patients with long-standing type 2 diabetes (T2D), and to determine associated signaling pathways. Gene expression profiles were examined by whole transcriptome, strand-specific RNA-sequencing and associated signaling was determined by western blot. We identified 117 differentially expressed gene transcripts. Ingenuity Pathway Analysis related these differences to abnormal muscle morphology and mitochondrial dysfunction. Despite a ~5-fold difference in plasma insulin, we did not observe any difference in phosphorylation of AKT or AS160, although other insulin-sensitive cascades, as mTOR/4EBP1, had retained their sensitivity. Autophagy-related gene (ATG14, RB1CC1/FIP200, GABARAPL1, SQSTM1/p62, and WIPI1) and protein (LC3BII, SQSTM1/p62 and ATG5) expression were decreased in skeletal muscle from the patients, and this was associated with a trend to increased phosphorylation of the insulin-sensitive regulatory transcription factor FOXO3a. These data show that gene expression is highly altered and related to mitochondrial dysfunction and abnormal morphology in skeletal muscle from severely insulin resistant patients with T2D, and that this is associated with decreased expression of autophagy-related genes and proteins. We speculate that prolonged treatment with high doses of insulin may suppress autophagy thereby generating a vicious cycle maintaining insulin resistance.

Expression, activation, and role of AKT isoforms in the uterus

The three isoforms of AKT: AKT1, AKT2, and AKT3, are crucial regulators of both normal and pathological cellular processes. Each of these isoforms exhibits a high level of homology and functional redundancy with each other. However, while being highly similar and structurally homologous, a rising amount of evidence is showing that each isoform possesses specific targets as well as preferential subcellular localization. The role of AKT has been studied extensively in reproductive processes, but isoform-specific roles are yet to be fully understood. This review will focus on the role of AKT in the uterus and its function in processes related to cell death and proliferation such as embryo implantation, decidualization, endometriosis, and endometrial cancer in an isoform-centric manner. In this review, we will cover the activation of AKT in various settings, localization of isoforms in subcellular compartments, and the effect of isoform expression on cellular processes. To fully understand the dynamic molecular processes taking place in the uterus, it is crucial that we better understand the physiological role of AKT isoforms as well as their function in the emergence of diseases.

C10ORF10/DEPP, a transcriptional target of FOXO3, regulates ROS-sensitivity in human neuroblastoma

Background

FOXO transcription factors control cellular levels of reactive oxygen species (ROS) which critically contribute to cell survival and cell death in neuroblastoma. In the present study we investigated the regulation of C10orf10/DEPP by the transcription factor FOXO3. As a physiological function of C10orf10/DEPP has not been described so far we analyzed its effects on cellular ROS detoxification and death sensitization in human neuroblastoma cells.

Methods

The effect of DEPP on cellular ROS was measured by catalase activity assay and live cell fluorescence microscopy using the ROS-sensitive dye reduced MitoTracker Red CM-H2XROS. The cellular localization of DEPP was determined by confocal microscopy of EYFP-tagged DEPP, fluorescent peroxisomal- and mitochondrial probes and co-immunoprecipitation of the PEX7 receptor.

Results

We report for the first time that DEPP regulates ROS detoxification and localizes to peroxisomes and mitochondria in neuroblastoma cells. FOXO3-mediated apoptosis involves a biphasic ROS accumulation. Knockdown of DEPP prevented the primary and secondary ROS wave during FOXO3 activation and attenuated FOXO3- and H₂O₂-induced apoptosis. Conditional overexpression of DEPP elevates cellular ROS levels and sensitizes to H₂O₂ and etoposide-induced cell death. In neuronal cells, cellular ROS are mainly detoxified in peroxisomes by the enzyme CAT/catalase. As DEPP contains a peroxisomal-targeting-signal-type-2 (PTS2) sequence at its N-terminus that allows binding to the PEX7 receptor and import into peroxisomes, we analyzed the effect of DEPP on cellular detoxification by measuring enzyme activity of catalase. Catalase activity was reduced in DEPP-overexpressing cells and significantly increased in DEPP-knockdown cells. DEPP directly interacts with the PEX7 receptor and localizes to the peroxisomal compartment. In parallel, the expression of the transcription factor peroxisome proliferator-activated receptor gamma (PPARG), a critical regulator of catalase enzyme activity, was strongly upregulated in DEPP-knockdown cells.

Conclusion

The combined data indicate that in neuroblastoma DEPP localizes to peroxisomes and mitochondria and impairs cellular ROS detoxification, which sensitizes tumor cells to ROS-induced cell death.

Electronic supplementary material

The online version of this article (doi:10.1186/1476-4598-13-224) contains supplementary material, which is available to authorized users.

Decreased expression of C10orf10 and its prognostic significance in human breast cancer

Breast cancer is a common malignant tumor, which severely threatens the health of women with an increasing incidence in many countries. Here, we identified C10orf10 as a novel differentially expression gene using expression microarray screening. The expression analysis indicated that C10orf10 was frequently decreased in human breast cancers compared to noncancerous breast tissues (81/95, P = 0.0063). Kaplan-Meier analysis indicated that patients with low C10orf10 expression showed a poorer prognosis both in mRNA (n = 1115, P = 0.0013) and protein (n = 100, P = 0.003) levels. Univariate and multivariate analysis showed that the C10orf10 expression was an independent prognostic factor for overall survival of breast cancer patients. Further analysis revealed that low expression of C10orf10 was an unfavorable factor for the prognosis of the patients who were luminal A, luminal B, Her2+ subtypes, at histological grade 2, lymph node negative and ER positive. Our data provided the first evidence that C10orf10 expression was frequently decreased in breast cancer tissues, and low expression of C10orf10 may be an important prognostic factor for poorer survival time of breast cancer patients.

FoxO regulates expression of ABCA6, an intracellular ATP-binding-cassette transporter responsive to cholesterol

ATP-binding-cassette (ABC) proteins have been recognized as key players in cellular physiological transport processes. ABC transporter A6 (ABCA6) is a member of the ABC subfamily A. Although it was cloned more than 10 years ago, its expression regulation, subcellular localization, and physiologic function remain largely unknown. We here demonstrated that expression of ABCA6 was Forkhead box O (FoxO)-dependent in human endothelial cell line EA.hy926 and human umbilical vein endothelial cells. Two functional FoxO-responsive elements were identified in ABCA6 promoter and characterized in detail. ABCA6 mRNA was suppressed by insulin-like growth factor-1 which stimulates the phosphorylation and inactivation of FoxOs while inhibitor of phosphatidylinositol 3-kinase had the opposite effect. By immunofluorescence and confocal microscopy, ABCA6 protein is localized primarily in an intracellular compartment, likely representing the Golgi apparatus. ABCA6 mRNA was demonstrated to be responsive to cholesterol loading as well as 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase inhibitors in human endothelial cells. Our data provide evidence for an essential role of FoxO proteins in the transcription of ABCA6 in human vascular endothelial cells. Based on its cholesterol responsiveness, a potential involvement of ABCA6 in intracellular lipid transport processes may be anticipated.