Schwann cell O-GlcNAcylation promotes peripheral nerve remyelination via attenuation of the AP-1 transcription factor JUN.

Schwann cells (SCs), the glia of the peripheral nervous system, play an essential role in nerve regeneration. Upon nerve injury, SCs are reprogrammed into unique "repair SCs," and these cells remove degenerating axons/myelin debris, promote axonal regrowth, and ultimately remyelinate regenerating axons. The AP-1 transcription factor JUN is promptly induced in SCs upon nerve injury and potently mediates this injury-induced SC plasticity; however, the regulation of these JUN-dependent SC injury responses is unclear. Previously, we produced mice with a SC-specific deletion of O-GlcNAc transferase (OGT). This enzyme catalyzes O-GlcNAcylation, a posttranslational modification that is influenced by the cellular metabolic state. Mice lacking OGT in SCs develop a progressive demyelinating peripheral neuropathy. Here, we investigated the nerve repair process in OGT-SCKO mutant mice and found that the remyelination of regenerating axons is severely impaired. Gene expression profiling of OGT-SCKO SCs revealed that the JUN-dependent SC injury program was elevated in the absence of injury and failed to shut down at the appropriate time after injury. This aberrant JUN activity results in abnormalities in repair SC function and redifferentiation and prevents the timely remyelination. This aberrant nerve injury response is normalized in OGT-SCKO mice with reduced Jun gene dosage in SCs. Mechanistically, OGT O-GlcNAcylates JUN at multiple sites, which then leads to an attenuation of AP-1 transcriptional activity. Together, these results highlight the metabolic oversight of the nerve injury response via the regulation of JUN activity by O-GlcNAcylation, a pathway that could be important in the neuropathy associated with diabetes and aging.

Identification of differential protein-coding gene expressions in early phase lung adenocarcinoma.

BACKGROUND: The diagnosis of early phase lung adenocarcinoma (LADC) is associated with therapeutic strategy, effect, and survival time. However, the sensitive biomarkers of early phase LADC are still unclear. This study aimed to identify protein-coding genes that can be used as biomarkers of early stage LADC. METHODS: Gene microarray analysis was performed to identify key hub genes that show different expression in lung adenocarcinoma compared to normal tissues. The microarray data of lung adenocarcinoma in stages IA, IB, IIA, IIB, and normal tissues (GSE10072) were downloaded from a free online database, Gene Expression Omnibus (GEO). RESULTS: A total of 572 differentially expressed genes (DEGs) were identified between early phase lung adenocarcinoma and normal tissues using R software. Database for Annotation, Visualization and Integrated Discovery online tools were used to obtain Gene Ontology analysis and the Kyoto Encyclopedia of Genes and Genomes was used to analyze DEGs. Cytoscape software was used to express the protein-protein interaction network. We found that some cancer-related Gene Ontology terms and pathways (e.g. cell adhesion, cell surface receptor signaling pathway, PI3K-Akt signaling pathway) were significantly enriched in DEGs. CONCLUSION: Protein-coding genes JUN, FYN, CAV1, and SFN may play vital roles in the progress of early-stage lung adenocarcinoma. Consequently, through bioinformatics analysis, the key genes could be established to provide more potential references for the therapeutic targets of lung adenocarcinoma.

Cadherin complexes recruit mRNAs and RISC to regulate epithelial cell signaling.

Cumulative evidence demonstrates that most RNAs exhibit specific subcellular distribution. However, the mechanisms regulating this phenomenon and its functional consequences are still under investigation. Here, we reveal that cadherin complexes at the apical zonula adherens (ZA) of epithelial adherens junctions recruit the core components of the RNA-induced silencing complex (RISC) Ago2, GW182, and PABPC1, as well as a set of 522 messenger RNAs (mRNAs) and 28 mature microRNAs (miRNAs or miRs), via PLEKHA7. Top canonical pathways represented by these mRNAs include Wnt/ß-catenin, TGF-ß, and stem cell signaling. We specifically demonstrate the presence and silencing of MYC, JUN, and SOX2 mRNAs by miR-24 and miR-200c at the ZA. PLEKHA7 knockdown dissociates RISC from the ZA, decreases loading of the ZA-associated mRNAs and miRNAs to Ago2, and results in a corresponding increase of MYC, JUN, and SOX2 protein expression. The present work reveals a mechanism that directly links junction integrity to the silencing of a set of mRNAs that critically affect epithelial homeostasis.

Prognostic value of HMGA2, CDK4, and JUN amplification in well-differentiated and dedifferentiated liposarcomas.

HMGA2, CDK4, and JUN genes have been described as frequently coamplified with MDM2 in atypical lipomatous tumor, well-differentiated liposarcoma, and dedifferentiated liposarcoma. We studied the frequency of amplification of these genes in a series of 48 dedifferentiated liposarcomas and 68 atypical lipomatous tumors/well-differentiated liposarcomas. We correlated their amplification status with clinicopathological features and outcomes. Histologically, both CDK4 (P=0.007) and JUN (P=0.005) amplifications were associated with dedifferentiated liposarcoma, whereas amplification of the proximal parts of HMGA2 (5'-untranslated region (UTR) and exons 1-3) was associated with atypical lipomatous tumor/well-differentiated liposarcoma (P=0.01). CDK4 amplification was associated with axial tumors. Amplification of 5'-UTR and exons 1-3 of HMGA2 was associated with primary status and grade 1. Shorter overall survival was correlated with: age >64 years (P=0.03), chemotherapy used in first intent (P<0.001), no surgery (P=0.003), grade 3 (P<0.001), distant metastasis (P<0.001), node involvement (P=0.006), and CDK4 amplification (P=0.07). In multivariate analysis, distant metastasis (HR=8.8) and grade 3 (HR=18.2) were associated with shorter overall survival. A shorter recurrence-free survival was associated with dedifferentiated liposarcoma (P<0.001), grade 3 (P<0.001), node involvement (P<0.001), distant metastasis (P=0.02), recurrent status (P=0.009), axial location (P=0.001), and with molecular features such as CDK4 (P=0.05) and JUN amplification (P=0.07). Amplification of 5'-UTR and exons 1-3 (P=0.08) and 3'-UTR (P=0.01) of HMGA2 were associated with longer recurrence-free survival. Distant metastasis was associated with shorter recurrence-free survival (HR=5.8) in multivariate analysis. Dedifferentiated liposarcoma type was associated with axial location, grade 3 and recurrent status. In conclusion, we showed that the amplification of HMGA2 was associated with the atypical lipomatous tumor/well-differentiated liposarcoma histological type and a good prognosis, whereas CDK4 and JUN amplifications were associated with dedifferentiated liposarcoma histology and a bad prognosis. In addition, we also provided the first description of the molecular evolution of a well-differentiated liposarcoma into four successive dedifferentiated liposarcoma relapses, which was consistent with our general observations.

cJun promotes CNS axon growth.

A number of genes regulate regeneration of peripheral axons, but their ability to drive axon growth and regeneration in the central nervous system (CNS) remains largely untested. To address this question we overexpressed eight transcription factors and one small GTPase alone and in pairwise combinations to test whether combinatorial overexpression would have a synergistic impact on CNS neuron neurite growth. The Jun oncogene/signal transducer and activator of transcription 6 (JUN/STAT6) combination increased neurite growth in dissociated cortical neurons and in injured cortical slices. In injured cortical slices, JUN overexpression increased axon growth to a similar extent as JUN and STAT6 together. Interestingly, JUN overexpression was not associated with increased growth associated protein 43 (GAP43) or integrin alpha 7 (ITGA7) expression, though these are predicted transcriptional targets. This study demonstrates that JUN overexpression in cortical neurons stimulates axon growth, but does so independently of changes in expression of genes thought to be critical for JUNs effects on axon growth. We conclude that JUN activity underlies this CNS axonal growth response, and that it is mechanistically distinct from peripheral regeneration responses, in which increases in JUN expression coincide with increases in GAP43 expression.

The BTB-zinc finger transcription factor abrupt acts as an epithelial oncogene in Drosophila melanogaster through maintaining a progenitor-like cell state.

The capacity of tumour cells to maintain continual overgrowth potential has been linked to the commandeering of normal self-renewal pathways. Using an epithelial cancer model in Drosophila melanogaster, we carried out an overexpression screen for oncogenes capable of cooperating with the loss of the epithelial apico-basal cell polarity regulator, scribbled (scrib), and identified the cell fate regulator, Abrupt, a BTB-zinc finger protein. Abrupt overexpression alone is insufficient to transform cells, but in cooperation with scrib loss of function, Abrupt promotes the formation of massive tumours in the eye/antennal disc. The steroid hormone receptor coactivator, Taiman (a homologue of SRC3/AIB1), is known to associate with Abrupt, and Taiman overexpression also drives tumour formation in cooperation with the loss of Scrib. Expression arrays and ChIP-Seq indicates that Abrupt overexpression represses a large number of genes, including steroid hormone-response genes and multiple cell fate regulators, thereby maintaining cells within an epithelial progenitor-like state. The progenitor-like state is characterised by the failure to express the conserved Eyes absent/Dachshund regulatory complex in the eye disc, and in the antennal disc by the failure to express cell fate regulators that define the temporal elaboration of the appendage along the proximo-distal axis downstream of Distalless. Loss of scrib promotes cooperation with Abrupt through impaired Hippo signalling, which is required and sufficient for cooperative overgrowth with Abrupt, and JNK (Jun kinase) signalling, which is required for tumour cell migration/invasion but not overgrowth. These results thus identify a novel cooperating oncogene, identify mammalian family members of which are also known oncogenes, and demonstrate that epithelial tumours in Drosophila can be characterised by the maintenance of a progenitor-like state.

Neurological and muscular manifestations associated with influenza B infection in children.

BACKGROUND: Influenza viruses have been associated with various neurological and muscular symptoms. The aim of this study was to evaluate the pediatric neurological and muscular manifestations of influenza B during a 5-month epidemic at a single center. METHODS: We retrospectively reviewed the medical records of 355 pediatric patients with laboratory-confirmed influenza B infection. RESULTS: Neurological and muscular symptoms were exhibited by 28 patients (7.9%). The mean age was 48.7 ± 25.2 months. The mean time between respiratory symptoms and neurological symptoms was 2.2 ± 1.5 days. The most common symptom was seizure (19/28, 67.9%), followed by myositis (5/28, 17.9%), increased intracerebral pressure (1/28, 3.6%), delirium (1/28, 3.6%), and severe headache (1/28, 3.6%). There was one severe case of meningitis with myocarditis (1/28, 3.6%). All seizures were febrile: 15 simple febrile seizures (78.9%), three complex febrile seizures (15.8%), and one febrile status epilepticus (5.3%). The mean age of nine patients with their first seizures was 37.9 ± 22.2 months, which was older than the typical age of onset for febrile seizure. All the patients, except one, were treated with oseltamivir. There were no deaths or chronic debilitating sequelae. CONCLUSIONS: The neurological and muscular complications of influenza B infection in children are relatively mild, and febrile seizure is the most common. However, clinicians should be alert to the possibility of rare severe complications during influenza B outbreaks.

PDGFR blockade is a rational and effective therapy for NPM-ALK-driven lymphomas.

Anaplastic large cell lymphoma (ALCL) is an aggressive non-Hodgkin's lymphoma found in children and young adults. ALCLs frequently carry a chromosomal translocation that results in expression of the oncoprotein nucleophosmin-anaplastic lymphoma kinase (NPM-ALK). The key molecular downstream events required for NPM-ALK-triggered lymphoma growth have been only partly unveiled. Here we show that the activator protein 1 family members JUN and JUNB promote lymphoma development and tumor dissemination through transcriptional regulation of platelet-derived growth factor receptor-ß (PDGFRB) in a mouse model of NPM-ALK-triggered lymphomagenesis. Therapeutic inhibition of PDGFRB markedly prolonged survival of NPM-ALK transgenic mice and increased the efficacy of an ALK-specific inhibitor in transplanted NPM-ALK tumors. Notably, inhibition of PDGFRA and PDGFRB in a patient with refractory late-stage NPM-ALK(+) ALCL resulted in rapid, complete and sustained remission. Together, our data identify PDGFRB as a previously unknown JUN and JUNB target that could be a highly effective therapy for ALCL.

Auto-activation of c-JUN gene by amino acid deprivation of hepatocellular carcinoma cells reveals a novel c-JUN-mediated signaling pathway.

Mammalian cells respond to protein or amino acid (AA) limitation by activating a number of signaling pathways, collectively referred to as the AA response (AAR), that modulate a range of cellular functions, including transcriptional induction of target genes. This study demonstrates that in hepatocellular carcinoma cells, expression of c-JUN, JUN-B, c-FOS, and FOS-B was induced by the AAR, whereas JUN-D, FRA-1, and FRA-2 were not. Of the four activated FOS/JUN members, c-JUN made the largest contribution to the induction of several known AAR target genes. For several human liver, prostate, and ovarian cell lines, the AAR-induced increase in c-JUN expression was greater in transformed cells compared with nontransformed counterparts, an effect independent of cell growth rate. Thus far, the best characterized AA-responsive genes are all transcriptionally activated by ATF4, but the AAR-dependent induction of c-JUN transcription was ATF4-independent. The increased expression of c-JUN was dependent on ATF2 and on activation of the MEK-ERK and JNK arms of the MAPK signaling pathways. Formation of c-JUN-ATF2-activated heterodimers was increased after AA limitation, and c-JUN or ATF2 knockdown suppressed the induction of c-JUN and other AAR target genes. AA deprivation triggers a feed-forward process that involves phosphorylation of existing c-JUN protein by JNK and subsequent auto-activation of the c-JUN gene by recruitment of c-JUN and ATF2 to two AP-1 sites within the proximal promoter. The results document the novel observation that AP-1 sequences within the c-JUN gene can function as transcriptional amino acid-response elements.

Advanced glycation end products down-regulate gap junctions in human hepatoma SKHep 1 cells via the activation of Src-dependent ERK1/2 and JNK/SAPK/AP1 signaling pathways.

Hyperglycemia and advanced glycation end products (AGEs) are associated with an elevated risk of developing several cancers in diabetic patients. However, the detailed mechanisms remain to be elucidated. The mechanism of AGE-bovine serum albumin (BSA) on gap junction intercellular communication in human hepatoma cell line, SKHep 1, was investigated. Both Cx32 and Cx43 are major gap junction forming proteins in the liver, the loss of which has been shown to facilitate tumorigenesis. Although the MTT assay results showed that AGE-BSA significantly increased cell growth by 31%, AGE-BSA down-regulated Cx32 and Cx43 expression in a dose- and time-dependent manner. The present study also demonstrated that ERK1/2 and JNK/SAPK were significantly activated by AGE-BSA and that Src, ERK1/2, and JNK/SAPK inhibitors significantly reversed the reduction of Cx32 and Cx43 proteins by AGE-BSA. Taken together, these results strongly support the hypothesis that Src-dependent ERK1/2 and JNK/SAPK/AP1 signaling pathways play a key role in AGE-BSA-mediated down-regulation of Cx32 and Cx43 protein expression in SKHep 1 cells.

Peripheral facial nerve axotomy in mice causes sprouting of motor axons into perineuronal central white matter: time course and molecular characterization.

Generation of new axonal sprouts plays an important role in neural repair. In the current study, we examined the appearance, composition and effects of gene deletions on intrabrainstem sprouts following peripheral facial nerve axotomy. Axotomy was followed by the appearance of galanin(+) and calcitonin gene-related peptide (CGRP)(+) sprouts peaking at day 14, matching both large, neuropeptide(+) subpopulations of axotomized facial motoneurons, but with CGRP(+) sprouts considerably rarer. Strong immunoreactivity for vesicular acetylcholine transporter (VAChT) and retrogradely transported MiniRuby following its application on freshly cut proximal facial nerve stump confirmed their axotomized motoneuron origin; the sprouts expressed CD44 and alpha7beta1 integrin adhesion molecules and grew apparently unhindered along neighboring central white matter tracts. Quantification of the galanin(+) sprouts revealed a stronger response following cut compared with crush (day 7-14) as well as enhanced sprouting after recut (day 8 + 6 vs. 14; 14 + 8 vs. 22), arguing against delayed appearance of sprouting being the result of the initial phase of reinnervation. Sprouting was strongly diminished in brain Jun-deficient mice but enhanced in alpha7 null animals that showed apparently compensatory up-regulation in beta1, suggesting important regulatory roles for transcription factors and the sprout-associated adhesion molecules. Analysis of inflammatory stimuli revealed a 50% reduction 12-48 hours following systemic endotoxin associated with neural inflammation and a tendency toward more sprouts in TNFR1/2 null mutants (P = 10%) with a reduced inflammatory response, indicating detrimental effects of excessive inflammation. Moreover, the study points to the usefulness of the facial axotomy model in exploring physiological and molecular stimuli regulating central sprouting.

Activator protein-1 transcription factors are associated with progression and recurrence of prostate cancer.

To identify biomarkers that discriminate the aggressive forms of prostate cancer, we performed gene expression profiling of prostate tumors using a genetically engineered mouse model that recapitulates the stages of human prostate cancer, namely Nkx3.1; Pten mutant mice. We observed a significant deregulation of the epidermal growth factor and mitogen-activated protein kinase (MAPK) signaling pathways, as well as their major downstream effectors--the activator protein-1 transcription factors c-Fos and c-Jun. Forced expression of c-Fos and c-Jun in prostate cancer cells promotes tumorigenicity and results in activation of extracellular signal-regulated kinase (Erk) MAPK signaling. In human prostate cancer, up-regulation of c-Fos and c-Jun proteins occurs in advanced disease and is correlated with Erk MAPK pathway activation, whereas high levels of c-Jun expression are associated with disease recurrence. Our analyses reveal a hitherto unappreciated role for AP-1 transcription factors in prostate cancer progression and identify c-Jun as a marker of high-risk prostate cancer. This study provides a striking example of how accurate mouse models can provide insights on molecular processes involved in progression and recurrence of human cancer.

Rapamycin antagonizes NF-kappaB nuclear translocation activated by TNF-alpha in primary vascular smooth muscle cells and enhances apoptosis.

Several lines of evidence support the view that rapamycin inhibits NF-kappaB. TNF-alpha, a potent inducer of NF-kappaB, is released after artery injury (e.g., balloon angioplasty) and plays an important role in inflammation and restenosis. We investigated the effect of rapamycin on NF-kappaB activation and apoptosis in vascular smooth muscle cells (VSMCs) stimulated with TNF-alpha. Using EMSA, we found that TNF-alpha caused NF-kappaB nuclear translocation in VSMCs after 1 h of incubation. Rapamycin inhibited IkappaBalpha degradation, thereby preventing nuclear translocation. Activation of NF-kappaB was accompanied by an increase of Bcl-xL and Bfl-1/A1 proteins, detected by Western blot assay, whereas rapamycin prevented the TNF-alpha-induced enhancement of these antiapoptotic proteins. The extent of apoptosis of VSMCs exposed to TNF-alpha was significantly enhanced by rapamycin. The effect of rapamycin appeared to be independent of the phosphatidylinositol 3-kinase/Akt-protein kinase B survival pathway, because the phosphatidylinositol 3-kinase inhibitor wortmannin neither prevented IkappaBalpha degradation nor increased apoptosis of cells incubated with TNF-alpha. Finally, we demonstrate that the large immunophilin FK-506 binding protein FKBP51 is essential for TNF-alpha-induced NF-kappaB activation in VSMCs. Our findings show that rapamycin inhibits NF-kappaB activation and acts in concert with TNF-alpha in induction of VSMC apoptosis.

Arsenic trioxide induces apoptosis of human monocytes during macrophagic differentiation through nuclear factor-kappaB-related survival pathway down-regulation.

Arsenic trioxide (As(2)O(3)) is known to be toxic toward leukemia cells. In this study, we determined its effects on survival of human monocytic cells during macrophagic differentiation, an important biological process involved in the immune response. As(2)O(3) used at clinically relevant pharmacological concentrations induced marked apoptosis of human blood monocytes during differentiation with either granulocyte-macrophage colony-stimulating factor or macrophage colony-stimulating factor. Apoptosis of monocytes was associated with increased caspase activities and decreased DNA binding of p65 nuclear factor-kappaB (NF-kappaB); like As(2)O(3), the selective NF-kappaB inhibitor (E)-3-[(4-methylphenyl)-sulfonyl]-2-propenenitrile (Bay 11-7082) strongly reduced survival of differentiating monocytes. The role of NF-kappaB in arsenic toxicity was also studied in promonocytic U937 cells during phorbol 12-myristate 13-acetate-induced macrophagic differentiation. In these cells, As(2)O(3) first reduced DNA binding of p65 NF-kappaB and subsequently induced apoptosis. In addition, overexpression of the p65 NF-kappaB subunit, following stable infection with a p65 retroviral expressing vector, increased survival of As(2)O(3)-treated U937 cells. As(2)O(3) specifically decreased protein levels of X-linked inhibitor of apoptosis protein and FLICE-inhibitory protein, two NF-kappaB-regulated genes in both U937 cells and blood monocytes during their differentiations. Finally, As(2)O(3) was found to inhibit macrophagic differentiation of monocytic cells when used at cytotoxic concentrations; however, overexpression of the p65 NF-kappaB subunit in U937 cells reduced its effects toward differentiation. In contrast to monocytes, well differentiated macrophages were resistant to low concentrations of As(2)O(3). Altogether, our study demonstrates that clinically relevant concentrations of As(2)O(3) induced marked apoptosis of monocytic cells during in vitro macrophagic differentiation likely through inhibition of NF-kappaB-related survival pathways.

Anti-inflammatory effects of moxifloxacin on IL-8, IL-1beta and TNF-alpha secretion and NFkappaB and MAP-kinase activation in human monocytes stimulated with Aspergillus fumigatus.

OBJECTIVES: We have previously shown that moxifloxacin conferred protective anti-inflammatory effects against Candida pneumonia in immunosuppressed mice. Further in vitro studies showed anti-inflammatory effects of moxifloxacin in LPS and cytokine-stimulated monocytic and epithelial cells. In the present study, concentrating on a more challenging pathogen of immunosuppressed hosts, we studied the effect of moxifloxacin on cytokine secretion and signal transduction mechanisms in monocytic cells stimulated with Aspergillus fumigatus. METHODS: Human peripheral blood monocytes (PBMCs) and a human monocytic cell line (THP-1) were incubated with 1.5x10(6)/mL conidia of a clinical isolate of A. fumigatus. Cytokine secretion and activation of NFkappaB and the MAP-kinases ERK1/2 and p38 were measured with and without the addition of moxifloxacin (5-20 mg/L). RESULTS: Stimulation of PBMCs and THP-1 cells with A. fumigatus increased IL-8, IL-1beta and TNF-alpha secretion (4.1-, 8.3- and 7-fold, and 5.4-, 3.7- and 17.8-fold, respectively). Addition of moxifloxacin (5-20 mg/L) inhibited cytokine secretion up to 45.7+/-5%, 72+/-13% and 73+/-10% in PBMCs and up to 35.6+/-0.5%, 30+/-2.4% and 19+/-4% in THP-1 cells (P<0.05). Signal transduction studies showed that incubation of THP-1 cells with A. fumigatus increased ERK1/2 and p38 phosphorylation and p65-NFkappaB protein expression by 1.6-, 1.3- and 1.8-fold, respectively. Addition of moxifloxacin inhibited ERK1/2, p38 and p65-NFkappaB by up to 69+/-14%, 58+/-3% and 75+/-15%, respectively. CONCLUSIONS: Our results indicate that moxifloxacin acts as an anti-inflammatory agent in monocytic cells stimulated with A. fumigatus conidia. Whether these effects may be protective as in the Candida pneumonia model is unknown and merits in vivo studies in models of pulmonary aspergillosis.

The v-Jun point mutation allows c-Jun to escape GSK3-dependent recognition and destruction by the Fbw7 ubiquitin ligase.

The c-Jun and c-Myc oncogenic transcription factors are highly unstable proteins due to polyubiquitination. Similar to c-Myc, we report here that phosphorylation of c-Jun by GSK3 creates a high-affinity binding site for the E3 ligase Fbw7, which targets c-Jun for polyubiquitination and proteasomal degradation. In keeping with this, we found that c-Jun levels were inversely related to GSK3 activity in mammalian cells that had entered the cell cycle. Importantly, phosphorylation of c-Jun by GSK3 requires a priming phosphorylation event at Ser-243. Ser-243 is mutated to phenylalanine in v-Jun and allows it to escape recognition by Fbw7. These findings explain the enhanced stability and oncogenicity of v-Jun relative to its cellular counterpart and reveal that GSK3 and Fbw7 coordinately regulate c-Jun and c-Myc.

Overexpression of the full-length neurotrophin receptor trkB regulates the expression of plasticity-related genes in mouse brain.

Significant body of evidence indicates an important role for brain-derived neurotrophic factor (BDNF) in the hippocampal synaptic plasticity; however, the exact mechanisms how the BDNF signal is converted to plastic changes during memory processes are under an intense investigation. To specifically address the role of the trkB receptor, we have previously generated transgenic mice overexpressing the full-length trkB receptor and observed a continuous activation of the trkB.TK+ receptor, improved learning and memory but an attenuated LTP in these mice. In this study, we describe the trkB.TK+ mRNA and protein distribution in the transgenic mice, showing the most prominent increase in the full-length trkB expression in the cortical layer V pyramidal neurons and dentate gyrus of the hippocampus. In addition, we have analyzed the mRNA expression patterns of a group of genes associated with both plastic changes in the nervous system and BDNF signaling. Regulated expression of immediate early genes c-fos, fra-2 and junB was observed in the transgenic mice. Furthermore, the mRNA expression of alpha-Ca2+/calmodulin-dependent kinase II (alpha-CaMKII) was reduced in both the hippocampus and parietal cortex, whereas growth-associated protein 43 (GAP-43) mRNA expressions were induced in the corresponding regions. Conversely, the mRNA expression of the transcription factor cAMP response element binding protein (CREB) was not altered in the trkB.TK+mice. Finally, the density of neuropeptide Y (NPY)-expressing cells was increased in the trkB.TK+ mice dentate hilus. Altogether, these results demonstrate in vivo that the increased trkB.TK+ signaling regulates several important plasticity-related genes.

Differential expression of mitogen-activated protein kinases and immediate early genes fos and jun in thalamus in schizophrenia.

Despite a growing body of evidence demonstrating that mitogen-activated protein (MAP) kinase pathways play an important physiological role in the CNS, little is known about their role and function in various mental disorders including schizophrenia. Our previous studies have shown increased expression of several intermediates of the extracellular signal-regulated (ERK) cascade and downstream transcription targets in cerebellar vermis without any changes in mesopontine tegmentum and Brodmann's area 10 in patients with schizophrenia. Given the evidence for abnormalities in schizophrenia in a neural circuit involving the cerebellum and thalamus, the present study was conducted to examine the expression of MAP kinases extracellular signal-regulated kinase (ERK), c-Jun-N-terminal kinase (JNK) and p38, as well as immediate early genes fos (c-fos and fos B) and jun (c-jun, jun B and jun D) using a Western blot analysis and reverse transcription polymerase chain reaction (RT-PCR) in postmortem thalamus from schizophrenic and control subjects. There were significant increase in ERK2, c-fos and c-jun protein and mRNA levels in thalamus of patients with schizophrenia relative to controls. No statistically significant differences were found for ERK1, Fos B, Jun B or Jun D proteins in schizophrenic and control subjects. These results taken together with our previous findings provide new evidence for selective abnormalities of distinct MAP kinases and immediate early genes c-fos and c-jun in a circuit involving the thalamus and cerebellum, which may contribute significantly to the pathophysiology of schizophrenia.

Jun oncoproteins do not function as primary transcription factors for the mouse major histocompatibility complex class I H-2 genes in fibroblasts.

There are several reports in the literature focusing on regulation of major histocompatibility complex (MHC) class I genes by transcription factors of the jun family. The methods employed in these reports differed in various respects, and their results are inconsistent. In mouse Lewis lung carcinoma, B16-melanoma and F9-teratocarcinoma cell lines, c-jun was characterized as a transcriptional activator of the murine MHC class I H2-Kb gene, while c-jun was identified as a direct transcriptional repressor of the swine class I PD1 gene, and c-jun stably transfected clones of mouse L-fibroblasts markedly reduced their H-2 class I gene expression. In this study, we attempted to reproduce this last effect by means of transient transfection coupled to Northern hybridization, upon transfecting L-fibroblasts with expression vectors for all jun family members as well as with an array of c-jun-derived dominant negative mutants. No change in H-2 class I expression could be identified. Next, we derived two additional fibroblastic cell lines from the fibrosarcoma of the H2-Kk/v-jun transgenic mouse and transfected them with the two most potent c-jun dominant negative mutants, again without eliciting any change in H-2 class I mRNA level. We conclude that the negative regulation of H-2 class I genes by c-jun in cells of the fibroblastic lineage is not a primary effect.

v-Jun stimulates both cdk2 kinase activity and G1/S progression via transcriptional repression of p21 CIP1.

Previous studies have shown that the viral Jun (v-Jun) oncoprotein induces marked alterations in cell cycle control, which are associated with, and may be caused by, increased cdk2 kinase activity. Since p21 CIP1 is an important regulator of cdk2, we investigated whether aberrant expression of this cyclin-dependent kinase inhibitor might contribute to cell cycle deregulation by v-Jun. We find that the basal levels of p21 CIP1 mRNA and protein expression are greatly reduced in chick embryo fibroblasts (CEF) transformed by v-Jun, and that v-Jun blocks the increases in p21 CIP1 expression that normally accompany growth inhibition induced by serum deprivation or confluency in untransformed CEF. Importantly, ectopic expression of p21 CIP1 in v-Jun-transformed CEF inhibits both cdk2 kinase activity and cell cycle progression, indicating that these alterations in p21 CIP1 expression are likely to be functionally significant for growth deregulation. We also investigated the mechanism through which v-Jun disturbs p21 CIP1 expression and the possible involvement of a known p21 CIP1 regulator, p53, as an intermediate in this process. This analysis revealed that repression is mediated primarily at the level of p21 CIP1 gene transcription, however the mechanism is complex; both p53-dependent and -independent mechanisms contribute as judged by analysis of p21 CIP1 promoter mutants and other assays of p53 transcriptional activity.