351
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Craig TJ, Henley JM. Protein SUMOylation in spine structure and function. Curr Opin Neurobiol 2012; 22:480-7. [PMID: 22054923 PMCID: PMC3379963 DOI: 10.1016/j.conb.2011.10.017] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Revised: 10/18/2011] [Accepted: 10/18/2011] [Indexed: 11/18/2022]
Abstract
The active regulation of spine structure and function is of fundamental importance for information storage in the brain. Many proteins involved in spine development and activity-dependent remodelling are potential or validated substrates for modification by the Small Ubiquitin-like Modifier (SUMO). The functional consequences of neuronal protein SUMOylation appear diverse and, in many cases, have not yet been determined. However, for several proteins SUMOylation has been shown to be a key regulator, which has a profound impact on spine dynamics and protein trafficking and function. Here we provide an overview of neuronal SUMOylation and discuss how greater understanding of this relatively recently discovered posttranslational modification will provide insight into the complexity of protein interactions that control synaptic activity and dysfunction.
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Affiliation(s)
- Tim J Craig
- MRC Centre for Synaptic Plasticity, School of Biochemistry Medical Sciences Building, University of Bristol, University Walk, Bristol, BS8 1TD, UK
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352
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Wang JQ, Li HX, Chen XM, Mo FF, Qi RR, Guo JS, Cai YL. Temporal change in NMDA receptor signaling and GABAA receptor exypression in rat caudal vestibular nucleus during motion sickness habituation. Brain Res 2012; 1461:30-40. [DOI: 10.1016/j.brainres.2012.04.041] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Revised: 03/31/2012] [Accepted: 04/21/2012] [Indexed: 12/29/2022]
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353
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A novel ARC gene polymorphism is associated with reduced risk of Alzheimer’s disease. J Neural Transm (Vienna) 2012; 119:833-42. [DOI: 10.1007/s00702-012-0823-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2011] [Accepted: 05/03/2012] [Indexed: 02/06/2023]
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354
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Soulé J, Alme M, Myrum C, Schubert M, Kanhema T, Bramham CR. Balancing Arc synthesis, mRNA decay, and proteasomal degradation: maximal protein expression triggered by rapid eye movement sleep-like bursts of muscarinic cholinergic receptor stimulation. J Biol Chem 2012; 287:22354-66. [PMID: 22584581 DOI: 10.1074/jbc.m112.376491] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Cholinergic signaling induces Arc/Arg3.1, an immediate early gene crucial for synaptic plasticity. However, the molecular mechanisms that dictate Arc mRNA and protein dynamics during and after cholinergic epochs are little understood. Using human SH-SY5Y neuroblastoma cells, we show that muscarinic cholinergic receptor (mAchR) stimulation triggers Arc synthesis, whereas translation-dependent RNA decay and proteasomal degradation strictly limit the amount and duration of Arc expression. Chronic application of the mAchR agonist, carbachol (Cch), induces Arc transcription via ERK signaling and release of calcium from IP(3)-sensitive stores. Arc translation requires ERK activation, but not changes in intracellular calcium. Proteasomal degradation of Arc (half-life ∼37 min) was enhanced by thapsigargin, an inhibitor of the endoplasmic calcium-ATPase pump. Similar mechanisms of Arc protein regulation were observed in cultured rat hippocampal slices. Functionally, we studied the impact of cholinergic epoch duration and temporal pattern on Arc protein expression. Acute Cch treatment (as short as 2 min) induces transient, moderate Arc expression, whereas continuous treatment of more than 30 min induces maximal expression, followed by rapid decline. Cholinergic activity associated with rapid eye movement sleep may function to facilitate long term synaptic plasticity and memory. Employing a paradigm designed to mimic intermittent rapid eye movement sleep epochs, we show that application of Cch in a series of short bursts generates persistent and maximal Arc protein expression. The results demonstrate dynamic, multifaceted control of Arc synthesis during mAchR signaling, and implicate cholinergic epoch duration and repetition as critical determinants of Arc expression and function in synaptic plasticity and behavior.
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Affiliation(s)
- Jonathan Soulé
- Department of Biomedicine, KG Jebsen Centre for Research on Neuropsychiatric Disorders, University of Bergen, Jonas Lies vei 91, N-5009 Bergen, Norway
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355
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Craig TJ, Jaafari N, Petrovic MM, Jacobs SC, Rubin PP, Mellor JR, Henley JM. Homeostatic synaptic scaling is regulated by protein SUMOylation. J Biol Chem 2012; 287:22781-8. [PMID: 22582390 PMCID: PMC3391081 DOI: 10.1074/jbc.m112.356337] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Homeostatic scaling allows neurons to alter synaptic transmission to compensate for changes in network activity. Here, we show that suppression of network activity with tetrodotoxin, which increases surface expression of AMPA receptors (AMPARs), dramatically reduces levels of the deSUMOylating (where SUMO is small ubiquitin-like modifier) enzyme SENP1, leading to a consequent increase in protein SUMOylation. Overexpression of the catalytic domain of SENP1 prevents this scaling effect, and we identify Arc as a SUMO substrate involved in the tetrodotoxin-induced increase in AMPAR surface expression. Thus, protein SUMOylation plays an important and previously unsuspected role in synaptic trafficking of AMPARs that underlies homeostatic scaling.
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Affiliation(s)
- Tim J Craig
- Medical Research Council Centre for Synaptic Plasticity, School of Biochemistry, University of Bristol, Bristol BS8 1TD, United Kingdom
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356
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O'Rourke NA, Weiler NC, Micheva KD, Smith SJ. Deep molecular diversity of mammalian synapses: why it matters and how to measure it. Nat Rev Neurosci 2012; 13:365-79. [PMID: 22573027 DOI: 10.1038/nrn3170] [Citation(s) in RCA: 137] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Pioneering studies in the middle of the twentieth century revealed substantial diversity among mammalian chemical synapses and led to a widely accepted classification of synapse type on the basis of neurotransmitter molecule identity. Subsequently, powerful new physiological, genetic and structural methods have enabled the discovery of much deeper functional and molecular diversity within each traditional neurotransmitter type. Today, this deep diversity continues to pose both daunting challenges and exciting new opportunities for neuroscience. Our growing understanding of deep synapse diversity may transform how we think about and study neural circuit development, structure and function.
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Affiliation(s)
- Nancy A O'Rourke
- Department of Molecular and Cellular Physiology, Beckman Center, Stanford University School of Medicine, Stanford, California 94305, USA
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357
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Abstract
Death-mediating proteases such as caspases and caspase-3 in particular, have been implicated in neurodegenerative processes, aging and Alzheimer's disease. However, emerging evidence suggests that in addition to their classical role in cell death, caspases play a key role in modulating synaptic function. It is remarkable that active caspases-3, which can trigger widespread damage and degeneration, aggregates in structures as delicate as synapses and persists in neurons without causing acute cell death. Here, we evaluate this dichotomy, and discuss the hypothesis that caspase-3 may be a bifurcation point in cellular signaling, able to orient the neuronal response to stress down either pathological/apoptotic pathways or towards physiological cellular remodeling. We propose that temporal, spatial and other regulators of caspase activity are key determinants of the ultimate effect of caspase-3 activation in neurons. This concept has implications for differential roles of caspase-3 activation across the lifespan. Specifically, we propose that limited caspase-3 activation is critical for synaptic function in the healthy adult brain while chronic activation is involved in degenerative processes in the aging brain.
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358
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Cuadrado-Tejedor M, Hervias I, Ricobaraza A, Puerta E, Pérez-Roldán JM, García-Barroso C, Franco R, Aguirre N, García-Osta A. Sildenafil restores cognitive function without affecting β-amyloid burden in a mouse model of Alzheimer's disease. Br J Pharmacol 2012; 164:2029-41. [PMID: 21627640 DOI: 10.1111/j.1476-5381.2011.01517.x] [Citation(s) in RCA: 141] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND AND PURPOSE Inhibitors of phosphodiesterase 5 (PDE5) affect signalling pathways by elevating cGMP, which is a second messenger involved in processes of neuroplasticity. In the present study, the effects of the PDE5 inhibitor, sildenafil, on the pathological features of Alzheimer's disease and on memory-related behaviour were investigated. EXPERIMENTAL APPROACH Sildenafil was administered to the Tg2576 transgenic mouse model of Alzheimer's disease and to age-matched negative littermates (controls). Memory function was analysed using the Morris water maze test and fear conditioning tasks. Biochemical analyses were performed in brain lysates from animals treated with saline or with sildenafil. KEY RESULTS Treatment of aged Tg2576 animals with sildenafil completely reversed their cognitive impairment. Such changes were accompanied in the hippocampus by a reduction of tau hyperphosphorylation and a decrease in the activity of glycogen synthase kinase 3β (GSK3β) and of cyclin-dependent kinase 5 (CDK5) (p25/p35 ratio). Moreover, sildenafil also increased levels of brain-derived neurotrophic factor (BDNF) and the activity-regulated cytoskeletal-associated protein (Arc) in the hippocampus without any detectable modification of brain amyloid burden. CONCLUSIONS AND IMPLICATIONS Sildenafil improved cognitive functions in Tg2576 mice and the effect was not related to changes in the amyloid burden. These data further strengthen the potential of sildenafil as a therapeutic agent for Alzheimer's disease.
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Affiliation(s)
- M Cuadrado-Tejedor
- Division of Neurosciences, CIMA, University of Navarra, Avenida Pio XII 55, Pamplona, Spain
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359
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Zoghbi HY, Bear MF. Synaptic dysfunction in neurodevelopmental disorders associated with autism and intellectual disabilities. Cold Spring Harb Perspect Biol 2012; 4:a009886. [PMID: 22258914 PMCID: PMC3282414 DOI: 10.1101/cshperspect.a009886] [Citation(s) in RCA: 523] [Impact Index Per Article: 43.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The discovery of the genetic causes of syndromic autism spectrum disorders and intellectual disabilities has greatly informed our understanding of the molecular pathways critical for normal synaptic function. The top-down approaches using human phenotypes and genetics helped identify causative genes and uncovered the broad spectrum of neuropsychiatric features that can result from various mutations in the same gene. Importantly, the human studies unveiled the exquisite sensitivity of cognitive function to precise levels of many diverse proteins. Bottom-up approaches applying molecular, biochemical, and neurophysiological studies to genetic models of these disorders revealed unsuspected pathogenic mechanisms and identified potential therapeutic targets. Moreover, studies in model organisms showed that symptoms of these devastating disorders can be reversed, which brings hope that affected individuals might benefit from interventions even after symptoms set in. Scientists predict that insights gained from studying these rare syndromic disorders will have an impact on the more common nonsyndromic autism and mild cognitive deficits.
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Affiliation(s)
- Huda Y Zoghbi
- Howard Hughes Medical Institute, The Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, Houston, Texas 77030, ;
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360
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Seibt J, Dumoulin MC, Aton SJ, Coleman T, Watson A, Naidoo N, Frank MG. Protein synthesis during sleep consolidates cortical plasticity in vivo. Curr Biol 2012; 22:676-82. [PMID: 22386312 DOI: 10.1016/j.cub.2012.02.016] [Citation(s) in RCA: 112] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Revised: 01/16/2012] [Accepted: 02/07/2012] [Indexed: 01/12/2023]
Abstract
Sleep consolidates experience-dependent brain plasticity, but the precise cellular mechanisms mediating this process are unknown [1]. De novo cortical protein synthesis is one possible mechanism. In support of this hypothesis, sleep is associated with increased brain protein synthesis [2, 3] and transcription of messenger RNAs (mRNAs) involved in protein synthesis regulation [4, 5]. Protein synthesis in turn is critical for memory consolidation and persistent forms of plasticity in vitro and in vivo [6, 7]. However, it is unknown whether cortical protein synthesis in sleep serves similar functions. We investigated the role of protein synthesis in the sleep-dependent consolidation of a classic form of cortical plasticity in vivo (ocular dominance plasticity, ODP; [8, 9]) in the cat visual cortex. We show that intracortical inhibition of mammalian target of rapamycin (mTOR)-dependent protein synthesis during sleep abolishes consolidation but has no effect on plasticity induced during wakefulness. Sleep also promotes phosphorylation of protein synthesis regulators (i.e., 4E-BP1 and eEF2) and the translation (but not transcription) of key plasticity related mRNAs (ARC and BDNF). These findings show that sleep promotes cortical mRNA translation. Interruption of this process has functional consequences, because it abolishes the consolidation of experience in the cortex.
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Affiliation(s)
- Julie Seibt
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6074, USA
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361
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Erasing synapses in sleep: is it time to be SHY? Neural Plast 2012; 2012:264378. [PMID: 22530156 PMCID: PMC3317003 DOI: 10.1155/2012/264378] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2011] [Accepted: 12/04/2011] [Indexed: 02/04/2023] Open
Abstract
Converging lines of evidence strongly support a role for sleep in brain plasticity. An elegant idea that may explain how sleep accomplishes this role is the "synaptic homeostasis hypothesis (SHY)." According to SHY, sleep promotes net synaptic weakening which offsets net synaptic strengthening that occurs during wakefulness. SHY is intuitively appealing because it relates the homeostatic regulation of sleep to an important function (synaptic plasticity). SHY has also received important experimental support from recent studies in Drosophila melanogaster. There remain, however, a number of unanswered questions about SHY. What is the cellular mechanism governing SHY? How does it fit with what we know about plasticity mechanisms in the brain? In this review, I discuss the evidence and theory of SHY in the context of what is known about Hebbian and non-Hebbian synaptic plasticity. I conclude that while SHY remains an elegant idea, the underlying mechanisms are mysterious and its functional significance unknown.
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362
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Hunsaker MR. Comprehensive neurocognitive endophenotyping strategies for mouse models of genetic disorders. Prog Neurobiol 2012; 96:220-41. [PMID: 22266125 PMCID: PMC3289520 DOI: 10.1016/j.pneurobio.2011.12.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Revised: 12/06/2011] [Accepted: 12/20/2011] [Indexed: 01/21/2023]
Abstract
There is a need for refinement of the current behavioral phenotyping methods for mouse models of genetic disorders. The current approach is to perform a behavioral screen using standardized tasks to define a broad phenotype of the model. This phenotype is then compared to what is known concerning the disorder being modeled. The weakness inherent in this approach is twofold: First, the tasks that make up these standard behavioral screens do not model specific behaviors associated with a given genetic mutation but rather phenotypes affected in various genetic disorders; secondly, these behavioral tasks are insufficiently sensitive to identify subtle phenotypes. An alternate phenotyping strategy is to determine the core behavioral phenotypes of the genetic disorder being studied and develop behavioral tasks to evaluate specific hypotheses concerning the behavioral consequences of the genetic mutation. This approach emphasizes direct comparisons between the mouse and human that facilitate the development of neurobehavioral biomarkers or quantitative outcome measures for studies of genetic disorders across species.
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Affiliation(s)
- Michael R Hunsaker
- Department of Neurological Surgery, University of California, Davis, Davis, CA 95616, USA.
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363
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Gal-Ben-Ari S, Rosenblum K. Molecular mechanisms underlying memory consolidation of taste information in the cortex. Front Behav Neurosci 2012; 5:87. [PMID: 22319481 PMCID: PMC3251832 DOI: 10.3389/fnbeh.2011.00087] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2011] [Accepted: 12/12/2011] [Indexed: 12/22/2022] Open
Abstract
The senses of taste and odor are both chemical senses. However, whereas an organism can detect an odor at a relatively long distance from its source, taste serves as the ultimate proximate gatekeeper of food intake: it helps in avoiding poisons and consuming beneficial substances. The automatic reaction to a given taste has been developed during evolution and is well adapted to conditions that may occur with high probability during the lifetime of an organism. However, in addition to this automatic reaction, animals can learn and remember tastes, together with their positive or negative values, with high precision and in light of minimal experience. This ability of mammalians to learn and remember tastes has been studied extensively in rodents through application of reasonably simple and well defined behavioral paradigms. The learning process follows a temporal continuum similar to those of other memories: acquisition, consolidation, retrieval, relearning, and reconsolidation. Moreover, inhibiting protein synthesis in the gustatory cortex (GC) specifically affects the consolidation phase of taste memory, i.e., the transformation of short- to long-term memory, in keeping with the general biochemical definition of memory consolidation. This review aims to present a general background of taste learning, and to focus on recent findings regarding the molecular mechanisms underlying taste–memory consolidation in the GC. Specifically, the roles of neurotransmitters, neuromodulators, immediate early genes, and translation regulation are addressed.
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364
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Network, cellular, and molecular mechanisms underlying long-term memory formation. Curr Top Behav Neurosci 2012; 15:73-115. [PMID: 22976275 DOI: 10.1007/7854_2012_229] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The neural network stores information through activity-dependent synaptic plasticity that occurs in populations of neurons. Persistent forms of synaptic plasticity may account for long-term memory storage, and the most salient forms are the changes in the structure of synapses. The theory proposes that encoding should use a sparse code and evidence suggests that this can be achieved through offline reactivation or by sparse initial recruitment of the network units. This idea implies that in some cases the neurons that underwent structural synaptic plasticity might be a subpopulation of those originally recruited; However, it is not yet clear whether all the neurons recruited during acquisition are the ones that underwent persistent forms of synaptic plasticity and responsible for memory retrieval. To determine which neural units underlie long-term memory storage, we need to characterize which are the persistent forms of synaptic plasticity occurring in these neural ensembles and the best hints so far are the molecular signals underlying structural modifications of the synapses. Structural synaptic plasticity can be achieved by the activity of various signal transduction pathways, including the NMDA-CaMKII and ACh-MAPK. These pathways converge with the Rho family of GTPases and the consequent ERK 1/2 activation, which regulates multiple cellular functions such as protein translation, protein trafficking, and gene transcription. The most detailed explanation may come from models that allow us to determine the contribution of each piece of this fascinating puzzle that is the neuron and the neural network.
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365
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Kubik S, Miyashita T, Kubik-Zahorodna A, Guzowski JF. Loss of activity-dependent Arc gene expression in the retrosplenial cortex after hippocampal inactivation: interaction in a higher-order memory circuit. Neurobiol Learn Mem 2011; 97:124-31. [PMID: 22100445 DOI: 10.1016/j.nlm.2011.10.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Revised: 10/21/2011] [Accepted: 10/24/2011] [Indexed: 01/19/2023]
Abstract
The rodent hippocampus is well known for its role in spatial navigation and memory, and recent evidence points to the retrosplenial cortex (RSC) as another element of a higher order spatial and mnemonic circuit. However, the functional interplay between hippocampus and RSC during spatial navigation remains poorly understood. To investigate this interaction, we examined cell activity in the RSC during spatial navigation in the water maze before and after acute hippocampal inactivation using expression of two immediate-early genes (IEGs), Arc and Homer 1a (H1a). Adult male rats were trained in a spatial water maze task for 4 days. On day 5, the rats received two testing/training sessions separated by 20 min. Eight minutes before the second session, different groups of rats received bilateral intrahippocampal infusion of tetrodotoxin (TTX), muscimol (MUS), or vehicle. Another group of rats (uni-TTX) received infusion of TTX in one hippocampus and vehicle in the other. Signals from Arc and H1a RNA probes correspond to the post- and pre-infusion sessions, respectively. Bilateral TTX and MUS impaired spatial memory, as expected, and decreased Arc expression in CA1 of hippocampus. Importantly, bilateral inactivation of hippocampus resulted in loss of behavior-induced Arc expression in RSC. Despite a lateralized effect in CA1, Arc expression was equivalently and bilaterally decreased in RSC of uni-TTX rats, consistent with a network level interaction between hippocampus and RSC. We conclude that the loss of hippocampal input alters activity of RSC neurons and compromises their ability to engage plastic processes dependent on IEG expression.
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Affiliation(s)
- Stepan Kubik
- Center for the Neurobiology of Learning and Memory, Department of Neurobiology and Behavior, University of California, Irvine, CA 92697-3800, USA
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366
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The importance of having Arc: expression of the immediate-early gene Arc is required for hippocampus-dependent fear conditioning and blocked by NMDA receptor antagonism. J Neurosci 2011; 31:11200-7. [PMID: 21813681 DOI: 10.1523/jneurosci.2211-11.2011] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Long-lasting, experience-dependent changes in synaptic strength are widely thought to underlie the formation of memories. Many forms of learning-related plasticity are likely mediated by NMDA receptor activation and plasticity-related gene expression in brain areas thought to be important for learning and memory, including the hippocampus. Here, we examined the putative role of activity-regulated cytoskeletal-associated protein (Arc), an immediate-early gene (IEG) whose expression is tightly linked to the induction and maintenance of some forms of neuronal plasticity, in hippocampus-dependent and hippocampus-independent forms of learning. The extent to which learning-induced Arc expression may depend on NMDA receptor activation was also assessed. First, we observed an increase in Arc gene and protein products in both dorsal hippocampus (DH) and ventral hippocampus (VH) of male Sprague Dawley rats after hippocampus-dependent trace and contextual fear conditioning, but not after hippocampus-independent delay fear conditioning. Specific knockdown of Arc using antisense oligodeoxynucleotides (ODNs) in DH or VH attenuated the learning-related expression of Arc protein, and resulted in a dramatic impairment in trace and contextual, but not delay, fear conditioning. Finally, pretraining infusions of the NMDA receptor antagonist APV into the DH or VH blocked the learning-induced enhancement of Arc in a regionally selective manner, suggesting that NMDA receptor activation and Arc translation are functionally coupled to support hippocampus-dependent memory for fear conditioning. Collectively these results provide the first evidence suggesting that NMDA receptor-dependent expression of the IEG Arc in both DH and VH likely underlies the consolidation of a variety of forms of hippocampus-dependent learning.
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367
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Korb E, Finkbeiner S. Arc in synaptic plasticity: from gene to behavior. Trends Neurosci 2011; 34:591-8. [PMID: 21963089 DOI: 10.1016/j.tins.2011.08.007] [Citation(s) in RCA: 267] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2011] [Revised: 08/26/2011] [Accepted: 08/30/2011] [Indexed: 10/17/2022]
Abstract
The activity-regulated cytoskeletal (Arc) gene encodes a protein that is critical for memory consolidation. Arc is one of the most tightly regulated molecules known: neuronal activity controls Arc mRNA induction, trafficking and accumulation, and Arc protein production, localization and stability. Arc regulates synaptic strength through multiple mechanisms and is involved in essentially every known form of synaptic plasticity. It also mediates memory formation and is implicated in multiple neurological diseases. In this review, we will discuss how Arc is regulated and used as a tool to study neuronal activity. We will also attempt to clarify how its molecular functions correspond to its requirement in various forms of plasticity, discuss Arc's role in behavior and disease, and highlight critical unresolved questions.
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Affiliation(s)
- Erica Korb
- Gladstone Institute of Neurological Disease, San Francisco, CA, USA
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368
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Morin JP, Quiroz C, Mendoza-Viveros L, Ramirez-Amaya V, Bermudez-Rattoni F. Familiar taste induces higher dendritic levels of activity-regulated cytoskeleton-associated protein in the insular cortex than a novel one. Learn Mem 2011; 18:610-6. [PMID: 21921210 DOI: 10.1101/lm.2323411] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The immediate early gene (IEG) Arc is known to play an important role in synaptic plasticity; its protein is locally translated in the dendrites where it has been involved in several types of plasticity mechanisms. Because of its tight coupling with neuronal activity, Arc has been widely used as a tool to tag behaviorally activated networks. However, studies examining the modulation of Arc expression during and after learning have yielded somewhat contradictory results. Although some have reported that higher levels of Arc were induced by initial acquisition of a task rather than by reinstating a learned behavior, others have failed to observe such habituation of Arc transcription. Moreover, most of these studies have focused on the mRNA and, surprisingly, relatively little is known about how learning can affect Arc protein expression levels. Here we used taste recognition memory and examined Arc protein expression in the insular cortex of rats at distinct times during taste memory formation. Interestingly, we found that more Arc protein was induced by a familiar rather than by a novel taste. Moreover, this increase was inhibited by post-trial intrahippocampal anisomycin injections, a treatment known to inhibit safe-taste memory consolidation. In addition, confocal microscopy analysis of immunofluorescence stained tissue revealed that the proportion of IC neurons expressing Arc was the same in animals exposed to novel and familiar taste, but Arc immunoreactivity in dendrites was dramatically higher in rats exposed to the familiar taste. These results provide novel insights on how experience affects cortical plasticity.
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Affiliation(s)
- Jean-Pascal Morin
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México DF, México
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369
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Walls SA, Macklin ZL, Devaud LL. Ethanol-induced loss-of-righting response during ethanol withdrawal in male and female rats: associations with alterations in Arc labeling. Alcohol Clin Exp Res 2011; 36:234-41. [PMID: 21895716 DOI: 10.1111/j.1530-0277.2011.01613.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
BACKGROUND There is increasing evidence for relevant sex differences in responses to ethanol. Several investigations have found differences in expression and recovery from ethanol withdrawal (EW) in people and across various animal models. We have found that female rats recover more quickly than male rats and show differential responses to various behavioral assessments and pharmacological challenges during withdrawal. The purpose of this study was to determine whether sex differences in EW behaviors extend to the hypnotic effects of acute ethanol administration. METHODS We used a repeated measures design to assess duration and latency for loss-of-righting reflex following an acute injection of ethanol (4.2 g/kg; 20% w/v) to pair-fed control or ethanol-withdrawn animals at 1 and 3 days EW in male, female, and ovariectomized female (OVX) rats. We determined protein levels of the activity-regulated cytoskeletal protein (Arc), used as a marker for synaptic activity in glutamatergic synapses, in the motor cortex and prefrontal cortex across these same treatment conditions. RESULTS Ethanol-withdrawn animals had a reduced ethanol-induced sleep time compared to controls at 1 day EW. Sleep time remained shortened at 3 days EW for males and OVX, but not females. Arc protein levels in motor cortex and preoptic nuclei significantly increased at 1 day EW across all sex conditions, suggestive of an association with the reduced ethanol-induced sleep times during EW. Arc levels increased further for males and OVX, but not females, at the 3 days EW time point. CONCLUSIONS These findings add further support to sex differences in effects of and responses to ethanol. They suggest that the more rapid recovery from EW for females than males also includes expression of tolerance to the hypnotic effects of ethanol. These sex differences may involve some differential neuroadaptations in glutamatergic signaling.
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Affiliation(s)
- Shawn A Walls
- Department of Molecular and Biomedical Sciences, University of Maine, Orono, Maine, USA
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370
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Yao J, Chen S, Mao Z, Cadenas E, Brinton RD. 2-Deoxy-D-glucose treatment induces ketogenesis, sustains mitochondrial function, and reduces pathology in female mouse model of Alzheimer's disease. PLoS One 2011; 6:e21788. [PMID: 21747957 PMCID: PMC3128612 DOI: 10.1371/journal.pone.0021788] [Citation(s) in RCA: 121] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Accepted: 06/08/2011] [Indexed: 11/19/2022] Open
Abstract
Previously, we demonstrated that mitochondrial bioenergetic deficits preceded Alzheimer's disease (AD) pathology in the female triple-transgenic AD (3xTgAD) mouse model. In parallel, 3xTgAD mice exhibited elevated expression of ketogenic markers, indicating a compensatory mechanism for energy production in brain. This compensatory response to generate an alternative fuel source was temporary and diminished with disease progression. To determine whether this compensatory alternative fuel system could be sustained, we investigated the impact of 2-deoxy-D-glucose (2-DG), a compound known to induce ketogenesis, on bioenergetic function and AD pathology burden in brain. 6-month-old female 3xTgAD mice were fed either a regular diet (AIN-93G) or a diet containing 0.04% 2-DG for 7 weeks. 2-DG diet significantly increased serum ketone body level and brain expression of enzymes required for ketone body metabolism. The 2-DG-induced maintenance of mitochondrial bioenergetics was paralleled by simultaneous reduction in oxidative stress. Further, 2-DG treated mice exhibited a significant reduction of both amyloid precursor protein (APP) and amyloid beta (Aβ) oligomers, which was paralleled by significantly increased α-secretase and decreased γ-secretase expression, indicating that 2-DG induced a shift towards a non-amyloidogenic pathway. In addition, 2-DG increased expression of genes involved in Aβ clearance pathways, degradation, sequestering, and transport. Concomitant with increased bioenergetic capacity and reduced β-amyloid burden, 2-DG significantly increased expression of neurotrophic growth factors, BDNF and NGF. Results of these analyses demonstrate that dietary 2-DG treatment increased ketogenesis and ketone metabolism, enhanced mitochondrial bioenergetic capacity, reduced β-amyloid generation and increased mechanisms of β-amyloid clearance. Further, these data link bioenergetic capacity with β-amyloid generation and demonstrate that β-amyloid burden was dynamic and reversible, as 2-DG reduced activation of the amyloidogenic pathway and increased mechanisms of β-amyloid clearance. Collectively, these data provide preclinical evidence for dietary 2-DG as a disease-modifying intervention to delay progression of bioenergetic deficits in brain and associated β-amyloid burden.
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Affiliation(s)
- Jia Yao
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California, United States of America
| | - Shuhua Chen
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California, United States of America
| | - Zisu Mao
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California, United States of America
| | - Enrique Cadenas
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California, United States of America
| | - Roberta Diaz Brinton
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California, United States of America
- Department of Neurology, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
- * E-mail: .
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