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PubMed2002

CREB DNA binding activation by a 50-Hz magnetic field in HL60 cells is dependent on extra- and intracellular Ca(2+) but not PKA, PKC, ERK, or p38 MAPK.

To investigate the possible mechanism of gene transcription changes induced by magnetic field (MF), we examined the DNA binding behavior of the transcription factor cyclic-AMP responsive element binding protein (CREB) in HL60 cells after exposure to a 0.1mT 50-Hz extremely low frequency (ELF) sinusoidal MF by a gel shift assay. Magnetic field induced a time-dependent activation of CREB binding. The complex formation increased shortly after MF exposure for 10min, reaching a peak level after 1h, and then recovered to basal level at 4h after exposure. A novel MF-induced ATF2/ATF2 homodimer formation was observed after MF exposure for 30min, 1, and 2h. Furthermore, We found that the MF-induced increase of CREB DNA binding in HL60 cells was dependent on both extracellular and intracellular Ca(2+) but not PKA, PKC, ERK, or p38 MAPK by using various pathway inhibitors. These data indicate that MF exposure activates CREB DNA binding through calcium-related signal transduction pathways under our experimental conditions.

Calcium↗
PubMed2000

DARPP-32 and CREB are present in type 2 iodothyronine deiodinase-producing tanycytes: implications for the regulation of type 2 deiodinase activity.

Type 2 iodothyronine deiodinase, an enzyme involved in the conversion of thyroxin to the biologically active 3,5, 3'-triiodothyronine, is highly concentrated in a group of specialized ependymal cells, tanycytes, lining the wall and floor of the third ventricle. As this distribution is highly reminiscent of the distribution of cells containing the phosphatase inhibitor, DARPP-32, we raised the possibility that these two proteins may coexist in tanycytes and that DARPP-32 may modulate type 2 deiodinase activity by regulating the phosphorylation state of the cAMP regulatory factor, CREB. To address this question, double-labeling histochemical studies were performed for type 2 deiodinase mRNA and DARPP-32 immunoreactivity (IR), or DARPP-32- and CREB-IR in the same tissue sections. Type 2 deiodinase mRNA was found in the cell bodies of all DARPP-32-immunolabeled tanycytes. Both type 2 deiodinase mRNA and DARPP-32-IR also extended into tanycyte processes that ramified in the arcuate nucleus and median eminence, in close association with blood vessels and portal capillaries. In contrast, type 2 deiodinase mRNA was not present in the same cells that contained DARPP-32-IR in the pituitary gland. All tanycytes containing DARPP-32-IR also contained CREB-IR in their nucleus. Since type 2 deiodinase activity can be induced by substances that increase cAMP, we hypothesize that DARPP-32 may regulate the activity of type 2 deiodinase by prolonging the activation of CREB. Selectivity for the colocalization of these factors to tanycytes but not the pituitary gland, may explain the heterogeneous response of type 2 deiodinase activity in these two loci in response to specific stimuli such as fasting.

Animals↗
PubMed2000

CREB contributes to the increased neurite outgrowth of sensory neurons induced by vasoactive intestinal polypeptide and activity-dependent neurotrophic factor.

Our recent experiments suggest that vasoactive intestinal polypeptide (VIP) enhances neurite outgrowth of dissociated rat dorsal root ganglion cells, indirectly, via the release of a trophic factor from the spinal cord. In this study, we have examined the possible contribution of activity-dependent neurotrophic factor (ADNF) to the trophic actions of VIP. In addition, as we have shown that the factor mediating the trophic actions of VIP acts via protein kinase A we have also examined the contribution of CREB, which is a transcription factor activated by protein kinase A. As previously shown, supernatant taken from spinal cord incubated with VIP, significantly increased the percentage of sensory neurons with neurites. Antiserum against ADNF attenuated the trophic effect of the VIP-conditioned supernatant. Consistently, the ADNF agonist, ADNF(14) (0.001-0.1 fM), significantly enhanced the percentage of cells with neurite outgrowth. Furthermore, the trophic action of ADNF(14) was attenuated by a protein kinase A inhibitor, Rp-cAMPS, whereas the inactive isomer, Sp-cAMPS, had no effect. Preincubation of cells with 5 mcM CREB antisense oligonucleotides, attenuated the increase in neurite outgrowth induced by either the supernatant or ADNF(14). The sense oligonucleotide had no influence on the enhanced neurite outgrowth. We also found that both the supernatant and ADNF(14) induced an increase in the percentage of cells expressing phosphorylated CREB. The data suggests that VIP induces a release of neurotrophic factors, such as ADNF, which enhance neurite outgrowth. In addition, protein kinase A and CREB appear to contribute to the neurotrophic actions of VIP and ADNF. The mechanisms underlying the neurotrophic action of VIP, may have important implications for sprouting and/or synaptic reorganization of central terminals of sensory neurons, which may contribute to neuropathic pain that commonly occurs following peripheral nerve damage.

Animals↗
PubMed2001

Stress-induced sensitization of CRH-ir but not P-CREB-ir responsivity in the rat central nervous system.

There is some evidence that a traumatic life event can induce long-term alterations in corticotropin-releasing hormone (CRH) producing neurons in humans, which may play a role in the pathophysiology of anxiety disorders, including post-traumatic stress disorder (PTSD). To study the long-term effects of a traumatic event on brain CRH-immunoreactivity (CRH-ir) and phospho-cAMP response element binding protein-immunoreactivity (P-CREB-ir), rats were exposed to a single session of foot shocks (preshocked) or no shocks (control). Two weeks later half of the control rats and half of the preshocked rats received an electrified prod in the home cage for 15 min and behavior was recorded. Fifteen minutes after the removal of the prod rats were perfused and brain sections were stained for CRH-ir and P-CREB-ir. There was no basal difference between preshocked and control rats in brain CRH-ir and P-CREB-ir. Exposure to the electrified prod induced a significant increase in CRH-ir in the paraventricular nucleus of the hypothalamus, the median eminence and the central amygdala in preshocked rats, but not in control rats. The electrified prod increased the number of P-CREB-ir neurons in the paraventricular nucleus of the hypothalamus and the locus coeruleus, but the preshock experience did not affect this response. In an additional experiment with a similar design plasma hormone levels were measured 14 days after the foot shocks. The preshock experience sensitized the shock prod-induced ACTH and corticosterone response. No behavioral differences between preshocked and control rats were found during the shock prod tests. We suggest that long-term stress-induced changes in neuropeptide dynamics of CRH-ir neurons may play a role in long-term stress-induced neuroendocrine sensitization.

Adrenocorticotropic Hormone↗
PubMed2003

The role of maternal CREB in early embryogenesis of Xenopus laevis.

In Xenopus embryos, body patterning and cell specification are initiated by transcription factors, which are themselves transcribed during oogenesis, and their mRNAs are stored for use after fertilization. We have previously shown that the T-box transcription factor VegT is both necessary and sufficient to initiate transcription of all endoderm, and most mesoderm genes. In the absence of maternal VegT, no mesodermal organs (including the heart) or endodermal organs form. A second maternal transcription factor XTcf3 acts as a global repressor of transcription of dorsal genes, whose repression is inactivated on the dorsal side by a maternally encoded Wnt signaling pathway. In the absence of beta-catenin, no mesodermal or endodermal organs form. We show here that the maternally encoded transcription factor CREB is also essential for development. It is required for the initiation of expression of several mesodermal genes, including Xbra, Xcad2, and -3 and also regulates the cardiogenic gene Nkx 2-5. We show that maternal CREB-depleted embryos develop gastrulation defects that are rescued by the reintroduction of activated CREB mRNA. We conclude that maternal CREB must be added to the list of essential maternal transcription factors regulating cell specification in the early embryo.

Amino Acid Sequence↗
PubMed1999

Lysophosphatidylcholine phosphorylates CREB and activates the jun2TRE site of c-jun promoter in vascular endothelial cells.

Lysophosphatidylcholine (lyso-PC), a polar phospholipid increased in atherogenic lipoproteins and atherosclerotic lesions, has been shown to induce transcription of a variety of endothelial genes relevant to atherogenesis. Lyso-PC has been shown to activate c-jun N-terminal kinase (JNK) and activator protein 1 (AP-1) and thereby stimulate transcription of the c-jun gene. Here we provide evidence that lyso-PC can phosphorylate cyclic AMP responsive element binding protein (CREB) and thereby activate the jun2 12-O-tetradecanoylphorbol 13-acetate response element (jun2TRE) site of the c-jun promoter, which appears to be the major molecular mechanism involved in lyso-PC-induced c-jun gene expression in cultured bovine aortic endothelial cells (BAEC). Transient transfection of BAEC with a 1.6-kbp c-jun promoter and luciferase reporter fusion gene resulted in a 12.9-fold increase in luciferase activity by lyso-PC treatment. Serial deletion mutation in c-jun promoter and luciferase reporter gene assay revealed that the 5' promoter region between nucleotide numbers -268 and -127, which contains a jun2TRE binding sequence, was most crucial for lyso-PC-induced transcription. The 5' promoter region between -76 and -27, which contains an AP-1 site, also affected lyso-PC-induced transcription of the c-jun gene. Point mutation in the jun2TRE site reduced lyso-PC-induced transcription of the c-jun promoter-luciferase fusion gene by a 70.3% decrease in c-jun promoter activity. Electrophoretic mobility shift assays showed increased binding of (32)P-labeled oligonucleotides with jun2TRE in nuclear extracts isolated from lyso-PC-treated BAEC, which was abolished or supershifted by anti-CREB antibody. Immunoblotting with anti-phosphorylated CREB antibody showed rapid phosphorylation of this protein after lyso-PC treatment. These results indicate that lyso-PC phosphorylates CREB, which was then bound to the jun2TRE site of the c-jun promoter and activated transcription. Activation of jun2TRE may play a key role in the transcriptional activation of c-jun as well as other endothelial genes depending upon these transcription factors.

Animals↗
PubMed1996

Angiotensin II induction of fibronectin biosynthesis in cultured human mesangial cells: association with CREB transcription factor activation.

We assessed the effect of angiotensin II on fibronectin biosynthesis a nd transcription factor activation in adult human mesangial cells in culture. We found that 10(-5) mol/L angiotensin II tended to increase fibronectin mRNA expression within 1 hour (1.2-fold +/- 0.3-fold of that in controls), with a significant increase after 4 hours (0.3-fold +/- 0.1-fold of that in controls, p < 0.05) and 24 hours (1.9-fold +/- 0.3-fold of that in controls, p < 0.02). In conjunction with increased fibronectin mRNA levels, angiotensin II exposure resulted in a significant elevation in immunoreactive fibronectin concentrations and the incorporation of (35S)-labeled methionine into fibronectin after 2 hours (224% +/- 23% of controls, p < 0.05). Angiotensin II also induced mesangial cell activation of the cyclic adenosine monophosphate response element binding protein (CREB) transcription factor, a DNA binding protein known to recognize specific regulatory elements present on the fibronectin gene promoter. Using the electrophoretic mobility shift assay, we showed that angiotensin II increased mesangial cell expression of the activated form of CREB after 4 hours (1.2-fold +/- 0.04-fold of that in controls, p < 0.05). To determine the importance of the CREB regulatory elements in mediating angiotensin II induction of fibronectin gene transcription, JEG-3 cells were transfected with plasmids containing fibronectin promoter-chloramphenicol acetyltransferase (CAT) reporter gene constructs with (FN510) or without (FN122) the CREB regulatory motifs. Angiotensin II resulted in a significant increase in CAT activity in FN510 transfectants (1.6-fold +/- 0.2-fold of that in controls, p < 0.05), but there was no effect of angiotensin II on FN122 transfected cells. These data demonstrate that angiotensin II stimulates fibronectin biosynthesis in adult human mesangial cells and suggest that the process may be regulated at the transcriptional level.

Angiotensin II↗
PubMed2003

2,2',4,6,6'-pentachlorobiphenyl (PCB 104) induces apoptosis of human microvascular endothelial cells through the caspase-dependent activation of CREB.

It has been proposed that endothelial integrity can play an active regulatory role in the extravasation of tumor cells during cancer metastasis. Since polychlorinated biphenyls (PCBs) have been shown to cause endothelial cell activation or injury and to lead to various diseases that involve dysfunction of the vascular endothelium, the present study was designed to determine the cellular and molecular signaling mechanisms of PCB-induced apoptosis in human microvascular endothelial cells (HMEC-1). A significant and marked decrease in cell viability was observed in HMEC-1 treated with 2,2',4,6,6'-pentachlorobiphenyl (PCB 104) in a time- and dose-dependent manner. Exposure of HMEC-1 to PCB 104 also dramatically induced internucleosomal DNA fragmentation. However, the caspase inhibitor zVAD-fmk significantly reversed the PCB 104-induced DNA fragmentation in HMEC-1, suggesting that endothelial cell death induced by PCB 104 exposure is, at least in part, due to caspase-dependent apoptotic pathways. To elucidate the molecular signaling mechanisms of PCB 104-induced apoptotic cell death in human microvascular endothelial cells, the present study focused on the effects of acute exposure of PCB 104 on the activation of several transcription factors, such as cAMP responsive element-binding protein (CREB), activator protein-1 (AP-1), nuclear factor-kappaB (NF-kappaB), and signal transducers and activators of transcription (STAT1), which have been known to play a pivotal role in the molecular signaling cascades for the induction of apoptosis. A series of electrophoretic mobility shift assay showed that PCB 104 specifically increased only CREB DNA-binding activity in a dose-dependent manner. AP-1, NF-kappaB, and STAT1, however, were not activated. In addition, zVAD-fmk significantly and dose-dependently blocked the CREB activation enhanced by PCB 104 exposure. These results suggest that PCB-induced death of human microvascular endothelial cells is mediated, at least in part, via the caspase-dependent apoptotic pathways and that the selective activation of CREB is involved in this process.

Apoptosis↗
PubMed2002

CREB phosphorylation as a molecular marker of memory processing in the hippocampus for spatial learning.

Regulation of gene transcription via the cyclic adenosine 3',5'-monophosphate (cAMP)-mediated second messenger pathway has been implicated in learning and memory. Although the cAMP response element-binding protein (CREB) is an important transcription factor involved in long-term memory, it remains to be determined whether the CREB-dependent events are attributed to spatial learning and memory in a radial arm maze. Here we demonstrate that cAMP-dependent protein kinase A (PKA) and CREB are activated in the course of spatial learning. The radial maze training in rats resulted in a significant increase in PKA and CREB phosphorylation in the hippocampus in the course of spatial learning, which was followed by spatial memory formation. On the other hand, neither the phosphorylation of Ca2+/calmodulin-dependent protein kinase II (CaMKII) and extracellular signal-regulated kinase (ERK) nor the mRNA level of brain-derived neurotrophic factor was significantly affected. These results suggest that activation of the PKA/CREB signaling pathway in the hippocampus plays an important role in spatial memory formation.

Animals↗
PubMed2001

Differentiation of bipolar CG-4 line oligodendrocytes is associated with regulation of CREB, MAP kinase and PKC signalling pathways.

Undifferentiated bipolar CG-4 cell line oligodendrocytes provide a model system for the O-2A progenitor cell from which oligodendrocytes are derived both in vivo and in vitro. The exchange of neuroblastoma conditioned basal media for basal media causes differentiation of undifferentiated bipolar CG-4 cells into multipolar oligodendrocyte-like cells whilst replacement with basal media containing 20% foetal bovine serum favours the formation of type-2 astrocyte-like cells. Here, we demonstrate that activation of these differentiation pathways correlates with distinct changes both in cell metabolism and in signal transduction. Exchange of neuroblastoma conditioned media for basal media correlates with stimulation of basal metabolic activity, reduced phosphorylation of p44/42 MAP kinase and reduced phosphorylation of the transcription factor CREB. In contrast, differentiation with basal medium containing 20% foetal bovine serum (FBS), into type 2 astrocyte-like cells, correlates with reduction in basal metabolic activity, increased phosphorylation of p44/42 MAP kinase and increased phosphorylation of the transcription factor CREB. Inhibition of protein kinase C blocked both the metabolic and morphological changes associated with differentiation towards mature multipolar oligodendrocyte-like cells. Inhibition of PKA and MEK did not effect metabolic activity. The rapid return of neuroblastoma conditioned basal media to cells treated with basal media, increased phosphorylation of CREB and MAP kinase. These results demonstrate that protein kinase C and p44/42 MAP kinase signalling pathways are modulated during bipolar CG-4 cell differentiation and demonstrate that the transcription factor CREB may play a pivotal role in differentiation along oligodendrocyte-or astrocyte-lineages.

Alkaloids↗
PubMedDate not supplied

Oxidative stress differentially modulates phosphorylation of ERK, p38 and CREB induced by NGF or EGF in PC12 cells.

This study assessed if oxidative stress induced by treatment of PC12 cells with H2O2 modulated signaling cascades induced by nerve growth factor (NGF) or epidermal growth factor (EGF) because oxidative stress and impaired growth factor function are associated with aging and aging-associated diseases such as Alzheimer's disease. Phosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK 1/2) and of p38 kinase was rapidly increased after treatment with NGF, EGF, or H2O2, with NGF causing more prolonged increases than the other agents. Pretreatment with H2O2 did not alter phosphorylation of ERK1/2 induced by either growth factor, but increased the phosphorylation of p38 kinase induced by treatment with NGF or EGF alone. CREB phosphorylation at SER 133 was rapidly increased by treatment with either NGF or EGF. Pretreatment with H2O2 reduced CREB phosphorylation induced by either growth factor. This seemed to be a direct effect because H2O2 also inhibited CREB phosphorylation induced by the adenylyl cyclase stimulator forskolin. These results demonstrate that oxidative stress can differentially modulate growth factor-initiated signaling cascades. Furthermore, because CREB is an evolutionarily preserved protein involved in the formation of long term memory, these results indicate a new target of oxidative stress that may be important in disorders involving impaired memory, such as Alzheimer's disease.

Alzheimer Disease↗
PubMed2001

Reversal by NS-7, a neuroprotective compound, of the decrease in transcription factor CREB mRNA expression in rat brain after permanent middle cerebral artery occlusion.

The effect of a neuroprotective agent NS-7 on changes in mRNA expressions for cyclic AMP responsive element binding protein (CREB) and several neurotrophins was examined in the rat cerebral cortex after permanent middle cerebral artery occlusion (MCAO). Significant reduction in mRNA expressions for CREB was observed at 24h after MCAO. NS-7 (0.5mg/kg), when injected at 6h after MCAO, significantly reversed the decreased expression for CREB mRNA. In addition, the mRNA expression for basic fibroblast growth factor (bFGF) was also significantly enhanced by NS-7 in MCA-occluded but not in sham-operated rats. On the other hand, the mRNAs for interluekin-6 and inducible-type nitric oxide synthase were markedly induced in the cerebral cortex of MCA-occluded rats, which was not significantly reversed by NS-7. Therefore, it is suggested that the reversal of decrease in CREB mRNA and concomitant increase in mRNA expression for bFGF may contribute to the neuroprotective action of NS-7.

Animals↗
PubMed2001

BDNF synthesis in spiral ganglion neurons is constitutive and CREB-dependent.

Brain-derived neurotrophic factor (BDNF), which supports spiral ganglion neuron (SGN) survival in vivo and in vitro, is synthesized by SGNs. The BDNF gene generates multiple different transcripts, each from its own promoter region. Using reverse transcriptase-polymerase chain reaction (RT-PCR), we find that SGNs express only the downstream transcripts III and IV in vivo and in vitro. Using RT-PCR assays of BDNF transcripts and transfection of BDNF promoter-reporter constructs, we tested the hypothesis, originally derived from studies of cortical neurons, that depolarization induces BDNF expression via a signaling pathway that includes Ca2+/calmodulin-dependent kinases (CaMKs) and the transcription factor, Ca2+/cyclic AMP response element binding protein (CREB). In contrast, we found that in SGNs in vivo BDNF expression is constitutive and is not increased by electrical activation. Similarly, BDNF expression in vitro is not increased by stimuli that activate CREB, including depolarization, cAMP, or transfection of activated CaMK mutants. However, transfection of dominant-negative CREB mutants did abrogate gene expression driven by BDNF promoters III and IV, indicating that CREB is necessary for constitutive BDNF expression. Thus, BDNF synthesis within SGNs makes possible an autocrine or paracrine mechanism that can contribute to support SGN survival but SGNs are distinctive in that this mechanism is constitutive and not activity-regulated.

Animals↗
PubMed1997

CREB: a major mediator of neuronal neurotrophin responses.

Neurotrophins regulate neuronal survival, differentiation, and synaptic function. To understand how neurotrophins elicit such diverse responses, we elucidated signaling pathways by which brain-derived neurotrophic factor (BDNF) activates gene expression in cultured neurons and hippocampal slices. We found, unexpectedly, that the transcription factor cyclic AMP response element-binding protein (CREB) is an important regulator of BDNF-induced gene expression. Exposure of neurons to BDNF stimulates CREB phosphorylation and activation via at least two signaling pathways: by a calcium/calmodulin-dependent kinase IV (CaMKIV)-regulated pathway that is activated by the release of intracellular calcium and by a Ras-dependent pathway. These findings reveal a previously unrecognized, CaMK-dependent mechanism by which neurotrophins activate CREB and suggest that CREB plays a central role in mediating neurotrophin responses in neurons.

Animals↗
PubMed1998

Cross talk between ERK and PKA is required for Ca2+ stimulation of CREB-dependent transcription and ERK nuclear translocation.

Although Ca2+-stimulated cAMP response element binding protein- (CREB-) dependent transcription has been implicated in growth, differentiation, and neuroplasticity, mechanisms for Ca2+-activated transcription have not been defined. Here, we report that extracellular signal-related protein kinase (ERK) signaling is obligatory for Ca2+-stimulated transcription in PC12 cells and hippocampal neurons. The sequential activation of ERK and Rsk2 by Ca2+ leads to the phosphorylation and transactivation of CREB. Interestingly, the Ca2+-induced nuclear translocation of ERK and Rsk2 to the nucleus requires protein kinase A (PKA) activation. This may explain why PKA activity is required for Ca2+-stimulated CREB-dependent transcription. Furthermore, the full expression of the late phase of long-term potentiation (L-LTP) and L-LTP-associated CRE-mediated transcription requires ERK activation, suggesting that the activation of CREB by ERK plays a critical role in the formation of long lasting neuronal plasticity.

Animals↗
PubMed2001

Voltage-gated channels block nicotinic regulation of CREB phosphorylation and gene expression in neurons.

Synaptic activation of the transcription factor CREB and downstream gene expression usually depend on calcium influx aided by voltage-gated calcium channels. We find that nicotinic signaling, in contrast, activates CREB and gene expression in ciliary ganglion neurons both in culture and in situ only if voltage-gated channels are silent. The nicotinic response requires calcium influx and release from internal stores and acts through CaMK and MAPK pathways to sustain activated CREB. Voltage-gated channels mobilize CaMK to activate CREB initially, but they also enable calcineurin and PP1 to terminate the activation before transcription is affected. L-type voltage-gated channels dominate the outcome and block the effects of nicotinic signaling on transcription. This demonstrates a novel aspect of activity-dependent gene regulation.

Animals↗
PubMed2002

Function and regulation of CREB family transcription factors in the nervous system.

CREB and its close relatives are now widely accepted as prototypical stimulus-inducible transcription factors. In many cell types, these factors function as effector molecules that bring about cellular changes in response to discrete sets of instructions. In neurons, a wide range of extracellular stimuli are capable of activating CREB family members, and CREB-dependent gene expression has been implicated in complex and diverse processes ranging from development to plasticity to disease. In this review, we focus on the current level of understanding of where, when, and how CREB family members function in the nervous system.

Animals↗
PubMed2001

Modulation of CREB and NF-kappaB signal transduction by cannabinol in activated thymocytes.

Cannabinoid compounds inhibit the cAMP signalling cascade in leukocytes. One of these compounds, cannabinol (CBN) has been shown to inhibit interleukin-2 (IL-2) expression and the activation of cAMP response element binding protein (CREB) and nuclear factor for immunoglobulin kappa chain in B cells (NF-kappaB) following phorbol-12-myristate-13 acetate (PMA) plus ionomycin (Io) treatment of thymocytes. Therefore, the objective of the present studies was to determine the role of cAMP and protein kinase A (PKA) in the CBN-mediated inhibition of IL-2, CREB, and NF-kappaB in PMA/Io-activated thymocytes. The inhibition of CREB/ATF-1 phosphorylation, or cAMP response element (CRE) or kappaB DNA binding activity produced by CBN in PMA/Io-activated thymocytes, could not be reversed by DBcAMP costimulation. Furthermore, DBcAMP failed to reverse the concentration-dependent inhibition of IL-2 protein secretion by CBN. Pretreatment of thymocytes with H89 produced a modest inhibition of PMA/Io-induced CREB/ATF-1 phosphorylation and CRE DNA binding activity but H89 had no effect on protein binding to a kappaB motif. Additionally, H89 modestly inhibited PMA/Io-induced IL-2 secretion. In light of the modest involvement of the cAMP pathway in CBN-mediated inhibition of CREB and IL-2 in PMA/Io-activated thymocytes, PD098059 (PD), the MEK inhibitor, was utilized to determine the role of ERK MAP kinases in thymocytes. ERKs play a critical role in IL-2 production but not for CREB phsophorylation. Collectively, these findings suggest that CBN may modulate several signalling pathways in activated T cells.

Animals↗