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Ye S, Kim JI, Kim J, Kaang BK. Overexpression of activated CaMKII in the CA1 hippocampus impairs context discrimination, but not contextual conditioning. Mol Brain 2019; 12:32. [PMID: 30953515 PMCID: PMC6449978 DOI: 10.1186/s13041-019-0454-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2019] [Accepted: 03/27/2019] [Indexed: 11/29/2022] Open
Abstract
Calcium/Calmodulin-dependent protein kinase II (CaMKII) plays a key role in the molecular mechanism of memory formation. CaMKII is known to be activated specifically in the activated spines during memory formation. However, it is unclear whether the specific activation of CaMKII is necessary for encoding information. Here, we overexpressed active form of CaMKII (CaMKII*) in the hippocampal CA1 region to activate CaMKII nonspecifically. Moreover, we examined context-discrimination performance of mice. We found that the mice with overexpression of CaMKII* showed impaired context-discrimination ability, while the contextual fear conditioning remained intact. These results indicate that spatial specificity of CaMKII activation is necessary for context discrimination.
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Affiliation(s)
- Sanghyun Ye
- School of Biological Sciences, Seoul National University, Gwanak-gu, Seoul, 08826, South Korea
| | - Ji-Il Kim
- School of Biological Sciences, Seoul National University, Gwanak-gu, Seoul, 08826, South Korea
| | - Jooyoung Kim
- School of Biological Sciences, Seoul National University, Gwanak-gu, Seoul, 08826, South Korea
| | - Bong-Kiun Kaang
- School of Biological Sciences, Seoul National University, Gwanak-gu, Seoul, 08826, South Korea.
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Chen YF, Chen ZX, Wang RH, Shi YW, Xue L, Wang XG, Zhao H. Knockdown of CLC-3 in the hippocampal CA1 impairs contextual fear memory. Prog Neuropsychopharmacol Biol Psychiatry 2019; 89:132-145. [PMID: 30025794 DOI: 10.1016/j.pnpbp.2018.07.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Revised: 06/11/2018] [Accepted: 07/05/2018] [Indexed: 01/01/2023]
Abstract
Previous studies support a critical role of hippocampus in contextual fear memory. Structural and functional alterations of hippocampus occur frequently in posttraumatic stress disorders (PTSD). Recent reports reveal that knockout of CLC-3, a member of the CLC family of anion channels and transporters, leads to neuronal degeneration and loss of hippocampus. However, the role of CLC-3 in contextual fear memory remains unknown. Using adenovirus and adeno-associated virus gene transfer to knockdown CLC-3 in hippocampal CA1, we investigate the role of CLC-3 in contextual fear memory. CLC-3 expression is increased in hippocampal CA1 after formation of long-term contextual fear memory. Knockdown of CLC-3 by adenovirus infusion in hippocampal CA1 significantly attenuates the contextual fear memory, reduces spine density, induces defects of excitatory synaptic ultrastructure showed by the decreased PSD length, PSD thickness and active zone length, and impairs L-LTP induction and maintenance. Knockdown of CLC-3 also induces the synaptic NMDAR subunit composition to an increased GluN2A/GluN2B ratio pattern and reduces the activity of CaMKII-α. Furthermore, selectively knockdown of CLC-3 in excitatory neurons by adeno-associated virus driven from CaMKII-α promoter is sufficient to impair long-term contextual fear memory. These findings highlight that CLC-3 in hippocampal CA1 is necessary for contextual fear memory.
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Affiliation(s)
- Ye-Fei Chen
- Faculty of Forensic Medicine, Zhongshan School of Medicine, Sun Yat-sen University, China; Guangdong Province Translational Forensic Medicine Engineering Technology Research Center, Zhongshan School of Medicine, Sun Yat-sen University, China; Guangdong Province Key Laboratory of Brain Function and Disease, Zhongshan School of Medicine, Sun Yat-sen University, China
| | - Zi-Xiang Chen
- Faculty of Forensic Medicine, Zhongshan School of Medicine, Sun Yat-sen University, China
| | - Run-Hua Wang
- Faculty of Forensic Medicine, Zhongshan School of Medicine, Sun Yat-sen University, China
| | - Yan-Wei Shi
- Faculty of Forensic Medicine, Zhongshan School of Medicine, Sun Yat-sen University, China; Guangdong Province Translational Forensic Medicine Engineering Technology Research Center, Zhongshan School of Medicine, Sun Yat-sen University, China; Guangdong Province Key Laboratory of Brain Function and Disease, Zhongshan School of Medicine, Sun Yat-sen University, China
| | - Li Xue
- Faculty of Forensic Medicine, Zhongshan School of Medicine, Sun Yat-sen University, China; Guangdong Province Translational Forensic Medicine Engineering Technology Research Center, Zhongshan School of Medicine, Sun Yat-sen University, China; Guangdong Province Key Laboratory of Brain Function and Disease, Zhongshan School of Medicine, Sun Yat-sen University, China
| | - Xiao-Guang Wang
- Faculty of Forensic Medicine, Zhongshan School of Medicine, Sun Yat-sen University, China; Guangdong Province Translational Forensic Medicine Engineering Technology Research Center, Zhongshan School of Medicine, Sun Yat-sen University, China; Guangdong Province Key Laboratory of Brain Function and Disease, Zhongshan School of Medicine, Sun Yat-sen University, China.
| | - Hu Zhao
- Faculty of Forensic Medicine, Zhongshan School of Medicine, Sun Yat-sen University, China; Guangdong Province Translational Forensic Medicine Engineering Technology Research Center, Zhongshan School of Medicine, Sun Yat-sen University, China; Guangdong Province Key Laboratory of Brain Function and Disease, Zhongshan School of Medicine, Sun Yat-sen University, China.
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Mechanisms of fear learning and extinction: synaptic plasticity-fear memory connection. Psychopharmacology (Berl) 2019; 236:163-182. [PMID: 30415278 PMCID: PMC6374177 DOI: 10.1007/s00213-018-5104-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Accepted: 11/02/2018] [Indexed: 12/21/2022]
Abstract
RATIONALE The ability to memorize threat-associated cues and subsequently react to them, exhibiting escape or avoidance responses, is an essential, often life-saving behavioral mechanism that can be experimentally studied using the fear (threat) conditioning training paradigm. Presently, there is substantial evidence supporting the Synaptic Plasticity-Memory (SPM) hypothesis in relation to the mechanisms underlying the acquisition, retention, and extinction of conditioned fear memory. OBJECTIVES The purpose of this review article is to summarize findings supporting the SPM hypothesis in the context of conditioned fear control, applying the set of criteria and tests which were proposed as necessary to causally link lasting changes in synaptic transmission in corresponding neural circuits to fear memory acquisition and extinction with an emphasis on their pharmacological diversity. RESULTS The mechanisms of synaptic plasticity in fear circuits exhibit complex pharmacological profiles and satisfy all four SPM criteria-detectability, anterograde alteration, retrograde alteration, and mimicry. CONCLUSION The reviewed findings, accumulated over the last two decades, provide support for both necessity and sufficiency of synaptic plasticity in fear circuits for fear memory acquisition and retention, and, in part, for fear extinction, with the latter requiring additional experimental work.
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Bear MF, Cooke SF, Giese KP, Kaang BK, Kennedy MB, Kim JI, Morris RGM, Park P. In memoriam: John Lisman - commentaries on CaMKII as a memory molecule. Mol Brain 2018; 11:76. [PMID: 30593282 PMCID: PMC6309094 DOI: 10.1186/s13041-018-0419-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Accepted: 10/24/2018] [Indexed: 11/10/2022] Open
Abstract
Shortly before he died in October 2017, John Lisman submitted an invited review to Molecular Brain on 'Criteria for identifying the molecular basis of the engram (CaMKII, PKMζ)'. John had no opportunity to read the referees' comments, and as a mark of the regard in which he was held by the neuroscience community the Editors decided to publish his review as submitted. This obituary takes the form of a series of commentaries on Lisman's review. At the same time we are publishing as a separate article a longer response by Todd Sacktor and André Fenton entitled 'What does LTP tell us about the roles of CaMKII and PKMζ in memory?' which presents the case for a rival memory molecule, PKMζ.
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Affiliation(s)
- Mark F. Bear
- Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
| | - Sam F. Cooke
- King’s College London, Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience, De Crespigny Park, London, SE5 8AF UK
| | - Karl Peter Giese
- King’s College London, Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience, De Crespigny Park, London, SE5 8AF UK
| | - Bong-Kiun Kaang
- Department of Biological Sciences, Seoul National University, Gwanak-gu, Seoul, Republic of Korea
| | - Mary B. Kennedy
- The Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125 USA
| | - Ji-il Kim
- Department of Biological Sciences, Seoul National University, Gwanak-gu, Seoul, Republic of Korea
| | - Richard G. M. Morris
- Laboratory for Cognitive Neuroscience, Centre for Discovery Brain Sciences, Edinburgh Neuroscience, Edinburgh, EH8 9JZ UK
| | - Pojeong Park
- Department of Biological Sciences, Seoul National University, Gwanak-gu, Seoul, Republic of Korea
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What does LTP tell us about the roles of CaMKII and PKMζ in memory? Mol Brain 2018; 11:77. [PMID: 30593289 PMCID: PMC6309091 DOI: 10.1186/s13041-018-0420-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Accepted: 10/24/2018] [Indexed: 11/18/2022] Open
Abstract
In “Criteria for identifying the molecular basis of the engram (CaMKII, PKMζ),” Lisman proposes that elucidating the mechanism of LTP maintenance is key to understanding memory storage. He suggests three criteria for a maintenance mechanism to evaluate data on CaMKII and PKMζ as memory storage molecules: necessity, occlusion, and erasure. Here we show that when the criteria are tested, the results reveal important differences between the molecules. Inhibiting PKMζ reverses established, protein synthesis-dependent late-LTP, without affecting early-LTP or baseline synaptic transmission. In contrast, blocking CaMKII has two effects: 1) inhibiting CaMKII activity blocks LTP induction but not maintenance, and 2) disrupting CaMKII interactions with NMDARs in the postsynaptic density (PSD) depresses both early-LTP and basal synaptic transmission equivalently. To identify a maintenance mechanism, we propose a fourth criterion — persistence. PKMζ increases for hours during LTP maintenance in hippocampal slices, and for over a month in specific brain regions during long-term memory storage in conditioned animals. In contrast, increased CaMKII activity lasts only minutes following LTP induction, and CaMKII translocation to the PSD in late-LTP or memory has not been reported. Lastly, do the PKMζ and CaMKII models integrate the many other signaling molecules important for LTP? Activity-dependent PKMζ synthesis is regulated by many of the signaling molecules that induce LTP, including CaMKII, providing a plausible mechanism for new gene expression in the persistent phosphorylation by PKMζ maintaining late-LTP and memory. In contrast, CaMKII autophosphorylation and translocation do not appear to require new protein synthesis. Therefore, the cumulative evidence supports a core role for PKMζ in late-LTP and long-term memory maintenance, and separate roles for CaMKII in LTP induction and for the maintenance of postsynaptic structure and synaptic transmission in a mechanism distinct from late-LTP.
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56
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Clarke SE. Analog Signaling With the "Digital" Molecular Switch CaMKII. Front Comput Neurosci 2018; 12:92. [PMID: 30524260 PMCID: PMC6262075 DOI: 10.3389/fncom.2018.00092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Accepted: 10/31/2018] [Indexed: 11/13/2022] Open
Abstract
Molecular switches, such as the protein kinase CaMKII, play a fundamental role in cell signaling by decoding inputs into either high or low states of activity; because the high activation state can be turned on and persist after the input ceases, these switches have earned a reputation as "digital." Although this on/off, binary perspective has been valuable for understanding long timescale synaptic plasticity, accumulating experimental evidence suggests that the CaMKII switch can also control plasticity on short timescales. To investigate this idea further, a non-autonomous, nonlinear ordinary differential equation, representative of a general bistable molecular switch, is analyzed. The results suggest that switch activity in regions surrounding either the high- or low-stable states of activation could act as a reliable analog signal, whose short timescale fluctuations relative to equilibrium track instantaneous input frequency. The model makes intriguing predictions and is validated against previous work demonstrating its suitability as a minimal representation of switch dynamics; in combination with existing experimental evidence, the theory suggests a multiplexed encoding of instantaneous frequency information over short timescales, with integration of total activity over longer timescales.
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Affiliation(s)
- Stephen E Clarke
- Department of Bioengineering, Department of Neurosurgery, Stanford University, Stanford, CA, United States
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57
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Zalcman G, Federman N, Romano A. CaMKII Isoforms in Learning and Memory: Localization and Function. Front Mol Neurosci 2018; 11:445. [PMID: 30564099 PMCID: PMC6288437 DOI: 10.3389/fnmol.2018.00445] [Citation(s) in RCA: 96] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 11/19/2018] [Indexed: 12/13/2022] Open
Abstract
Calcium/calmodulin-dependent protein kinase II (CaMKII) is a key protein kinase in neural plasticity and memory, as have been shown in several studies since the first evidence in long-term potentiation (LTP) 30 years ago. However, most of the studies were focused mainly in one of the four isoforms of this protein kinase, the CaMKIIα. Here we review the characteristics and the role of each of the four isoforms in learning, memory and neural plasticity, considering the well known local role of α and β isoforms in dendritic terminals as well as recent findings about the γ isoform as calcium signals transducers from synapse to nucleus and δ isoform as a kinase required for a more persistent memory trace.
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Affiliation(s)
- Gisela Zalcman
- Instituto de Fisiología, Biología Molecular y Neurociencias, Universidad de Buenos Aires - Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina.,Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Noel Federman
- Instituto de Fisiología, Biología Molecular y Neurociencias, Universidad de Buenos Aires - Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina.,Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Arturo Romano
- Instituto de Fisiología, Biología Molecular y Neurociencias, Universidad de Buenos Aires - Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina.,Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
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58
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Singh D, Bhalla US. Subunit exchange enhances information retention by CaMKII in dendritic spines. eLife 2018; 7:e41412. [PMID: 30418153 PMCID: PMC6286124 DOI: 10.7554/elife.41412] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2018] [Accepted: 11/09/2018] [Indexed: 12/15/2022] Open
Abstract
Molecular bistables are strong candidates for long-term information storage, for example, in synaptic plasticity. Calcium/calmodulin-dependent protein Kinase II (CaMKII) is a highly expressed synaptic protein which has been proposed to form a molecular bistable switch capable of maintaining its state for years despite protein turnover and stochastic noise. It has recently been shown that CaMKII holoenzymes exchange subunits among themselves. Here, we used computational methods to analyze the effect of subunit exchange on the CaMKII pathway in the presence of diffusion in two different micro-environments, the post synaptic density (PSD) and spine cytosol. We show that CaMKII exhibits multiple timescales of activity due to subunit exchange. Further, subunit exchange enhances information retention by CaMKII both by improving the stability of its switching in the PSD, and by slowing the decay of its activity in the spine cytosol. The existence of diverse timescales in the synapse has important theoretical implications for memory storage in networks.
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Affiliation(s)
- Dilawar Singh
- National Centre for Biological SciencesTata Institute of Fundamental ResearchBangaloreIndia
| | - Upinder Singh Bhalla
- National Centre for Biological SciencesTata Institute of Fundamental ResearchBangaloreIndia
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59
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Developmental transitions in amygdala PKC isoforms and AMPA receptor expression associated with threat memory in infant rats. Sci Rep 2018; 8:14679. [PMID: 30279521 PMCID: PMC6168531 DOI: 10.1038/s41598-018-32762-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Accepted: 09/03/2018] [Indexed: 12/12/2022] Open
Abstract
Although infants learn and remember, they rapidly forget, a phenomenon known as infantile amnesia. While myriad mechanisms impact this rapid forgetting, the molecular events supporting memory maintenance have yet to be explored. To explore memory mechanisms across development, we used amygdala-dependent odor-shock conditioning and focused on mechanisms important in adult memory, the AMPA receptor subunits GluA1/2 and upstream protein kinases important for trafficking AMPAR, protein kinase M zeta (PKMζ) and iota/lambda (PKCι/λ). We use odor-shock conditioning in infant rats because it is late-developing (postnatal day, PN10) and can be modulated by corticosterone during a sensitive period in early life. Our results show that memory-related molecules did not change in pups too young to learn threat (PN8) but were activated in pups old enough to learn (PN12), with increased PKMζ-PKCι/λ and GluA2 similar to that observed in adult memory, but with an uncharacteristic decrease in GluA1. This molecular signature and behavioral avoidance of the conditioned odor was recapitulated in PN8 pups injected with CORT before conditioning to precociously induce learning. Blocking learning via CORT inhibition in older pups (PN12) blocked the expression of these molecules. PN16 pups showed a more adult-like molecular cascade of increased PKMζ-PKCι/λ and GluA1–2. Finally, at all ages, zeta inhibitory peptide (ZIP) infusions into the amygdala 24 hr after conditioning blocked memory. Together, these results identify unique features of memory processes across early development: AMPAR subunits GluA1/2 and PKC isoform expression are differentially used, which may contribute to mechanisms of early life forgetting.
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60
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Vigil FA, Giese KP. Calcium/calmodulin-dependent kinase II and memory destabilization: a new role in memory maintenance. J Neurochem 2018; 147:12-23. [PMID: 29704430 PMCID: PMC6221169 DOI: 10.1111/jnc.14454] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Revised: 03/28/2018] [Accepted: 04/17/2018] [Indexed: 02/03/2023]
Abstract
In this review, we discuss the poorly explored role of calcium/calmodulin-dependent protein kinase II (CaMKII) in memory maintenance, and its influence on memory destabilization. After a brief review on CaMKII and memory destabilization, we present critical pieces of evidence suggesting that CaMKII activity increases retrieval-induced memory destabilization. We then proceed to propose two potential molecular pathways to explain the association between CaMKII activation and increased memory destabilization. This review will pinpoint gaps in our knowledge and discuss some 'controversial' observations, establishing the basis for new experiments on the role of CaMKII in memory reconsolidation. The role of CaMKII in memory destabilization is of great clinical relevance. Still, because of the lack of scientific literature on the subject, more basic science research is necessary to pursue this pathway as a clinical tool.
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Affiliation(s)
- Fabio Antonio Vigil
- Department of Cell and Integrative PhysiologyThe University of Texas Health San Antonio8403, Floyd Curl DriveSan AntonioTX 78229USA
| | - Karl Peter Giese
- Department of Basic and Clinical NeuroscienceKing's College London125 Coldharbour LaneLondonSE5 9NUUK
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61
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Differential Involvement of Kinase Activity of Ca 2+/Calmodulin-Dependent Protein Kinase IIα in Hippocampus- and Amygdala-Dependent Memory Revealed by Kinase-Dead Knock-In Mouse. eNeuro 2018; 5:eN-NWR-0133-18. [PMID: 30225347 PMCID: PMC6140109 DOI: 10.1523/eneuro.0133-18.2018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Revised: 07/23/2018] [Accepted: 07/27/2018] [Indexed: 01/07/2023] Open
Abstract
Ca2+/calmodulin-dependent protein kinase IIα (CaMKIIα) is a key mediator of activity-dependent neuronal modifications and has been implicated in the molecular mechanisms of learning and memory. Indeed, several types of CaMKIIα knock-in (KI) and knock-out (KO) mice revealed impairments in hippocampal synaptic plasticity and behavioral learning. On the other hand, a similar role for CaMKIIα has been implicated in amygdala-dependent memory, but detailed analyses have not much been performed yet. To better understand its involvement in amygdala-dependent memory as compared to hippocampus-dependent memory, here we performed biochemical analyses and behavioral memory tests using the kinase-dead CaMKIIα (K42R)-KI mouse. In the Morris water maze tasks, homozygous mutants performed well in the visible platform trials, while they failed to form spatial memory in the hippocampus-dependent hidden platform trials. In fear conditioning, these mice were impaired but showed a certain level of amygdala-dependent cued fear memory, which lasted four weeks, while they showed virtually no hippocampus-dependent context discrimination. Neither stronger stimulation nor repetitive stimulation compensated for their memory deficits. The differential outcome of hippocampus- and amygdala-dependent memory in the mutant mouse was not due to differential expression of CaMKIIα between the hippocampus and the amygdala, because biochemical analyses revealed that both kinase activity and protein levels of CaMKII were indistinguishable between the two brain regions. These results indicate that kinase activity of CaMKIIα is indispensable for hippocampus-dependent memory, but not necessarily for amygdala-dependent memory. There may be a secondary, CaMKIIα activity-independent pathway, in addition to the CaMKIIα activity-dependent pathway, in the acquisition of amygdala-dependent memory.
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Borovac J, Bosch M, Okamoto K. Regulation of actin dynamics during structural plasticity of dendritic spines: Signaling messengers and actin-binding proteins. Mol Cell Neurosci 2018; 91:122-130. [PMID: 30004015 DOI: 10.1016/j.mcn.2018.07.001] [Citation(s) in RCA: 105] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2018] [Revised: 06/25/2018] [Accepted: 07/06/2018] [Indexed: 12/17/2022] Open
Abstract
Activity-dependent plasticity of synaptic structure and function plays an essential role in neuronal development and in cognitive functions including learning and memory. The formation, maintenance and modulation of dendritic spines are mainly controlled by the dynamics of actin filaments (F-actin) through interaction with various actin-binding proteins (ABPs) and postsynaptic signaling messengers. Induction of long-term potentiation (LTP) triggers a cascade of events involving Ca2+ signaling, intracellular pathways such as cAMP and cGMP, and regulation of ABPs such as CaMKII, Cofilin, Aip1, Arp2/3, α-actinin, Profilin and Drebrin. We review here how these ABPs modulate the rate of assembly, disassembly, stabilization and bundling of F-actin during LTP induction. We highlight the crucial role that CaMKII exerts in both functional and structural plasticity by directly coupling Ca2+ signaling with F-actin dynamics through the β subunit. Moreover, we show how cAMP and cGMP second messengers regulate postsynaptic structural potentiation. Brain disorders such as Alzheimer's disease, schizophrenia or autism, are associated with alterations in the regulation of F-actin dynamics by these ABPs and signaling messengers. Thus, a better understanding of the molecular mechanisms controlling actin cytoskeleton can provide cues for the treatment of these disorders.
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Affiliation(s)
- Jelena Borovac
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON M5G 1X5, Canada; Department of Molecular Genetics, Faculty of Medicine, University of Toronto, Toronto, ON M5G 1X5, Canada
| | - Miquel Bosch
- Institute for Bioengineering of Catalonia, Barcelona 08028, Spain.
| | - Kenichi Okamoto
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON M5G 1X5, Canada; Department of Molecular Genetics, Faculty of Medicine, University of Toronto, Toronto, ON M5G 1X5, Canada.
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Remote Memory and Cortical Synaptic Plasticity Require Neuronal CCCTC-Binding Factor (CTCF). J Neurosci 2018; 38:5042-5052. [PMID: 29712785 DOI: 10.1523/jneurosci.2738-17.2018] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Revised: 03/30/2018] [Accepted: 04/08/2018] [Indexed: 12/20/2022] Open
Abstract
The molecular mechanism of long-term memory has been extensively studied in the context of the hippocampus-dependent recent memory examined within several days. However, months-old remote memory maintained in the cortex for long-term has not been investigated much at the molecular level yet. Various epigenetic mechanisms are known to be important for long-term memory, but how the 3D chromatin architecture and its regulator molecules contribute to neuronal plasticity and systems consolidation is still largely unknown. CCCTC-binding factor (CTCF) is an 11-zinc finger protein well known for its role as a genome architecture molecule. Male conditional knock-out mice in which CTCF is lost in excitatory neurons during adulthood showed normal recent memory in the contextual fear conditioning and spatial water maze tasks. However, they showed remarkable impairments in remote memory in both tasks. Underlying the remote memory-specific phenotypes, we observed that female CTCF conditional knock-out mice exhibit disrupted cortical LTP, but not hippocampal LTP. Similarly, we observed that CTCF deletion in inhibitory neurons caused partial impairment of remote memory. Through RNA sequencing, we observed that CTCF knockdown in cortical neuron culture caused altered expression of genes that are highly involved in cell adhesion, synaptic plasticity, and memory. These results suggest that remote memory storage in the cortex requires CTCF-mediated gene regulation in neurons, whereas recent memory formation in the hippocampus does not.SIGNIFICANCE STATEMENT CCCTC-binding factor (CTCF) is a well-known 3D genome architectural protein that regulates gene expression. Here, we use two different CTCF conditional knock-out mouse lines and reveal, for the first time, that CTCF is critically involved in the regulation of remote memory. We also show that CTCF is necessary for appropriate expression of genes, many of which we found to be involved in the learning- and memory-related processes. Our study provides behavioral and physiological evidence for the involvement of CTCF-mediated gene regulation in the remote long-term memory and elucidates our understanding of systems consolidation mechanisms.
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Sossin WS. Memory Synapses Are Defined by Distinct Molecular Complexes: A Proposal. Front Synaptic Neurosci 2018; 10:5. [PMID: 29695960 PMCID: PMC5904272 DOI: 10.3389/fnsyn.2018.00005] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 03/26/2018] [Indexed: 12/17/2022] Open
Abstract
Synapses are diverse in form and function. While there are strong evidential and theoretical reasons for believing that memories are stored at synapses, the concept of a specialized “memory synapse” is rarely discussed. Here, we review the evidence that memories are stored at the synapse and consider the opposing possibilities. We argue that if memories are stored in an active fashion at synapses, then these memory synapses must have distinct molecular complexes that distinguish them from other synapses. In particular, examples from Aplysia sensory-motor neuron synapses and synapses on defined engram neurons in rodent models are discussed. Specific hypotheses for molecular complexes that define memory synapses are presented, including persistently active kinases, transmitter receptor complexes and trans-synaptic adhesion proteins.
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Affiliation(s)
- Wayne S Sossin
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
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65
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Identification of long-lived synaptic proteins by proteomic analysis of synaptosome protein turnover. Proc Natl Acad Sci U S A 2018; 115:E3827-E3836. [PMID: 29610302 DOI: 10.1073/pnas.1720956115] [Citation(s) in RCA: 100] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Memory formation is believed to result from changes in synapse strength and structure. While memories may persist for the lifetime of an organism, the proteins and lipids that make up synapses undergo constant turnover with lifetimes from minutes to days. The molecular basis for memory maintenance may rely on a subset of long-lived proteins (LLPs). While it is known that LLPs exist, whether such proteins are present at synapses is unknown. We performed an unbiased screen using metabolic pulse-chase labeling in vivo in mice and in vitro in cultured neurons combined with quantitative proteomics. We identified synaptic LLPs with half-lives of several months or longer. Proteins in synaptic fractions generally exhibited longer lifetimes than proteins in cytosolic fractions. Protein turnover was sensitive to pharmacological manipulations of activity in neuronal cultures or in mice exposed to an enriched environment. We show that synapses contain LLPs that may underlie stabile long-lasting changes in synaptic structure and function.
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Lisman J, Cooper K, Sehgal M, Silva AJ. Memory formation depends on both synapse-specific modifications of synaptic strength and cell-specific increases in excitability. Nat Neurosci 2018; 21:309-314. [PMID: 29434376 PMCID: PMC5915620 DOI: 10.1038/s41593-018-0076-6] [Citation(s) in RCA: 209] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Accepted: 12/08/2017] [Indexed: 11/09/2022]
Abstract
The modification of synaptic strength produced by long-term potentiation (LTP) is widely thought to underlie memory storage. Indeed, given that hippocampal pyramidal neurons have >10,000 independently modifiable synapses, the potential for information storage by synaptic modification is enormous. However, recent work suggests that CREB-mediated global changes in neuronal excitability also play a critical role in memory formation. Because these global changes have a modest capacity for information storage compared with that of synaptic plasticity, their importance for memory function has been unclear. Here we review the newly emerging evidence for CREB-dependent control of excitability and discuss two possible mechanisms. First, the CREB-dependent transient change in neuronal excitability performs a memory-allocation function ensuring that memory is stored in ways that facilitate effective linking of events with temporal proximity (hours). Second, these changes may promote cell-assembly formation during the memory-consolidation phase. It has been unclear whether such global excitability changes and local synaptic mechanisms are complementary. Here we argue that the two mechanisms can work together to promote useful memory function.
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Affiliation(s)
- John Lisman
- Department of Biology, Brandeis University, Waltham, MA, USA
| | | | - Megha Sehgal
- Department of Neurobiology, Department of Psychology, Department of Psychiatry and Biobehavioral Sciences, Integrative Center for Learning and Memory, and Brain Research Institute, University of California, Los Angeles, Los Angeles, CA, USA
| | - Alcino J Silva
- Department of Biology, Brandeis University, Waltham, MA, USA.
- Department of Neurobiology, Department of Psychology, Department of Psychiatry and Biobehavioral Sciences, Integrative Center for Learning and Memory, and Brain Research Institute, University of California, Los Angeles, Los Angeles, CA, USA.
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Criteria for identifying the molecular basis of the engram (CaMKII, PKMzeta). Mol Brain 2017; 10:55. [PMID: 29187215 PMCID: PMC5707903 DOI: 10.1186/s13041-017-0337-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 11/16/2017] [Indexed: 11/22/2022] Open
Abstract
The engram refers to the molecular changes by which a memory is stored in the brain. Substantial evidence suggests that memory involves learning-dependent changes at synapses, a process termed long-term potentiation (LTP). Thus, understanding the storages process that underlies LTP may provide insight into how the engram is stored. LTP involves induction, maintenance (storage), and expression sub-processes; special tests are required to specifically reveal properties of the storage process. The strongest of these is the Erasure test in which a transiently applied agent that attacks a putative storage molecule may lead to persistent erasure of previously induced LTP/memory. Two major hypotheses have been proposed for LTP/memory storage: the CaMKII and PKM-zeta hypotheses. After discussing the tests that can be used to identify the engram (Necessity test, Saturation/Occlusion test, Erasure test), the status of these hypotheses is evaluated, based on the literature on LTP and memory-guided behavior. Review of the literature indicates that all three tests noted above support the CaMKII hypothesis when done at both the LTP level and at the behavioral level. Taken together, the results strongly suggest that the engram is stored by an LTP process in which CaMKII is a critical memory storage molecule.
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Juárez-Muñoz Y, Ramos-Languren LE, Escobar ML. CaMKII Requirement for in Vivo Insular Cortex LTP Maintenance and CTA Memory Persistence. Front Pharmacol 2017; 8:822. [PMID: 29184500 PMCID: PMC5694558 DOI: 10.3389/fphar.2017.00822] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 10/30/2017] [Indexed: 12/12/2022] Open
Abstract
Calcium-calmodulin/dependent protein kinase II (CaMKII) plays an essential role in LTP induction, but since it has the capacity to remain persistently activated even after the decay of external stimuli it has been proposed that it can also be necessary for LTP maintenance and therefore for memory persistence. It has been shown that basolateral amygdaloid nucleus (Bla) stimulation induces long-term potentiation (LTP) in the insular cortex (IC), a neocortical region implicated in the acquisition and retention of conditioned taste aversion (CTA). Our previous studies have demonstrated that induction of LTP in the Bla-IC pathway before CTA training increased the retention of this task. Although it is known that IC-LTP induction and CTA consolidation share similar molecular mechanisms, little is known about the molecular actors that underlie their maintenance. The purpose of the present study was to evaluate the role of CaMKII in the maintenance of in vivo Bla-IC LTP as well as in the persistence of CTA long-term memory (LTM). Our results show that acute microinfusion of myr-CaMKIINtide, a selective inhibitor of CaMKII, in the IC of adult rats during the late-phase of in vivo Bla-IC LTP blocked its maintenance. Moreover, the intracortical inhibition of CaMKII 24 h after CTA acquisition impairs CTA-LTM persistence. Together these results indicate that CaMKII is a central key component for the maintenance of neocortical synaptic plasticity as well as for persistence of CTA-LTM.
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Affiliation(s)
- Yectivani Juárez-Muñoz
- División de Investigación y Estudios de Posgrado, Facultad de Psicología, Universidad Nacional Autónoma de Mexico, Mexico City, Mexico
| | - Laura E Ramos-Languren
- División de Investigación y Estudios de Posgrado, Facultad de Psicología, Universidad Nacional Autónoma de Mexico, Mexico City, Mexico
| | - Martha L Escobar
- División de Investigación y Estudios de Posgrado, Facultad de Psicología, Universidad Nacional Autónoma de Mexico, Mexico City, Mexico
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