Arginine methylation of FOXO transcription factors inhibits their phosphorylation by Akt

Overcoming EZH2 Inhibitor Resistance by Taxane in PTEN-Mutated Cancer

Rationale: The Polycomb group (PcG) protein EZH2 is implicated in cancer progression due to its frequent overexpression in many cancer types and therefore is a promising therapeutic target. Forkhead box transcription factor-1 (FOXO1) is a tumor suppressor that is often transcriptionally downregulated in human cancers such as prostate cancer although the underlying regulatory mechanisms remain elusive.

Methods: Analysis of EZH2 ChIP-seq and ChIP-on-chip data in various cell types was performed. ChIP-qPCR, RT-qPCR, and western blot analyses were conducted to determine the mechanism by which EZH2 represses FOXO1 expression. Immunohistochemistry was employed to assess the correlation between EZH2 and FOXO1 protein expression in prostate cancer patient specimens. In vitro MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) and animal experiments were performed to determine the anti-cancer efficacy of EZH2 inhibitor alone or in combination of docetaxel, a chemotherapy agent of the taxane family, and dependency of the efficacy on FOXO1 expression.

Results: We demonstrated that EZH2 binds to the FOXO1 gene promoter. EZH2 represses FOXO1 gene expression at the transcriptional level. EZH2 protein level inversely correlated with FOXO1 protein expression in prostate cancer patient specimens. This repression requires the methyltransferase activity and the functional PRC2 complex. While effectively inducing loss of viability of PTEN-positive 22Rv1 prostate cancer cells, EZH2 inhibitor failed to inhibit growth of PTEN-negative C4-2 prostate cancer cells. Co-treatment with docetaxel overcame EZH2 inhibitor resistance in PTEN-negative cancer cells in vitro and in mice. This effect was largely mediated by docetaxel-induced nuclear localization and activation of FOXO1.

Conclusions: This study identifies FOXO1 as a bona fide repression target of EZH2 and an essential mediator of EZH2 inhibition-induced cell death. Our findings suggest that EZH2 repression of FOXO1 can be targeted by EZH2 inhibitor as a monotherapy for PTEN-proficient cancers or in combination with taxane for treatment of cancers with PTEN mutation or deletion.

Hepatocyte PRMT1 protects from alcohol induced liver injury by modulating oxidative stress responses

Protein Arginine methyltransferase 1 (PRMT1) is the main enzyme of cellular arginine methylation. Previously we found that PRMT1 activity in the liver is altered after alcohol exposure resulting in epigenetic changes. To determine the impact of these PRMT1 changes on the liver's response to alcohol, we induced a hepatocyte specific PRMT1 knockout using AAV mediated Cre delivery in mice fed either alcohol or control Lieber-DeCarli liquid diet. We found that in alcohol fed mice, PRMT1 prevents oxidative stress and promotes hepatocyte survival. PRMT1 knockout in alcohol fed mice resulted in a dramatic increase in hepatocyte death, inflammation and fibrosis. Additionally, we found that alcohol promotes PRMT1 dephosphorylation at S297. Phosphorylation at this site is necessary for PRMT1-dependent protein arginine methylation. PRMT1 S297A, a dephosphorylation mimic of PRMT1 had reduced ability to promote gene expression of pro-inflammatory cytokines, pro-apoptotic genes BIM and TRAIL and expression of a suppressor of hepatocyte proliferation, Hnf4α. On the other hand, several functions of PRMT1 were phosphorylation-independent, including expression of oxidative stress response genes, Sod1, Sod2 and others. In vitro, both wild type and S297A PRMT1 protected hepatocytes from oxidative stress induced apoptosis, however S297D phosphorylation mimic PRMT1 promoted cell death. Taken together these data suggest that PRMT1 is an essential factor of liver adaptation to alcohol; alcohol-induced dephosphorylation shifts PRMT1 toward a less pro-inflammatory, more pro-proliferative and pro-survival form.

Roles of forkhead box O (FoxO) transcription factors in neurodegenerative diseases: A panoramic view

Neurodegenerative diseases (NDDs), which are among the most important aging-related diseases, are typically characterized by neuronal damage and a progressive impairment in neurological function during aging. Few effective therapeutic targets for NDDs have been revealed; thus, an understanding of the pathogenesis of NDDs is important. Forkhead box O (FoxO) transcription factors have been implicated in the mechanisms regulating aging and longevity. The functions of FoxOs are regulated by diverse post-translational modifications (e.g., phosphorylation, acetylation, ubiquitination, methylation and glycosylation). FoxOs exert both detrimental and protective effects on NDDs. Therefore, an understanding of the precise function of FoxOs in NDDs will be helpful for developing appropriate treatment strategies. In this review, we first introduce the post-translational modifications of FoxOs. Next, the regulation of FoxO expression and post-translational modifications in the central nervous system (CNS) is described. Afterwards, we analyze and address the important roles of FoxOs in NDDs. Finally, novel potential directions of future FoxO research in NDDs are discussed. This review recapitulates essential facts and questions about the promise of FoxOs in treating NDDs, and it will likely be important for the design of further basic studies and to realize the potential for FoxOs as therapeutic targets in NDDs.

hnRNPK S379 phosphorylation participates in migration regulation of triple negative MDA-MB-231 cells

We have previously identified a novel Aurora-A-mediated Serine 379 (S379) phosphorylation of a poly(C)-binding protein, hnRNPK, the overexpression of which is frequently observed in various cancers. It is known that the oncogenic Aurora-A kinase promotes the malignancy of cancer cells. This study aims to investigate the unexplored functions of hnRNPK S379 phosphorylation using MDA-MB-231 cells, a triple negative breast cancer cell that has amplification of the Aurora-A kinase gene. Accordingly, we established two cell lines in which the endogenous hnRNPK was replaced with either S379D or S379A hnRNPK respectively. Notably, we found that a phosphorylation-mimic S379D mutant of hnRNPK suppressed cell migration and, conversely, a phosphorylation-defective S379A mutant promoted migration. Moreover, Twist was downregulated upon hnRNPK S379 phosphorylation, whereas β-catenin and MMP12 were increased when there was loss of hnRNPK S379 phosphorylation in MDA-MB-231 cells. Furthermore, S379A hnRNPK increases stability of β-catenin in MDA-MB-231 cells. In conclusion, our results suggest that hnRNPK S379 phosphorylation regulates migration via the EMT signaling pathway.

Metabolism in Immune Cell Differentiation and Function

The immune system is a central determinant of organismal health. Functional immune responses require quiescent immune cells to rapidly grow, proliferate, and acquire effector functions when they sense infectious agents or other insults. Specialized metabolic programs are critical regulators of immune responses, and alterations in immune metabolism can cause immunological disorders. There has thus been growing interest in understanding how metabolic processes control immune cell functions under normal and pathophysiological conditions. In this chapter, we summarize how metabolic programs are tuned and what the physiological consequences of metabolic reprogramming are as they relate to immune cell homeostasis, differentiation, and function.

Methylation of C/EBPα by PRMT1 Inhibits Its Tumor-Suppressive Function in Breast Cancer

C/EBPα is an essential transcription factor involved in regulating the expression or function of certain cell-cycle regulators, including in breast cancer cells. Although protein arginine methyltransferases have been shown to play oncogenic roles in a variety of cancers, little is known about the role of arginine methylation in regulating the antiproliferation activity of C/EBPα. Here, we report that the protein arginine methyltransferase 1 (PRMT1) is overexpressed in human breast cancer and that elevated PRMT1 correlates with cancer malignancy. RNA-sequencing analysis revealed that knockdown of PRMT1 in breast cancer cells is accompanied by a decrease in the expression of pro-proliferative genes, including cyclin D1. Furthermore, tandem affinity purification followed by mass spectrometry identified PRMT1 as a component of the C/EBPα complex. C/EBPα associated with and was methylated by PRMT1 at three arginine residues (R35, R156, and R165). PRMT1-dependent methylation of C/EBPα promoted the expression of cyclin D1 by blocking the interaction between C/EBPα and its corepressor HDAC3, which resulted in rapid growth of tumor cells during the pathogenesis of breast cancer. Inhibition of PRMT1 significantly impeded the growth of cancer cells from patients with triple-negative breast cancer. This evidence that PRMT1 mediates C/EBPα methylation sheds light on a novel pathway and potential therapeutic target in breast cancer. SIGNIFICANCE: This study provides novel mechanistic insight of the role of the arginine methyltransferase PRMT1 in breast cancer pathogenesis.

Thioredoxin-1 improves the immunometabolic phenotype of antitumor T cells

Adoptive transfer of tumor epitope-reactive T cells has emerged as a promising strategy to control tumor growth. However, chronically-stimulated T cells expanded for adoptive cell transfer are susceptible to cell death in an oxidative tumor microenvironment. Because oxidation of cell-surface thiols also alters protein functionality, we hypothesized that increasing the levels of thioredoxin (Trx), an antioxidant molecule facilitating reduction of proteins through cysteine thiol-disulfide exchange, in T cells will promote their sustained antitumor function. Using pre-melanosome protein (Pmel)-Trx1 transgenic mouse-derived splenic T cells, flow cytometry, and gene expression analysis, we observed here that higher Trx expression inversely correlated with reactive oxygen species and susceptibility to T-cell receptor restimulation or oxidation-mediated cell death. These Trx1-overexpressing T cells exhibited a cluster of differentiation 62L^hi (CD62L^hi) central memory-like phenotype with reduced glucose uptake (2-NBDG^lo) and decreased effector function (interferon γ^lo). Furthermore, culturing tumor-reactive T cells in the presence of recombinant Trx increased the dependence of T cells on mitochondrial metabolism and improved tumor control. We conclude that strategies for increasing the antioxidant capacity of antitumor T cells modulate their immunometabolic phenotype leading to improved immunotherapeutic control of established tumors.

Molecular mechanisms of FOXO1 in adipocyte differentiation

Forkhead box-O1 (FOXO1) is a downstream target of AKT and plays crucial roles in cell cycle control, apoptosis, metabolism and adipocyte differentiation. It is thought that FOXO1 affects adipocyte differentiation by regulating lipogenesis and cell cycle. With the deepening in the understanding of this field, it is currently believed that FOXO1 translocation between nuclei and cytoplasm is involved in the regulation of FOXO1 activity, thus affecting adipocyte differentiation. Translocation of FOXO1 depends on its post-translational modifications and interactions with 14-3-3. Based on these modifications and interactions, FOXO1 could regulate lipogenesis through PPARγ and the adipocyte cell cycle through p21 and p27. In this review, we aim to provide a comprehensive FOXO1 regulation network in adipocyte differentiation by linking together distinct functions mentioned above to explain their effects on adipocyte differentiation and to emphasize the regulatory role of FOXO1. In addition, we also focus on the novel findings such as the use of miRNAs in FOXO1 regulation and highlight the improvable issues, such as RNA modifications, for future research in the field.

PTEN arginine methylation by PRMT6 suppresses PI3K-AKT signaling and modulates pre-mRNA splicing

Arginine methylation is a ubiquitous posttranslational modification that regulates critical cellular processes including signal transduction and pre-mRNA splicing. Here, we report that the tumor-suppressor PTEN is methylated by protein arginine methyltransferase 6 (PRMT6). Mass-spectrometry analysis reveals that PTEN is dimethylated at arginine 159 (R159). We found that PTEN is mutated at R159 in cancers, and the PTEN mutant R159K loses its capability to inhibit the PI3K-AKT cascade. Furthermore, PRMT6 is physically associated with PTEN, promotes asymmetrical dimethylation of PTEN, and regulates the PI3K-AKT cascade through PTEN R159 methylation. In addition, using transcriptome analyses, we found that PTEN R159 methylation is involved in modulation of pre-mRNA alternative splicing. Our results demonstrate that PTEN is functionally regulated by arginine methylation. We propose that PTEN arginine methylation modulates pre-mRNA alternative splicing and influences diverse physiologic processes.

Increase of arginine dimethylation correlates with the progression and prognosis of ALS

OBJECTIVE

To investigate whether arginine methylation is altered in patients with amyotrophic lateral sclerosis (ALS) and how it affects disease severity, progression, and prognosis.

METHODS

We compared the immunoreactivity of protein arginine methyltransferase 1 (PRMT1) and its products, asymmetric dimethylated proteins (ASYM), in postmortem spinal cord. We also measured the concentrations of total l-arginine and methylated arginine residues, including asymmetric dimethyl l-arginine (ADMA), symmetric dimethyl arginine, and monomethyl arginine, in CSF samples from 52 patients with ALS using liquid chromatography-tandem mass spectrometry, and we examined their relationship with the progression and prognosis of ALS.

RESULTS

The immunoreactivity of both PRMT1 (p < 0.0001) and ASYM (p = 0.005) was increased in patients with ALS. The concentration of ADMA in CSF was substantially higher in patients with ALS than in disease controls. The ADMA/l-arginine ratio was correlated with the change of decline in the ALS Functional Rating Scale at 12 months after the time of measurement (r = 0.406, p = 0.010). A Cox proportional hazards model showed that the ADMA/l-arginine ratio was an independent predictor for overall survival. Moreover, a high ADMA/l-arginine ratio predicted poor prognosis, even in a group with normal percentage forced vital capacity.

CONCLUSION

There was an enhancement of arginine dimethylation in patients with ALS, and the ADMA/l-arginine ratio predicted disease progression and prognosis in such patients.

miRNA-seq analysis of human vertebrae provides insight into the mechanism underlying GIOP

High-throughput sequencing (HTS) was recently applied to detect microRNA (miRNA) regulation in age-related osteoporosis. However, miRNA regulation has not been reported in glucocorticoid-induced osteoporosis (GIOP) patients and the mechanism of GIOP remains elusive. To comprehensively analyze the role of miRNA regulation in GIOP based on human vertebrae and to explore the molecular mechanism, a high-throughput sequencing strategy was employed to identify miRNAs involved in GIOP. Twenty-six patients undergoing spinal surgery were included in this study. Six vertebral samples were selected for miRNA sequencing (miRNA-seq) analysis and 26 vertebral samples were verified by qRT-PCR. Bioinformatics was utilized for target prediction, to investigate the regulation of miRNA-mRNA networks, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. Six significantly up-regulated miRNAs (including one novel miRNA) and three significantly down-regulated miRNAs were verified via miRNA-seq and verified in the vertebrae of GIOP patients. Up-regulated miRNAs included hsa-miR-214-5p, hsa-miR-10b-5p, hsa-miR-21-5p, hsa-miR-451a, hsa-miR-186-5p, and hsa-miR-novel-chr3_49,413 while down-regulated miRNAs included hsa-let-7f-5p, hsa-let-7a-5p, and hsa-miR-27a-3p. Bioinformatics analysis revealed 5983 and 23,463 predicted targets in the up-regulated and down-regulated miRNAs respectively, using the miRanda, miRBase and TargetScan databases. The target genes of these significantly altered miRNAs were enriched to 1939 GO terms and 84 KEGG pathways. GO terms revealed that up-regulated targets were most enriched in actin filament-based processes (BP), anchoring junction (CC), and cytoskeletal protein binding (MF). Conversely, the down-regulated targets were mostly enriched in multicellular organismal development (BP), intracellular membrane-bounded organelles (CC), and protein binding (MF). Top-10 pathway analysis revealed that the differentially expressed miRNAs in GIOP were closely related to bone metabolism-related pathways such as FoxO, PI3K-Akt, MAPK and Notch signaling pathway. These results suggest that significantly altered miRNAs may play an important role in GIOP by targeting mRNA and regulating biological processes and bone metabolism-related pathways such as MAPK, FoxO, PI3K-Akt and Notch signaling, which provides novel insight into the mechanism of GIOP and lays a good foundation for the prevention and treatment of GIOP.

Long live the queen, the king and the commoner? Transcript expression differences between old and young in the termite Cryptotermes secundus

Social insects provide promising new avenues for aging research. Within a colony, individuals that share the same genetic background can differ in lifespan by up to two orders of magnitude. Reproducing queens (and in termites also kings) can live for more than 20 years, extraordinary lifespans for insects. We studied aging in a termite species, Cryptotermes secundus, which lives in less socially complex societies with a few hundred colony members. Reproductives develop from workers which are totipotent immatures. Comparing transcriptomes of young and old individuals, we found evidence for aging in reproductives that was especially associated with DNA and protein damage and the activity of transposable elements. By contrast, workers seemed to be better protected against aging. Thus our results differed from those obtained for social insects that live in more complex societies. Yet, they are in agreement with lifespan estimates for the study species. Our data are also in line with expectations from evolutionary theory. For individuals that are able to reproduce, it predicts that aging should only start after reaching maturity. As C. secundus workers are immatures with full reproductive options we expect them to invest into anti-aging processes. Our study illustrates that the degree of aging can differ between social insects and that it may be associated with caste-specific opportunities for reproduction.

Downregulation of PRMT1 promotes the senescence and migration of a non-MYCN amplified neuroblastoma SK-N-SH cells

Protein arginine methyltransferase 1 (PRMT1) catalyzing the formation of asymmetric dimethylarginines has been implicated in cancer development, metastasis, and prognosis. In this study, we investigated the effects of low PRMT1 levels on a non-MYCN amplified neuroblastoma SK-N-SH cell line. Stable PRMT1-knockdown (PRMT1-KD) cells showed reduced growth rates and cell cycle arrest at G₂/M. They also exhibited senescent phenotypes and increased p53 expression. p21 and PAI-1, which are two p53 downstream targets critical for senescence, were significantly induced in SK-N-SH cells subjected to either PRMT1-KD or inhibitor treatment. The induction was suppressed by a p53 inhibitor and marginal in a p53-null SK-N-AS cell line, suggesting dependence on p53. In general, the DNA damage and ROS levels of the PRMT1-KD SK-N-SH cells were slightly increased. Their migration activity also increased with the induction of PAI-1. Thus, PRMT1 downregulation released the repression of cellular senescence and migration activity in SK-N-SH cells. These results might partially explain the poor prognostic outcome of low PRMT1 in a non-MYCN-amplified cohort and indicate the multifaceted complexity of PRMT1 as a biological regulator of neuroblastoma.

Skeletal muscle-specific Prmt1 deletion causes muscle atrophy via deregulation of the PRMT6-FOXO3 axis

Protein arginine methyltransferases (PRMTs) have emerged as important regulators of skeletal muscle metabolism and regeneration. However, the direct roles of the various PRMTs during skeletal muscle remodeling remain unclear. Using skeletal muscle-specific prmt1 knockout mice, we examined the function and downstream targets of PRMT1 in muscle homeostasis. We found that muscle-specific PRMT1 deficiency led to muscle atrophy. PRMT1-deficient muscles exhibited enhanced expression of a macroautophagic/autophagic marker LC3-II, FOXO3 and muscle-specific ubiquitin ligases, TRIM63/MURF-1 and FBXO32, likely contributing to muscle atrophy. The mechanistic study reveals that PRMT1 regulates FOXO3 through PRMT6 modulation. In the absence of PRMT1, increased PRMT6 specifically methylates FOXO3 at arginine 188 and 249, leading to its activation. Finally, we demonstrate that PRMT1 deficiency triggers FOXO3 hyperactivation, which is abrogated by PRMT6 depletion. Taken together, PRMT1 is a key regulator for the PRMT6-FOXO3 axis in the control of autophagy and protein degradation underlying muscle maintenance. Abbreviations: Ad-RNAi: adenovirus-delivered small interfering RNA; AKT: thymoma viral proto-oncogene; AMPK: AMP-activated protein kinase; Baf A1: bafilomycin A₁; CSA: cross-sectional area; EDL: extensor digitorum longus; FBXO32: F-box protein 32; FOXO: forkhead box O; GAS: gatrocnemieus; HDAC: histone deacetylase; IGF: insulin-like growth factor; LAMP: lysosomal-associated membrane protein; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; mKO: Mice with skeletal muscle-specific deletion of Prmt1; MTOR: mechanistic target of rapamycin kinase; MYH: myosin heavy chain; MYL1/MLC1f: myosin, light polypeptide 1; PRMT: protein arginine N-methyltransferase; sgRNA: single guide RNA; SQSTM1: sequestosome 1; SOL: soleus; TA: tibialis anterior; TRIM63/MURF-1: tripartite motif-containing 63; YY1: YY1 transcription factor.

Menin Upregulates FOXO1 Protein Stability by Repressing Skp2-Mediated Degradation in β Cells

OBJECTIVES

Menin, a chromatin binding protein, interacts with various epigenetic regulators to regulate gene transcription, whereas forkhead box protein O1 (FOXO1) is a transcription factor that can be regulated by multiple signaling pathways. Both menin and FOXO1 are crucial regulators of β-cell function and metabolism; however, whether or how they interplay to regulate β cells is not clear.

METHODS

To examine whether menin affects expression of FOXO1, we ectopically expressed menin complementary DNA and small hairpin RNA targeting menin via a retroviral vector in INS-1 cells. Western blotting was used to analyze protein levels.

RESULTS

Our current work shows that menin increases the expression of FOXO1. Menin stabilizes FOXO1 protein level in INS-1 cells, as shown by increased half-life of FOXO1 by menin expression. Moreover, menin represses ubiquitination of FOXO1 protein and AKT phosphorylation, We found that menin stabilizes FOXO1 by repressing FOXO1 degradation mediated by S-phase kinase-associated protein 2 (Skp2), an E3 ubiquitin ligase, promoting caspase 3 activation and apoptosis.

CONCLUSIONS

Because FOXO1 upregulates the menin gene transcription, our findings unravel a crucial menin and FOXO1 interplay, with menin and FOXO1 upregulating their expression reciprocally, forming a positive feedback loop to sustain menin and FOXO1 expression.

Emerging impacts of biological methylation on genetic information

The central dogma of molecular biology explains the fundamental flow of genetic information for life. Although genome sequence (DNA) itself is a static chemical signature, it includes multiple layers of information composed of mRNA, tRNA, rRNA and small RNAs, all of which are involved in protein synthesis and is passing from parents to offspring via DNA. Methylation is a biologically important modification, because DNA, RNAs and proteins, components of the central dogma, are methylated by a set of methyltransferases. Recent works focused on understanding a variety of biological methylation have shed light on new regulation of cellular functions. In this review, we briefly discuss some of those recent findings of methylation, including DNA, RNAs and proteins.

Unraveling the Regulation of Hepatic Gluconeogenesis

Hepatic gluconeogenesis, de novo glucose synthesis from available precursors, plays a crucial role in maintaining glucose homeostasis to meet energy demands during prolonged starvation in animals. The abnormally increased rate of hepatic gluconeogenesis contributes to hyperglycemia in diabetes. Gluconeogenesis is regulated on multiple levels, such as hormonal secretion, gene transcription, and posttranslational modification. We review here the molecular mechanisms underlying the transcriptional regulation of gluconeogenesis in response to nutritional and hormonal changes. The nutrient state determines the hormone release, which instigates the signaling cascades in the liver to modulate the activities of various transcriptional factors through various post-translational modifications like phosphorylation, methylation, and acetylation. AMP-activated protein kinase (AMPK) can mediate the activities of some transcription factors, however its role in the regulation of gluconeogenesis remains uncertain. Metformin, a primary hypoglycemic agent of type 2 diabetes, ameliorates hyperglycemia predominantly through suppression of hepatic gluconeogenesis. Several molecular mechanisms have been proposed to be metformin's mode of action.

Zfp238 Regulates the Thermogenic Program in Cooperation with Foxo1

Obesity has become an explicit public health concern because of its relevance to metabolic syndrome. Evidence points to the significance of beige adipocytes in regulating energy expenditure. Here, using yeast two-hybrid screening, we show that Zfp238 is a Foxo1 co-repressor and that adipose-tissue-specific ablation of Zfp238 (Adipo-Zfp238KO) in mice leads to obesity, decreased energy expenditure, and insulin resistance under normal chow diet. Adipo-Zfp238KO inhibits induction of Ucp1 expression in subcutaneous adipose tissue upon cold exposure or CL316243, but not in brown adipose tissue. Furthermore, knockdown of Zfp238 in 3T3-L1 cells decreases Ucp1 expression in response to cool incubation or forskolin significantly compared with control cells. In contrast, overexpression of Zfp238 in 3T3-L1 cells significantly increases Ucp1 expression in response to forskolin. Finally, double knockdown of both Zfp238 and Foxo1 normalizes Ucp1 induction. These data suggest that Zfp238 in adipose tissue regulates the thermogenic program in cooperation with Foxo1.

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Zfp238 is a Foxo1 co-repressor

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Zfp238 deficiency in adipocyte leads to obesity and decreased energy expenditure

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Knockdown of Zfp238 in 3T3-L1 cells decreases Ucp1 induction

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Double knockdown of both Zfp238 and Foxo1 normalizes Ucp1 induction

The Methods Employed in Mass Spectrometric Analysis of Posttranslational Modifications (PTMs) and Protein-Protein Interactions (PPIs)

Mass Spectrometry (MS) has revolutionized the way we study biomolecules, especially proteins, their interactions and posttranslational modifications (PTM). As such MS has established itself as the leading tool for the analysis of PTMs mainly because this approach is highly sensitive, amenable to high throughput and is capable of assigning PTMs to specific sites in the amino acid sequence of proteins and peptides. Along with the advances in MS methodology there have been improvements in biochemical, genetic and cell biological approaches to mapping the interactome which are discussed with consideration for both the practical and technical considerations of these techniques. The interactome of a species is generally understood to represent the sum of all potential protein-protein interactions. There are still a number of barriers to the elucidation of the human interactome or any other species as physical contact between protein pairs that occur by selective molecular docking in a particular spatiotemporal biological context are not easily captured and measured.PTMs massively increase the complexity of organismal proteomes and play a role in almost all aspects of cell biology, allowing for fine-tuning of protein structure, function and localization. There are an estimated 300 PTMS with a predicted 5% of the eukaryotic genome coding for enzymes involved in protein modification, however we have not yet been able to reliably map PTM proteomes due to limitations in sample preparation, analytical techniques, data analysis, and the substoichiometric and transient nature of some PTMs. Improvements in proteomic and mass spectrometry methods, as well as sample preparation, have been exploited in a large number of proteome-wide surveys of PTMs in many different organisms. Here we focus on previously published global PTM proteome studies in the Apicomplexan parasites T. gondii and P. falciparum which offer numerous insights into the abundance and function of each of the studied PTM in the Apicomplexa. Integration of these datasets provide a more complete picture of the relative importance of PTM and crosstalk between them and how together PTM globally change the cellular biology of the Apicomplexan protozoa. A multitude of techniques used to investigate PTMs, mostly techniques in MS-based proteomics, are discussed for their ability to uncover relevant biological function.

Trifluoperazine prevents FOXO1 nuclear excretion and reverses doxorubicin-resistance in the SHG44/DOX drug-resistant glioma cell line

As a tumor suppressor, Forkhead box O1 (FOXO1) is located in the nucleus where it regulates gene expression and inhibits tumor progression. However, the antitumor effects of FOXO1 are attenuated in several tumors due to its translocation from the nucleus to the cytoplasm. Trifluoperazine (TFP) is able to reverse tumor drug resistance by inhibiting multidrug resistance (MDR), however, the detailed molecular mechanisms by which this occurs remain to be fully elucidated. In the present study, the doxorubicin (DOX)‑resistant SHG44/DOX glioma cell line was established. The results showed that TFP promoted DOX‑induced cytotoxicity, cell cycle arrest and early apoptosis using a Cell Counting Kit‑8 and flow cytometry. In vivo experiments also demonstrated that DOX combined with TFP reduced tumor volumes and proliferation indices, and led to higher protein levels of FOXO1. In addition, TFP inhibited the nuclear exclusion of FOXO1, contributing toward the downregulation of MDR genes and an increase in intracellular DOX concentrations by reverse transcription‑quantitative polymerase chain reaction, western blot analysis, immunofluorescence and spectrophotometer analysis. Therefore, TFP may inhibit DOX resistance by stimulating FOXO1 nuclear translocation and suppressing MDF genes in SHG44/DOX cells, contributing to promising clinical prospects for tumor chemotherapy.

Cardiac specific PRMT1 ablation causes heart failure through CaMKII dysregulation

Dysregulation of Ca²⁺/calmodulin-dependent protein kinase (CaMK)II is closely linked with myocardial hypertrophy and heart failure. However, the mechanisms that regulate CaMKII activity are incompletely understood. Here we show that protein arginine methyltransferase 1 (PRMT1) is essential for preventing cardiac CaMKII hyperactivation. Mice null for cardiac PRMT1 exhibit a rapid progression to dilated cardiomyopathy and heart failure within 2 months, accompanied by cardiomyocyte hypertrophy and fibrosis. Consistently, PRMT1 is downregulated in heart failure patients. PRMT1 depletion in isolated cardiomyocytes evokes hypertrophic responses with elevated remodeling gene expression, while PRMT1 overexpression protects against pathological responses to neurohormones. The level of active CaMKII is significantly elevated in PRMT1-deficient hearts or cardiomyocytes. PRMT1 interacts with and methylates CaMKII at arginine residues 9 and 275, leading to its inhibition. Accordingly, pharmacological inhibition of CaMKII restores contractile function in PRMT1-deficient mice. Thus, our data suggest that PRMT1 is a critical regulator of CaMKII to maintain cardiac function.

The mechanisms that regulate the activity of Ca^2 +/calmodulin-dependent protein kinase II (CaMKII) in the context of heart failure are incompletely understood. Here the authors show that protein arginine methyltransferase 1 (PRMT1) prevents cardiac hyperactivation of CaMKII and heart failure development by methylating CaMKII at arginine residues 9 and 275.

PRMT1 Deficiency in Mouse Juvenile Heart Induces Dilated Cardiomyopathy and Reveals Cryptic Alternative Splicing Products

Protein arginine methyltransferase 1 (PRMT1) catalyzes the asymmetric dimethylation of arginine residues in proteins and methylation of various RNA-binding proteins and is associated with alternative splicing in vitro. Although PRMT1 has essential in vivo roles in embryonic development, CNS development, and skeletal muscle regeneration, the functional importance of PRMT1 in the heart remains to be elucidated. Here, we report that juvenile cardiomyocyte-specific PRMT1-deficient mice develop severe dilated cardiomyopathy and exhibit aberrant cardiac alternative splicing. Furthermore, we identified previously undefined cardiac alternative splicing isoforms of four genes (Asb2, Fbxo40, Nrap, and Eif4a2) in PRMT1-cKO mice and revealed that eIF4A2 protein isoforms translated from alternatively spliced mRNA were differentially ubiquitinated and degraded by the ubiquitin-proteasome system. These findings highlight the essential roles of PRMT1 in cardiac homeostasis and alternative splicing regulation.

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PRMT1 deficiency in cardiomyocytes causes dilated cardiomyopathy in juvenile mice

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PRMT1-deficient heart shows abnormal alternative splicing patterns

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Previously undefined cardiac splicing events are revealed by transcriptome analysis

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eIF4A2 isoforms are differentially ubiquitinated and degraded

Role of FOXO transcription factors in crosstalk between mitochondria and the nucleus

FOXO transcription factors are evolutionally conserved regulators of organismal life span downstream of insulin signaling. After integrating cellular signals from various stimuli such as growth factors, oxidative stress, and energy deprivation, FOXO factors induce expression of a specific set of genes that regulate various cellular processes to maintain homeostasis at a cellular or organismal level. In this review, we discuss roles of FOXO proteins in the maintenance of mitochondria, organelles critical for cellular quality control. FOXO factors protect mitochondria by activating mitochondrial antioxidant enzymes and they help remodel damaged mitochondria by inducing remodeling processes such as mitophagy. Furthermore, we also review the recently identified FOXO-dependent retrograde signaling from stressed mitochondria to the nucleus, which suggest that FOXO mediates the crosstalk between these two important organelles to maintain cell homeostasis. In addition, we introduce a mitohormetic role of gamitrinib-triphenylphosphonium (G-TPP), a mitochondrial heat shock protein (Hsp) inhibitor that can induce mild mitochondrial stress to protect cells from future insults in a FOXO-dependent manner.

The Protein Arginine Methyltransferase PRMT-5 Regulates SER-2 Tyramine Receptor-Mediated Behaviors in Caenorhabditis elegans

G protein-coupled receptors are 7-pass transmembrane receptors that couple to heterotrimeric G proteins to mediate cellular responses to a diverse array of stimuli. Understanding the mechanisms that regulate G protein-coupled receptors is crucial to manipulating their signaling for therapeutic benefit. One key regulatory mechanism that contributes to the functional diversity of many signaling proteins is post-translational modification. Whereas phosphorylation remains the best studied of such modifications, arginine methylation by protein arginine methyltransferases is emerging as a key regulator of protein function. We previously published the first functional evidence that arginine methylation of G protein-coupled receptors modulates their signaling. We report here a third receptor that is regulated by arginine methylation, the Caenorhabditis elegans SER-2 tyramine receptor. We show that arginines within a putative methylation motif in the third intracellular loop of SER-2 are methylated by PRMT5 in vitro Our data also suggest that this modification enhances SER-2 signaling in vivo to modulate animal behavior. The identification of a third G protein-coupled receptor to be functionally regulated by arginine methylation suggests that this post-translational modification may be utilized to regulate signaling through a broad array of G protein-coupled receptors.

-Characterization of pyruvate kinase from the anoxia tolerant turtle, Trachemys scripta elegans: a potential role for enzyme methylation during metabolic rate depression

Background

Pyruvate kinase (PK) is responsible for the final reaction in glycolysis. As PK is a glycolytic control point, the analysis of PK posttranslational modifications (PTM) and kinetic changes reveals a key piece of the reorganization of energy metabolism in an anoxia tolerant vertebrate.

Methods

To explore PK regulation, the enzyme was isolated from red skeletal muscle and liver of aerobic and 20-hr anoxia-exposed red eared-slider turtles (Trachemys scripta elegans). Kinetic analysis and immunoblotting were used to assess enzyme function and the corresponding covalent modifications to the enzymes structure during anoxia.

Results

Both muscle and liver isoforms showed decreased affinity for phosphoenolpyruvate substrate during anoxia, and muscle PK also had a lower affinity for ADP. I₅₀ values for the inhibitors ATP and lactate were lower for PK from both tissues after anoxic exposure while I₅₀ L-alanine was only reduced in the liver. Both isozymes showed significant increases in threonine phosphorylation (by 42% in muscle and 60% in liver) and lysine methylation (by 43% in muscle and 70% in liver) during anoxia which have been linked to suppression of PK activity in other organisms. Liver PK also showed a 26% decrease in tyrosine phosphorylation under anoxia.

Discussion

Anoxia responsive changes in turtle muscle and liver PK coordinate with an overall reduced activity state. This reduced affinity for the forward glycolytic reaction is likely a key component of the overall metabolic rate depression that supports long term survival in anoxia tolerant turtles. The coinciding methyl- and phospho- PTM alterations present the mechanism for tissue specific enzyme modification during anoxia.

Identifying conserved UV exposure genes and mechanisms

Studies have been showing how changes in ultraviolet (UV) affect the terrestrial system, mostly focusing on higher plants and indirect effects, e.g. UV changed food quality/decomposition. Much less attention has been given to direct effect on terrestrial species, although the negative effects have been recognized for some earthworms. Further, the actual mechanisms of UV toxicity to soil invertebrates are even less understood. We here studied the effect of UV on the soil oligochaete Enchytraeus crypticus, and attempted to identify the possible mechanisms of toxicity using high-throughput gene expression. Applying a UV dose equivalent to UV during the winter months in northern Europe we observed an 80% decrease in reproduction. For these organisms, approximately 5% of the genes were differentially expressed. Among the observations was an activation of the DNA repair mechanisms, nucleotide excision repair, which correlated with survival of the organisms. An observed repressing of apoptosis seems to have deleterious effects (e.g. because it may lead to the accumulation of aberrant cells) leading to a decline in reproduction. The mechanisms activated by UV were similar to those mechanisms activated in humans, showing conservation across species.

Recent advances in targeting protein arginine methyltransferase enzymes in cancer therapy

INTRODUCTION

Exploration in the field of epigenetics has revealed the diverse roles of the protein arginine methyltransferase (PRMT) family of proteins in multiple disease states. These findings have led to the development of specific inhibitors and discovery of several new classes of drugs with potential to treat both benign and malignant conditions. Areas covered: We provide an overview on the role of PRMT enzymes in healthy and malignant cells, highlighting the role of arginine methylation in specific pathways relevant to cancer pathogenesis. Additionally, we describe structure and catalytic activity of PRMT and discuss the mechanisms of action of novel small molecule inhibitors of specific members of the arginine methyltransferase family. Expert opinion: As the field of PRMT biology advances, it's becoming clear that this class of enzymes is highly relevant to maintaining normal physiologic processes as well and disease pathogenesis. We discuss the potential impact of PRMT inhibitors as a broad class of drugs, including the pleiotropic effects, off target effects the need for more detailed PRMT-centric interactomes, and finally, the potential for targeting this class of enzymes in clinical development of experimental therapeutics for cancer.

Increasing Cardiomyocyte Atrogin-1 Reduces Aging-Associated Fibrosis and Regulates Remodeling in Vivo

The muscle-specific ubiquitin ligase atrogin-1 (MAFbx) has been identified as a critical regulator of pathologic and physiological cardiac hypertrophy; it regulates these processes by ubiquitinating transcription factors [nuclear factor of activated T-cells and forkhead box O (FoxO) 1/3]. However, the role of atrogin-1 in regulating transcription factors in aging has not previously been described. Atrogin-1 cardiomyocyte-specific transgenic (Tg⁺) adult mice (α-major histocompatibility complex promoter driven) have normal cardiac function and size. Herein, we demonstrate that 18-month-old atrogin-1 Tg⁺ hearts exhibit significantly increased anterior wall thickness without functional impairment versus wild-type mice. Histologic analysis at 18 months revealed atrogin-1 Tg⁺ mice had significantly less fibrosis and significantly greater nuclei and cardiomyocyte cross-sectional analysis. Furthermore, by real-time quantitative PCR, atrogin-1 Tg⁺ had increased Col 6a4, 6a5, 6a6, matrix metalloproteinase 8 (Mmp8), and Mmp9 mRNA, suggesting a role for atrogin-1 in regulating collagen deposits and MMP-8 and MMP-9. Because atrogin-1 Tg⁺ mice exhibited significantly less collagen deposition and protein levels, enhanced Mmp8 and Mmp9 mRNA may offer one mechanism by which collagen levels are kept in check in the aged atrogin-1 Tg⁺ heart. In addition, atrogin-1 Tg⁺ hearts showed enhanced FoxO1/3 activity. The present study shows a novel link between atrogin-1-mediated regulation of FoxO1/3 activity and reduced collagen deposition and fibrosis in the aged heart. Therefore, targeting FoxO1/3 activity via the muscle-specific atrogin-1 ubiquitin ligase may offer a muscle-specific method to modulate aging-related cardiac fibrosis.

Arginine methylation of translocated in liposarcoma (TLS) inhibits its binding to long noncoding RNA, abrogating TLS-mediated repression of CBP/p300 activity

Translocated in liposarcoma (TLS) is an RNA-binding protein and a transcription-regulatory sensor of DNA damage. TLS binds promoter-associated noncoding RNA (pncRNA) and inhibits histone acetyltransferase (HAT) activity of CREB-binding protein (CBP)/E1A-binding protein P300 (p300) on the cyclin D1 (CCND1) gene. Although post-translational modifications of TLS, such as arginine methylation, are known to regulate TLS's nucleocytoplasmic shuttling and assembly in stress granules, its interactions with RNAs remain poorly characterized. Herein, using various biochemical assays, we confirmed the earlier observations that TLS is methylated by protein arginine methyltransferase 1 (PRMT1) in vitro The arginine methylation of TLS disrupted binding to pncRNA and also prevented binding of TLS to and inhibition of CBP/p300. This result indicated that arginine methylation of TLS abrogates both binding to pncRNA and TLS-mediated inhibition of CBP/p300 HAT activities. We also report that an arginine residue within the Arg-Gly-Gly domain of TLS, Arg-476, serves as the major determinant for binding to pncRNA. Either methylation or mutation of Arg-476 of TLS significantly decreased pncRNA binding and thereby prevented a pncRNA-induced allosteric alteration in TLS that is required for its interaction with CBP/p300. Moreover, unlike WT TLS, an R476A TLS mutant did not inhibit CCND1 promoter activity in luciferase reporter assays. Taken together, we propose the hypothesis that arginine methylation of TLS regulates both TLS-nucleic acid and TLS-protein interactions and thereby participates in transcriptional regulation.

The GATA transcription factor ELT-2 modulates both the expression and methyltransferase activity of PRMT-1 in Caenorhabditis elegans

Protein arginine methyltransferase 1 (PRMT1) catalyzes asymmetric arginine dimethylation of cellular proteins and thus modulates various biological processes, including gene regulation, RNA metabolism, cell signaling and DNA repair. Since prmt-1 null mutant completely abolishes asymmetric dimethylarginine in C. elegans, PRMT-1 is thought to play a crucial role in determining levels of asymmetric arginine dimethylation. However, the mechanism underlying the regulation of PRMT-1 activity remains largely unknown. Here, we explored for transcription factors that induce the expression of PRMT-1 by an RNAi screen using transgenic C. elegans harbouring prmt-1 promoter upstream of gfp. Of 529 clones, we identify a GATA transcription factor elt-2 as a positive regulator of Pprmt-1:: gfp expression and show that elt-2 RNAi decreases endogenous PRMT-1 expression at mRNA and protein levels. Nevertheless, surprisingly arginine methylation levels are increased when elt-2 is silenced, implying that erythroid-like transcription factor (ELT)-2 may also have ability to inhibit methyltransferase activity of PRMT-1. Supporting this idea, GST pull-down and co-immunoprecipitation assays demonstrate the interaction between ELT-2 and PRMT-1. Furthermore, we find that ELT-2 interferes with PRMT-1-induced arginine methylation in a dose-dependent manner. Collectively, our results illustrate the two modes of PRMT-1 regulation, which could determine the levels of asymmetric arginine dimethylation in C. elegans.

GDF15 promotes the proliferation of cervical cancer cells by phosphorylating AKT1 and Erk1/2 through the receptor ErbB2

BACKGROUND

Growth differentiation factor 15 (GDF15) is a member of the TGF-β superfamily, and evidence suggests that a substantial amount of GDF15 is secreted in various human cancers, such as ovarian cancer, prostate cancer, and breast cancer, among others. However, the function of GDF15 in cervical cancer has not yet been reported.

METHODS

Immunohistochemistry was used to detect GDF15 expression in normal cervix and in different cervical cancer lesions. Cell growth curves, MTT, tumor formation assays and flow cytometry were utilized to observe the effects of ectopic GDF15 expression on the proliferation and cell cycle of cervical cancer cells. Real-time PCR, western blotting and immunoprecipitation assays were conducted to measure the expression of genes related to the cell cycle and the PI3K/AKT and MAPK/ERK signaling pathways. A chromatin immunoprecipitation assay was performed to confirm whether C-myc bound to a specific region of the GDF15 promoter. Inhibitor treatment and immunoprecipitation assays were employed to identify the association between GDF15 and ErbB2.

RESULTS

GDF15 expression gradually increased during the progression of cervical carcinogenesis. GDF15 promoted cervical cancer cell proliferation via exogenous rhGDF15 treatment or the use of gene editing technology in vitro and in vivo and significantly accelerated the cell cycle transition from G0/G1 to S phase. The expression of p-ErbB2, p-AKT1, p-Erk1/2, CyclinD1 and CyclinE1 was up-regulated and the expression of p21 was down-regulated in GDF15-overexpressing and rhGDF15-treated cervical cancer cells. C-myc trans-activated GDF15 expression by binding to the E-box motifs in the promoter of GDF15 and contributed to the positive feedback of GDF15/C-myc/GDF15. Furthermore, GDF15 bound to ErbB2 in a protein complex in cervical cancer cells.

CONCLUSIONS

Our data demonstrated that GDF15 promoted the proliferation of cervical cancer cells via the up-regulation of CyclinD1 and CyclinE1 and the down-regulation of p21 through both the PI3K/AKT and MAPK/ERK signaling pathways in a complex with ErbB2.

FOXO1 cysteine-612 mediates stimulatory effects of the coregulators CBP and PGC1α on FOXO1 basal transcriptional activity

Hepatic production and release of metabolites, nutrients and micronutrient transporters is tightly regulated at the level of gene expression. In this regard, transcription factor FOXO1 modulates the expression of genes such as G6PC and SELENOP, encoding the catalytic subunit of glucose 6-phosphatase and the plasma selenium transporter selenoprotein P, respectively. Here, we analyzed the role of cysteine residues in FOXO1 in controlling its activity with respect to regulation of G6PC and SELENOP in HepG2 human hepatoma cells. None of the seven FOXO1 cysteines affected FOXO1 binding to DNA or its basal subcellular distribution. Whereas overexpression of wildtype FOXO1 caused a strong induction of both G6PC and SELENOP promoter activities and mRNA levels, the induction was lowered by approx. 50% if cysteine-deficient FOXO1 was overexpressed instead. Only the most C-terminal of the seven FOXO1 cysteines, Cys612, was required and sufficient to ensure full FOXO1 transactivation activity. Coexpression of FOXO1 coregulators, CBP or PGC1α, had a strong synergistic effect in stimulating G6PC promoter activity and expression, fully relying on the presence of FOXO1 Cys612. Similarly, a synergistic effect of FOXO1 and CBP was observed for SELENOP. In contrast, stimulation of SELENOP by PGC1α was independent of FOXO1-Cys612, due to the close proximity of a hepatocyte nuclear factor-4α binding site to the FOXO1 binding site within the SELENOP promoter, as demonstrated using mutant SELENOP promoter constructs. In summary, full basal FOXO1 transactivation activity relies on Cys612, which mediates synergistic effects of coregulators, CBP or PGC1α, on FOXO1 transcriptional activity. The extent of Cys612 contribution depends on the promoter context of FOXO1 target genes.

Molecular control of B-cell homeostasis in health and malignancy

Altered B-cell homeostasis underlies a wide range of pathologies, from cancers to autoimmunity and immunodeficiency. The molecular safeguards against those disorders, which also allow effective immune responses, are therefore particularly critical. Here, we review recent findings detailing the fine control of B-cell homeostasis, during B-cell development, maturation in the periphery and during activation and differentiation into antibody-producing cells.

Lyn, Lupus, and (B) Lymphocytes, a Lesson on the Critical Balance of Kinase Signaling in Immunity

Systemic lupus erythematosus (SLE) is a progressive autoimmune disease characterized by increased sensitivity to self-antigens, auto-antibody production, and systemic inflammation. B cells have been implicated in disease progression and as such represent an attractive therapeutic target. Lyn is a Src family tyrosine kinase that plays a major role in regulating signaling pathways within B cells as well as other hematopoietic cells. Its role in initiating negative signaling cascades is especially critical as exemplified by Lyn-/- mice developing an SLE-like disease with plasma cell hyperplasia, underscoring the importance of tightly regulating signaling within B cells. This review highlights recent advances in our understanding of the function of the Src family tyrosine kinase Lyn in B lymphocytes and its contribution to positive and negative signaling pathways that are dysregulated in autoimmunity.

The Role of Sirt6 in Obesity and Diabetes

Sirt6 is one of the sirtuin family members, a kind of NAD+-dependent histone deacetylase and ADP-ribose transferase enzyme. It has an important role in physiological and pathological processes, regulating aging, cancer, obesity, insulin resistance, inflammation, and energy metabolism. Recent studies have suggested that reduced Sirt6 action is related to obesity and diabetes. Aging and overnutrition, two major risk factors for obesity and diabetes, lead to decreased Sirt6 level and function, which results in abnormal glucose and lipid metabolism. Whole-body ablation of Sirt6 in mice results in severe hypoglycemia. Sirt6 deficiency leads to liver steatosis and promotes diet-induced obesity and insulin resistance. Sirt6 has a protective effect on obesity and diabetes. This review surveys evidence for an emerging role of Sirt6 as a regulator of metabolism in mammals and summarizes its major functions in obesity and diabetes.

Protein arginine methylation/demethylation and cancer

Protein arginine methylation is a common post-translational modification involved in numerous cellular processes including transcription, DNA repair, mRNA splicing and signal transduction. Currently, there are nine known members of the protein arginine methyltransferase (PRMT) family, but only one arginine demethylase has been identified, namely the Jumonji domain-containing 6 (JMJD6). Although its demethylase activity was initially challenged, its dual activity as an arginine demethylase and a lysine hydroxylase is now recognized. Interestingly, a growing number of substrates for arginine methylation and demethylation play key roles in tumorigenesis. Though alterations in the sequence of these enzymes have not been identified in cancer, their overexpression is associated with various cancers, suggesting that they could constitute targets for therapeutic strategies. In this review, we present the recent knowledge of the involvement of PRMTs and JMJD6 in tumorigenesis.

Role of Forkhead Box O (FOXO) transcription factor in aging and diseases

Fork head box O (FOXO) transcription factor is a key player in an evolutionarily conserved pathway. The mammalian FOXO family consists of FOXO1, 3, 4 and 6, are highly similar in their structure, function and regulation. To maintain optimum body function, the organisms have developed complex mechanisms for homeostasis. Importantly, it is well known that when these mechanisms dysregulate it results in the development of age-related disease. FOXO proteins are involved in a diverse cellular function and also have clinical significance including cell cycle arrest, cell differentiation, tumour suppression, DNA repair, longevity, diabetic complications, immunity, wound healing, regulation of metabolism and thus treatment of several types of diseases. By the combinations of post-translational modifications FOXO's serve as a 'molecular code' to sense external stimuli and recruit it as to specific regions of the genome and provide an integrated cellular response to changing physiological conditions. Akt/Protein kinase B a signaling pathway as a main regulator of FOXO to perform a diverse function in organisms. The present review summarizes the molecular and clinical aspects of FOXO transcription factor. And also elaborate the interaction of FOXO with the nucleosome remodelling complex to target genes, which is essential to cellular homeostasis.

FOXO in Neural Cells and Diseases of the Nervous System

The evolutionarily conserved FOXO family of transcription factors has emerged as a significant arbiter of neural cell fate and function in mammals. From the neural stem cell (NSC) state through mature neurons under both physiological and pathological conditions, they have been found to modulate neural cell survival, stress responses, lineage commitment, and neuronal signaling. Lineage-specific FOXO knockout mice have provided an invaluable tool for the dissection of FOXO biology in the nervous system. Within the NSC compartments of the brain, FOXOs are required for the maintenance of NSC quiescence and for the clearance of reactive oxygen species. Within mature neurons, FOXO transcriptional activity is essential for the prevention of age-dependent axonal degeneration. Acutely, FOXO3 has been found to cause axonal degeneration upon withdrawal of neurotrophic factors. In more active neural signaling, FOXO6 promotes increased dendritic spine density of hippocampal neurons and is required for the consolidation of memories. In addition to the central nervous system (CNS), FOXOs also influence the functionality of the peripheral nervous system (PNS). FOXO1 knockout within the PNS results in a reduction of sympathetic tone and decreased levels of brain-derived norepinephrine and lower energy expenditure. FOXO3 knockout mice have impaired hearing which may be due to defects in synapse localization within the ear. Given the scope of FOXO activities in both the CNS and PNS, it will be of interest to study FOXOs within the context of neurodegenerative diseases such as Alzheimer's, Parkinson's, Huntington's, and amyotrophic lateral sclerosis. From within the nervous system, FOXOs may also regulate important parameters such as whole-body metabolism, motor function, and catecholamine production, making FOXOs key players in physiologic homeostasis.

FOXO family in regulating cancer and metabolism

FOXO proteins are a sub-group of a superfamily of forkhead box (FOX)-containing transcription factors (TFs). FOXOs play an important role in regulating a plethora of biological activities ranging from development, cell signaling, and tumorigenesis to cell metabolism. Here we mainly focus on reviewing the role of FOXOs in regulating tumor and metabolism. Moreover, how crosstalk among various pathways influences the function of FOXOs will be reviewed. Further, the paradoxical role for FOXOs in controlling the fate of cancer and especially resistance/sensitivity of cancer to the class of drugs that target PI3K/AKT will also be reviewed. Finally, how FOXOs regulate crosstalk between common cancer pathways and cell metabolism pathways, and how these crosstalks affect the fate of the cancer will be discussed.

FoxO transcription factors in cancer metabolism

FoxO transcription factors serve as the central regulator of cellular homeostasis and are tumor suppressors in human cancers. Recent studies have revealed that, besides their classic functions in promoting cell death and inducing cell cycle arrest, FoxOs also regulate cancer metabolism, an emerging hallmark of cancer. In this review, we summarize the regulatory mechanisms employed to control FoxO activities in the context of cancer biology, and discuss FoxO function in metabolism reprogramming in cancer and interaction with other key cancer metabolism pathways. A deeper understanding of FoxOs in cancer metabolism may reveal novel therapeutic opportunities in cancer treatment.

PRMT1 promotes hyperglycemia in a FoxO1-dependent manner, affecting glucose metabolism, during hypobaric hypoxia exposure, in rat model

PURPOSE

High-altitude (HA) environment causes changes in cellular metabolism among unacclimatized humans. Previous studies have revealed that insulin-dependent activation of protein kinase B (Akt) regulates metabolic processes via discrete transcriptional effectors. Moreover, protein arginine methyltransferase (PRMT)1-dependent arginine modification of forkhead box other (FoxO)1 protein interferes with Akt-dependent phosphorylation. The present study was undertaken to test the involvement of PRMT1 on FoxO1 activation during hypobaric hypoxia (HH) exposure in rat model.

METHODS

Samples were obtained from normoxia control (NC) and HH-exposed (H) rats, subdivided according to the duration of HH exposure. To explore the specific role played by PRMT1 during HH exposure, samples from 1d pair-fed (PF) NC, 1d acute hypoxia-exposed (AH) placebo-treated, and 1d AH TC-E-5003-treated rats were investigated. Quantitative reverse transcriptase polymerase chain reaction (RT-qPCR) was performed to determine expressions of glycolytic, gluconeogenic enzymes, and insulin response regulating genes. Immuno-blot and enzyme linked immunosorbent assay (ELISA) were used for insulin response regulating proteins. Nuclear translocation of FoxO1 was analyzed using deoxyribonucleic acid (DNA)-binding ELISA kit.

RESULTS

We observed HH-induced increase in glycolytic enzyme expressions in hepatic tissue unlike hypothalamic tissue. PRMT1 expression increased during HH exposure, causing insulin resistance and resulting increase in FoxO1 nuclear translocation, leading to hyperglycemia. Conversely, PRMT1 inhibitor treatment promoted inhibition of FoxO1 activity and increase in glucose uptake during HH exposure leading to reduction in blood-glucose and hepatic glycogen levels.

CONCLUSIONS

PRMT1 might have a potential importance as a therapeutic target for the treatment of HH-induced maladies.

Functional analyses of major cancer-related signaling pathways in Alzheimer's disease etiology

Alzheimer's disease (AD) is an aging-related neurodegenerative disease and accounts for majority of human dementia. The hyper-phosphorylated tau-mediated intracellular neurofibrillary tangle and amyloid β-mediated extracellular senile plaque are characterized as major pathological lesions of AD. Different from the dysregulated growth control and ample genetic mutations associated with human cancers, AD displays damage and death of brain neurons in the absence of genomic alterations. Although various biological processes predominately governing tumorigenesis such as inflammation, metabolic alteration, oxidative stress and insulin resistance have been associated with AD genesis, the mechanistic connection of these biological processes and signaling pathways including mTOR, MAPK, SIRT, HIF, and the FOXO pathway controlling aging and the pathological lesions of AD are not well recapitulated. Hence, we performed a thorough review by summarizing the physiological roles of these key cancer-related signaling pathways in AD pathogenesis, comprising of the crosstalk of these pathways with neurofibrillary tangle and senile plaque formation to impact AD phenotypes. Importantly, the pharmaceutical investigations of anti-aging and AD relevant medications have also been highlighted. In summary, in this review, we discuss the potential role that cancer-related signaling pathways may play in governing the pathogenesis of AD, as well as their potential as future targeted strategies to delay or prevent aging-related diseases and combating AD.

Mechanisms controlling the anti-neoplastic functions of FoxO proteins

The Forkhead box O (FoxO) proteins comprise a family of evolutionarily conserved transcription factors that predominantly function as tumor suppressors. These proteins assume diverse roles in the cellular anti-neoplastic response, including regulation of apoptosis and autophagy, cancer metabolism, cell-cycle arrest, oxidative stress and the DNA damage response. More recently, FoxO proteins have been implicated in cancer immunity and cancer stem-cell (CSC) homeostasis. Interestingly, in some sporadic sub-populations, FoxO protein function may also be manipulated by factors such as β-catenin whereby they instead can facilitate cancer progression via maintenance of CSC properties or promoting drug resistance or metastasis and invasion. This review highlights the essential biological functions of FoxOs and explores the areas that may be exploited in FoxO protein signaling pathways in the development of novel cancer therapeutic agents.

Regulation of FOXO Factors in Mammalian Cells

Forkhead box O (FOXO) transcription factors are central regulators of cellular homeostasis. FOXOs respond to a wide range of external stimuli, including growth factor signaling, oxidative stress, genotoxic stress, and nutrient deprivation. These signaling inputs regulate FOXOs through a number of posttranslational modifications, including phosphorylation, acetylation, ubiquitination, and methylation. Covalent modifications can affect localization, DNA binding, and interactions with other cofactors in the cell. FOXOs integrate the various modifications to regulate cell type-specific gene expression programs that are essential for metabolic homeostasis, redox balance, and the stress response. Together, these functions are critical for coordinating a response to environmental fluctuations in order to maintain cellular homeostasis during development and to support healthy aging.

The methyltransferase NSD3 promotes antiviral innate immunity via direct lysine methylation of IRF3

Wang et al. demonstrate that methyltransferase NSD3 directly methylates IRF3 and maintains IRF3 phosphorylation to enhance its transcriptional activity by disassociating the methylated IRF3 and PP1cc to prevent IRF3 dephosphorylation, consequently promoting antiviral innate immune response.

Lysine methylation is an important posttranslational modification, implicated in various biological pathological conditions. The transcription factor interferon regulatory factor 3 (IRF3) is essential for antiviral innate immunity, yet the mechanism for methylation control of IRF3 activation remains unclear. In this paper, we discovered monomethylation of IRF3 at K366 is critical for IRF3 transcription activity in antiviral innate immunity. By mass spectrometry analysis of IRF3-associated proteins, we identified nuclear receptor–binding SET domain 3 (NSD3) as the lysine methyltransferase that directly binds to the IRF3 C-terminal region through its PWWP1 domain and methylates IRF3 at K366 via its SET domain. Deficiency of NSD3 impairs the antiviral innate immune response in vivo. Mechanistically, NSD3 enhances the transcription activity of IRF3 dependent on K366 monomethylation, which maintains IRF3 phosphorylation by promoting IRF3 dissociation of protein phosphatase PP1cc and consequently promotes type I interferon production. Our study reveals a critical role of NSD3-mediated IRF3 methylation in enhancing antiviral innate immunity.