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Thomas C Tubon,
Jiabin Zhang,
Eugenia L Friedman,
Haining Jin,
Erin D Gonzales,
Hong Zhou,
Diana Drier,
Jason R Gerstner,
Emily A Paulson,
Robin Fropf, Jerry C P Yin
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ABSTRACT: CREB-responsive transcription has an important role in adaptive responses in all cells and tissue. In the nervous system, it has an essential and well established role in long-term memory formation throughout a diverse set of organisms. Activation of this transcription factor correlates with long-term memory formation and disruption of its activity interferes with this process. Most convincingly, augmenting CREB activity in a number of different systems enhances memory formation. In Drosophila, a sequence rearrangement in the original transgene used to enhance memory formation has been a source of confusion. This rearrangement prematurely terminates translation of the full-length protein, leaving the identity of the "enhancing molecule" unclear. In this report, we show that a naturally occurring, downstream, in-frame initiation codon is used to make a dCREB2 protein off of both transgenic and chromosomal substrates. This protein is a transcriptional activator and is responsible for memory enhancement. A number of parameters can affect enhancement, including the short-lived activity of the activator protein, and the time-of-day when induction and behavioral training occur. Our results reaffirm that overexpression of a dCREB2 activator can enhance memory formation and illustrate the complexity of this behavioral enhancement.
Journal of Neuroscience 04/2013; 33(17):7475-87. · 7.11 Impact Factor
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ABSTRACT: cAMP response element-binding protein (CREB) and nuclear factor kappa-B (NF-κB) are two ubiquitous transcription factors involved in a wide number of cellular processes, including the circadian system. Many previous studies on these factors use cellular assays that provide limited information on circadian activity or anatomical specificity. The ability to study transcription factors in defined tissue within intact animals will help to bridge the gap between cellular and in vivo data. We have used the GAL4-UAS and FLP-FRT systems to gain spatial control over reporter gene expression. Using a luciferase-based reporter, we show in vivo that Drosophila dCREB2- and NF-κB-mediated transcription oscillates in neuronal cells, glia, and in the mushroom body, a higher-order brain center in flies. This oscillation is under circadian control, cycling with a 24-hour rhythm, under both light-dark and dark-dark conditions. In light-light conditions, dCREB2 and NF-κB reporter flies exhibit a suppression of rhythmic activity. Furthermore, neuronal cycling of dCREB2 and NF-κB activity are modulated in period mutant flies, indicating these oscillations are controlled through the central clock. This study shows for the first time region-specific circadian oscillation of dCREB2/NF-κB activity in the Drosophila nervous system.
PLoS ONE 01/2012; 7(10):e45130. · 4.09 Impact Factor
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ABSTRACT: Research in Drosophila has many advantages for the study of complex behavior. Two studies identify a new role for chemical and electrical signaling in the anterior paired lateral neurons during memory formation.
Current biology: CB 05/2011; 21(10):R394-5. · 10.99 Impact Factor
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ABSTRACT: Sleep is thought to be important for memory consolidation, since sleep deprivation has been shown to interfere with memory processing. However, the effects of augmenting sleep on memory formation are not well known, and testing the role of sleep in memory enhancement has been limited to pharmacological and behavioral approaches. Here we test the effect of overexpressing the brain-type fatty acid binding protein (Fabp7) on sleep and long-term memory (LTM) formation in Drosophila melanogaster. Transgenic flies carrying the murine Fabp7 or the Drosophila homologue dFabp had reduced baseline sleep but normal LTM, while Fabp induction produced increases in both net sleep and LTM. We also define a post-training consolidation "window" that is sufficient for the observed Fabp-mediated memory enhancement. Since Fabp overexpression increases consolidated daytime sleep bouts, these data support a role for longer naps in improving memory and provide a novel role for lipid-binding proteins in regulating memory consolidation concurrently with changes in behavioral state.
PLoS ONE 01/2011; 6(1):e15890. · 4.09 Impact Factor
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ABSTRACT: There has been considerable progress in elucidating the molecular mechanisms that contribute to memory formation and the generation of circadian rhythms. However, it is not well understood how these two processes interact to generate long-term memory. Recent studies in both vertebrate and invertebrate models have shown time-of-day effects on neurophysiology and memory formation, and have revealed a possible role for cycling molecules in memory persistence. Together, these studies suggest that common mechanisms underlie circadian rhythmicity and long-term memory formation.
Nature Reviews Neuroscience 08/2010; 11(8):577-88. · 26.48 Impact Factor
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ABSTRACT: Pharmacodynamic tolerance is believed to involve homeostatic mechanisms initiated to restore normal neural function. Drosophila exposed to a sedating dose of an organic solvent, such as benzyl alcohol or ethanol, acquire tolerance to subsequent sedation by that solvent. The slo gene encodes BK-type Ca(2+)-activated K(+) channels and has been linked to alcohol- and organic solvent-induced behavioral tolerance in mice, Caenorhabditis elegans (C. elegans) and Drosophila. The cyclic AMP response element-binding (CREB) proteins are transcription factors that have been mechanistically linked to some behavioral changes associated with drug addiction. Here, we show that benzyl alcohol sedation alters expression of both dCREB-A and dCREB2-b genes to increase production of positively acting CREB isoforms and to reduce expression of negatively acting CREB variants. Using a CREB-responsive reporter gene, we show that benzyl alcohol sedation increases CREB-mediated transcription. Chromatin immunoprecipitation assays show that the binding of dCREB2, with a phosphorylated kinase-inducible domain, increases immediately after benzyl alcohol sedation within the slo promoter region. Most importantly, we show that a loss-of-function allele of dCREB2 eliminates drug-induced upregulation of slo expression and the production of benzyl alcohol tolerance. This unambiguously links dCREB2 transcription factors to these two benzyl alcohol-induced phenotypes. These findings suggest that CREB positively regulates the expression of slo-encoded BK-type Ca(2+)-activated K(+) channels and that this gives rise to behavioral tolerance to benzyl alcohol sedation.
Genes Brain and Behavior 03/2009; 8(4):369-76. · 3.48 Impact Factor
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ABSTRACT: Cyclic AMP (cAMP) is a second messenger involved in many processes including mnemonic processing and anxiety. Memory deficits and anxiety are noted in the phenotype of fragile X (FX), the most common heritable cause of mental retardation and autism. Here we review reported observations of altered cAMP cascade function in FX and autism. Cyclic AMP is a potentially useful biochemical marker to distinguish autism comorbid with FX from autism per se and the cAMP cascade may be a viable therapeutic target for both FX and autism.
Neuroscience & Biobehavioral Reviews 07/2008; 32(8):1533-43. · 8.65 Impact Factor
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ABSTRACT: Tolerance to drugs that affect neural activity is mediated, in part, by adaptive mechanisms that attempt to restore normal neural excitability. Changes in the expression of ion channel genes are thought to play an important role in these neural adaptations. The slo gene encodes the pore-forming subunit of BK-type Ca(2+)-activated K(+) channels, which regulate many aspects of neural activity. Given that induction of slo gene expression plays an important role in the acquisition of tolerance to sedating drugs, we investigated the molecular mechanism of gene induction. Using chromatin immunoprecipitation followed by real-time PCR, we show that a single brief sedation with the anesthetic benzyl alcohol generates a spatiotemporal pattern of histone H4 acetylation across the slo promoter region. Inducing histone acetylation with a histone deacetylase inhibitor yields a similar pattern of changes in histone acetylation, up-regulates slo expression, and phenocopies tolerance in a slo-dependent manner. The cAMP response element binding protein (CREB) is an important transcription factor mediating experience-based neuroadaptations. The slo promoter region contains putative binding sites for the CREB transcription factor. Chromatin immunoprecipitation assays show that benzyl alcohol sedation enhances CREB binding within the slo promoter region. Furthermore, activation of a CREB dominant-negative transgene blocks benzyl alcohol-induced changes in histone acetylation within the slo promoter region, slo induction, and behavioral tolerance caused by benzyl alcohol sedation. These findings provide unique evidence that links molecular epigenetic histone modifications and transcriptional induction of an ion channel gene with a single behavioral event.
PLoS Biology 11/2007; 5(10):e265. · 11.45 Impact Factor
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ABSTRACT: Fragile X syndrome (FX), the most common heritable cause of mental retardation and autism, is a developmental disorder characterized by physical, cognitive, and behavioral deficits. FX results from a trinucleotide expansion mutation in the fmr1 gene that reduces levels of fragile X mental retardation protein (FMRP). Although research efforts have focused on FMRP's impact on mGluR signaling, how the loss of FMRP leads to the individual symptoms of FX is not known. Previous studies on human FX blood cells revealed alterations in the cyclic adenosine 3', 5'-monophosphate (cAMP) cascade. We tested the hypothesis that cAMP signaling is altered in the FX nervous system using three different model systems. Induced levels of cAMP in platelets and in brains of fmr1 knockout mice are substantially reduced. Cyclic AMP induction is also significantly reduced in human FX neural cells. Furthermore, cAMP production is decreased in the heads of FX Drosophila and this defect can be rescued by reintroduction of the dfmr gene. Our results indicate that a robust defect in cAMP production in FX is conserved across species and suggest that cAMP metabolism may serve as a useful biomarker in the human disease population. Reduced cAMP induction has implications for the underlying causes of FX and autism spectrum disorders. Pharmacological agents known to modulate the cAMP cascade may be therapeutic in FX patients and can be tested in these models, thus supplementing current efforts centered on mGluR signaling.
PLoS ONE 02/2007; 2(9):e931. · 4.09 Impact Factor
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ABSTRACT: Gene-specific expansion of polyglutamine-encoding CAG repeats can cause neurodegenerative disorders, including Huntington's disease. It is believed that part of the pathological effect of the expanded protein is due to transcriptional dysregulation. Using Drosophila as a model, we show that cAMP-response element-binding protein (CREB) is involved in expanded polyglutamine-induced toxicity. A mutation in the Drosophila homolog of CREB, dCREB2, enhances lethality due to polyglutamine peptides (polyQ), and an additional copy of dCREB2 partially rescues this lethality. Neuronal expression of expanded polyQ attenuates in vivo CRE-mediated transcription of a reporter gene. As reported previously, overexpression of heat-shock protein 70 (Hsp70) rescues polyglutamine-dependent lethality. However, it does not rescue CREB-mediated transcription. The protective effects of CREB and heat-shock protein 70 against polyQ are additive, suggesting that targeting multiple pathways may be effective for treatment of polyglutamine diseases.
Proceedings of the National Academy of Sciences 08/2005; 102(29):10261-6. · 9.68 Impact Factor
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ABSTRACT: The cAMP response Element (CRE)-binding protein (CREB) is involved in many adaptive behaviors, including circadian rhythms. In order to assess CREB activity in vivo, we made transgenic flies carrying a CRE-luciferase reporter and showed that this reporter is CRE and dCREB2 responsive. dCREB2 is the Drosophila homolog of mammalian CREB?CREM. The transgenic luciferase activity cycles with a 24-h periodicity, suggesting that dCREB2 and period are somehow linked. The CRE-luciferase reporter is a useful monitor of circadian activity, and mutations can be found that affect its periodicity, baseline activity, or amplitude. Analysis of such mutations should reveal information about how particular genes affect the molecular machinery of circadian cycling and how different genes affect the activity of dCREB2.
Methods in enzymology 02/2005; 393:302-15. · 1.90 Impact Factor
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ABSTRACT: The Drosophila homolog of cAMP-response element-binding protein (CREB), dCREB2, exists with serine 231, equivalent to mammalian serine 133, in a predominantly phosphorylated state. Thus, unlike the mammalian protein, the primary regulation of dCREB2 may occur at a different step from serine 231 phosphorylation. Although bacterially expressed dCREB2 bound cAMP-response element sites, protein from Drosophila extracts was unable to do so unless treated with phosphatase. Phosphorylation of recombinant protein by casein kinase (CK) I or II, but not calcium-calmodulin kinase II or protein kinase A, inhibited DNA binding. Up to four conserved CK sites likely to be phosphorylated in vivo were responsible for this effect, and these sites were phosphorylated by a kinase present in Drosophila cell extracts that biochemically resembles CKII. We propose that the relative importance of different signaling pathways in regulating CREB activity may differ between Drosophila and mammals. In Drosophila, the dephosphorylation of CK sites appears to be the major regulatory step, while phosphorylation of serine 231 is necessary but secondary.
Journal of Biological Chemistry 04/2004; 279(13):12117-25. · 4.77 Impact Factor
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ABSTRACT: Synaptic stimulation activates signal transduction pathways, producing persistently active protein kinases. PKMzeta is a truncated, persistently active isoform of atypical protein kinase C-zeta (aPKCzeta), which lacks the N-terminal pseudosubstrate regulatory domain. Using a Pavlovian olfactory learning task in Drosophila, we found that induction of the mouse aPKMzeta (MaPKMzeta) transgene enhanced memory. The enhancement required persistent kinase activity and was temporally specific, with optimal induction at 30 minutes after training. Induction also enhanced memory after massed training and corrected the memory defect of radish mutants, but did not improve memory produced by spaced training. The 'M' isoform of the Drosophila homolog of MaPKCzeta (DaPKM) was present and active in fly heads. Chelerythrine, an inhibitor of PKMzeta, and the induction of a dominant-negative MaPKMzeta transgene inhibited memory without affecting learning. Finally, induction of DaPKM after training also enhanced memory. These results show that atypical PKM is sufficient to enhance memory in Drosophila and suggest that it is necessary for normal memory maintenance.
Nature Neuroscience 05/2002; 5(4):316-24. · 15.53 Impact Factor
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ABSTRACT: The cAMP response Element (CRE)–binding protein (CREB) is involved in many adaptive behaviors, including circadian rhythms. In order to assess CREB activity in vivo, we made transgenic flies carrying a CRE-luciferase reporter and showed that this reporter is CRE and dCREB2 responsive. dCREB2 is the Drosophila homolog of mammalian CREB⧸CREM. The transgenic luciferase activity cycles with a 24-h periodicity, suggesting that dCREB2 and period are somehow linked. The CRE-luciferase reporter is a useful monitor of circadian activity, and mutations can be found that affect its periodicity, baseline activity, or amplitude. Analysis of such mutations should reveal information about how particular genes affect the molecular machinery of circadian cycling and how different genes affect the activity of dCREB2.
Methods in Enzymology.
