GAS1 induces cell death through an intrinsic apoptotic pathway

Suppression of apoptosis impairs phalangeal joint formation in the pathogenesis of brachydactyly type A1

Apoptosis occurs during development when a separation of tissues is needed. Synovial joint formation is initiated at the presumptive site (interzone) within a cartilage anlagen, with changes in cellular differentiation leading to cavitation and tissue separation. Apoptosis has been detected in phalangeal joints during development, but its role and regulation have not been defined. Here, we use a mouse model of brachydactyly type A1 (BDA1) with an IhhE95K mutation, to show that a missing middle phalangeal bone is due to the failure of the developing joint to cavitate, associated with reduced apoptosis, and a joint is not formed. We showed an intricate relationship between IHH and interacting partners, CDON and GAS1, in the interzone that regulates apoptosis. We propose a model in which CDON/GAS1 may act as dependence receptors in this context. Normally, the IHH level is low at the center of the interzone, enabling the "ligand-free" CDON/GAS1 to activate cell death for cavitation. In BDA1, a high concentration of IHH suppresses apoptosis. Our findings provided new insights into the role of IHH and CDON in joint formation, with relevance to hedgehog signaling in developmental biology and diseases.

Characterization of the pattern of expression of Gas1 in the kidney during postnatal development in the rat

Growth Arrest-Specific 1 (Gas1) is a pleiotropic protein with different functions, in the adult kidney Gas1 acts as an endogenous inhibitor of cell proliferation but it is also necessary for the maintenance and proliferation of Renal Progenitor Cells (RPC) during early development, thus it fulfills important functions in the adult kidney. However, it is not known whether or not Gas1 is expressed during postnatal development, a critical stage for renal maturation. For this reason, the main objective of this work was to characterize the expression pattern of Gas1 in the different regions of the kidney by immunofluorescence and Western blot analysis during the postnatal development of the rat. We found that Gas1 is present and has a differential expression pattern in the various regions of the nephron during postnatal development. We observed that the highest levels of expression of Gas1 occur in the adult, however, Gas1 is also expressed in RPC and interestingly, the expression of RPC markers such as the Neural cell adhesion molecule (NCAM) and Cluster of differentiation 24 (CD24) were found to have an inverse pattern of expression to Gas1 (decreases as the kidney matures) during postnatal renal maturation, this indicates a role for Gas1 in the regulation of renal cell proliferation at this stage of development.

Expression of growth arrest specific 1 (Gas1) in the distal tubules and collecting ducts in normal kidney and in the early stages of diabetic nephropathy

The Growth Arrest-Specific protein 1 (Gas1) has been recently described in kidney as an endogenous inhibitor of cell proliferation in mesangial cells and with an important role in the maintenance of nephron progenitor cells. Furthermore, the expression of Gas1 was demonstrated in NCAM + progenitor parietal cells of Bowman's capsule. Thus, the aim of this study was to analyze the expression of Gas1 in the collecting ducts (CD) of healthy rats and to examine whether high glucose levels modify its expression during the early stages of diabetes in STZ-treated rats. Immunofluorescence reveals that principal cells AQP2 + express Gas1 in both healthy and diabetic conditions. Western blot from enriched fractions of medullary CD suggests that diabetes promotes the increase of Gas1. AQP2 + cells are also positive for the expression of CD24 and CD1133 in diabetic rats. In addition, diabetes modifies the cell morphology in the CD and favors the increase of principal cells (AQP2+/Gas1+), induces a significant decrease of intercalated cells (V-ATPase+/Gas1-) and the presence of intermediate cells (Gas1+/V-ATPase+) which express both principal and intercalated cell markers. The expression of Gas1 in the distal tubules was also determined by immunofluorescence, western blot and ELISA in diabetic rats. The results identify Gas1 as a specific marker of principal cells in healthy and diabetic rats and suggest that diabetes promotes the expression of Gas1. Gas1 may have an important role in the maintenance and differentiation to principal cells in the CD during early stages of diabetes.

The cytotoxicity of PM2.5 and its effect on the secretome of normal human bronchial epithelial cells

Exposure to airborne fine particulate matter (PM_2.5) induced various adverse health effects, such as metabolic syndrome, systemic inflammation, and respiratory disease. Many works have studied the effects of PM_2.5 exposure on cells through intracellular proteomics analyses. However, changes of the extracellular proteome under PM_2.5 exposure and its correlation with PM_2.5-induced cytotoxicity still remain unclear. Herein, the cytotoxicity of PM_2.5 on normal human bronchial epithelia cells (BEAS-2B cells) was evaluated, and the secretome profile of BEAS-2B cells before and after PM_2.5 exposure was investigated. A total of 83 proteins (58 upregulated and 25 downregulated) were differentially expressed in extracellular space after PM_2.5 treatment. Notably, we found that PM_2.5 promoted the release of several pro-apoptotic factors and induced dysregulated secretion of extracellular matrix (ECM) constituents, showing that the abnormal extracellular environment attributed to PM_2.5-induced cell damage. This study provided a secretome data for the deep understanding of the molecular mechanism underlying PM_2.5-caused human bronchial epithelia cell damage.

Simultaneous Treatment with Soluble Forms of GAS1 and PTEN Reduces Invasiveness and Induces Death of Pancreatic Cancer Cells

Introduction

Pancreatic carcinoma cells exhibit a pronounced tendency to invade along and through intra and extrapancreatic nerves, even during the early stages of the disease, a phenomenon called perineural invasion (PNI). Thus, we sought to determine the effects of the simultaneous expression of soluble forms of GAS1 and PTEN (tGAS1 and PTEN-L) inhibiting tumor growth and invasiveness.

Materials and Methods

We employed a lentiviral system to simultaneously express tGAS1 and PTEN-L; in order to determine the effects of the treatments, cell viability and apoptosis as well as the expression of the transgenes by ELISA and intracellular signaling as ascertained by the activation of AKT and ERK1/2 were measured; cell invasiveness was determined using a Boyden chamber assay; and the effects of the treatment were measured in vivo in a mouse model.

Results

In the present work, we show that the combined treatment with tGAS1 and PTEN-L inhibits the growth of pancreatic cancer cells, by reducing the activities of both AKT and ERK 1/2, decreases cell invasiveness, and restrains tumor growth in a mouse model.

Conclusion

The combined administration of tGAS1 and PTEN-L could be a valuable adjunct therapy for the treatment of pancreatic cancer.

The systemic administration of neural stem cells expressing an inducible and soluble form of growth arrest specific 1 inhibits mammary gland tumor growth and the formation of metastases

BACKGROUND AIMS

Metastasis to different organs is the major cause of death in breast cancer patients. The poor clinical prognosis and lack of successful treatments for metastatic breast cancer patients demand the development of new tumor-selective therapies. Thus, it is necessary to develop treatments capable of releasing therapeutic agents to both primary tumors and metastases that avoid toxic side effects in normal tissue, and neural stem cells are an attractive vehicle for tracking tumor cells and delivering anti-cancer agents. The authorspreviously demonstrated that a soluble form of growth arrest specific 1 (GAS1) inhibits the growth of triple-negative breast tumors and glioblastoma.

METHODS

In this study, the authors engineered ReNcell CX (EMD Millipore, Temecula, CA, USA) neural progenitor cells to express truncated GAS1 (tGAS1) under a tetracycline/on inducible system using lentiviral vectors.

RESULTS

Here the authors show that treatment with ReNcell-tGAS1 in combination with tetracycline decreased primary tumor growth and inhibited the formation of metastases in tumor-bearing mice by diminishing the phosphorylation of AKT and ERK1/2 in orthotopic mammary gland tumors. Moreover, the authors observed that ReNcell-tGAS1 prolonged the survival of 4T1 tumor-bearing mice.

CONCLUSIONS

These data suggest that the delivery of tGAS1 by ReNcell cells could be an effective adjuvant for the treatment of triple-negative breast cancer.

Time-dependent cytokine and chemokine changes in mouse cerebral cortex following a mild traumatic brain injury

Traumatic brain injury (TBI) is a serious global health problem, many individuals live with TBI-related neurological dysfunction. A lack of biomarkers of TBI has impeded medication development. To identify new potential biomarkers, we time-dependently evaluated mouse brain tissue and neuronally derived plasma extracellular vesicle proteins in a mild model of TBI with parallels to concussive head injury. Mice (CD-1, 30–40 g) received a sham procedure or 30 g weight-drop and were euthanized 8, 24, 48, 72, 96 hr, 7, 14 and 30 days later. We quantified ipsilateral cortical proteins, many of which differed from sham by 8 hours post-mTBI, particularly GAS-1 and VEGF-B were increased while CXCL16 reduced, 23 proteins changed in 4 or more of the time points. Gene ontology pathways mapped from altered proteins over time related to pathological and physiological processes. Validation of proteins identified in this study may provide utility as treatment response biomarkers.

Attenuation of Cardiac Ischaemia-reperfusion Injury by Treatment with Hydrogen-rich Water

Background: Hydrogen has been shown to exert a bioactive effect on the myocardium. This study examined the signalling pathways for hydrogen attenuating ischaemia-reperfusion injury.

Methods: In total, 20 male Wistar rats were evaluated for the effects of hydrogen-rich water on ischaemia-reperfusion in hearts. Left ventricular tissue was taken for screening and analysis of active protein factors by protein chip technology. The enrichment of the KEGG pathway was obtained by using the Gene Ontology (GO) enrichment principle. The expression of JAK2, STAT1, STAT3, p-STAT1, p-JAK2, p-STAT3 in rat myocardium was detected by Western blot analysis and immunohistochemistry. The apoptosis rates of the control and hydrogen-rich water groups were detected by TUNEL staining.

Results: The expression levels of 25 proteins, including five transduction pathways, were downregulated in the hydrogen-rich water group. The expression levels of p-JAK2/JAK2, p-STAT3/STAT3 were upregulated in the hydrogen-rich water group compared with the control group, and p-STAT1/STAT1 was downregulated in the hydrogen-rich water group compared with the control group. Furthermore, the apoptosis rate was significantly decreased in the hydrogen-rich water group, as well.

Conclusion: Hydrogen-rich water may inhibit the apoptosis of cardiomyocytes after ischaemia-reperfusion by upregulating the expression of the JAK2-STAT3 signalling pathway, which reduces ischaemia-reperfusion injury.

Analysis of long non-coding RNA and mRNA expression in bovine macrophages brings up novel aspects of Mycobacterium avium subspecies paratuberculosis infections

Paratuberculosis is a major disease in cattle that severely affects animal welfare and causes huge economic losses worldwide. Development of alternative diagnostic methods is of urgent need to control the disease. Recent studies suggest that long non-coding RNAs (lncRNAs) play a crucial role in regulating immune function and may confer valuable information about the disease. However, their role has not yet been investigated in cattle with respect to infection towards Paratuberculosis. Therefore, we investigated the alteration in genomic expression profiles of mRNA and lncRNA in bovine macrophages in response to Paratuberculosis infection using RNA-Seq. We identified 397 potentially novel lncRNA candidates in macrophages of which 38 were differentially regulated by the infection. A total of 820 coding genes were also significantly altered by the infection. Co-expression analysis of lncRNAs and their neighbouring coding genes suggest regulatory functions of lncRNAs in pathways related to immune response. For example, this included protein coding genes such as TNIP3, TNFAIP3 and NF-κB2 that play a role in NF-κB2 signalling, a pathway associated with immune response. This study advances our understanding of lncRNA roles during Paratuberculosis infection.

A survey of metastasis suppressors in Metazoa

Metastasis suppressors are genes/proteins involved in regulation of one or more steps of the metastatic cascade while having little or no effect on tumor growth. The list of putative metastasis suppressors is constantly increasing although thorough understanding of their biochemical mechanism(s) and evolutionary history is still lacking. Little is known about tumor-related genes in invertebrates, especially non-bilaterians and unicellular relatives of animals. However, in the last few years we have been witnessing a growing interest in this subject since it has been shown that many disease-related genes are already present in simple non-bilateral animals and even in their unicellular relatives. Studying human diseases using simpler organisms that may better represent the ancestral conditions in which the specific disease-related genes appeared could provide better understanding of how those genes function. This review represents a compilation of published literature and our bioinformatics analysis to gain a general insight into the evolutionary history of metastasis-suppressor genes in animals (Metazoa). Our survey suggests that metastasis-suppressor genes emerged in three different periods in the evolution of Metazoa: before the origin of metazoans, with the emergence of first animals and at the origin of vertebrates.

Annexin A1, Annexin A2, and Dyrk 1B are upregulated during GAS1-induced cell cycle arrest

GAS1 is a pleiotropic protein that has been investigated because of its ability to induce cell proliferation, cell arrest, and apoptosis, depending on the cellular or the physiological context in which it is expressed. At this point, we have information about the molecular mechanisms by which GAS1 induces proliferation and apoptosis; but very few studies have been focused on elucidating the mechanisms by which GAS1 induces cell arrest. With the aim of expanding our knowledge on this subject, we first focused our research on finding proteins that were preferentially expressed in cells arrested by serum deprivation. By using a proteomics approach and mass spectrometry analysis, we identified 17 proteins in the 2-DE protein profile of serum deprived NIH3T3 cells. Among them, Annexin A1 (Anxa1), Annexin A2 (Anxa2), dual specificity tyrosine-phosphorylation-regulated kinase 1B (Dyrk1B), and Eukaryotic translation initiation factor 3, F (eIf3f) were upregulated at transcriptional the level in proliferative NIH3T3 cells. Moreover, we demonstrated that Anxa1, Anxa2, and Dyrk1b are upregulated at both the transcriptional and translational levels by the overexpression of GAS1. Thus, our results suggest that the upregulation of Anxa1, Anxa2, and Dyrk1b could be related to the ability of GAS1 to induce cell arrest and maintain cell viability. Finally, we provided further evidence showing that GAS1 through Dyrk 1B leads not only to the arrest of NIH3T3 cells but also maintains cell viability.

Expression of Gas1 in Mouse Brain: Release and Role in Neuronal Differentiation

Growth arrest-specific 1 (Gas1) is a pleiotropic protein that induces apoptosis of tumor cells and has important roles during development. Recently, the presence of two forms of Gas1 was reported: one attached to the cell membrane by a GPI anchor; and a soluble extracellular form shed by cells. Previously, we showed that Gas1 is expressed in different areas of the adult mouse CNS. Here, we report the levels of Gas1 mRNA protein in different regions and analyzed its expressions in glutamatergic, GABAergic, and dopaminergic neurons. We found that Gas1 is expressed in GABAergic and glutamatergic neurons in the Purkinje-molecular layer of the cerebellum, hippocampus, thalamus, and fastigial nucleus, as well as in dopaminergic neurons of the substantia nigra. In all cases, Gas1 was found in the cell bodies, but not in the neuropil. The Purkinje and the molecular layers show the highest levels of Gas1, whereas the granule cell layer has low levels. Moreover, we detected the expression and release of Gas1 from primary cultures of Purkinje cells and from hippocampal neurons as well as from neuronal cell lines, but not from cerebellar granular cells. In addition, using SH-SY5Y cells differentiated with retinoic acid as a neuronal model, we found that extracellular Gas1 promotes neurite outgrowth, increases the levels of tyrosine hydroxylase, and stimulates the inhibition of GSK3β. These findings demonstrate that Gas1 is expressed and released by neurons and promotes differentiation, suggesting an important role for Gas1 in cellular signaling in the CNS.

Genetic interactions between the hedgehog co-receptors Gas1 and Boc regulate cell proliferation during murine palatogenesis

Abnormal regulation of Sonic hedgehog (Shh) signaling has been described in a variety of human cancers and developmental anomalies, which highlights the essential role of this signaling molecule in cell cycle regulation and embryonic development. Gas1 and Boc are membrane co-receptors for Shh, which demonstrate overlapping domains of expression in the early face. This study aims to investigate potential interactions between these co-receptors during formation of the secondary palate. Mice with targeted mutation in Gas1 and Boc were used to generate Gas1; Boc compound mutants. The expression of key Hedgehog signaling family members was examined in detail during palatogenesis via radioactive in situ hybridization. Morphometric analysis involved computational quantification of BrdU-labeling and cell packing; whilst TUNEL staining was used to assay cell death. Ablation of Boc in a Gas1 mutant background leads to reduced Shh activity in the palatal shelves and an increase in the penetrance and severity of cleft palate, associated with failed elevation, increased proliferation and reduced cell death. Our findings suggest a dual requirement for Boc and Gas1 during early development of the palate, mediating cell cycle regulation during growth and subsequent fusion of the palatal shelves.

Thiamine antagonists trigger p53-dependent apoptosis in differentiated SH-SY5Y cells

Accumulating evidences suggest that p53 is a key coordinator of cellular events triggered by oxidative stress often associated with the impairment in thiamine metabolism and its functions. However, there are limited data regarding the pursuant feedback between p53 transactivation and thiamine homeostasis. Impairment in thiamine metabolism can be induced experimentally via interference with the thiamine uptake and/or inhibition of the thiamin pyrophosphate–dependent enzymes using thiamine antagonists - amprolium (AM), oxythiamine (OT) or pyrithiamine (PT). We found that exposure of neuronally differentiated SH-SY5Y cells to AM, OT and PT triggered upregulation of p53 gene expression, post-translational modification of p53 via phosphorylation and activation of p53 DNA-binding activity. Phosphorylation of p53 at Ser20 was equally efficient in upregulation of thiamine transporter 1 (THTR1) by all antagonists. However, induction of the expressions of the pyruvate dehydrogenase E1 component subunit beta (PDHB) and oxoglutarate dehydrogenase (OGDH) required dual phosphorylation of p53 at Ser9 and Ser20, seen in cells treated with PT and OT. Moreover, pretreatment of the cells with a decoy oligonucleotide carrying wild-type p53-response element markedly attenuated OT-induced THTR1, PDHB and OGDH gene expression suggesting an important role of p53 in transactivation of these genes. Finally, analysis of gene and metabolic networks showed that OT triggers cell apoptosis through the p53-dependent intrinsic pathway.

Gas1 up-regulation is inducible and contributes to cell apoptosis in reactive astrocytes in the substantia nigra of LPS and MPTP models

Background

Reactive astrogliosis is a remarkable pathogenetic hallmark of the brains of Parkinson’s disease (PD) patients, but its progressive fate and regulation mechanisms are poorly understood. In this study, growth arrest specific 1 (Gas1), a tumor growth suppressor oncogene, was identified as a novel modulator of the cell apoptosis of reactive astrocytes in primary culture and the injured substantia nigra.

Methods

Animal models and cell cultures were utilized in the present study. Lipopolysaccharide (LPS)- and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated animal models were used to detect Gas1 expression in the brain via immunohistochemistry and western blot. Cell cultures were performed to analyze Gas1 functions in the viability and apoptosis of reactive astrocytes and SH-SY5Y cells by double labeling, CCK-8, LDH, TUNEL, flow cytometry, and siRNA knockdown methods.

Results

Gas1 expressions were significantly elevated in the majority of the reactive astrocytes of the brains with LPS or MPTP insults. In the injured substantia nigras, GFAP-positive astrocytes exhibited higher levels of cleaved caspase-3. In cell culture, the up-regulated Gas1 expression induced apoptosis of reactive astrocytes that were insulted by LPS in combination with interferon-γ and tumor necrosis factor-a. This effect was confirmed through siRNA knockdown of Gas1 gene expression. Finally and interestingly, the potential underlying signaling pathways were evidently related to an increase in the Bax/Bcl-2 ratio, the abundant generation of reactive oxygen species and the activation of cleaved caspase-3.

Conclusions

This study demonstrated that the up-regulation of inducible Gas1 contributed to the apoptosis of reactive astrocytes in the injured nigra. Gas1 signaling may function as a novel regulator of astrogliosis and is thus a potential intervention target for inflammatory events in PD conditions.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0643-2) contains supplementary material, which is available to authorized users.

GAS1 is present in the cerebrospinal fluid and is expressed in the choroid plexus of the adult rat

Growth arrest specific 1 (GAS1) is a GPI-anchored protein that inhibits proliferation when overexpressed in tumors but during development it promotes proliferation and survival of different organs and tissues. This dual ability is caused by its capacity to interact both by inhibiting the signaling induced by the glial cell line-derived neurotrophic factor and by facilitating the activity of the sonic hedgehog pathway. GAS1 is expressed as membrane bound in different organs and as a secreted form by glomerular mesangial cells. In the developing central nervous system, GAS1 is found in neural progenitors; however, it continues to be expressed in the adult brain. Here, we demonstrate that soluble GAS1 is present in the cerebrospinal fluid (CSF) and it is expressed in the choroid plexus (CP) of the adult rat, the main producer of CSF. Additionally, we confirm the presence of GAS1 in blood plasma and liver of the adult rat, the principal source of blood plasma proteins. The pattern of expression of GAS1 is perivascular in both the CP and the liver. In vitro studies show that the fibroblast cell line NIH/3T3 expresses one form of GAS1 and releases two soluble forms into the supernatant. Briefly, in the present work, we show the presence of GAS1 in adult rat body fluids focusing in the CSF and the CP, and suggest that secreted GAS1 exists as two different isoforms.

Gas1 Knockdown Increases the Neuroprotective Effect of Glial Cell-Derived Neurotrophic Factor Against Glutamate-Induced Cell Injury in Human SH-SY5Y Neuroblastoma Cells

Growth arrest-specific 1 (Gas1) protein acts as an inhibitor of cell growth and a mediator of cell death in nervous system during development and is also re-expressed in adult neurons during excitotoxic insult. Due to its structural similarity to the glial cell-derived neurotrophic factor family receptors α (GFRα), Gas1 is likely to interfere with the neuroprotective effect of GDNF. In the present study, we investigated the expression profile of Gas1 during glutamate insults in human SH-SY5Y neuroblastoma cells as well as the influence of Gas1 inhibition on the protective effect of GDNF against glutamate-induced cell injury. Our data showed that Gas1 expression was significantly increased with the treatment of glutamate in SH-SY5Y cells. The silencing of Gas1 by small interfering RNA promoted the protective effect of GDNF against glutamate-induced cytotoxicity as well as cell apoptosis, which effect was likely mediated through activating Akt/PI3 K-dependent cell survival signaling pathway and inhibiting mitochondrial-dependent cell apoptosis signaling pathway via Bad dephosphorylation blockade. In summary, this study showed the synergistic effect of Gas1 inhibition and GDNF against glutamate-induced cell injury in human SH-SY5Y neuroblastoma cells, which information might significantly contribute to better understanding the function of Gas1 in neuronal cells and form the basis of the therapeutic development of GDNF in treating human neurodegenerative diseases in the future.

Iron-induced oxidative stress activates AKT and ERK1/2 and decreases Dyrk1B and PRMT1 in neuroblastoma SH-SY5Y cells

Iron is essential for proper neuronal functioning; however, excessive accumulation of brain iron is reported in Parkinson's, Alzheimer's, Huntington's diseases and amyotrophic lateral sclerosis. This indicates that dysregulated iron homeostasis is involved in the pathogenesis of these diseases. To determinate the effect of iron on oxidative stress and on cell survival pathways, such as AKT, ERK1/2 and DyrK1B, neuroblastoma SH-SY5Y cells were exposed to different concentration of FeCl2 (iron). We found that iron induced cell death in SH-SY5Y cells in a concentration-dependent manner. Detection of iNOS and 3-nitrotyrosine confirms the presence of increased nitrogen species. Furthermore, we found a decrease of catalase and protein arginine methyl-transferase 1 (PRMT1). Interestingly, iron increased the activity of ERK and AKT and reduced DyrK1B. Moreover, after FeCl2 treatment, the transcription factors c-Jun and pSmad1/5 were activated. These results indicate that the presence of high levels of iron increase the vulnerability of neurons to oxidative stress.

MiR-184 Regulates Proliferation in Nucleus Pulposus Cells by Targeting GAS1

OBJECTIVE

The precise mechanism of nucleus pulposus proliferation in the degeneration of the intervertebral disk pathogenesis remains to be implicated. MicroRNAs (MiRNAs) are a class of 18-22 nucleotides, which are small, noncoding RNAs that inhibit protein translation by binding to the 3'-UTR of target gene. Recent studies have shown that miRNAs play a crucial role in various cell biologies such as cell proliferation, invasion, migration, and cell cycle. However, the role of miR-184 in nucleus pulposus proliferation is still unknown.

METHOD

qRT-PCR was performed to measure the expression of miR-184. CCK-8 assay, qRT-PCR, and Western blot were used to measure the functional role of miR-184 in nucleus pulposus (NP) cells. Western blot and Luciferase assays were done to find the miR-184 target gene.

RESULT

We demonstrated that expression of miR-184 was upregulated in degenerative NP tissues compared with that in the control NP tissues, and the expression of miR-184 was positively correlated with disk degeneration grade. We identified Growth Arrest Specific Gene 1 (GAS1) as a direct target gene of miR-184 in NP cells, and ectopic expression of miR-184 promoted NP cells proliferation. In addition, we found that GAS1 expression was downregulated in degenerative NP tissues compared with that in the control NP tissues and the GAS1 expression was inversely correlated with the grade of disk degeneration. Moreover, we demonstrated that miR-184 overexpression could induce AKT phosphorylation and ectopic expression of GAS1 decreased the miR-184 overexpressing NP cells proliferation.

CONCLUSION

These results demonstrated that miR-184 and the GAS1/Akt pathway may be a potential therapeutic target for intervertebral disc degeneration.

Growth Arrest Specific-1 (GAS1) Is a C/EBP Target Gene That Functions in Ovulation and Corpus Luteum Formation in Mice

Ovulation and luteinization are initiated in preovulatory follicles by the luteinizing hormone (LH) surge; however, the signaling events that mediate LH actions in these follicles remain incompletely defined. Two key transcription factors that are targets of LH surge are C/EBPalpha and C/EBPbeta, and their depletion in granulosa cells results in complete infertility. Microarray analyses of these mutant mice revealed altered expression of a number of genes, including growth arrest specific-1 (Gas1). To investigate functions of Gas1 in ovulation- and luteinization-related processes, we crossed Cyp19a1-Cre and Gas1^flox/flox mice to conditionally delete Gas1 in granulosa and cumulus cells. While expression of Gas1 is dramatically increased in granulosa and cumulus cells around 12–16 h post-human chorionic gonadotropin (hCG) stimulation in wild-type mice, this increase is abolished in Cebpa/b double mutant and in Gas1 mutant mice. GAS1 is also dynamically expressed in stromal cells of the ovary independent of C/EBPalpha/beta. Female Gas1 mutant mice are fertile, exhibit enhanced rates of ovulation, increased fertility, and higher levels of Areg and Lhcgr mRNA in granulosa cells. The morphological appearance and vascularization of corpora lutea appeared normal in these mutant females. Interestingly, levels of mRNA for a number of genes (Cyp11a1, Star, Wnt4, Prlr, Cd52, and Sema3a) associated with luteinization are decreased in corpora lutea of Gas1 mutant mice as compared with controls at 24 h post-hCG; these differences were no longer detectable by 48 h post-hCG. The C/EBP target Gas1 is induced in granulosa cells and is associated with ovulation and luteinization.

RNA sequencing provides exquisite insight into the manipulation of the alveolar macrophage by tubercle bacilli

Mycobacterium bovis, the agent of bovine tuberculosis, causes an estimated $3 billion annual losses to global agriculture due, in part, to the limitations of current diagnostics. Development of next-generation diagnostics requires a greater understanding of the interaction between the pathogen and the bovine host. Therefore, to explore the early response of the alveolar macrophage to infection, we report the first application of RNA-sequencing to define, in exquisite detail, the transcriptomes of M. bovis-infected and non-infected alveolar macrophages from ten calves at 2, 6, 24 and 48 hours post-infection. Differentially expressed sense genes were detected at these time points that revealed enrichment of innate immune signalling functions, and transcriptional suppression of host defence mechanisms (e.g., lysosome maturation). We also detected differentially expressed natural antisense transcripts, which may play a role in subverting innate immune mechanisms following infection. Furthermore, we report differential expression of novel bovine genes, some of which have immune-related functions based on orthology with human proteins. This is the first in-depth transcriptomics investigation of the alveolar macrophage response to the early stages of M. bovis infection and reveals complex patterns of gene expression and regulation that underlie the immunomodulatory mechanisms used by M. bovis to evade host defence mechanisms.

The Internalization of Neurotensin by the Low-Affinity Neurotensin Receptors (NTSR2 and vNTSR2) Activates ERK 1/2 in Glioma Cells and Allows Neurotensin-Polyplex Transfection of tGAS1

Glioblastoma is the most malignant primary brain tumor and is very resistant to treatment; hence, it has a poor prognosis. Neurotensin receptor type 1 (NTSR1) plays a key role in cancer malignancy and has potential therapeutic applications. However, the presence and function of neurotensin (NTS) receptors in glioblastoma is not clearly established. RT-PCR assays showed that healthy (non-tumor) astroglial cells and C6 glioma cells express NTSR2 and its isoform (vNTSR2) rather than NTSR1. In glioma cells, NTS promotes the phosphorylation of extracellular signal-regulated kinases 1/2 (ERK 1/2), an effect that was completely abolished by blocking the internalization of the NTS/NTSR complex. We demonstrated pharmacologically that the internalization is dependent on the activation of NTSR2 receptors and it was prevented by levocabastine, a NTSR2 receptor antagonist. The internalization of NTSR2 and vNTSR2 was further demonstrated by its ability to mediate gene transfer (transfection) via the NTS-polyplex system. Expression of reporter transgenes and of the pro-apoptotic soluble form of growth arrest specific 1 (tGAS1) was observed in glioma cells. A significant reduction on the viability of C6 cells was determined when tGAS1 was transfected into glioma cells. Conversely, astroglial cells could neither internalize NTS nor activate ERK 1/2 and could not be transfected by the NTS-polyplex. These results demonstrate that the internalization process of NTSR2 receptors is a key regulator necessary to trigger the activation of the ERK 1/2. Our data support a new internalization pathway in glioma C6 cells that involve NTSR2/vNTSR2, which can be used to selectively transfer therapeutic genes using the NTS-polyplex system.

Growth Arrest Specific 1 (Gas1) Gene Overexpression in Liver Reduces the In Vivo Progression of Murine Hepatocellular Carcinoma and Partially Restores Gene Expression Levels

The prognosis of hepatocellular carcinoma patients is usually poor, the size of tumors being a limiting factor for surgical treatments. Present results suggest that the overexpression of Gas1 (growth arrest specific 1) gene reduces the size, proliferating activity and malignancy of liver tumors. Mice developing diethylnitrosamine-induced hepatocellular carcinoma were subjected to hydrodynamic gene delivery to overexpress Gas1 in liver. This treatment significantly (p < 0.05) reduced the number of large tumors, while the difference in the total number of lesions was not significant. Moreover, the number of carcinoma foci in the liver and the number of lung metastases were reduced. These results are related with the finding that overexpression of Gas1 in Hepa 1-6 cells arrests cell cycle before S phase, with a significant (p < 0.01) and concomitant reduction in the expression of cyclin E2 gene. In addition, a triangular analysis of microarray data shows that Gas1 overexpression restores the transcription levels of 150 genes whose expression was affected in the diethylnitrosamine-induced tumors, thirteen of which are involved in the hedgehog signaling pathway. Since the in vivo Gas1 gene delivery to livers of mice carrying hepatocellular carcinoma reduces the size and proliferating activity of tumors, partially restoring the transcriptional profile of the liver, the present study opens promising insights towards a therapeutic approach for hepatocellular carcinoma.

Mitochondrial Membrane Potential and Nuclear and Gene Expression Changes During Human Disc Cell Apoptosis: In Vitro and In Vivo Annulus Findings

STUDY DESIGN

A study using cultured human annulus cells and human annular tissue.

OBJECTIVE

To further explore and define mitochondrial mechanisms related to disc cell apoptosis in vitro and in vivo.

SUMMARY OF BACKGROUND DATA

Mitochondrial-dependent intrinsic signaling pathways are a well-recognized component of apoptosis (programmed cell death). Disc cell apoptosis is important because it is a major mechanism by which cell numbers decrease during disc degeneration. Our objective was to further explore and define mitochondrial mechanisms related to disc cell apoptosis.

METHODS

High-content screening techniques were used to study nuclear morphology and mitochondrial membrane potentials in cultured annulus cells. Gene expression in annulus tissue was studied with microarray analysis.

RESULTS

Cultured cells showed significantly increased nuclear size (an indicator of apoptosis) with increasing Thompson grade (P < 0.00001 by analysis of variance). A significant negative correlation for mitochondrial potential (which results from the difference in electrical potential generated by the electrochemical gradient across the inner membrane of the mitochondrion) versus Thompson grade was identified in cultured human annulus cells in control conditions (r = 0.356, P < 0.0001). When exposed to the K ionophore valinomycin at sublethal levels to induce apoptosis, a significant reduction in mitochondrial potential was identified versus nontreated cells. Gene expression patterns in more degenerated Thompson grade III, IV, and V discs versus healthier grade I and II discs showed significant upregulation of a number of genes with well-recognized apoptosis roles in mitochondrial potential decline (ITM2B, beta-2-microglobulin, and cathepsin B, DAP, GAS1, and PDCD5) and TNF-α associations (cathepsin B, RAC1, and PPT1).

CONCLUSION

Data presented here show the in vivo expression of apoptosis-related genes associated with the loss of mitochondrial membrane integrity and decreased mitochondrial membrane potential with increasing Thompson scores. These data, which mimic our novel, direct cell-based in vitro findings, stress the importance of mitochondrial changes related to apoptosis and TNF-α during human disc degeneration.

LEVEL OF EVIDENCE

N/A.

Denoising perturbation signatures reveal an actionable AKT-signaling gene module underlying a poor clinical outcome in endocrine-treated ER+ breast cancer

Background

Databases of perturbation gene expression signatures and drug sensitivity provide a powerful framework to develop personalized medicine approaches, by helping to identify actionable genomic markers and subgroups of patients who may benefit from targeted treatments.

Results

Here we use a perturbation expression signature database encompassing perturbations of over 90 cancer genes, in combination with a large breast cancer expression dataset and a novel statistical denoising algorithm, to help discern cancer perturbations driving most of the variation in breast cancer gene expression. Clustering estrogen receptor positive cancers over the perturbation activity scores recapitulates known luminal subtypes. Analysis of individual activity scores enables identification of a novel cancer subtype, defined by a 31-gene AKT-signaling module. Specifically, we show that activation of this module correlates with a poor prognosis in over 900 endocrine-treated breast cancers, a result we validate in two independent cohorts. Importantly, breast cancer cell lines with high activity of the module respond preferentially to PI3K/AKT/mTOR inhibitors, a result we also validate in two independent datasets. We find that at least 34 % of the downregulated AKT module genes are either mediators of apoptosis or have tumor suppressor functions.

Conclusions

The statistical framework advocated here could be used to identify gene modules that correlate with prognosis and sensitivity to alternative treatments. We propose a randomized clinical trial to test whether the 31-gene AKT module could be used to identify estrogen receptor positive breast cancer patients who may benefit from therapy targeting the PI3K/AKT/mTOR signaling axis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-015-0630-4) contains supplementary material, which is available to authorized users.

Activated Nrf2 impairs liver regeneration in mice by activation of genes involved in cell-cycle control and apoptosis

The nuclear factor erythroid-derived 2, like 2 (Nrf2) transcription factor is a key regulator of the antioxidant defense system, and pharmacological activation of Nrf2 is a promising strategy for prevention of toxin-induced liver damage. However, the consequences of Nrf2 activation on liver regeneration (LR) have not been determined. To address this question, we generated mice expressing a constitutively active Nrf2 (caNrf2) mutant in hepatocytes. Expression of the transgene did not affect liver homeostasis. Surprisingly, however, there was no beneficial effect of Nrf2 activation on CCl4 -induced liver injury and fibrosis. Most important, LR after partial hepatectomy was impaired in caNrf2-transgenic mice as a result of delayed hepatocyte proliferation and enhanced apoptosis of these cells after liver injury. Mechanistically, this involved up-regulation of the cyclin-dependent kinase inhibitor p15 and the proapoptotic protein Bcl2l11 (Bim). Using chromatin immunoprecipitation, we show that the p15 and Bcl2l11 genes are direct targets of Nrf2, which are activated under hyperproliferative conditions in the liver.

CONCLUSION

Activated Nrf2 delays proliferation and induces apoptosis of hepatocytes in the regenerating liver. These negative effects of Nrf2 activation on LR should be considered when Nrf2-activating compounds are used for prevention of liver damage.

Down-regulation of miR-34a alleviates mesangial proliferation in vitro and glomerular hypertrophy in early diabetic nephropathy mice by targeting GAS1

AIMS

Diabetic nephropathy (DN) is a major diabetic complication characterized by mesangial proliferation and glomerular hypertrophy. MicroRNAs might play an important role in these pathological processes. The aim of this study is to examine the possible association of miR-34a as one of the microRNAs with DN and underlying mechanisms in vitro and in vivo.

METHODS

According to previous results of microarray which compared the different microRNAs between diabetic and normal control mice, miR-34a was chosen and its expression was detected by qRT-PCR. Cell viability was then assessed using Cell Counting Kit-8 (CCK8) and 5-ethynyl-20-deoxyuridine (EDU) incorporation. Antagomir was injected in db/db mice to down regulate miR-34a. Average diameter of glomeruli was analyzed by periodic acid-Schiff (PAS) stain of kidney. Luciferase gene report assay was then performed to identify the target gene of miR-34a. Additional immunoblotting and immunohistochemical analyses were implemented to verify the expression level of growth arrest-specific 1 (GAS1).

RESULTS

MiR-34a expression level was increased under high glucose condition in vitro and in vivo. Down-regulation of miR-34a inhibits mice mesangial cells (MMCs) proliferation in vitro and alleviates glomerular hypertrophy in vivo. GAS1 was proved to be the target of miR-34a through luciferase report. Moreover, up-regulation of GAS1 expression was observed in the presence of miR-34a antagomir as compared with miR-34a antagomir-NC in high-glucose-treated MMCs and db/db mice, respectively.

CONCLUSIONS

MiR-34a regulated mesangial proliferation and glomerular hypertrophy by directly inhibiting GAS1 in early DN.

The membrane proteome of sensory cilia to the depth of olfactory receptors

In the nasal cavity, the nonmotile cilium of olfactory sensory neurons (OSNs) constitutes the chemosensory interface between the ambient environment and the brain. The unique sensory organelle facilitates odor detection for which it includes all necessary components of initial and downstream olfactory signal transduction. In addition to its function in olfaction, a more universal role in modulating different signaling pathways is implicated, for example, in neurogenesis, apoptosis, and neural regeneration. To further extend our knowledge about this multifunctional signaling organelle, it is of high importance to establish a most detailed proteome map of the ciliary membrane compartment down to the level of transmembrane receptors. We detached cilia from mouse olfactory epithelia via Ca(2+)/K(+) shock followed by the enrichment of ciliary membrane proteins at alkaline pH, and we identified a total of 4,403 proteins by gel-based and gel-free methods in conjunction with high resolution LC/MS. This study is the first to report the detection of 62 native olfactory receptor proteins and to provide evidence for their heterogeneous expression at the protein level. Quantitative data evaluation revealed four ciliary membrane-associated candidate proteins (the annexins ANXA1, ANXA2, ANXA5, and S100A5) with a suggested function in the regulation of olfactory signal transduction, and their presence in ciliary structures was confirmed by immunohistochemistry. Moreover, we corroborated the ciliary localization of the potassium-dependent Na(+)/Ca(2+) exchanger (NCKX) 4 and the plasma membrane Ca(2+)-ATPase 1 (PMCA1) involved in olfactory signal termination, and we detected for the first time NCKX2 in olfactory cilia. Through comparison with transcriptome data specific for mature, ciliated OSNs, we finally delineated the membrane ciliome of OSNs. The membrane proteome of olfactory cilia established here is the most complete today, thus allowing us to pave new avenues for the study of diverse molecular functions and signaling pathways in and out of olfactory cilia and thus to advance our understanding of the biology of sensory organelles in general.

MiR-34a targets GAS1 to promote cell proliferation and inhibit apoptosis in papillary thyroid carcinoma via PI3K/Akt/Bad pathway

MicroRNAs (miRNAs) are fundamental regulators of cell proliferation, differentiation, and apoptosis, and are implicated in tumorigenesis of many cancers. MiR-34a is best known as a tumor suppressor through repression of growth factors and oncogenes. Growth arrest specific1 (GAS1) protein is a tumor suppressor that inhibits cancer cell proliferation and induces apoptosis through inhibition of RET receptor tyrosine kinase. Both miR-34a and GAS1 are frequently down-regulated in various tumors. However, it has been reported that while GAS1 is down-regulated in papillary thyroid carcinoma (PTC), miR-34a is up-regulated in this specific type of cancer, although their potential roles in PTC tumorigenesis have not been examined to date. A computational search revealed that miR-34a putatively binds to the 3'-UTR of GAS1 gene. In the present study, we confirmed previous findings that miR-34a is up-regulated and GAS1 down-regulated in PTC tissues. Further studies indicated that GAS1 is directly targeted by miR-34a. Overexpression of miR-34a promoted PTC cell proliferation and colony formation and inhibited apoptosis, whereas knockdown of miR-34a showed the opposite effects. Silencing of GAS1 had similar growth-promoting effects as overexpression of miR-34a. Furthermore, miR-34a overexpression led to activation of PI3K/Akt/Bad signaling pathway in PTC cells, and depletion of Akt reversed the pro-growth, anti-apoptotic effects of miR-34a. Taken together, our results demonstrate that miR-34a regulates GAS1 expression to promote proliferation and suppress apoptosis in PTC cells via PI3K/Akt/Bad pathway. MiR-34a functions as an oncogene in PTC.

The proform of glia cell line-derived neurotrophic factor: a potentially biologically active protein

Growing evidences have revealed that the proforms of several neurotrophins including nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT3), by binding to p75 neurotrophin receptor and sortilin, could induce neuronal apoptosis and are implicated in the pathogenesis of various neurodegenerative diseases. The glial cell line-derived neurotrophic factor (GDNF), one of the most potent useful neurotrophic factors for the treatment of Parkinson's disease (PD), is firstly synthesized as the proform (proGDNF) like other neurotrophin NGF, BDNF, and NT3. However, little is known about proGDNF expression and secretion under physiological as well as pathological states in vivo or in vitro. In this study, we investigated the expression profile and dynamic changes of proGDNF in brains of aging and PD animal models, with the interesting finding that proGDNF was a predominant form of GDNF with molecular weight of about 36 kDa by reducing and nonreducing immunoblots in adult brains and was unregulated in the aging, lipopolysaccharide (LPS), and 1-methyl-4-phenyl- 1,2,3,6-tetrahydropyridine (MPTP) insult. We further provided direct evidence that accompanied activation of primary astrocytes as well as C6 cell line induced by LPS stimulation, proGDNF was increasingly synthesized and released as the uncleaved form in cell culture. Taken together, our results strongly suggest that proGDNF may be a biologically active protein and has specific effects on the cells close to its secreting site, and a potentially important role of proGDNF signaling in the brains, in the glia-neuronal interaction or in the pathogenesis of PD, should merit further investigation.

Growth arrest specific 1 (GAS1) is abundantly expressed in the adult mouse central nervous system

Growth arrest specific 1 (GAS1) is a pleiotropic protein that induces apoptosis and cell arrest in different tumors, but it is also involved in the development of the nervous system and other tissues and organs. This dual ability is likely caused by its capacity to interact both by inhibiting the intracellular signaling cascade induced by glial cell-line derived neurotrophic factor and by facilitating the activity of the sonic hedgehog pathway. The presence of GAS1 mRNA has been described in adult mouse brain, and here we corroborated this observation. We then proceeded to determine the distribution of the protein in the adult central nervous system (CNS). We detected, by western blot analysis, expression of GAS1 in olfactory bulb, caudate-putamen, cerebral cortex, hippocampus, mesencephalon, medulla oblongata, cerebellum, and cervical spinal cord. To more carefully map the expression of GAS1, we performed double-label immunohistochemistry and noticed expression of GAS1 in neurons in all brain areas examined. We also observed expression of GAS1 in astroglial cells, albeit the pattern of expression was more restricted than that seen in neurons. Briefly, in the present article, we report the widespread distribution and cellular localization of the GAS1 native protein in adult mammalian CNS.

Growth arrest-specific gene 1 is downregulated and inhibits tumor growth in gastric cancer

Gastric cancer is one of the leading causes of malignancy-related mortality in the world, and malignant growth is a crucial characteristic in gastric cancer. In our previous study, we found that growth arrest-specific gene 1 (GAS1) suppression was involved in making gastric cancer cells multidrug-resistant by protecting them from drug-induced apoptosis. In the present study, we investigated the potential role of GAS1 in the growth and proliferation of gastric cancer. We demonstrated that GAS1 expression was decreased in gastric cancer, and patients without GAS1 expression showed shorter survival times than those with GAS1 expression. Both gain-of-function (by overexpression of GAS1) and loss-of-function (by GAS1-specific small interfering RNA knockdown) studies showed that increased GAS1 expression significantly reduced the colony-forming ability of gastric cancer cells in vitro and reduced cell growth in vivo, whereas decreased GAS1 expression had the opposite effects. Moreover, upregulation of GAS1 induced cell apoptosis, and downregulation of GAS1 inhibited apoptosis. Furthermore, we demonstrated that GAS1 could induce gastric cancer cell apoptosis, at least in part through modulating the Bcl-2/Bax ratio and the activity of caspase-3. Taken together, our results strongly indicate that GAS1 expression was decreased in gastric cancer and was predictive of a poor prognosis. Restoration of GAS1 expression inhibited cell growth and promoted apoptosis of gastric cancer cells, at least in part through modulating the Bcl-2/Bax ratio and activating caspase-3, suggesting that GAS1 might be used as a novel therapeutic candidate for gastric cancer.