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Abstract
Maintaining wakefulness is associated with a progressive increase in the need for sleep. This phenomenon has been linked to changes in synaptic function. The synaptic adhesion molecule Neuroligin-1 (NLG1) controls the activity and synaptic localization of N-methyl-d-aspartate receptors, which activity is impaired by prolonged wakefulness. We here highlight that this pathway may underlie both the adverse effects of sleep loss on cognition and the subsequent changes in cortical synchrony. We found that the expression of specific Nlg1 transcript variants is changed by sleep deprivation in three mouse strains. These observations were associated with strain-specific changes in synaptic NLG1 protein content. Importantly, we showed that Nlg1 knockout mice are not able to sustain wakefulness and spend more time in nonrapid eye movement sleep than wild-type mice. These changes occurred with modifications in waking quality as exemplified by low theta/alpha activity during wakefulness and poor preference for social novelty, as well as altered delta synchrony during sleep. Finally, we identified a transcriptional pathway that could underlie the sleep/wake-dependent changes in Nlg1 expression and that involves clock transcription factors. We thus suggest that NLG1 is an element that contributes to the coupling of neuronal activity to sleep/wake regulation.
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152
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Sun C, Zhang L, Chen G. An unexpected role of neuroligin-2 in regulating KCC2 and GABA functional switch. Mol Brain 2013; 6:23. [PMID: 23663753 PMCID: PMC3661362 DOI: 10.1186/1756-6606-6-23] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Accepted: 05/08/2013] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND GABAA receptors are ligand-gated Cl- channels, and the intracellular Cl- concentration governs whether GABA function is excitatory or inhibitory. During early brain development, GABA undergoes functional switch from excitation to inhibition: GABA depolarizes immature neurons but hyperpolarizes mature neurons due to a developmental decrease of intracellular Cl- concentration. This GABA functional switch is mainly mediated by the up-regulation of KCC2, a potassium-chloride cotransporter that pumps Cl- outside neurons. However, the upstream factor that regulates KCC2 expression is unclear. RESULTS We report here that KCC2 is unexpectedly regulated by neuroligin-2 (NL2), a cell adhesion molecule specifically localized at GABAergic synapses. The expression of NL2 precedes that of KCC2 in early postnatal development. Upon knockdown of NL2, the expression level of KCC2 is significantly decreased, and GABA functional switch is significantly delayed during early development. Overexpression of shRNA-proof NL2 rescues both KCC2 reduction and delayed GABA functional switch induced by NL2 shRNAs. Moreover, NL2 appears to be required to maintain GABA inhibitory function even in mature neurons, because knockdown NL2 reverses GABA action to excitatory. Gramicidin-perforated patch clamp recordings confirm that NL2 directly regulates the GABA equilibrium potential. We further demonstrate that knockdown of NL2 decreases dendritic spines through down-regulating KCC2. CONCLUSIONS Our data suggest that in addition to its conventional role as a cell adhesion molecule to regulate GABAergic synaptogenesis, NL2 also regulates KCC2 to modulate GABA functional switch and even glutamatergic synapses. Therefore, NL2 may serve as a master regulator in balancing excitation and inhibition in the brain.
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Affiliation(s)
- Chicheng Sun
- Department of Biology, The Huck Institutes of Life Sciences, The Pennsylvania State University, University Park, PA 16802, USA
| | - Lei Zhang
- Department of Biology, The Huck Institutes of Life Sciences, The Pennsylvania State University, University Park, PA 16802, USA
| | - Gong Chen
- Department of Biology, The Huck Institutes of Life Sciences, The Pennsylvania State University, University Park, PA 16802, USA
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153
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Takasugi N, Sasaki T, Ebinuma I, Osawa S, Isshiki H, Takeo K, Tomita T, Iwatsubo T. FTY720/fingolimod, a sphingosine analogue, reduces amyloid-β production in neurons. PLoS One 2013; 8:e64050. [PMID: 23667698 PMCID: PMC3646787 DOI: 10.1371/journal.pone.0064050] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Accepted: 04/09/2013] [Indexed: 01/04/2023] Open
Abstract
Sphingosine-1-phosphate (S1P) is a pluripotent lipophilic mediator working as a ligand for G-protein coupled S1P receptors (S1PR), which is currently highlighted as a therapeutic target for autoimmune diseases including relapsing forms of multiple sclerosis. Sphingosine related compounds, FTY720 and KRP203 known as S1PR modulators, are phosphorylated by sphingosine kinase 2 (SphK2) to yield the active metabolites FTY720-P and KRP203-P, which work as functional antagonists for S1PRs. Here we report that FTY720 and KRP203 decreased production of Amyloid-β peptide (Aβ), a pathogenic proteins causative for Alzheimer disease (AD), in cultured neuronal cells. Pharmacological analyses suggested that the mechanism of FTY720-mediated Aβ decrease in cells was independent of known downstream signaling pathways of S1PRs. Unexpectedly, 6-days treatment of APP transgenic mice with FTY720 resulted in a decrease in Aβ40, but an increase in Aβ42 levels in brains. These results suggest that S1PR modulators are novel type of regulators for Aβ metabolisms that are active in vitro and in vivo.
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Affiliation(s)
- Nobumasa Takasugi
- Department of Neuropathology and Neuroscience, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
- Department of Neuropathology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, The University of Tokyo, Tokyo, Japan
| | - Tomoki Sasaki
- Department of Neuropathology and Neuroscience, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Ihori Ebinuma
- Department of Neuropathology and Neuroscience, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Satoko Osawa
- Department of Neuropathology and Neuroscience, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Hayato Isshiki
- Department of Neuropathology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, The University of Tokyo, Tokyo, Japan
| | - Koji Takeo
- Department of Neuropathology and Neuroscience, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Taisuke Tomita
- Department of Neuropathology and Neuroscience, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, The University of Tokyo, Tokyo, Japan
- * E-mail:
| | - Takeshi Iwatsubo
- Department of Neuropathology and Neuroscience, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
- Department of Neuropathology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, The University of Tokyo, Tokyo, Japan
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154
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Bang ML, Owczarek S. A Matter of Balance: Role of Neurexin and Neuroligin at the Synapse. Neurochem Res 2013; 38:1174-89. [DOI: 10.1007/s11064-013-1029-9] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Revised: 02/01/2013] [Accepted: 03/26/2013] [Indexed: 11/29/2022]
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155
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Liu DS, Loh KH, Lam SS, White KA, Ting AY. Imaging trans-cellular neurexin-neuroligin interactions by enzymatic probe ligation. PLoS One 2013; 8:e52823. [PMID: 23457442 PMCID: PMC3573046 DOI: 10.1371/journal.pone.0052823] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Accepted: 11/22/2012] [Indexed: 11/19/2022] Open
Abstract
Neurexin and neuroligin are transmembrane adhesion proteins that play an important role in organizing the neuronal synaptic cleft. Our lab previously reported a method for imaging the trans-synaptic binding of neurexin and neuroligin called BLINC (Biotin Labeling of INtercellular Contacts). In BLINC, biotin ligase (BirA) is fused to one protein while its 15-amino acid acceptor peptide substrate (AP) is fused to the binding partner. When the two fusion proteins interact across cellular junctions, BirA catalyzes the site-specific biotinylation of AP, which can be read out by staining with streptavidin-fluorophore conjugates. Here, we report that BLINC in neurons cannot be reproduced using the reporter constructs and labeling protocol previously described. We uncover the technical reasons for the lack of reproducibilty and then re-design the BLINC reporters and labeling protocol to achieve neurexin-neuroligin BLINC imaging in neuron cultures. In addition, we introduce a new method, based on lipoic acid ligase instead of biotin ligase, to image trans-cellular neurexin-neuroligin interactions in human embryonic kidney cells and in neuron cultures. This method, called ID-PRIME for Interaction-Dependent PRobe Incorporation Mediated by Enzymes, is more robust than BLINC due to higher surface expression of lipoic acid ligase fusion constructs, gives stronger and more localized labeling, and is more versatile than BLINC in terms of signal readout. ID-PRIME expands the toolkit of methods available to study trans-cellular protein-protein interactions in living systems.
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Affiliation(s)
- Daniel S. Liu
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Ken H. Loh
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Stephanie S. Lam
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Katharine A. White
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Alice Y. Ting
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
- * E-mail:
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156
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Lee SH, Shim J, Kaang BK. The role of cell adhesion molecules (CAMs) in defining synapse-specific function and plasticity. Anim Cells Syst (Seoul) 2013. [DOI: 10.1080/19768354.2013.769898] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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157
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158
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Takagi-Niidome S, Osawa S, Tomita T, Iwatsubo T. Inhibition of γ-Secretase Activity by a Monoclonal Antibody against the Extracellular Hydrophilic Loop of Presenilin 1. Biochemistry 2012; 52:61-9. [DOI: 10.1021/bi301252r] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Shizuka Takagi-Niidome
- Department of Neuropathology
and Neuroscience, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
| | - Satoko Osawa
- Department of Neuropathology
and Neuroscience, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
| | - Taisuke Tomita
- Department of Neuropathology
and Neuroscience, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
- Core Research for Evolutional
Science and Technology, Japan Science and Technology Agency, Tokyo 113-0033, Japan
| | - Takeshi Iwatsubo
- Department of Neuropathology
and Neuroscience, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
- Core Research for Evolutional
Science and Technology, Japan Science and Technology Agency, Tokyo 113-0033, Japan
- Department of Neuropathology,
Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
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