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Kasai H, Ziv NE, Okazaki H, Yagishita S, Toyoizumi T. Spine dynamics in the brain, mental disorders and artificial neural networks. Nat Rev Neurosci 2021; 22:407-422. [PMID: 34050339 DOI: 10.1038/s41583-021-00467-3] [Citation(s) in RCA: 68] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/14/2021] [Indexed: 12/15/2022]
Abstract
In the brain, most synapses are formed on minute protrusions known as dendritic spines. Unlike their artificial intelligence counterparts, spines are not merely tuneable memory elements: they also embody algorithms that implement the brain's ability to learn from experience and cope with new challenges. Importantly, they exhibit structural dynamics that depend on activity, excitatory input and inhibitory input (synaptic plasticity or 'extrinsic' dynamics) and dynamics independent of activity ('intrinsic' dynamics), both of which are subject to neuromodulatory influences and reinforcers such as dopamine. Here we succinctly review extrinsic and intrinsic dynamics, compare these with parallels in machine learning where they exist, describe the importance of intrinsic dynamics for memory management and adaptation, and speculate on how disruption of extrinsic and intrinsic dynamics may give rise to mental disorders. Throughout, we also highlight algorithmic features of spine dynamics that may be relevant to future artificial intelligence developments.
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Affiliation(s)
- Haruo Kasai
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Faculty of Medicine, The University of Tokyo, Tokyo, Japan. .,International Research Center for Neurointelligence (WPI-IRCN), UTIAS, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
| | - Noam E Ziv
- Technion Faculty of Medicine and Network Biology Research Labs, Technion City, Haifa, Israel
| | - Hitoshi Okazaki
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Faculty of Medicine, The University of Tokyo, Tokyo, Japan.,International Research Center for Neurointelligence (WPI-IRCN), UTIAS, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Sho Yagishita
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Faculty of Medicine, The University of Tokyo, Tokyo, Japan.,International Research Center for Neurointelligence (WPI-IRCN), UTIAS, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Taro Toyoizumi
- Laboratory for Neural Computation and Adaptation, RIKEN Center for Brain Science, Saitama, Japan.,Department of Mathematical Informatics, Graduate School of Information Science and Technology, The University of Tokyo, Tokyo, Japan
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2
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Gennaccaro L, Fuchs C, Loi M, Roncacè V, Trazzi S, Ait-Bali Y, Galvani G, Berardi AC, Medici G, Tassinari M, Ren E, Rimondini R, Giustetto M, Aicardi G, Ciani E. A GABA B receptor antagonist rescues functional and structural impairments in the perirhinal cortex of a mouse model of CDKL5 deficiency disorder. Neurobiol Dis 2021; 153:105304. [PMID: 33621640 DOI: 10.1016/j.nbd.2021.105304] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 02/16/2021] [Accepted: 02/17/2021] [Indexed: 11/25/2022] Open
Abstract
CDKL5 (cyclin-dependent kinase-like 5) deficiency disorder (CDD) is a severe neurodevelopmental encephalopathy characterized by early-onset epilepsy and intellectual disability. Studies in mouse models have linked CDKL5 deficiency to defects in neuronal maturation and synaptic plasticity, and disruption of the excitatory/inhibitory balance. Interestingly, increased density of both GABAergic synaptic terminals and parvalbumin inhibitory interneurons was recently observed in the primary visual cortex of Cdkl5 knockout (KO) mice, suggesting that excessive GABAergic transmission might contribute to the visual deficits characteristic of CDD. However, the functional relevance of cortical GABAergic circuits abnormalities in these mutant mice has not been investigated so far. Here we examined GABAergic circuits in the perirhinal cortex (PRC) of Cdkl5 KO mice, where we previously observed impaired long-term potentiation (LTP) associated with deficits in novel object recognition (NOR) memory. We found a higher number of GABAergic (VGAT)-immunopositive terminals in the PRC of Cdkl5 KO compared to wild-type mice, suggesting that increased inhibitory transmission might contribute to LTP impairment. Interestingly, while exposure of PRC slices to the GABAA receptor antagonist picrotoxin had no positive effects on LTP in Cdkl5 KO mice, the selective GABAB receptor antagonist CGP55845 restored LTP magnitude, suggesting that exaggerated GABAB receptor-mediated inhibition contributes to LTP impairment in mutants. Moreover, acute in vivo treatment with CGP55845 increased the number of PSD95 positive puncta as well as density and maturation of dendritic spines in PRC, and restored NOR memory in Cdkl5 KO mice. The present data show the efficacy of limiting excessive GABAB receptor-mediated signaling in improving synaptic plasticity and cognition in CDD mice.
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Affiliation(s)
- Laura Gennaccaro
- Department of Biomedical and Neuromotor Science, University of Bologna, Bologna, Italy
| | - Claudia Fuchs
- Department of Biomedical and Neuromotor Science, University of Bologna, Bologna, Italy
| | - Manuela Loi
- Department of Biomedical and Neuromotor Science, University of Bologna, Bologna, Italy
| | - Vincenzo Roncacè
- Department for Life Quality Studies, University of Bologna, Bologna, Italy
| | - Stefania Trazzi
- Department of Biomedical and Neuromotor Science, University of Bologna, Bologna, Italy
| | - Yassine Ait-Bali
- Department of Neuroscience "Rita Levi Montalcini", University of Turin, Turin, Italy
| | - Giuseppe Galvani
- Department of Biomedical and Neuromotor Science, University of Bologna, Bologna, Italy
| | | | - Giorgio Medici
- Department of Biomedical and Neuromotor Science, University of Bologna, Bologna, Italy
| | - Marianna Tassinari
- Department of Biomedical and Neuromotor Science, University of Bologna, Bologna, Italy
| | - Elisa Ren
- Department of Biomedical and Neuromotor Science, University of Bologna, Bologna, Italy
| | - Roberto Rimondini
- Department of Medical and Clinical Sciences, University of Bologna, Bologna, Italy
| | - Maurizio Giustetto
- Department of Neuroscience "Rita Levi Montalcini", University of Turin, Turin, Italy
| | - Giorgio Aicardi
- Department for Life Quality Studies, University of Bologna, Bologna, Italy.
| | - Elisabetta Ciani
- Department of Biomedical and Neuromotor Science, University of Bologna, Bologna, Italy.
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3
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Imaging of spine synapses using super-resolution microscopy. Anat Sci Int 2021; 96:343-358. [PMID: 33459976 DOI: 10.1007/s12565-021-00603-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Accepted: 01/04/2021] [Indexed: 12/17/2022]
Abstract
Neuronal circuits in the neocortex and hippocampus are essential for higher brain functions such as motor learning and spatial memory. In the mammalian forebrain, most excitatory synapses of pyramidal neurons are formed on spines, which are tiny protrusions extending from the dendritic shaft. The spine contains specialized molecular machinery that regulates synaptic transmission and plasticity. Spine size correlates with the efficacy of synaptic transmission, and spine morphology affects signal transduction at the post-synaptic compartment. Plasticity-related changes in the structural and molecular organization of spine synapses are thought to underlie the cellular basis of learning and memory. Recent advances in super-resolution microscopy have revealed the molecular mechanisms of the nanoscale synaptic structures regulating synaptic transmission and plasticity in living neurons, which are difficult to investigate using electron microscopy alone. In this review, we summarize recent advances in super-resolution imaging of spine synapses and discuss the implications of nanoscale structures in the regulation of synaptic function, learning, and memory.
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4
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Wiesner T, Bilodeau A, Bernatchez R, Deschênes A, Raulier B, De Koninck P, Lavoie-Cardinal F. Activity-Dependent Remodeling of Synaptic Protein Organization Revealed by High Throughput Analysis of STED Nanoscopy Images. Front Neural Circuits 2020; 14:57. [PMID: 33177994 PMCID: PMC7594516 DOI: 10.3389/fncir.2020.00057] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2020] [Accepted: 07/29/2020] [Indexed: 01/03/2023] Open
Abstract
The organization of proteins in the apposed nanodomains of pre- and postsynaptic compartments is thought to play a pivotal role in synaptic strength and plasticity. As such, the alignment between pre- and postsynaptic proteins may regulate, for example, the rate of presynaptic release or the strength of postsynaptic signaling. However, the analysis of these structures has mainly been restricted to subsets of synapses, providing a limited view of the diversity of synaptic protein cluster remodeling during synaptic plasticity. To characterize changes in the organization of synaptic nanodomains during synaptic plasticity over a large population of synapses, we combined STimulated Emission Depletion (STED) nanoscopy with a Python-based statistical object distance analysis (pySODA), in dissociated cultured hippocampal circuits exposed to treatments driving different forms of synaptic plasticity. The nanoscale organization, characterized in terms of coupling properties, of presynaptic (Bassoon, RIM1/2) and postsynaptic (PSD95, Homer1c) scaffold proteins was differently altered in response to plasticity-inducing stimuli. For the Bassoon - PSD95 pair, treatments driving synaptic potentiation caused an increase in their coupling probability, whereas a stimulus driving synaptic depression had an opposite effect. To enrich the characterization of the synaptic cluster remodeling at the population level, we applied unsupervised machine learning approaches to include selected morphological features into a multidimensional analysis. This combined analysis revealed a large diversity of synaptic protein cluster subtypes exhibiting differential activity-dependent remodeling, yet with common features depending on the expected direction of plasticity. The expanded palette of synaptic features revealed by our unbiased approach should provide a basis to further explore the widely diverse molecular mechanisms of synaptic plasticity.
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Affiliation(s)
| | | | | | | | | | - Paul De Koninck
- CERVO Brain Research Centre, Québec, QC, Canada.,Department of Biochemistry, Microbiology and Bioinformatics, Université Laval, Québec, QC, Canada
| | - Flavie Lavoie-Cardinal
- CERVO Brain Research Centre, Québec, QC, Canada.,Department of Psychiatry and Neuroscience, Université Laval, Québec, QC, Canada
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5
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Regional Brain Recovery from Acute Synaptic Injury in Simian Immunodeficiency Virus-Infected Rhesus Macaques Associates with Heme Oxygenase Isoform Expression. J Virol 2020; 94:JVI.01102-20. [PMID: 32669339 PMCID: PMC7495379 DOI: 10.1128/jvi.01102-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 07/10/2020] [Indexed: 12/21/2022] Open
Abstract
Brain injury induced by acute simian (or human) immunodeficiency virus infection may persist or spontaneously resolve in different brain regions. Identifying the host factor(s) that promotes spontaneous recovery from such injury may reveal targets for therapeutic drug strategies for promoting recovery from acute neuronal injury. The gradual recovery from such injury observed in many, but not all, brain regions in the rhesus macaque model is consistent with the possible existence of a therapeutic window of opportunity for intervening to promote recovery, even in those regions not showing spontaneous recovery. In persons living with human immunodeficiency virus infection, such neuroprotective treatments could ultimately be considered as adjuncts to the initiation of antiretroviral drug therapy. Brain injury occurs within days in simian immunodeficiency virus (SIV) or human immunodeficiency virus (HIV) infection, and some recovery may occur within weeks. Inflammation and oxidative stress associate with such injury, but what drives recovery is unknown. Chronic HIV infection associates with reduced brain frontal cortex expression of the antioxidant/anti-inflammatory enzyme heme oxygenase-1 (HO-1) and increased neuroinflammation in individuals with cognitive impairment. We hypothesized that acute regional brain injury and recovery associate with differences in regional brain HO-1 expression. Using SIV-infected rhesus macaques, we analyzed multiple brain regions through acute and chronic infection (90 days postinfection [dpi]) and quantified viral (SIV gag RNA), synaptic (PSD-95; synaptophysin), axonal (neurofilament/neurofilament light chain [NFL]), inflammatory, and antioxidant (enzymes, including heme oxygenase isoforms [HO-1, HO-2]) markers. PSD-95 was reduced in the brainstem, basal ganglia, neocortex, and cerebellum within 13 dpi, indicating acute synaptic injury throughout the brain. All areas except the brainstem recovered. Unchanged NFL was consistent with no acute axonal injury. SIV RNA expression was highest in the brainstem throughout infection, and it associated with neuroinflammation. Surprisingly, during the synaptic injury and recovery phases, HO-2, and not HO-1, progressively decreased in the brainstem. Thus, acute SIV synaptic injury occurs throughout the brain, with spontaneous recovery in regions other than the brainstem. Within the brainstem, the high SIV load and inflammation, along with reduction of HO-2, may impair recovery. In other brain regions, stable HO-2 expression, with or without increasing HO-1, may promote recovery. Our data support roles for heme oxygenase isoforms in modulating recovery from synaptic injury in SIV infection and suggest their therapeutic targeting for promoting neuronal recovery. IMPORTANCE Brain injury induced by acute simian (or human) immunodeficiency virus infection may persist or spontaneously resolve in different brain regions. Identifying the host factor(s) that promotes spontaneous recovery from such injury may reveal targets for therapeutic drug strategies for promoting recovery from acute neuronal injury. The gradual recovery from such injury observed in many, but not all, brain regions in the rhesus macaque model is consistent with the possible existence of a therapeutic window of opportunity for intervening to promote recovery, even in those regions not showing spontaneous recovery. In persons living with human immunodeficiency virus infection, such neuroprotective treatments could ultimately be considered as adjuncts to the initiation of antiretroviral drug therapy.
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Carriba P, Wyatt S, Davies AM. CD40L Reverse Signaling Influences Dendrite Spine Morphology and Expression of PSD-95 and Rho Small GTPases. Front Cell Dev Biol 2020; 8:254. [PMID: 32411702 PMCID: PMC7198883 DOI: 10.3389/fcell.2020.00254] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 03/25/2020] [Indexed: 11/13/2022] Open
Abstract
CD40-activated CD40L reverse signaling is a major physiological regulator of neural process growth from many kinds of developing neurons. Here we have investigated whether CD40L-reverse signaling also influences dendrite spine number and morphology in striatal medium spiny neurons (MSNs). Golgi preparations revealed no differences in the spine density, but because the dendrite arbors of MSNs were larger and branched in Cd40 -/- mice, the total number of spines was greater in Cd40 -/- mice. We also detected more mature spines compared with wild-type littermates. Western blot revealed that MSN cultures from Cd40 -/- mice had significantly less PSD-95 and there were changes in RhoA/B/C and Cdc42. Immunocytochemistry revealed that PSD-95 was clustered in spines in Cd40 -/- neurons compared with more diffuse labeling in Cd40 +/+ neurons. Activation of CD40L-reverse signaling with CD40-Fc prevented the changes observed in Cd40 -/- cultures. Our findings suggest that CD40L-reverse signaling influences dendrite spine morphology and related protein expression and distribution.
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Affiliation(s)
- Paulina Carriba
- Neuron Development, Neurosciences Department, School of Biosciences, Cardiff University, Cardiff, United Kingdom
| | - Sean Wyatt
- Neuron Development, Neurosciences Department, School of Biosciences, Cardiff University, Cardiff, United Kingdom
| | - Alun M Davies
- Neuron Development, Neurosciences Department, School of Biosciences, Cardiff University, Cardiff, United Kingdom
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7
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Lagache T, Grassart A, Dallongeville S, Faklaris O, Sauvonnet N, Dufour A, Danglot L, Olivo-Marin JC. Mapping molecular assemblies with fluorescence microscopy and object-based spatial statistics. Nat Commun 2018; 9:698. [PMID: 29449608 PMCID: PMC5814551 DOI: 10.1038/s41467-018-03053-x] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Accepted: 01/17/2018] [Indexed: 12/20/2022] Open
Abstract
Elucidating protein functions and molecular organisation requires to localise precisely single or aggregated molecules and analyse their spatial distributions. We develop a statistical method SODA (Statistical Object Distance Analysis) that uses either micro- or nanoscopy to significantly improve on standard co-localisation techniques. Our method considers cellular geometry and densities of molecules to provide statistical maps of isolated and associated (coupled) molecules. We use SODA with three-colour structured-illumination microscopy (SIM) images of hippocampal neurons, and statistically characterise spatial organisation of thousands of synapses. We show that presynaptic synapsin is arranged in asymmetric triangle with the 2 postsynaptic markers homer and PSD95, indicating a deeper localisation of homer. We then determine stoichiometry and distance between localisations of two synaptic vesicle proteins with 3D-STORM. These findings give insights into the protein organisation at the synapse, and prove the efficiency of SODA to quantitatively assess the geometry of molecular assemblies.
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Affiliation(s)
- Thibault Lagache
- Institut Pasteur, BioImage Analysis Unit. CNRS UMR 3691. 25 rue du Docteur Roux, 75724, Paris Cedex 15, France
- Department of Biological Sciences, Columbia University, New York, NY, USA
| | - Alexandre Grassart
- Institut Pasteur, Molecular Microbial Pathogenesis Unit. INSERM U1202. 28 rue du Docteur Roux, 75724, Paris Cedex 15, France
| | - Stéphane Dallongeville
- Institut Pasteur, BioImage Analysis Unit. CNRS UMR 3691. 25 rue du Docteur Roux, 75724, Paris Cedex 15, France
| | - Orestis Faklaris
- CNRS UMR7592, Institut Jacques Monod, Université Paris Diderot, 15 rue Hélène Brion, 75013, Paris, France
| | - Nathalie Sauvonnet
- Institut Pasteur, Molecular Microbial Pathogenesis Unit. INSERM U1202. 28 rue du Docteur Roux, 75724, Paris Cedex 15, France
| | - Alexandre Dufour
- Institut Pasteur, BioImage Analysis Unit. CNRS UMR 3691. 25 rue du Docteur Roux, 75724, Paris Cedex 15, France
| | - Lydia Danglot
- Inserm U894 Center for Psychiatry and Neuroscience, Team Membrane traffic in healthy and diseased brain, 102-108 rue de la Santé, 75014, Paris, France.
| | - Jean-Christophe Olivo-Marin
- Institut Pasteur, BioImage Analysis Unit. CNRS UMR 3691. 25 rue du Docteur Roux, 75724, Paris Cedex 15, France.
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8
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Gupta R. Self-crowding of AMPA receptors in the excitatory postsynaptic density can effectuate anomalous receptor sub-diffusion. PLoS Comput Biol 2018; 14:e1005984. [PMID: 29444074 PMCID: PMC5812565 DOI: 10.1371/journal.pcbi.1005984] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Accepted: 01/15/2018] [Indexed: 12/03/2022] Open
Abstract
AMPA receptors (AMPARs) and their associations with auxiliary transmembrane proteins are bulky structures with large steric-exclusion volumes. Hence, self-crowding of AMPARs, depending on the local density, may affect their lateral diffusion in the postsynaptic membrane as well as in the highly crowded postsynaptic density (PSD) at excitatory synapses. Earlier theoretical studies considered only the roles of transmembrane obstacles and the AMPAR-binding submembranous scaffold proteins in shaping receptor diffusion within PSD. Using lattice model of diffusion, the present study investigates the additional impacts of self-crowding on the anomalousity and effective diffusion coefficient (Deff) of AMPAR diffusion. A recursive algorithm for avoiding false self-blocking during diffusion simulation is also proposed. The findings suggest that high density of AMPARs in the obstacle-free membrane itself engenders strongly anomalous diffusion and severe decline in Deff. Adding transmembrane obstacles to the membrane accentuates the anomalousity arising from self-crowding due to the reduced free diffusion space. Contrarily, enhanced AMPAR-scaffold binding, either through increase in binding strength or scaffold density or both, ameliorates the anomalousity resulting from self-crowding. However, binding has differential impacts on Deff depending on the receptor density. Increase in binding causes consistent decrease in Deff for low and moderate receptor density. For high density, binding increases Deff as long as it reduces anomalousity associated with intense self-crowding. Given a sufficiently strong binding condition when diffusion acquires normal behavior, further increase in binding causes decrease in Deff. Supporting earlier experimental observations are mentioned and implications of present findings to the experimental observations on AMPAR diffusion are also drawn. The transmembrane AMPA receptors (AMPARs) prominently exhibit lateral diffusion in the postsynaptic membrane at excitatory synapses. Steric obstructions to AMPAR diffusion due to the crowd of other relatively static transmembrane proteins and binding of AMPARs to the submembranous scaffold proteins in the specialized region of postsynaptic density (PSD) are well known to retard receptor diffusion, which causes receptor trapping and accumulation within PSD. However, AMPARs are significantly bulky structures and may also obstruct their own diffusion paths in the presence of their high density. It is shown here that intense self-crowding of AMPARs may lead to highly obstructed and confined receptor diffusion even in the obstacle-free medium, and the presence of other obstacles further aggravates this effect. AMPAR-scaffold binding reduces confined diffusion arising from self-crowding and strong binding engenders normal diffusion even at high receptor density. However, it overall causes reduction in the effective diffusion coefficient of the receptor diffusion.
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Affiliation(s)
- Rahul Gupta
- School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi, India
- * E-mail:
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9
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Aittaleb M, Martinez-Pena Y Valenzuela I, Akaaboune M. Spatial distribution and molecular dynamics of dystrophin glycoprotein components at the neuromuscular junction in vivo. J Cell Sci 2017; 130:1752-1759. [PMID: 28364093 DOI: 10.1242/jcs.198358] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 03/29/2017] [Indexed: 11/20/2022] Open
Abstract
A bimolecular fluorescence complementation (BiFC) approach was used to study the molecular interactions between different components of the postsynaptic protein complex at the neuromuscular junction of living mice. We show that rapsyn forms complex with both α-dystrobrevin and α-syntrophin at the crests of junctional folds. The linkage of rapsyn to α-syntrophin and/or α-dystrobrevin is mediated by utrophin, a protein localized at acetylcholine receptor (AChR)-rich domains. In mice deficient in α-syntrophin, in which utrophin is no longer present at the synapse, rapsyn interaction with α-dystrobrevin was completely abolished. This interaction was completely restored when either utrophin or α-syntrophin was introduced into muscles deficient in α-syntrophin. However, in neuromuscular junctions deficient in α-dystrobrevin, in which utrophin is retained, complex formation between rapsyn and α-syntrophin was unaffected. Using fluorescence recovery after photobleaching, we found that α-syntrophin turnover is 5-7 times faster than that of AChRs, and loss of α-dystrobrevin has no effect on rapsyn and α-syntrophin half-life, whereas the half-life of AChR was significantly altered. Altogether, these results provide new insights into the spatial distribution of dystrophin glycoprotein components and their dynamics in living mice.
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Affiliation(s)
- Mohamed Aittaleb
- Department of Molecular, Cellular, and Developmental Biology, and Program in Neuroscience, University of Michigan, Ann Arbor, MI 48109, USA
| | - Isabel Martinez-Pena Y Valenzuela
- Department of Molecular, Cellular, and Developmental Biology, and Program in Neuroscience, University of Michigan, Ann Arbor, MI 48109, USA
| | - Mohammed Akaaboune
- Department of Molecular, Cellular, and Developmental Biology, and Program in Neuroscience, University of Michigan, Ann Arbor, MI 48109, USA .,College of Sciences and Engineering, Life Science Division, Hamad Bin Khalifa University, Doha, Qatar
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10
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OKABE S. Fluorescence imaging of synapse dynamics in normal circuit maturation and in developmental disorders. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2017; 93:483-497. [PMID: 28769018 PMCID: PMC5713177 DOI: 10.2183/pjab.93.029] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 05/26/2017] [Indexed: 06/07/2023]
Abstract
One of the most fundamental questions in neurobiology is how proper synaptic connections are established in the developing brain. Live-cell imaging of the synaptic structure and functional molecules can reveal the time course of synapse formation, molecular dynamics, and functional maturation. Using postsynaptic scaffolding proteins as a marker of synapse development, fluorescence time-lapse imaging revealed rapid formation of individual synapses that occurred within hours and their remodeling in culture preparations. In vivo two-photon excitation microscopy development enabled us to directly measure synapse turnover in living animals. In vivo synapse dynamics were suppressed in the adult rodent brain, but were maintained at a high level during the early postnatal period. This transition in synapse dynamics is biologically important and can be linked to the pathology of juvenile-onset psychiatric diseases. Indeed, the upregulation of synapse dynamics was observed in multiple mouse models of autism spectrum disorders. Fluorescence imaging of synapses provides new information regarding the physiology and pathology of neural circuit construction.
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Affiliation(s)
- Shigeo OKABE
- Department of Cellular Neurobiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
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11
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Dvorkin R, Ziv NE. Relative Contributions of Specific Activity Histories and Spontaneous Processes to Size Remodeling of Glutamatergic Synapses. PLoS Biol 2016; 14:e1002572. [PMID: 27776122 PMCID: PMC5077109 DOI: 10.1371/journal.pbio.1002572] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2016] [Accepted: 09/27/2016] [Indexed: 11/18/2022] Open
Abstract
The idea that synaptic properties are defined by specific pre- and postsynaptic activity histories is one of the oldest and most influential tenets of contemporary neuroscience. Recent studies also indicate, however, that synaptic properties often change spontaneously, even in the absence of specific activity patterns or any activity whatsoever. What, then, are the relative contributions of activity history-dependent and activity history-independent processes to changes synapses undergo? To compare the relative contributions of these processes, we imaged, in spontaneously active networks of cortical neurons, glutamatergic synapses formed between the same axons and neurons or dendrites under the assumption that their similar activity histories should result in similar size changes over timescales of days. The size covariance of such commonly innervated (CI) synapses was then compared to that of synapses formed by different axons (non-CI synapses) that differed in their activity histories. We found that the size covariance of CI synapses was greater than that of non-CI synapses; yet overall size covariance of CI synapses was rather modest. Moreover, momentary and time-averaged sizes of CI synapses correlated rather poorly, in perfect agreement with published electron microscopy-based measurements of mouse cortex synapses. A conservative estimate suggested that ~40% of the observed size remodeling was attributable to specific activity histories, whereas ~10% and ~50% were attributable to cell-wide and spontaneous, synapse-autonomous processes, respectively. These findings demonstrate that histories of naturally occurring activity patterns can direct glutamatergic synapse remodeling but also suggest that the contributions of spontaneous, possibly stochastic, processes are at least as great.
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Affiliation(s)
- Roman Dvorkin
- Technion Faculty of Medicine, Network Biology Research Laboratories, Lorry Lokey Center for Life Sciences and Engineering, Technion, Haifa, Israel
| | - Noam E Ziv
- Technion Faculty of Medicine, Network Biology Research Laboratories, Lorry Lokey Center for Life Sciences and Engineering, Technion, Haifa, Israel.,Rappaport Family Institute for Research in the Medical Sciences, Haifa, Israel
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12
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Zimmerman SP, Hallett RA, Bourke AM, Bear JE, Kennedy MJ, Kuhlman B. Tuning the Binding Affinities and Reversion Kinetics of a Light Inducible Dimer Allows Control of Transmembrane Protein Localization. Biochemistry 2016; 55:5264-71. [PMID: 27529180 DOI: 10.1021/acs.biochem.6b00529] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Inducible dimers are powerful tools for controlling biological processes through colocalizing signaling molecules. To be effective, an inducible system should have a dissociation constant in the "off" state that is greater (i.e., weaker affinity) than the concentrations of the molecules that are being controlled, and in the "on" state a dissociation constant that is less (i.e., stronger affinity) than the relevant protein concentrations. Here, we reengineer the interaction between the light inducible dimer, iLID, and its binding partner SspB, to better control proteins present at high effective concentrations (5-100 μM). iLID contains a light-oxygen-voltage (LOV) domain that undergoes a conformational change upon activation with blue light and exposes a peptide motif, ssrA, that binds to SspB. The new variant of the dimer system contains a single SspB point mutation (A58V), and displays a 42-fold change in binding affinity when activated with blue light (from 3 ± 2 μM to 125 ± 40 μM) and allows for light-activated colocalization of transmembrane proteins in neurons, where a higher affinity switch (0.8-47 μM) was less effective because more colocalization was seen in the dark. Additionally, with a point mutation in the LOV domain (N414L), we lengthened the reversion half-life of iLID. This expanded suite of light induced dimers increases the variety of cellular pathways that can be targeted with light.
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Affiliation(s)
| | | | - Ashley M Bourke
- Department of Pharmacology, University of Colorado School of Medicine , Aurora, Colorado 80045, United States
| | | | - Matthew J Kennedy
- Department of Pharmacology, University of Colorado School of Medicine , Aurora, Colorado 80045, United States
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13
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Abbas AK. Protein Synthesis Inhibitors Did Not Interfere with Long-Term Depression Induced either Electrically in Juvenile Rats or Chemically in Middle-Aged Rats. PLoS One 2016; 11:e0161270. [PMID: 27517693 PMCID: PMC4982604 DOI: 10.1371/journal.pone.0161270] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 07/02/2016] [Indexed: 11/26/2022] Open
Abstract
In testing the hypothesis that long-term potentiation (LTP) maintenance depends on triggered protein synthesis, we found no effect of protein synthesis inhibitors (PSIs) on LTP stabilization. Similarly, some studies reported a lack of effect of PSIs on long-term depression (LTD); the lack of effect on LTD has been suggested to be resulting from the short time recordings. If this proposal were true, LTD might exhibit sensitivity to PSIs when the recording intervals were enough long. We firstly induced LTD by a standard protocol involving low frequency stimulation, which is suitable for eliciting NMDAR-LTD in CA1 area of hippocampal slices obtained from juvenile Sprague-Dawley rats. This LTD was persistent for intervals in range of 8–10 h. Treating slices with anisomycin, however, did not interfere with the magnitude and persistence of this form of LTD. The failure of anisomycin to block synaptic-LTD might be relied on the age of animal, the type of protein synthesis inhibitors and/or the inducing protocol. To verify whether those variables altogether were determinant, NMDA or DHPG was used to chemically elicit LTD recorded up to 10 h on hippocampal slices obtained from middle-aged rats. In either form of LTD, cycloheximide did not interfere with LTD stabilization. Furthermore, DHPG application did show an increase in the global protein synthesis as assayed by radiolabeled methodology indicating that though triggered protein synthesis can occur but not necessarily required for LTD expression. The findings confirm that stabilized LTD in either juvenile, or middle-aged rats can be independent of triggered protein synthesis. Although the processes responsible for the independence of LTD stabilization on the triggered protein synthesis are not yet defined, these findings raise the possibility that de novo protein synthesis is not universally necessary.
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Affiliation(s)
- Abdul-Karim Abbas
- Institute of Neuroscience and Physiology, University of Gothenburg, Box 432, SE-40530, Gothenburg, Sweden
- * E-mail:
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14
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Glebov OO, Cox S, Humphreys L, Burrone J. Neuronal activity controls transsynaptic geometry. Sci Rep 2016; 6:22703. [PMID: 26951792 PMCID: PMC4782104 DOI: 10.1038/srep22703] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 02/09/2016] [Indexed: 11/13/2022] Open
Abstract
The neuronal synapse is comprised of several distinct zones, including presynaptic vesicle zone (SVZ), active zone (AZ) and postsynaptic density (PSD). While correct relative positioning of these zones is believed to be essential for synaptic function, the mechanisms controlling their mutual localization remain unexplored. Here, we employ high-throughput quantitative confocal imaging, super-resolution and electron microscopy to visualize organization of synaptic subdomains in hippocampal neurons. Silencing of neuronal activity leads to reversible reorganization of the synaptic geometry, resulting in a increased overlap between immunostained AZ and PSD markers; in contrast, the SVZ-AZ spatial coupling is decreased. Bayesian blinking and bleaching (3B) reconstruction reveals that the distance between the AZ-PSD distance is decreased by 30 nm, while electron microscopy shows that the width of the synaptic cleft is decreased by 1.1 nm. Our findings show that multiple aspects of synaptic geometry are dynamically controlled by neuronal activity and suggest mutual repositioning of synaptic components as a potential novel mechanism contributing to the homeostatic forms of synaptic plasticity.
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Affiliation(s)
- Oleg O. Glebov
- Wolfson Centre for Age-Related Diseases, King’s College London, London SE1 1UL, UK
- Department of Developmental Neurobiology, King’s College London, London SE1 1UL, UK
| | - Susan Cox
- Randall Division of Cell and Molecular Biophysics, King’s College London, London SE1 1UL, UK
| | - Lawrence Humphreys
- Department of Developmental Neurobiology, King’s College London, London SE1 1UL, UK
| | - Juan Burrone
- Department of Developmental Neurobiology, King’s College London, London SE1 1UL, UK
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15
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Shisa6 traps AMPA receptors at postsynaptic sites and prevents their desensitization during synaptic activity. Nat Commun 2016; 7:10682. [PMID: 26931375 PMCID: PMC4778035 DOI: 10.1038/ncomms10682] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2015] [Accepted: 01/11/2016] [Indexed: 11/08/2022] Open
Abstract
Trafficking and biophysical properties of AMPA receptors (AMPARs) in the brain depend on interactions with associated proteins. We identify Shisa6, a single transmembrane protein, as a stable and directly interacting bona fide AMPAR auxiliary subunit. Shisa6 is enriched at hippocampal postsynaptic membranes and co-localizes with AMPARs. The Shisa6 C-terminus harbours a PDZ domain ligand that binds to PSD-95, constraining mobility of AMPARs in the plasma membrane and confining them to postsynaptic densities. Shisa6 expressed in HEK293 cells alters GluA1- and GluA2-mediated currents by prolonging decay times and decreasing the extent of AMPAR desensitization, while slowing the rate of recovery from desensitization. Using gene deletion, we show that Shisa6 increases rise and decay times of hippocampal CA1 miniature excitatory postsynaptic currents (mEPSCs). Shisa6-containing AMPARs show prominent sustained currents, indicating protection from full desensitization. Accordingly, Shisa6 prevents synaptically trapped AMPARs from depression at high-frequency synaptic transmission. Auxiliary AMPA receptor subunits can affect gating and surface mobility. Here the authors show that Shisa6 traps AMPA receptors at postsynaptic sites via PSD-95, and keeps them in an activated state in the presence of glutamate, preventing full desensitization and consequently synaptic depression.
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16
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Guo W, Ceolin L, Collins KA, Perroy J, Huber KM. Elevated CaMKIIα and Hyperphosphorylation of Homer Mediate Circuit Dysfunction in a Fragile X Syndrome Mouse Model. Cell Rep 2015; 13:2297-311. [PMID: 26670047 DOI: 10.1016/j.celrep.2015.11.013] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Revised: 09/09/2015] [Accepted: 11/02/2015] [Indexed: 10/22/2022] Open
Abstract
Abnormal metabotropic glutamate receptor 5 (mGluR5) function, as a result of disrupted scaffolding with its binding partner Homer, contributes to the pathophysiology of fragile X syndrome, a common inherited form of intellectual disability and autism caused by mutations in Fmr1. How loss of Fmr1 disrupts mGluR5-Homer scaffolds is unknown, and little is known about the dynamic regulation of mGluR5-Homer scaffolds in wild-type neurons. Here, we demonstrate that brief (minutes-long) elevations in neural activity cause CaMKIIα-mediated phosphorylation of long Homer proteins and dissociation from mGluR5 at synapses. In Fmr1 knockout (KO) cortex, Homers are hyperphosphorylated as a result of elevated CaMKIIα protein. Genetic or pharmacological inhibition of CaMKIIα or replacement of Homers with dephosphomimetics restores mGluR5-Homer scaffolds and multiple Fmr1 KO phenotypes, including circuit hyperexcitability and/or seizures. This work links translational control of an FMRP target mRNA, CaMKIIα, to the molecular-, cellular-, and circuit-level brain dysfunction in a complex neurodevelopmental disorder.
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Affiliation(s)
- Weirui Guo
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Laura Ceolin
- CNRS, UMR-5203, Institut de Génomique Fonctionnelle, 34000 Montpellier, France; INSERM, U1191, 34000 Montpellier, France; Universites de Montpellier 1 & 2, UMR-5203, 34000 Montpellier, France
| | - Katie A Collins
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Julie Perroy
- CNRS, UMR-5203, Institut de Génomique Fonctionnelle, 34000 Montpellier, France; INSERM, U1191, 34000 Montpellier, France; Universites de Montpellier 1 & 2, UMR-5203, 34000 Montpellier, France
| | - Kimberly M Huber
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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17
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Matlashov ME, Bogdanova YA, Ermakova GV, Mishina NM, Ermakova YG, Nikitin ES, Balaban PM, Okabe S, Lukyanov S, Enikolopov G, Zaraisky AG, Belousov VV. Fluorescent ratiometric pH indicator SypHer2: Applications in neuroscience and regenerative biology. Biochim Biophys Acta Gen Subj 2015; 1850:2318-28. [PMID: 26259819 DOI: 10.1016/j.bbagen.2015.08.002] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Revised: 07/13/2015] [Accepted: 08/04/2015] [Indexed: 10/23/2022]
Abstract
BACKGROUND SypHer is a genetically encoded fluorescent pH-indicator with a ratiometric readout, suitable for measuring fast intracellular pH shifts. However, the relatively low brightness of the indicator limits its use. METHODS Here we designed a new version of pH-sensor called SypHer-2, which has up to three times brighter fluorescence in cultured mammalian cells compared to the SypHer. RESULTS Using the new indicator we registered activity-associated pH oscillations in neuronal cell culture. We observed prominent transient neuronal cytoplasm acidification that occurs in parallel with calcium entry. Furthermore, we monitored pH in presynaptic and postsynaptic termini by targeting SypHer-2 directly to these compartments and revealed marked differences in pH dynamics between synaptic boutons and dendritic spines. Finally, we were able to reveal for the first time the intracellular pH drop that occurs within an extended region of the amputated tail of the Xenopus laevis tadpole before it begins to regenerate. CONCLUSIONS SypHer2 is suitable for quantitative monitoring of pH in biological systems of different scales, from small cellular subcompartments to animal tissues in vivo. GENERAL SIGNIFICANCE The new pH-sensor will help to investigate pH-dependent processes in both in vitro and in vivo studies.
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Affiliation(s)
- Mikhail E Matlashov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, 117997 Moscow, Russia; Nizhny Novgorod State Medical Academy, 603005 Nizhny Novgorod, Russia
| | - Yulia A Bogdanova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, 117997 Moscow, Russia; Faculty of Biology, Moscow State University, 119991 Moscow, Russia
| | - Galina V Ermakova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, 117997 Moscow, Russia
| | - Natalia M Mishina
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, 117997 Moscow, Russia; Nizhny Novgorod State Medical Academy, 603005 Nizhny Novgorod, Russia
| | - Yulia G Ermakova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, 117997 Moscow, Russia
| | - Evgeny S Nikitin
- Institute of Higher Nervous Activity and Neurophysiology, 117485 Moscow, Russia
| | - Pavel M Balaban
- Institute of Higher Nervous Activity and Neurophysiology, 117485 Moscow, Russia
| | - Shigeo Okabe
- Department of Cellular Neurobiology, Graduate School of Medicine, University of Tokyo, Tokyo 113-0033, Japan
| | - Sergey Lukyanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, 117997 Moscow, Russia; Nizhny Novgorod State Medical Academy, 603005 Nizhny Novgorod, Russia
| | - Grigori Enikolopov
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA; Department of Anesthesiology, Stony Brook School of Medicine, Stony Brook, NY 11794, USA; Center for Developmental Genetics, Stony Brook University, Stony Brook, NY 11794, USA; NBIC, Moscow Institute of Physics and Technology, 123182 Moscow, Russia.
| | - Andrey G Zaraisky
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, 117997 Moscow, Russia.
| | - Vsevolod V Belousov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, 117997 Moscow, Russia; Nizhny Novgorod State Medical Academy, 603005 Nizhny Novgorod, Russia.
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18
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Abstract
The development of methods to follow the dynamics of synaptic molecules in living neurons has radically altered our view of the synapse, from that of a generally static structure to that of a dynamic molecular assembly at steady state. This view holds not only for relatively labile synaptic components, such as synaptic vesicles, cytoskeletal elements, and neurotransmitter receptors, but also for the numerous synaptic molecules known as scaffolding molecules, a generic name for a diverse class of molecules that organize synaptic function in time and space. Recent studies reveal that these molecules, which confer a degree of stability to synaptic assemblies over time scales of hours and days, are themselves subject to significant dynamics. Furthermore, these dynamics are probably not without effect; wherever studied, these seem to be associated with spontaneous changes in scaffold molecule content, synaptic size, and possibly synaptic function. This review describes the dynamics exhibited by synaptic scaffold molecules, their typical time scales, and the potential implications to our understanding of synaptic function.
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Affiliation(s)
- Noam E. Ziv
- Technion–Israel Institute of Technology, Haifa, Israel
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19
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Tao-Cheng JH, Thein S, Yang Y, Reese TS, Gallant PE. Homer is concentrated at the postsynaptic density and does not redistribute after acute synaptic stimulation. Neuroscience 2014; 266:80-90. [PMID: 24530450 DOI: 10.1016/j.neuroscience.2014.01.066] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 01/30/2014] [Accepted: 01/31/2014] [Indexed: 10/25/2022]
Abstract
Homer is a postsynaptic density (PSD) scaffold protein that is involved in synaptic plasticity, calcium signaling and neurological disorders. Here, we use pre-embedding immunogold electron microscopy to illustrate the differential localization of three Homer gene products (Homer 1, 2, and 3) in different regions of the mouse brain. In cross-sectioned PSDs, Homer occupies a layer ∼30-100nm from the postsynaptic membrane lying just beyond the dense material that defines the PSD core (∼30-nm-thick). Homer is evenly distributed within the PSD area along the lateral axis, but not at the peri-PSD locations within 60nm from the edge of the PSD, where type I-metabotropic glutamate receptors (mGluR1 and 5) are concentrated. This distribution of Homer matches that of Shank, another major PSD scaffold protein, but differs from those of other two major binding partners of Homer, type I mGluR and IP3 receptors. Many PSD proteins rapidly redistribute upon acute (2min) stimulation. To determine whether Homer distribution is affected by acute stimulation, we examined its distribution in dissociated hippocampal cultures under different conditions. Both the pattern and density of label for Homer 1, the isoform that is ubiquitous in hippocampus, remained unchanged under high K(+) depolarization (90mM for 2-5min), N-methyl-d-asparic acid (NMDA) treatment (50μM for 2min), and calcium-free conditions (EGTA at 1mM for 2min). In contrast, Shank and calcium/calmodulin-dependent kinase II (CaMKII) accumulate at the PSD upon NMDA treatment, and CaMKII is excluded from the PSD complex under low calcium conditions.
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Affiliation(s)
- J-H Tao-Cheng
- EM Facility, NINDS, NIH, Bethesda, MD, United States.
| | - S Thein
- Laboratory of Neurobiology, NINDS, NIH, Bethesda, MD, United States
| | - Y Yang
- Laboratory of Neurobiology, NINDS, NIH, Bethesda, MD, United States
| | - T S Reese
- Laboratory of Neurobiology, NINDS, NIH, Bethesda, MD, United States
| | - P E Gallant
- Laboratory of Neurobiology, NINDS, NIH, Bethesda, MD, United States
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20
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Abstract
Like all cells, neurons are made of proteins that have characteristic synthesis and degradation profiles. Unlike other cells, however, neurons have a unique multipolar architecture that makes ∼10,000 synaptic contacts with other neurons. Both the stability and modifiability of the neuronal proteome are crucial for its information-processing, storage and plastic properties. The cell biological mechanisms that synthesize, modify, deliver and degrade dendritic and synaptic proteins are not well understood but appear to reflect unique solutions adapted to the particular morphology of neurons.
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21
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Giannone G, Mondin M, Grillo-Bosch D, Tessier B, Saint-Michel E, Czöndör K, Sainlos M, Choquet D, Thoumine O. Neurexin-1β binding to neuroligin-1 triggers the preferential recruitment of PSD-95 versus gephyrin through tyrosine phosphorylation of neuroligin-1. Cell Rep 2013; 3:1996-2007. [PMID: 23770246 DOI: 10.1016/j.celrep.2013.05.013] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Revised: 03/08/2013] [Accepted: 05/09/2013] [Indexed: 11/28/2022] Open
Abstract
Adhesion between neurexin-1β (Nrx1β) and neuroligin-1 (Nlg1) induces early recruitment of the postsynaptic density protein 95 (PSD-95) scaffold; however, the associated signaling mechanisms are unknown. To dissociate the effects of ligand binding and receptor multimerization, we compared conditions in which Nlg1 in neurons was bound to Nrx1β or nonactivating HA antibodies. Time-lapse imaging, fluorescence recovery after photobleaching, and single-particle tracking demonstrated that in addition to aggregating Nlg1, Nrx1β binding stimulates the interaction between Nlg1 and PSD-95. Phosphotyrosine immunoblots and pull-down of gephyrin by Nlg1 peptides in vitro showed that Nlg1 can be phosphorylated at a unique tyrosine (Y782), preventing gephyrin binding. Expression of Nlg1 point mutants in neurons indicated that Y782 phosphorylation controls the preferential binding of Nlg1 to PSD-95 versus gephyrin, and accordingly the formation of inhibitory and excitatory synapses. We propose that ligand-induced changes in the Nlg1 phosphotyrosine level control the balance between excitatory and inhibitory scaffold assembly during synapse formation and stabilization.
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Affiliation(s)
- Grégory Giannone
- University Bordeaux, Interdisciplinary Institute for Neuroscience, UMR 5297, F-33000 Bordeaux, France
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22
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23
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Luo P, Li X, Fei Z, Poon W. Scaffold protein Homer 1: implications for neurological diseases. Neurochem Int 2012; 61:731-8. [PMID: 22749857 DOI: 10.1016/j.neuint.2012.06.014] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Revised: 06/16/2012] [Accepted: 06/20/2012] [Indexed: 11/17/2022]
Abstract
Homer proteins are commonly known as scaffold proteins at postsynaptic density. Homer 1 is a widely studied member of the Homer protein family, comprising both synaptic structure and mediating postsynaptic signaling transduction. Both an immediate-early gene encoding a Homer 1 variant and a constitutively expressed Homer 1 variant regulate receptor clustering and trafficking, intracellular calcium homeostasis, and intracellular molecule complex formation. Substantial preclinical investigations have implicated that each of these Homer 1 variants are associated with the etiology of many neurological diseases, such as pain, mental retardation syndromes, Alzheimer's disease, schizophrenia, drug-induced addiction, and traumatic brain injury.
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Affiliation(s)
- Peng Luo
- Department of Neurosurgery, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, PR China
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24
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Kawabata I, Kashiwagi Y, Obashi K, Ohkura M, Nakai J, Wynshaw-Boris A, Yanagawa Y, Okabe S. LIS1-dependent retrograde translocation of excitatory synapses in developing interneuron dendrites. Nat Commun 2012; 3:722. [PMID: 22395613 PMCID: PMC3316883 DOI: 10.1038/ncomms1736] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2011] [Accepted: 02/07/2012] [Indexed: 11/30/2022] Open
Abstract
Synaptic remodelling coordinated with dendritic growth is essential for proper development of neural connections. After establishment of synaptic contacts, synaptic junctions are thought to become stationary and provide fixed anchoring points for further dendritic growth. However, the possibility of active translocation of synapses along dendritic protrusions, to guide the proper arrangement of synaptic distribution, has not yet been fully investigated. Here we show that immature dendrites of γ-aminobutyric acid-positive interneurons form long protrusions and that these protrusions serve as conduits for retrograde translocation of synaptic contacts to the parental dendrites. This translocation process is dependent on microtubules and the activity of LIS1, an essential regulator of dynein-mediated motility. Suppression of this retrograde translocation results in disorganized synaptic patterns on interneuron dendrites. Taken together, these findings suggest the existence of an active microtubule-dependent mechanism for synaptic translocation that helps in the establishment of proper synaptic distribution on dendrites. Maturation of synaptic junctions is important for proper neuronal connections. Using live cell imaging, Okabe et al. show that interneuron dendrites extend filopodia-like projections and use microtubule-dependent retrograde transport to guide proper synaptic distribution on dendrites.
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Affiliation(s)
- Izumi Kawabata
- Department of Cellular Neurobiology, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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25
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Okabe S. Molecular Dynamics of the Excitatory Synapse. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 970:131-52. [DOI: 10.1007/978-3-7091-0932-8_6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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26
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Roselli F, Livrea P, Almeida OFX. CDK5 is essential for soluble amyloid β-induced degradation of GKAP and remodeling of the synaptic actin cytoskeleton. PLoS One 2011; 6:e23097. [PMID: 21829588 PMCID: PMC3146526 DOI: 10.1371/journal.pone.0023097] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Accepted: 07/11/2011] [Indexed: 01/01/2023] Open
Abstract
The early stages of Alzheimer's disease are marked by synaptic dysfunction and loss. This process results from the disassembly and degradation of synaptic components, in particular of scaffolding proteins that compose the post-synaptic density (PSD), namely PSD95, Homer and Shank. Here we investigated in rat frontal cortex dissociated culture the mechanisms involved in the downregulation of GKAP (SAPAP1), which links the PSD95 complex to the Shank complex and cytoskeletal structures within the PSD. We show that Aβ causes the rapid loss of GKAP from synapses through a pathway that critically requires cdk5 activity, and is set in motion by NMDAR activity and Ca(2+) influx. We show that GKAP is a direct substrate of cdk5 and that its phosphorylation results in polyubiquitination and proteasomal degradation of GKAP and remodeling (collapse) of the synaptic actin cytoskeleton; the latter effect is abolished in neurons expressing GKAP mutants that are resistant to phosphorylation by cdk5. Given that cdk5 also regulates degradation of PSD95, these results underscore the central position of cdk5 in mediating Aβ-induced PSD disassembly and synapse loss.
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Affiliation(s)
- Francesco Roselli
- Neuroadaptation Group, Max Planck Institute of Psychiatry, Munich, Germany
- Department of Neurological and Psychiatric Sciences, University of Bari, Bari, Italy
- * E-mail: (FR); (OFXA)
| | - Paolo Livrea
- Department of Neurological and Psychiatric Sciences, University of Bari, Bari, Italy
| | - Osborne F. X. Almeida
- Neuroadaptation Group, Max Planck Institute of Psychiatry, Munich, Germany
- * E-mail: (FR); (OFXA)
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27
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Soria Van Hoeve JS, Borst JGG. Delayed appearance of the scaffolding proteins PSD-95 and Homer-1 at the developing rat calyx of Held synapse. J Comp Neurol 2011; 518:4581-90. [PMID: 20886623 DOI: 10.1002/cne.22479] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The calyx of Held synapse is a giant axosomatic synapse that acts as a fast relay in the sound localization circuit of the brainstem. In rodents it forms within a relatively brief period starting around the second postnatal day (P2). The relative timing of the formation of its pre- and the postsynaptic compartment are not yet known. By means of fluorescent immunohistochemistry in neonatal rats we therefore compared the developmental expression patterns of the vesicular glutamate transporter (VGLUT)-1 and the postsynaptic density scaffolding proteins Homer-1 and PSD-95 in the medial nucleus of the trapezoid body (MNTB). Before its formation, colocalized punctate staining of VGLUT-1 and Homer-1 or PSD-95 was observed on principal neurons, in agreement with earlier work showing that they are already innervated by fibers from the cochlear nucleus before the calyx forms. The expression of VGLUT-1 clusters within the nascent calyx of Held synapse preceded the expression of Homer-1 and PSD-95 clusters, as indicated by the presence of principal neurons with only a large contiguous cluster (LCC) of VGLUT-1 at P2-3, whereas no neurons with only an LCC for Homer-1 or PSD-95 were seen. At P3 the first principal neurons with both a pre- and a postsynaptic LCC were observed, and at P12 all principal neurons had both a pre- and a postsynaptic LCC. The relatively late appearance of Homer-1 and PSD-95 within the developing calyx of Held synapse suggests that they play a role in its stabilization and the recruitment of additional receptors to its postsynaptic density.
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Affiliation(s)
- John S Soria Van Hoeve
- Department of Neuroscience, Erasmus MC, University Medical Center Rotterdam, 3015 GE Rotterdam, The Netherlands
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28
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Structural dynamics of dendritic spines in memory and cognition. Trends Neurosci 2010; 33:121-9. [PMID: 20138375 DOI: 10.1016/j.tins.2010.01.001] [Citation(s) in RCA: 595] [Impact Index Per Article: 42.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2009] [Revised: 01/07/2010] [Accepted: 01/08/2010] [Indexed: 01/07/2023]
Abstract
Recent studies show that dendritic spines are dynamic structures. Their rapid creation, destruction and shape-changing are essential for short- and long-term plasticity at excitatory synapses on pyramidal neurons in the cerebral cortex. The onset of long-term potentiation, spine-volume growth and an increase in receptor trafficking are coincident, enabling a 'functional readout' of spine structure that links the age, size, strength and lifetime of a synapse. Spine dynamics are also implicated in long-term memory and cognition: intrinsic fluctuations in volume can explain synapse maintenance over long periods, and rapid, activity-triggered plasticity can relate directly to cognitive processes. Thus, spine dynamics are cellular phenomena with important implications for cognition and memory. Furthermore, impaired spine dynamics can cause psychiatric and neurodevelopmental disorders.
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29
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Goswami C, Rademacher N, Smalla KH, Kalscheuer V, Ropers HH, Gundelfinger ED, Hucho T. TRPV1 acts as a synaptic protein and regulates vesicle recycling. J Cell Sci 2010; 123:2045-57. [PMID: 20483957 DOI: 10.1242/jcs.065144] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Electrophysiological studies demonstrate that transient receptor potential vanilloid subtype 1 (TRPV1) is involved in neuronal transmission. Although it is expressed in the peripheral as well as the central nervous system, the questions remain whether TRPV1 is present in synaptic structures and whether it is involved in synaptic processes. In the present study we gathered evidence that TRPV1 can be detected in spines of cortical neurons, that it colocalizes with both pre- and postsynaptic proteins, and that it regulates spine morphology. Moreover, TRPV1 is also present in biochemically prepared synaptosomes endogenously. In F11 cells, a cell line derived from dorsal-root-ganglion neurons, TRPV1 is enriched in the tips of elongated filopodia and also at sites of cell-cell contact. In addition, we also detected TRPV1 in synaptic transport vesicles, and in transport packets within filopodia and neurites. Using FM4-64 dye, we demonstrate that recycling and/or fusion of these vesicles can be rapidly modulated by TRPV1 activation, leading to rapid reorganization of filopodial structure. These data suggest that TRPV1 is involved in processes such as neuronal network formation, synapse modulation and release of synaptic transmitters.
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Affiliation(s)
- Chandan Goswami
- Signal Transduction in Pain and Mental Retardation, Department for Molecular Human Genetics, Max-Planck Institute for Molecular Genetics, Berlin, Germany.
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Santamaria F, Gonzalez J, Augustine GJ, Raghavachari S. Quantifying the effects of elastic collisions and non-covalent binding on glutamate receptor trafficking in the post-synaptic density. PLoS Comput Biol 2010; 6:e1000780. [PMID: 20485563 PMCID: PMC2869312 DOI: 10.1371/journal.pcbi.1000780] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2009] [Accepted: 04/09/2010] [Indexed: 11/19/2022] Open
Abstract
One mechanism of information storage in neurons is believed to be determined by the strength of synaptic contacts. The strength of an excitatory synapse is partially due to the concentration of a particular type of ionotropic glutamate receptor (AMPAR) in the post-synaptic density (PSD). AMPAR concentration in the PSD has to be plastic, to allow the storage of new memories; but it also has to be stable to preserve important information. Although much is known about the molecular identity of synapses, the biophysical mechanisms by which AMPAR can enter, leave and remain in the synapse are unclear. We used Monte Carlo simulations to determine the influence of PSD structure and activity in maintaining homeostatic concentrations of AMPARs in the synapse. We found that, the high concentration and excluded volume caused by PSD molecules result in molecular crowding. Diffusion of AMPAR in the PSD under such conditions is anomalous. Anomalous diffusion of AMPAR results in retention of these receptors inside the PSD for periods ranging from minutes to several hours in the absence of strong binding of receptors to PSD molecules. Trapping of receptors in the PSD by crowding effects was very sensitive to the concentration of PSD molecules, showing a switch-like behavior for retention of receptors. Non-covalent binding of AMPAR to anchored PSD molecules allowed the synapse to become well-mixed, resulting in normal diffusion of AMPAR. Binding also allowed the exchange of receptors in and out of the PSD. We propose that molecular crowding is an important biophysical mechanism to maintain homeostatic synaptic concentrations of AMPARs in the PSD without the need of energetically expensive biochemical reactions. In this context, binding of AMPAR with PSD molecules could collaborate with crowding to maintain synaptic homeostasis but could also allow synaptic plasticity by increasing the exchange of these receptors with the surrounding extra-synaptic membrane. One of the most accepted theories of information storage in neurons is that it is partially localized in the strength of synaptic contacts. Evidence suggests that at the cellular level, in combination with other cellular mechanisms, this is implemented by increasing or decreasing the concentration of a particular type of membrane molecules. Two opposing mechanisms have to coexist in synapses to allow them to store information. On one hand, synapses have to be flexible, to allow the storage of new memories. On the other hand, synapses have to be stable to preserve previously learned information. Although much is known about the molecular identity of synapses, the biophysical mechanisms by which molecules can enter, leave and remain in the synapse are unclear. Our modeling work uses fundamental biophysical principles to quantify the effects of molecular collisions and biochemical reactions. Our results show that molecular collisions alone, between the diffusing proteins with anchored molecules in the synapse, can replicate known experimental results. Molecular collision in combination with biochemical binding can be fundamental biophysical principles used by synapses for the formation and preservation of memories.
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Affiliation(s)
- Fidel Santamaria
- Biology Department, The University of Texas at San Antonio, San Antonio, Texas, United States of America
- Neurosciences Institute, The University of Texas at San Antonio, San Antonio, Texas, United States of America
- * E-mail: (FS); (SR)
| | - Jossina Gonzalez
- Biology Department, The University of Texas at San Antonio, San Antonio, Texas, United States of America
| | - George J. Augustine
- Department of Neurobiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Sridhar Raghavachari
- Department of Neurobiology, Duke University Medical Center, Durham, North Carolina, United States of America
- * E-mail: (FS); (SR)
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31
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Staras K, Branco T, Burden JJ, Pozo K, Darcy K, Marra V, Ratnayaka A, Goda Y. A vesicle superpool spans multiple presynaptic terminals in hippocampal neurons. Neuron 2010; 66:37-44. [PMID: 20399727 PMCID: PMC2908741 DOI: 10.1016/j.neuron.2010.03.020] [Citation(s) in RCA: 118] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/05/2010] [Indexed: 01/01/2023]
Abstract
Synapse-specific vesicle pools have been widely characterized at central terminals. Here, we demonstrate a vesicle pool that is not confined to a synapse but spans multiple terminals. Using fluorescence imaging, correlative electron microscopy, and modeling of vesicle dynamics, we show that some recycling pool vesicles at synapses form part of a larger vesicle "superpool." The vesicles within this superpool are highly mobile and are rapidly exchanged between terminals (turnover: approximately 4% of total pool/min), significantly changing vesicular composition at synapses over time. In acute hippocampal slices we show that the mobile vesicle pool is also a feature of native brain tissue. We also demonstrate that superpool vesicles are available to synapses during stimulation, providing an extension of the classical recycling pool. Experiments using focal BDNF application suggest the involvement of a local TrkB-receptor-dependent mechanism for synapse-specific regulation of presynaptic vesicle pools through control of vesicle release and capture to or from the extrasynaptic pool.
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Affiliation(s)
- Kevin Staras
- School of Life Sciences, University of Sussex, Brighton, UK.
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32
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Homer and the ryanodine receptor. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 39:91-102. [PMID: 19513708 DOI: 10.1007/s00249-009-0494-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2009] [Revised: 05/15/2009] [Accepted: 05/18/2009] [Indexed: 10/20/2022]
Abstract
Homer proteins have recently been identified as novel high-affinity ligands that modulate ryanodine receptor (RyR) Ca(2+) release channels in heart and skeletal muscle, through an EVH1 domain which binds to proline-rich regions in target proteins. Many Homer proteins can also self-associate through a coiled-coil domain that allows their multimerisation. In other tissues, especially neurons, Homer anchors proteins embedded in the surface membrane to the Ca(2+) release channel in the endoplasmic reticulum and can anchor membrane or cytosolic proteins to the cytoskeleton. Although this anchoring aspect of Homer function has not been extensively investigated in muscle, there are consensus sequences for Homer binding in the RyR and on many of the proteins that it interacts with in the massive RyR ion channel complex. In this review we explore the potential of Homer to contribute to a variety of cell processes in muscle and neurons that also involve RyR channels.
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33
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Sekimoto K, Triller A. Compatibility between itinerant synaptic receptors and stable postsynaptic structure. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 79:031905. [PMID: 19391969 DOI: 10.1103/physreve.79.031905] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2008] [Revised: 01/13/2009] [Indexed: 05/27/2023]
Abstract
The density of synaptic receptors in front of presynaptic release sites is stabilized in the presence of scaffold proteins, but the receptors and scaffold molecules have local exchanges with characteristic times shorter than that of the receptor-scaffold assembly. We propose a mesoscopic model to account for the regulation of the local density of receptors as quasiequilibrium. It is based on two zones (synaptic and extrasynaptic) and multilayer (membrane, submembrane, and cytoplasmic) topological organization. The model includes the balance of chemical potentials associated with the receptor and scaffold protein concentrations in the various compartments. The model shows highly cooperative behavior including a "phase change" resulting in the formation of well-defined postsynaptic domains. This study provides theoretical tools to approach the complex issue of synaptic stability at the synapse, where receptors are transiently trapped yet rapidly diffuse laterally on the plasma membrane.
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Affiliation(s)
- Ken Sekimoto
- Laboratoire Matières et Systèmes Complexes, Université Paris Diderot and CNRS-UMR 7057, 10 rue Alice Domont et Léonie Duquet, 75013 Paris, France
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34
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Targeting Homer genes using adeno-associated viral vector: lessons learned from behavioural and neurochemical studies. Behav Pharmacol 2008; 19:485-500. [PMID: 18690104 DOI: 10.1097/fbp.0b013e32830c369f] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Over a decade of in-vitro data support a critical role for members of the Homer family of postsynaptic scaffolding proteins in regulating the functional architecture of glutamate synapses. Earlier studies of Homer knockout mice indicated a necessary role for Homer gene products in normal mesocorticolimbic glutamate transmission and behaviours associated therewith. The advent of adeno-associated viral vectors carrying cDNA for, or short hairpin RNA against, specific Homer isoforms enabled the site-directed targeting of Homers to neurons in the brain. This approach has allowed our groups to address developmental issues associated with conventional knockout mice, to confirm active roles for distinct Homer isoforms in regulating glutamate transmission in vivo, as well as in mediating a variety of behavioural processes. This review summarizes the existing data derived from our studies using adeno-associated viral vector-mediated neuronal targeting of Homer in rodents, implicating this family of proteins in drug and alcohol addiction, learning/memory and emotional processing.
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35
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Abstract
Information processing in the nervous system relies on properly localized and organized synaptic structures at the correct locations. The formation of synapses is a long and intricate process involving multiple interrelated steps. Decades of research have identified a large number of molecular components of the presynaptic compartment. In addition to neurotransmitter-containing synaptic vesicles, presynaptic terminals are defined by cytoskeletal and membrane specializations that allow highly regulated exo- and endocytosis of synaptic vesicles and that maintain precise registration with postsynaptic targets. Functional studies at multiple levels have revealed complex interactions between the transport of vesicular intermediates, the presynaptic cytoskeleton, growth cone navigation, and synaptic targets. With the advent of finer anatomical, physiological, and molecular tools, great insights have been gained toward the mechanistic dissection of functionally redundant processes controlling the specificity and dynamics of synapses. This review highlights the recent findings pertaining to the cellular and molecular regulation of presynaptic differentiation.
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Affiliation(s)
- Yishi Jin
- Division of Biological Sciences, Section of Neurobiology, Howard Hughes Medical Institute, University of California, San Diego, La Jolla, California 92093, USA.
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36
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Structural plasticity with preserved topology in the postsynaptic protein network. Proc Natl Acad Sci U S A 2008; 105:12587-92. [PMID: 18723686 DOI: 10.1073/pnas.0711669105] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The size, shape, and molecular arrangement of the postsynaptic density (PSD) determine the function of excitatory synapses in the brain. Here, we directly measured the internal dynamics of scaffold proteins within single living PSDs, focusing on the principal scaffold protein PSD-95. We found that individual PSDs undergo rapid, continuous changes in morphology driven by the actin cytoskeleton and regulated by synaptic activity. This structural plasticity is accompanied by rapid fluctuations in internal scaffold density over submicron distances. Using targeted photobleaching and photoactivation of PSD subregions, we show that PSD-95 is nearly immobile within the PSD, and PSD subdomains can be maintained over long periods. We propose a flexible matrix model of the PSD based on stable molecular positioning of PSD-95 scaffolds.
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37
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Szumlinski KK, Ary AW, Lominac KD. Homers regulate drug-induced neuroplasticity: implications for addiction. Biochem Pharmacol 2008; 75:112-33. [PMID: 17765204 PMCID: PMC2204062 DOI: 10.1016/j.bcp.2007.07.031] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2007] [Revised: 07/22/2007] [Accepted: 07/23/2007] [Indexed: 12/20/2022]
Abstract
Drug addiction is a chronic, relapsing disorder, characterized by an uncontrollable motivation to seek and use drugs. Converging clinical and preclinical observations implicate pathologies within the corticolimbic glutamate system in the genetic predisposition to, and the development of, an addicted phenotype. Such observations pose cellular factors regulating glutamate transmission as likely molecular candidates in the etiology of addiction. Members of the Homer family of proteins regulate signal transduction through, and the trafficking of, glutamate receptors, as well as maintain and regulate extracellular glutamate levels in corticolimbic brain regions. This review summarizes the existing data implicating the Homer family of protein in acute behavioral and neurochemical sensitivity to drugs of abuse, the development of drug-induced neuroplasticity, as well as other behavioral and cognitive pathologies associated with an addicted state.
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Affiliation(s)
- Karen K Szumlinski
- Behavioral and Neural Genetics Laboratory, Department of Psychology and the Neuroscience Research Institute, University of California at Santa Barbara, Santa Barbara, CA 93106-9660, USA.
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38
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Inoue Y, Udo H, Inokuchi K, Sugiyama H. Homer1a regulates the activity-induced remodeling of synaptic structures in cultured hippocampal neurons. Neuroscience 2007; 150:841-52. [PMID: 18006237 DOI: 10.1016/j.neuroscience.2007.09.081] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2007] [Revised: 08/30/2007] [Accepted: 10/01/2007] [Indexed: 12/21/2022]
Abstract
Activity-dependent re-organizations of central synapses are thought to play important roles in learning and memory. Although the precise mechanisms of how neuronal activities modify synaptic connections remain to be elucidated, the activity-induced neuronal proteins such as Homer1a may contribute to the onset of synaptic remodeling. To further understand the physiological roles of Homer1a, we first examined prolonged effects of neuronal stimulation capable of inducing Homer1a on the distribution of a postsynaptic protein Homer1c by live imaging and immunostaining. We found that glutamate stimulation induced a biphasic change in the distribution of Homer1c, in which the postsynaptic clusters of Homer1c defused initially after 30 min to 1 h, and then reassembled more than the original level after 4-8 h. When other synaptic proteins (postsynaptic density-95 (PSD95), Filamentous actin (F-actin), glutamate receptors, synaptotagmin, synaptophysin and synapsin) were analyzed by immunocytochemical methods, the distribution of these proteins also showed a similar biphasic pattern, suggesting that glutamate stimulation induces a global alteration in synaptic structures. To further dissect the functions of Homer1a in the activity-induced synaptic remodeling, the short hairpin RNA (shRNA) vectors that specifically block the expression of endogenous Homer1a were constructed. When the shRNA of Homer1a was introduced to the cells, the activity-induced changes were almost completely suppressed. The expression of surface glutamate receptor 2 was also inhibited, suggesting that Homer1a may modulate the efficacy of synaptic transmission. Furthermore, we found that Homer1a contributes to the presynaptic remodeling in a retrograde manner. Our data indicate that Homer1a regulates the activity-induced biphasic changes of post- and pre-synaptic sites.
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Affiliation(s)
- Y Inoue
- Department of Biology, Graduate School of Science, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
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39
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Staras K. Share and share alike: trading of presynaptic elements between central synapses. Trends Neurosci 2007; 30:292-8. [PMID: 17467066 DOI: 10.1016/j.tins.2007.04.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2007] [Revised: 03/20/2007] [Accepted: 04/18/2007] [Indexed: 11/21/2022]
Abstract
Central presynaptic terminals harbour synaptic vesicles (SVs) and synapse-specific proteins necessary for neurotransmission. Classically, these elements were thought to reside more or less stably at individual mature synapses, giving rise to the idea that each terminal was essentially an independent functional unit. However, emerging evidence from fluorescence imaging studies in hippocampal cultured neurons is now challenging this view, suggesting that neighbouring synapses along axons share vesicles, and also other synaptic elements, at high levels. This raises the possibility that control of import and export might be an important regulatory target for the maintenance of release sites, modulation of synaptic efficacy and formation of new synaptic contacts. Here, temporal synaptic stability and the functional consequences for presynaptic operation will be considered.
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Affiliation(s)
- Kevin Staras
- MRC Laboratory for Molecular Cell Biology and Cell Biology Unit, University College London, London, UK.
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40
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Yoshii A, Constantine-Paton M. BDNF induces transport of PSD-95 to dendrites through PI3K-AKT signaling after NMDA receptor activation. Nat Neurosci 2007; 10:702-11. [PMID: 17515902 DOI: 10.1038/nn1903] [Citation(s) in RCA: 235] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2006] [Accepted: 03/30/2007] [Indexed: 01/28/2023]
Abstract
The N-methyl-D-aspartate receptor (NMDAR), brain-derived neurotrophic factor (BDNF), postsynaptic density protein 95 (PSD-95) and phosphatidylinositol 3-kinase (PI3K) have all been implicated in long-term potentiation. Here we show that these molecules are involved in a single pathway for synaptic potentiation. In visual cortical neurons in young rodents, the neurotrophin receptor TrkB is associated with PSD-95. When BDNF is applied to cultured visual cortical neurons, PSD-95-labeled synaptic puncta enlarge, and fluorescent recovery after photobleaching (FRAP) reveals increased delivery of green fluorescent protein-tagged PSD-95 to the dendrites. The recovery of fluorescence requires TrkB, signaling through PI3K and the serine-threonine kinase Akt, and an intact Golgi apparatus. Stimulation of NMDARs mimics the PSD-95 trafficking that is induced by BDNF but requires active BDNF and PI3K. Furthermore, local dendritic contact with a BDNF-coated microsphere induces PSD-95 FRAP throughout the dendrites of the stimulated neuron, suggesting that this mechanism induces rapid neuron-wide synaptic increases in PSD-95 and refinement whenever a few robust inputs activate the NMDAR-BDNF-PI3K pathway.
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Affiliation(s)
- Akira Yoshii
- Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA.
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41
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Jaubert PJ, Golub MS, Lo YY, Germann SL, Dehoff MH, Worley PF, Kang SH, Schwarz MK, Seeburg PH, Berman RF. Complex, multimodal behavioral profile of the Homer1 knockout mouse. GENES BRAIN AND BEHAVIOR 2007; 6:141-54. [PMID: 16734773 DOI: 10.1111/j.1601-183x.2006.00240.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Proteins of the Homer1 immediate early gene family have been associated with synaptogenesis and synaptic plasticity suggesting broad behavioral consequences of loss of function. This study examined the behavior of male Homer1 knockout (KO) mice compared with wild-type (WT) and heterozygous mice using a battery of 10 behavioral tests probing sensory, motor, social, emotional and learning/memory functions. KO mice showed mild somatic growth retardation, poor motor coordination, enhanced sensory reactivity and learning deficits. Heterozygous mice showed increased aggression in social interactions with conspecifics. The distribution of mGluR5 and N-methyl-D-aspartate receptors (NMDA) receptors appeared to be unaltered in the hippocampus (HIP) of Homer1 KO mice. The results indicate an extensive range of disrupted behaviors that should contribute to the understanding of the Homer1 gene in brain development and behavior.
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Affiliation(s)
- P J Jaubert
- Children's Center for Environmental Health & Department of Neurological Surgery, University of California Davis, CA 95616, USA
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42
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Bats C, Groc L, Choquet D. The interaction between Stargazin and PSD-95 regulates AMPA receptor surface trafficking. Neuron 2007; 53:719-34. [PMID: 17329211 DOI: 10.1016/j.neuron.2007.01.030] [Citation(s) in RCA: 428] [Impact Index Per Article: 25.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2006] [Revised: 12/11/2006] [Accepted: 01/26/2007] [Indexed: 10/23/2022]
Abstract
Accumulation of AMPA receptors at synapses is a fundamental feature of glutamatergic synaptic transmission. Stargazin, a member of the TARP family, is an AMPAR auxiliary subunit allowing interaction of the receptor with scaffold proteins of the postsynaptic density, such as PSD-95. How PSD-95 and Stargazin regulate AMPAR number in synaptic membranes remains elusive. We show, using single quantum dot and FRAP imaging in live hippocampal neurons, that exchange of AMPAR by lateral diffusion between extrasynaptic and synaptic sites mostly depends on the interaction of Stargazin with PSD-95 and not upon the GluR2 AMPAR subunit C terminus. Disruption of interactions between Stargazin and PSD-95 strongly increases AMPAR surface diffusion, preventing AMPAR accumulation at postsynaptic sites. Furthermore, AMPARs and Stargazin diffuse as complexes in and out synapses. These results propose a model in which the Stargazin-PSD-95 interaction plays a key role to trap and transiently stabilize diffusing AMPARs in the postsynaptic density.
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Affiliation(s)
- Cecile Bats
- Physiologie Cellulaire de la Synapse, UMR 5091 CNRS - Institut François Magendie, Université Bordeaux, Bordeaux 33077, France
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43
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Okabe S. Molecular anatomy of the postsynaptic density. Mol Cell Neurosci 2007; 34:503-18. [PMID: 17321751 DOI: 10.1016/j.mcn.2007.01.006] [Citation(s) in RCA: 165] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2006] [Revised: 01/18/2007] [Accepted: 01/18/2007] [Indexed: 10/23/2022] Open
Abstract
The postsynaptic density (PSD) is a structure composed of both membranous and cytoplasmic proteins localized at the postsynaptic plasma membrane of excitatory synapses. Biochemical and molecular biological studies have identified a number of proteins present in the PSD. Glutamate receptors are important constituents of the PSD and membrane proteins involved in synaptic signal transduction and cell adhesion are also essential components. Scaffolding proteins containing multiple protein interaction motifs are thought to provide the framework of the PSD through their interactions with both membrane proteins and the cytoplasmic proteins. Among the cytoplasmic signaling molecules, calcium-calmodulin-dependent protein kinase II stands out as a major component of the PSD and its dynamic translocation to the PSD in response to neuronal activity is crucial in synaptic signal transduction. Recent advancements in molecular biological, structural and electrophysiological techniques have enabled us to directly measure the number, distribution and interactions of PSD molecules with high sensitivity and precision. In this review, I describe the structure and molecular composition of the PSD as well as the molecular interactions between the major constituents. This information will be combined with recent quantitative analyses of the PSD protein contents per synapse, in order to provide a current view of the PSD molecular architecture and its dynamics.
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Affiliation(s)
- Shigeo Okabe
- Department of Cell Biology, School of Medicine, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8519, Japan.
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44
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Tsuriel S, Geva R, Zamorano P, Dresbach T, Boeckers T, Gundelfinger ED, Garner CC, Ziv NE. Local sharing as a predominant determinant of synaptic matrix molecular dynamics. PLoS Biol 2007; 4:e271. [PMID: 16903782 PMCID: PMC1540708 DOI: 10.1371/journal.pbio.0040271] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2005] [Accepted: 06/14/2006] [Indexed: 01/03/2023] Open
Abstract
Recent studies suggest that central nervous system synapses can persist for weeks, months, perhaps lifetimes, yet little is known as to how synapses maintain their structural and functional characteristics for so long. As a step toward a better understanding of synaptic maintenance we examined the loss, redistribution, reincorporation, and replenishment dynamics of Synapsin I and ProSAP2/Shank3, prominent presynaptic and postsynaptic matrix molecules, respectively. Fluorescence recovery after photobleaching and photoactivation experiments revealed that both molecules are continuously lost from, redistributed among, and reincorporated into synaptic structures at time-scales of minutes to hours. Exchange rates were not affected by inhibiting protein synthesis or proteasome-mediated protein degradation, were accelerated by stimulation, and greatly exceeded rates of replenishment from somatic sources. These findings indicate that the dynamics of key synaptic matrix molecules may be dominated by local protein exchange and redistribution, whereas protein synthesis and degradation serve to maintain and regulate the sizes of local, shared pools of these proteins. To understand processes involved in synaptic maintenance, the authors examine the loss, redistribution, reincorporation and replenishment dynamics of two key synaptic proteins, Synapsin I and ProSAP2/Shank3.
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Affiliation(s)
- Shlomo Tsuriel
- The Rappaport Family Institute for Research in the Medical Sciences, Technion Faculty of Medicine, Haifa, Israel
- The Department of Physiology, Technion Faculty of Medicine, Haifa, Israel
| | - Ran Geva
- The Rappaport Family Institute for Research in the Medical Sciences, Technion Faculty of Medicine, Haifa, Israel
- The Department of Physiology, Technion Faculty of Medicine, Haifa, Israel
| | - Pedro Zamorano
- Department of Psychiatry and Behavioral Science, Nancy Pritzker Laboratory, Stanford University, Palo Alto, California, United States of America
| | - Thomas Dresbach
- Institute of Anatomy and Cell Biology II, University of Heidelberg, Heidelberg, Germany
| | - Tobias Boeckers
- Institute of Anatomy and Cell Biology, University of Ulm, Ulm, Germany
| | - Eckart D Gundelfinger
- Department of Neurochemistry and Molecular Biology, Leibniz Institute for Neurobiology, Magdeburg, Germany
| | - Craig C Garner
- Department of Psychiatry and Behavioral Science, Nancy Pritzker Laboratory, Stanford University, Palo Alto, California, United States of America
| | - Noam E Ziv
- The Rappaport Family Institute for Research in the Medical Sciences, Technion Faculty of Medicine, Haifa, Israel
- The Department of Physiology, Technion Faculty of Medicine, Haifa, Israel
- * To whom correspondence should be addressed. E-mail:
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45
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Kim E, Ko J. Molecular organization and assembly of the postsynaptic density of excitatory brain synapses. Results Probl Cell Differ 2006; 43:1-23. [PMID: 17068965 DOI: 10.1007/400_011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/27/2023]
Abstract
The postsynaptic density (PSD) is a postsynaptic membrane specialization at excitatory synapses. The PSD is made of macromolecular multiprotein complexes, which contain a variety of synaptic proteins including membrane, scaffolding, and signaling proteins. By coaggregating with postsynaptic cell adhesion molecules, PSD proteins promote the formation and maturation of excitatory synapses. PSD proteins organize signaling pathways to coordinate structural and functional changes in synapses, and they regulate trafficking and recycling of glutamate receptors, which determines synaptic strength and plasticity. Synaptic activity dynamically regulates the assembly of the PSD through mechanisms including protein phosphorylation, palmitoylation, and protein degradation. PSD proteins associate with diverse motor proteins, suggesting that they function as adaptors linking motors to their specific cargoes.
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Affiliation(s)
- Eunjoon Kim
- National Creative Research Initiative Center for Synaptogenesis and Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon.
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46
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Garner CC, Waites CL, Ziv NE. Synapse development: still looking for the forest, still lost in the trees. Cell Tissue Res 2006; 326:249-62. [PMID: 16909256 DOI: 10.1007/s00441-006-0278-1] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2006] [Accepted: 06/08/2006] [Indexed: 01/23/2023]
Abstract
Synapse development in the vertebrate central nervous system is a highly orchestrated process occurring not only during early stages of brain development, but also (to a lesser extent) in the mature nervous system. During development, the formation of synapses is intimately linked to the differentiation of neuronal cells, the extension of their axons and dendrites, and the course wiring of the nervous system. Subsequently, the stabilization, elimination, and strengthening of synaptic contacts is coupled to the refinement of axonal and dendritic arbors, to the establishment of functionally meaningful connections, and probably also to the day-to-day acquisition, storage, and retrieval of memories, higher order thought processes, and behavioral patterns.
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Affiliation(s)
- Craig C Garner
- Department of Psychiatry and Behavioral Science, Nancy Pritzer Laboratory, Stanford University, Palo Alto, CA 94304-5485, USA.
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47
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Bortoloso E, Pilati N, Megighian A, Tibaldo E, Sandonà D, Volpe P. Transition of Homer isoforms during skeletal muscle regeneration. Am J Physiol Cell Physiol 2006; 290:C711-8. [PMID: 16236824 DOI: 10.1152/ajpcell.00217.2005] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Homer represents a new and diversified family of proteins that includes several isoforms, Homer 1, 2, and 3; some of these isoforms have been reported to be present in striated muscles. In this study, the presence of Homer isoforms 1a, 1b/c/d, 2b, and 3 was thoroughly investigated in rat skeletal muscles under resting conditions. Transition in Homer isoforms compositon was studied under experimental conditions of short-term and long-term adaptation, e.g., fatigue and regeneration, respectively. First, we show that Homer 1a was constitutively expressed and was transiently upregulated during regeneration. In C2C12 cell cultures, Homer 1a was also upregulated during formation of myotubes. No change of Homer 1a was observed in fatigue. Second, Homer 1b/c/d and Homer 2b were positively and linearly related to muscle mass change during regeneration, and third, Homer 3 was not detectable under resting conditions but was transiently expressed during regeneration although with a temporal pattern distinct from that of Homer 1a. Thus a switch in Homer isoforms is associated to muscle differentiation and regeneration. Homers may play a role not only in signal transduction of skeletal muscle, in particular regulation of Ca2+ release from sarcoplasmic reticulum (Ward CW, Feng W, Tu J, Pessah IN, Worley PF, and Schneider MF. Homer protein increases activation of Ca2+ sparks in permeabilized skeletal muscle. J Biol Chem 279: 5781–5787, 2004), but also in adaptation.
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Affiliation(s)
- Elena Bortoloso
- Dipartimento di Scienze Biomediche Sperimentali, Università degli Studi di Padova, viale G. Colombo 3, 35121 Padova, Italy
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Sharma K, Fong DK, Craig AM. Postsynaptic protein mobility in dendritic spines: long-term regulation by synaptic NMDA receptor activation. Mol Cell Neurosci 2006; 31:702-12. [PMID: 16504537 DOI: 10.1016/j.mcn.2006.01.010] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2005] [Revised: 11/30/2005] [Accepted: 01/01/2006] [Indexed: 11/29/2022] Open
Abstract
Reorganization of molecular components represents a cellular mechanism for synaptic plasticity. Dendritic spines, major sites for glutamatergic synapses, compartmentalize dynamic changes in molecular composition. Here, we use fluorescence recovery after photobleaching (FRAP) in cultured hippocampal neurons to show that spine proteins undergo continual exchange with extra-spine pools. Each spine component has a distinctive mobility: calcium/calmodulin activated protein kinase CaMKIIalpha > GluR1 AMPA glutamate receptor > PSD-95 scaffolding protein > NR1 NMDA glutamate receptor. Stimulation of synaptic NMDA receptors by a protocol that induces chemical LTP resulted in a long-lasting reduction in the mobility of spine CaMKIIalpha and an increased mobile fraction but slower kinetics for spine GluR1. Stimulation also increased the resistance of postsynaptic CaMKIIalpha to detergent extraction. These results suggest long-lasting changes in affinity of protein-protein interactions and/or ongoing alterations in exo/endocytosis. Such lasting changes in protein mobility may contribute to maintaining alterations in synaptic efficacy.
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Affiliation(s)
- Kamal Sharma
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
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Tombler E, Cabanilla NJ, Carman P, Permaul N, Hall JJ, Richman RW, Lee J, Rodriguez J, Felsenfeld DP, Hennigan RF, Diversé-Pierluissi MA. G protein-induced trafficking of voltage-dependent calcium channels. J Biol Chem 2005; 281:1827-39. [PMID: 16293615 DOI: 10.1074/jbc.m508829200] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Calcium channels are well known targets for inhibition by G protein-coupled receptors, and multiple forms of inhibition have been described. Here we report a novel mechanism for G protein-mediated modulation of neuronal voltage-dependent calcium channels that involves the destabilization and subsequent removal of calcium channels from the plasma membrane. Imaging experiments in living sensory neurons show that, within seconds of receptor activation, calcium channels are cleared from the membrane and sequestered in clathrin-coated vesicles. Disruption of the L1-CAM-ankyrin B complex with the calcium channel mimics transmitter-induced trafficking of the channels, reduces calcium influx, and decreases exocytosis. Our results suggest that G protein-induced removal of plasma membrane calcium channels is a consequence of disrupting channel-cytoskeleton interactions and might represent a novel mechanism of presynaptic inhibition.
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Affiliation(s)
- Eugene Tombler
- Department of Pharmacology and Biological Chemistry, Mount Sinai School of Medicine, New York, New York 10029, USA
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Sugiyama Y, Kawabata I, Sobue K, Okabe S. Determination of absolute protein numbers in single synapses by a GFP-based calibration technique. Nat Methods 2005; 2:677-84. [PMID: 16118638 DOI: 10.1038/nmeth783] [Citation(s) in RCA: 141] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Accepted: 07/18/2005] [Indexed: 11/08/2022]
Abstract
To build a quantitative model of molecular organization of neurons, it is essential to have information about the number of protein molecules at individual synapses. Here we developed a method to estimate absolute numbers of individual proteins at actual excitatory synapses by calibrating the fluorescence intensity of microspheres with single EGFP molecules. In cultured hippocampal neurons, we observed a monotonous increase of postsynaptic protein numbers per single synapse during neuronal differentiation and subsequent stabilization. At maturity we calculated that a single excitatory postsynaptic site contains 100-450 of individual postsynaptic proteins, such as PSD-95, GKAP, Shank and Homer. This narrow range of postsynaptic protein content suggests relatively simple stoichiometry of postsynaptic molecular organization. The EGFP-based calibration technique provides an unprecedented general method for estimating the amounts of proteins in macromolecular complexes.
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Affiliation(s)
- Yoshiko Sugiyama
- Department of Cell Biology, School of Medicine, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo, 113-8519, Japan
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