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.

Evolutionary and functional analysis of Cyclina sinensis c-Jun AP-1 gene in response to LPS stimulation

The transcription factor activator protein-1 (AP-1) plays an essential and critical role in the regulation of numerous downstream genes involved in various physiological and chemical responses. In this study, we identified a full-length cDNA of the c-Jun AP-1 gene (termed Csc-Jun) from the transcriptome library in Cyclina sinensis. The cDNA contains an 825-bp open reading frame that encodes a 274-amino acid protein sequence, including a characteristic Jun transcription factor domain and a highly conserved basic leucine zipper (bZIP) signature that shares 90% identity to that of Ruditapes philippinarum. Furthermore, a phylogenetic analysis using MrBayes and PhyML software (with Bayesian and maximum likelihood approaches, respectively) revealed that the c-Jun AP-1 family genes might be involved in adapting to various environments in different invertebrates. We implemented the PAML software with the maximum likelihood method to further select and verify the positive selection sites (PSSs) in the Mollusca c-Jun AP-1 genes, and we detected four PSSs located in the Jun transcription factor domain. In addition, a spatial expression analysis showed that the Csc-Jun cDNA transcript was ubiquitously expressed in all of the tested tissues and was strongly expressed in the hepatopancreas and weakly expressed in the tissues of the hemocytes, gill filaments, mantle and adductor muscle. Quantitative real-time PCR showed that the expression profiles of Csc-Jun were significantly upregulated at different times in all of the tested tissues when challenged with lipopolysaccharide (LPS). Furthermore, knockdown of Csc-Jun by RNA interference resulted in a higher mortality of C. sinensis following LPS exposure. Finally, we explored the function of the TLR13-MyD88 signaling pathway in the innate immunity of C. sinensis by RNA interference and immune challenges. The results revealed that the mRNA expression levels of Csc-Jun were all decreased (P < 0.01) in normal and stimulated C. sinensis hemocytes. These data collectively indicated that the c-Jun AP-1 gene might play vital roles in innate immunity and provide new evidence for the evolutionary patterns of innate immune genes in Mollusca.

Anti-DR5 mAb ameliorate adjuvant arthritis rats through inducing synovial cells apoptosis

OBJECTIVE

Study the therapeutic effects and immunoregulatory mechanisms of anti-DR5 mAb on adjuvant arthritis (AA) rats.

METHODS

AA rats induced by CFA, were treated with anti-DR5 mAb through mainline administration. Effect on the synovial membranes of the tissues was detected by H&E staining. Flow cytometry and MTT assay were used for detecting the induced apoptosis in an in vitro system and TUNEL assay was used for analysis in an in vivo system. The involvement of the apoptotic pathway was further proved by a caspase inhibition assay.

RESULTS

Anti-DR5 mAb could induce synovial cell apoptosis in an in vitro system, which was related with the mRNA expression of DR5 on the cell surface. The mRNA expressions of c-myc and bcl-2 were decreased in synovial cells and those of p21, p53, and bax were increased. The protein expressions of caspase-8/3/9, RANKL, JNK2, and c-Jun were raised and that of bcl-2 was decreased. When the caspase inhibitor was added to the synovial cells treated with anti-DR5 mAb, it showed a dose-dependence inhibition effect, indicating that anti-DR5 mAb inducing apoptosis might be through the caspase pathway.

CONCLUSION

This study shows that anti-DR5 mAb can ameliorate arthritic symptoms. The mechanisms of the treatment are related to the increase in synovial cell apoptosis by regulating the mRNA expression of DR5 and apoptosis-related genes, prolonging the duration of the cell cycle by modulation of the mRNA expression of cell cycle-related genes, and the protein expression of the molecules in the caspase pathway and RANKL, JNK2, and c-Jun.

CREB-1 and AP-1 transcription factors JunD and Fra-2 regulate bone sialoprotein gene expression in human breast cancer cells

Bone sialoprotein (BSP) expression is detected in a variety of human osteotropic cancers. High expression of BSP in breast and prostate primary carcinomas is associated with progression and bone metastases development. In this study, we examined the transcriptional regulation of BSP gene expression in MDA-MB-231 and MCF-7 human breast cancer cells compared with Saos-2 human osteoblast-like cells. BSP human promoter deletion analyses delineated a -56/-84 region, which comprises a cAMP response element (CRE) that was sufficient for maximal promoter activity in breast cancer cell lines. We found that the basic fibroblast growth factor response element (FRE) also located in the proximal promoter was a crucial regulator of human BSP promoter activity in Saos-2 but not in breast cancer cells. Promoter activity experiments in combination with DNA mobility shift assays demonstrated that BSP promoter activity is under the control of the CRE element, through CREB-1, JunD and Fra-2 binding, in MDA-MB-231, MCF-7 and in Saos-2 cells. Forskolin, a protein kinase A pathway activator, failed to enhance BSP transcriptional activity suggesting that CRE site behaves as a constitutive rather than an inducible element in these cell lines. Over-expression of JunD and Fra-2 increased BSP promoter activity and upregulated endogenous BSP protein expression in MCF-7 and Saos-2 cells while siRNA-mediated inhibition of both factors expression significantly reduced BSP protein level in MDA-MB-231. Collectively, these data provide with new transcriptional mechanisms, implicating CREB and AP-1 factors, that control BSP gene expression in breast cancer cells.

Cyclooxygenase-2 gene transcription in a macrophage model of inflammation

Infections involving LPS-bearing, Gram-negative bacteria can lead to acute inflammation and septic shock. Cyclooxygenase-2 (COX-2), the target of nonsteroidal anti-inflammatory drugs and selective COX-2 inhibitors, is importantly involved in these responses. We examined the dynamics of COX-2 gene expression in RAW264.7 murine macrophages treated with LPS as a model for COX-2 gene expression during inflammation. We established, using Northern blotting, nuclear run-on assays, and RT-PCR, that COX-2 transcriptional activation continues for at least 12 h after LPS treatment and involves at least three phases. Previous studies with murine macrophages identified an NF-kappaB site, a C/EBP site, and a cAMP response element-1 (CRE-1) as cis-acting elements in the COX-2 promoter. We identified three additional functional elements including a second CRE (CRE-2), an AP-1 site, and an E-box that overlaps CRE-1. The E-box mediates transcriptional repression whereas the other cis-elements are activating. Using electrophoretic mobility supershift and chromatin immunoprecipitation assays, we cataloged binding to each functional cis element and found them occupied to varying extents and by different transcription factors during the 12 h following LPS treatment. This suggests that the cis elements and their cognate transcription factors participate in a sequential, coordinated regulation of COX-2 gene expression during an inflammatory response. In support of this concept, we found, using inhibitors of Jun kinase and NF-kappaB p50 nuclear localization, that COX-2 gene transcription was completely dependent on phospho-c-Jun plus p50 at 6 h after LPS treatment but was only partially dependent on the combination of these factors at later treatment times.

Ndfip1 protein promotes the function of itch ubiquitin ligase to prevent T cell activation and T helper 2 cell-mediated inflammation

Nedd4 family interacting protein-1 (Ndfip1) is a protein whose only known function is that it binds Nedd4, a HECT-type E3 ubiquitin ligase. Here we show that mice lacking Ndfip1 developed severe inflammation of the skin and lung and died prematurely. This condition was due to a defect in Ndfip1(-/-) T cells. Ndfip1(-/-) T cells were activated, and they proliferated and adopted a T helper 2 (Th2) phenotype more readily than did their Ndfip1(+/+) counterparts. This phenotype resembled that of Itchy mutant mice, suggesting that Ndfip1 might affect the function of Itch, an E3 ubiquitin ligase. We show that T cell activation promoted both Ndfip1 expression and its association with Itch. In the absence of Ndfip1, JunB half-life was prolonged after T cell activation. Thus, in the absence of Ndfip1, Itch is inactive and JunB accumulates. As a result, T cells produce Th2 cytokines and promote Th2-mediated inflammatory disease.

A distal regulatory region is required for constitutive and IFN-beta-induced expression of murine TLR9 gene

TLR9 is critical for the recognition of unmethylated CpG DNA in innate immunity. Accumulating evidence suggests distinct patterns of TLR9 expression in various types of cells. However, the molecular mechanism of TLR9 expression has received little attention. In the present study, we demonstrate that transcription of murine TLR9 is induced by IFN-beta in peritoneal macrophages and a murine macrophage cell line RAW264.7. TLR9 is regulated through two cis-acting regions, a distal regulatory region (DRR) and a proximal promoter region (PPR), which are separated by approximately 2.3 kbp of DNA. Two IFN-stimulated response element/IFN regulatory factor-element (ISRE/IRF-E) sites, ISRE/IRF-E1 and ISRE/IRF-E2, at the DRR and one AP-1 site at the PPR are required for constitutive expression of TLR9, while only the ISRE/IRF-E1 motif is essential for IFN-beta induction. In vivo genomic footprint assays revealed constitutive factor occupancy at the DRR and the PPR and an IFN-beta-induced occupancy only at the DRR. IRF-2 constitutively binds to the two ISRE/IRF-E sites at the DRR, while IRF-1 and STAT1 are induced to bind to the two ISRE/IRF-E sites and the ISRE/IRF-E1, respectively, only after IFN-beta treatment. AP-1 subunits, c-Jun and c-Fos, were responsible for the constitutive occupancy at the proximal region. Induction of TLR9 by IFN-beta was absent in STAT1-/- macrophages, while the level of TLR9 induction was decreased in IRF-1-/- cells. This study illustrates the crucial roles for AP-1, IRF-1, IRF-2, and STAT1 in the regulation of murine TLR9 expression.

JunB expression is a common feature of CD30+ lymphomas and lymphomatoid papulosis

JunB is a member of the Jun family of proteins that are components of the AP-1 transcription factor complex. AP-1 is involved in cell proliferation and apoptosis. Recent evidence suggests that Hodgkin and Reed-Sternberg cells overexpress JunB and that JunB facilitates constitutive CD30 expression by binding to an AP-1 site in the CD30 promoter. In this study we surveyed JunB expression in a variety of CD30+ lymphoma types including 42 cases of anaplastic large cell lymphoma, 36 classical Hodgkin lymphoma, 15 cutaneous anaplastic large cell lymphoma, and 11 CD30+ diffuse large B-cell lymphoma. In addition, seven cases of nodular lymphocyte-predominant Hodgkin lymphoma and 42 diffuse large B-cell lymphoma, known to be CD30-, were analyzed. JunB expression was assessed using tissue microarrays, immunohistochemistry and a monoclonal antibody specific for JunB. Expression of JunB was observed in 41 of 42 cases of anaplastic large cell lymphoma, including all 21 cases positive for anaplastic lymphoma kinase and 20 of 21 (95%) negative for anaplastic lymphoma kinase. JunB was also expressed in all cases of classical Hodgkin lymphoma, cutaneous anaplastic large cell lymphoma and CD30+ diffuse large B-cell lymphoma, and in lymphomatoid papulosis. By contrast, all nodular lymphocyte-predominant Hodgkin lymphomas and diffuse large B-cell lymphomas that were CD30- were also JunB-. We conclude that JunB is expressed in virtually all CD30+ lymphomas and is a potential target for experimental therapy in patients with these tumors.

Role of AP-1 in ethanol-induced N-methyl-d-aspartate receptor 2B subunit gene up-regulation in mouse cortical neurons

Activator protein 1 (AP-1) has been reported to regulate the gene expression in a wide variety of cellular processes in response to stimuli. In this study, we investigated the DNA-protein binding activities and promoter activity in the N-methyl-D-aspartate R2B (NR2B) gene AP-1 site in normal and ethanol-treated cultured neurons. The identity of the AP-1 site as the functional binding factor is suggested by the specific binding of nuclear extract derived from cultured cortical neurons to the labeled probes and the specific antibody-induced supershift. Mutations in the core sequence resulted in a significantly reduced promoter activity and the ability to compete for the binding. Moreover, treatment of the cultured neuron with 75 mm ethanol for 5 days caused a significant increase in the AP-1 binding activity and promoter activity. The AP-1 DNA-binding complex in control and ethanol-treated nuclear extract was composed of c-Fos, FosB, c-Jun, JunD, and phosphorylated CREB (p-CREB). Western blot analysis showed that p-CREB and FosB significantly increased, whereas c-Jun decreased. The DNA affinity precipitation assay indicated that FosB, p-CREB, and c-Jun increased in the AP-1 complex following ethanol treatment. These results suggest that AP-1 is an active regulator of the NR2B transcription and ethanol-induced changes may result at multiple levels in the regulation including AP-1 proteins expression, CREB phosphorylation and perhaps reorganization of dimmers.

Cardiac remodeling after long-term stimulation by antibodies against the alpha1-adrenergic receptor in rats

Although autoantibodies against the alpha1-adrenergic receptor which had been found in hypertensive patients had agonist-like activity as phenylephrine, the effects of these antibodies on cardiac remodeling have not been known. In this paper, the models with agonist-like activity of antibodies to alpha1-adrenergic receptor were made by immunized Wistar rats using synthesized peptides of alpha1A-adrenergic receptor and raised for 1 year, and the excited antibodies against the alpha1-adrenergic receptor which could elevate the free Ca2+ in isolated adult rat cardiomyocytes had been existed throughout the experiments after immunization. In immunized rats, despite that systolic blood pressure (SBP) had no difference with normal control, the hypertrophy of heart and cardiomyocytes was observed, the collagen deposition in heart interstitium increased, and c-jun expression and matrix metalloproteinase (MMP)-2 mRNA expression and activity in heart had increased. The results suggested that antibodies against the alpha1-adrenergic receptor could induce cardiac remodeling and maybe play a particular role in hypertension.

MPTP-induced increase in c-Fos- and c-Jun-like immunoreactivity in the monkey cerebellum

The transcription factors c-Fos and c-Jun have been described to be overexpressed following many pathological stimuli, but whether they are required for neurodegeneration or neuroprotection is still open. In the present report, we analyzed the role of c-Fos and c-Jun proteins in Purkinje cell degeneration caused by the neurotoxin MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) in the monkey cerebellum, and determined the neuroprotective effect of the antioxidant drug a-dihydroergocryptine (DHEC), whose prior and simultaneous administration reduced the MPTP-induced neuronal loss in the substantia nigra. Immunocytochemistry for c-Fos- and c-Jun-like proteins showed persistent increased staining in Purkinje cells of MPTP-treated monkeys. The staining was greatly reduced in animals receiving DHEC. Similar results were observed in white matter glial cells after immunoreaction for c-Fos. The results suggest that, at least as far as the cerebellum is concerned, the increase in c-Fos and c-Jun expression correlate with cell damage, rather than with preservation.

Differential activation of interferon regulatory factors-3 and -7 by non-cytopathogenic and cytopathogenic bovine viral diarrhoea virus

Non-cytopathogenic bovine viral diarrhoea virus (ncpBVDV) has previously been shown to inhibit the function of interferon regulatory factor-3 in cultured cells [J. Virol. 76 (2002) 8979]. In this study, we show that, like ncpBVDV, when cells were previously exposed to cytopathogenic BVDV (cpBVDV) the appearance of an IRF-3-DNA complex from nuclear extracts that can be induced by heterologous virus infection was not observed. Infection of cells with ncpBVDV or cpBVDV resulted in neither the translocation of IRF-7 from the cytoplasm to the nucleus of infected cells, nor an inhibition of its nuclear translocation in cells super-infected by Semliki Forest Virus. We conclude that cpBVDV and ncpBVDV both share the ability to inhibit the full function of IRF-3 but neither stimulate or block the nuclear uptake of IRF-7.

A reinvestigation of the multisite phosphorylation of the transcription factor c-Jun

We have used phospho-specific antibodies to re-examine the multisite phosphorylation of c-Jun in murine RAW macrophages and embryonic fibroblasts. Our results indicate that JNK isoforms are required and sufficient for the phosphorylation of Thr91 and Thr93, as well as the phosphorylation of Ser63 and Ser73, in response to LPS or anisomycin in macrophages and TNFalpha or anisomycin in fibroblasts. However, the phorbol ester (TPA) and EGF-induced phosphorylation of Ser63 and Ser73 is mediated by ERK1/ERK2, as well as JNK1/JNK2, in fibroblasts from wild-type mice and by ERK1/ERK2 alone in fibroblasts from JNK-deficient mice. The phosphorylation of Thr239 is catalysed by GSK3 and the phosphorylation of Ser243 by an as yet unidentified protein kinase. The inhibition of GSK3 is not required for the dephosphorylation of Thr239 in response to LPS, and nor is the phosphorylation of Thr91 and Thr93 required for the TPA- or EGF-induced dephosphorylation of Thr239 in fibroblasts. The agonist-induced dephosphorylation of Thr239 may involve a conformational change that exposes Thr239 to dephosphorylation and/or the activation of a Thr239 phosphatase.

L10 ribosomal protein from Entamoeba histolytica share structural and functional homologies with QM/Jif-1: proteins with extraribosomal functions

In the present work, the complete amino acid sequence of the Entamoeba histolytica ribosomal protein L10 (EhL10) is reported. cDNA of 630bp revealed an open reading frame that encodes a protein of 210 amino acids. Analysis of EhL10 ribosomal protein revealed 75% similarity and 57% identity with QM protein from Homo sapiens and 78 and 60%, respectively, with Arabidopsis thaliana. Western blot analysis of ribosomal proteins from E. histolytica showed that EhL10 protein is part of the ribosomal complex. Immunofluorescence analysis of EhL10 distribution in a transfected E. histolytica strain showed that EhL10 protein was mainly localized in the nucleus of trophozoites. Overexpression of EhL10 ribosomal protein in trophozoites transfected with the pExEhNeo/EhL10 vector exhibited a 60% reduction in cellular growth. DNA mobility-shift assays demonstrated that EhL10 ribosomal protein was able to destabilize the activating protein 1 (AP-1) complex binding specifically to the c-Jun-like protein. It is proposed in this study that the complex formation of EhL10 with c-Jun-like protein interferes with transcriptional activation of genes controlled by Jun (i.e. gene involved in cell growth). It is also being reported identification of a member of the AP-1 complex, the c-Jun-like protein, in nuclear extracts of E. histolytica using human-specific antibodies against this protein. The observations suggest that EhL10 may have an extraribosomal function in E. histolytica involved in suppression of cell proliferation in E. histolytica similar to the QM protein.

Regulation of trophoblastic gelatinases by proto-oncogenes

During the first trimester of pregnancy, certain cytotrophoblastic cells (CTB) of anchoring villi invade the underlying decidua. Regulation of this invasive behaviour depends on cytokines and growth factors secreted by decidua and trophoblast, which modulate metalloproteinase (MMP) secretion of CTB. Since MMP-9 expression by CTB is a prerequisite for matrigel invasion and since the promoter region of the MMP-9 gene contains two AP-1 binding sites, we hypothesized, that transient activation of c-jun and c-fos oncogenes (which bind to form AP-1) by tumour necrosis factor (TNFalpha), or the phorbol ester TPA will promote the invasive phenotype of CTB and induce the production of MMP-9.TNFalpha or TPA when added to primary cultures of CTB increase MMP-9 activity and MMP-9 mRNA. This effect is inhibited by cycloheximide indicating the necessity of protein synthesis. TPA or TNFalpha induces also the binding of nuclear proteins (extracted from treated CTB) to a radiolabelled oligonucleotide corresponding to the consensus sequence of the TPA responsive element. Antibodies to Jun and Fos can displace this binding. Transient transfection of antisense mRNA to jun or fos into CTB inhibits the immunoreactivity and gelatinolytic activity of MMP-9. We conclude that AP-1 is necessary but may not be sufficient for transactivation of the MMP-9 gene in human CTB.

C-JUN and CPP32 (CASPASE 3) in human pancreatic cancer: relation to cell proliferation and death

INTRODUCTION

There is strong evidence that tumor growth is not only a result of uncontrolled cell proliferation but also of decreased apoptosis.

AIMS

To ascertain the expression of c-Jun in specimens of pancreatic duct cancer and to evaluate its correlation with CPP32, apoptotic index, and proliferation index (MIB-1).

METHODS

Tissue samples were collected from 23 patients with pancreatic duct cancer who had not received chemotherapy nor radiation therapy before surgery. In these specimens we determined the expression of c-Jun protein, CPP32, and MIB-1 by immunohistochemical method. Apoptosis was studied by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling method.

RESULTS

CPP32/caspase3 was expressed in 83% and c-Jun in 87% of primary lesions. Three of 23 samples were completely negative for c-Jun, and 4 of 23 were negative for CPP32. Three of 4 specimens negative for CPP32 showed low or negative c-Jun. A significant correlation was found between CPP32/caspase3 and c-Jun (r = 0.51; p < 0.01) and between c-Jun and MIB-1 (r = 0.57; p < 0.004). No correlation was found between CPP32, c-Jun, MIB-1, and apoptotic index.

CONCLUSIONS

The positive correlation between the expression of c-Jun and CPP32 and the absence of both in the same specimens suggest that a common factor or common factors induce the expression of both genes. Pancreatic cancer tissue with an increased percentage of proliferating tumor cells showed also a strong expression of c-Jun, which supports the hypothesis that this oncogene may be involved in the growth of pancreatic cancer. We hypothesize that under different extracellular stimuli both death and proliferation are activated in neoplastic cell, probably under the control of transcription factor AP-1.

Abundant expression of c-Jun in guinea pig sympathetic ganglia under basal conditions and allergen challenge

Airway hyperresponsiveness, a keystone of allergic asthma, is mediated by the extrinsic airway innervation. As pathophysiological stimuli can induce the expression JUN proteins, which belong to the immediate early gene (IEG) family of transcription factors, the expression of c-Jun was examined under basal conditions and allergen challenge in guinea pig paravertebral and prevertebral sympathetic ganglia by quantitative double-labeling immunohistochemistry. C-Jun immunoreactivity was seen in 78.4 +/- 3.5% under normal and 82.6 +/- 4.6% under allergen-challenged conditions of protein-gene product (PGP) 9.5-positive sympathetic neurons of guinea pig superior cervical ganglia and 73.1 +/- 2.8% (normal) and 76.1 +/- 3.5% (allergen) of stellate ganglion neurons. In the coeliac-superior mesenteric ganglion, 59.5 +/- 5.0% (normal) and 57.5 +/- 4.4% (allergen) of the PGP 9.5-positive sympathetic neurons were labeled for c-Jun. The high basal levels of c-Jun expression indicate that the presence of c-Jun is not exclusively related to noxious stimulation such as allergic airway inflammation in the guinea pig.

Apoptosis-specific protein (ASP 45 kDa) is distinct from human Apg5, the homologue of the yeast autophagic gene apg5

We have examined whether the apoptosis-specific protein p45ASP and human Apg5 are identical proteins. Like p45ASP, myc-hApg5 cross-reacted with a c-Jun antibody and approximately 50% of myc-hApg5 was bound to a Triton X-100-insoluble fraction in HeLa cells. However, soluble myc-hApg5 was degraded during apoptosis induced by staurosporine or TNFalpha/cycloheximide whilst expression of soluble p45ASP was stabilised. Furthermore, myc-hApg5 degradation was blocked by the caspase inhibitor Boc-Asp(OMe)FMK whilst p45ASP expression was eliminated. Moreover, myc-hApg5 ( approximately 32 kDa) never assumed the size of p45ASP (45 kDa). It is therefore likely that p45ASP and human Apg5 are distinct proteins although they do share some common characteristics.

c-Jun-like immunoreactivity in apoptosis is the result of a crossreaction with neoantigenic sites exposed by caspase-3-mediated proteolysis

Previous reports in various cells and species have shown that apoptotic cells are specifically and strongly labeled by certain c-Jun/N-terminal antibodies, such as c-Jun/sc45. This kind of immunoreactivity is confined to the cytoplasm. It is not due to c-Jun but appears to be related to c-Jun-like neoepitopes generated during apoptosis. This study was planned to gain further information about c-Jun-like immunostaining during apoptosis and to evaluate these antibodies as possible tools for characterizing cell death. Most of the experiments were performed in chick embryo spinal cord. When the apoptotic c-Jun-like immunoreactivity and caspase-3 immunostaining patterns were compared, we found that both antibodies immunostained the same dying cells in a similar pattern. In contrast to TUNEL staining, which reveals a positive reaction in both apoptotic and necrotic dying cells, active caspase-3 and c-Jun/sc45 antibodies are more selective because they stained only apoptotic cells. When cytosolic extracts from normal tissues were digested in vitro with caspase-3, c-Jun/sc45 immunoreactivity was strongly induced in several proteins, as demonstrated by Western blotting. Similar results were found when normal tissue sections were treated with caspase-3. Our results show that c-Jun/sc45 antibodies react with neoepitopes generated from cell proteins cleaved by activated caspases during apoptosis. We conclude that c-Jun/sc45 antibodies may be useful for detecting apoptosis. They can even be used in archival paraffin-embedded tissue samples.

Immunoreactivity for Bcl-2 and C-Jun/AP1 in hippocampal corpora amylacea after ischaemia in humans

Corpora amylacea (CAm) are regarded as a hallmark of brain ageing, but little is known about their role in normal and pathological circumstances. CAm contain, in addition to glucose polymers, ageing-, stress- and proinflammatory proteins. In view of their almost universal occurrence and their cumulation with time, formation of CAm may represent a basic mechanism for the management of metabolic degradation products. In this context, we studied samples from post-mortem cases with repetitive brain hypoxic episodes in the past history. We investigated, by immunohistochemistry, the presence of Bcl-2, c-jun and bax in CAm. CAm showed immunoreactivity for the mitochondrial membrane associated protein Bcl-2, and for the major component of activator protein 1 transcriptional factor c-Jun. We found higher numbers of CAm in the hippocampus and the dentate gyrus in cases with repetitive cerebral hypoxia than in controls. We conclude that: (1) the presence of C-Jun and Bcl-2 within the glucose polymer mass of CAm may be related to mitochondrial damage and/or a transient overload of proteolytic systems during cellular injury; and (2) repetitive cellular stress during life may cause the age-related increase of CAm in elderly subjects.

Antibodies against c-Jun N-terminal peptide cross-react with neo-epitopes emerging after caspase-mediated proteolysis during apoptosis

In previous studies it has been shown that neural cells undergoing programmed cell death display strongly positive cytoplasmic immunoreactivity to polyclonal antibodies directed against a c-Jun N-terminal peptide. It was later found that c-Jun-like immunoreactivity in apoptosis was due to cross-reactivity with proteins other than c-JUN: We have analysed the biochemical counterpart of this property in neuroblastoma cell lines treated to induce apoptosis. Using the c-Jun/sc-45 antibody, several bands with apparent molecular masses distinct from c-Jun were detected in extracts in parallel with both the degree of apoptosis and the appearance of the cytoplasmic signal after immunostaining. c-Jun/sc-45 immunostaining was prevented by caspase inhibitors and did not require de novo protein synthesis. One of the antigens recognized by the c-Jun/sc-45 antibody was identified as seryl-tRNA synthetase. We provide evidence that seryl-tRNA synthetase is a substrate of caspase-3 in vitro and that the digested form turns highly immunoreactive towards the antibody. A carboxy-terminus epitope of the protein that constitutes a consensus site for caspase-3 is involved in c-Jun/sc-45 recognition. This epitope shares some amino acids with the peptide used as the immunogen and this could explain the cross-reactivity observed. In conclusion, we demonstrate here that cytoplasmic c-Jun/sc-45-like immunoreactivity specific to apoptosis is due to post-translational changes which occur in seryl-tRNA synthetase and probably also in other proteins as a consequence of caspase mediated proteolysis.

c-Jun regulation in rat neonatal motoneurons postaxotomy

Motoneurons respond to peripheral nerve transection by either regenerative or degenerative events depending on their state of maturation. Since the expression of c-Jun has been involved in the early signalling of the regenerative process that follows nerve transection in adults, we have investigated c-Jun on rat neonatal axotomized motoneurons during the period in which neuronal death is induced. Changes in levels of c-Jun protein and its mRNA were determined by means of quantitative immunocytochemistry and in situ hybridization. Three hours after nerve transection performed on postnatal day (P)3, c-Jun protein and mRNA is induced in axotomized spinal cord motoneurons, and high levels were reached between 1 and 10 days after. This response is associated with a detectable c-Jun activation by phosphorylation on serine 63. No changes were found in the levels of activating transcription factor -2. Most of dying motoneurons were not labelled by either a specific c-Jun antibody or a c-jun mRNA probe. However, dying motoneurons were specifically stained by a polyclonal anti c-Jun antibody, indicating that some c-Jun antibodies react with unknown epitopes, probably distinct from c-Jun p39, that are specifically associated with apoptosis.

Localization of transcription factor AP-1 family proteins in ameloblast nuclei of the rat incisor

We examined by immunocytochemistry the localization of the AP-1 family proteins c-Jun, JunB, JunD, c-Fos, FosB, Fra-1, and Fra-2 in rat incisor ameloblasts. Most of the antibodies against AP-1 family proteins, except for c-Fos-specific antibody, labeled ameloblast nuclei. The labeling intensity of the c-Jun, JunD, and Fra-2 antibodies was stronger than that of JunB, FosB, and Fra-1. Antibody reactivities of c-Jun, JunD, and Fra-2 were greatly enhanced during or after the transition zone. Furthermore, c-Jun antibodies labeled maturation ameloblasts in a cyclic pattern, which was correlated with ameloblast modulation. Disruption of ameloblast modulation by colchicine injection resulted in greatly decreased reactivity of the c-Jun antibody in the ameloblast nuclei of the maturation zone. Phospho-specific antibodies to c-Jun labeled ameloblast nuclei only weakly throughout the secretion, transition, and maturation zones. These results suggest that the stage-specific localization of AP-1 in ameloblasts is closely related to tooth enamel formation.

Expression profiles of JunB and c-Fos proteins in the rat circadian system

The immediate-early genes c-Fos and JunB are implicated in light signaling within the suprachiasmatic nucleus (SCN), the mammalian circadian clock. Light induces phase-dependent expression of c-Fos and JunB within the retinorecipient SCN. In the absence of light, rhythmic expression of these genes has been observed in the dorsal region of the SCN with peak expression observed near dawn. The present study examined the pattern of induction of c-Fos and JunB in the SCN and intergeniculate leaflet (IGL) of rats housed in constant conditions, under light-dark cycles, or in dark-adapted light-stimulated animals. In contrast with previous studies, no evidence of expression of c-Fos and JunB was observed within the dorsal SCN, regardless of circadian time. Strain differences could account for the absence of rhythmic JunB expression, whereas the use of a monoclonal anti-c-Fos antibody in the present study may account for the absence of dorsal SCN c-Fos staining. The profile of light-induced c-Fos and JunB expression was consistent with previous observations. In the SCN, light-induced expression of c-Fos and JunB was phase dependent, whereas in the IGL light-induced both c-Fos and JunB regardless of circadian time.

Calcium channel blockers inhibit proliferation and matrix production in rat mesangial cells: possible mechanism of suppression of AP-1 and CREB activities

BACKGROUND

Calcium channel blockers (CCBs) are reported to attenuate the loss of renal function in various glomerulonephritides.

METHODS

To determine the mechanism of action of these drugs, we investigated the effects of CCBs on cell proliferation and extracellular matrix (ECM) production in cultured rat mesangial cells.

RESULTS

While stimulation with 5% fetal calf serum (FCS) increased [(3)H]thymidine and [(3)H]proline incorporation into quiescent mesangial cells, incubation with nifedipine and cilnidipine inhibited the increase in a dose-dependent manner. Northern blot analysis demonstrated that 5% FCS increased the expression of transforming growth factor beta (TGF-beta) and fibronectin (FN) mRNA and that CCBs significantly reduced this induction, indicating that CCBs may reduce ECM production through inhibiting TGF-beta and FN. Since activator protein 1 (AP-1) regulates cell proliferation and TGF-beta expression, we evaluated the AP-1 activity by gel mobility shift analysis. Nuclear extracts of FCS-treated cells showed a strong binding to AP-1-specific oligonucleotides which was suppressed by CCBs, suggesting that these agents may inhibit cell proliferation by suppressing AP-1. CCBs also inhibited the binding activity of cyclic adenosine monophosphate responsive element binding protein which regulates FN gene expression. However, neither CCBs nor FCS affected the NFkappaB activity.

CONCLUSION

These results suggest that CCBs may, in part, inhibit the progression of glomerulonephritis through non-hemodynamic actions that include the suppression of mesangial cell proliferation and the production of ECM.

Motor neuronal death in sporadic amyotrophic lateral sclerosis (ALS) is not apoptotic. A comparative study of ALS and chronic aluminium chloride neurotoxicity in New Zealand white rabbits

Whether diseased motor neurones in sporadic amyotrophic lateral sclerosis (ALS) die via apoptosis is unknown. Because this relates primarily to difficulties in utilizing post-mortem tissue from end-stage disease, motor neurone degeneration in ALS spinal cord was compared with that of a model of a chronic motor neurone degeneration. Degenerating motor neurones in ALS, identified by ubiquitin immunoreactivity, did not demonstrate the morphological characteristics of apoptosis and were not c-Jun immunoreactive or TUNEL positive. A temporal analysis of spinal motor neurone death in the chronic AlCl3 neurotoxicity model of motor neurone degeneration was also undertaken. AlCl3 was administered intracisternally every 4 weeks and, at intervals of 51, 107, 156 and 267 days, evidence of apoptosis was sought by morphology, TUNEL hybridization or DNA laddering. Double-labelling immunostudies were also performed with antibodies to either c-Jun, ubiquitin or high molecular weight neurofilament (NFH) with TUNEL hybridization. Although significant neurone loss was evident, apoptosis was not found. These studies demonstrate a lack of apoptosis in ALS spinal motor neurones and suggest that this observation does not relate to the utilization of post-mortem tissue in which apoptotic neurones may have been lost.

Effects of amphetamine and cocaine treatment on c-Fos, Jun-B, and Krox-24 expression in rats with intrastriatal dopaminergic grafts

Activation of dopaminergic (DA) transmission by psychostimulants increases c-fos expression. d-Amphetamine-induced c-fos activation is reduced in the neostriatum deprived of DA afferents. Dopaminergic grafts implanted into the denervated neostriatum induce a c-fos hyperexpression when challenged with d-amphetamine, which is correlated with the exaggerated compensation of d-amphetamine-induced rotation. The aim of the present study was to test the generality of this phenomenon and the effects of DA grafts on the expression of three immediate early gene-coded proteins (c-Fos, Jun-B, Krox-24) following a challenge with either d-amphetamine or cocaine. c-fos basal expression was low in the neostriatum and was increased by the administration of psychostimulants. These effects were blocked by the DA lesion and restored by the DA grafts. A c-fos hyperexpression was observed within the grafted neostriatum, which was correlated with the compensation of d-amphetamine- or cocaine-induced rotation. Basal levels of Jun-B- and Krox-24-LI nuclei were high within the neostriatum. Administration of d-amphetamine or cocaine did not influence the expression of these IEG-coded proteins. Jun-B expression was not affected by the surgical procedure. In contrast, lesion of DA afferents of neostriatum decreased Krox-24 basal expression, an effect reversed by the grafts. Thus, the expression of c-fos but not Jun-B or Krox-24 appeared to be a good marker for the rotational behavior exhibited by DA-grafted rats challenged with drugs that increased DA transmission. This generalized c-fos overshoot indicates an abnormal activation of postsynaptic neurons by dopamine and points to its value as an indicator of the deleterious effects of DA grafts.

Factors from Trypanosoma cruzi interacting with AP-1 sequences

Interaction between factors from Trypanosoma cruzi extracts and AP-1 sequences was studied by electrophoretic mobility shift assays. Using a double-stranded probe carrying the AP-1 sequence from the SV40 promoter, three specific complexes designated A, B, and C were detected. Complexes A and C were formed when using single-stranded probes. The relative amount of complex B, specific for double-stranded DNA, increased as a function of probe length. Complexes were stabilized by cross-linking with UVC irradiation and resolved on denaturing SDS-PAGE. Complex A generated bands of 60- and 39 kDa; complex B produced two bands of 46- and 43 kDa; and complex C generated one band of 43 kDa. The AP-1 binding activity was much higher in purified nuclear preparations than in soluble fractions, and was detected in crude extracts from the three forms of the parasite. The binding signal, however, was much stronger in amastigote and trypomastigote than in the epimastigote forms. Specific binding was increased by oxidative stress. Antibodies raised against peptides corresponding to conserved domains of mammalian c-Jun and c-Fos detected bands of 40- and 60 kDa, respectively, in a nuclear epimastigote preparation.

Effects of mild traumatic brain injury on immunoreactivity for the inducible transcription factors c-Fos, c-Jun, JunB, and Krox-24 in cerebral regions associated with conditioned fear responding

We have previously demonstrated that mild traumatic brain injury (TBI) of the right parietal cortex results in a relatively selective deficit in conditioned fear responding. However, this behavioural deficit is very consistent and unrelated to the extent of the cortical necrotic lesion. We were therefore interested in determining if other brain regions might show a consistent response to mild TBI, and therefore, more reliably relate to the behavioural change. Increased expression of inducible transcription factors (ITFs) has been used to study which brain regions respond to a variety of events. In the present study, we examined the expression patterns of immunoreactivity (IR) for four ITFs (c-Fos, c-Jun, JunB, and Krox-24) at 3 h after mild fluid percussion TBI. Changes in ITF expression were only observed ipsilateral to the side of TBI. The clearest changes were observed in brain regions known to be involved in conditioned fear responding, such as the amygdala complex and hippocampal formation and several cortical regions. In contrast, no changes in IR for any of the ITFs were observed in the striatum, nucleus accumbens, nucleus basalis magnocellularis, septum or periacqueductal grey. Unlike the extent of visible damage to the cortex at the site of impact, the overexpression of ITFs showed a notable consistency between animals subjected to TBI. This consistency in regions known to be involved in conditioned fear responding (i.e., amygdala complex and hippocampal formation) lead us to suggest that it is these changes, rather than the more variable cortical necrotic lesion, that is responsible for the behavioural deficits we observe following mild TBI. Importantly, our results demonstrate that like the hippocampus, the amygdala is a sub-cortical structure particularly sensitive to the effects of mild brain trauma and underline the fact that cerebral regions distant from the location of the fluid impact can be affected.

UV-Laser induced protein/DNA crosslinking reveals sequence variations of DNA elements bound by c-Jun in vivo

Many proteins involved in the modulation of gene expression exert their function through direct interaction with DNA. The sequence specificity of these interactions provides the basis for many regulatory mechanisms. The sites that are utilized by a transcription factor are usually analyzed using in vitro binding studies. To detect true in vivo binding sites we developed a method, presented here, that allows construction of recognition element DNA (reDNA) libraries which represent in vivo binding sites plus flanking sequences. reDNA libraries can be constructed for any well-characterized transcription factor. Here we used this method for an in vivo study of genomic DNA elements that interact with the transcription factor c-Jun in rat cerebellum.

Enterocyte-like differentiation of the Caco-2 intestinal cell line is associated with increases in AP-1 protein binding

The nuclear factor AP-1, a large family of transcription factors composed of the Jun and Fos protein families, plays a role in the differentiation of various cells; the role of the AP-1 factors in intestinal differentiation is not known. Members of the AP-1 family can be activated by the Ras pathway and, in addition, Ras appears to be important for gut differentiation. The purpose of this study was to determine whether AP-1 activity is altered in the Caco-2 cell line, which spontaneously differentiates to a small bowel phenotype after confluency, and the Caco-2-ras cell line, which exhibits differentiated properties regardless of culture conditions. AP-1 binding activity, consisting of c-Jun, JunD, c-Fos and Fra-2 proteins, was increased in Caco-2 cells at 3 days postconfluency, a time point associated with G1 block and cessation of proliferation. Steady state levels of JunD were increased at day 3 postconfluency as determined by Western blot. Furthermore, AP-1 binding was increased in preconfluent Caco-2-ras cells compared with parental Caco-2 cells, suggesting that AP-1 induction may be mediated by the Ras pathway. The early induction of AP-1 binding activity suggests a role for these proteins in the differentiation of the Caco-2 intestinal cell line.

C-Fos, Jun D and HSP72 immunoreactivity, and neuronal injury following lithium-pilocarpine induced status epilepticus in immature and adult rats

In order to follow the maturation-related evolution of neuronal damage, cellular activation and stress response subsequent to Li-Pilo seizures in the 10- (P10), 21-day-old (P21) and adult rat, we analyzed the expression of the c-Fos protein as a marker of cellular activation, HSP72 immunoreactivity as the stress response and silver staining for the assessment of neuronal damage in 20 selected brain regions. The early wave of c-Fos measured at 2 h after the onset of seizures was present in most structures of the animals at the three ages studied and particularly strong in the cerebral cortex, hippocampus and amygdala. The late wave of c-Fos measured at 24 h after the onset of seizures and that was shown to correlate to neuronal damage was absent from the P10 rat brain, and present mainly in the cerebral cortex and hippocampus of P21 and adult rats. The expression of the stress response, assessed by the immunoreactivity of HSP72 at 24 h after the seizures was absent from the P10 rat brain and present in the entorhinal cortex, amygdala, hippocampus and thalamus of P21 and adult rats. The expression of Jun D at 24 h after the seizures was discrete and present in most brain regions at all ages. Neuronal injury assessed by silver staining at 6 h after the onset of seizures was very discrete in the brain of the P10 rat and limited to a few neurons in the piriform and entorhinal cortices. In older animals, marked neuronal degeneration occurred in the cerebral cortex, amygdala, hippocampus, lateral septum and thalamus. Thus the immediate cell activation induced by lithium-pilocarpine seizures which is present at all ages translates only into a late wave of c-Fos and the expression of HSP72 in P21 and adult animals in which there will be extensive cell damage.

An upstream negative regulatory element in human granulocyte-macrophage colony-stimulating factor promoter is recognised by AP1 family members

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a cytokine involved in haematopoiesis and host defence. Production of GM-CSF has been detected in tumour cells including the U87MG astrocytoma cell line. Previous studies have been focused on the regulatory role of the proximal region of the GM-CSF promoter. Our studies on the distal region of the promoter in U87MG cells identify a negative cis element (-1377/-1298) which contains a AP1-like site able to bind c-jun and c-fos transcription factors, according to the results of DNA/protein binding assays. Mutagenesis of the AP1-like site eliminates AP1 binding and the negative effect on promoter activity.

Retrograde regulation of growth-associated gene expression in adult rat Purkinje cells by myelin-associated neurite growth inhibitory proteins

Axon regeneration requires that injured neurons reinitiate long-distance growth and upregulate specific genes. To address the question of whether inhibitory environmental cues along the axon could exert a negative, tonic downregulation of growth-associated genes, we have examined adult rat Purkinje cells, which are endowed with poor regenerative capabilities. First we have compared their response to axotomy with that of neurons of the inferior olive, lateral reticular nucleus, and deep cerebellar nuclei, all of which vigorously regenerate into growth-permissive transplants. These injured neurons upregulate the transcription factors c-Jun and JunD, GAP-43, and NADPH diaphorase. In contrast, most axotomized Purkinje cells fail to express any of these markers, showing that the strength of this response parallels the regenerative potential of the examined neuron populations. However, strong upregulation of the same genes can be induced in Purkinje cells after colchicine injection into the uninjured adult cerebellum, indicating that their expression could be controlled by retrograde signals. To assess whether myelin-associated neurite growth inhibitory proteins contribute to this regulation, we applied the neutralizing antibodies IN-1 against one of the main inhibitory components of central myelin (NI-250) either in vivo or in vitro to organotypic cerebellar cultures. Application of IN-1 antibodies induces the upregulation of c-Jun, JunD, and NADPH diaphorase in Purkinje cells, showing that their expression is suppressed constitutively by myelin-associated neurite growth inhibitors. Thus, the inhibitory activity of the IN-1 antigen on axon growth is not restricted to the control of growth cone motility but also involves a retrograde regulation of gene expression in adult central neurons.

Correlation between potentiation of AP1 DNA binding and expression of c-Fos in association with phosphorylation of CREB at serine133 in thalamus of gerbils with ischemia

Protein biosynthesis is mainly under the control at the level of gene transcription in eukaryotes. Transcription factors are nuclear proteins with abilities to modulate the activity of RNA polymerase II which is responsible for the formation of messenger RNA from double stranded DNA in the cell nuclei. Binding of a radiolabeled oligonucleotide probe for the transcription factor activator protein-1 (AP1) was transiently potentiated 1 to 6 h after the recirculation of blood supply in the thalamus and striatum, but not in the entorhinal cortex, olfactory bulb, frontal cortex, cerebellar cortex and medulla-pons, in gerbils with transient global forebrain ischemia for 5 min, in addition to the hippocampal subregions. The ischemic insult not only increased the immunoreactivity with an antibody against cyclic AMP response element binding protein (CREB) phosphorylated at serine133, but also induced the expression of both c-Jun and c-Fos family proteins 3 h after the recirculation in the thalamus. Limited proteolysis by Staphylococcus aureus (S. aureus) V8 protease revealed the expression of different partner proteins of AP1 in response to ischemic signals in the thalamus. Moreover, ischemia for 2 min led to more prolonged elevation of AP1 binding in the thalamus at least up to 12 h after the reperfusion than that seen with ischemia for 5 min. These results suggest that potentiation of AP1 DNA binding may at least in part involve mechanisms associated with the expression of c-Fos protein through phosphorylation of CREB at serine133 in the thalamus of gerbils with ischemia.

Transcription factor AP1 is involved in basal and okadaic acid-stimulated activity of the human PRL promoter

The tumor promoter, okadaic acid (OA), an inhibitor of protein phosphatases, stimulates the activity of the human PRL (hPRL) proximal promoter. We analyzed in detail the effects of OA on transcription factor binding to elements P1 and P2 of this promoter, sequences known to contain at least one Pit-1 binding site each. OA treatment induces binding of an AP1-related transcription factor to the P1 site. This effect is specific, as protein binding to the P2 site is not altered by the treatment. Specific antibodies were used to confirm that the OA-induced complex is related to AP1 and to show that it contains JunD and c-fos, but not Pit-1. The increase in AP1 binding to P1 and to a canonical AP1 site correlates to an increase in cellular JunD and c-fos content. Transient transfection experiments showed that both AP1 and Pit-1 are involved in the regulation of basal and OA-stimulated promoter activity. Our results demonstrate that a member of the AP1 family, containing JunD and c-fos, can bind to the proximal element P1 within the hPRL promoter. In addition, they show that AP1 is involved in both basal and OA-stimulated expression of the hPRL gene.

Inhibition of CD28/CD3-mediated costimulation of naive and memory human T lymphocytes by intracellular incorporation of polyclonal antibodies specific for the activator protein-1 transcriptional complex

A number of indirect methods have been utilized in demonstrating activator protein-1 transcription factor function in IL-2 promoter activity. However, there has been no direct demonstration that activator protein-1 is involved in CD28-dependent costimulation of IL-2 gene transcription in freshly isolated naive and memory human T lymphocytes. To address this issue, the method of scrape loading was applied to purified peripheral blood T lymphocytes. Since scrape loading relies on adherent cells, peripheral blood human T (PB-T) cells were immobilized on the nonspecific cell attachment factor poly-L-lysine. Cells scraped off poly-L-lysine in the presence of Ig FITC efficiently incorporated Ig, with relatively uniform fluorescence. T cells retained their physical parameters as measured by forward and side light scatter, and functional activity as measured by costimulation of proliferation and IL-2 production after being scraped off this substrate. CD28/CD3-costimulated T cells produced intracellular IL-2 from all subsets measured (CD4+, CD4-, CD45RO+, and CD45RO-). IL-2 production and intracellular accumulation in nonscraped PB-T cells activated with CD28/CD3 coligation were skewed favoring CD45RO+ and CD4+ subsets, as was IL-2 production in scraped PB-T cells. The intracellular incorporation of Abs specific for c-Fos and c-Jun family members by scrape loading inhibited the production and intracellular accumulation of IL-2 within 6 h of costimulation with PMA/ionomycin, or costimulation by CD28 and CD3 ligation. Scrape loading thus provides an efficient mechanism for intracellular incorporation of macromolecules, and the first direct evidence that c-Fos and c-Jun are involved in transcription of the IL-2 gene within its correct chromosomal context, in resting human T lymphocyte subpopulations.

Characterization of the long-lasting activator protein-1 complex induced by kainic acid treatment

Kainic acid is known to induce seizures, neuronal damage and cell loss in the rat hippocampus. Our laboratory has shown that a single kainic acid injection elicits acute increases of activator protein-1 DNA-binding activity and this activity stays at an elevated level for 2 weeks after kainic acid injection. However, some pathological changes such as mossy fiber sprouting do not occur until 2-3 weeks after the kainic acid injection and the specific transcription factors regulating the long-term events after kainic acid treatment are not clear. To determine the involvement of activator protein-1 transcription factors in the long-term events after kainic acid treatment, gel mobility-shift and Western blot analyses were used. The results showed that two activator protein-1 complexes with different mobilities occur during the acute stage. However, only the faster-migrating complex as well as the 35-37-kDa fos-related antigen and Jun-D proteins were seen during the late stage. These results suggest that different activator protein-1 complexes exist at different stages after convulsions and that they regulate ensembles of different genes.

Lead-induced developmental changes in AP-1 DNA binding in rat brain

Exposure to lead during ontogeny is detrimental to the growth and development of the brain. Morphological abnormalities occur in the developing brain, which are manifested as mental retardation and other neurological disorders. Despite extensive research, the biochemical mechanism for neurological effects of lead has not been established but appears to be at the level of the genome since aberrant expression of developmentally-important genes has been reported. Basal levels of activator protein 1 (AP-1) transcription factor DNA binding are elevated in the rat brain during the early postnatal period. The AP-1 DNA binding complex is composed of a Jun:cAMP responsive element binding protein dimer, which appears to modulate expression of developmentally-important genes that contain AP-1 binding sites in their promoter. Brain regions from perinatally lead-exposed rats were examined on postnatal days 3, 9 and 15 for DNA binding activity to the AP-1 DNA sequence. AP-1 DNA binding activities were significantly increased on postnatal day 3 in hippocampus and cortex from lead-treated rats with no other area (frontal lobe or brainstem) or timepoint showing significant changes. Since no increases were detected in the level of Jun protein which is a component of the AP-1 binding complex, post-translational modification may be involved in enhancing DNA binding activity. By altering levels of AP-1 DNA binding to the promoter regions, lead exposure may be changing the levels of mRNA synthesis of developmentally important genes.

Fos and Jun expression in rat supraoptic nucleus neurons after acute vs. repeated osmotic stimulation

Using a double-label immunofluorescence method, we analyzed the time course of the appearance of Fos and Jun in the nuclei of supraoptic nucleus (SON) neurons following intraperitoneal injection of hypertonic saline. Fos and Jun immunostaining appeared within 30 min, peaked at 90-120 min, and disappeared 4-5 h later. At all time points (30, 60, 120, 180, 240 min postinjection), colocalized Fos and Jun immunostaining was observed (> 90% colocalized staining in labeled neurons). At 4 h post-saline injection, some rats received a second injection of normal or hypertonic saline. A second injection of normal saline resulted in no Fos/Jun immunostaining 90 min later, while hypertonic saline induced combined Fos/Jun staining in only 17% of SON neurons. Of the remaining SON cells, 23% had staining to Fos alone and 4% of the cells stained for Jun only. In spite of the delivery of an effective second osmotic stimulus, determined by assessment of plasma osmolality and sodium content, SON neurons exhibited less colocalized Fos/Jun immunostaining, dramatically less Jun expression, and substantial, but attenuated, immunostaining for Fos. These results are discussed in the context of known negative feedback mechanisms that control the re-expression of these transcription factors.

Immunocytochemical localization of C-myc and C-jun oncoproteins in hamster kidney and estrogen-induced kidney tumors

The chronic administration of 17beta-estradiol to male Syrian hamsters for 6-7 months induces kidney tumors which express high levels of c-fos, c-myc and c-jun mRNA compared to surrounding tissue or untreated controls. In this study, we have investigated, by immunocytochemical methods, the cellular localization of c-myc and c-jun oncoproteins in estrogen-dependent kidney tumors, in kidney tissue of hamsters treated with 17beta-estradiol for 6 months and in the kidneys of age-matched controls. The c-myc oncoprotein was strongly expressed in tumors, in smooth muscle layers of arteries and in parietal epithelial cells of the glomerulus. In age-matched untreated kidneys, there was little or no staining in the glomerulus, arteries or kidney tubular cells. The c-jun oncoprotein was detected in kidney tumors and in the tubular epithelium of surrounding tissue. The immunoreactivity for c-jun oncoprotein was highest in the tumor, intermediate in estrogen-treated kidney tissue and lowest in kidney tubular cells of controls. It is concluded that the high expression of c-myc in estrogen-induced kidney tumors, in the smooth muscle layer of arteries, and in glomerular parietal epithelial cells in the kidneys of 17beta-estradiol-treated hamsters, but poor expression in control kidneys indicate an involvement of this oncoprotein in the tumorigenic process. In contrast, c-jun is expressed in untreated, in 17beta-estradiol-treated kidneys and in tumors, and may not serve as a prognostic marker in the transformation of these cells to the malignant phenotype.

Oncoprotein expression in human synovial tissue: an immunohistochemical study of different types of arthritis

Based on the fact that synovial lining cells have some properties of transformed-appearing cells, we have examined the expression of Myc, Myb, Fos, Jun and Ras oncoproteins in synovial tissues from patients with different types of arthritis. Formalin-fixed and paraffin-embedded sections of synovial tissue from 12 patients with rheumatoid arthritis (RA), 14 with reactive arthritis (ReA), nine with other seronegative arthritis (OSA), seven with bacterial arthritis (BA), eight with probable bacterial arthritis (PBA) and eight with osteoarthritis (OA) were studied using the immunoperoxidase staining technique. The oncoproteins studied were expressed both in the synovial lining layer and in the sublining layer, consisting of lymphocytes, other inflammatory cells and blood vessels. Among the six disease entities, RA and OA appeared to be the most distinct, whereas the results obtained for ReA and OSA, and on the other hand for BA and PBA, closely resembled each other. The expression of Myc, Myb, Fos and Jun was significantly correlated both to the degree of synovial hypercellularity and the synovial lymphocytic infiltration. For Ras, such a correlation could not be seen. We conclude that we find no evidence of a cell lineage-specific or a disease-specific abnormality of proto-oncogene products in RA, and the expression of these oncoproteins is consistent with inflammation rather than with any primary abnormality of cell growth.

Cloning Aspergillus fumigatus allergens by the pJuFo filamentous phage display system

A cDNA library from Aspergillus fumigatus has been displayed on the surface of filamentous phage M13 and screened for gene products binding to human serum IgE. The physical linkage of cDNA gene products to the genetic information required for their production, achieved by exploiting the high-affinity interaction of the Jun and Fos leucine zippers, allows rapid and easier screening of large libraries in semifluid systems. The pJuFo cloning vector is designed to display proteins on the surface of phage and allows selective isolation of genes by gene product-ligand interaction. Thus the system is applicable to clone cDNA that encodes proteins for which a ligand is available. Herein we show that phage expressing IgE binding proteins from A. fumigatus can be enriched and separated from nonspecific phage by using serum IgE from A. fumigatus-allergic individuals coated to plastic dishes. Subsequently, the proteins can be produced in high amounts in Escherichia coli and purified for usage in allergy testing.

The temporal pattern of mating-induced immediate-early gene product immunoreactivity in LHRH and non-LHRH neurons of the estrous ferret forebrain

The mating-induced preovulatory surge of luteinizing hormone (LH) lasts for at least 12 h in the female ferret. This prolonged increase in circulating LH is presumably accompanied by a corresponding elevation in the activity and output of luteinizing hormone-releasing hormone (LHRH) neurons projecting to the hypothalamic-hypophyseal portal blood vessels and adenohypophysis. We used the protein products of the immediate early genes (IEGs) c-fos, and c-jun as markers of neural activation in order to determine whether a sub-population of LHRH neurons is differentially activated by mating and whether non-LHRH neurons in specific forebrain regions are selectively activated at different times during the mating-induced preovulatory LH surge. In Experiment 1, estrous female ferrets were perfused 0.5, 1.5, 3.0, 6.0 or 12.0 h after receiving one 5-min intromission from a male or after being placed alone in a testing cage for 20 min. Fos-like immunoreactivity (Fos-IR; Oncogene Ab-2 antiserum) and LHRH-like immunoreactivity (LHRH-IR; LR-1 antiserum) were visualized. The percentage of Fos-IR LHRH neurons was significantly augmented 1.5 h after mating but had returned to basal levels by 3.0 h. The double-labeled LHRH neurons were concentrated in the caudal medio-basal hypothalamus. In non-LHRH neurons the number of Fos-IR neural nuclei was significantly increased by mating in the medial preoptic area (MPOA), bed nucleus of the stria terminalis (BNST), medial amygdala (MA), ventrolateral hypothalamus (VLH), and midbrain central tegmental field (CTF) 1.5 h after mating but, as in LHRH neurons, had returned to basal levels by 3.0 h. In Experiment 2, estrous females were perfused 1.5 h or 8.0 h after either receiving one 5-min intromission or being placed alone in a testing cage, and the brains were processed for LHRH and c-Fos-like (DCH-1, Dr Gerard Evan), c-Jun-like (Jun-IR; Oncogene Ab-2) or Egr-1-like (Egr-IR; Santa Cruz) immunoreactivity. The percentage of LHRH neurons colabeled with both Fos-IR and Jun-IR was significantly greater in the 1.5 h group than in the unpaired group. Again, the induction of these IEG products occurred in LHRH neurons in the caudal medio-basal hypothalamus. Mating significantly increased the number of Fos-IR non-LHRH neural nuclei in the MPOA, BNST, MA, VMH and CTF, as well as the number of Egr-IR nuclei in the MPOA, BNST and MA in the 1.5 h group. By contrast, the number of Jun-IR non-LHRH neurons was unaffected by mating. In these Experiments we have identified a sub-population of LHRH neurons which, using Fos and Jun as markers of neural activation, is activated by mating and may be differentially involved in the generation of the preovulatory LH surge. Although the LHRH system is presumably activated throughout the duration of the 12 h preovulatory LH surge, c-Fos and c-Jun immunoreactivity in LHRH neurons is augmented only transiently. Fos-IR and Egr-IR in non-LHRH neurons show a similar time-course. Together, these results suggest that the presence of augmented levels of these proteins is not required for the maintenance or termination of the preovulatory output of LHRH.

Leucine zipper dimerized bivalent and bispecific scFv antibodies from a semi-synthetic antibody phage display library

This report describes the construction of leucine zipper-based dimerization cassettes for the conversion of recombinant monomeric scFv antibody fragments to bivalent and bispecific dimers. A truncated murine IgG3 hinge region and a Fos or Jun leucine zipper were cloned into four scFv fragments previously isolated from a synthetic antibody phage display library. Cysteine residues flanking the zipper region were introduced to covalently link dimerized scFv fragments. The secreted fusion proteins were shown to spontaneously and efficiently form stable Fos-Fos or Jun-Jun homodimers in the Escherichia coli periplasm at levels comparable to their monovalent counterparts. The bivalent (scFv)2 fragments performed well in enzyme-linked immunosorbent assay, flowcytometric, and immunohistochemical analysis. Fos and Jun homodimer (scFv)2 antibodies with different specificities could be reduced, reshuffled, and reoxidized to form preparations of functional bispecific (scFv)2 Fos-Jun heterodimers. These Fos and Jun fusion protein cassettes provide a universal basis for the construction of dimeric scFv antibodies with enhanced avidity or dual specificity.

Ionizing radiation-induced apoptosis is associated with c-Jun expression and c-Jun/AP-1 activation in the developing cerebellum of the rat

Previous studies have shown that ionizing radiation-induced cell death in the developing brain has morphological characteristics of apoptosis and is associated with internucleosomal DNA fragmentation. In the present study, we have observed c-Jun induction in cells sensitive to ionizing radiation during the whole process of radiation-induced cell death, and that this expression is accompanied by modifications in the composition of AP-1 complexes: c-Jun/AP-1 activity is highly increased whereas Jun D/AP-1 is slightly decreased. These results show that c-Jun expression and c-Jun/AP-1 activity are induced in the developing brain following ionizing radiation.

c-JUN, KROX-24, and c-FOS expression in hippocampal grafts placed in excitotoxic hippocampal lesions of the rat

Hippocampal transplants were examined for the expression of three specific immediate early gene encoded proteins in order to establish if grafted immature tissue maintains the basic molecular program necessary for gene transcription after grafting to excitotoxic (ibotenic acid-induced) lesions in adult host rat brains. The transplants were derived from newborn donor rats and were analyzed immunocytochemically for the presence of c-JUN, KROX-24, and c-FOS transcription factors 5 months after grafting. The expression and distribution patterns of these genes in the host hippocampus were identical to those in hippocampal neurons of normal untreated animals. c-JUN-, KROX-24-, and c-FOS-labeled neurons were also present in the transplants, where KROX-24 and c-FOS exhibited a distribution similar to host hippocampus. In contrast, c-JUN was more extensively expressed in the transplants, suggesting a molecular response to the grafting conditions and the actual graft-host brain interactions.

Alterations in immediate-early gene proteins in the rat forebrain induced by acute morphine injection

Injection of morphine (10 mg/kg) induced a complex immediate-early gene response in the rat forebrain, as detected with immunocytochemistry. The c-Fos protein was induced consistently in the dorsomedial caudate-putamen, the nucleus accumbens, and in midline and intralaminar nuclei of the thalamus. In some rats induction was also seen in the parietal and insular cortex and in lateral regions of the caudate-putamen. Induction was detectable, although weak, at 30 min, was maximal at 2 h, and was undetectable 3 h after injection. JunB was induced in the same regions of the caudate-putamen as found for c-Fos, but was not induced in the nucleus accumbens or thalamus. In the caudate-putamen, JunB induction was still present 3 h after injection. A considerably smaller induction of c-Jun was noted in the dorsomedial caudate-putamen and in deep neocortex. Expression of JunD was inhibited in intralaminar and midline thalamic nuclei. Increases in numbers of cells immunoreactive for a Jun-related antigen (Jra) were found in the caudate-putamen and nucleus accumbens. These results indicate a complex immediate-early gene response to acute morphine, suggesting that morphine activates or inhibits specific neurons and circuits in the forebrain.