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Activity-dependent dendritic arborization mediated by CaM-kinase I activation and enhanced CREB-dependent transcription of Wnt-2.

Members of the Wnt signaling family are important mediators of numerous developmental events, including activity-dependent dendrite development, but the pathways regulating expression and secretion of Wnt in response to neuronal activity are poorly defined. Here, we identify an NMDA receptor-mediated, Ca2+-dependent signaling pathway that couples neuronal activity to dendritic arborization through enhanced Wnt synthesis and secretion. Activity-dependent dendritic outgrowth and branching in cultured hippocampal neurons and slices is mediated through activation by CaM-dependent protein kinase kinase (CaMKK) of the membrane-associated gamma isoform of CaMKI. Downstream effectors of CaMKI include the MAP-kinase pathway of Ras/MEK/ERK and the transcription factor CREB. A serial analysis of chromatin occupancy screen identified Wnt-2 as an activity-dependent CREB-responsive gene. Neuronal activity enhances CREB-dependent transcription of Wnt-2, and expression of Wnt-2 stimulates dendritic arborization. This novel signaling pathway contributes to dynamic remodeling of the dendritic architecture in response to neuronal activity during development.

Animals↗

Plasticity-specific phosphorylation of CaMKII, MAP-kinases and CREB during late-LTP in rat hippocampal slices in vitro.

Processes of learning, memory formation and functional plasticity, such as long-term potentiation (LTP) are associated with activity changes of alphaCaMKII, MAPKs and CREB proteins. Little is known on the temporal regulation of the phosphorylation states of these proteins during late-LTP, a period which requires the synthesis of new macromolecules and has been postulated to correlate with the consolidation of a memory trace at the cellular level. We now present data from hippocampal slices in vitro obtained from adult rats that describe such specific phosphorylation changes of the above mentioned three molecules during early- and late-LTP. We detail that LTP induction and its maintenance reveals a delayed onset of continuous CREB phosphorylation with two separate peaks at 45 min and 6 h before it decays back to baseline phosphorylation levels; whereas alphaCaMKII and MAPK2 remain in a specific, but enhanced phosphorylation state throughout the induction, early- and late-LTP. These LTP-regulated phosphorylation events were NMDAR-dependent and upon the activity of a translated serine-threonine kinase. Interestingly, only the late enhancement of pCREB was clearly dependent on protein synthesis. Our data extend results describing the regulation of alphaCaMKII, MAPKs and CREB phosphorylation during early stages of LTP, suggesting a specific role of these enzymes also during phases of LTP consolidation in adult animals.

2-Amino-5-phosphonovalerate↗

Cyclic AMP-dependent protein kinase A and CREB are involved in neuregulin-induced synapse-specific expression of acetylcholine receptor gene.

Neuregulin is reported to stimulate synapse-specific transcription of acetylcholine receptor (AChR) genes in the skeletal muscle fiber by multiple signaling pathways such as ERK, PI3K, and JNK. The co-localization of PKA mRNA with AChR and ErbBs, receptors for neuregulin, at the confined region of synapse implicates the putative role of PKA in neuregulin-induced AChR gene expression. In the present study, we found that mRNA and protein of a regulatory subunit of PKA (PKARIalpha) were concentrated at synaptic sites of the rat sternomastoid muscle fiber, while those of ERK and PI3K were uniformly distributed throughout the muscle fiber. Neuregulin (100 ng/ml) increased both PKA activity in the nucleus and AChRdelta subunit gene transcription in cultured Sol8 myotubes. These increases were significantly blocked by a specific PKA inhibitor H-89 (100 nM) and an adenylcyclase inhibitor SQ 22536 (200 microM) (72.5% and 60.1%, respectively). Furthermore, neuregulin phosphorylated CREB, a well-known down-stream transcription factor of PKA. While H-89 inhibited CREB phosphorylation, H-89 and PD098059 (50 microM), a specific MEK1/2 inhibitor, did not inhibit the phosphorylation of ERK and CREB, respectively, suggesting no cross-talk between PKA and ERK pathways. In conclusion, neuregulin increases AChRdelta subunit gene transcription, in part, by the activation of PKA/CREB, an alternative route to the previously reported ERK signaling pathway.

8-Bromo Cyclic Adenosine Monophosphate↗

Evidence from studies with N-ethyl-maleimide and 12-O-tetradecanoylphorbol-13-acetate that AP-1 and CREB are involved in the glucocorticoid activation of TRH gene expression in hypothalamic cultures.

To determine whether c-fos/c-jun (AP-1) and CREB mediate glucocorticoid stimulated TRH gene regulation, we investigated the effect of N-ethyl-maleimide (NEM), an alkylating agent, and 12-O-tetradecanoylphorbol-13-acetate (TPA) on this process. NEM decreased while TPA increased TRH levels in rat hypothalamic culture, changes similar to their effects on CREB and Fos/Jun proteins in the AtT20 cell line. This suggests that glucocorticoid stimulation of TRH gene expression may be regulated by the AP-1 complex and CREB pathway.

Animals↗

MSK1 is required for CREB phosphorylation in response to mitogens in mouse embryonic stem cells.

Mouse embryonic stem (ES) cells homozygous for disruption of the MSK1 gene had no detectable MSK1 activity. However, their activators (extracellular signal related kinase (ERK)1/ERK2) were stimulated normally in mitogen- and stress-activated protein kinase (MSK)1-/- and wild type cells in response to tetradecanoylphorbol acetate (TPA) and epidermal growth factor (EGF). TPA and EGF induced the phosphorylation of cyclic AMP-responsive element binding protein (CREB) at Ser-133 and ATF1 at Ser-63 in wild type cells and this was abolished by inhibition of the mitogen-activated protein kinase cascade. In contrast, the TPA- and EGF-induced phosphorylation of CREB/ATF1 was barely detectable in MSK1-/- cells. However, basal and forskolin-induced phosphorylation was similar, indicating that the MSK1 'knockout' did not prevent CREB phosphorylation by cyclic AMP-dependent protein kinase. Thus MSK1 is required for CREB and ATF1 phosphorylation after mitogenic stimulation of ES cells.

Acetyltransferases↗

CREB is cleaved by caspases during neural cell apoptosis.

Programmed cell death, or apoptosis, is a tightly regulated process mediated by selective cleavage of proteins by caspases, resulting in ordered destruction of the cell. In addition to structural proteins, proteins that mediate anti-apoptotic signal transduction are also substrates; their destruction eliminates potential futile attempts to escape execution. We asked whether cAMP response element binding protein (CREB), a transcription factor that mediates nerve growth factor (NGF) survival signals, is a target for caspases during apoptosis. CREB was specifically cleaved by caspases in neuroblastoma extracts, and in cells induced to undergo apoptosis by staurosporine. The destruction of CREB eliminates a key factor that could reverse apoptosis.

Adenosine Triphosphate↗

Cyclic AMP signalling and cellular proliferation: regulation of CREB and CREM.

In eukaryotes, transcriptional regulation upon stimulation of the adenylyl cyclase signalling pathway is mediated by a family of cAMP-responsive nuclear factors. This family consists of a large number of members which may act as activators or repressors. These factors contain the basic domain/leucine zipper motifs and bind as dimers to cAMP-response elements (CRE). The function of CRE-binding proteins (CREB) is modulated by phosphorylation by the cAMP-dependent protein kinase. The ICER (inducible cAMP early repressor) protein is the only inducible member of this family and is a product of the CREM gene. The induction of this powerful repressor is likely to be important for the transient nature of cAMP-induced gene expression. CREB proteins have been found to play an important role in the physiology of neuroendocrine functions. In addition, recent results indicate that CREB and CREM could be involved in the proliferation of hepatocytes which follows partial hepatectomy.

Cell Division↗

Expression of constitutively active CREB protein facilitates the late phase of long-term potentiation by enhancing synaptic capture.

Restricted and regulated expression in mice of VP16-CREB, a constitutively active form of CREB, in hippocampal CA1 neurons lowers the threshold for eliciting a persistent late phase of long-term potentiation (L-LTP) in the Schaffer collateral pathway. This L-LTP has unusual properties in that its induction is not dependent on transcription. Pharmacological and two-pathway experiments suggest a model in which VP16-CREB activates the transcription of CRE-driven genes and leads to a cell-wide distribution of proteins that prime the synapses for subsequent synapse-specific capture of L-LTP by a weak stimulus. Our analysis indicates that synaptic capture of CRE-driven gene products may be sufficient for consolidation of LTP and provides insight into the molecular mechanisms of synaptic tagging and synapse-specific potentiation.

Animals↗

Lithium and valproate differentially regulate brain regional expression of phosphorylated CREB and c-Fos.

Previous studies in our laboratory have shown that the mood stabilizers, lithium and valproate (VPA), regulate the transcription factors, cyclic AMP responsive element binding protein (CREB), c-Fos and c-Jun, differentially in cultured human neuroblastoma SH-SY5Y cells. Here, we confirm these findings in rat brain and further study the brain-regional effects of these drugs using immunohistochemistry. We found that although chronic treatment with LiCl or VPA did not change the expression of c-Fos and c-Jun, acute treatment with either drugs increased c-Fos expression but not c-Jun expression in CA1 and CA3 regions of hippocampus. Chronic treatment with LiCl, but not VPA, decreased CREB phosphorylation in rat cerebral cortex and hippocampus. These results suggest that lithium and VPA may act on different pathways to bring about their long-term prophylactic effects on bipolar disorder (BD). The regulation of CREB phosphorylation may be relevant to lithium effect. VPA, which is also effective in BD, may be linked to other pathways.

Animals↗

Gonadotropin-releasing hormone-induced stimulation of the rat secretogranin II promoter involves activation of CREB.

To investigate the events involved in regulation of the secretogranin II (SgII) gene, luciferase reporter constructs were transfected into gonadotrope-derived, alphaT3-1 cells. DNA between -91 and -60 relative to the transcription start site was found to be required for GnRH induced SgII reporter gene activation. This region contains a consensus cAMP response element (CRE) and disruption of this CRE reduced GnRH responsiveness of the SgII promoter. CREB was shown to bind to the SgII CRE and transfection studies with a dominant-negative CREB mutant provided evidence that CREB is required for GnRH responsiveness of the SgII promoter. An expression vector for an inhibitor of the cAMP-dependent protein kinase was found to reduce the ability of cAMP or GnRH to activate the SgII-luciferase reporter gene. These studies offer evidence that GnRH-induced activation of the SgII promoter in the alphaT3-1 cell line requires cAMP-dependent protein kinase activity and a functional CRE within the 5'-flanking region of the gene.

5' Flanking Region↗

Group I metabotropic glutamate receptors control phosphorylation of CREB, Elk-1 and ERK via a CaMKII-dependent pathway in rat striatum.

In vivo activation of group I metabotropic glutamate receptors (mGluRs) upregulates phosphorylation of cyclic AMP response element-binding protein (CREB), Elk-1 and extracellular signal-regulated kinases (ERK) in striatal neurons. To evaluate putative roles of Ca2+/calmodulin-dependent protein kinase II (CaMKII) in CREB, Elk-1 and ERK phosphorylation, the CaMKII inhibitor, KN62, was infused simultaneously with the group I mGluR agonist, 3,5-dihydroxyphenylglycine (DHPG), into the rat dorsal striatum. The results showed that DHPG (125, 250, and 500 nmol) increased phosphorylated (p) CaMKII immunoreactivity (IR) in a dose-dependent manner. KN62 (50 nmol) significantly attenuated 500 nmol DHPG-induced pERK, pElk-1 and pCREB IR in the ipsilateral dorsal striatum. These data indicate that pCaMKII is a possible upstream effector that is responsible for the regulation of CREB, Elk-1 and ERK phosphoproteins in response to group I mGluR stimulation in striatal neurons.

Animals↗

Increased phosphorylation of cyclic AMP response element-binding protein (CREB) in the superficial dorsal horn neurons following partial sciatic nerve ligation.

Partial sciatic nerve injury causes neuropathic pain associated with behavioral changes such as spontaneous pain, hyperalgesia and allodynia. Both central and peripheral sensitization of pain pathways are likely to be involved in these alterations. Nerve injury induced plastic changes in the dorsal horn, where the second relay nociceptive neurons are located, may contribute to the central sensitization process. It is thus important to establish the intracellular events through which a partial nerve injury can induce plasticity leading to neuropathic pain. In this study, we investigated whether partial sciatic nerve ligation (PSNL), a well-characterized neuropathic pain model, is able to induce the phosphorylation of a transcription factor, known as the cyclic AMP response element-binding protein (CREB) which is believed to be involved in the transcriptional regulation of many genes. Using immunocytochemistry, we found that 3 weeks following PSNL, the number of phosphorylated (p) CREB-IR cells was significantly increased in the injured side dorsal horn of rats, particularly in the superficial laminae. Interestingly, the majority of pCREB-IR cells expressed protein kinase Cgamma, an enzyme shown to be involved in the development of neuropathic pain in PSNL model. Taken together, these results suggest that increased CREB phosphorylation induced by PSNL may be one of the key molecular events leading to synaptic alterations and persistent pain in the PSNL model of neuropathic pain.

Animals↗

A late phase of cerebellar long-term depression requires activation of CaMKIV and CREB.

Recently, it has been shown that cerebellar LTD has a late phase that may be blocked by protein synthesis inhibitors. To understand the mechanisms underlying the late phase, we interfered with the activation of transcription factors that might couple synaptic activation to protein synthesis. Particle-mediated transfection of cultured Purkinje neurons with an expression vector encoding a dominant inhibitory form of CREB resulted in a nearly complete blockade of the late phase. Kinases that activate CREB were inhibited, and LTD was assessed. Inhibition of PKA or the MAPK/RSK cascades were without effect on the late phase, while constructs designed to interfere with CaMKIV function attenuated the late phase. These results indicate that the activation of CaMKIV and CREB are necessary to establish a late phase of cerebellar LTD.

Animals↗

CREB and the formation of long-term memory.

Cyclic AMP response element binding protein (CREB)-responsive transcription plays a central role in the formation of long-term memory in Drosophila, Aplysia and mice. Agents that disrupt the activity of CREB specifically block the formation of long-term memory, whereas agents that increase the amount or activity of the transcription factor accelerate the process. These results have led to the recent hypothesis that CREB is pivotal in the switch from short-term (protein synthesis independent) to long-term (protein synthesis dependent) memory.

Animals↗

In vivo CREB phosphorylation mediated by dopamine and NMDA receptor activation in mouse hippocampus and caudate nucleus.

The pattern of CREB phosphorylation was investigated in the caudate nucleus and hippocampus 10 min or 3 h after i.p. injection of dopamine or NMDA receptor agonists alone, or in combination with antagonists. Ten minutes after C57BL/6 J mice were injected with either the dopamine D1 receptor agonist SKF-38393 hydrobromide or NMDA, immunoreactivity of phosphorylated CREB (pCREB) was significantly increased in all parts of the caudate nucleus but not in hippocampal regions. However, 3 h after the injection of SKF-38393, pCREB levels in the caudate nucleus did not differ significantly from the pCREB levels in control animals, whereas pCREB levels were still elevated 3 h after NMDA injection. Except for the D1 receptor antagonist SCH-23390, which induced CREB phosphorylation in the caudate nucleus, dopamine and NMDA receptor antagonists had little effect on pCREB levels by themselves. However, the NMDA receptor antagonist CGS-19755 injected i.p. blocked both the NMDA- and SKF-38393-induced rise of pCREB levels in the caudate nucleus. Similarly, the D1 receptor antagonist SCH-23390 inhibited the effects produced by SKF-38393 or NMDA. Interestingly, the D2 receptor antagonist sulpiride also blocked the SKF-38393-triggered rise of pCREB. The results demonstrated that NMDA and dopamine receptors modulate pCREB levels in the caudate nucleus and suggest mutual permissive roles for both receptors.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

Hepatitis B virus X protein activates transcription by bypassing CREB phosphorylation, not by stabilizing bZIP-DNA complexes.

Although previous work has shown that the hepatitis B virus X protein (pX) stabilizes complexes between basic region leucine zipper (bZIP) proteins and target DNA, the relationship between enhanced binding and transcriptional activation has not been established. Here we show that interactions between CREB and pX, which coincidentally enhance DNA affinity, are necessary but not sufficient for increased transcriptional potency. Further, we show that transcriptional activation by pX requires a form of CREB in which Ser-133 is not phosphorylated. By stimulating the transcriptional potency of unphosphorylated CREB, pX can up-regulate the expression of cAMP-responsive genes implicated in hepatocyte proliferation, leading ultimately to the development of liver cancer after viral infection.

Activating Transcription Factor 2↗

Dynamic glycosylation of the transcription factor CREB: a potential role in gene regulation.

We report that CREB (cyclic AMP-responsive element-binding protein), a transcription factor essential for long-term memory, is O-GlcNAc glycosylated in the mammalian brain. Glycosylation occurs at two sites within the Q2 domain and disrupts the interaction between CREB and TAFII130, thereby repressing the transcriptional activity of CREB in vitro. These findings have important implications for the role of O-GlcNAc glycosylation in gene regulation, and they provide a link between O-GlcNAc and information storage processes in the brain.

Acetylglucosamine↗

Overexpression of a CREB repressor isoform enhances the female sexual receptivity in Drosophila.

The cAMP responsive transcriptional factor, CREB, is highly conserved among animal species, and its activity affects their behavior. In Drosophila melanogaster, one of alternatively spliced products of the CREB gene, dCREB2-a, is a transcriptional activator, while another isoform, dCREB2-b, is a repressor of dCREB2-a. Here, we demonstrate that overexpression of dCREB2-b in virgin females enhances their sexual receptivity. We studied the role of dCREB2 in female mating behavior using two transgenic lines, hs-dCREB2-a and hs-dCREB2-b, which overexpress respective products with heat-shock treatment. Wild-type males started their courtship behavior and mated more quickly with heat-shocked hs-dCREB2-b females than with non-heat-shocked hs-dCREB2-b females. Overexpression of dCREB2-a in females affected neither their courtship behavior nor mating frequency. The effects of overexpressed dCREB2-b were not due to elevated locomotor activities of heat-shocked females nor due to more vigorous courtship behavior of paired wild-type males. CREB might be involved in female sexual behavior of animals.

Animals↗