Fos and Jun: the AP-1 connection

NR4A1 suppresses breast cancer growth by repressing c-Fos-mediated lipid and redox dyshomeostasis

The specific function of NR4A1 as a transcriptional regulator in cancer remains unclear. Here we report the biological effect of NR4A1 in suppressing breast cancer (BC) growth. We found that NR4A1 deficiency was correlated with BC progression in the clinic. Genetic deletion of NR4A1 in BC cells significantly promoted cellular proliferation and tumor growth. Moreover, global metabolome screening indicated that the deletion of NR4A1 resulted in tumor lipid remodeling and phospholipid accumulation, which was accompanied by increases in fatty acid and lipid uptake. In addition, NR4A1 knockout induced oxidative stress that aggravated redox balance disruption. Mechanistically, transcriptomic and epigenomic analyses revealed that NR4A1 restrained BC cell proliferation by directly interacting with c-Fos and competitively inhibiting c-Fos binding to the promoter of the target gene PRDX6, which is involved in lipid and redox homeostasis. Notably, we confirmed that the treatment of BC cells with the selective NR4A1 agonist cytosporone B significantly activated the expression of NR4A1, followed by increased interaction between NR4A1 and c-Fos, thereby interfering with c-Fos-mediated transcriptional regulation of BC cell growth. Thus, NR4A1 plays a vital role in reducing the c-Fos-induced activation of downstream signaling cascades in BC, suggesting that agents that activate NR4A1 may be potential therapeutic strategies.

The sperm quality in DIO male mice is linked to the NF-κB signaling and Ppp2ca expression in the hypothalamus

Recent studies show obesity correlated with reduced sperm quality in males, but the mechanism is unclear. In this study, diet-induced obese (DIO) male mice exhibited disrupted luteinizing hormone (LH) pulse release due to altered function of the hypothalamic-pituitary-gonadal (HPG) axis. This alteration was caused by activation of nuclear factor kappa B (NF-κB) signaling in the hypothalamus, which led to decreased sperm quality. RNA sequencing (RNA-seq) analysis of the hypothalamic arcuate nucleus (ARC) revealed a signaling network involving protein phosphatase 2 catalytic subunit alpha (Ppp2ca). This network disrupted LH pulse secretion by inhibiting Akt kinase (AKT) and cAMP responsive element-binding protein 1 (CREB1) activities, thereby reducing KiSS-1 metastasis-suppressor (Kiss1) expression. Furthermore, overexpression of the Ppp2ca gene in the ARC led to disrupted LH patterns and reduced sperm quality. These findings offer new insights into the molecular mechanisms underlying sperm quality decline in DIO male mice.

fos genes in mainly invertebrate model systems: A review of commonalities and some diversities

fos genes, transcription factors with a common basic region and leucine zipper domains binding to a consensus DNA sequence (TGA{}TCA), are evolutionarily conserved in eukaryotes. Homologs can be found in many different species from yeast to vertebrates. In yeast, the homologous GCN4 gene is required to mediate "emergency" situations like nutrient deprivation and the unfolded protein response. The C. elegans homolog fos-1 is required for reproduction and vulval development, as well as in adult homeostasis. In Drosophila melanogaster, there is also a sole fos homolog: the gene kayak, with five isoforms. The kayak locus has been studied in detail. It was originally described as embryonic lethal with a "dorsal open" phenotype. Since then, kayak has been shown to be required for oocyte maturation and as a source for piRNA; for early dorsoventral specification, macrophage function, dorsal closure, endoderm differentiation, and finally during metamorphosis in wing and eye-antennal development. In mammals there are multiple fos loci, each one with alternative splicing giving rise to multiple isoforms. Overall, mammalian fos genes are required for bone, cartilage and tooth formation, and in some instances for placental angiogenesis and retinal function. We review here mainly what is known about fos function in invertebrate model systems, especially during embryogenesis. We propose that fos genes, evolutionarily conserved transcription factors, evolved early during eukaryotic development, and from its inception as part of an environmental stress response machinery, were co-opted several times during development to regulate processes that may require similar cellular responses.

Photoreceptors inhibit pathological retinal angiogenesis through transcriptional regulation of Adam17 via c-Fos

Pathological retinal angiogenesis profoundly impacts visual function in vascular eye diseases, such as retinopathy of prematurity (ROP) in preterm infants and age-related macular degeneration in the elderly. While the involvement of photoreceptors in these diseases is recognized, the underlying mechanisms remain unclear. This study delved into the pivotal role of photoreceptors in regulating abnormal retinal blood vessel growth using an oxygen-induced retinopathy (OIR) mouse model through the c-Fos/A disintegrin and metalloprotease 17 (Adam17) axis. Our findings revealed a significant induction of c-Fos expression in rod photoreceptors, and c-Fos depletion in these cells inhibited pathological neovascularization and reduced blood vessel leakage in the OIR mouse model. Mechanistically, c-Fos directly regulated the transcription of Adam17 a shedding protease responsible for the production of bioactive molecules involved in inflammation, angiogenesis, and cell adhesion and migration. Furthermore, we demonstrated the therapeutic potential by using an adeno-associated virus carrying a rod photoreceptor-specific short hairpin RNA against c-fos which effectively mitigated abnormal retinal blood vessel overgrowth, restored retinal thickness, and improved electroretinographic (ERG) responses. In conclusion, this study highlights the significance of photoreceptor c-Fos in ROP pathology, offering a novel perspective for the treatment of this disease.

FOSL1's Oncogene Roles in Glioma/Glioma Stem Cells and Tumorigenesis: A Comprehensive Review

This review specifically examines the important function of the oncoprotein FOSL1 in the dimeric AP-1 transcription factor, which consists of FOS-related components. FOSL1 is identified as a crucial controller of invasion and metastatic dissemination, making it a potential target for therapeutic treatment in cancer patients. The review offers a thorough examination of the regulatory systems that govern the influence exerted on FOSL1. These include a range of changes that occur throughout the process of transcription and after the translation of proteins. We have discovered that several non-coding RNAs, such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), play a significant role in regulating FOSL1 expression by directly interacting with its mRNA transcripts. Moreover, an investigation into the functional aspects of FOSL1 reveals its involvement in apoptosis, proliferation, and migration. This work involves a comprehensive analysis of the complex signaling pathways that support these diverse activities. Furthermore, particular importance is given to the function of FOSL1 in coordinating the activation of several cytokines, such as TGF-beta, and the commencement of IL-6 and VEGF production in tumor-associated macrophages (TAMs) that migrate into the tumor microenvironment. There is a specific emphasis on evaluating the predictive consequences linked to FOSL1. Insights are now emerging on the developing roles of FOSL1 in relation to the processes that drive resistance and reliance on specific treatment methods. Targeting FOSL1 has a strong inhibitory effect on the formation and spread of specific types of cancers. Despite extensive endeavors, no drugs targeting AP-1 or FOSL1 for cancer treatment have been approved for clinical use. Hence, it is imperative to implement innovative approaches and conduct additional verifications.

The Wingless planar cell polarity pathway is essential for optimal activity-dependent synaptic plasticity

From fly to man, the Wingless (Wg)/Wnt signaling molecule is essential for both the stability and plasticity of the nervous system. The Drosophila neuromuscular junction (NMJ) has proven to be a useful system for deciphering the role of Wg in directing activity-dependent synaptic plasticity (ADSP), which, in the motoneuron, has been shown to be dependent on both the canonical and the noncanonical calcium Wg pathways. Here we show that the noncanonical planar cell polarity (PCP) pathway is an essential component of the Wg signaling system controlling plasticity at the motoneuron synapse. We present evidence that disturbing the PCP pathway leads to a perturbation in ADSP. We first show that a PCP-specific allele of disheveled (dsh) affects the de novo synaptic structures produced during ADSP. We then show that the Rho GTPases downstream of Dsh in the PCP pathway are also involved in regulating the morphological changes that take place after repeated stimulation. Finally, we show that Jun kinase is essential for this phenomenon, whereas we found no indication of the involvement of the transcription factor complex AP1 (Jun/Fos). This work shows the involvement of the neuronal PCP signaling pathway in supporting ADSP. Because we find that AP1 mutants can perform ADSP adequately, we hypothesize that, upon Wg activation, the Rho GTPases and Jun kinase are involved locally at the synapse, in instructing cytoskeletal dynamics responsible for the appearance of the morphological changes occurring during ADSP.

Iron overload promotes the progression of MLL-AF9 induced acute myeloid leukemia by upregulation of FOS

Systemic iron overload is a common clinical challenge leading to significantly serious complications in patients with acute myeloid leukemia (AML), which affects both the quality of life and the overall survival of patients. Symptoms can be relieved after iron chelation therapy in clinical practice. However, the roles and mechanisms of iron overload on the initiation and progression of leukemia remain elusive. Here we studied the correlation between iron overload and AML clinical outcome, and further explored the role and pathophysiologic mechanism of iron overload in AML by using two mouse models: an iron overload MLL-AF9-induced AML mouse model and a nude xenograft mouse model. Patients with AML had an increased ferritin level, particularly in the myelomonocytic (M4) or monocytic (M5) subtypes. High level of iron expression correlated with a worsened prognosis in AML patients and a shortened survival time in AML mice. Furthermore, iron overload increased the tumor load in the bone marrow (BM) and extramedullary tissues by promoting the proliferation of leukemia cells through the upregulation of FOS. Collectively, our findings provide new insights into the roles of iron overload in AML. Additionally, this study may provide a potential therapeutic target to improve the outcome of AML patients and a rationale for the prospective evaluation of iron chelation therapy in AML.

[Molecular mechanisms underlying the pathogenesis of septic multiple organ failure]

Sepsis is defined as the body's overwhelming and life-threatening response to infection that can lead to tissue damage, organ failure, and death. Since bacterial infection is one of the main causes of sepsis, appropriate antimicrobial therapy remains the cornerstone of sepsis and septic shock management. However, since sepsis is a multifaceted chaos involving inflammation and anti-inflammation disbalance leading to the unregulated widespread release of inflammatory mediators, cytokines, and pathogen-related molecules leading to system-wide organ dysfunction, the whole body control to prevent the progression of organ dysfunction is needed. In sepsis and septic shock, pathogen-associated molecular patterns (PAMPs), such as bacterial exotoxins, cause direct cellular damage and/or trigger an immune response in the host. PAMPs are recognized by pattern recognizing receptors (PRRs) expressed on immune-reactive cells. PRRs are also activated by host nuclear, mitochondrial, and cytosolic proteins, known as damage-associated molecular patterns (DAMPs) that are released from cells during sepsis. Thus, most PRRs respond to PAMPs or DAMPs by triggering activation of transcriptional factors, NF-κB, AP1, and STAT-3. On the other hand, sepsis leads to immune (lymphocytes and macrophages) and nonimmune (endothelial and epithelial cells) cell death. Apoptosis has been the major focus of research on cell death in sepsis, but autophagy, necrosis, necroptosis, pyroptosis, NETosis, and ferroptosis may also play an important role in this critical situation. The recent development in our understanding regarding the cellular pathogenesis of sepsis will help in developing new treatment of sepsis.

2022 Cannon lecture: an ode to signal transduction: how the growth hormone pathway revealed insight into height, malignancy, and obesity

Walter Cannon was a highly regarded American neurologist and physiologist with extremely broad interests. In the tradition of Cannon and his broad interests, we discuss our laboratory's multifaceted work in signal transduction over the past 40+ years. We show how our questioning of how growth hormone (GH) in the blood communicates with cells throughout the body to promote body growth and regulate body metabolism led to insight into not only body height but also important regulators of malignancy and body weight. Highlights include finding that 1) A critical initiating step in GH signal transduction is GH activating the GH receptor-associated tyrosine kinase JAK2; 2) GH activation of JAK2 leads to activation of a number of signaling proteins, including STAT transcription factors; 3) JAK2 is autophosphorylated on multiple tyrosines that regulate the activity of JAK2 and recruit signaling proteins to GH/GH receptor/JAK2 complexes; 4) Constitutively activated STAT proteins are associated with cancer; 5) GH activation of JAK2 recruits the adapter protein SH2B1 to GH/GH receptor/JAK2 complexes where it facilitates GH regulation of the actin cytoskeleton and motility; and 6) SH2B1 is recruited to other receptors in the brain, where it enhances satiety, most likely in part by regulating leptin action and neuronal connections of appetite-regulating neurons. These findings have led to increased understanding of how GH functions, as well as therapeutic interventions for certain cancer and obese individuals, thereby reinforcing the great importance of supporting basic research since one never knows ahead of time what important insight it can provide.

The potential of activator protein 1 (AP-1) in cancer targeted therapy

Activator protein-1 (AP-1) is a transcription factor that consists of a diverse group of members including Jun, Fos, Maf, and ATF. AP-1 involves a number of processes such as proliferation, migration, and invasion in cells. Dysfunctional AP-1 activity is associated with cancer initiation, development, invasion, migration and drug resistance. Therefore, AP-1 is a potential target for cancer targeted therapy. Currently, some small molecule inhibitors targeting AP-1 have been developed and tested, showing some anticancer effects. However, AP-1 is complex and diverse in its structure and function, and different dimers may play different roles in different type of cancers. Therefore, more research is needed to reveal the specific mechanisms of AP-1 in cancer, and how to select appropriate inhibitors and treatment strategies. Ultimately, this review summarizes the potential of combination therapy for cancer.

Determining the Potential Roles of Branched-Chain Amino Acids in the Regulation of Muscle Growth in Common Carp (Cyprinus carpio) Based on Transcriptome and MicroRNA Sequencing

Branched-chain amino acids (BCAAs) can be critically involved in skeletal muscle growth and body energy homeostasis. Skeletal muscle growth is a complex process; some muscle-specific microRNAs (miRNAs) are involved in the regulation of muscle thickening and muscle mass. Additionally, the regulatory network between miRNA and messenger RNA (mRNA) in the modulation of the role of BCAAs on skeletal muscle growth in fish has not been studied. In this study, common carp was starved for 14 days, followed by a 14-day gavage therapy with BCAAs, to investigate some of the miRNAs and genes that contribute to the regulation of normal growth and maintenance of skeletal muscle in response to short-term BCAA starvation stress. Subsequently, the transcriptome and small RNAome sequencing of carp skeletal muscle were performed. A total of 43,414 known and 1,112 novel genes were identified, in addition to 142 known and 654 novel miRNAs targeting 22,008 and 33,824 targets, respectively. Based on their expression profiles, 2,146 differentially expressed genes (DEGs) and 84 differentially expressed miRNA (DEMs) were evaluated. Kyoto Encyclopedia of Genes and Genome pathways, including the proteasome, phagosome, autophagy in animals, proteasome activator complex, and ubiquitin-dependent protein catabolic process, were enriched for these DEGs and DEMs. Our findings revealed the role of atg5, map1lc3c, ctsl, cdc53, psma6, psme2, myl9, and mylk in skeletal muscle growth, protein synthesis, and catabolic metabolism. Furthermore, miR-135c, miR-192, miR-194, and miR-203a may play key roles in maintaining the normal activities of the organism by regulating genes related to muscle growth, protein synthesis, and catabolism. This study on transcriptome and miRNA reveals the potential molecular mechanisms underlying the regulation of muscle protein deposition and provides new insights into genetic engineering techniques to improve common carp muscle development.

Guanxinning injection ameliorates cardiac remodeling in HF mouse and 3D heart spheroid models via p38/FOS/MMP1-mediated inhibition of myocardial hypertrophy and fibrosis

BACKGROUND

Heart failure (HF) is a cardiovascular disease with high morbidity and mortality. Guanxinning injection (GXNI) is clinically used for the treatment of coronary heart disease, but its therapeutic efficacy and potential mechanism for HF are poorly understood. This study aimed to evaluate the therapeutic potential of GXNI on HF, with a special focus on its role in myocardial remodeling.

METHODS

3D cardiac organoids and transverse aortic constriction (TAC) mouse models were established and utilized. Heart function and pathology were evaluated by echocardiography, hemodynamic examination, tail-cuff blood pressure and histopathology. Key targets and pathways regulated by GXNI in HF mouse heart were revealed via RNA-seq and network pharmacology analysis, and were verified by RT-PCR, Western blot, immunohistochemistry and immunofluorescence.

RESULTS

GXNI significantly inhibited cardiac hypertrophy and cells death. It protected mitochondrial function in cardiac hypertrophic organoids and markedly improved cardiac function in HF mice. Analysis of GXNI-regulated genes in HF mouse hearts revealed that IL-17A signaling in fibroblasts and the corresponding p38/c-Fos/Mmp1 pathway prominently mediated cardiac. Altered expressions of c-Fos, p38 and Mmp1 by GXNI in heart tissues and in cardiac organoids were validated by RT-PCR, WB, IHC, and IF. H&E and Masson staining confirmed that GXNI substantially ameliorated myocardial hypertrophy and fibrosis in HF mice and in 3D organoids.

CONCLUSION

GXNI inhibited cardiac fibrosis and hypertrophy mainly via down-regulating p38/c-Fos/Mmp1 pathway, thereby ameliorating cardiac remodeling in HF mice. Findings in this study provide a new strategy for the clinical application of GXNI in the treatment of heart failure.

AP-1-independent NFAT signaling maintains follicular T cell function in infection and autoimmunity

Coordinated gene expression programs enable development and function of T cell subsets. Follicular helper T (Tfh) cells coordinate humoral immune responses by providing selective and instructive cues to germinal center B cells. Here, we show that AP-1-independent NFAT gene expression, a program associated with hyporesponsive T cell states like anergy or exhaustion, is also a distinguishing feature of Tfh cells. NFAT signaling in Tfh cells, maintained by NFAT2 autoamplification, is required for their survival. ICOS signaling upregulates Bcl6 and induces an AP-1-independent NFAT program in primary T cells. Using lupus-prone mice, we demonstrate that genetic disruption or pharmacologic inhibition of NFAT signaling specifically impacts Tfh cell maintenance and leads to amelioration of autoantibody production and renal injury. Our data provide important conceptual and therapeutic insights into the signaling mechanisms that regulate Tfh cell development and function.

Common Trajectories of Highly Effective CD19-Specific CAR T Cells Identified by Endogenous T-cell Receptor Lineages

Current chimeric antigen receptor-modified (CAR) T-cell products are evaluated in bulk, without assessing functional heterogeneity. We therefore generated a comprehensive single-cell gene expression and T-cell receptor (TCR) sequencing data set using pre- and postinfusion CD19-CAR T cells from blood and bone marrow samples of pediatric patients with B-cell acute lymphoblastic leukemia. We identified cytotoxic postinfusion cells with identical TCRs to a subset of preinfusion CAR T cells. These effector precursor cells exhibited a unique transcriptional profile compared with other preinfusion cells, corresponding to an unexpected surface phenotype (TIGIT+, CD62Llo, CD27-). Upon stimulation, these cells showed functional superiority and decreased expression of the exhaustion-associated transcription factor TOX. Collectively, these results demonstrate diverse effector potentials within preinfusion CAR T-cell products, which can be exploited for therapeutic applications. Furthermore, we provide an integrative experimental and analytic framework for elucidating the mechanisms underlying effector development in CAR T-cell products.

SIGNIFICANCE

Utilizing clonal trajectories to define transcriptional potential, we find a unique signature of CAR T-cell effector precursors present in preinfusion cell products. Functional assessment of cells with this signature indicated early effector potential and resistance to exhaustion, consistent with postinfusion cellular patterns observed in patients. This article is highlighted in the In This Issue feature, p. 2007.

Combinatorial Treatment with PARP-1 Inhibitors and Cisplatin Attenuates Cervical Cancer Growth through Fos-Driven Changes in Gene Expression

Cervical cancer continues to be a significant cause of cancer-related deaths in women. The most common treatment for cervical cancer involves the use of the drug cisplatin in conjunction with other therapeutics. However, the development of cisplatin resistance in patients can hinder the efficacy of these treatments, so alternatives are needed. In this study, we found that PARP inhibitors (PARPi) could attenuate the growth of cells representing cervical adenocarcinoma and cervical squamous cell carcinoma. Moreover, a combination of PARPi with cisplatin increased cisplatin-mediated cytotoxicity in cervical cancer cells. This was accompanied by a dramatic alteration of the transcriptome. The FOS gene, which encodes the transcription factor Fos, was one of the most highly upregulated genes in the dual treatment condition, leading to increased Fos protein levels, greater Fos binding to chromatin, and the subsequent induction of Fos target genes. Increased expression of Fos was sufficient to hinder cervical cancer growth, as shown by ectopic expression of Fos in cervical cancer cells. Conversely, Fos knockdown enhanced cell growth. Collectively, these results indicate that by inducing FOS expression, PARPi treatment in combination with cisplatin leads to inhibition of cervical cancer proliferation, likely through a Fos-specific gene expression program.

IMPLICATIONS

Our observations, which link the gene regulatory effects of PARPi + cisplatin to the growth inhibitory effects of FOS expression in cervical cancer cells, strengthen the rationale for using PARPi with cisplatin as a therapy for cervical cancer.

Structural and Functional Properties of Activator Protein-1 in Cancer and Inflammation

The transcriptional machinery is composed of numerous factors that help to regulate gene expression in cells. The function and the fundamental role of transcription factors in different human diseases and cancer have been extensively researched. Activator protein-1 (AP-1) is an inducible transcription factor that consists of a diverse group of members including Jun, Fos, Maf, and ATF. AP-1 involves a number of processes such as proliferation, migration, and survival in cells. Dysfunctional AP-1 activity is seen in several diseases, especially cancer and inflammatory disorders. The AP-1 proteins are controlled by mitogen-activated protein kinases (MAPKs) and the NF-κB pathway. AP-1 inhibitors can be actively pursued as drug discovery targets in cancer therapy when used as a treatment to halt tumor progression. The consumption of phytochemicals in the diet is related to decreasing the incidence of cancer and proves to exhibit anticancer properties. Natural product targets AP-1 are effective cancer prevention and treatment options for various cancer types. Targeting AP-1 with natural products is an effective cancer treatment option for different cancer types. This review summarizes AP-1 subunit proteins, their structures, AP-1-related signaling, and its modulation by natural bioactive compounds.

Fluid shear stress-induced mechanotransduction in myoblasts: Does it depend on the glycocalyx?

Muscle stem cells (MuSCs) are involved in muscle maintenance and regeneration. Mechanically loaded MuSCs within their native niche undergo tensile and shear deformations, but how MuSCs sense mechanical stimuli and translate these into biochemical signals regulating function and fate is still poorly understood. We aimed to investigate whether the glycocalyx is involved in the MuSC mechanoresponse, and whether MuSC morphology affects mechanical loading-induced pressure, shear stress, and fluid velocity distribution. FSS-induced deformation of active proliferating MuSCs (myoblasts) with intact or degraded glycocalyx was assessed by live-cell imaging. Glycocalyx-degradation did not significantly affect nitric oxide production, but reduced FSS-induced myoblast deformation and modulated gene expression. Finite-element analysis revealed that the distribution of FSS-induced pressure, shear stress, and fluid velocity on myoblasts was non-uniform, and the magnitude depended on myoblast morphology and apex-height. In conclusion, our results suggest that the glycocalyx does not play a role in NO production in myoblasts but might impact mechanotransduction and gene expression, which needs further investigation. Future studies will unravel the underlying mechanism by which the glycocalyx affects FSS-induced myoblast deformation, which might be related to increased drag forces. Moreover, MuSCs with varying apex-height experience different levels of FSS-induced pressure, shear stress, and fluid velocity, suggesting differential responsiveness to fluid shear forces.

Cellular and molecular pathways controlling muscle size in response to exercise

From the discovery of ATP and motor proteins to synaptic neurotransmitters and growth factor control of cell differentiation, skeletal muscle has provided an extreme model system in which to understand aspects of tissue function. Muscle is one of the few tissues that can undergo both increase and decrease in size during everyday life. Muscle size depends on its contractile activity, but the precise cellular and molecular pathway(s) by which the activity stimulus influences muscle size and strength remain unclear. Four correlates of muscle contraction could, in theory, regulate muscle growth: nerve-derived signals, cytoplasmic calcium dynamics, the rate of ATP consumption and physical force. Here, we summarise the evidence for and against each stimulus and what is known or remains unclear concerning their molecular signal transduction pathways and cellular effects. Skeletal muscle can grow in three ways, by generation of new syncytial fibres, addition of nuclei from muscle stem cells to existing fibres or increase in cytoplasmic volume/nucleus. Evidence suggests the latter two processes contribute to exercise-induced growth. Fibre growth requires increase in sarcolemmal surface area and cytoplasmic volume at different rates. It has long been known that high-force exercise is a particularly effective growth stimulus, but how this stimulus is sensed and drives coordinated growth that is appropriately scaled across organelles remains a mystery.

The transcription factor reservoir and chromatin landscape in activated plasmacytoid dendritic cells

Background

Transcription factors (TFs) control gene expression by direct binding to regulatory regions of target genes but also by impacting chromatin landscapes and modulating DNA accessibility for other TFs. In recent years several TFs have been defined that control cell fate decisions and effector functions in the immune system. Plasmacytoid dendritic cells (pDCs) are an immune cell type with the unique capacity to produce high amounts of type I interferons quickly in response to contact with viral components. Hereby, this cell type is involved in anti-infectious immune responses but also in the development of inflammatory and autoimmune diseases. To date, the global TF reservoir in pDCs early after activation remains to be fully characterized.

Results

To fill this gap, we have performed a comprehensive analysis in naïve versus TLR9-activated murine pDCs in a time course study covering early timepoints after stimulation (2 h, 6 h, 12 h) integrating gene expression (RNA-Seq) and chromatin landscape (ATAC-Seq) studies. To unravel the biological processes underlying the changes in TF expression on a global scale gene ontology (GO) analyses were performed. We found that 70% of all genes annotated as TFs in the mouse genome (1014 out of 1636) are expressed in pDCs for at least one stimulation time point and are covering a wide range of TF classes defined by their specific DNA binding mechanisms. GO analysis revealed involvement of TLR9-induced TFs in epigenetic modulation, NFκB and JAK-STAT signaling, and protein production in the endoplasmic reticulum. pDC activation predominantly “turned on” the chromatin regions associated with TF genes. Our in silico analyses pointed at the AP-1 family of TFs as less noticed but possibly important players in these cells after activation. AP-1 family members exhibit (1) increased gene expression, (2) enhanced chromatin accessibility in their promoter region, and (3) a TF DNA binding motif that is globally enriched in genomic regions that were found more accessible in pDCs after TLR9 activation.

Conclusions

In this study we define the complete set of TLR9-regulated TFs in pDCs. Further, this study identifies the AP-1 family of TFs as potentially important but so far less well characterized regulators of pDC function.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12863-021-00991-2.

Gene fusions in vascular tumors and their underlying molecular mechanisms

INTRODUCTION

The group of vascular tumors contains many different entities, and is considered difficult by pathologists, as they often have overlapping histological characteristics. Chromosomal translocations have been identified in ~20% of mesenchymal tumors and are considered the drivers of tumor formation. Many translocations have been discovered over the past decade through next-generation sequencing. This technological advancement has also revealed several recurrent gene fusions in vascular tumors.

AREAS COVERED

This review will discuss the various vascular tumors for which recurrent gene fusions have been identified. The gene fusions and the presumed molecular mechanisms underlying tumorigenesis are shown, and potential implications for targeted therapies discussed. The identification of these gene fusions in vascular tumors has improved diagnostic accuracy, especially since several of these fusions can be easily detected using surrogate immunohistochemical markers.

EXPERT OPINION

The identification of gene fusions in a subset of vascular tumors over the past decade has improved diagnostic accuracy, and has provided the pathologists with novel diagnostic tools to accurately diagnose these often difficult tumors. Moreover, the increased understanding of the underlying molecular mechanisms can guide the development of targeted therapeutic strategies.

Myofiber stretch induces tensile and shear deformation of muscle stem cells in their native niche

Muscle stem cells (MuSCs) are requisite for skeletal muscle regeneration and homeostasis. Proper functioning of MuSCs, including activation, proliferation, and fate decision, is determined by an orchestrated series of events and communication between MuSCs and their niche. A multitude of biochemical stimuli are known to regulate MuSC fate and function. However, in addition to biochemical factors, it is conceivable that MuSCs are subjected to mechanical forces during muscle stretch-shortening cycles because of myofascial connections between MuSCs and myofibers. MuSCs respond to mechanical forces in vitro, but it remains to be proven whether physical forces are also exerted on MuSCs in their native niche and whether they contribute to the functioning and fate of MuSCs. MuSC deformation in their native niche resulting from mechanical loading of ex vivo myofiber bundles was visualized utilizing mT/mG double-fluorescent Cre-reporter mouse and multiphoton microscopy. MuSCs were subjected to 1 h pulsating fluid shear stress (PFSS) with a peak shear stress rate of 6.5 Pa/s. After PFSS treatment, nitric oxide, messenger RNA (mRNA) expression levels of genes involved in regulation of MuSC proliferation and differentiation, ERK 1/2, p38, and AKT activation were determined. Ex vivo stretching of extensor digitorum longus and soleus myofiber bundles caused compression as well as tensile and shear deformation of MuSCs in their niche. MuSCs responded to PFSS in vitro with increased nitric oxide production and an upward trend in iNOS mRNA levels. PFSS enhanced gene expression of c-Fos, Cdk4, and IL-6, whereas expression of Wnt1, MyoD, Myog, Wnt5a, COX2, Rspo1, Vangl2, Wnt10b, and MGF remained unchanged. ERK 1/2 and p38 MAPK signaling were also upregulated after PFSS treatment. We conclude that MuSCs in their native niche are subjected to force-induced deformations due to myofiber stretch-shortening. Moreover, MuSCs are mechanoresponsive, as evidenced by PFSS-mediated expression of factors by MuSCs known to promote proliferation.

Dopaminergic Control of Striatal Cholinergic Interneurons Underlies Cocaine-Induced Psychostimulation

Cocaine drastically elevates dopamine (DA) levels in the striatum, a brain region that is critical to the psychomotor and rewarding properties of the drug. DA signaling regulates intrastriatal circuits connecting medium spiny neurons (MSNs) with afferent fibers and interneurons. While the cocaine-mediated increase in DA signaling on MSNs is well documented, that on cholinergic interneurons (ChIs) has been more difficult to assess. Using combined pharmacological, chemogenetic, and cell-specific ablation approaches, we reveal that the D2R-dependent inhibition of acetylcholine (ACh) signaling is fundamental to cocaine-induced changes in behavior and the striatal genomic response. We show that the D2R-dependent control of striatal ChIs enables the motor, sensitized, and reinforcing properties of cocaine. This study highlights the importance of the DA- and D2R-mediated inhibitory control of ChIs activity in the normal functioning of striatal networks.

Neural substrates involved in the cognitive information processing in teleost fish

Over the last few decades, it has been shown that fish, comprising the largest group of vertebrates and in many respects one of the least well studied, possess many cognitive abilities comparable to those of birds and mammals. Despite a plethora of behavioural studies assessing cognition abilities and an abundance of neuroanatomical studies, only few studies have aimed to or in fact identified the neural substrates involved in the processing of cognitive information. In this review, an overview of the currently available studies addressing the joint research topics of cognitive behaviour and neuroscience in teleosts (and elasmobranchs wherever possible) is provided, primarily focusing on two fundamentally different but complementary approaches, i.e. ablation studies and Immediate Early Gene (IEG) analyses. More recently, the latter technique has become one of the most promising methods to visualize neuronal populations activated in specific brain areas, both during a variety of cognitive as well as non-cognition-related tasks. While IEG studies may be more elegant and potentially easier to conduct, only lesion studies can help researchers find out what information animals can learn or recall prior to and following ablation of a particular brain area.

Transcriptomic analyses of humans and mice provide insights into depression

Accumulating studies have been conducted to identify risk genes and relevant biological mechanisms underlying major depressive disorder (MDD). In particular, transcriptomic analyses in brain regions engaged in cognitive and emotional processes, e.g., the dorsolateral prefrontal cortex (DLPFC), have provided essential insights. Based on three independent DLPFC RNA-seq datasets of 79 MDD patients and 75 healthy controls, we performed differential expression analyses using two alternative approaches for cross-validation. We also conducted transcriptomic analyses in mice undergoing chronic variable stress (CVS) and chronic social defeat stress (CSDS). We identified 12 differentially expressed genes (DEGs) through both analytical methods in MDD patients, the majority of which were also dysregulated in stressed mice. Notably, the mRNA level of the immediate early gene FOS ( Fos proto-oncogene) was significantly decreased in both MDD patients and CVS-exposed mice, and CSDS-susceptible mice exhibited a greater reduction in Fos expression compared to resilient mice. These findings suggest the potential key roles of this gene in the pathogenesis of MDD related to stress exposure. Altered transcriptomes in the DLPFC of MDD patients might be, at least partially, the result of stress exposure, supporting that stress is a primary risk factor for MDD.

Gammacoronavirus Avian Infectious Bronchitis Virus and Alphacoronavirus Porcine Epidemic Diarrhea Virus Exploit a Cell-Survival Strategy via Upregulation of cFOS to Promote Viral Replication

Coronaviruses have evolved a variety of strategies to optimize cellular microenvironment for efficient replication. In this study, we report the induction of AP-1 transcription factors by coronavirus infection based on genome-wide analyses of differentially expressed genes in cells infected with avian coronavirus infectious bronchitis virus (IBV). Most members of the AP-1 transcription factors were subsequently found to be upregulated during the course of IBV and porcine epidemic diarrhea virus (PEDV) infection of cultured cells as well as in IBV-infected chicken embryos. Further characterization of the induction kinetics and functional roles of cFOS in IBV replication demonstrated that upregulation of cFOS at early to intermediate phases of IBV replication cycles suppresses IBV-induced apoptosis and promotes viral replication. Blockage of nuclear translocation of cFOS by peptide inhibitor NLSP suppressed IBV replication and apoptosis, ruling out the involvement of the cytoplasmic functions of cFOS in the replication of IBV. Furthermore, knockdown of ERK1/2 and inhibition of JNK and p38 kinase activities reduced cFOS upregulation and IBV replication. This study reveals an important function of cFOS in the regulation of coronavirus-induced apoptosis, facilitating viral replication.IMPORTANCE The ongoing pandemic of coronavirus disease 2019 (COVID-19), caused by a newly emerged zoonotic coronavirus (SARS-CoV-2), highlights the importance of coronaviruses as human and animal pathogens and our knowledge gaps in understanding the cellular mechanisms, especially mechanisms shared among human and animal coronaviruses, exploited by coronaviruses for optimal replication and enhanced pathogenicity. This study reveals that upregulation of cFOS, along with other AP-1 transcription factors, as a cell-survival strategy is such a mechanism utilized by coronaviruses during their replication cycles. Through induction and regulation of apoptosis of the infected cells at early to intermediate phases of the replication cycles, subtle but appreciable differences in coronavirus replication efficiency were observed when the expression levels of cFOS were manipulated in the infected cells. As the AP-1 transcription factors are multi-functional, further studies of their regulatory roles in proinflammatory responses may provide new insights into the pathogenesis and virus-host interactions during coronavirus infection.

Dentate Granule Cells Recruited in the Home Environment Display Distinctive Properties

The dentate granule cells (DGCs) play a crucial role in learning and memory. Many studies have described the role and physiological properties of these sparsely active neurons using different behavioral contexts. However, the morpho-functional features of DGCs recruited in mice maintained in their home cage (without training), considered as a baseline condition, have not yet been established. Using fosGFP transgenic mice, we observed ex vivo that DGCs recruited in animals maintained in the home cage condition are mature neurons that display a longer dendritic tree and lower excitability compared with non-activated cells. The higher GABA_A receptor-mediated shunting inhibition contributes to the lower excitability of DGCs activated in the home environment by shifting the input resistance towards lower values. Remarkably, that shunting inhibition is neither observed in non-activated DGCs nor in DGCs activated during training in virtual reality. In short, our results suggest that strong shunting inhibition and reduced excitability could constitute a distinctive neural signature of mature DGCs recruited in the context of the home environment.

Interaction between intensity and duration of acute exercise on neuronal activity associated with depression-related behavior in rats

We examined the activities of serotonin (5-HT) neurons in the dorsal raphe nucleus (DRN) and corticotropin-releasing factor (CRF) neurons in the hypothalamic paraventricular nucleus (PVN) during acute treadmill running at different speeds (control, low, high) and durations (15, 30, 60 min) in male Wistar rats using c-Fos/5-HT or CRF immunohistochemistry. We also performed elevated plus maze test (EPM) and forced swim test (FST) after acute treadmill running in rats. Acute treadmill running at low speed, regardless of exercise duration, significantly increased c-Fos expression in 5-HT neurons in the DRN compared with controls, whereas high-speed running significantly activated 5-HT neurons only at 60-min duration. In contrast, c-Fos expression in CRF neurons in the PVN was enhanced in an intensity-dependent manner, regardless of exercise duration. c-Fos expression in 5-HT neurons in the DRN induced by the acute treadmill running for 30 or 60 min, but not 15 min, was positively correlated with the time spent on the open arms in the EPM and was negatively correlated with the immobility time in the FST. These results suggest an interaction between exercise intensity and duration on the antidepressant effects of acute physical exercise.

FRA1 is essential for the maintenance of the oncogenic phenotype induced by in vitro long-term arsenic exposure

Arsenic induces oncogenic effects activating stress-related signalling pathways. This can result in the over-activation of the AP-1 protein, specifically its FRA1 component. FRA1 is a transcription factor frequently overexpressed in epithelial tumors, where it can regulate the expression of different target genes. Accordingly, FRA1 could play an essential role in the in vitro cell transformation induced by arsenic. FRA1 levels were monitored in MEF cells throughout their transformation stages during 40 weeks of long-term 2 μM arsenic exposure. Interestingly, the results show a progressive FRA1 overexpression with time (60-fold and 11-fold for mRNA and pFRA/non-pFRA1, respectively, at week 40), which may be responsible for the observed altered expression in the FRA1 downstream target genes Pten, Pdcd4, Tpm1, Tgfb1, Tgfb2, Zeb1, Zeb2, and Twist. The levels of MAPKs (ERK, p38, and JNK) and other known players upstream from FRA1 were assessed at equivalent time-points, and ERK, p38 and RAS were pinpointed as potential candidates involved in arsenic-induced FRA1 activation. Furthermore, FRA1 stable knockdown under chronic arsenic exposure settings elicits a remarkable impact on the features relative to the cells' oncogenic phenotype. Notably, FRA1 knockdown cells present a 30% diminished proliferation rate, a 50% lowered migration and invasion potential, a 50% reduction in senescence, and a 30-60% reduced tumorsphere-forming ability. This work is the first to demonstrate the important role of FRA1 in the development and aggressiveness of the in vitro transformed phenotype induced by long-term arsenic exposure.

Identification of SCARA3 with potential roles in metabolic disorders

Obesity is characterized by the expansion of adipose tissue which is partially modulated by adipogenesis. In the present study, we identified five differentially expressed genes by incorporating two adipogenesis-related datasets from the GEO database and their correlation with adipogenic markers. However, the role of scavenger receptor class A member 3 (SCARA3) in obesity-related disorders has been rarely reported. We found that Scara3 expression in old adipose tissue-derived mesenchymal stem cells (Ad-MSCs) was lower than it in young Ad-MSCs. Obese mice caused by deletion of the leptin receptor gene (db/db) or by a high-fat diet both showed reduced Scara3 expression in inguinal white adipose tissue. Moreover, hypermethylation of SCARA3 was observed in patients with type 2 diabetes and atherosclerosis. Data from the CTD database indicated that SCARA3 is a potential target for metabolic diseases. Mechanistically, JUN was predicted as a transcriptional factor of SCARA3 in different databases which is consistent with our further bioinformatics analysis. Collectively, our study suggested that SCARA3 is potentially associated with age-related metabolic dysfunction, which provided new insights into the pathogenesis and treatment of obesity as well as other obesity-associated metabolic complications.

Transcriptomic Changes in Endothelial Cells Triggered by Na,K-ATPase Inhibition: A Search for Upstream Na+i/K+i Sensitive Genes

Stimulus-dependent elevation of intracellular Ca²⁺ affects gene expression via well-documented calmodulin-mediated signaling pathways. Recently, we found that the addition of extra- and intracellular Ca²⁺ chelators increased, rather than decreased, the number of genes expressed, and that this is affected by the elevation of [Na⁺]_i/[K⁺]_i-ratio. This assumes the existence of a novel Na⁺_i/K⁺_i-mediated Ca²⁺_i-independent mechanism of excitation-transcription coupling. To identify upstream Na⁺_i/K⁺_i-sensitive genes, we examined the kinetics of transcriptomic changes in human umbilical vein endothelial cells (HUVEC) subjected to Na,K-ATPase inhibition by ouabain or K⁺-free medium. According to our data, microRNAs, transcription factors, and proteins involved in immune response and inflammation might be considered as key components of Na⁺_i/K⁺_i-mediated excitation-transcription coupling. Special attention was focused on the FOS gene and the possible mechanism of transcription regulation via G-quadruplexes, non-canonical secondary structures of nucleic acids, whose stability depends on [Na⁺]_i/[K⁺]_i-ratio. Verification of the [Na⁺]_i/[K⁺]_i-sensitive transcription regulation mechanism should be continued in forthcoming studies.

JunB can enhance the transcription of IL-8 in oral squamous cell carcinoma

Proteasome inhibitor MG132 was shown to enhance the secretion of interleukin 8 (IL-8) by various cells. The enhancement is regulated by the transcription factor activator protein-1 (AP-1) at the transcriptional level. AP-1 is a dimer formed by AP-1 family proteins. The purpose of the present study was to explore the combinations of the AP-1 family proteins that contribute to MG132-driven IL-8 secretion. Oral squamous cell carcinoma-derived cell lines, Ca9-22 and HSC3, were used to demonstrate their response to MG132. IL-8 secretion was augmented by MG132 in both cell lines. c-Jun expression was detected in both the cell lines, whereas c-Fos expression was detected only in the HSC3. The influence of MG132 stimulation on c-Jun and c-Fos expression was further examined by western blot analysis. c-Jun expression was increased by MG132 stimulation, whereas c-Fos expression was not detected even after MG132 stimulation. As JunB is reported to inhibit the transcriptional activity of the AP-1 complex, we speculated that the c-Jun homodimer should contribute to IL-8 enhancement. Expression vectors encoding wild type and c-Jun mutants, M17 and M22-23, respectively, were constructed and transfected into the Ca9-22 cells. In contrast to our expectations, MG132-induced IL-8 secretion was significantly reduced in all the transfectants suggesting that other c-Jun members might form homodimers with c-Jun and contribute to IL-8 enhancement. Transfection of the cells with c-Jun or JunB small hairpin RNA (shRNA) reduced IL-8 secretion up to 50% and 65% of the control shRNA transfectant. Furthermore, cotransfection of both shRNA almost completely inhibited the IL-8 secretion. These results indicate that JunB not only inhibits but also enhances the transcription of c-Jun targets in combination with c-Jun.

Cho S, Britton W, S. Kern T, Antonetti DA, Hellström A, E.H. Smith L. Targeting Neurovascular Interaction in Retinal Disorders

The tightly structured neural retina has a unique vascular network comprised of three interconnected plexuses in the inner retina (and choroid for outer retina), which provide oxygen and nutrients to neurons to maintain normal function. Clinical and experimental evidence suggests that neuronal metabolic needs control both normal retinal vascular development and pathological aberrant vascular growth. Particularly, photoreceptors, with the highest density of mitochondria in the body, regulate retinal vascular development by modulating angiogenic and inflammatory factors. Photoreceptor metabolic dysfunction, oxidative stress, and inflammation may cause adaptive but ultimately pathological retinal vascular responses, leading to blindness. Here we focus on the factors involved in neurovascular interactions, which are potential therapeutic targets to decrease energy demand and/or to increase energy production for neovascular retinal disorders.

Unfolded protein response-mediated modulation of mesenchymal stem cells

The endoplasmic reticulum (ER) receives unfolded proteins predestined for the secretory pathway or to be incorporated as transmembrane proteins. The ER has to accommodate the proper folding and glycosylation of these proteins and also to properly incorporate transmembrane proteins. However, under various circumstances, the proteins shuttling through the ER can be misfolded and undergo aggregation, which causes activation of the unfolded protein response (UPR). The UPR is mediated through three primary pathways: activating transcription factor-6, inositol-requiring enzyme-1 (IRE1), and PKR-like endoplasmic reticulum kinase, which up-regulate ER folding chaperones and temporarily suppress protein translation. The UPR can be both cytoprotective and/or cytotoxic depending on the duration of UPR activation and the type of host cell. Proteostasis controls stem cell function, while stress responses affect stem cell identity and differentiation. The present review aimed to explore and discuss the effects of the UPR pathways on mesenchymal stem cells.

New markers for regulation of transcription and macromolecule metabolic process in porcine oocytes during in vitro maturation

Oocyte maturation is essential for proper fertilization, embryo implantation and early development. While the physiological conditions of these processes are relatively well-known, its exact molecular mechanisms remain widely undiscovered. Oocyte growth, differentiation and maturation are therefore the subject of scientific debate. Precious literature has indicated that the oocyte itself serves a regulatory role in the mechanisms underlying these processes. Hence, the present study performed expression microarrays to analyze the complete transcriptome of porcine oocytes during their in vitro maturation (IVM). Pig material was used for experimentation, as it possesses similarities to the reproductive processes and general genetic proximities of Sus scrofa to human. Oocytes, isolated from the ovaries of slaughtered animals were assessed via the Brilliant Cresyl Blue test and directed to IVM. A number of oocytes were left to be analyzed as the ‘before IVM’ group. Oocyte mRNA was isolated and used for microarray analysis, which was subsequently validated via RT-qPCR. The current study particularly focused on genes belonging to ‘positive regulation of transcription, DNA-dependent’, ‘positive regulation of gene expression’, ‘positive regulation of macromolecule metabolic process’ and ‘positive regulation of transcription from RNA polymerase II promoter’ ontologies. FOS, VEGFA, ESR1, AR, CCND2, EGR2, ENDRA, GJA1, INHBA, IHH, INSR, APP, WWTR1, SMARCA1, NFAT5, SMAD4, MAP3K1, EGR1, RORA, ECE1, NR5A1, KIT, IKZF2, MEF2C, SH3D19, MITF and PSMB4 were all determined to be significantly altered (fold change, >|2|; P<0.05) among these groups, with their downregulation being observed after IVM. Genes with the most altered expressions were analyzed and considered to be potential markers of maturation associated with transcription regulation and macromolecule metabolism process.

Activator Protein-1 Transcriptional Activity Drives Soluble Micrograft-Mediated Cell Migration and Promotes the Matrix Remodeling Machinery

Impaired wound healing and tissue regeneration have severe consequences on the patient's quality of life. Micrograft therapies are emerging as promising and affordable alternatives to improve skin regeneration by enhancing the endogenous wound repair processes. However, the molecular mechanisms underpinning the beneficial effects of the micrograft treatments remain largely unknown. In this study, we identified the active protein-1 (AP-1) member Fos-related antigen-1 (Fra-1) to play a central role in the extracellular signal-regulated kinase- (ERK-) mediated enhanced cell migratory capacity of soluble micrograft-treated mouse adult fibroblasts and in the human keratinocyte cell model. Accordingly, we show that increased micrograft-dependent in vitro cell migration and matrix metalloprotease activity is abolished upon inhibition of AP-1. Furthermore, soluble micrograft treatment leads to increased expression and posttranslational phosphorylation of Fra-1 and c-Jun, resulting in the upregulation of wound healing-associated genes mainly involved in the regulation of cell migration. Collectively, our work provides insights into the molecular mechanisms behind the cell-free micrograft treatment, which might contribute to future advances in wound repair therapies.

Construction and evaluation of an efficient C-Jun siRNA to downregulate matrix metalloproteinase in human keratinocytes and fibroblasts under UV exposure

Background

C‐Jun and EGFR have not been explored as targets via the mechanism of RNA silencing. Hence, this study designed an efficient C‐Jun‐h‐825 small interfering RNA (siRNA) and investigated its effect on matrix metalloproteinase (MMP) and collagen expression in human keratinocytes exposed to UV radiation.

Methods

Five C‐Jun siRNAs were designed and screened for their ability to downregulate C‐Jun expression in human fibroblasts. These constructs were used to study changes in skin cancer‐related protein expression. HaCaT cells were grouped into 5‐carboxyfluorescien (FAM‐labeled) C‐Jun‐h‐825 siRNA + 2 hr prior irradiation; mock transfected + 2 hr prior irradiation; normal control; irradiation only for 2 hr; and Blank. Twenty‐four hours posttransfection, mRNA and protein levels of MMP‐I, MMP‐III, collagen‐I and collagen‐III were determined using standard RT‐PCR and ELISA kits.

Results

FAM‐labeled C‐Jun siRNA showed 80%–90% transfection efficiency. There was a significant increase in MMP‐I and MMP‐III and decrease in Col‐I and III mRNA levels when the cells were exposed to UV irradiation without siRNA transfection compared to blank (p < .05). This effect was reversed upon transfection with C‐Jun‐h‐825 (p < .01).

Conclusion

Thus, C‐Jun‐h‐825 siRNA might help restore skin collagen by decreasing MMP expression in cells exposed to UVA. Constructs and vectors designed herein have the potential to be translated into a treatment for photoaging induced skin cancer.

Expression and function of FRA1 protein in tumors

AP-1 is a dimeric complex that is composed of JUN, FOS, ATF and MAF protein families. FOS-related antigen 1 (FRA1) which encoded by FOSL1 gene, belongs to the FOS protein family, and mainly forms an AP-1 complex with the protein of the JUN family to exert an effect. Regulation of FRA1 occurs at levels of transcription and post-translational modification, and phosphorylation is the major post-translational modification. FRA1 is mainly regulated by the mitogen-activated protein kinases signaling pathway and is degraded by ubiquitin-independent proteasomes. FRA1 can affect biological functions, such as tumor proliferation, differentiation, invasion and apoptosis. Studies have demonstrated that FRA1 is abnormally expressed in many tumors and plays a relevant role, but the specific condition varies from the target organs. FRA1 is overexpressed in breast cancer, lung cancer, colorectal cancer, prostate cancer, nasopharyngeal cancer, thyroid cancer and other tumors. However, the expression of FRA1 is decreased in cervical cancer, and the expression of FRA1 in ovarian cancer and oral squamous cell carcinoma is still controversial. In this review, we present a detailed description of the regulatory factors and functions of FRA1, also, the expression of FRA1 in various tumors and its function in relative tumor.

Insight into the molecular function and transcriptional regulation of activator protein 1 (AP-1) components c-Jun/c-Fos ortholog in red lip mullet (Liza haematocheila)

The transcription factor, activator protein-1 (AP-1), is a dimeric protein and a downstream member of the mitogen-activated protein kinase (MAPK) signaling pathway. It regulates a wide array of functions including, cell proliferation, survival, differentiation, response to UV-irradiation, immune responses, and inflammatory conditions. AP-1 belongs to the basic leucine zipper (bZIP) protein family, which consists of members from Jun, Fos, Maf, and ATF subfamilies. In the present study, c-Jun and c-Fos homologs were identified from a transcriptome database of Liza haematocheila and designated as Lhc-Jun and Lhc-Fos. In both sequences, the signature bZIP domain was identified and also the DNA binding sites, dimerization sites, as well as the phosphorylation sites, were found to be highly conserved through evolution. Tissue distribution analysis revealed that both Lhc-Jun and Lhc-Fos transcripts were ubiquitously expressed in all examined tissues of healthy mullets. In order to determine the transcriptional modulations of Lhc-Jun and Lhc-Fos, challenge experiments were carried out using LPS, poly I:C, and L. garvieae. The qRT-PCR analysis revealed significant upregulation of Lhc-Jun and Lhc-Fos in blood, gill, liver, and spleen. This is the first study that explores the correlation between UV-irradiation and AP-1 ortholog expression in teleosts. Also, this is the first time that the functional characterization of the teleost c-Fos ortholog has been carried out. Sub-cellular localization of Lhc-Jun and Lhc-Fos was observed in the nucleus. AP-1-Luc reporter assays revealed significant higher luciferase activities in both Lhc-Jun and Lhc-Fos proteins compared to mock controls. These results strongly suggest that Lhc-Jun and Lhc-Fos might play a significant role in Liza haematocheila immunity by regulating AP-1 promoter sequences in immune and stress-related genes.

Transregulation of microRNA miR-21 promoter by AP-1 transcription factor in cervical cancer cells

BACKGROUND

Gene expression profiles have demonstrated that miR-21 expression is altered in almost all types of cancers and it has been classified as an oncogenic microRNA. Persistent HPV infection is the main etiologic agent in cervical cancer and induces genetic instability, including disruption of microRNA gene expression. In the present study, we analyzed the underlying mechanism of how AP-1 transcription factor can active miR-21 gene expression in cervical cancer cells.

METHODS

To identify that c-Fos and c-Jun regulate the expression of miR-21 we performed RT-qPCR and western blot assays. We analyzed the interaction of AP-1 with miR-21 promoter by EMSA and ChIP assays and determined the mechanism of its regulation by reporter construct plasmids. We identified the nuclear translocation of c-Fos and c-Jun by immunofluorescence microscopy assays.

RESULTS

We demonstrated that c-Fos and c-Jun proteins are expressed and regulate the expression of miR-21 in cervical cancer cells. DNA sequence analysis revealed the presence of AP-1 DNA-binding sites in the human miR-21 promoter region. EMSA analyses confirmed the interactions of the miR-21 upstream transcription factor AP-1. ChIP assays further showed the binding of c-Fos to AP-1 sequences from the miR-21 core promoter in vivo. Functional analysis of AP-1 sequences of miR-21 in reporter plasmids demonstrated that these sequences increase the miR-21 promoter activation.

CONCLUSIONS

Our findings suggest a physical interaction and functional cooperation between AP-1 transcription factor in the miR-21 promoter and may explain the effect of AP-1 on miR-21 gene expression in cervical cancer cells.

Lipid Metabolism in Neurons: A Brief Story of a Novel c-Fos-Dependent Mechanism for the Regulation of Their Synthesis

The mechanisms that coordinately regulate lipid synthesis in the nervous system together with the high rates of membrane biogenesis needed to support cell growth are largely unknown as are their subcellular site of synthesis. c-Fos, a well-known AP-1 transcription factor, has emerged as a unique protein with the capacity to associate to specific enzymes of the pathway of synthesis of phospholipids at the endoplasmic reticulum and activate their synthesis to accompany genomic decisions of growth. Herein, we discuss this effect of c-Fos in the context of neuronal differentiation and also with respect to pathologies of the nervous system such as the development and growth of tumors. We also provide insights into the sub-cellular sites where this regulation occurs at the endoplasmic reticulum membranes and the molecular mechanism by which c-Fos exerts this activity.

Inhibition of the TIRAP-c-Jun interaction as a therapeutic strategy for AP1-mediated inflammatory responses

Bacterial endotoxin-induced sepsis causes 30-40% of the deaths in the intensive care unit (ICU) globally, for which there is no pharmacotherapy. Lipopolysaccharide (LPS), a bacterial endotoxin, stimulates the Toll-like receptor (TLR)-4 signalling pathways to upregulate the expression of various inflammatory mediators. Here, we show that the TIRAP and c-Jun protein signalling complex forms in macrophages in response to LPS stimulation, which increases the AP1 transcriptional activity, thereby amplifying the expression of inflammatory mediators. Using a computer-aided molecular docking platform, we identified gefitinib as a putative inhibitor of the TIRAP-c-Jun signalling complex. Further, we demonstrated the ability of gefitinib to inhibit the interaction of TIRAP-c-Jun with in vitro experiments and with a mouse model of sepsis. Importantly, pre-treatment with gefitinib increased the survival of the mice that received a lethal dose of LPS compared to that of the controls. These findings verify the ability of gefitinib to directly disrupt the interaction of TIRAP and c-Jun, thereby inhibiting a major inflammatory response that is often observed in patients experiencing sepsis.

Identification of Triple-Negative Breast Cancer Genes and a Novel High-Risk Breast Cancer Prediction Model Development Based on PPI Data and Support Vector Machines

Triple-negative breast cancer (TNBC) is a special subtype of breast cancer that is difficult to treat. It is crucial to identify breast cancer-related genes that could provide new biomarkers for breast cancer diagnosis and potential treatment goals. In the development of our new high-risk breast cancer prediction model, seven raw gene expression datasets from the NCBI gene expression omnibus (GEO) database (GSE31519, GSE9574, GSE20194, GSE20271, GSE32646, GSE45255, and GSE15852) were used. Using the maximum relevance minimum redundancy (mRMR) method, we selected significant genes. Then, we mapped transcripts of the genes on the protein-protein interaction (PPI) network from the Search Tool for the Retrieval of Interacting Genes (STRING) database, as well as traced the shortest path between each pair of proteins. Genes with higher betweenness values were selected from the shortest path proteins. In order to ensure validity and precision, a permutation test was performed. We randomly selected 248 proteins from the PPI network for shortest path tracing and repeated the procedure 100 times. We also removed genes that appeared more frequently in randomized results. As a result, 54 genes were selected as potential TNBC-related genes. Using 14 out the 54 genes, which are potential TNBC associated genes, as input features into a support vector machine (SVM), a novel model was trained to predict high-risk breast cancer. The prediction accuracy of normal tissues and TNBC tissues reached 95.394%, and the predictions of Stage II and Stage III TNBC reached 86.598%, indicating that such genes play important roles in distinguishing breast cancers, and that the method could be promising in practical use. According to reports, some of the 54 genes we identified from the PPI network are associated with breast cancer in the literature. Several other genes have not yet been reported but have functional resemblance with known cancer genes. These may be novel breast cancer-related genes and need further experimental validation. Gene ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed to appraise the 54 genes. It was indicated that cellular response to organic cyclic compounds has an influence in breast cancer, and most genes may be related with viral carcinogenesis.

FOS, a Critical Downstream Mediator of PGR and EGF Signaling Necessary for Ovulatory Prostaglandins in the Human Ovary

Context

Fos null mice failed to ovulate and form a corpus luteum (CL) even when given exogenous gonadotropins, suggesting that ovarian Fos expression is critical for successful ovulation and CL formation. However, little is known about FOS in the human ovary.

Objectives

To determine the expression, regulation, and function of FOS in human periovulatory follicles.

Design/Participants

Timed periovulatory follicles were obtained from normally cycling women. Granulosa/lutein cells were collected from in vitro fertilization patients.

Main Outcome Measures

The in vivo expression after human chorionic gonadotropin (hCG) administration and in vitro regulation of FOS, JUN, JUNB, and JUND was evaluated at the mRNA and protein level. Binding of progesterone receptor (PGR) and FOS to their target genes was assessed by chromatin immunoprecipitation analyses. Prostaglandin E2 (PGE2) and progesterone were measured.

Results

The expression of FOS, JUNB, and JUND drastically increased in ovulatory follicles after hCG administration. In human granulosa/lutein cell cultures, hCG increased the expression of FOS and JUN proteins. Inhibitors of PGR and epidermal growth factor (EGF) receptors reduced hCG-induced increases in the expression and phosphorylation of FOS. PGR bound to the FOS gene. A selective FOS inhibitor blocked hCG-induced increases in PGE2 and the expression of prostaglandin (PG) synthases and transporters (PTGES, SLCO2A1, and ABCC1). FOS bound to the promoter regions of these genes.

Conclusions

The increase of FOS/activator protein 1 in human periovulatory follicles after hCG administration is mediated by collaborative actions of PGR and EGF signaling and critical for the upregulated expression of key ovulatory genes required for the rise in ovulatory PG in human granulosa cells.

Cloning and expression of a transcription factor activator protein-1 member identified from the swimming crab Portunus trituberculatus

Transcription activator proteins are regulatory proteins that bind to the promoter regions of target genes. Transcription activator protein-1 (AP-1) regulates numerous genes related to the immune system, apoptosis, and proliferation. In this study, the full-length cDNA of AP-1 from Portunus trituberculatus (PtAP-1) was identified by expressed sequence tag analysis and cDNA-end rapid amplification. The gene is 1183 bp and encodes a 256-amino acid protein with a predicted molecular mass and isoelectric point of 28.96 kDa and 8.90, respectively. PtAP-1 showed the highest expression level in the gonad tissue and the lowest expression level in blood, hemocyte, muscle, hepatopancreas, and gill, during the first 6 h of low-salinity stimulation (10%). Additionally, we observed steady decreases in PtAP-1 mRNA expression in the gill, but at 12 h, expression was initially upregulated, followed by a significant decrease until restoration to baseline levels at 48 h. Additionally, Vibrio alginolyticus challenge resulted in significant upregulation of PtAP-1 expression in the first 6 h, which was maintained at high levels for 48 h. From 48 to 72 h, we observed decreases in PtAP-1 levels, although they remained significantly higher than those detected at baseline. These results suggested that PtAP-1 is involved in the immune response and osmoregulation of crustaceans.

Efficiency of All-Trans Retinoic Acid on Gastric Cancer: A Narrative Literature Review

Gastric cancer (GC) is the third leading cause of cancer-related death worldwide with a five-year survival rate of around 25%, and 4% when diagnosed at a metastatic stage. Cancer stem cells (CSC) have recently been characterized as being responsible for resistance to radio/chemotherapies and metastasis formation, opening up perspectives for new targeted therapies. Those CSCs express biomarkers such as cluster of differentiation 44 (CD44) and display high aldehyde dehydrogenase activity that converts vitamin A-derived retinal into retinoic acids. All-trans retinoic acid (ATRA), which has pro-differentiating properties, has revolutionized the prognosis of acute promyelotic leukemia by increasing its remission rate from 15% to 85%. Recent studies have started to show that ATRA also has an anti-tumoral role on solid cancers such as GC. The purpose of this review is therefore to summarize the work that evaluated the effects of ATRA in GC and to evaluate whether its anti-cancerous action involves gastric CSCs targeting. It has been demonstrated that ATRA can block the cell cycle, enhance apoptosis, and decrease gastric CSCs properties in GC cell lines, tumorspheres, and patient-derived xenograft mice models. Therefore, retinoids and new synthetic retinoids seem to be a promising step forward in targeted therapy of gastric CSC in combination with existing chemotherapies. Future studies should probably focus on these points.

The role of AP-1 in self-sufficient proliferation and migration of cancer cells and its potential impact on an autocrine/paracrine loop

Activating protein-1 (AP-1) family members, especially Fra-1 and c-Jun, are highly expressed in invasive cancers and can mediate enhanced migration and proliferation. The aim of this study was to explore the significance of elevated levels of AP-1 family members under conditions that restrict growth. We observed that invasive MDA-MB-231 cells express high levels of Fra-1, c-Jun, and Jun-D during serum starvation and throughout the cell cycle compared to non-tumorigenic and non-invasive cell lines. We then analyzed Fra-1 levels in additional breast and other cancer cell lines. We found breast and lung cancer cells with higher levels of Fra-1 during serum starvation had relatively higher ability to proliferate and migrate under these conditions. Utilizing a dominant negative construct of AP-1, we demonstrated that proliferation and migration of MDA-MB-231 in the absence of serum requires AP-1 activity. Finally, we observed that MDA-MB-231 cells secrete factors(s) that induce Fra-1 expression and migration in non-tumorigenic and non-metastatic cells and that both the expression of and response to these factors require AP-1 activity. These results suggest the presence of an autocrine/paracrine loop that maintains high Fra-1 levels in aggressive cancer cells, enhancing their proliferative and metastatic ability and affecting neighbors to alter the tumor environment.

Fos metamorphoses: Lessons from mutants in model organisms

The Fos oncogene gene family is evolutionarily conserved throughout Eukarya. Fos proteins characteristically have a leucine zipper and a basic region with a helix-turn-helix motif that binds DNA. In vertebrates, there are several Fos homologs. They can homo- or hetero-dimerize via the leucine zipper domain. Fos homologs coupled with other transcription factors, like Jun oncoproteins, constitute the Activator Protein 1 (AP-1) complex. From its original inception as an oncogene, the subsequent finding that they act as transcription factors binding DNA sequences known as TRE, to the realization that they are activated in many different scenarios, and to loss-of-function analysis, the Fos proteins have traversed a multifarious path in development and physiology. They are instrumental in 'immediate early genes' responses, and activated by a seemingly myriad assemblage of different stimuli. Yet, the majority of these studies were basically gain-of-function studies, since it was thought that Fos genes would be cell lethal. Loss-of-function mutations in vertebrates were recovered later, and were not cell lethal. In fact, c-fos null mutations are viable with developmental defects (osteopetrosis and myeloid lineage abnormalities). It was then hypothesized that vertebrate genomes exhibit partial redundancy, explaining the 'mild' phenotypes, and complicating assessment of complete loss-of-function phenotypes. Due to its promiscuous activation, fos genes (especially c-fos) are now commonly used as markers for cellular responses to stimuli. fos homologs high sequence conservation (including Drosophila) is advantageous as it allows critical assessment of fos genes functions in this genetic model. Drosophila melanogaster contains only one fos homolog, the gene kayak. kayak mutations are lethal, and allow study of all the processes where fos is required. The kayak locus encodes several different isoforms, and is a pleiotropic gene variously required for development involving cell shape changes. In general, fos genes seem to primarily activate programs involved in cellular architectural rearrangements and cell shape changes.

What does the Fos say? Using Fos-based approaches to understand the contribution of stress to substance use disorders

Despite extensive research efforts, drug addiction persists as a largely unmet medical need. Perhaps the biggest challenge for treating addiction is the high rate of recidivism. While many factors can promote relapse in abstinent drug users, the contribution of stress is particularly problematic, as stress is uncontrollable and pervasive in the lives of those struggling with addiction. Thus, understanding the neurocircuitry that underlies the influence of stress on drug seeking is critical for guiding treatment. Preclinical research aimed at defining this neurocircuitry has, in part, relied upon the use of experimental approaches that allow visualization of cellular and circuit activity that corresponds to stressor-induced drug seeking in rodent relapse models. Much of what we have learned about the mechanisms that mediate stressor-induced relapse has been informed by studies that have used the expression of the immediate early gene, cfos, or its protein product, Fos, as post-mortem activity markers. In this review we provide an overview of the rodent models used to study stressor-induced relapse and briefly summarize what is known about the underlying neurocircuitry before describing the use of cfos/Fos-based approaches. In addition to reviewing findings obtained using this approach, its advantages and limitations are considered. Moreover, new techniques that leverage the expression profile of cfos to tag and manipulate cells based on their activity patterns are discussed. The intent of the review is to guide the interpretation of old and design of new studies that utilize cfos/Fos-based strategies to study the neurocircuitry that contributes to stress-related drug use.