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APLP1 Is a Synaptic Cell Adhesion Molecule, Supporting Maintenance of Dendritic Spines and Basal Synaptic Transmission. J Neurosci 2017; 37:5345-5365. [PMID: 28450540 DOI: 10.1523/jneurosci.1875-16.2017] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Revised: 02/22/2017] [Accepted: 03/24/2017] [Indexed: 12/19/2022] Open
Abstract
The amyloid precursor protein (APP), a key player in Alzheimer's disease, belongs to the family of synaptic adhesion molecules (SAMs) due to its impact on synapse formation and synaptic plasticity. These functions are mediated by both the secreted APP ectodomain that acts as a neurotrophic factor and full-length APP forming trans-cellular dimers. Two homologs of APP exist in mammals: the APP like proteins APLP1 and APLP2, exhibiting functions that partly overlap with those of APP. Here we tested whether APLP1 and APLP2 also show features of SAMs. We found that all three family members were upregulated during postnatal development coinciding with synaptogenesis. We observed presynaptic and postsynaptic localization of all APP family members and could show that heterologous expression of APLP1 or APLP2 in non-neuronal cells induces presynaptic differentiation in contacting axons of cocultured neurons, similar to APP and other SAMs. Moreover, APP/APLPs all bind to synaptic-signaling molecules, such as MINT/X11. Furthermore, we report that aged APLP1 knock-out mice show impaired basal transmission and a reduced mEPSC frequency, likely resulting from reduced spine density. This demonstrates an essential nonredundant function of APLP1 at the synapse. Compared to APP, APLP1 exhibits increased trans-cellular binding and elevated cell-surface levels due to reduced endocytosis. In conclusion, our results establish that APLPs show typical features of SAMs and indicate that increased surface expression, as observed for APLP1, is essential for proper synapse formation in vitro and synapse maintenance in vivoSIGNIFICANCE STATEMENT According to the amyloid-cascade hypothesis, Alzheimer's disease is caused by the accumulation of Aβ peptides derived from sequential cleavage of the amyloid precursor protein (APP) by β-site APP cleaving enzyme 1 (BACE1) and γ-secretase. Here we show that all mammalian APP family members (APP, APLP1, and APLP2) exhibit synaptogenic activity, involving trans-synaptic dimerization, similar to other synaptic cell adhesion molecules, such as Neuroligin/Neurexin. Importantly, our study revealed that the loss of APLP1, which is one of the major substrates of BACE1, causes reduced spine density in aged mice. Because some therapeutic interventions target APP processing (e.g., BACE inhibitors), those strategies may alter APP/APLP physiological function. This should be taken into account for the development of pharmaceutical treatments of Alzheimer's disease.
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Shiotani H, Maruo T, Sakakibara S, Miyata M, Mandai K, Mochizuki H, Takai Y. Aging-dependent expression of synapse-related proteins in the mouse brain. Genes Cells 2017; 22:472-484. [DOI: 10.1111/gtc.12489] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Accepted: 03/08/2017] [Indexed: 01/13/2023]
Affiliation(s)
- Hajime Shiotani
- Division of Pathogenetic Signaling, Department of Biochemistry and Molecular Biology; Kobe University Graduate School of Medicine; Kobe 650-0047 Japan
- Department of Neurology; Osaka University Graduate School of Medicine; Suita 565-0871 Japan
| | - Tomohiko Maruo
- Division of Pathogenetic Signaling, Department of Biochemistry and Molecular Biology; Kobe University Graduate School of Medicine; Kobe 650-0047 Japan
| | - Shotaro Sakakibara
- Division of Pathogenetic Signaling, Department of Biochemistry and Molecular Biology; Kobe University Graduate School of Medicine; Kobe 650-0047 Japan
| | - Muneaki Miyata
- Division of Pathogenetic Signaling, Department of Biochemistry and Molecular Biology; Kobe University Graduate School of Medicine; Kobe 650-0047 Japan
| | - Kenji Mandai
- Division of Pathogenetic Signaling, Department of Biochemistry and Molecular Biology; Kobe University Graduate School of Medicine; Kobe 650-0047 Japan
| | - Hideki Mochizuki
- Department of Neurology; Osaka University Graduate School of Medicine; Suita 565-0871 Japan
| | - Yoshimi Takai
- Division of Pathogenetic Signaling, Department of Biochemistry and Molecular Biology; Kobe University Graduate School of Medicine; Kobe 650-0047 Japan
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Guénette S, Strecker P, Kins S. APP Protein Family Signaling at the Synapse: Insights from Intracellular APP-Binding Proteins. Front Mol Neurosci 2017; 10:87. [PMID: 28424586 PMCID: PMC5371672 DOI: 10.3389/fnmol.2017.00087] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Accepted: 03/13/2017] [Indexed: 12/17/2022] Open
Abstract
Understanding the molecular mechanisms underlying amyloid precursor protein family (APP/APP-like proteins, APLP) function in the nervous system can be achieved by studying the APP/APLP interactome. In this review article, we focused on intracellular APP interacting proteins that bind the YENPTY internalization motif located in the last 15 amino acids of the C-terminal region. These proteins, which include X11/Munc-18-interacting proteins (Mints) and FE65/FE65Ls, represent APP cytosolic binding partners exhibiting different neuronal functions. A comparison of FE65 and APP family member mutant mice revealed a shared function for APP/FE65 protein family members in neurogenesis and neuronal positioning. Accumulating evidence also supports a role for membrane-associated APP/APLP proteins in synapse formation and function. Therefore, it is tempting to speculate that APP/APLP C-terminal interacting proteins transmit APP/APLP-dependent signals at the synapse. Herein, we compare our current knowledge of the synaptic phenotypes of APP/APLP mutant mice with those of mice lacking different APP/APLP interaction partners and discuss the possible downstream effects of APP-dependent FE65/FE65L or X11/Mint signaling on synaptic vesicle release, synaptic morphology and function. Given that the role of X11/Mint proteins at the synapse is well-established, we propose a model highlighting the role of FE65 protein family members for transduction of APP/APLP physiological function at the synapse.
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Affiliation(s)
| | - Paul Strecker
- Department of Biology, Division of Human Biology, University of KaiserslauternKaiserslautern, Germany
| | - Stefan Kins
- Department of Biology, Division of Human Biology, University of KaiserslauternKaiserslautern, Germany
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104
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Roh JD, Choi SY, Cho YS, Choi TY, Park JS, Cutforth T, Chung W, Park H, Lee D, Kim MH, Lee Y, Mo S, Rhee JS, Kim H, Ko J, Choi SY, Bae YC, Shen K, Kim E, Han K. Increased Excitatory Synaptic Transmission of Dentate Granule Neurons in Mice Lacking PSD-95-Interacting Adhesion Molecule Neph2/Kirrel3 during the Early Postnatal Period. Front Mol Neurosci 2017; 10:81. [PMID: 28381988 PMCID: PMC5360738 DOI: 10.3389/fnmol.2017.00081] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2017] [Accepted: 03/08/2017] [Indexed: 11/13/2022] Open
Abstract
Copy number variants and point mutations of NEPH2 (also called KIRREL3) gene encoding an immunoglobulin (Ig) superfamily adhesion molecule have been linked to autism spectrum disorders, intellectual disability and neurocognitive delay associated with Jacobsen syndrome, but the physiological roles of Neph2 in the mammalian brain remain largely unknown. Neph2 is highly expressed in the dentate granule (DG) neurons of the hippocampus and is localized in both dendrites and axons. It was recently shown that Neph2 is required for the formation of mossy fiber filopodia, the axon terminal structure of DG neurons forming synapses with GABAergic neurons of CA3. In contrast, however, it is unknown whether Neph2 also has any roles in the postsynaptic compartments of DG neurons. We here report that, through its C-terminal PDZ domain-binding motif, Neph2 directly interacts with postsynaptic density (PSD)-95, an abundant excitatory postsynaptic scaffolding protein. Moreover, Neph2 protein is detected in the brain PSD fraction and interacts with PSD-95 in synaptosomal lysates. Functionally, loss of Neph2 in mice leads to age-specific defects in the synaptic connectivity of DG neurons. Specifically, Neph2-/- mice show significantly increased spontaneous excitatory synaptic events in DG neurons at postnatal week 2 when the endogenous Neph2 protein expression peaks, but show normal excitatory synaptic transmission at postnatal week 3. The evoked excitatory synaptic transmission and synaptic plasticity of medial perforant pathway (MPP)-DG synapses are also normal in Neph2-/- mice at postnatal week 3, further confirming the age-specific synaptic defects. Together, our results provide some evidence for the postsynaptic function of Neph2 in DG neurons during the early postnatal period, which might be implicated in neurodevelopmental and cognitive disorders caused by NEPH2 mutations.
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Affiliation(s)
- Junyeop D Roh
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST) Daejeon, South Korea
| | - Su-Yeon Choi
- Center for Synaptic Brain Dysfunctions, Institute for Basic Science (IBS) Daejeon, South Korea
| | - Yi Sul Cho
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University Daegu, South Korea
| | - Tae-Yong Choi
- Department of Physiology, Dental Research Institute, Seoul National University School of Dentistry Seoul, South Korea
| | - Jong-Sil Park
- Department of Physiology, Dental Research Institute, Seoul National University School of Dentistry Seoul, South Korea
| | - Tyler Cutforth
- Department of Neurology, Columbia University Medical Center New York, NY, USA
| | - Woosuk Chung
- Department of Anesthesiology and Pain Medicine, College of Medicine, Chungnam National University Daejeon, South Korea
| | - Hanwool Park
- Center for Synaptic Brain Dysfunctions, Institute for Basic Science (IBS) Daejeon, South Korea
| | - Dongsoo Lee
- Center for Synaptic Brain Dysfunctions, Institute for Basic Science (IBS) Daejeon, South Korea
| | - Myeong-Heui Kim
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST) Daejeon, South Korea
| | - Yeunkum Lee
- Department of Neuroscience, College of Medicine, Korea University Seoul, South Korea
| | - Seojung Mo
- Department of Anatomy, College of Medicine, Korea University Seoul, South Korea
| | - Jeong-Seop Rhee
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine Göttingen, Germany
| | - Hyun Kim
- Department of Anatomy, College of Medicine, Korea University Seoul, South Korea
| | - Jaewon Ko
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST) Daegu, South Korea
| | - Se-Young Choi
- Department of Physiology, Dental Research Institute, Seoul National University School of Dentistry Seoul, South Korea
| | - Yong Chul Bae
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University Daegu, South Korea
| | - Kang Shen
- Department of Biology, Howard Hughes Medical Institute, Stanford University Stanford, CA, USA
| | - Eunjoon Kim
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST)Daejeon, South Korea; Center for Synaptic Brain Dysfunctions, Institute for Basic Science (IBS)Daejeon, South Korea
| | - Kihoon Han
- Department of Neuroscience, College of Medicine, Korea University Seoul, South Korea
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105
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Pan-neurexin perturbation results in compromised synapse stability and a reduction in readily releasable synaptic vesicle pool size. Sci Rep 2017; 7:42920. [PMID: 28220838 PMCID: PMC5318902 DOI: 10.1038/srep42920] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 01/16/2017] [Indexed: 11/08/2022] Open
Abstract
Neurexins are a diverse family of cell adhesion molecules that localize to presynaptic specializations of CNS neurons. Heterologous expression of neurexins in non-neuronal cells leads to the recruitment of postsynaptic proteins in contacting dendrites of co-cultured neurons, implicating neurexins in synapse formation. However, isoform-specific knockouts of either all α- or all β-neurexins show defects in synaptic transmission but an unaltered density of glutamatergic synapses, a finding that argues against an essential function of neurexins in synaptogenesis. To address the role of neurexin in synapse formation and function, we disrupted the function of all α- and β-neurexins in cultured hippocampal neurons by shRNA knockdown or by overexpressing a neurexin mutant that is unable to bind to postsynaptic neurexin ligands. We show that neurexin perturbation results in an attenuation of neurotransmitter release that is in large part due to a reduction in the number of readily releasable synaptic vesicles. We also find that neurexin perturbation fails to alter the ability of neurons to form synapses, but rather leads to more frequent synapse elimination. These experiments suggest that neurexins are dispensable for the formation of initial synaptic contacts, but play an essential role in the stabilization and functional maturation of synapses.
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106
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Amyloid-β Oligomers Interact with Neurexin and Diminish Neurexin-mediated Excitatory Presynaptic Organization. Sci Rep 2017; 7:42548. [PMID: 28211900 PMCID: PMC5304201 DOI: 10.1038/srep42548] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 01/12/2017] [Indexed: 01/29/2023] Open
Abstract
Alzheimer's disease (AD) is characterized by excessive production and deposition of amyloid-beta (Aβ) proteins as well as synapse dysfunction and loss. While soluble Aβ oligomers (AβOs) have deleterious effects on synapse function and reduce synapse number, the underlying molecular mechanisms are not well understood. Here we screened synaptic organizer proteins for cell-surface interaction with AβOs and identified a novel interaction between neurexins (NRXs) and AβOs. AβOs bind to NRXs via the N-terminal histidine-rich domain (HRD) of β-NRX1/2/3 and alternatively-spliced inserts at splicing site 4 of NRX1/2. In artificial synapse-formation assays, AβOs diminish excitatory presynaptic differentiation induced by NRX-interacting proteins including neuroligin1/2 (NLG1/2) and the leucine-rich repeat transmembrane protein LRRTM2. Although AβOs do not interfere with the binding of NRX1β to NLG1 or LRRTM2, time-lapse imaging revealed that AβO treatment reduces surface expression of NRX1β on axons and that this reduction depends on the NRX1β HRD. In transgenic mice expressing mutated human amyloid precursor protein, synaptic expression of β-NRXs, but not α-NRXs, decreases. Thus our data indicate that AβOs interact with NRXs and that this interaction inhibits NRX-mediated presynaptic differentiation by reducing surface expression of axonal β-NRXs, providing molecular and mechanistic insights into how AβOs lead to synaptic pathology in AD.
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107
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Wild K, August A, Pietrzik CU, Kins S. Structure and Synaptic Function of Metal Binding to the Amyloid Precursor Protein and its Proteolytic Fragments. Front Mol Neurosci 2017; 10:21. [PMID: 28197076 PMCID: PMC5281630 DOI: 10.3389/fnmol.2017.00021] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 01/16/2017] [Indexed: 12/19/2022] Open
Abstract
Alzheimer’s disease (AD) is ultimately linked to the amyloid precursor protein (APP). However, current research reveals an important synaptic function of APP and APP-like proteins (APLP1 and 2). In this context various neurotrophic and neuroprotective functions have been reported for the APP proteolytic fragments sAPPα, sAPPβ and the monomeric amyloid-beta peptide (Aβ). APP is a metalloprotein and binds copper and zinc ions. Synaptic activity correlates with a release of these ions into the synaptic cleft and dysregulation of their homeostasis is linked to different neurodegenerative diseases. Metal binding to APP or its fragments affects its structure and its proteolytic cleavage and therefore its physiological function at the synapse. Here, we summarize the current data supporting this hypothesis and provide a model of how these different mechanisms might be intertwined with each other.
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Affiliation(s)
- Klemens Wild
- Heidelberg University Biochemistry Center (BZH), University of Heidelberg Heidelberg, Germany
| | - Alexander August
- Division of Human Biology and Human Genetics, Technical University of Kaiserslautern Kaiserslautern, Germany
| | - Claus U Pietrzik
- Institute for Pathobiochemistry, University Medical Center of the Johannes Gutenberg-University Mainz Mainz, Germany
| | - Stefan Kins
- Division of Human Biology and Human Genetics, Technical University of Kaiserslautern Kaiserslautern, Germany
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108
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Vezina-Audette R, Tremblay M, Carbonetto S. Laminin is instructive and calmodulin dependent kinase II is non-permissive for the formation of complex aggregates of acetylcholine receptors on myotubes in culture. Matrix Biol 2016; 57-58:106-123. [PMID: 27964993 DOI: 10.1016/j.matbio.2016.11.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 11/16/2016] [Indexed: 12/11/2022]
Abstract
Previous work has shown that myotubes cultured on laminin-coated substrates form complex aggregates of synaptic proteins that are similar in shape and composition to neuromuscular junctions (NMJs). Here we show that laminin instructs the location of complex aggregates which form only on the lower surface when laminin is coated onto culture dishes but over the entire cell when laminin is added in solution. Silencing of myotubes by agents that block electrical activity (tetrodotoxin, verapamil) or by inhibitors of calmodulin dependent kinase (CaMKII) render the myotube permissive for the formation of complex aggregates. Treatment with laminin alone will facilitate the formation of complex aggregates hours later when myotubes are made permissive by inhibiting CaMKII. The AChR agonist carbachol disperses pre formed aggregates suggesting that non-permissiveness may involve active dispersal of AChRs. The permissive period requires ongoing protein synthesis. The latter may reflect a requirement for rapsyn, which turns over rapidly, and is necessary for aggregation. Consistent with this geldanamycin, an agent that increases rapsyn turnover disrupts complex aggregates. Agrin is well known to induce small clusters of AChRs but does not induce complex aggregates even though aggregate formation requires MuSK, a receptor tyrosine kinase activated by agrin. Dystroglycan (DG) is the major laminin receptor mediating complex aggregate formation with some contribution from β1 integrins. In addition, there is a pool of CaMKII associated with DG. We discuss how these permissive and instructive mechanisms bear on NMJ formation in vivo.
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Affiliation(s)
- Raphael Vezina-Audette
- Centre for Research in Neuroscience, and Dept. of Neurology, McGill University Health Centre, 1650, Cedar Ave., Montreal, Quebec, H3G 1A4, Canada
| | - Mathieu Tremblay
- Centre for Research in Neuroscience, and Dept. of Neurology, McGill University Health Centre, 1650, Cedar Ave., Montreal, Quebec, H3G 1A4, Canada
| | - Salvatore Carbonetto
- Centre for Research in Neuroscience, and Dept. of Neurology, McGill University Health Centre, 1650, Cedar Ave., Montreal, Quebec, H3G 1A4, Canada.
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109
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Roppongi RT, Karimi B, Siddiqui TJ. Role of LRRTMs in synapse development and plasticity. Neurosci Res 2016; 116:18-28. [PMID: 27810425 DOI: 10.1016/j.neures.2016.10.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 10/10/2016] [Accepted: 10/14/2016] [Indexed: 12/19/2022]
Abstract
Leucine-rich-repeat transmembrane neuronal proteins (LRRTMs) are a family of four synapse organizing proteins critical for the development and function of excitatory synapses. The genes encoding LRRTMs and their binding partners, neurexins and HSPGs, are strongly associated with multiple psychiatric disorders. Here, we review the literature covering their structural features, expression patterns in the developing and adult brains, evolutionary origins, and discovery as synaptogenic proteins. We also discuss their role in the development and plasticity of excitatory synapses as well as their disease associations.
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Affiliation(s)
- Reiko T Roppongi
- Department of Physiology and Pathophysiology, College of Medicine, University of Manitoba, Winnipeg, MB, Canada; Neuroscience Research Program, Kleysen Institute for Advanced Medicine, Health Sciences Centre, 710 William Avenue, Winnipeg R3Y 0Z3, MB, Canada
| | - Benyamin Karimi
- Department of Physiology and Pathophysiology, College of Medicine, University of Manitoba, Winnipeg, MB, Canada; Neuroscience Research Program, Kleysen Institute for Advanced Medicine, Health Sciences Centre, 710 William Avenue, Winnipeg R3Y 0Z3, MB, Canada
| | - Tabrez J Siddiqui
- Department of Physiology and Pathophysiology, College of Medicine, University of Manitoba, Winnipeg, MB, Canada; Neuroscience Research Program, Kleysen Institute for Advanced Medicine, Health Sciences Centre, 710 William Avenue, Winnipeg R3Y 0Z3, MB, Canada.
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110
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The Purkinje cell as a model of synaptogenesis and synaptic specificity. Brain Res Bull 2016; 129:12-17. [PMID: 27721030 DOI: 10.1016/j.brainresbull.2016.10.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 09/28/2016] [Accepted: 10/05/2016] [Indexed: 01/03/2023]
Abstract
Since the groundbreaking work of Ramon y Cajal, the cerebellar Purkinje cell has always represented an ideal model for studying the organization, development and function of synaptic circuits. Purkinje cells receive distinct types of glutamatergic and GABAergic synapses, each characterized by exquisite sub-cellular and molecular specificity. The formation and refinement of these connections results from a temporally-regulated sequence of events that involves molecular interactions between distinct sets of secreted and surface proteins, as well as activity-dependent competition between converging inputs. Insights into the mechanisms controlling synaptic specificity in Purkinje cells may help understand synapse development also in other brain regions and disclose circuit abnormalities that underlie neurodevelopmental disorders.
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111
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Wierenga CJ. Live imaging of inhibitory axons: Synapse formation as a dynamic trial-and-error process. Brain Res Bull 2016; 129:43-49. [PMID: 27720814 DOI: 10.1016/j.brainresbull.2016.09.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Revised: 09/20/2016] [Accepted: 09/29/2016] [Indexed: 02/07/2023]
Abstract
In this review I discuss recent live imaging studies that demonstrate that synapses, and in particular inhibitory synapses, are highly dynamic structures. The ongoing changes of presynaptic boutons within axons emphasize the stochastic aspect of inhibitory synapse formation and paint a picture of a dynamic trial-and-error process. Furthermore, I discuss recent and previous insights in the molecular and mechanistic pathways that underlie synapse formation, with a specific focus on the formation of inhibitory presynaptic boutons.
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Affiliation(s)
- Corette J Wierenga
- Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
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112
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Irala D, Bonafina A, Fontanet PA, Alsina FC, Paratcha G, Ledda F. The GDNF-GFRα1 complex promotes the development of hippocampal dendritic arbors and spines via NCAM. Development 2016; 143:4224-4235. [PMID: 27707798 DOI: 10.1242/dev.140350] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2016] [Accepted: 09/28/2016] [Indexed: 12/26/2022]
Abstract
The formation of synaptic connections during nervous system development requires the precise control of dendrite growth and synapse formation. Although glial cell line-derived neurotrophic factor (GDNF) and its receptor GFRα1 are expressed in the forebrain, the role of this system in the hippocampus remains unclear. Here, we investigated the consequences of GFRα1 deficiency for the development of hippocampal connections. Analysis of conditional Gfra1 knockout mice shows a reduction in dendritic length and complexity, as well as a decrease in postsynaptic density specializations and in the synaptic localization of postsynaptic proteins in hippocampal neurons. Gain- and loss-of-function assays demonstrate that the GDNF-GFRα1 complex promotes dendritic growth and postsynaptic differentiation in cultured hippocampal neurons. Finally, in vitro assays revealed that GDNF-GFRα1-induced dendrite growth and spine formation are mediated by NCAM signaling. Taken together, our results indicate that the GDNF-GFRα1 complex is essential for proper hippocampal circuit development.
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Affiliation(s)
- Dolores Irala
- Division of Molecular and Cellular Neuroscience, Institute of Cell Biology and Neuroscience (IBCN)-CONICET, School of Medicine, University of Buenos Aires (UBA), Buenos Aires 1121, Argentina
| | - Antonela Bonafina
- Division of Molecular and Cellular Neuroscience, Institute of Cell Biology and Neuroscience (IBCN)-CONICET, School of Medicine, University of Buenos Aires (UBA), Buenos Aires 1121, Argentina
| | - Paula Aldana Fontanet
- Division of Molecular and Cellular Neuroscience, Institute of Cell Biology and Neuroscience (IBCN)-CONICET, School of Medicine, University of Buenos Aires (UBA), Buenos Aires 1121, Argentina
| | - Fernando Cruz Alsina
- Division of Molecular and Cellular Neuroscience, Institute of Cell Biology and Neuroscience (IBCN)-CONICET, School of Medicine, University of Buenos Aires (UBA), Buenos Aires 1121, Argentina
| | - Gustavo Paratcha
- Division of Molecular and Cellular Neuroscience, Institute of Cell Biology and Neuroscience (IBCN)-CONICET, School of Medicine, University of Buenos Aires (UBA), Buenos Aires 1121, Argentina
| | - Fernanda Ledda
- Division of Molecular and Cellular Neuroscience, Institute of Cell Biology and Neuroscience (IBCN)-CONICET, School of Medicine, University of Buenos Aires (UBA), Buenos Aires 1121, Argentina
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113
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Naito Y, Lee AK, Takahashi H. Emerging roles of the neurotrophin receptor TrkC in synapse organization. Neurosci Res 2016; 116:10-17. [PMID: 27697534 DOI: 10.1016/j.neures.2016.09.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2016] [Revised: 09/18/2016] [Accepted: 09/20/2016] [Indexed: 10/20/2022]
Abstract
Tropomyosin-receptor-kinase (Trk) receptors have been extensively studied for their roles in kinase-dependent signaling cascades in nervous system development. Synapse organization is coordinated by trans-synaptic interactions of various cell adhesion proteins, a representative example of which is the neurexin-neuroligin complex. Recently, a novel role for TrkC as a synapse organizing protein has been established. Post-synaptic TrkC binds to pre-synaptic type-IIa receptor-type protein tyrosine phosphatase sigma (PTPσ). TrkC-PTPσ specifically induces excitatory synapses in a kinase domain-independent manner. TrkC has distinct extracellular domains for PTPσ- and NT-3-binding and thus may bind both ligands simultaneously. Indeed, NT-3 enhances the TrkC-PTPσ interaction, thus facilitating synapse induction at the pre-synaptic side and increasing pre-synaptic vesicle recycling in a kinase-independent fashion. A crystal structure study has revealed the detailed structure of the TrkC-PTPσ complex as well as competitive modulation of TrkC-mediated synaptogenesis by heparan sulfate proteoglycans (HSPGs), which bind the same domain of TrkC as PTPσ. Thus, there is strong evidence supporting a role for the TrkC-PTPσ complex in mechanisms underlying the fine turning of neural connectivity. Furthermore, disruption of the TrkC-PTPσ complex may be the underlying cause of certain psychiatric disorders caused by mutations in the gene encoding TrkC (NTRK3), supporting its role in cognitive functions.
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Affiliation(s)
- Yusuke Naito
- Synapse Development and Plasticity, Institut de Recherches Cliniques de Montréal (IRCM), Montreal, Quebec H2W 1R7, Canada; Integrated Program in Neuroscience, McGill University, Montreal, Quebec H3A 2B4, Canada
| | - Alfred Kihoon Lee
- Synapse Development and Plasticity, Institut de Recherches Cliniques de Montréal (IRCM), Montreal, Quebec H2W 1R7, Canada; Integrated Program in Neuroscience, McGill University, Montreal, Quebec H3A 2B4, Canada
| | - Hideto Takahashi
- Synapse Development and Plasticity, Institut de Recherches Cliniques de Montréal (IRCM), Montreal, Quebec H2W 1R7, Canada; Integrated Program in Neuroscience, McGill University, Montreal, Quebec H3A 2B4, Canada; Department of Medicine, Université de Montréal, Montreal, Quebec H3T 1J4, Canada; Division of Experimental Medicine, McGill University, Montreal, Quebec H3A 1A3, Canada.
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114
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SALM4 suppresses excitatory synapse development by cis-inhibiting trans-synaptic SALM3-LAR adhesion. Nat Commun 2016; 7:12328. [PMID: 27480238 PMCID: PMC4974644 DOI: 10.1038/ncomms12328] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Accepted: 06/23/2016] [Indexed: 12/01/2022] Open
Abstract
Synaptic adhesion molecules regulate various aspects of synapse development, function and plasticity. These functions mainly involve trans-synaptic interactions and positive regulations, whereas cis-interactions and negative regulation are less understood. Here we report that SALM4, a member of the SALM/Lrfn family of synaptic adhesion molecules, suppresses excitatory synapse development through cis inhibition of SALM3, another SALM family protein with synaptogenic activity. Salm4-mutant (Salm4−/−) mice show increased excitatory synapse numbers in the hippocampus. SALM4 cis-interacts with SALM3, inhibits trans-synaptic SALM3 interaction with presynaptic LAR family receptor tyrosine phosphatases and suppresses SALM3-dependent presynaptic differentiation. Importantly, deletion of Salm3 in Salm4−/− mice (Salm3−/−; Salm4−/−) normalizes the increased excitatory synapse number. These results suggest that SALM4 negatively regulates excitatory synapses via cis inhibition of the trans-synaptic SALM3–LAR adhesion. Synaptic adhesion molecules regulate synapse development and function by both cis and trans-interactions. Here, Lie et al. show that postsynaptic SALM4 regulates excitatory synapse numbers by cis inhibition of the SALM3-LAR transynaptic interaction.
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115
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Newell-Litwa KA. Breaking down to build up: Neuroligin's C-terminal domain strengthens the synapse. J Cell Biol 2016; 212:375-7. [PMID: 26880198 PMCID: PMC4754722 DOI: 10.1083/jcb.201601081] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The mechanisms by which neuroligin adhesion molecules modulate synaptic plasticity remain unclear. In this issue, Liu et al. (2016. J. Cell Biol.http://dx.doi.org/10.1083/jcb.201509023) demonstrate that neuroligin 1 promotes actin assembly associated with synaptic strengthening independent of adhesion, suggesting additional ways for neuroligins to contribute to neuronal development and disease pathology.
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Affiliation(s)
- Karen A Newell-Litwa
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA 22908
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116
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Pinto MJ, Almeida RD. Puzzling out presynaptic differentiation. J Neurochem 2016; 139:921-942. [PMID: 27315450 DOI: 10.1111/jnc.13702] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Revised: 05/27/2016] [Accepted: 06/10/2016] [Indexed: 12/24/2022]
Abstract
Proper brain function in the nervous system relies on the accurate establishment of synaptic contacts during development. Countless synapses populate the adult brain in an orderly fashion. In each synapse, a presynaptic terminal loaded with neurotransmitters-containing synaptic vesicles is perfectly aligned to an array of receptors in the postsynaptic membrane. Presynaptic differentiation, which encompasses the events underlying assembly of new presynaptic units, has seen notable advances in recent years. It is now consensual that as a growing axon encounters the receptive dendrites of its partner, presynaptic assembly will be triggered and specified by multiple postsynaptically-derived factors including soluble molecules and cell adhesion complexes. Presynaptic material that reaches these distant sites by axonal transport in the form of pre-assembled packets will be retained and clustered, ultimately giving rise to a presynaptic bouton. This review focuses on the cellular and molecular aspects of presynaptic differentiation in the central nervous system, with a particular emphasis on the identity of the instructive factors and the intracellular processes used by neuronal cells to assemble functional presynaptic terminals. We provide a detailed description of the mechanisms leading to the formation of new presynaptic terminals. In brief, soma-derived packets of pre-assembled material are trafficked to distant axonal sites. Synaptogenic factors from dendritic or glial provenance activate downstream intra-axonal mediators to trigger clustering of passing material and their correct organization into a new presynaptic bouton. This article is part of a mini review series: "Synaptic Function and Dysfunction in Brain Diseases".
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Affiliation(s)
- Maria J Pinto
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,PhD Programme in Experimental Biology and Biomedicine (PDBEB), Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
| | - Ramiro D Almeida
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,School of Allied Health Technologies, Polytechnic Institute of Oporto, Vila Nova de Gaia, Portugal.,Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
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117
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Regulation of GABAergic synapse development by postsynaptic membrane proteins. Brain Res Bull 2016; 129:30-42. [PMID: 27453545 DOI: 10.1016/j.brainresbull.2016.07.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 07/06/2016] [Indexed: 02/07/2023]
Abstract
In the adult mammalian brain, GABAergic neurotransmission provides the majority of synaptic inhibition that balances glutamatergic excitatory drive and thereby controls neuronal output. It is generally accepted that synaptogenesis is initiated through highly specific protein-protein interactions mediated by membrane proteins expressed in developing presynaptic terminals and postsynaptic membranes. Accumulating studies have uncovered a number of membrane proteins that regulate different aspects of GABAergic synapse development. In this review, we summarize recent advances in understanding of GABAergic synapse development with a focus on postsynaptic membrane molecules, including receptors, synaptogenic cell adhesion molecules and immunoglobulin superfamily proteins.
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118
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Pinto MJ, Pedro JR, Costa RO, Almeida RD. Visualizing K48 Ubiquitination during Presynaptic Formation By Ubiquitination-Induced Fluorescence Complementation (UiFC). Front Mol Neurosci 2016; 9:43. [PMID: 27375430 PMCID: PMC4901079 DOI: 10.3389/fnmol.2016.00043] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 05/24/2016] [Indexed: 11/18/2022] Open
Abstract
In recent years, signaling through ubiquitin has been shown to be of great importance for normal brain development. Indeed, fluctuations in ubiquitin levels and spontaneous mutations in (de)ubiquitination enzymes greatly perturb synapse formation and neuronal transmission. In the brain, expression of lysine (K) 48-linked ubiquitin chains is higher at a developmental stage coincident with synaptogenesis. Nevertheless, no studies have so far delved into the involvement of this type of polyubiquitin chains in synapse formation. We have recently proposed a role for polyubiquitinated conjugates as triggering signals for presynaptic assembly. Herein, we aimed at characterizing the axonal distribution of K48 polyubiquitin and its dynamics throughout the course of presynaptic formation. To accomplish so, we used an ubiquitination-induced fluorescence complementation (UiFC) strategy for the visualization of K48 polyubiquitin in live hippocampal neurons. We first validated its use in neurons by analyzing changing levels of polyubiquitin. UiFC signal is diffusely distributed with distinct aggregates in somas, dendrites and axons, which perfectly colocalize with staining for a K48-specific antibody. Axonal UiFC aggregates are relatively stable and new aggregates are formed as an axon grows. Approximately 65% of UiFC aggregates colocalize with synaptic vesicle clusters and they preferentially appear in the axonal domains of axo-somatodendritic synapses when compared to isolated axons. We then evaluated axonal accumulation of K48 ubiquitinated signals in bead-induced synapses. We observed rapid accumulation of UiFC signal and endogenous K48 ubiquitin at the sites of newly formed presynapses. Lastly, we show by means of a microfluidic platform, for the isolation of axons, that presynaptic clustering on beads is dependent on E1-mediated ubiquitination at the axonal level. Altogether, these results indicate that enrichment of K48 polyubiquitin at the site of nascent presynaptic terminals is an important axon-intrinsic event for presynaptic differentiation.
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Affiliation(s)
- Maria J Pinto
- Center for Neuroscience and Cell Biology (CNC), University of CoimbraCoimbra, Portugal; PhD Programme in Experimental Biology and Biomedicine (PDBEB), Center for Neuroscience and Cell Biology, University of CoimbraCoimbra, Portugal
| | - Joana R Pedro
- Center for Neuroscience and Cell Biology (CNC), University of Coimbra Coimbra, Portugal
| | - Rui O Costa
- Center for Neuroscience and Cell Biology (CNC), University of Coimbra Coimbra, Portugal
| | - Ramiro D Almeida
- Center for Neuroscience and Cell Biology (CNC), University of CoimbraCoimbra, Portugal; School of Allied Health Technologies, Polytechnic Institute of Porto (ESTSP-IPP)Vila Nova de Gaia, Portugal; Institute for Interdisciplinary Research, University of CoimbraCoimbra, Portugal
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119
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Zhang C, Caldwell TA, Mirbolooki MR, Duong D, Park EJ, Chi NW, Chessler SD. Extracellular CADM1 interactions influence insulin secretion by rat and human islet β-cells and promote clustering of syntaxin-1. Am J Physiol Endocrinol Metab 2016; 310:E874-85. [PMID: 27072493 PMCID: PMC4935136 DOI: 10.1152/ajpendo.00318.2015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Accepted: 04/08/2016] [Indexed: 11/22/2022]
Abstract
Contact between β-cells is necessary for their normal function. Identification of the proteins mediating the effects of β-cell-to-β-cell contact is a necessary step toward gaining a full understanding of the determinants of β-cell function and insulin secretion. The secretory machinery of the β-cells is nearly identical to that of central nervous system (CNS) synapses, and we hypothesize that the transcellular protein interactions that drive maturation of the two secretory machineries upon contact of one cell (or neural process) with another are also highly similar. Two such transcellular interactions, important for both synaptic and β-cell function, have been identified: EphA/ephrin-A and neuroligin/neurexin. Here, we tested the role of another synaptic cleft protein, CADM1, in insulinoma cells and in rat and human islet β-cells. We found that CADM1 is a predominant CADM isoform in β-cells. In INS-1 cells and primary β-cells, CADM1 constrains insulin secretion, and its expression decreases after prolonged glucose stimulation. Using a coculture model, we found that CADM1 also influences insulin secretion in a transcellular manner. We asked whether extracellular CADM1 interactions exert their influence via the same mechanisms by which they influence neurotransmitter exocytosis. Our results suggest that, as in the CNS, CADM1 interactions drive exocytic site assembly and promote actin network formation. These results support the broader hypothesis that the effects of cell-cell contact on β-cell maturation and function are mediated by the same extracellular protein interactions that drive the formation of the presynaptic exocytic machinery. These interactions may be therapeutic targets for reversing β-cell dysfunction in diabetes.
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Affiliation(s)
- Charles Zhang
- Department of Medicine, University of California, Irvine, School of Medicine, Irvine, California
| | - Thomas A Caldwell
- Department of Medicine, University of California, Irvine, School of Medicine, Irvine, California
| | - M Reza Mirbolooki
- Department of Medicine, University of California, Irvine, School of Medicine, Irvine, California
| | - Diana Duong
- Pediatric Diabetes Research Center, University of California San Diego, La Jolla, California; and
| | - Eun Jee Park
- Department of Medicine, University of California, Irvine, School of Medicine, Irvine, California
| | - Nai-Wen Chi
- Research Service, Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Steven D Chessler
- Department of Medicine, University of California, Irvine, School of Medicine, Irvine, California;
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120
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Choi Y, Nam J, Whitcomb DJ, Song YS, Kim D, Jeon S, Um JW, Lee SG, Woo J, Kwon SK, Li Y, Mah W, Kim HM, Ko J, Cho K, Kim E. SALM5 trans-synaptically interacts with LAR-RPTPs in a splicing-dependent manner to regulate synapse development. Sci Rep 2016; 6:26676. [PMID: 27225731 PMCID: PMC4881023 DOI: 10.1038/srep26676] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 05/04/2016] [Indexed: 11/08/2022] Open
Abstract
Synaptogenic adhesion molecules play critical roles in synapse formation. SALM5/Lrfn5, a SALM/Lrfn family adhesion molecule implicated in autism spectrum disorders (ASDs) and schizophrenia, induces presynaptic differentiation in contacting axons, but its presynaptic ligand remains unknown. We found that SALM5 interacts with the Ig domains of LAR family receptor protein tyrosine phosphatases (LAR-RPTPs; LAR, PTPδ, and PTPσ). These interactions are strongly inhibited by the splice insert B in the Ig domain region of LAR-RPTPs, and mediate SALM5-dependent presynaptic differentiation in contacting axons. In addition, SALM5 regulates AMPA receptor-mediated synaptic transmission through mechanisms involving the interaction of postsynaptic SALM5 with presynaptic LAR-RPTPs. These results suggest that postsynaptic SALM5 promotes synapse development by trans-synaptically interacting with presynaptic LAR-RPTPs and is important for the regulation of excitatory synaptic strength.
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Affiliation(s)
- Yeonsoo Choi
- Department of Biological Sciences, Korea Advanced Institute for Science and Technology (KAIST), Daejeon 305-701, Korea
| | - Jungyong Nam
- Department of Biological Sciences, Korea Advanced Institute for Science and Technology (KAIST), Daejeon 305-701, Korea
| | - Daniel J. Whitcomb
- Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, School of Clinical Sciences, Faculty of Health Sciences, University of Bristol, Whitson Street, Bristol BS1 3NY, United Kingdom
| | - Yoo Sung Song
- Department of Nuclear Medicine, Seoul National University Bundang Hospital, Gyeonggi-do, 463–707, Korea
| | - Doyoun Kim
- Center for Synaptic Brain Dysfunctions, Institute for Basic Science (IBS), Daejeon 305-701, Korea
| | - Sangmin Jeon
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Korea
| | - Ji Won Um
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Korea
- Department of Physiology and BK21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul 120-752, Korea
| | - Seong-Gyu Lee
- Department of Biological Sciences, Korea Advanced Institute for Science and Technology (KAIST), Daejeon 305-701, Korea
| | - Jooyeon Woo
- Department of Biological Sciences, Korea Advanced Institute for Science and Technology (KAIST), Daejeon 305-701, Korea
| | - Seok-Kyu Kwon
- Department of Biological Sciences, Korea Advanced Institute for Science and Technology (KAIST), Daejeon 305-701, Korea
| | - Yan Li
- Center for Synaptic Brain Dysfunctions, Institute for Basic Science (IBS), Daejeon 305-701, Korea
| | - Won Mah
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, Korea
| | - Ho Min Kim
- Graduate School of Medical Science and Engineering, KAIST, Daejeon 305-701, Korea
| | - Jaewon Ko
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Korea
| | - Kwangwook Cho
- Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, School of Clinical Sciences, Faculty of Health Sciences, University of Bristol, Whitson Street, Bristol BS1 3NY, United Kingdom
- Centre for Synaptic Plasticity, University of Bristol, Bristol BS1 3NY, United Kingdom
| | - Eunjoon Kim
- Department of Biological Sciences, Korea Advanced Institute for Science and Technology (KAIST), Daejeon 305-701, Korea
- Center for Synaptic Brain Dysfunctions, Institute for Basic Science (IBS), Daejeon 305-701, Korea
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121
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Brown LE, Nicholson MW, Arama JE, Mercer A, Thomson AM, Jovanovic JN. γ-Aminobutyric Acid Type A (GABAA) Receptor Subunits Play a Direct Structural Role in Synaptic Contact Formation via Their N-terminal Extracellular Domains. J Biol Chem 2016; 291:13926-13942. [PMID: 27129275 PMCID: PMC4933154 DOI: 10.1074/jbc.m116.714790] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Indexed: 11/17/2022] Open
Abstract
The establishment of cell-cell contacts between presynaptic GABAergic neurons and their postsynaptic targets initiates the process of GABAergic synapse formation. GABAA receptors (GABAARs), the main postsynaptic receptors for GABA, have been recently demonstrated to act as synaptogenic proteins that can single-handedly induce the formation and functional maturation of inhibitory synapses. To establish how the subunit composition of GABAARs influences their ability to induce synaptogenesis, a co-culture model system incorporating GABAergic medium spiny neurons and the HEK293 cells, stably expressing different combinations of receptor subunits, was developed. Analyses of HEK293 cell innervation by medium spiny neuron axons using immunocytochemistry, activity-dependent labeling, and electrophysiology have indicated that the γ2 subunit is required for the formation of active synapses and that its effects are influenced by the type of α/β subunits incorporated into the functional receptor. To further characterize this process, the large N-terminal extracellular domains (ECDs) of α1, α2, β2, and γ2 subunits were purified using the baculovirus/Sf9 cell system. When these proteins were applied to the co-cultures of MSNs and α1/β2/γ2-expressing HEK293 cells, the α1, β2, or γ2 ECD each caused a significant reduction in contact formation, in contrast to the α2 ECD, which had no effect. Together, our experiments indicate that the structural role of GABAARs in synaptic contact formation is determined by their subunit composition, with the N-terminal ECDs of each of the subunits directly participating in interactions between the presynaptic and postsynaptic elements, suggesting the these interactions are multivalent and specific.
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Affiliation(s)
- Laura E Brown
- Research Department of Pharmacology, UCL School of Pharmacy, University College London, London WC1N 1AX, United Kingdom
| | - Martin W Nicholson
- Research Department of Pharmacology, UCL School of Pharmacy, University College London, London WC1N 1AX, United Kingdom
| | - Jessica E Arama
- Research Department of Pharmacology, UCL School of Pharmacy, University College London, London WC1N 1AX, United Kingdom
| | - Audrey Mercer
- Research Department of Pharmacology, UCL School of Pharmacy, University College London, London WC1N 1AX, United Kingdom
| | - Alex M Thomson
- Research Department of Pharmacology, UCL School of Pharmacy, University College London, London WC1N 1AX, United Kingdom
| | - Jasmina N Jovanovic
- Research Department of Pharmacology, UCL School of Pharmacy, University College London, London WC1N 1AX, United Kingdom.
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122
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Terauchi A, Johnson-Venkatesh EM, Bullock B, Lehtinen MK, Umemori H. Retrograde fibroblast growth factor 22 (FGF22) signaling regulates insulin-like growth factor 2 (IGF2) expression for activity-dependent synapse stabilization in the mammalian brain. eLife 2016; 5. [PMID: 27083047 PMCID: PMC4868541 DOI: 10.7554/elife.12151] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 04/14/2016] [Indexed: 02/06/2023] Open
Abstract
Communication between pre- and postsynaptic cells promotes the initial organization of synaptic specializations, but subsequent synaptic stabilization requires transcriptional regulation. Here we show that fibroblast growth factor 22 (FGF22), a target-derived presynaptic organizer in the mouse hippocampus, induces the expression of insulin-like growth factor 2 (IGF2) for the stabilization of presynaptic terminals. FGF22 is released from CA3 pyramidal neurons and organizes the differentiation of excitatory nerve terminals formed onto them. Local application of FGF22 on the axons of dentate granule cells (DGCs), which are presynaptic to CA3 pyramidal neurons, induces IGF2 in the DGCs. IGF2, in turn, localizes to DGC presynaptic terminals and stabilizes them in an activity-dependent manner. IGF2 application rescues presynaptic defects of Fgf22(-/-) cultures. IGF2 is dispensable for the initial presynaptic differentiation, but is required for the following presynaptic stabilization both in vitro and in vivo. These results reveal a novel feedback signal that is critical for the activity-dependent stabilization of presynaptic terminals in the mammalian hippocampus.
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Affiliation(s)
- Akiko Terauchi
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, United States
| | - Erin M Johnson-Venkatesh
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, United States
| | - Brenna Bullock
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, United States
| | - Maria K Lehtinen
- Department of Pathology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, United States
| | - Hisashi Umemori
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, United States
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123
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Hayashi Y, Nishimune H, Hozumi K, Saga Y, Harada A, Yuzaki M, Iwatsubo T, Kopan R, Tomita T. A novel non-canonical Notch signaling regulates expression of synaptic vesicle proteins in excitatory neurons. Sci Rep 2016; 6:23969. [PMID: 27040987 PMCID: PMC4819173 DOI: 10.1038/srep23969] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 03/17/2016] [Indexed: 12/17/2022] Open
Abstract
Notch signaling plays crucial roles for cellular differentiation during development through γ-secretase-dependent intramembrane proteolysis followed by transcription of target genes. Although recent studies implicate that Notch regulates synaptic plasticity or cognitive performance, the molecular mechanism how Notch works in mature neurons remains uncertain. Here we demonstrate that a novel Notch signaling is involved in expression of synaptic proteins in postmitotic neurons. Levels of several synaptic vesicle proteins including synaptophysin 1 and VGLUT1 were increased when neurons were cocultured with Notch ligands-expressing NIH3T3 cells. Neuron-specific deletion of Notch genes decreased these proteins, suggesting that Notch signaling maintains the expression of synaptic vesicle proteins in a cell-autonomous manner. Unexpectedly, cGMP-dependent protein kinase (PKG) inhibitor, but not γ-secretase inhibitor, abolished the elevation of synaptic vesicle proteins, suggesting that generation of Notch intracellular domain is dispensable for this function. These data uncover a ligand-dependent, but γ-secretase-independent, non-canonical Notch signaling involved in presynaptic protein expression in postmitotic neurons.
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Affiliation(s)
- Yukari Hayashi
- Laboratory of Neuropathology and Neuroscience, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan.,Department of Physiology, School of Medicine, Keio University, Tokyo 160-8582, Japan
| | - Hiroshi Nishimune
- Department of Anatomy and Cell Biology, University of Kansas Medical School, Kansas City, KS 66160, USA
| | - Katsuto Hozumi
- Department of Immunology, Tokai University School of Medicine, Kanagawa 259-1193, Japan
| | - Yumiko Saga
- Division of Mammalian Development, National Institute of Genetics, Shizuoka 411-8540, Japan.,Department of Genetics, SOKENDAI, Shizuoka 411-8540, Japan
| | - Akihiro Harada
- Department of Cell Biology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
| | - Michisuke Yuzaki
- Department of Physiology, School of Medicine, Keio University, Tokyo 160-8582, Japan
| | - Takeshi Iwatsubo
- Department of Neuropathology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Raphael Kopan
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO 63110, USA.,Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA
| | - Taisuke Tomita
- Laboratory of Neuropathology and Neuroscience, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan.,Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO 63110, USA
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124
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Yagensky O, Kalantary Dehaghi T, Chua JJE. The Roles of Microtubule-Based Transport at Presynaptic Nerve Terminals. Front Synaptic Neurosci 2016; 8:3. [PMID: 26903856 PMCID: PMC4748046 DOI: 10.3389/fnsyn.2016.00003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Accepted: 01/29/2016] [Indexed: 01/19/2023] Open
Abstract
Targeted intracellular movement of presynaptic proteins plays important roles during synapse formation and, later, in the homeostatic maintenance of mature synapses. Movement of these proteins, often as vesicular packages, is mediated by motor complexes travelling along intracellular cytoskeletal networks. Presynaptic protein transport by kinesin motors in particular plays important roles during synaptogenesis to bring newly synthesized proteins to establish nascent synaptic sites. Conversely, movement of proteins away from presynaptic sites by Dynein motors enables synapse-nuclear signaling and allows for synaptic renewal through degradation of unwanted or damaged proteins. Remarkably, recent data has indicated that synaptic and protein trafficking machineries can modulate each other's functions. Here, we survey the mechanisms involved in moving presynaptic components to and away from synapses and how this process supports presynaptic function.
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Affiliation(s)
- Oleksandr Yagensky
- Research Group Protein Trafficking in Synaptic Development and Function, Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry Göttingen, Germany
| | - Tahere Kalantary Dehaghi
- Research Group Protein Trafficking in Synaptic Development and Function, Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry Göttingen, Germany
| | - John Jia En Chua
- Research Group Protein Trafficking in Synaptic Development and Function, Department of Neurobiology, Max-Planck-Institute for Biophysical ChemistryGöttingen, Germany; Interactomics and Intracellular Trafficking Laboratory, Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, SingaporeSingapore; Neurobiology/Ageing Programme, National University of Singapore, SingaporeSingapore
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125
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Gundelfinger ED, Reissner C, Garner CC. Role of Bassoon and Piccolo in Assembly and Molecular Organization of the Active Zone. Front Synaptic Neurosci 2016; 7:19. [PMID: 26793095 PMCID: PMC4709825 DOI: 10.3389/fnsyn.2015.00019] [Citation(s) in RCA: 104] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Accepted: 12/14/2015] [Indexed: 01/05/2023] Open
Abstract
Bassoon and Piccolo are two very large scaffolding proteins of the cytomatrix assembled at the active zone (CAZ) where neurotransmitter is released. They share regions of high sequence similarity distributed along their entire length and seem to share both overlapping and distinct functions in organizing the CAZ. Here, we survey our present knowledge on protein-protein interactions and recent progress in understanding of molecular functions of these two giant proteins. These include roles in the assembly of active zones (AZ), the localization of voltage-gated Ca2+ channels (VGCCs) in the vicinity of release sites, synaptic vesicle (SV) priming and in the case of Piccolo, a role in the dynamic assembly of the actin cytoskeleton. Piccolo and Bassoon are also important for the maintenance of presynaptic structure and function, as well as for the assembly of CAZ specializations such as synaptic ribbons. Recent findings suggest that they are also involved in the regulation activity-dependent communication between presynaptic boutons and the neuronal nucleus. Together these observations suggest that Bassoon and Piccolo use their modular structure to organize super-molecular complexes essential for various aspects of presynaptic function.
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Affiliation(s)
- Eckart D Gundelfinger
- Department Neurochemistry and Molecular Biology, Leibniz Institute for NeurobiologyMagdeburg, Germany; Center for Behavioral Brain SciencesMagdeburg, Germany; Medical Faculty, Otto von Guericke UniversityMagdeburg, Germany; German Center for Neurodegenerative Diseases (DZNE) Site MagdeburgMagdeburg, Germany
| | - Carsten Reissner
- Institute of Anatomy and Molecular Neurobiology, Westfälische Wilhelms University Münster, Germany
| | - Craig C Garner
- German Center for Neurodegenerative Diseases (DZNE) Site BerlinBerlin, Germany; Charité Medical UniversityBerlin, Germany
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126
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Gu X, Zhou L, Lu W. An NMDA Receptor-Dependent Mechanism Underlies Inhibitory Synapse Development. Cell Rep 2016; 14:471-478. [PMID: 26774487 DOI: 10.1016/j.celrep.2015.12.061] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Revised: 11/09/2015] [Accepted: 12/10/2015] [Indexed: 10/22/2022] Open
Abstract
In the mammalian brain, GABAergic synaptic transmission provides inhibitory balance to glutamatergic excitatory drive and controls neuronal output. The molecular mechanisms underlying the development of GABAergic synapses remain largely unclear. Here, we report that NMDA-type ionotropic glutamate receptors (NMDARs) in individual immature neurons are the upstream signaling molecules essential for GABAergic synapse development, which requires signaling via Calmodulin binding motif in the C0 domain of the NMDAR GluN1 subunit. Interestingly, in neurons lacking NMDARs, whereas GABAergic synaptic transmission is strongly reduced, the tonic inhibition mediated by extrasynaptic GABAA receptors is increased, suggesting a compensatory mechanism for the lack of synaptic inhibition. These results demonstrate a crucial role for NMDARs in specifying the development of inhibitory synapses, and suggest an important mechanism for controlling the establishment of the balance between synaptic excitation and inhibition in the developing brain.
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Affiliation(s)
- Xinglong Gu
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 35 Convent Drive, 3C1000, Bethesda, MD 20892, USA
| | - Liang Zhou
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 35 Convent Drive, 3C1000, Bethesda, MD 20892, USA
| | - Wei Lu
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 35 Convent Drive, 3C1000, Bethesda, MD 20892, USA.
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127
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Neurotrophin-3 Enhances the Synaptic Organizing Function of TrkC-Protein Tyrosine Phosphatase σ in Rat Hippocampal Neurons. J Neurosci 2015; 35:12425-31. [PMID: 26354911 DOI: 10.1523/jneurosci.1330-15.2015] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neurotrophin-3 (NT-3) and its high-affinity receptor TrkC play crucial trophic roles in neuronal differentiation, axon outgrowth, and synapse development and plasticity in the nervous system. We demonstrated previously that postsynaptic TrkC functions as a glutamatergic synapse-inducing (synaptogenic) cell adhesion molecule trans-interacting with presynaptic protein tyrosine phosphatase σ (PTPσ). Given that NT-3 and PTPσ bind distinct domains of the TrkC extracellular region, here we tested the hypothesis that NT-3 modulates TrkC/PTPσ binding and synaptogenic activity. NT-3 enhanced PTPσ binding to cell surface-expressed TrkC and facilitated the presynapse-inducing activity of TrkC in rat hippocampal neurons. Imaging of recycling presynaptic vesicles combined with TrkC knockdown and rescue approaches demonstrated that NT-3 rapidly potentiates presynaptic function via binding endogenous postsynaptic TrkC in a tyrosine kinase-independent manner. Thus, NT-3 positively modulates the TrkC-PTPσ complex for glutamatergic presynaptic assembly and function independently from TrkC kinase activation. Our findings provide new insight into synaptic roles of neurotrophin signaling and mechanisms controlling synaptic organizing complexes. Significance statement: Although many synaptogenic adhesion complexes have been identified in recent years, little is known about modulatory mechanisms. Here, we demonstrate a novel role of neurotrophin-3 in synaptic assembly and function as a positive modulator of the TrkC-protein tyrosine phosphatase σ complex. This study provides new insight into the involvement of neurotrophin signaling in synapse development and plasticity, presenting a molecular mechanism that may underlie previous observations of short- and long-term enhancement of presynaptic function by neurotrophin. Given the links of synaptogenic adhesion molecules to autism and schizophrenia, this study might also contribute to a better understanding of the pathogenesis of these disorders and provide a new direction for ameliorating imbalances in synaptic signaling networks.
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128
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de Wit J, Ghosh A. Specification of synaptic connectivity by cell surface interactions. Nat Rev Neurosci 2015; 17:22-35. [PMID: 26656254 DOI: 10.1038/nrn.2015.3] [Citation(s) in RCA: 192] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The molecular diversification of cell surface molecules has long been postulated to impart specific surface identities on neuronal cell types. The existence of unique cell surface identities would allow neurons to distinguish one another and connect with their appropriate target cells. Although progress has been made in identifying cell type-specific surface molecule repertoires and in characterizing their extracellular interactions, determining how this molecular diversity contributes to the precise wiring of neural circuitry has proven challenging. Here, we review the role of the cadherin, neurexin, immunoglobulin and leucine-rich repeat protein superfamilies in the specification of connectivity. The emerging evidence suggests that the concerted actions of these proteins may critically contribute to the assembly of neural circuits.
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Affiliation(s)
- Joris de Wit
- VIB Center for the Biology of Disease and Center for Human Genetics, KU Leuven, Herestraat 49, 3000 Leuven, Belgium
| | - Anirvan Ghosh
- Neuroscience Discovery, Roche Innovation Center Basel, F. Hoffman-La Roche, Grenzacherstrasse 124, 4070 Basel, Switzerland
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129
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Shinoe T, Goda Y. Tuning synapses by proteolytic remodeling of the adhesive surface. Curr Opin Neurobiol 2015; 35:148-55. [DOI: 10.1016/j.conb.2015.08.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 07/17/2015] [Accepted: 08/04/2015] [Indexed: 10/23/2022]
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130
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Tyleckova J, Valekova I, Zizkova M, Rakocyova M, Marsala S, Marsala M, Gadher SJ, Kovarova H. Surface N-glycoproteome patterns reveal key proteins of neuronal differentiation. J Proteomics 2015; 132:13-20. [PMID: 26581640 DOI: 10.1016/j.jprot.2015.11.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 09/03/2015] [Accepted: 11/09/2015] [Indexed: 01/23/2023]
Abstract
UNLABELLED Pluripotent stem cell-derived committed neural precursors are an important source of cells to treat neurodegenerative diseases including spinal cord injury. There remains an urgency to identify markers for monitoring of neural progenitor specificity, estimation of neural fate and follow-up correlation with therapeutic effect in preclinical studies using animal disease models. Cell surface capture technology was used to uncover the cell surface exposed N-glycoproteome of neural precursor cells upon neuronal differentiation as well as post-mitotic mature hNT neurons. The data presented depict an extensive study of surfaceome during neuronal differentiation, confirming glycosylation at a particular predicted site of many of the identified proteins. Quantitative changes detected in cell surface protein levels reveal a set of proteins that highlight the complexity of the neuronal differentiation process. Several of these proteins including the cell adhesion molecules ICAM1, CHL1, and astrotactin1 as well as LAMP1 were validated by SRM. Combination of immunofluorescence staining of ICAM1 and flow cytometry indicated a possible direction for future scrutiny of such proteins as targets for enrichment of the neuronal subpopulation from mixed cultures after differentiation of neural precursor cells. These surface proteins hold an important key for development of safe strategies in cell-replacement therapies of neuronal disorders. BIOLOGICAL SIGNIFICANCE Neural stem and/or precursor cells have a great potential for cell-replacement therapies of neuronal diseases. Availability of well characterised and expandable neural cell lineage specific populations is critical for addressing such a challenge. In our study we identified and relatively quantified several hundred surface N-glycoproteins in the course of neuronal differentiation. We further confirmed the abundant changes for several cell adhesion proteins by SRM and outlined a strategy for utilisation of such N-glycoproteins in antibody based cell sorting. The comprehensive dataset presented here demonstrates the molecular background of neuronal differentiation highly useful for development of new plasma membrane markers to identify and select neuronal subpopulation from mixed neural cell cultures.
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Affiliation(s)
- Jirina Tyleckova
- Institute of Animal Physiology and Genetics, Academy of Sciences of the Czech Republic, Laboratory of Applied Proteome Analyses, Libechov, CZ 27721, Czech Republic; Research Center PIGMOD, Laboratory of Applied Proteome Analyses, Libechov, CZ 27721, Czech Republic
| | - Ivona Valekova
- Institute of Animal Physiology and Genetics, Academy of Sciences of the Czech Republic, Laboratory of Applied Proteome Analyses, Libechov, CZ 27721, Czech Republic; Research Center PIGMOD, Laboratory of Applied Proteome Analyses, Libechov, CZ 27721, Czech Republic; Department of Cell Biology, Faculty of Science, Charles University, CZ 128 43 Prague, Czech Republic
| | - Martina Zizkova
- Institute of Animal Physiology and Genetics, Academy of Sciences of the Czech Republic, Laboratory of Applied Proteome Analyses, Libechov, CZ 27721, Czech Republic; Research Center PIGMOD, Laboratory of Applied Proteome Analyses, Libechov, CZ 27721, Czech Republic; Department of Cell Biology, Faculty of Science, Charles University, CZ 128 43 Prague, Czech Republic
| | - Michaela Rakocyova
- Institute of Animal Physiology and Genetics, Academy of Sciences of the Czech Republic, Laboratory of Applied Proteome Analyses, Libechov, CZ 27721, Czech Republic; Research Center PIGMOD, Laboratory of Applied Proteome Analyses, Libechov, CZ 27721, Czech Republic
| | - Silvia Marsala
- University of California, San Diego, Department of Anesthesiology, Neuroregeneration Laboratory, Sanford Consortium for Regenerative Medicine, La Jolla, CA-92037, USA
| | - Martin Marsala
- University of California, San Diego, Department of Anesthesiology, Neuroregeneration Laboratory, Sanford Consortium for Regenerative Medicine, La Jolla, CA-92037, USA
| | | | - Hana Kovarova
- Institute of Animal Physiology and Genetics, Academy of Sciences of the Czech Republic, Laboratory of Applied Proteome Analyses, Libechov, CZ 27721, Czech Republic; Research Center PIGMOD, Laboratory of Applied Proteome Analyses, Libechov, CZ 27721, Czech Republic.
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131
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Splicing-Dependent Trans-synaptic SALM3-LAR-RPTP Interactions Regulate Excitatory Synapse Development and Locomotion. Cell Rep 2015; 12:1618-30. [PMID: 26321637 PMCID: PMC4578660 DOI: 10.1016/j.celrep.2015.08.002] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 06/10/2015] [Accepted: 07/31/2015] [Indexed: 12/02/2022] Open
Abstract
Synaptic adhesion molecules regulate diverse aspects of synapse development and plasticity. SALM3 is a PSD-95-interacting synaptic adhesion molecule known to induce presynaptic differentiation in contacting axons, but little is known about its presynaptic receptors and in vivo functions. Here, we identify an interaction between SALM3 and LAR family receptor protein tyrosine phosphatases (LAR-RPTPs) that requires the mini-exon B splice insert in LAR-RPTPs. In addition, SALM3-dependent presynaptic differentiation requires all three types of LAR-RPTPs. SALM3 mutant (Salm3−/−) mice display markedly reduced excitatory synapse number but normal synaptic plasticity in the hippocampal CA1 region. Salm3−/− mice exhibit hypoactivity in both novel and familiar environments but perform normally in learning and memory tests administered. These results suggest that SALM3 regulates excitatory synapse development and locomotion behavior.
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132
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Abstract
The mechanisms mediating the appropriate clustering of neurotransmitter receptors opposite release sites are poorly understood. Two studies in this issue of Neuron, Maro et al. (2015) and Tu et al. (2015), identify a new extracellular effector for neuroligin in GABAergic postsynaptic differentiation.
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Affiliation(s)
- Peng Zhang
- Brain Research Centre and Department of Psychiatry, University of British Columbia, Vancouver, BC V6T 2B5, Canada
| | - Ann Marie Craig
- Brain Research Centre and Department of Psychiatry, University of British Columbia, Vancouver, BC V6T 2B5, Canada.
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133
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Choi SY, Han K, Cutforth T, Chung W, Park H, Lee D, Kim R, Kim MH, Choi Y, Shen K, Kim E. Mice lacking the synaptic adhesion molecule Neph2/Kirrel3 display moderate hyperactivity and defective novel object preference. Front Cell Neurosci 2015; 9:283. [PMID: 26283919 PMCID: PMC4517382 DOI: 10.3389/fncel.2015.00283] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Accepted: 07/10/2015] [Indexed: 11/13/2022] Open
Abstract
Synaptic adhesion molecules regulate diverse aspects of neuronal synapse development, including synapse specificity, formation, and maturation. Neph2, also known as Kirrel3, is an immunoglobulin superfamily adhesion molecule implicated in intellectual disability, neurocognitive delay associated with Jacobsen syndrome, and autism spectrum disorders. We here report mice lacking Neph2 (Neph2(-/-) mice) display moderate hyperactivity in a familiar, but not novel, environment and defective novel object recognition with normal performances in Morris water maze spatial learning and memory, contextual fear conditioning and extinction, and pattern separation tests. These mice also show normal levels of anxiety-like behaviors, social interaction, and repetitive behaviors. At the synapse level, Neph2(-/-) dentate gyrus granule cells exhibit unaltered dendritic spine density and spontaneous excitatory synaptic transmission. These results suggest that Neph2 is important for normal locomotor activity and object recognition memory.
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Affiliation(s)
- Su-Yeon Choi
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology Daejeon, South Korea
| | - Kihoon Han
- Department of Neuroscience and Division of Brain Korea 21, Biomedical Science, College of Medicine, Korea University Seoul, South Korea
| | - Tyler Cutforth
- Department of Neurology, Columbia University Medical Center New York, NY, USA
| | - Woosuk Chung
- Department of Biomedical Sciences, Graduate School of Medical Science and Engineering, Korea Advanced Institute of Science and Technology Daejeon, South Korea
| | - Haram Park
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology Daejeon, South Korea
| | - Dongsoo Lee
- Center for Synaptic Brain Dysfunctions, Institute for Basic Science Daejeon, South Korea
| | - Ryunhee Kim
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology Daejeon, South Korea
| | - Myeong-Heui Kim
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology Daejeon, South Korea
| | - Yeeun Choi
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology Daejeon, South Korea
| | - Kang Shen
- Department of Biology, Stanford University Stanford, CA, USA ; Howard Hughes Medical Institute Chevy Chase, MD, USA
| | - Eunjoon Kim
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology Daejeon, South Korea ; Center for Synaptic Brain Dysfunctions, Institute for Basic Science Daejeon, South Korea
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134
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The LGI1-ADAM22 protein complex directs synapse maturation through regulation of PSD-95 function. Proc Natl Acad Sci U S A 2015; 112:E4129-37. [PMID: 26178195 DOI: 10.1073/pnas.1511910112] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Synapse development is coordinated by a number of transmembrane and secreted proteins that come together to form synaptic organizing complexes. Whereas a variety of synaptogenic proteins have been characterized, much less is understood about the molecular networks that support the maintenance and functional maturation of nascent synapses. Here, we demonstrate that leucine-rich, glioma-inactivated protein 1 (LGI1), a secreted protein previously shown to modulate synaptic AMPA receptors, is a paracrine signal released from pre- and postsynaptic neurons that acts specifically through a disintegrin and metalloproteinase protein 22 (ADAM22) to set postsynaptic strength. We go on to describe a novel role for ADAM22 in maintaining excitatory synapses through PSD-95/Dlg1/zo-1 (PDZ) domain interactions. Finally, we show that in the absence of LGI1, the mature synapse scaffolding protein PSD-95, but not the immature synapse scaffolding protein SAP102, is unable to modulate synaptic transmission. These results indicate that LGI1 and ADAM22 form an essential synaptic organizing complex that coordinates the maturation of excitatory synapses by regulating the functional incorporation of PSD-95.
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135
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Dayer AG, Jacobshagen M, Chaumont-Dubel S, Marin P. 5-HT6 Receptor: A New Player Controlling the Development of Neural Circuits. ACS Chem Neurosci 2015; 6:951-60. [PMID: 25590789 DOI: 10.1021/cn500326z] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
5-HT6 receptor (5-HT6R) is a G protein-coupled receptor that has recently emerged as a new regulator of neural development. In addition to the canonical Gs adenylyl cyclase pathway, recent proteomics approaches reveal that 5-HT6R is able to engage key developmental signaling pathways controlling neuronal circuit formation, neuronal connectivity, and psychiatric-relevant behaviors. For example, at early stages of neuronal development, expression of 5-HT6R constitutively regulates the activity of the cyclin-dependent kinase (Cdk)5 and, through this mechanism, controls cellular processes involved in circuit formation, including neuronal migration and neurite outgrowth. In addition to the Cdk5 pathway, 5-HT6R modulates a variety of key developmental targets such as Fyn, Jab1, and mammalian target of rapamycin (mTOR). Engagement of developmental pathways through 5-HT6R pharmacological manipulation has led to interesting new therapeutic perspectives in the field of psychiatric-related disorders. Indeed, 5-HT6R blockade can rescue a pathological overactivation of the mTOR pathway induced by early life insults in rodents and normalizes the associated social and episodic memory deficits. Here, we review recent evidence supporting the notion that 5-HT6R is at the interface of key developmental signaling pathways and a novel actor in the orchestration of neural circuit formation.
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Affiliation(s)
| | | | - Séverine Chaumont-Dubel
- Institut de Génomique Fonctionnelle, CNRS UMR 5203, INSERM U661, Universités Montpellier I & II, 34094 Montpellier, France
| | - Philippe Marin
- Institut de Génomique Fonctionnelle, CNRS UMR 5203, INSERM U661, Universités Montpellier I & II, 34094 Montpellier, France
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136
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Ackermann F, Waites CL, Garner CC. Presynaptic active zones in invertebrates and vertebrates. EMBO Rep 2015; 16:923-38. [PMID: 26160654 DOI: 10.15252/embr.201540434] [Citation(s) in RCA: 92] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 06/19/2015] [Indexed: 11/09/2022] Open
Abstract
The regulated release of neurotransmitter occurs via the fusion of synaptic vesicles (SVs) at specialized regions of the presynaptic membrane called active zones (AZs). These regions are defined by a cytoskeletal matrix assembled at AZs (CAZ), which functions to direct SVs toward docking and fusion sites and supports their maturation into the readily releasable pool. In addition, CAZ proteins localize voltage-gated Ca(2+) channels at SV release sites, bringing the fusion machinery in close proximity to the calcium source. Proteins of the CAZ therefore ensure that vesicle fusion is temporally and spatially organized, allowing for the precise and reliable release of neurotransmitter. Importantly, AZs are highly dynamic structures, supporting presynaptic remodeling, changes in neurotransmitter release efficacy, and thus presynaptic forms of plasticity. In this review, we discuss recent advances in the study of active zones, highlighting how the CAZ molecularly defines sites of neurotransmitter release, endocytic zones, and the integrity of synapses.
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Affiliation(s)
- Frauke Ackermann
- German Center for Neurodegenerative Disease, Charité Medical University, Berlin, Germany
| | - Clarissa L Waites
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Craig C Garner
- German Center for Neurodegenerative Disease, Charité Medical University, Berlin, Germany
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137
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C. elegans Punctin Clusters GABAA Receptors via Neuroligin Binding and UNC-40/DCC Recruitment. Neuron 2015; 86:1407-19. [DOI: 10.1016/j.neuron.2015.05.013] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Revised: 02/13/2015] [Accepted: 03/27/2015] [Indexed: 12/21/2022]
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138
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Maro GS, Gao S, Olechwier AM, Hung WL, Liu M, Özkan E, Zhen M, Shen K. MADD-4/Punctin and Neurexin Organize C. elegans GABAergic Postsynapses through Neuroligin. Neuron 2015; 86:1420-32. [PMID: 26028574 DOI: 10.1016/j.neuron.2015.05.015] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Revised: 04/07/2015] [Accepted: 05/01/2015] [Indexed: 11/29/2022]
Abstract
At synapses, the presynaptic release machinery is precisely juxtaposed to the postsynaptic neurotransmitter receptors. We studied the molecular mechanisms underlying this exquisite alignment at the C. elegans inhibitory synapses. We found that the sole C. elegans neuroligin homolog, NLG-1, localizes specifically at GABAergic postsynapses and is required for clustering the GABA(A) receptor UNC-49. Two presynaptic factors, Punctin/MADD-4, an ADAMTS-like extracellular protein, and neurexin/NRX-1, act partially redundantly to recruit NLG-1 to synapses. In the absence of both MADD-4 and NRX-1, NLG-1 and GABA(A) receptors fail to cluster, and GABAergic synaptic transmission is severely compromised. Biochemically, we detect an interaction between MADD-4 and NLG-1, as well as between MADD-4 and NRX-1. Interestingly, the presence of NRX-1 potentiates binding between Punctin/MADD-4 and NLG-1, suggestive of a tripartite receptor ligand complex. We propose that presynaptic terminals induce postsynaptic receptor clustering through the action of both secreted ECM proteins and trans-synaptic adhesion complexes.
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Affiliation(s)
- Géraldine S Maro
- Howard Hughes Medical Institute, Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Shangbang Gao
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON M5G1X5, Canada
| | - Agnieszka M Olechwier
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637, USA
| | - Wesley L Hung
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON M5G1X5, Canada
| | - Michael Liu
- Howard Hughes Medical Institute, Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Engin Özkan
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637, USA
| | - Mei Zhen
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON M5G1X5, Canada.
| | - Kang Shen
- Howard Hughes Medical Institute, Department of Biology, Stanford University, Stanford, CA 94305, USA.
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139
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Mosca TJ. On the Teneurin track: a new synaptic organization molecule emerges. Front Cell Neurosci 2015; 9:204. [PMID: 26074772 PMCID: PMC4444827 DOI: 10.3389/fncel.2015.00204] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 05/11/2015] [Indexed: 11/16/2022] Open
Abstract
To achieve proper synaptic development and function, coordinated signals must pass between the pre- and postsynaptic membranes. Such transsynaptic signals can be comprised of receptors and secreted ligands, membrane associated receptors, and also pairs of synaptic cell adhesion molecules. A critical open question bridging neuroscience, developmental biology, and cell biology involves identifying those signals and elucidating how they function. Recent work in Drosophila and vertebrate systems has implicated a family of proteins, the Teneurins, as a new transsynaptic signal in both the peripheral and central nervous systems. The Teneurins have established roles in neuronal wiring, but studies now show their involvement in regulating synaptic connections between neurons and bridging the synaptic membrane and the cytoskeleton. This review will examine the Teneurins as synaptic cell adhesion molecules, explore how they regulate synaptic organization, and consider how some consequences of human Teneurin mutations may have synaptopathic origins.
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Affiliation(s)
- Timothy J Mosca
- Department of Biology, Stanford University Stanford, CA, USA
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140
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Dabrowski A, Terauchi A, Strong C, Umemori H. Distinct sets of FGF receptors sculpt excitatory and inhibitory synaptogenesis. Development 2015; 142:1818-30. [PMID: 25926357 DOI: 10.1242/dev.115568] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2014] [Accepted: 03/25/2015] [Indexed: 12/13/2022]
Abstract
Neurons in the brain must establish a balanced network of excitatory and inhibitory synapses during development for the brain to function properly. An imbalance between these synapses underlies various neurological and psychiatric disorders. The formation of excitatory and inhibitory synapses requires precise molecular control. In the hippocampus, the structure crucial for learning and memory, fibroblast growth factor 22 (FGF22) and FGF7 specifically promote excitatory or inhibitory synapse formation, respectively. Knockout of either Fgf gene leads to excitatory-inhibitory imbalance in the mouse hippocampus and manifests in an altered susceptibility to epileptic seizures, underscoring the importance of FGF-dependent synapse formation. However, the receptors and signaling mechanisms by which FGF22 and FGF7 induce excitatory and inhibitory synapse differentiation are unknown. Here, we show that distinct sets of overlapping FGF receptors (FGFRs), FGFR2b and FGFR1b, mediate excitatory or inhibitory presynaptic differentiation in response to FGF22 and FGF7. Excitatory presynaptic differentiation is impaired in Fgfr2b and Fgfr1b mutant mice; however, inhibitory presynaptic defects are only found in Fgfr2b mutants. FGFR2b and FGFR1b are required for an excitatory presynaptic response to FGF22, whereas only FGFR2b is required for an inhibitory presynaptic response to FGF7. We further find that FGFRs are required in the presynaptic neuron to respond to FGF22, and that FRS2 and PI3K, but not PLCγ, mediate FGF22-dependent presynaptic differentiation. Our results reveal the specific receptors and signaling pathways that mediate FGF-dependent presynaptic differentiation, and thereby provide a mechanistic understanding of precise excitatory and inhibitory synapse formation in the mammalian brain.
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Affiliation(s)
- Ania Dabrowski
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA Medical Scientist Training Program, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA Neuroscience Graduate Program, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA Molecular & Behavioral Neuroscience Institute, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA
| | - Akiko Terauchi
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA Molecular & Behavioral Neuroscience Institute, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA
| | - Cameron Strong
- Molecular & Behavioral Neuroscience Institute, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA
| | - Hisashi Umemori
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA Medical Scientist Training Program, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA Neuroscience Graduate Program, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA Molecular & Behavioral Neuroscience Institute, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA
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141
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Fekete CD, Chiou TT, Miralles CP, Harris RS, Fiondella CG, Loturco JJ, De Blas AL. In vivo clonal overexpression of neuroligin 3 and neuroligin 2 in neurons of the rat cerebral cortex: Differential effects on GABAergic synapses and neuronal migration. J Comp Neurol 2015; 523:1359-78. [PMID: 25565602 DOI: 10.1002/cne.23740] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Revised: 01/02/2015] [Accepted: 01/02/2015] [Indexed: 01/08/2023]
Abstract
We studied the effect of clonal overexpression of neuroligin 3 (NL3) or neuroligin 2 (NL2) in the adult rat cerebral cortex following in utero electroporation (IUEP) at embryonic stage E14. Overexpression of NL3 leads to a large increase in vesicular gamma-aminobutyric acid (GABA) transporter (vGAT) and glutamic acid decarboxylase (GAD)65 in the GABAergic contacts that the overexpressing neurons receive. Overexpression of NL2 produced a similar effect but to a lesser extent. In contrast, overexpression of NL3 or NL2 after IUEP does not affect vesicular glutamate transporter 1 (vGlut1) in the glutamatergic contacts that the NL3 or NL2-overexpressing neurons receive. The NL3 or NL2-overexpressing neurons do not show increased innervation by parvalbumin-containing GABAergic terminals or increased parvalbumin in the same terminals that show increased vGAT. These results indicate that the observed increase in vGAT and GAD65 is not due to increased GABAergic innervation but to increased expression of vGAT and GAD65 in the GABAergic contacts that NL3 or NL2-overexpressing neurons receive. The majority of bright vGAT puncta contacting the NL3-overexpressing neurons have no gephyrin juxtaposed to them, indicating that many of these contacts are nonsynaptic. This contrasts with the majority of the NL2-overexpressing neurons, which show plenty of synaptic gephyrin clusters juxtaposed to vGAT. Besides having an effect on GABAergic contacts, overexpression of NL3 interferes with the neuronal radial migration, in the cerebral cortex, of the neurons overexpressing NL3.
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Affiliation(s)
- Christopher D Fekete
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut, 06269
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142
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Jacobi A, Loy K, Schmalz AM, Hellsten M, Umemori H, Kerschensteiner M, Bareyre FM. FGF22 signaling regulates synapse formation during post-injury remodeling of the spinal cord. EMBO J 2015; 34:1231-43. [PMID: 25766255 DOI: 10.15252/embj.201490578] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 02/16/2015] [Indexed: 12/24/2022] Open
Abstract
The remodeling of axonal circuits after injury requires the formation of new synaptic contacts to enable functional recovery. Which molecular signals initiate such axonal and synaptic reorganisation in the adult central nervous system is currently unknown. Here, we identify FGF22 as a key regulator of circuit remodeling in the injured spinal cord. We show that FGF22 is produced by spinal relay neurons, while its main receptors FGFR1 and FGFR2 are expressed by cortical projection neurons. FGF22 deficiency or the targeted deletion of FGFR1 and FGFR2 in the hindlimb motor cortex limits the formation of new synapses between corticospinal collaterals and relay neurons, delays their molecular maturation, and impedes functional recovery in a mouse model of spinal cord injury. These results establish FGF22 as a synaptogenic mediator in the adult nervous system and a crucial regulator of synapse formation and maturation during post-injury remodeling in the spinal cord.
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Affiliation(s)
- Anne Jacobi
- Institute of Clinical Neuroimmunology, Ludwig-Maximilians Universität München, Munich, Germany
| | - Kristina Loy
- Institute of Clinical Neuroimmunology, Ludwig-Maximilians Universität München, Munich, Germany
| | - Anja M Schmalz
- Institute of Clinical Neuroimmunology, Ludwig-Maximilians Universität München, Munich, Germany
| | - Mikael Hellsten
- Institute of Clinical Neuroimmunology, Ludwig-Maximilians Universität München, Munich, Germany
| | - Hisashi Umemori
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA Molecular & Behavioral Neuroscience Institute and Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Martin Kerschensteiner
- Institute of Clinical Neuroimmunology, Ludwig-Maximilians Universität München, Munich, Germany Munich Cluster of Systems Neurology (SyNergy), Munich, Germany
| | - Florence M Bareyre
- Institute of Clinical Neuroimmunology, Ludwig-Maximilians Universität München, Munich, Germany Munich Cluster of Systems Neurology (SyNergy), Munich, Germany
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143
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Abstract
Synaptic cell adhesion molecules are increasingly gaining attention for conferring specific properties to individual synapses. Netrin-G1 and netrin-G2 are trans-synaptic adhesion molecules that distribute on distinct axons, and their presence restricts the expression of their cognate receptors, NGL1 and NGL2, respectively, to specific subdendritic segments of target neurons. However, the neural circuits and functional roles of netrin-G isoform complexes remain unclear. Here, we use netrin-G-KO and NGL-KO mice to reveal that netrin-G1/NGL1 and netrin-G2/NGL2 interactions specify excitatory synapses in independent hippocampal pathways. In the hippocampal CA1 area, netrin-G1/NGL1 and netrin-G2/NGL2 were expressed in the temporoammonic and Schaffer collateral pathways, respectively. The lack of presynaptic netrin-Gs led to the dispersion of NGLs from postsynaptic membranes. In accord, netrin-G mutant synapses displayed opposing phenotypes in long-term and short-term plasticity through discrete biochemical pathways. The plasticity phenotypes in netrin-G-KOs were phenocopied in NGL-KOs, with a corresponding loss of netrin-Gs from presynaptic membranes. Our findings show that netrin-G/NGL interactions differentially control synaptic plasticity in distinct circuits via retrograde signaling mechanisms and explain how synaptic inputs are diversified to control neuronal activity.
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144
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Amyloid precursor protein dimerization and synaptogenic function depend on copper binding to the growth factor-like domain. J Neurosci 2014; 34:11159-72. [PMID: 25122912 DOI: 10.1523/jneurosci.0180-14.2014] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Accumulating evidence suggests that the copper-binding amyloid precursor protein (APP) has an essential synaptic function. APP synaptogenic function depends on trans-directed dimerization of the extracellular E1 domain encompassing a growth factor-like domain (GFLD) and a copper-binding domain (CuBD). Here we report the 1.75 Å crystal structure of the GFLD in complex with a copper ion bound with high affinity to an extended hairpin loop at the dimerization interface. In coimmunoprecipitation assays copper binding promotes APP interaction, whereas mutations in the copper-binding sites of either the GFLD or CuBD result in a drastic reduction in APP cis-orientated dimerization. We show that copper is essential and sufficient to induce trans-directed dimerization of purified APP. Furthermore, a mixed culture assay of primary neurons with HEK293 cells expressing different APP mutants revealed that APP potently promotes synaptogenesis depending on copper binding to the GFLD. Together, these findings demonstrate that copper binding to the GFLD of APP is required for APP cis-/trans-directed dimerization and APP synaptogenic function. Thus, neuronal activity or disease-associated changes in copper homeostasis likely go along with altered APP synaptic function.
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145
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Miller AC, Voelker LH, Shah AN, Moens CB. Neurobeachin is required postsynaptically for electrical and chemical synapse formation. Curr Biol 2014; 25:16-28. [PMID: 25484298 DOI: 10.1016/j.cub.2014.10.071] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Revised: 10/27/2014] [Accepted: 10/28/2014] [Indexed: 02/03/2023]
Abstract
BACKGROUND Neural networks and their function are defined by synapses, which are adhesions specialized for intercellular communication that can be either chemical or electrical. At chemical synapses, transmission between neurons is mediated by neurotransmitters, whereas at electrical synapses, direct ionic and metabolic coupling occur via gap junctions between neurons. The molecular pathways required for electrical synaptogenesis are not well understood, and whether they share mechanisms of formation with chemical synapses is not clear. RESULTS Here, using a forward genetic screen in zebrafish, we find that the autism-associated gene neurobeachin (nbea), which encodes a BEACH-domain-containing protein implicated in endomembrane trafficking, is required for both electrical and chemical synapse formation. Additionally, we find that nbea is dispensable for axonal formation and early dendritic outgrowth but is required to maintain dendritic complexity. These synaptic and morphological defects correlate with deficiencies in behavioral performance. Using chimeric animals in which individually identifiable neurons are either mutant or wild-type, we find that Nbea is necessary and sufficient autonomously in the postsynaptic neuron for both synapse formation and dendritic arborization. CONCLUSIONS Our data identify a surprising link between electrical and chemical synapse formation and show that Nbea acts as a critical regulator in the postsynaptic neuron for the coordination of dendritic morphology with synaptogenesis.
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Affiliation(s)
- Adam C Miller
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue N, Seattle, WA 98109, USA.
| | - Lisa H Voelker
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue N, Seattle, WA 98109, USA; Molecular and Cellular Biology, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA
| | - Arish N Shah
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue N, Seattle, WA 98109, USA
| | - Cecilia B Moens
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue N, Seattle, WA 98109, USA
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146
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Stahl R, Schilling S, Soba P, Rupp C, Hartmann T, Wagner K, Merdes G, Eggert S, Kins S. Shedding of APP limits its synaptogenic activity and cell adhesion properties. Front Cell Neurosci 2014; 8:410. [PMID: 25520622 PMCID: PMC4253958 DOI: 10.3389/fncel.2014.00410] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 11/11/2014] [Indexed: 01/05/2023] Open
Abstract
The amyloid precursor protein (APP) plays a central role in Alzheimer's disease (AD) and has essential synapse promoting functions. Synaptogenic activity as well as cell adhesion properties of APP presumably depend on trans-cellular dimerization via its extracellular domain. Since neuronal APP is extensively processed by secretases, it raises the question if APP shedding affects its cell adhesion and synaptogenic properties. We show that inhibition of APP shedding using cleavage deficient forms of APP or a dominant negative α-secretase strongly enhanced its cell adhesion and synaptogenic activity suggesting that synapse promoting function of APP is tightly regulated by α-secretase mediated processing, similar to other trans-cellular synaptic adhesion molecules.
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Affiliation(s)
- Ronny Stahl
- Center of Molecular Biology ZMBH, University of Heidelberg Heidelberg, Germany ; Department of Physiological Genomics, Institute of Physiology, Ludwig-Maximilians University Munich Munich, Germany
| | - Sandra Schilling
- Department of Human Biology and Human Genetics, Technical University of Kaiserslautern Kaiserslautern, Germany
| | - Peter Soba
- Center of Molecular Biology ZMBH, University of Heidelberg Heidelberg, Germany ; Center for Molecular Neurobiology (ZMNH), University of Hamburg Hamburg, Germany
| | - Carsten Rupp
- Department of Human Biology and Human Genetics, Technical University of Kaiserslautern Kaiserslautern, Germany
| | - Tobias Hartmann
- Deutsches Institut für DemenzPrävention, Experimental Neurology, Saarland University Homburg/Saar, Germany
| | - Katja Wagner
- Center of Molecular Biology ZMBH, University of Heidelberg Heidelberg, Germany ; Department of Human Biology and Human Genetics, Technical University of Kaiserslautern Kaiserslautern, Germany
| | - Gunter Merdes
- Center of Molecular Biology ZMBH, University of Heidelberg Heidelberg, Germany ; Department of Biosystems Science and Engineering, ETH Zürich Basel, Switzerland
| | - Simone Eggert
- Department of Human Biology and Human Genetics, Technical University of Kaiserslautern Kaiserslautern, Germany
| | - Stefan Kins
- Center of Molecular Biology ZMBH, University of Heidelberg Heidelberg, Germany ; Department of Human Biology and Human Genetics, Technical University of Kaiserslautern Kaiserslautern, Germany ; Deutsches Institut für DemenzPrävention, Experimental Neurology, Saarland University Homburg/Saar, Germany
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147
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Terauchi A, Timmons KM, Kikuma K, Pechmann Y, Kneussel M, Umemori H. Selective synaptic targeting of the excitatory and inhibitory presynaptic organizers FGF22 and FGF7. J Cell Sci 2014; 128:281-92. [PMID: 25431136 DOI: 10.1242/jcs.158337] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Specific formation of excitatory and inhibitory synapses is crucial for proper functioning of the brain. Fibroblast growth factor 22 (FGF22) and FGF7 are postsynaptic-cell-derived presynaptic organizers necessary for excitatory and inhibitory presynaptic differentiation, respectively, in the hippocampus. For the establishment of specific synaptic networks, these FGFs must localize to appropriate synaptic locations - FGF22 to excitatory and FGF7 to inhibitory postsynaptic sites. Here, we show that distinct motor and adaptor proteins contribute to intracellular microtubule transport of FGF22 and FGF7. Excitatory synaptic targeting of FGF22 requires the motor proteins KIF3A and KIF17 and the adaptor protein SAP102 (also known as DLG3). By contrast, inhibitory synaptic targeting of FGF7 requires the motor KIF5 and the adaptor gephyrin. Time-lapse imaging shows that FGF22 moves with SAP102, whereas FGF7 moves with gephyrin. These results reveal the basis of selective targeting of the excitatory and inhibitory presynaptic organizers that supports their different synaptogenic functions. Finally, we found that knockdown of SAP102 or PSD95 (also known as DLG4), which impairs the differentiation of excitatory synapses, alters FGF7 localization, suggesting that signals from excitatory synapses might regulate inhibitory synapse formation by controlling the distribution of the inhibitory presynaptic organizer.
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Affiliation(s)
- Akiko Terauchi
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA Molecular & Behavioral Neuroscience Institute, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA
| | - Kendall M Timmons
- Molecular & Behavioral Neuroscience Institute, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA
| | - Koto Kikuma
- Molecular & Behavioral Neuroscience Institute, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA
| | - Yvonne Pechmann
- Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Falkenried 94, D-20251 Hamburg, Germany
| | - Matthias Kneussel
- Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Falkenried 94, D-20251 Hamburg, Germany
| | - Hisashi Umemori
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA Molecular & Behavioral Neuroscience Institute, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA
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148
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Brown LE, Fuchs C, Nicholson MW, Stephenson FA, Thomson AM, Jovanovic JN. Inhibitory synapse formation in a co-culture model incorporating GABAergic medium spiny neurons and HEK293 cells stably expressing GABAA receptors. J Vis Exp 2014:e52115. [PMID: 25489750 PMCID: PMC4354098 DOI: 10.3791/52115] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Inhibitory neurons act in the central nervous system to regulate the dynamics and spatio-temporal co-ordination of neuronal networks. GABA (γ-aminobutyric acid) is the predominant inhibitory neurotransmitter in the brain. It is released from the presynaptic terminals of inhibitory neurons within highly specialized intercellular junctions known as synapses, where it binds to GABAA receptors (GABAARs) present at the plasma membrane of the synapse-receiving, postsynaptic neurons. Activation of these GABA-gated ion channels leads to influx of chloride resulting in postsynaptic potential changes that decrease the probability that these neurons will generate action potentials. During development, diverse types of inhibitory neurons with distinct morphological, electrophysiological and neurochemical characteristics have the ability to recognize their target neurons and form synapses which incorporate specific GABAARs subtypes. This principle of selective innervation of neuronal targets raises the question as to how the appropriate synaptic partners identify each other. To elucidate the underlying molecular mechanisms, a novel in vitro co-culture model system was established, in which medium spiny GABAergic neurons, a highly homogenous population of neurons isolated from the embryonic striatum, were cultured with stably transfected HEK293 cell lines that express different GABAAR subtypes. Synapses form rapidly, efficiently and selectively in this system, and are easily accessible for quantification. Our results indicate that various GABAAR subtypes differ in their ability to promote synapse formation, suggesting that this reduced in vitro model system can be used to reproduce, at least in part, the in vivo conditions required for the recognition of the appropriate synaptic partners and formation of specific synapses. Here the protocols for culturing the medium spiny neurons and generating HEK293 cells lines expressing GABAARs are first described, followed by detailed instructions on how to combine these two cell types in co-culture and analyze the formation of synaptic contacts.
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Affiliation(s)
| | - Celine Fuchs
- UCL School of Pharmacy, University College London
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149
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Dlg5 regulates dendritic spine formation and synaptogenesis by controlling subcellular N-cadherin localization. J Neurosci 2014; 34:12745-61. [PMID: 25232112 DOI: 10.1523/jneurosci.1280-14.2014] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Most excitatory synapses in the mammalian brain are formed on dendritic spines, and spine density has a profound impact on synaptic transmission, integration, and plasticity. Membrane-associated guanylate kinase (MAGUK) proteins are intracellular scaffolding proteins with well established roles in synapse function. However, whether MAGUK proteins are required for the formation of dendritic spines in vivo is unclear. We isolated a novel disc large-5 (Dlg5) allele in mice, Dlg5(LP), which harbors a missense mutation in the DLG5 SH3 domain, greatly attenuating its ability to interact with the DLG5 GUK domain. We show here that DLG5 is a MAGUK protein that regulates spine formation, synaptogenesis, and synaptic transmission in cortical neurons. DLG5 regulates synaptogenesis by enhancing the cell surface localization of N-cadherin, revealing a key molecular mechanism for regulating the subcellular localization of this cell adhesion molecule during synaptogenesis.
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150
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Coles CH, Mitakidis N, Zhang P, Elegheert J, Lu W, Stoker AW, Nakagawa T, Craig AM, Jones EY, Aricescu AR. Structural basis for extracellular cis and trans RPTPσ signal competition in synaptogenesis. Nat Commun 2014; 5:5209. [PMID: 25385546 PMCID: PMC4239663 DOI: 10.1038/ncomms6209] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 09/09/2014] [Indexed: 01/26/2023] Open
Abstract
Receptor protein tyrosine phosphatase sigma (RPTPσ) regulates neuronal extension and acts as a presynaptic nexus for multiple protein and proteoglycan interactions during synaptogenesis. Unknown mechanisms govern the shift in RPTPσ function, from outgrowth promotion to synaptic organization. Here, we report crystallographic, electron microscopic and small-angle X-ray scattering analyses, which reveal sufficient inter-domain flexibility in the RPTPσ extracellular region for interaction with both cis (same cell) and trans (opposite cell) ligands. Crystal structures of RPTPσ bound to its postsynaptic ligand TrkC detail an interaction surface partially overlapping the glycosaminoglycan-binding site. Accordingly, heparan sulphate and heparin oligomers compete with TrkC for RPTPσ binding in vitro and disrupt TrkC-dependent synaptic differentiation in neuronal co-culture assays. We propose that transient RPTPσ ectodomain emergence from the presynaptic proteoglycan layer allows capture by TrkC to form a trans-synaptic complex, the consequent reduction in RPTPσ flexibility potentiating interactions with additional ligands to orchestrate excitatory synapse formation.
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Affiliation(s)
- Charlotte H. Coles
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - Nikolaos Mitakidis
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - Peng Zhang
- Brain Research Centre and Department of Psychiatry, University of British Columbia, Vancouver, British Columbia, Canada V6T 2B5
| | - Jonathan Elegheert
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - Weixian Lu
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - Andrew W. Stoker
- Cancer Section, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK
| | - Terunaga Nakagawa
- Department of Molecular Physiology and Biophysics, Vanderbilt University, School of Medicine, 702 Light Hall (0615), Nashville, Tennessee 37232-0615, USA
| | - Ann Marie Craig
- Brain Research Centre and Department of Psychiatry, University of British Columbia, Vancouver, British Columbia, Canada V6T 2B5
| | - E. Yvonne Jones
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - A. Radu Aricescu
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
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