CREB DNA Binding Activity Research Articles

Roles of constitutive and signal-dependent protein phosphatase 2A docking motifs in burst attenuation of the cyclic AMP response element-binding protein

The cAMP response element-binding protein (CREB) is an important regulator of cell growth, metabolism, and synaptic plasticity. CREB is activated through phosphorylation of an evolutionarily conserved Ser residue (S133) within its intrinsically disordered kinase-inducible domain (KID). Phosphorylation of S133 in response to cAMP, Ca2+, and other stimuli triggers an association of the KID with the KID-interacting (KIX) domain of the CREB-binding protein (CBP), a histone acetyl transferase (HAT) that promotes transcriptional activation. Here we addressed the mechanisms of CREB attenuation following bursts in CREB phosphorylation. We show that phosphorylation of S133 is reversed by protein phosphatase 2A (PP2A), which is recruited to CREB through its B56 regulatory subunits. We found that a B56-binding site located at the carboxyl-terminal boundary of the KID (BS2) mediates high-affinity B56 binding, while a second binding site (BS1) located near the amino terminus of the KID mediates low affinity binding enhanced by phosphorylation of adjacent casein kinase (CK) phosphosites. Mutations that diminished B56 binding to BS2 elevated both basal and stimulus-induced phosphorylation of S133, increased CBP interaction with CREB, and potentiated the expression of CREB-dependent reporter genes. Cells from mice harboring a homozygous CrebE153D mutation that disrupts BS2 exhibited increased S133 phosphorylation stoichiometry and elevated transcriptional bursts to cAMP. These findings provide insights into substrate targeting by PP2A holoenzymes and establish a new mechanism of CREB attenuation that has implications for understanding CREB signaling in cell growth, metabolism, synaptic plasticity, and other physiologic contexts.

Compound matrine injection reduces morphine tolerance of the mice with lung cancer by inhibiting expression of multidrug resistance gene 1 and P-glycoprotein

Objective: To investigate the effect of compound matrine injection on morphine tolerance in mice with lung cancer in situ and the expressions of multidrug resistance gene 1 (MDR1) and P-glycoprotein (P-gp). Methods: A mouse model of lung cancer in situ and morphine tolerance mode was established. The mice were injected with gradient concentration of compound matrine. The pain thresholds under different conditions were measured by thermal radiation tail-flick method. The mRNA level of MDR1 was tested by reverse transcription polymerase chain reaction (RT-PCR) and the protein level of P-gp was detected by western blot. The DNA binding activity of cyclophosphoadenosine response element binding protein (CREB) to the promoter of MDR1 gene was detected by electrophoretic mobility shift assay (EMSA). Results: The maximum analgesic percentage (MPE) of the mice in the morphine group was (85.21±6.53)% on the 8th day, and decreased to (38.45±5.52)% and (28.14±4.52)% on the 10th and 12th day, respectively, which indicated the morphine tolerance of mice with lung cancer in situ.The MPE of the mice in the group treated with morphine and compound matrine injection (300 mg/kg) was (79.34±6.50)% on the 8th day, and decreased to (62.16±5.53)% and (40.20±4.50)% on the 10th and 12th day, respectively.The results of RT-PCR assay showed that the relative expression levels of MDR1 mRNA in the brain tissues of mice in the morphine group, saline group, morphine combined with compound matrine injection (300 mg/kg) group and compound matrine injection (200 mg/kg) group were 2.33±0.79, 1.04±0.38, 1.37±0.38, and 1.43±0.53, respectively. There were statistically significant differences between the morphine group and the normal saline group, the morphine group and the morphine combined with compound matrine injection (300 mg/kg) group (P<0.05). There was no significant difference between the normal saline group and the compound matrine injection (200 mg/kg) group (P=0.05). The results of western blot showed that the relative expression levels of P-gp protein in the brain tissue of mice in the morphine group, saline group, and morphine combined with compound matrine injection (300 mg/kg) group were 1.86±0.40, 1.00±0.23, and 1.27±0.27, respectively. The expression of P-gp protein in the morphine group was significantly higher than those of the normal saline group and the morphine combined with compound matrine injection (300 mg/kg) group (P<0.05). The DNA-binding activity of CREB in the saline group was (0.23±0.07) Pu, significantly lower than (0.89±0.23) Pu of morphine combined with naloxone group and (0.80±0.23) Pu of morphine group (P<0.05). While the CREB DNA binding activity of morphine combined with compound matrine injection (300 mg/kg) group was (0.79±0.21) Pu, implicated that compound matrine had marginal effect on the DNA-binding activity of CREB (P>0.05). Conclusion: Compound matrine injection can significantly improve morphine tolerance and drug resistance of lung cancer through inhibiting the upregulations of MDR1 and P-gp induced by morphine.

Role of the p38 MAPK/C/EBPβ Pathway in the Regulation of Phenotype and IL-10 and IL-12 Production by Tolerogenic Bone Marrow-Derived Dendritic Cells.

Dendritic cells (DCs) play a major role in innate and adaptive immunity and self-immune tolerance. Immunogenic versus tolerogenic DC functions are dictated by their levels of costimulatory molecules and their cytokine expression profile. The transcription factor C/EBPβ regulates the expression of several inflammatory genes in many cell types including macrophages. However, little is known regarding the role of C/EBPβ in tolerogenic versus immunogenic DCs functions. We have previously reported that bone marrow-derived DCs generated with GM-CSF (GM/DCs) acquire the signature of semi-mature tolerogenic IL-10-producing DCs as opposed to immunogenic DCs generated with GM-CSF and IL-4 (IL-4/DCs). Here, we show that tolerogenic GM/DCs exhibit higher levels of phosphorylation and enhanced DNA binding activity of C/EBPβ and CREB than immunogenic IL-4/DCs. We also show that the p38 MAPK/CREB axis and GSK3 play an important role in regulating C/EBPβ phosphorylation and DNA binding activity. Inhibition of p38 MAPK in GM/DCs resulted in a drastic decrease of C/EBPβ and CREB DNA binding activities, a reduction of their IL-10 production and an increase of their IL-12p70 production, a characteristic of immunogenic IL-4/DCs. We also present evidence that GSK3 inhibition in GM/DCs reduced C/EBPβ DNA binding activity and increased expression of costimulatory molecules in GM/DCs and their production of IL-10. Analysis of GM/DCs of C/EBPβ−/− mice showed that C/EBPβ was essential to maintain the semimature phenotype and the production of IL-10 as well as low CD4+ T cell proliferation. Our results highlight the importance of the p38MAPK-C/EBPβ pathway in regulating phenotype and function of tolerogenic GM/DCs.

Alpinetin exerts anti-colitis efficacy by activating AhR, regulating miR-302/DNMT-1/CREB signals, and therefore promoting Treg differentiation

Alpinetin, a flavonoid compound extracted from the seeds of Alpinia katsumadai Hayata, has been demonstrated to exert massive biological properties. This study aimed to evaluate the effect of alpinetin on dextran sulfate sodium (DSS)-induced colitis, and elucidate the potential mechanisms. Alpinetin significantly alleviated colitis in mice, accompanied with restored Th17/Treg balance in colons. In vitro, alpinetin directly promoted Treg differentiation but exerted little effect on Th17 differentiation, and the action was in an aryl hydrocarbon receptor (AhR)-dependent manner. It acted as a potential AhR activator, evidenced by increased expression of CYP1A1, dissociation of AhR/HSP90 complexes, AhR nuclear translocation, XRE-driven luciferase reporter gene and DNA-binding activity of AhR/ARNT/XRE in T cells. Furthermore, alpinetin significantly promoted expression of miR-302 but not others, and restrained expression of DNMT-1 and methylation level of Foxp3 promoter region in CD4+ T cells and colons of colitis mice. However, the association of CREB and Foxp3 promoter region but not expression, nuclear translocation and DNA-binding activity of CREB was up-regulated by alpinetin in CD4+ T cells. The relationship of alpinetin-adjusted AhR activation, expressions of miR-302 and DNMT-1, association of CREB and Foxp3 promoter region, and Treg differentiation was confirmed by using CH223191, siAhR, miR-302 inhibitor and pcDNA3.1(+)-mDNMT-1. Finally, CH223191 abolished the amelioration of alpinetin on colitis, induction of Treg cells and regulation of miR-302/DNMT-1/CREB signals in colons of colitis mice. In conclusion, alpinetin ameliorated colitis in mice via activating AhR, regulating miR-302/DNMT-1/CREB signals, therefore promoting Treg differentiation.

Glabridin inhibits osteosarcoma migration and invasion via blocking the p38- and JNK-mediated CREB-AP1 complexes formation.

Osteosarcoma is the most common bone malignancy, and it seriously affects the quality of life of affected children and adolescents. Glabridin (GLA), a major component of licorice root extract, has been reported to exert antitumor effects against a variety of tumor types; however, its effects on osteosarcoma have not been elucidated. In the current study, we investigate the effects and potential antimetastatic mechanisms of GLA on osteosarcoma in vitro and in vivo. Flow cytometry showed that GLA induced G2/M cell cycle phase arrest and promoted cell apoptosis. Transwell and wound-healing assays showed that GLA significantly decreased the migration and invasion of osteosarcoma cells. Further western blotting and quantitative real-time polymerase chain reaction showed that the expression of matrix metalloproteinase (MMP)-2 and MMP-9 in MG63 and HOS cells were reduced after GLA treatment. Moreover, western blotting demonstrated that GLA downregulated the phosphorylation of p38 mitogen-activated protein kinases and c-Jun N-terminal kinase. A coimmunoprecipitation assay illustrated that formation of cAMP response element-binding protein (CREB)-activating protein 1 (AP1) complexes and the DNA binding activities of CREB and AP1 in MG63 and HOS cells were impaired following treatment with GLA. Finally, GLA inhibited tumor growth and suppressed osteosarcoma cell metastasis in vivo. Overall, our findings highlight the potential of GLA as a therapeutic agent for the prevention and treatment of tumor metastasis.

Andrographolide suppresses the migratory ability of human glioblastoma multiforme cells by targeting ERK1/2-mediated matrix metalloproteinase-2 expression.

Glioblastoma multiforme (GBM) can be a fatal tumor because of difficulties in treating the related metastasis. Andrographolide is the bioactive component of the Andrographis paniculata. Andrographolide possesses the anti-inflammatory activity and inhibits the growth of various cancers; however, its effect on GBM cancer motility remains largely unknown. In this study, we examined the antimetastatic properties of andrographolide in human GBM cells. Our results revealed that andrographolide inhibited the invasion and migration abilities of GBM8401 and U251 cells. Furthermore, andrographolide inhibited matrix metalloproteinase (MMP)-2 activity and expression. Real-time PCR and promoter activity assays indicated that andrographolide inhibited MMP-2 expression at the transcriptional level. Such inhibitory effects were associated with the suppression of CREB DNA-binding activity and CREB expression. Mechanistically, andrographolide inhibited the cell motility of GBM8401 cells through the extracellular-regulated kinase (ERK) 1/2 pathway, and the blocking of the ERK 1/2 pathway could reverse MMP-2-mediated cell motility. In conclusion, CREB is a crucial target of andrographolide for suppressing MMP-2-mediated cell motility in GBM cells. Therefore, a combination of andrographolide and an ERK inhibitor might be a good strategy for preventing GBM metastasis.

Treadmill exercise alleviated prenatal buprenorphine exposure-induced depression in rats

Mounting evidence suggests that physical exercise shows health benefits in a range of diseases, including psychiatric disorders. Perinatal opioid exposure produces neurobehavioral abnormality, which includes depression symptoms, in patients and their offspring following chronic use of buprenorphine, a mixed agonist/antagonist with a high affinity to opioid receptors, for pain control. Previously, we demonstrated that prenatal buprenorphine exposure in pregnant Sprague-Dawley rats starting from gestation day 7 and lasting for 14 days caused the development of depression-like phenotypes in pups at postnatal day 21. Using the same prenatal buprenorphine exposure model, we further demonstrated that a 4-week course of moderate treadmill exercise conducted on pups starting from postnatal day 22 improved depression-like neurobehaviors. Prenatal buprenorphine exposure-induced neurobehavioral changes were accompanied by reductions of neuronal survival, neural stem cell-associated genes, plasma level of brain-derived neurotrophic factor (BDNF) and serotonin, phosphorylated tropomyosin-related kinase receptor type B (TrkB), phosphorylated extracellular signal-regulated kinase (ERK), PKA activity, phosphorylated cAMP response element-binding protein (CREB), and CREB DNA binding activity, as well as elevation of repressor element-1 silencing transcription factor (REST), oxidative stress, and inflammatory responses. Those changes in parameters of plasma and brain were improved by treadmill exercise. In conclusion, the findings of the current study suggest that a non-pharmacological option, i.e., moderate treadmill exercise, alleviated the development of depression-like neurobehaviors by resolving the oxidative and inflammatory burden as well as by enhancing neurochemical and neuroendocrine signaling.

Interplay of inflammatory gene expression in pericytes following Japanese encephalitis virus infection

Neuroinflammation is a pathological hallmark and has been implicated in the pathogenesis of Japanese encephalitis. Although brain pericytes show regulatory effects on neuroinflammation, their involvement in Japanese encephalitis-associated neuroinflammation is not understood. Here, we demonstrated that brain microvascular pericytes could be an alternative cellular source for the induction and/or amplification of neuroinflammation caused by Japanese encephalitis virus (JEV) infection. Infection of cultured pericytes with JEV caused profound production of IL-6, RANTES, and prostaglandin E2 (PGE2). Mechanistic studies revealed that JEV infection elicited an elevation of the toll-like receptor 7 (TLR7)/MyD88 signaling axis, leading to the activation of NF-κB through IKK signaling and p65 phosphorylation as well as cAMP response element-binding protein (CREB) via phosphorylation. We further demonstrated that extracellular signal-regulated kinase (ERK) could be an alternative regulator in transducing signals to NF-κB, CREB, and cytosolic phospholipase A2 (cPLA2) through the phosphorylation mechanism. Released IL-6 and RANTES played an active role in the disruption of endothelial barrier integrity and leukocyte chemotaxis, respectively. cPLA2/PGE2 had a role in activating NF-κB and CREB DNA-binding activities and inflammatory cytokine transcription via the EP2/cAMP/PKA mechanism in an autocrine loop. These inflammatory responses and biochemical events were also detected in the brain of JEV-infected mice. The current findings suggest that pericytes might have pathological relevance in Japanese encephalitis-associated neuroinflammation through a TLR7-related mechanism. The consequences of pericyte activation are their ability to initiate and/or amplify inflammatory cytokine expression by which cellular function of endothelial cells and leukocytes are regulated in favor of CNS infiltration by leukocytes.

Abstract 4093: t-Darpp stimulates protein kinase A activity by interacting with its RI regulatory subunit

Abstract t-Darpp is the truncated form of the dopamine- and cAMP-regulated phosphoprotein of 32 kDa (Darpp-32) and has been demonstrated to confer resistance to trastuzumab, a Her2-targeted anticancer agent, via sustained signaling through the phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/Akt pathway. t-Darpp over-expression results in enhanced activity of protein kinase A (PKA), but the mechanism of t-Darpp-mediated PKA activation is poorly understood. In the PKA holoenzyme, when the catalytic subunits are bound to regulatory subunits RI or RII, kinase activity is inhibited. We investigated PKA activity and holoenzyme composition in cell lines that over-express t-Darpp (SK.tDrp) or a T75A phosphorylation mutant (SK.tDrp.T75A), as well as an empty vector control cell line (SK.empty). We also evaluated protein-protein interactions between t-Darpp and PKA catalytic (PKAc) or regulatory subunits RI and RII in those cell lines. Whereas SK.tDrp cells had elevated PKA activity, SK.tDrp.T75A cells did not. In agreement with the effects on activity, a proximity ligation assay showed that SK.tDrp cells, but not SK.tDrp.T75A cells, had diminished association of RI with PKAc. Moreover, t-Darpp was seen to bind directly to RI in co-immunoprecipitation studies. Cells that express both Darpp-32 and t-Darpp had PKA activity levels and RI-PKAc association that were similar to control SK.empty cells. This is consistent with our published findings that Darpp-32 reverses t-Darpp’s effects on trastuzumab resistance and CREB DNA binding activity (downstream of PKA). Taken together, our data suggest that T75 phosphorylation is crucial for t-Darpp-mediated PKA activation and this activation appears to occur through direct binding to RI and release of RI from PKAc. The t-Darpp-RI interaction could be a druggable target to reduce PKA activity in drug-resistant cancer. Citation Format: Dirk Theile, Shuhui Geng, Erin Denny, Jamil Momand, Susan E. Kane. t-Darpp stimulates protein kinase A activity by interacting with its RI regulatory subunit [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4093. doi:10.1158/1538-7445.AM2017-4093

P21-Associated Kinase 4 (PAK4) Addiction in Multiple Myeloma: A Potential Therapeutic Application with Enhanced Activity in FGFR3 Expressing Myeloma

Dysregulated oncogenic serine/threonine kinases (STKs) play a pathological role in diverse forms of malignancies, including multiple myeloma (MM), and thus represent potential therapeutic targets. Here, we evaluated the biological and functional role of p21-activated kinase 4 (PAK4), and its potential as a new therapeutic target in MM. The PAK4 gene lies within chromosome region 19q13.2 commonly amplified in 30% of MM patients. We confirmed a correlation between copy number amplification and increased expression of PAK4 in two large myeloma patient datasets. High expression of total and phosphorylated PAK4 was also observed in the premalignant MGUS stage, suggesting that its overexpression may be an early event in the pathogenesis of myeloma. Myeloma cells with high PAK4 expression display sensitivity to conditional PAK4 knockdown, implying that an oncogene-addicted state exists in such cells. Moreover, we show that PAK4 promotes myeloma cell proliferation in vitro as well as in vivo in murine models of human myeloma through activation of the MEK/ERK pathway. This is further highlighted by the correlation between the basal levels of ERK activity and sensitivity to a novel small molecule inhibitor of PAK4, KPT-9274, a lead clinical agent. KPT-9274 effectively inhibits MM cell growth and survival via ERK inhibition in a large panel of MM cell lines and primary MM cells, also in the presence of bone marrow microenvironment, with no significant effect on normal PBMCs suggesting a potentially favorable therapeutic index. Inhibition of ERK by KPT-9274 also correlates with decreased DNA binding activity of ERK-dependent transcription factors AP1, ETS, CREB and EGR and decreased expression of ERK target genes such as CCND2, CCR1 and MYC. Finally, using a protein binding array, we have identified FGFR3, a commonly disrupted tyrosine kinase receptor, and Grb2, an adaptor protein involved in RAS activation, as novel PAK4 binding partners in myeloma and report disruption of this binding by KPT-9274. As a results, t(4;14)-positive MM cells expressing FGFR3 show greater sensitivity to PAK4 inhibition compared to MM cell lines without FGFR3 aberrations (e.g. U266 and ANBL6). FGFR3 may therefore serve as a predictive marker of KPT-9274 sensitivity in MM patients, with the potential for broader application to other malignancies associated with dysregulation of FGFR3 such as human bladder and cervical carcinomas.In conclusions, our study sheds light on the oncogenic role of the serine/threonine kinase PAK4 as survival and anti-apoptotic factor in myeloma and its inhibition with a new allosteric modulator, KPT-9274, as a potential novel therapeutic intervention in MM especially in high risk t(4:14)-positive patients. DisclosuresSenapedis:Karyopharm Therapeutics Inc: Employment. Oliva:Celgene: Honoraria; Takeda: Honoraria; Amgen: Honoraria. Anderson:Gilead: Membership on an entity's Board of Directors or advisory committees; Oncoprep: Equity Ownership; Oncoprep: Equity Ownership; Gilead: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Acetylon: Equity Ownership; Acetylon: Equity Ownership; Millennuim: Membership on an entity's Board of Directors or advisory committees; Millennuim: Membership on an entity's Board of Directors or advisory committees; C4 Therapeutics: Equity Ownership; C4 Therapeutics: Equity Ownership; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees.

Tunable regulation of CREB DNA binding activity couples genotoxic stress response and metabolism.

cAMP response element binding protein (CREB) is a key regulator of glucose metabolism and synaptic plasticity that is canonically regulated through recruitment of transcriptional coactivators. Here we show that phosphorylation of CREB on a conserved cluster of Ser residues (the ATM/CK cluster) by the DNA damage-activated protein kinase ataxia-telangiectasia-mutated (ATM) and casein kinase1 (CK1) and casein kinase2 (CK2) positively and negatively regulates CREB-mediated transcription in a signal dependent manner. In response to genotoxic stress, phosphorylation of the ATM/CK cluster inhibited CREB-mediated gene expression, DNA binding activity and chromatin occupancy proportional to the number of modified Ser residues. Paradoxically, substoichiometric, ATM-independent, phosphorylation of the ATM/CK cluster potentiated bursts in CREB-mediated transcription by promoting recruitment of the CREB coactivator, cAMP-regulated transcriptional coactivators (CRTC2). Livers from mice expressing a non-phosphorylatable CREB allele failed to attenuate gluconeogenic genes in response to DNA damage or fully activate the same genes in response to glucagon. We propose that phosphorylation-dependent regulation of DNA binding activity evolved as a tunable mechanism to control CREB transcriptional output and promote metabolic homeostasis in response to rapidly changing environmental conditions.

Martine delayed morphine tolerance associated with inhibited the expression of permeability-glycoprotein

Objective The matrine(Mat)on the development of morphine tolerance was investigated in rats. Methods Established morphine tolerance rat model treated with Mat and morphine using the tail-flick test to assesse the degree of tolerance. The expression of morphine-induced multidrug resistance (MDR)1 and Permeability-glycoprotein (P-gp) was tested by reverse transcriptase-polymerase chain reaction (RT-PCR)/Western blotting analysis. Further synthesized in vitro with cyclic adenosine monophosphate (cAMP) response element sequence, using electrophoretic mobility shift assay (EMSA) detection of MDR1 gene upstream start cyclic adenosine monophosphate response element binding protein (CREB) DNA binding activity changes. Results Morphine tolerance model is established after 7 days, Mat (300 mg/kg) inhibited the development of morphine tolerance which decreased (6.71±0.27) s, MPE%: 42.1%, areas under the curve (AUC) ratio: 1.93 and ED50 effective threshold: (4.15±0.54) mg/kg were all below the morphine group (P<0.05). MDR1 mRNA and P-gp expression was decreasedin Mat (300 mg/kg) with morphine group (P<0.05), but the difference between the samples of each has statistical significance. Mat doesn't affect CREB DNA binding activity. Conclusion These results suggest that Mat is likely not only can enhance morphine's analgesic effects, but also has analgesic effects itself, which the mechanism was related to the inhibition of MDR1 mRNA/P-gp expression. Key words: Matrine; Morphine tolerance; Permeability-glycoprotein; Multidrug resistance

Corticotropin Releasing Hormone and Urocortin 3 Stimulate Vascular Endothelial Growth Factor Expression through the cAMP/CREB Pathway

Colonic epithelium is the first line of defense against various pathological offenses in the gut. Previous studies have shown that the peptides of the corticotropin-releasing hormone (CRH) family modulate vascular endothelial growth factor (VEGF)-A production in other cells. Here we sought to investigate whether CRH and urocortin (Ucn) 3 regulate VEGF-A secretion in colonocytes through CRH receptors and to elucidate the underlying mechanism of action. CRH and Ucn 3 significantly increased the expression levels of VEGF-A mRNA and protein through CRH receptor 1 and 2, respectively, in human colonic epithelial cells and primary mouse intestinal epithelial cells. Underlying mechanisms involve activation of adenylyl cyclase with subsequent increase of intracellular cAMP level and increased DNA binding activity of transcription factor CREB on VEGF-A promoter region. Finally, genetic deficiency of CREB decreased intestinal inflammation and VEGF-A expression in a dextran sodium sulfate-induced colitis model. These results show that activation of CRH receptors by CRH ligands stimulates VEGF-A expression in intestinal epithelial cells through the cAMP/CREB pathway. Since VEGF-A boosts inflammatory responses through angiogenesis, these data suggest that CREB may be a key effector of CRH and Ucn 3-dependent inflammatory angiogenesis.

Bacterial flagellin induces IL-6 expression in human basophils

Binding of allergen to IgE on basophils positively affects allergic inflammation by releasing inflammatory mediators. Recently, basophils were shown to express pattern-recognition receptors, such as toll-like receptors (TLRs), for recognizing microbe-associated molecular patterns (MAMPs) that are independent of allergen-IgE binding. In this study, we investigated whether MAMP alone can induce IL-6 production in a human basophil cell line, KU812. Stimulation with flagellin in the absence of allergen-IgE association induced IL-6 expression in KU812 cells, while stimulation with lipoteichoic acid, peptidoglycan, or poly I:C did not under the same condition. Flagellin-induced IL-6 expression was also observed in human primary basophils. Flow cytometric analysis showed that KU812 cells expressed flagellin-recognizing TLR5 both on the cell surface and in the cytoplasm while TLR2 and TLR3 were observed only in the cytoplasm. We further demonstrated that although flagellin augmented the phosphorylation of mitogen-activated protein kinases including p38 kinase, ERK, and JNK, flagellin-induced IL-6 production was attenuated by inhibitors for p38 kinase and ERK, but not by JNK inhibitors. In addition, flagellin enhanced phosphorylation of signaling molecules including CREB, PKCδ, and AKT. The inhibitors for PKA and PKC also showed inhibitory effects. Interestingly, flagellin-induced IL-6 production was further enhanced by pretreatment with inhibitors for PI3K, implying that PI3K negatively affects the flagellin-induced IL-6 production. Furthermore, DNA binding activities of NF-κB, AP-1, and CREB, which play pivotal roles in the induction of IL-6 gene expression, were increased by flagellin. These results suggest that flagellin alone is sufficient to induce IL-6 gene expression via TLR5 signaling pathways in human basophils.

IL-13 Orchestrates Resolution of Chronic Intestinal Inflammation via Phosphorylation of Glycogen Synthase Kinase-3β

Spontaneous amelioration of inflammation (often accompanied by fibrosis) is a well-known, but poorly understood, outcome of many chronic inflammatory processes. We studied this phenomenon in a chronic trinitrobenzene sulfonic acid-induced colitis model, an experimental colitis in mice that we showed to ultimately undergo spontaneous resolution, despite continued trinitrobenzene sulfonic acid stimulation. Analysis of the mechanism of this resolution revealed that it was critically dependent on IL-13 activation of STAT6, followed by phosphorylation (inactivation) of glycogen synthase kinase-3β, at least in part via STAT6 induction of p38 MAPK. Such glycogen synthase kinase-3β inactivation causes changes in CREB and p65 DNA-binding activity that favors decreased proinflammatory IL-17 production and increased anti-inflammatory IL-10 production. Thus, in this case, IL-13 acts as a molecular switch that leads to resolution of inflammation.

Depression-Like Effect of Prenatal Buprenorphine Exposure in Rats

Studies indicate that perinatal opioid exposure produces a variety of short- and long-term neurobehavioral consequences. However, the precise modes of action are incompletely understood. Buprenorphine, a mixed agonist/antagonist at the opioid receptors, is currently being used in clinical trials for managing pregnant opioid addicts. This study provides evidence of depression-like consequence following prenatal exposure to supra-therapeutic dose of buprenorphine and sheds light on potential mechanisms of action in a rat model involving administration of intraperitoneal injection to pregnant Sprague-Dawley rats starting from gestation day 7 and lasting for 14 days. Results showed that pups at postnatal day 21 but not the dams had worse parameters of depression-like neurobehaviors using a forced swimming test and tail suspension test, independent of gender. Neurobehavioral changes were accompanied by elevation of oxidative stress, reduction of plasma levels of brain-derived neurotrophic factor (BDNF) and serotonin, and attenuation of tropomyosin-related kinase receptor type B (TrkB) phosphorylation, extracellular signal-regulated kinase (ERK) phosphorylation, protein kinase A activity, cAMP response element-binding protein (CREB) phosphorylation, and CREB DNA-binding activity. Since BDNF/serotonin and CREB signaling could orchestrate a positive feedback loop, our findings suggest that the induction of oxidative stress, reduction of BDNF and serotonin expression, and attenuation of CREB signaling induced by prenatal exposure to supra-therapeutic dose of buprenorphine provide evidence of potential mechanism for the development of depression-like neurobehavior.

E2F2 and CREB cooperatively regulate transcriptional activity of cell cycle genes

E2F2 is essential for the maintenance of T lymphocyte quiescence. To identify the full set of E2F2 target genes, and to gain further understanding of the role of E2F2 in transcriptional regulation, we have performed ChIP-chip analyses across the genome of lymph node–derived T lymphocytes. Here we show that during quiescence, E2F2 binds the promoters of a large number of genes involved in DNA metabolism and cell cycle regulation, concomitant with their transcriptional silencing. A comparison of ChIP-chip data with expression profiling data on resting E2f2−/− T lymphocytes identified a subset of 51 E2F2-specific target genes, most of which are upregulated on E2F2 loss. Luciferase reporter assays showed a retinoblastoma-independent role for E2F2 in the negative regulation of these target genes. Importantly, we show that the DNA binding activity of the transcription factor CREB contributes to E2F2-mediated repression of Mcm5 and Chk1 promoters. siRNA-mediated CREB knockdown, expression of a dominant negative KCREB mutant or disruption of CREB binding by mutating a CRE motif on Mcm5 promoter, relieved E2F2-mediated transcriptional repression. Taken together, our data uncover a new regulatory mechanism for E2F-mediated transcriptional control, whereby E2F2 and CREB cooperate in the transcriptional repression of a subset of E2F2 target genes.

Changes in CREB activation in the prefrontal cortex and hippocampus blunt ethanol-induced behavioral sensitization in adolescent mice

Drug dependence is a major health problem in adults and has been recognized as a significant problem in adolescents. We previously demonstrated that repeated treatment with a behaviorally sensitizing dose of ethanol in adult mice induced tolerance or no sensitization in adolescents and that repeated ethanol-treated adolescents expressed lower Fos and Egr-1 expression than adult mice in the prefrontal cortex (PFC). In the present work, we investigated the effects of acute and repeated ethanol administration on cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB) DNA-binding activity using the electrophoretic mobility shift assay (EMSA) and the phosphorylated CREB (pCREB)/CREB ratio using immunoblotting in both the PFC and hippocampus in adolescent and adult mice. Adult mice exhibited typical locomotor sensitization after 15 days of daily treatment with 2.0 g/kg ethanol, whereas adolescent mice did not exhibit sensitization. Overall, adolescent mice displayed lower CREB binding activity in the PFC compared with adult mice, whereas opposite effects were observed in the hippocampus. The present results indicate that ethanol exposure induces significant and differential neuroadaptive changes in CREB DNA-binding activity in the PFC and hippocampus in adolescent mice compared with adult mice. These differential molecular changes may contribute to the blunted ethanol-induced behavioral sensitization observed in adolescent mice.

MTOR modulates host immune responses to Francisella tularensis LVS infection (112.7)

Abstract Francisella tularensis (Ft) is the cause of tularemia, a disease with a high morbidity and mortality rate. The Ft live vaccine strain (LVS) has been used to study disease pathogenesis since infection of mice with LVS resembles tularemia in humans. It has been reported that Ft LVS is a TLR2 agonist and involves PI3K/Akt signaling. However, the involvement of mTOR, a downstream molecule of the PI3K/Akt pathway, has not been determined in Ft LVS infection, nor has the interplay between TLR2 and the mTOR cascade. In the present study, we provide evidence that mTOR exerts a differential regulation on both cytokine mRNA and secreted protein in murine peritoneal macrophages stimulated with Ft LVS. IL-6, IL-10 and IFN-β mRNA production increased with inhibition of the mTOR pathway, while levels of IFN-γ mRNA were independent of mTOR signaling. Secreted IL-6 and IFN-γ but not IFN-β and TNFα was dependent of mTOR regulation. Furthermore, mTOR signaling was critical for the DNA binding activity of CREB, but not of NF-κB p65. Upregulation of the interferon regulatory factors (IRF)-1, IRF-3 and IRF-5 in nuclear fractions of cell lysates was observed upon inhibition of mTOR, and correlated with increased levels of the pro-apoptotic proteins Bax, caspase 3 and caspase 8, indicating mTOR modulation of apoptosis via IRF downreguation. Overall, these studies identify mTOR as a critical regulator of the host immune response to Ft LVS infection.

Alternariol induces DNA polymerase β expression through the PKA-CREB signaling pathway

Alternariol (AOH) is a mycotoxin of Alternaria alternata and can cause DNA damage and gene mutations. Low-dose and long-term treatment with AOH has been linked with incidence of esophageal carcinoma. DNA polymerase β (polβ) is a key enzyme in DNA base excision repair (BER). When it is overexpressed or mutated in cells, DNA polβ can cause genetic instability. Elevated DNA polβ has also been reported in several human cancers. Here, we report that AOH at 2, 10, 20 µM induces DNA polβ expression. In the process, protein kinase A (PKA) catalytic subunit activation, nuclear translocation and cAMP response element binding protein (CREB) phosphorylation are involved. AOH also increased CREB binding to the cAMP response element (CRE) consensus motif, which is present in the DNA polβ gene promoter. The PKA inhibitor H89 was able to block AOH-induced PKA-CREB activation, CREB DNA binding activity and decrease DNA polβ expression. Our results suggest that AOH can upregulate DNA polβ expression through the PKA-CREB signal transduction pathway.