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Nawrocka WI, Cheng S, Hao B, Rosen MC, Cortés E, Baltrusaitis EE, Aziz Z, Kovács IA, Özkan E. Nematode Extracellular Protein Interactome Expands Connections between Signaling Pathways. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.08.602367. [PMID: 39026773 PMCID: PMC11257444 DOI: 10.1101/2024.07.08.602367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/20/2024]
Abstract
Multicellularity was accompanied by the emergence of new classes of cell surface and secreted proteins. The nematode C. elegans is a favorable model to study cell surface interactomes, given its well-defined and stereotyped cell types and intercellular contacts. Here we report our C. elegans extracellular interactome dataset, the largest yet for an invertebrate. Most of these interactions were unknown, despite recent datasets for flies and humans, as our collection contains a larger selection of protein families. We uncover new interactions for all four major axon guidance pathways, including ectodomain interactions between three of the pathways. We demonstrate that a protein family known to maintain axon locations are secreted receptors for insulins. We reveal novel interactions of cystine-knot proteins with putative signaling receptors, which may extend the study of neurotrophins and growth-factor-mediated functions to nematodes. Finally, our dataset provides insights into human disease mechanisms and how extracellular interactions may help establish connectomes.
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Affiliation(s)
- Wioletta I. Nawrocka
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
- Institute for Neuroscience, The University of Chicago, Chicago, IL 60637, USA
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA
| | - Shouqiang Cheng
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
- Institute for Neuroscience, The University of Chicago, Chicago, IL 60637, USA
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA
| | - Bingjie Hao
- Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA
| | - Matthew C. Rosen
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
- Institute for Neuroscience, The University of Chicago, Chicago, IL 60637, USA
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA
| | - Elena Cortés
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
- Institute for Neuroscience, The University of Chicago, Chicago, IL 60637, USA
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA
| | - Elana E. Baltrusaitis
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
- Institute for Neuroscience, The University of Chicago, Chicago, IL 60637, USA
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA
| | - Zainab Aziz
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
- Institute for Neuroscience, The University of Chicago, Chicago, IL 60637, USA
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA
| | - István A. Kovács
- Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA
- Northwestern Institute on Complex Systems, Northwestern University, Evanston, IL 60208, USA
- Department of Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, IL 60208, USA
| | - Engin Özkan
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
- Institute for Neuroscience, The University of Chicago, Chicago, IL 60637, USA
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA
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Crowl S, Coleman MB, Chaphiv A, Naegle KM. A systematic analysis of the effects of splicing on the diversity of post-translational modifications in protein isoforms. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.10.575062. [PMID: 38260432 PMCID: PMC10802621 DOI: 10.1101/2024.01.10.575062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Post-translational modifications (PTMs) and splicing are known to be important regulatory processes for controlling protein function and activity. However, there have been limitations in analyzing the interplay of alternative splicing and PTMs, which stems from the deep differences in genomic and proteomic databases. In this work, we bridged the protein- and genome-centric world views to map PTMs to genomic locations for subsequent projection of PTMs onto alternative isoforms. We then performed a systematic analysis of the diversification of PTMs by alternative splicing, including exploration of the modification-specific rates of inclusion across isoforms and how often the regulatory sequences directly flanking a PTM are impacted by splicing, which might indicate altered regulatory or binding interactions in the alternatively spliced isoform. We found that 6-51% of PTMs are excluded from at least one isoform, depending on the modification type. Further, approximately 2% of prospective PTM sites exhibited altered regulatory sequences surrounding the modification site, suggesting that regulatory or binding interactions might be diversified in these proteoforms. Lastly, we applied this PTM-to-isoform mapping approach to explore the impacts of disease-related splicing in prostate cancer, identifying possible new hypotheses explaining the variable consequences of ESRP1 expression in different cancers. As a part of this work, we have provided an easily implementable tool for annotating splice events identified from RNA-sequencing with PTMs and their functional consequences, called PTM-POSE.
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Altas B, Tuffy LP, Patrizi A, Dimova K, Soykan T, Brandenburg C, Romanowski AJ, Whitten JR, Robertson CD, Khim SN, Crutcher GW, Ambrozkiewicz MC, Yagensky O, Krueger-Burg D, Hammer M, Hsiao HH, Laskowski PR, Dyck L, Puche AC, Sassoè-Pognetto M, Chua JJE, Urlaub H, Jahn O, Brose N, Poulopoulos A. Region-Specific Phosphorylation Determines Neuroligin-3 Localization to Excitatory Versus Inhibitory Synapses. Biol Psychiatry 2023:S0006-3223(23)01799-7. [PMID: 38154503 PMCID: PMC11209832 DOI: 10.1016/j.biopsych.2023.12.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 12/19/2023] [Accepted: 12/19/2023] [Indexed: 12/30/2023]
Abstract
BACKGROUND Neuroligin-3 is a postsynaptic adhesion molecule involved in synapse development and function. It is implicated in rare, monogenic forms of autism, and its shedding is critical to the tumor microenvironment of gliomas. While other members of the neuroligin family exhibit synapse-type specificity in localization and function through distinct interactions with postsynaptic scaffold proteins, the specificity of neuroligin-3 synaptic localization remains largely unknown. METHODS We investigated the synaptic localization of neuroligin-3 across regions in mouse and human brain samples after validating antibody specificity in knockout animals. We raised a phospho-specific neuroligin antibody and used phosphoproteomics, cell-based assays, and in utero CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/Cas9) knockout and gene replacement to identify mechanisms that regulate neuroligin-3 localization to distinct synapse types. RESULTS Neuroligin-3 exhibits region-dependent synapse specificity, largely localizing to excitatory synapses in cortical regions and inhibitory synapses in subcortical regions of the brain in both mice and humans. We identified specific phosphorylation of cortical neuroligin-3 at a key binding site for recruitment to inhibitory synapses, while subcortical neuroligin-3 remained unphosphorylated. In vitro, phosphomimetic mutation of that site disrupted neuroligin-3 association with the inhibitory postsynaptic scaffolding protein gephyrin. In vivo, phosphomimetic mutants of neuroligin-3 localized to excitatory postsynapses, while phospho-null mutants localized to inhibitory postsynapses. CONCLUSIONS These data reveal an unexpected region-specific pattern of neuroligin-3 synapse specificity, as well as a phosphorylation-dependent mechanism that regulates its recruitment to either excitatory or inhibitory synapses. These findings add to our understanding of how neuroligin-3 is involved in conditions that may affect the balance of excitation and inhibition.
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Affiliation(s)
- Bekir Altas
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Liam P Tuffy
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Annarita Patrizi
- Department of Neuroscience Rita Levi Montalcini, University of Turin, Turin, Italy
| | - Kalina Dimova
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany; Neuroproteomics Group, Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Tolga Soykan
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Cheryl Brandenburg
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Andrea J Romanowski
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Julia R Whitten
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Colin D Robertson
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Saovleak N Khim
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Garrett W Crutcher
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Mateusz C Ambrozkiewicz
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Oleksandr Yagensky
- Research Group Protein Trafficking in Synaptic Development and Function, Laboratory of Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Dilja Krueger-Burg
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Matthieu Hammer
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - He-Hsuan Hsiao
- Bioanalytical Mass Spectrometry, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Pawel R Laskowski
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Lydia Dyck
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Adam C Puche
- Department of Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland
| | | | - John J E Chua
- Research Group Protein Trafficking in Synaptic Development and Function, Laboratory of Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Henning Urlaub
- Bioanalytical Mass Spectrometry, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany; Bioanalytics Group, Institute of Clinical Chemistry, University Medical Center Göttingen, Göttingen, Germany
| | - Olaf Jahn
- Neuroproteomics Group, Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany; Translational Neuroproteomics Group, Department of Psychiatry and Psychotherapy, University Medical Center Göttingen, Göttingen, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Alexandros Poulopoulos
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, Maryland; Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany.
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Benner O, Cast TP, Minamide LS, Lenninger Z, Bamburg JR, Chanda S. Multiple N-linked glycosylation sites critically modulate the synaptic abundance of neuroligin isoforms. J Biol Chem 2023; 299:105361. [PMID: 37865312 PMCID: PMC10679506 DOI: 10.1016/j.jbc.2023.105361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Revised: 10/05/2023] [Accepted: 10/11/2023] [Indexed: 10/23/2023] Open
Abstract
In recent years, elegant glycomic and glycoproteomic approaches have revealed an intricate glycosylation profile of mammalian brain with enormous spatial and temporal diversities. Nevertheless, at a cellular level, it is unclear how these post-translational modifications affect various proteins to influence crucial neuronal properties. Here, we have investigated the impact of N-linked glycosylation on neuroligins (NLGNs), a class of cell-adhesion molecules that play instructive roles in synapse organization. We found that endogenous NLGN proteins are differentially glycosylated across several regions of murine brain in a sex-independent but isoform-dependent manner. In both rodent primary neurons derived from brain sections and human neurons differentiated from stem cells, all NLGN variants were highly enriched with multiple N-glycan subtypes, which cumulatively ensured their efficient trafficking to the cell surface. Removal of these N-glycosylation residues only had a moderate effect on NLGNs' stability or expression levels but particularly enhanced their retention at the endoplasmic reticulum. As a result, the glycosylation-deficient NLGNs exhibited considerable impairments in their dendritic distribution and postsynaptic accumulation, which in turn, virtually eliminated their ability to recruit presynaptic terminals and significantly reduced NLGN overexpression-induced assemblies of both glutamatergic and GABAergic synapse structures. Therefore, our results highlight an essential mechanistic contribution of N-linked glycosylations in facilitating the appropriate secretory transport of a major synaptic cell-adhesion molecule and promoting its cellular function in neurons.
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Affiliation(s)
- Orion Benner
- Biochemistry & Molecular Biology, Colorado State University, Fort Collins, USA
| | - Thomas P Cast
- Biochemistry & Molecular Biology, Colorado State University, Fort Collins, USA
| | - Laurie S Minamide
- Biochemistry & Molecular Biology, Colorado State University, Fort Collins, USA
| | - Zephyr Lenninger
- Molecular, Cellular & Integrated Neurosciences, Colorado State University, Fort Collins, Colorado, USA
| | - James R Bamburg
- Biochemistry & Molecular Biology, Colorado State University, Fort Collins, USA; Molecular, Cellular & Integrated Neurosciences, Colorado State University, Fort Collins, Colorado, USA; Cell & Molecular Biology, Colorado State University, Fort Collins, Colorado, USA
| | - Soham Chanda
- Biochemistry & Molecular Biology, Colorado State University, Fort Collins, USA; Molecular, Cellular & Integrated Neurosciences, Colorado State University, Fort Collins, Colorado, USA; Cell & Molecular Biology, Colorado State University, Fort Collins, Colorado, USA.
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Lagardère M, Drouet A, Sainlos M, Thoumine O. High-Resolution Fluorescence Imaging Combined With Computer Simulations to Quantitate Surface Dynamics and Nanoscale Organization of Neuroligin-1 at Synapses. Front Synaptic Neurosci 2022; 14:835427. [PMID: 35546899 PMCID: PMC9083120 DOI: 10.3389/fnsyn.2022.835427] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Accepted: 03/09/2022] [Indexed: 11/13/2022] Open
Abstract
Neuroligins (NLGNs) form a family of cell adhesion molecules implicated in synapse development, but the mechanisms that retain these proteins at synapses are still incompletely understood. Recent studies indicate that surface-associated NLGN1 is diffusionally trapped at synapses, where it interacts with quasi-static scaffolding elements of the post-synaptic density. Whereas single molecule tracking reveals rapid diffusion and transient immobilization of NLGN1 at synapses within seconds, fluorescence recovery after photobleaching experiments indicate instead a long-term turnover of NLGN1 at synapse, in the hour time range. To gain insight into the mechanisms supporting NLGN1 anchorage at post-synapses and try to reconcile those experimental paradigms, we quantitatively analyzed here live-cell and super-resolution imaging experiments performed on NLGN1 using a newly released simulator of membrane protein dynamics for fluorescence microscopy, FluoSim. Based on a small set of parameters including diffusion coefficients, binding constants, and photophysical rates, the framework describes fairly well the dynamic behavior of extra-synaptic and synaptic NLGN1 over both short and long time ranges, and provides an estimate of NLGN1 copy numbers in post-synaptic densities at steady-state (around 50 dimers). One striking result is that the residence time of NLGN1 at synapses is much longer than what can be expected from extracellular interactions with pre-synaptic neurexins only, suggesting that NLGN1 is stabilized at synapses through multivalent interactions with intracellular post-synaptic scaffolding proteins.
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Postsynaptic autism spectrum disorder genes and synaptic dysfunction. Neurobiol Dis 2021; 162:105564. [PMID: 34838666 DOI: 10.1016/j.nbd.2021.105564] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Revised: 11/17/2021] [Accepted: 11/23/2021] [Indexed: 12/20/2022] Open
Abstract
This review provides an overview of the synaptic dysfunction of neuronal circuits and the ensuing behavioral alterations caused by mutations in autism spectrum disorder (ASD)-linked genes directly or indirectly affecting the postsynaptic neuronal compartment. There are plenty of ASD risk genes, that may be broadly grouped into those involved in gene expression regulation (epigenetic regulation and transcription) and genes regulating synaptic activity (neural communication and neurotransmission). Notably, the effects mediated by ASD-associated genes can vary extensively depending on the developmental time and/or subcellular site of expression. Therefore, in order to gain a better understanding of the mechanisms of disruptions in postsynaptic function, an effort to better model ASD in experimental animals is required to improve standardization and increase reproducibility within and among studies. Such an effort holds promise to provide deeper insight into the development of these disorders and to improve the translational value of preclinical studies.
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Glycoconjugate journal special issue on: the glycobiology of Parkinson's disease. Glycoconj J 2021; 39:55-74. [PMID: 34757539 DOI: 10.1007/s10719-021-10024-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2021] [Revised: 09/14/2021] [Accepted: 09/24/2021] [Indexed: 10/19/2022]
Abstract
Parkinson's disease (PD) is a neurodegenerative disorder that affects over 10 million aging people worldwide. This condition is characterized by the degeneration of dopaminergic neurons in the pars compacta region of the substantia nigra (SNpc) and by aggregation of proteins, commonly α-synuclein (SNCA). The formation of Lewy bodies that encapsulate aggregated proteins in lipid vesicles is a hallmark of PD. Glycosylation of proteins and neuroinflammation are involved in the pathogenesis. SNCA has many posttranslational modifications and interacts with components of membranes that affect aggregation. The large membrane lipid dolichol accumulates in the brain upon age and has a significant effect on membrane structure. The replacement of dopamine and dopaminergic neurons are at the forefront of therapeutic development. This review examines the role of membrane lipids, glycolipids, glycoproteins and dopamine in the aggregation of SNCA and development of PD. We discuss the SNCA-dopamine-neuromelanin-dolichol axis and the role of membranes in neuronal stem cells that could be a regenerative therapy for PD patients.
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Abstract
Herein, I intend to capture highlights shared with my academic and research colleagues over the 60 years I devoted initially to my graduate and postdoctoral training and then to academic endeavors starting as an assistant professor in a new medical school at the University of California, San Diego (UCSD). During this period, the Department of Pharmacology emerged from a division within the Department of Medicine to become the first basic science department, solely within the School of Medicine at UCSD in 1979. As part of the school's plans to reorganize and to retain me at UCSD, I was appointed as founding chair. Some years later in 2002, faculty, led largely within the Department of Pharmacology and by practicing pharmacists within UCSD Healthcare, started the independent Skaggs School of Pharmacy and Pharmaceutical Sciences with a doctor of pharmacy (PharmD) program, where I served as the founding dean. My career pathway, from working at my family-owned pharmacy to chairing a department in a school of medicine and then becoming the dean of a school of pharmacy at a research-intensive, student-centered institution, involved some risky decisions. But the academic, curricular, and accreditation challenges posed were met by a cadre of creative faculty colleagues. I offer my experiences to individuals confronted with a multiplicity of real or imagined opportunities in academic health sciences, the related pharmaceutical industry, and government oversight agencies.
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Affiliation(s)
- Palmer Taylor
- Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, and School of Medicine, University of California, San Diego, La Jolla, California 92093, USA
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An Autism-Associated Mutation Impairs Neuroligin-4 Glycosylation and Enhances Excitatory Synaptic Transmission in Human Neurons. J Neurosci 2020; 41:392-407. [PMID: 33268543 DOI: 10.1523/jneurosci.0404-20.2020] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Revised: 11/18/2020] [Accepted: 11/20/2020] [Indexed: 02/06/2023] Open
Abstract
Neuroligins (NLGNs) are a class of postsynaptic cell adhesion molecules that interact with presynaptic neurexins (NRXNs) and regulate synapse function. NLGN4 is a member of the NLGN family and consists of a unique amino acid sequence in humans that is not evolutionarily well conserved in rodents. The human-specific NLGN4 gene has been reported to be mutated in many patients with autism and other neurodevelopmental disorders. However, it remained unclear how these mutations might alter the molecular properties of NLGN4 and affect synaptic transmission in human neurons. Here, we describe a severely autistic male patient carrying a single amino acid substitution (R101Q) in the NLGN4 gene. When expressed in HEK293 cells, the R101Q mutation in NLGN4 did not affect its binding affinity for NRXNs or its capacity to form homodimers. This mutation, however, impaired the maturation of NLGN4 protein by inhibiting N-linked glycosylation at an adjacent residue (N102), which is conserved in all NLGNs. As a result, the R101Q substitution significantly decreased the surface trafficking of NLGN4 and increased its retention in the endoplasmic reticulum and Golgi apparatus. In human neurons derived from male stem cell lines, the R101Q mutation also similarly reduced the synaptic localization of NLGN4, resulting in a loss-of-function phenotype. This mutation-induced trafficking defect substantially diminished the ability of NLGN4 to form excitatory synapses and modulate their functional properties. Viewed together, our findings suggest that the R101Q mutation is pathogenic for NLGN4 and can lead to synaptic dysfunction in autism.
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FluoSim: simulator of single molecule dynamics for fluorescence live-cell and super-resolution imaging of membrane proteins. Sci Rep 2020; 10:19954. [PMID: 33203884 PMCID: PMC7672080 DOI: 10.1038/s41598-020-75814-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Accepted: 09/28/2020] [Indexed: 12/14/2022] Open
Abstract
Fluorescence live-cell and super-resolution microscopy methods have considerably advanced our understanding of the dynamics and mesoscale organization of macro-molecular complexes that drive cellular functions. However, different imaging techniques can provide quite disparate information about protein motion and organization, owing to their respective experimental ranges and limitations. To address these issues, we present here a robust computer program, called FluoSim, which is an interactive simulator of membrane protein dynamics for live-cell imaging methods including SPT, FRAP, PAF, and FCS, and super-resolution imaging techniques such as PALM, dSTORM, and uPAINT. FluoSim integrates diffusion coefficients, binding rates, and fluorophore photo-physics to calculate in real time the localization and intensity of thousands of independent molecules in 2D cellular geometries, providing simulated data directly comparable to actual experiments. FluoSim was thoroughly validated against experimental data obtained on the canonical neurexin-neuroligin adhesion complex at cell-cell contacts. This unified software allows one to model and predict membrane protein dynamics and localization at the ensemble and single molecule level, so as to reconcile imaging paradigms and quantitatively characterize protein behavior in complex cellular environments.
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Comoletti D, Trobiani L, Chatonnet A, Bourne Y, Marchot P. Comparative mapping of selected structural determinants on the extracellular domains of cholinesterase-like cell-adhesion molecules. Neuropharmacology 2020; 184:108381. [PMID: 33166544 DOI: 10.1016/j.neuropharm.2020.108381] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 09/10/2020] [Accepted: 10/29/2020] [Indexed: 11/18/2022]
Abstract
Cell adhesion generally involves formation of homophilic or heterophilic protein complexes between two cells to form transcellular junctions. Neural cell-adhesion members of the α/β-hydrolase fold superfamily of proteins use their extracellular or soluble cholinesterase-like domain to bind cognate partners across cell membranes, as illustrated by the neuroligins. These cell-adhesion molecules currently comprise the synaptic organizers neuroligins found in all animal phyla, along with three proteins found only in invertebrates: the guidance molecule neurotactin, the glia-specific gliotactin, and the basement membrane protein glutactin. Although these proteins share a cholinesterase-like fold, they lack one or more residues composing the catalytic triad responsible for the enzymatic activity of the cholinesterases. Conversely, they are found in various subcellular localisations and display specific disulfide bonding and N-glycosylation patterns, along with individual surface determinants possibly associated with recognition and binding of protein partners. Formation of non-covalent dimers typical of the cholinesterases is documented for mammalian neuroligins, yet whether invertebrate neuroligins and their neurotactin, gliotactin and glutactin relatives also form dimers in physiological conditions is unknown. Here we provide a brief overview of the localization, function, evolution, and conserved versus individual structural determinants of these cholinesterase-like cell-adhesion proteins. This article is part of the special issue entitled 'Acetylcholinesterase Inhibitors: From Bench to Bedside to Battlefield'.
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Affiliation(s)
- Davide Comoletti
- School of Biological Sciences, Victoria University of Wellington, Wellington, 6012, New Zealand; Child Health Institute of New Jersey, New Brunswick, NJ 08901, USA; Department of Neuroscience and Cell Biology Robert Wood Johnson Medical School, Rutgers University, New Brunswick, NJ 08901, USA.
| | - Laura Trobiani
- School of Biological Sciences, Victoria University of Wellington, Wellington, 6012, New Zealand
| | - Arnaud Chatonnet
- Lab 'Dynamique Musculaire et Métabolisme', Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (INRAE) / Université Montpellier, Montpellier, France
| | - Yves Bourne
- Lab 'Architecture et Fonction des Macromolécules Biologiques (AFMB)', Centre National de la Recherche Scientifique (CNRS)/Aix-Marseille Univ, Faculté des Sciences - Campus Luminy, Marseille, France
| | - Pascale Marchot
- Lab 'Architecture et Fonction des Macromolécules Biologiques (AFMB)', Centre National de la Recherche Scientifique (CNRS)/Aix-Marseille Univ, Faculté des Sciences - Campus Luminy, Marseille, France.
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Trobiani L, Meringolo M, Diamanti T, Bourne Y, Marchot P, Martella G, Dini L, Pisani A, De Jaco A, Bonsi P. The neuroligins and the synaptic pathway in Autism Spectrum Disorder. Neurosci Biobehav Rev 2020; 119:37-51. [PMID: 32991906 DOI: 10.1016/j.neubiorev.2020.09.017] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 09/11/2020] [Accepted: 09/19/2020] [Indexed: 12/13/2022]
Abstract
The genetics underlying autism spectrum disorder (ASD) is complex and heterogeneous, and de novo variants are found in genes converging in functional biological processes. Neuronal communication, including trans-synaptic signaling involving two families of cell-adhesion proteins, the presynaptic neurexins and the postsynaptic neuroligins, is one of the most recurrently affected pathways in ASD. Given the role of these proteins in determining synaptic function, abnormal synaptic plasticity and failure to establish proper synaptic contacts might represent mechanisms underlying risk of ASD. More than 30 mutations have been found in the neuroligin genes. Most of the resulting residue substitutions map in the extracellular, cholinesterase-like domain of the protein, and impair protein folding and trafficking. Conversely, the stalk and intracellular domains are less affected. Accordingly, several genetic animal models of ASD have been generated, showing behavioral and synaptic alterations. The aim of this review is to discuss the current knowledge on ASD-linked mutations in the neuroligin proteins and their effect on synaptic function, in various brain areas and circuits.
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Affiliation(s)
- Laura Trobiani
- Dept. Biology and Biotechnology, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy
| | - Maria Meringolo
- Lab. Neurophysiology and Plasticity, IRCCS Fondazione Santa Lucia, Via del Fosso di Fiorano 64, 00143 Rome, Italy; Dept. Systems Medicine, University Tor Vergata, Via Montpellier 1, 00133 Rome, Italy
| | - Tamara Diamanti
- Dept. Biology and Biotechnology, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy
| | - Yves Bourne
- Lab. "Architecture et Fonction des Macromolécules Biologiques", CNRS/Aix Marseille Univ, Faculté des Sciences - Campus Luminy, 163 Avenue de Luminy, 13288 Marseille cedex 09, France
| | - Pascale Marchot
- Lab. "Architecture et Fonction des Macromolécules Biologiques", CNRS/Aix Marseille Univ, Faculté des Sciences - Campus Luminy, 163 Avenue de Luminy, 13288 Marseille cedex 09, France
| | - Giuseppina Martella
- Lab. Neurophysiology and Plasticity, IRCCS Fondazione Santa Lucia, Via del Fosso di Fiorano 64, 00143 Rome, Italy; Dept. Systems Medicine, University Tor Vergata, Via Montpellier 1, 00133 Rome, Italy
| | - Luciana Dini
- Dept. Biology and Biotechnology, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy
| | - Antonio Pisani
- Lab. Neurophysiology and Plasticity, IRCCS Fondazione Santa Lucia, Via del Fosso di Fiorano 64, 00143 Rome, Italy; Dept. Systems Medicine, University Tor Vergata, Via Montpellier 1, 00133 Rome, Italy
| | - Antonella De Jaco
- Dept. Biology and Biotechnology, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy.
| | - Paola Bonsi
- Lab. Neurophysiology and Plasticity, IRCCS Fondazione Santa Lucia, Via del Fosso di Fiorano 64, 00143 Rome, Italy.
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13
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Golub M, Hussein R, Ibrahim M, Hecht M, Wieland DCF, Martel A, Machado B, Zouni A, Pieper J. Solution Structure of the Detergent-Photosystem II Core Complex Investigated by Small-Angle Scattering Techniques. J Phys Chem B 2020; 124:8583-8592. [PMID: 32816484 DOI: 10.1021/acs.jpcb.0c07169] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Albeit achieving the X-ray diffraction structure of dimeric photosystem II core complexes (dPSIIcc) at the atomic resolution, the nature of the detergent belt surrounding dPSIIcc remains ambiguous. Therefore, the solution structure of the whole detergent-protein complex of dPSIIcc of Thermosynechococcus elongatus (T. elongatus) solubilized in n-dodecyl-ß-d-maltoside (ßDM) was investigated by a combination of small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) with contrast variation. First, the structure of dPSIIcc was studied separately in SANS experiments using a contrast of 5% D2O. Guinier analysis reveals that the dPSIIcc solution is virtually free of aggregation in the studied concentration range of 2-10 mg/mL dPSIIcc, and characterized by a radius of gyration of 62 Å. A structure reconstitution shows that dPSIIcc in buffer solution widely retains the crystal structure reported by X-ray free electron laser studies at room temperature with a slight expansion of the entire protein. Additional SANS experiments on dPSIIcc samples in a buffer solution containing 75% D2O provide information about the size and shape of the whole detergent-dPSIIcc. The maximum position of P(r) function increases to 68 Å, i.e., it is about 6 Å larger than that of dPSIIcc only, thus indicating the presence of an additional structure. Thus, it can be concluded that dPSIIcc is surrounded by a monomolecular belt of detergent molecules under appropriate solubilization conditions. The homogeneity of the ßDM-dPSIIcc solutions was also verified using dynamic light scattering. Complementary SAXS experiments indicate the presence of unbound detergent micelles by a separate peak consistent with a spherical shape possessing a radius of about 40 Å. The latter structure also contributes to the SANS data but rather broadens the SANS curve artificially. Without the simultaneous inspection of SANS and SAXS data, this effect may lead to an apparent underestimation of the size of the PS II-detergent complex. The formation of larger unbound detergent aggregates in solution prior to crystallization may have a significant effect on the crystal formation or quality of the ßDM-dPSIIcc.
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Affiliation(s)
- Maksym Golub
- Institute of Physics, University of Tartu, Wilhelm Ostwald str. 1, 50411 Tartu, Estonia
| | - Rana Hussein
- Humboldt Universität zu Berlin, Philipp Str. 13, 10115 Berlin, Germany
| | - Mohamed Ibrahim
- Humboldt Universität zu Berlin, Philipp Str. 13, 10115 Berlin, Germany
| | - Max Hecht
- Institute of Physics, University of Tartu, Wilhelm Ostwald str. 1, 50411 Tartu, Estonia
| | | | - Anne Martel
- Institut Laue-Langevin, 71 avenue des Martyrs, 38043 Grenoble, France
| | - Barbara Machado
- European Synchrotron Radiation Facility, 71 avenue des Martyrs, 38043 Grenoble, France
| | - Athina Zouni
- Humboldt Universität zu Berlin, Philipp Str. 13, 10115 Berlin, Germany
| | - Jörg Pieper
- Institute of Physics, University of Tartu, Wilhelm Ostwald str. 1, 50411 Tartu, Estonia
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14
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Sakers K, Eroglu C. Control of neural development and function by glial neuroligins. Curr Opin Neurobiol 2019; 57:163-170. [PMID: 30991196 DOI: 10.1016/j.conb.2019.03.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Revised: 03/12/2019] [Accepted: 03/13/2019] [Indexed: 11/16/2022]
Abstract
Neuroligins are a family of cell adhesion molecules, which are best known for their functions as postsynaptic components of the trans-synaptic neurexin-neuroligin complexes. Neuroligins are highly conserved across evolution with important roles in the formation, maturation and function of synaptic structures. Mutations in the genes that encode for neuroligins have been linked to a number of neurodevelopmental disorders such as autism and schizophrenia, which stem from synaptic pathologies. Owing to their essential functions in regulating synaptic connectivity and their link to synaptic dysfunction in disease, previous studies on neuroligins have focused on neurons. Yet a recent work reveals that neuroligins are also expressed in the central nervous system by glial cells, such as astrocytes and oligodendrocytes, and perform important roles in controlling synaptic connectivity in a non-cell autonomous manner. In this review, we will highlight these recent findings demonstrating the important roles of glial neuroligins in regulating the development and connectivity of healthy and diseased brains.
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Affiliation(s)
- Kristina Sakers
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, United States
| | - Cagla Eroglu
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, United States; Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, United States; Duke Institute for Brain Sciences (DIBS), Durham, NC 27710, United States; Regeneration Next Initiative, Duke University, Durham, NC 27710, United States.
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15
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Ranaivoson FM, Turk LS, Ozgul S, Kakehi S, von Daake S, Lopez N, Trobiani L, De Jaco A, Denissova N, Demeler B, Özkan E, Montelione GT, Comoletti D. A Proteomic Screen of Neuronal Cell-Surface Molecules Reveals IgLONs as Structurally Conserved Interaction Modules at the Synapse. Structure 2019; 27:893-906.e9. [PMID: 30956130 DOI: 10.1016/j.str.2019.03.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 01/10/2019] [Accepted: 03/07/2019] [Indexed: 12/21/2022]
Abstract
In the developing brain, cell-surface proteins play crucial roles, but their protein-protein interaction network remains largely unknown. A proteomic screen identified 200 interactions, 89 of which were not previously published. Among these interactions, we find that the IgLONs, a family of five cell-surface neuronal proteins implicated in various human disorders, interact as homo- and heterodimers. We reveal their interaction patterns and report the dimeric crystal structures of Neurotrimin (NTRI), IgLON5, and the neuronal growth regulator 1 (NEGR1)/IgLON5 complex. We show that IgLONs maintain an extended conformation and that their dimerization occurs through the first Ig domain of each monomer and is Ca2+ independent. Cell aggregation shows that NTRI and NEGR1 homo- and heterodimerize in trans. Taken together, we report 89 unpublished cell-surface ligand-receptor pairs and describe structural models of trans interactions of IgLONs, showing that their structures are compatible with a model of interaction across the synaptic cleft.
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Affiliation(s)
| | - Liam S Turk
- Child Health Institute of New Jersey, New Brunswick, NJ 08901, USA
| | - Sinem Ozgul
- Child Health Institute of New Jersey, New Brunswick, NJ 08901, USA
| | - Sumie Kakehi
- Child Health Institute of New Jersey, New Brunswick, NJ 08901, USA
| | | | - Nicole Lopez
- Child Health Institute of New Jersey, New Brunswick, NJ 08901, USA
| | - Laura Trobiani
- Department of Biology and Biotechnology "Charles Darwin" and Pasteur Institute - Cenci Bolognetti Foundation, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Antonella De Jaco
- Department of Biology and Biotechnology "Charles Darwin" and Pasteur Institute - Cenci Bolognetti Foundation, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Natalia Denissova
- Department of Molecular Biology and Biochemistry and Center for Advanced Biotechnology and Medicine, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA
| | - Borries Demeler
- Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive, Lethbridge, AB T1K 3M4, Canada
| | - Engin Özkan
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637, USA
| | - Gaetano T Montelione
- Department of Molecular Biology and Biochemistry and Center for Advanced Biotechnology and Medicine, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA; Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA
| | - Davide Comoletti
- Child Health Institute of New Jersey, New Brunswick, NJ 08901, USA; Departments of Neuroscience and Cell Biology Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901, USA; Department of Pediatrics, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901, USA; School of Biological Sciences, Victoria University of Wellington, Wellington 6140, New Zealand.
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16
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Chamma I, Sainlos M, Thoumine O. Biophysical mechanisms underlying the membrane trafficking of synaptic adhesion molecules. Neuropharmacology 2019; 169:107555. [PMID: 30831159 DOI: 10.1016/j.neuropharm.2019.02.037] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 02/14/2019] [Accepted: 02/27/2019] [Indexed: 01/13/2023]
Abstract
Adhesion proteins play crucial roles at synapses, not only by providing a physical trans-synaptic linkage between axonal and dendritic membranes, but also by connecting to functional elements including the pre-synaptic neurotransmitter release machinery and post-synaptic receptors. To mediate these functions, adhesion proteins must be organized on the neuronal surface in a precise and controlled manner. Recent studies have started to describe the mobility, nanoscale organization, and turnover rate of key synaptic adhesion molecules including cadherins, neurexins, neuroligins, SynCAMs, and LRRTMs, and show that some of these proteins are highly mobile in the plasma membrane while others are confined at sub-synaptic compartments, providing evidence for different regulatory pathways. In this review article, we provide a biophysical view of the diffusional trapping of adhesion molecules at synapses, involving both extracellular and intracellular protein interactions. We review the methodology underlying these measurements, including biomimetic systems with purified adhesion proteins, means to perturb protein expression or function, single molecule imaging in cultured neurons, and analytical models to interpret the data. This article is part of the special issue entitled 'Mobility and trafficking of neuronal membrane proteins'.
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Affiliation(s)
- Ingrid Chamma
- Univ. Bordeaux, Interdisciplinary Institute for Neuroscience, UMR 5297, F-33000, Bordeaux, France; CNRS, Interdisciplinary Institute for Neuroscience, UMR 5297, F-33000, Bordeaux, France
| | - Matthieu Sainlos
- Univ. Bordeaux, Interdisciplinary Institute for Neuroscience, UMR 5297, F-33000, Bordeaux, France; CNRS, Interdisciplinary Institute for Neuroscience, UMR 5297, F-33000, Bordeaux, France
| | - Olivier Thoumine
- Univ. Bordeaux, Interdisciplinary Institute for Neuroscience, UMR 5297, F-33000, Bordeaux, France; CNRS, Interdisciplinary Institute for Neuroscience, UMR 5297, F-33000, Bordeaux, France.
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17
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Jeon J, Oh MA, Cho W, Yoon SH, Kim JY, Chung TD. Robust Induced Presynapse on Artificial Substrates as a Neural Interfacing Method. ACS APPLIED MATERIALS & INTERFACES 2019; 11:7764-7773. [PMID: 30707832 DOI: 10.1021/acsami.8b20405] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Over the recent years, the development of neural interface systems has stuck to using electrical cues to stimulate neurons and read out neural signals, although neurons relay signals via chemical release and recognition at synapses. In addition, conventional neural interfaces are vulnerable to cell migration and glial encapsulation due to the absence of connection anchoring the neuron into the device unlike synapses, which are firmly sustained by protein bonding. To close this discrepancy, we conducted an intensive investigation into the induced synapse interface by employing engineered synaptic proteins from a neural interface perspective. The strong potential of induced synaptic differentiation as an emerging neural interfacing technique is demonstrated by exploring its structural features, chemical release kinetics, robustness, and scalability to the brain tissue. We show that the exocytosis kinetics of induced synapses is similar to that of endogenous synapses. Moreover, induced synapses show remarkable stability, despite cell migration and growth. The synapse-inducing technique has broad applications to cultured hippocampal and cortex tissues and suggests a promising method to integrate neural circuits with digital elements.
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Affiliation(s)
- Joohee Jeon
- Department of Chemistry , Seoul National University , Seoul 08826 , Republic of Korea
| | - Min-Ah Oh
- Department of Chemistry , Seoul National University , Seoul 08826 , Republic of Korea
| | - Wonkyung Cho
- Department of Chemistry , Seoul National University , Seoul 08826 , Republic of Korea
| | - Sun-Heui Yoon
- Department of Chemistry , Seoul National University , Seoul 08826 , Republic of Korea
| | - Ji Yong Kim
- Department of Chemistry , Seoul National University , Seoul 08826 , Republic of Korea
| | - Taek Dong Chung
- Department of Chemistry , Seoul National University , Seoul 08826 , Republic of Korea
- Advanced Institutes of Convergence Technology , Suwon-Si , Gyeonggi-do 16229 , Republic of Korea
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18
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Ozgul S, von Daake S, Kakehi S, Sereni D, Denissova N, Hanlon C, Huang YJ, Everett JK, Yin C, Montelione GT, Comoletti D. An ELISA-Based Screening Platform for Ligand–Receptor Discovery. Methods Enzymol 2019; 615:453-475. [DOI: 10.1016/bs.mie.2018.10.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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19
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Li Y, Liu H, Dong Y. Significance of neurexin and neuroligin polymorphisms in regulating risk of Hirschsprung's disease. J Investig Med 2018; 66:1-8. [PMID: 29622757 PMCID: PMC5992363 DOI: 10.1136/jim-2017-000623] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/29/2018] [Indexed: 12/27/2022]
Abstract
By performing a basic case-control study among a Chinese population, the aims of this study were to explore if single nucleotide polymorphisms (SNPs) within neurexin and neuroligin were associated with susceptibility to Hirschsprung's disease (HD). Eleven SNPs within neurexin and neuroligin were selected in this basic case-control study, and this study recruited 210 children with HD and 187 healthy children. The t-test and Χ2 test were used to find the difference between case and control in their clinical variables. OR and 95% CI were used to assess the association between HD susceptibility and neurexin/neuroligin polymorphisms/haplotypes. Several SNPs were significantly associated with altered risk of HD in the Chinese Han population, including rs1421589 within NRXN1, rs11795613 and rs4844285 within NLGN3, as well as rs5961397, rs7157669 and rs724373 within NLGX4X (all P<0.05). Further studies presented that the effects of rs1421589 within NRXN1, rs4844285 and rs11795613 within NLGN3, as well as rs5961397 within NLGX4X on HD phenotypes were also statistically significant (all P<0.05). Conclusively, the polymorphisms and haplotypes situated within neurexin and neuroligin were markedly associated with the onset of HD, implying that mutations of neurexin and neuroligin might serve as the treatment target for HD for the Chinese children.
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Affiliation(s)
- Yanhong Li
- Department of Pediatrics, Zhoukou Central Hospital, Zhoukou, Henan Province, China
| | - Hui Liu
- Department of Pediatrics, Zhoukou Central Hospital, Zhoukou, Henan Province, China
| | - Yubin Dong
- Department of Pediatrics, Zhoukou Central Hospital, Zhoukou, Henan Province, China
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20
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Südhof TC. Synaptic Neurexin Complexes: A Molecular Code for the Logic of Neural Circuits. Cell 2017; 171:745-769. [PMID: 29100073 DOI: 10.1016/j.cell.2017.10.024] [Citation(s) in RCA: 485] [Impact Index Per Article: 69.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Revised: 10/04/2017] [Accepted: 10/15/2017] [Indexed: 10/18/2022]
Abstract
Synapses are specialized junctions between neurons in brain that transmit and compute information, thereby connecting neurons into millions of overlapping and interdigitated neural circuits. Here, we posit that the establishment, properties, and dynamics of synapses are governed by a molecular logic that is controlled by diverse trans-synaptic signaling molecules. Neurexins, expressed in thousands of alternatively spliced isoforms, are central components of this dynamic code. Presynaptic neurexins regulate synapse properties via differential binding to multifarious postsynaptic ligands, such as neuroligins, cerebellin/GluD complexes, and latrophilins, thereby shaping the input/output relations of their resident neural circuits. Mutations in genes encoding neurexins and their ligands are associated with diverse neuropsychiatric disorders, especially schizophrenia, autism, and Tourette syndrome. Thus, neurexins nucleate an overall trans-synaptic signaling network that controls synapse properties, which thereby determines the precise responses of synapses to spike patterns in a neuron and circuit and which is vulnerable to impairments in neuropsychiatric disorders.
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Affiliation(s)
- Thomas C Südhof
- Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University Medical School, 265 Campus Drive, CA 94305-5453, USA.
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21
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Molumby MJ, Anderson RM, Newbold DJ, Koblesky NK, Garrett AM, Schreiner D, Radley JJ, Weiner JA. γ-Protocadherins Interact with Neuroligin-1 and Negatively Regulate Dendritic Spine Morphogenesis. Cell Rep 2017; 18:2702-2714. [PMID: 28297673 DOI: 10.1016/j.celrep.2017.02.060] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Revised: 01/18/2017] [Accepted: 02/20/2017] [Indexed: 10/20/2022] Open
Abstract
The 22 γ-Protocadherin (γ-Pcdh) cell adhesion molecules are critical for the elaboration of complex dendritic arbors in the cerebral cortex. Here, we provide evidence that the γ-Pcdhs negatively regulate synapse development by inhibiting the postsynaptic cell adhesion molecule, neuroligin-1 (Nlg1). Mice lacking all γ-Pcdhs in the forebrain exhibit significantly increased dendritic spine density in vivo, while spine density is significantly decreased in mice overexpressing one of the 22 γ-Pcdh isoforms. Co-expression of γ-Pcdhs inhibits the ability of Nlg1 to increase spine density and to induce presynaptic differentiation in hippocampal neurons in vitro. The γ-Pcdhs physically interact in cis with Nlg1 both in vitro and in vivo, and we present evidence that this disrupts Nlg1 binding to its presynaptic partner neurexin1β. Together with prior work, these data identify a mechanism through which γ-Pcdhs could coordinate dendrite arbor growth and complexity with spine maturation in the developing brain.
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Affiliation(s)
- Michael J Molumby
- Graduate Program in Genetics, The University of Iowa, Iowa City, IA 52242, USA; Department of Biology, The University of Iowa, Iowa City, IA 52242, USA
| | - Rachel M Anderson
- Department of Psychological and Brain Sciences, The University of Iowa, Iowa City, IA 52242, USA
| | - Dillan J Newbold
- Department of Biology, The University of Iowa, Iowa City, IA 52242, USA
| | - Norah K Koblesky
- Department of Biology, The University of Iowa, Iowa City, IA 52242, USA
| | - Andrew M Garrett
- Department of Biology, The University of Iowa, Iowa City, IA 52242, USA
| | - Dietmar Schreiner
- Department of Biology, The University of Iowa, Iowa City, IA 52242, USA
| | - Jason J Radley
- Department of Psychological and Brain Sciences, The University of Iowa, Iowa City, IA 52242, USA
| | - Joshua A Weiner
- Graduate Program in Genetics, The University of Iowa, Iowa City, IA 52242, USA; Department of Biology, The University of Iowa, Iowa City, IA 52242, USA; Department of Psychiatry, The University of Iowa, Iowa City, IA 52242, USA.
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22
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Elegheert J, Cvetkovska V, Clayton AJ, Heroven C, Vennekens KM, Smukowski SN, Regan MC, Jia W, Smith AC, Furukawa H, Savas JN, de Wit J, Begbie J, Craig AM, Aricescu AR. Structural Mechanism for Modulation of Synaptic Neuroligin-Neurexin Signaling by MDGA Proteins. Neuron 2017; 95:896-913.e10. [PMID: 28817804 PMCID: PMC5563082 DOI: 10.1016/j.neuron.2017.07.040] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2016] [Revised: 06/22/2017] [Accepted: 07/28/2017] [Indexed: 01/30/2023]
Abstract
Neuroligin-neurexin (NL-NRX) complexes are fundamental synaptic organizers in the central nervous system. An accurate spatial and temporal control of NL-NRX signaling is crucial to balance excitatory and inhibitory neurotransmission, and perturbations are linked with neurodevelopmental and psychiatric disorders. MDGA proteins bind NLs and control their function and interaction with NRXs via unknown mechanisms. Here, we report crystal structures of MDGA1, the NL1-MDGA1 complex, and a spliced NL1 isoform. Two large, multi-domain MDGA molecules fold into rigid triangular structures, cradling a dimeric NL to prevent NRX binding. Structural analyses guided the discovery of a broad, splicing-modulated interaction network between MDGA and NL family members and helped rationalize the impact of autism-linked mutations. We demonstrate that expression levels largely determine whether MDGAs act selectively or suppress the synapse organizing function of multiple NLs. These results illustrate a potentially brain-wide regulatory mechanism for NL-NRX signaling modulation. The MDGA1 extracellular region has an unusual triangular multi-domain arrangement The NL1-MDGA1 complex structure reveals how MDGA proteins block neurexin binding MDGA1 and MDGA2 bind all NL isoforms, a process fine-tuned by alternative splicing MDGA1 and MDGA2 suppress NL synaptogenic activity in a concentration-dependent manner
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Affiliation(s)
- Jonathan Elegheert
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK.
| | - Vedrana Cvetkovska
- Djavad Mowafaghian Centre for Brain Health and Department of Psychiatry, University of British Columbia, Vancouver, BC V6T 2B5, Canada
| | - Amber J Clayton
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - Christina Heroven
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK; MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK
| | - Kristel M Vennekens
- VIB Center for Brain and Disease Research, Herestraat 49, B-3000 Leuven, Belgium; Department of Neurosciences, KU Leuven, Herestraat 49, B-3000 Leuven, Belgium
| | - Samuel N Smukowski
- Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Michael C Regan
- Keck Structural Biology Laboratory, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, USA
| | - Wanyi Jia
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - Alexandra C Smith
- Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX1 3QX, UK
| | - Hiro Furukawa
- Keck Structural Biology Laboratory, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, USA
| | - Jeffrey N Savas
- Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Joris de Wit
- VIB Center for Brain and Disease Research, Herestraat 49, B-3000 Leuven, Belgium; Department of Neurosciences, KU Leuven, Herestraat 49, B-3000 Leuven, Belgium
| | - Jo Begbie
- Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX1 3QX, UK
| | - Ann Marie Craig
- Djavad Mowafaghian Centre for Brain Health and Department of Psychiatry, University of British Columbia, Vancouver, BC V6T 2B5, Canada.
| | - A Radu Aricescu
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK; MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK.
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23
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Unique versus Redundant Functions of Neuroligin Genes in Shaping Excitatory and Inhibitory Synapse Properties. J Neurosci 2017; 37:6816-6836. [PMID: 28607166 DOI: 10.1523/jneurosci.0125-17.2017] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2017] [Revised: 05/10/2017] [Accepted: 05/31/2017] [Indexed: 11/21/2022] Open
Abstract
Neuroligins are evolutionarily conserved postsynaptic cell adhesion molecules that interact with presynaptic neurexins. Neurons express multiple neuroligin isoforms that are targeted to specific synapses, but their synaptic functions and mechanistic redundancy are not completely understood. Overexpression or RNAi-mediated knockdown of neuroligins, respectively, causes a dramatic increase or decrease in synapse density, whereas genetic deletions of neuroligins impair synapse function with only minor effects on synapse numbers, raising fundamental questions about the overall physiological role of neuroligins. Here, we have systematically analyzed the effects of conditional genetic deletions of all major neuroligin isoforms (i.e., NL1, NL2, and NL3), either individually or in combinations, in cultured mouse hippocampal and cortical neurons. We found that conditional genetic deletions of neuroligins caused no change or only a small change in synapses numbers, but strongly impaired synapse function. This impairment was isoform specific, suggesting that neuroligins are not functionally redundant. Sparse neuroligin deletions produced phenotypes comparable to those of global deletions, indicating that neuroligins function in a cell-autonomous manner. Mechanistically, neuroligin deletions decreased the synaptic levels of neurotransmitter receptors and had no effect on presynaptic release probabilities. Overexpression of neuroligin-1 in control or neuroligin-deficient neurons increased synaptic transmission and synapse density but not spine numbers, suggesting that these effects reflect a gain-of-function mechanism; whereas overexpression of neuroligin-3, which, like neuroligin-1 is also targeted to excitatory synapses, had no comparable effect. Our data demonstrate that neuroligins are required for the physiological organization of neurotransmitter receptors in postsynaptic specializations and suggest that they do not play a major role in synapse formation.SIGNIFICANCE STATEMENT Human neuroligin genes have been associated with autism, but the cellular functions of different neuroligins and their molecular mechanisms remain incompletely understood. Here, we performed comparative analyses in cultured mouse neurons of all major neuroligin isoforms, either individually or in combinations, using conditional knockouts. We found that neuroligin deletions did not affect synapse numbers but differentially impaired excitatory or inhibitory synaptic functions in an isoform-specific manner. These impairments were due, at least in part, to a decrease in synaptic distribution of neurotransmitter receptors upon deletion of neuroligins. Conversely, the overexpression of neuroligin-1 increased synapse numbers but not spine numbers. Our results suggest that various neuroligin isoforms perform unique postsynaptic functions in organizing synapses but are not essential for synapse formation or maintenance.
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24
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Jeong J, Paskus JD, Roche KW. Posttranslational modifications of neuroligins regulate neuronal and glial signaling. Curr Opin Neurobiol 2017; 45:130-138. [PMID: 28577430 DOI: 10.1016/j.conb.2017.05.017] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 05/02/2017] [Accepted: 05/12/2017] [Indexed: 12/29/2022]
Abstract
This review covers the dynamic regulation of neuroligin isoforms, focusing on posttranslational events including phosphorylation, glycosylation and activity-dependent cleavage. There is a growing literature on how phosphorylation confers an isoform-specific level of modulation affecting a variety of protein interactions. In addition, recent studies describe activity-dependent proteolytic cleavage of neuroligins, revealing a broader role for neuroligins than just synaptic 'glue'. Interesting new research implicates the cleaved extracellular fragments of neuroligins in promoting glioma. These reports on cell signaling mediated by the cleavage products of neuroligins suggest novel and important roles for neuroligins in neuro-glial signaling.
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Affiliation(s)
- Jaehoon Jeong
- Receptor Biology Section, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health, Bethesda, MD 20892, USA
| | - Jeremiah D Paskus
- Receptor Biology Section, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health, Bethesda, MD 20892, USA; Interdisciplinary Program in Neuroscience, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Katherine W Roche
- Receptor Biology Section, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health, Bethesda, MD 20892, USA.
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Abstract
This protocol describes an in situ protein-protein interaction assay between tagged recombinant proteins and cell-surface expressed synaptic proteins. The assay is arguably more sensitive than other traditional protein binding assays such as co-immunoprecipitation and pull-downs and provides a visual readout for binding. This assay has been widely used to determine the dissociation constant of binding of trans-synaptic adhesion proteins. The step-wise description in the protocol should facilitate the adoption of this method in other laboratories.
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Affiliation(s)
- Nirmala Padmanabhan
- Department of Physiology and Pathophysiology, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada
- Neuroscience Research Program, Kleysen Institute for Advanced Medicine, Health Sciences Centre, University of Manitoba, 710 William Avenue, Winnipeg, MB, Canada, R3E 0Z3
| | - Tabrez J Siddiqui
- Department of Physiology and Pathophysiology, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada.
- Neuroscience Research Program, Kleysen Institute for Advanced Medicine, Health Sciences Centre, University of Manitoba, 710 William Avenue, Winnipeg, MB, Canada, R3E 0Z3.
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Nguyen QA, Horn ME, Nicoll RA. Distinct roles for extracellular and intracellular domains in neuroligin function at inhibitory synapses. eLife 2016; 5. [PMID: 27805570 PMCID: PMC5098909 DOI: 10.7554/elife.19236] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 11/01/2016] [Indexed: 11/17/2022] Open
Abstract
Neuroligins (NLGNs) are postsynaptic cell adhesion molecules that interact trans-synaptically with neurexins to mediate synapse development and function. NLGN2 is only at inhibitory synapses while NLGN3 is at both excitatory and inhibitory synapses. We found that NLGN3 function at inhibitory synapses in rat CA1 depends on the presence of NLGN2 and identified a domain in the extracellular region that accounted for this functional difference between NLGN2 and 3 specifically at inhibitory synapses. We further show that the presence of a cytoplasmic tail (c-tail) is indispensible, and identified two domains in the c-tail that are necessary for NLGN function at inhibitory synapses. These domains point to a gephyrin-dependent mechanism that is disrupted by an autism-associated mutation at R705 and a gephyrin-independent mechanism reliant on a putative phosphorylation site at S714. Our work highlights unique and separate roles for the extracellular and intracellular regions in specifying and carrying out NLGN function respectively. DOI:http://dx.doi.org/10.7554/eLife.19236.001
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Affiliation(s)
- Quynh-Anh Nguyen
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, United States.,Neuroscience Graduate Program, University of California, San Francisco, San Francisco, United States
| | - Meryl E Horn
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, United States.,Neuroscience Graduate Program, University of California, San Francisco, San Francisco, United States
| | - Roger A Nicoll
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, United States.,Department of Physiology, University of California, San Francisco, San Francisco, United States
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27
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Chamma I, Levet F, Sibarita JB, Sainlos M, Thoumine O. Nanoscale organization of synaptic adhesion proteins revealed by single-molecule localization microscopy. NEUROPHOTONICS 2016; 3:041810. [PMID: 27872870 PMCID: PMC5093229 DOI: 10.1117/1.nph.3.4.041810] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Accepted: 10/11/2016] [Indexed: 06/06/2023]
Abstract
The advent of superresolution imaging has created a strong need for both optimized labeling strategies and analysis methods to probe the nanoscale organization of complex biological structures. We present a thorough description of the distribution of synaptic adhesion proteins at the nanoscopic scale, namely presynaptic neurexin-[Formula: see text] ([Formula: see text]), and its two postsynaptic binding partners neuroligin-1 (Nlg1) and leucine-rich-repeat transmembrane protein 2 (LRRTM2). We monitored these proteins in the membrane of neurons by direct stochastic optical reconstruction microscopy, after live surface labeling with Alexa647-conjugated monomeric streptavidin. The small probe ([Formula: see text]) efficiently penetrates into crowded synaptic junctions and reduces the distance to target. We quantified the organization of the single-molecule localization data using a tesselation-based analysis technique. We show that Nlg1 exhibits a fairly disperse organization within dendritic spines, while LRRTM2 is organized in compact domains, and [Formula: see text] in presynaptic terminals displays a dual-organization pattern intermediate between that of Nlg1 and LRRTM2. These results suggest that part of [Formula: see text] interacts transsynaptically with Nlg1 and the other part with LRRTM2.
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Affiliation(s)
- Ingrid Chamma
- Centre National de la Recherche Scientifique, Interdisciplinary Institute for Neuroscience, UMR 5297, 147 rue Léo-Saignat, Bordeaux Cedex 33077, France
- University of Bordeaux, Interdisciplinary Institute for Neuroscience, 147 rue Léo-Saignat, Bordeaux Cedex 33077, France
| | - Florian Levet
- Centre National de la Recherche Scientifique, Interdisciplinary Institute for Neuroscience, UMR 5297, 147 rue Léo-Saignat, Bordeaux Cedex 33077, France
- University of Bordeaux, Interdisciplinary Institute for Neuroscience, 147 rue Léo-Saignat, Bordeaux Cedex 33077, France
| | - Jean-Baptiste Sibarita
- Centre National de la Recherche Scientifique, Interdisciplinary Institute for Neuroscience, UMR 5297, 147 rue Léo-Saignat, Bordeaux Cedex 33077, France
- University of Bordeaux, Interdisciplinary Institute for Neuroscience, 147 rue Léo-Saignat, Bordeaux Cedex 33077, France
| | - Matthieu Sainlos
- Centre National de la Recherche Scientifique, Interdisciplinary Institute for Neuroscience, UMR 5297, 147 rue Léo-Saignat, Bordeaux Cedex 33077, France
- University of Bordeaux, Interdisciplinary Institute for Neuroscience, 147 rue Léo-Saignat, Bordeaux Cedex 33077, France
| | - Olivier Thoumine
- Centre National de la Recherche Scientifique, Interdisciplinary Institute for Neuroscience, UMR 5297, 147 rue Léo-Saignat, Bordeaux Cedex 33077, France
- University of Bordeaux, Interdisciplinary Institute for Neuroscience, 147 rue Léo-Saignat, Bordeaux Cedex 33077, France
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28
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Cao X, Tabuchi K. Functions of synapse adhesion molecules neurexin/neuroligins and neurodevelopmental disorders. Neurosci Res 2016; 116:3-9. [PMID: 27664583 DOI: 10.1016/j.neures.2016.09.005] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 09/02/2016] [Accepted: 09/02/2016] [Indexed: 12/15/2022]
Abstract
Neurexins and neuroligins are two distinct families of single-pass transmembrane proteins localized at pre- and postsynapses, respectively. They trans-synaptically interact with each other and induce synapse formation and maturation. Common variants and rare mutations, including copy number variations, short deletions, and single or small nucleotide changes in neurexin and neuroligin genes have been linked to the neurodevelopmental disorders, such as autism spectrum disorders (ASDs). In this review, we summarize the structure and basic synaptic function of neurexins and neuroligins, followed by behaviors and synaptic phenotypes of knock-in and knock-out mouse of these family genes. From the studies of these mice, it turns out that the effects of neurexins and neuroligins are amazingly neural circuit dependent, even within the same brain region. In addition, neurexins and neuroligins are commonly involved in the endocannabinoid signaling. These finding may provide not only insight into understanding the pathophysiology, but also the concept for strategy of therapeutic intervention for ASDs.
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Affiliation(s)
- Xueshan Cao
- Department of Molecular & Cellular Physiology, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan
| | - Katsuhiko Tabuchi
- Department of Molecular & Cellular Physiology, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan; Institute for Biomedical Sciences, Interdisciplinary Cluster for Cutting Edge Research, Shinshu University, Matsumoto 390-8621, Japan.
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29
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Kim EJ, Jeon CS, Lee SY, Hwang I, Chung TD. Robust Type-specific Hemisynapses Induced by Artificial Dendrites. Sci Rep 2016; 6:24210. [PMID: 27072994 PMCID: PMC4829863 DOI: 10.1038/srep24210] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Accepted: 03/22/2016] [Indexed: 11/09/2022] Open
Abstract
Type-specificity of synapses, excitatory and inhibitory, regulates information process in neural networks via chemical neurotransmitters. To lay a foundation of synapse-based neural interfaces, artificial dendrites are generated by covering abiotic substrata with ectodomains of type-specific synaptogenic proteins that are C-terminally tagged with biotinylated fluorescent proteins. The excitatory artificial synapses displaying engineered ectodomains of postsynaptic neuroligin-1 (NL1) induce the formation of excitatory presynapses with mixed culture of neurons in various developmental stages, while the inhibitory artificial dendrites displaying engineered NL2 and Slitrk3 induce inhibitory presynapses only with mature neurons. By contrast, if the artificial dendrites are applied to the axonal components of micropatterned neurons, correctly-matched synaptic specificity emerges regardless of the neuronal developmental stages. The hemisynapses retain their initially established type-specificity during neuronal development and maintain their synaptic strength provided live neurons, implying the possibility of durable synapse-based biointerfaces.
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Affiliation(s)
- Eun Joong Kim
- Department of Chemistry, Seoul National University, Seoul, 08826, Korea
| | - Chang Su Jeon
- Department of Chemistry, Seoul National University, Seoul, 08826, Korea
| | - Soo Youn Lee
- Department of Chemistry, Seoul National University, Seoul, 08826, Korea
| | - Inseong Hwang
- Department of Chemistry, Seoul National University, Seoul, 08826, Korea
| | - Taek Dong Chung
- Department of Chemistry, Seoul National University, Seoul, 08826, Korea
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30
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Sindi IA, Dodd PR. New insights into Alzheimer's disease pathogenesis: the involvement of neuroligins in synaptic malfunction. Neurodegener Dis Manag 2016; 5:137-45. [PMID: 25894877 DOI: 10.2217/nmt.14.54] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Synaptic damage is a key hallmark of Alzheimer's disease and the best correlate with cognitive decline ante mortem. Signature protein combinations arrayed at tightly apposed pre- and post-synaptic sites characterize different types of synapse. Neuroligins are postsynaptic cell adhesion molecules that interact with neurexins across the synaptic cleft. These pairings recruit receptors, channels and signal transduction molecules to the synapse, and help mediate trans-synaptic transmission. Dysfunction in the neuroligin family can disrupt neuronal networks and leads to neurodegeneration and other diseases. The extracellular domain of neuroligins is homologous with acetylcholinesterase but lacks residues required for enzymatic activity. This domain may interact pathogenically with β-amyloid. Here we summarize research over the last decade on the potential involvement of neuroligins in Alzheimer's disease.
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Affiliation(s)
- Ikhlas A Sindi
- Centre for Psychiatry & Clinical Neuroscience, School of Medicine, Australia
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31
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Dinamarca MC, Di Luca M, Godoy JA, Inestrosa NC. The soluble extracellular fragment of neuroligin-1 targets Aβ oligomers to the postsynaptic region of excitatory synapses. Biochem Biophys Res Commun 2015; 466:66-71. [DOI: 10.1016/j.bbrc.2015.08.107] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Accepted: 08/24/2015] [Indexed: 11/30/2022]
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32
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Abstract
A fundamental physical interaction exists across the synapse. It is mediated by synaptic adhesion molecules, and is among the earliest and most indispensable of molecular events occurring during synaptogenesis. The regulation of adhesion molecules and their interactions with other synaptic proteins likely affect not only on synapse formation but also on ongoing synaptic function. We review research on one major family of postsynaptic adhesion molecules, neuroligins, which bind to their presynaptic partner neurexin across the synaptic cleft. We move from a structural overview to the broad cellular and synaptic context of neuroligins, intermolecular interactions, and molecular modifications that occur within a synapse. Finally, we examine evidence concerning the physiological functions of neuroligin in a cell and highlight areas requiring further investigation.
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Affiliation(s)
- Michael A Bemben
- Receptor Biology Section, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health, Bethesda, MD 20892, USA; Department of Biology, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD, 21218, USA
| | - Seth L Shipman
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA; Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA 02138, USA
| | - Roger A Nicoll
- Departments of Cellular and Molecular Pharmacology and Physiology, University of California, San Francisco, San Francisco, CA 94158, USA.
| | - Katherine W Roche
- Receptor Biology Section, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health, Bethesda, MD 20892, USA.
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33
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Proctor DT, Stotz SC, Scott LOM, de la Hoz CLR, Poon KWC, Stys PK, Colicos MA. Axo-glial communication through neurexin-neuroligin signaling regulates myelination and oligodendrocyte differentiation. Glia 2015; 63:2023-2039. [PMID: 26119281 DOI: 10.1002/glia.22875] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 05/25/2015] [Accepted: 06/02/2015] [Indexed: 12/13/2022]
Abstract
Axonal transsynaptic signaling between presynaptic neurexin (NX) and postsynaptic neuroligin (NL) is essential for many properties of synaptic connectivity. Here, we demonstrate the existence of a parallel axo-glial signaling pathway between axonal NX and oligodendritic (OL) NL3. We show that this pathway contributes to the regulation of myelinogenesis, the maintenance of established myelination, and the differentiation state of the OL using in vitro models. We first confirm that NL3 mRNA and protein are expressed in OLs and in OL precursors. We then show that OLs in culture form contacts with non-neuronal cells exogenously expressing NL3's binding partners NX1α or NX1β. Conversely, blocking axo-glial NX-NL3 signaling by saturating NX with exogenous soluble NL protein (NL-ECD) disrupts interactions between OLs and axons in both in vitro and ex vivo assays. Myelination by OLs is tied to their differentiation state, and we find that blocking NX-NL signaling with soluble NL protein also caused OL differentiation to stall at an immature stage. Moreover, in vitro knockdown of NL3 in OLs with siRNAs stalls their development and reduces branching complexity. Interestingly, inclusion of an autism related mutation in the NL blocking protein attenuates these effects; OLs differentiate and the dynamics of OL-axon signaling occur normally as this peptide does not disrupt NX-NL3 axo-glial interactions. Our findings provide evidence not only for a new pathway in axo-glial communication, they also potentially explain the correlation between altered white matter and autism. GLIA 2015;63:2023-2039.
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Affiliation(s)
- Dustin T Proctor
- Department of Physiology & Pharmacology, Faculty of Medicine, and the Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada, T2N 4N1
| | - Stephanie C Stotz
- Department of Physiology & Pharmacology, Faculty of Medicine, and the Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada, T2N 4N1
| | - Lucas O M Scott
- Department of Physiology & Pharmacology, Faculty of Medicine, and the Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada, T2N 4N1
| | - Cristiane L R de la Hoz
- Department of Physiology & Pharmacology, Faculty of Medicine, and the Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada, T2N 4N1
| | - Kelvin W C Poon
- Department of Clinical Neurosciences, Faculty of Medicine and the Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada, T2N 4N1
| | - Peter K Stys
- Department of Clinical Neurosciences, Faculty of Medicine and the Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada, T2N 4N1
| | - Michael A Colicos
- Department of Physiology & Pharmacology, Faculty of Medicine, and the Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada, T2N 4N1
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Wang B, Guo W, Huang Y. Thrombospondins and synaptogenesis. Neural Regen Res 2015; 7:1737-43. [PMID: 25624796 PMCID: PMC4302456 DOI: 10.3969/j.issn.1673-5374.2012.22.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Accepted: 05/03/2012] [Indexed: 12/28/2022] Open
Abstract
Here, we review research on the mechanisms underlying the ability of thrombospondin to promote synaptogenesis and examine its role in central nervous system diseases and drug actions. Thrombospondin secreted by glial cells plays a critical role in synaptogenesis and maintains synapse stability. Thrombospondin regulates synaptogenesis through receptor α2δ-1 and neuroligin 1, and promotes the proliferation and differentiation of neural progenitor cells. It also participates in synaptic remodeling following injury and in the action of some nervous system drugs.
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Affiliation(s)
- Bin Wang
- Department of Orthopedics, Affiliated Hospital of Guangdong Medical College, Zhanjiang 524001, Guangdong Province, China
| | - Weitao Guo
- Department of Orthopedics, Affiliated Hospital of Guangdong Medical College, Zhanjiang 524001, Guangdong Province, China
| | - Yun Huang
- Department of Orthopedics, Affiliated Hospital of Guangdong Medical College, Zhanjiang 524001, Guangdong Province, China
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Conserved and divergent processing of neuroligin and neurexin genes: from the nematode C. elegans to human. INVERTEBRATE NEUROSCIENCE 2014; 14:79-90. [PMID: 25148907 DOI: 10.1007/s10158-014-0173-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Accepted: 08/11/2014] [Indexed: 01/17/2023]
Abstract
Neuroligins are cell-adhesion proteins that interact with neurexins at the synapse. This interaction may contribute to differentiation, plasticity and specificity of synapses. In humans, single mutations in neuroligin-encoding genes are implicated in autism spectrum disorder and/or mental retardation. Moreover, some copy number variations and point mutations in neurexin-encoding genes have been linked to neurodevelopmental disorders including autism. Neurexins are subject to extensive alternative splicing, highly regulated in mammals, with a great physiological importance. In addition, neuroligins and neurexins are subjected to proteolytic processes that regulate synaptic transmission modifying pre- and postsynaptic activities and may also regulate the remodelling of spines at specific synapses. Four neuroligin genes exist in mice and five in human, whilst in the nematode Caenorhabditis elegans, there is only one orthologous gene. In a similar manner, in mammals, there are three neurexin genes, each of them encoding two major isoforms named α and β, respectively. In contrast, there is one neurexin gene in C. elegans that also generates two isoforms like mammals. The complexity of the genetic organization of neurexins is due to extensive processing resulting in hundreds of isoforms. In this review, a wide comparison is made between the genes in the nematode and human with a view to better understanding the conservation of processing in these synaptic proteins in C. elegans, which may serve as a genetic model to decipher the synaptopathies underpinning neurodevelopmental disorders such as autism.
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Xiang YY, Dong H, Yang BB, Macdonald JF, Lu WY. Interaction of acetylcholinesterase with neurexin-1β regulates glutamatergic synaptic stability in hippocampal neurons. Mol Brain 2014; 7:15. [PMID: 24594013 PMCID: PMC3973991 DOI: 10.1186/1756-6606-7-15] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2013] [Accepted: 02/27/2014] [Indexed: 02/11/2023] Open
Abstract
Background Excess expression of acetylcholinesterase (AChE) in the cortex and hippocampus causes a decrease in the number of glutamatergic synapses and alters the expression of neurexin and neuroligin, trans-synaptic proteins that control synaptic stability. The molecular sequence and three-dimensional structure of AChE are homologous to the corresponding aspects of the ectodomain of neuroligin. This study investigated whether excess AChE interacts physically with neurexin to destabilize glutamatergic synapses. Results The results showed that AChE clusters colocalized with neurexin assemblies in the neurites of hippocampal neurons and that AChE co-immunoprecipitated with neurexin from the lysate of these neurons. Moreover, when expressed in human embryonic kidney 293 cells, N-glycosylated AChE co-immunoprecipitated with non-O–glycosylated neurexin-1β, with N-glycosylation of the AChE being required for this co-precipitation to occur. Increasing extracellular AChE decreased the association of neurexin with neuroligin and inhibited neuroligin-induced synaptogenesis. The number and activity of excitatory synapses in cultured hippocampal neurons were reduced by extracellular catalytically inactive AChE. Conclusions Excessive glycosylated AChE could competitively disrupt a subset of the neurexin–neuroligin junctions consequently impairing the integrity of glutamatergic synapses. This might serve a molecular mechanism of excessive AChE induced neurodegeneration.
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Affiliation(s)
| | | | | | | | - Wei-Yang Lu
- Robarts Research Institute, University of Western Ontario, London, Ontario, Canada.
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37
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Sindi IA, Tannenberg RK, Dodd PR. Role for the neurexin-neuroligin complex in Alzheimer's disease. Neurobiol Aging 2013; 35:746-56. [PMID: 24211009 DOI: 10.1016/j.neurobiolaging.2013.09.032] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Revised: 09/20/2013] [Accepted: 09/22/2013] [Indexed: 11/29/2022]
Abstract
Synaptic damage is a critical hallmark of Alzheimer's disease, and the best correlate with cognitive impairment ante mortem. Synapses, the loci of communication between neurons, are characterized by signature protein combinations arrayed at tightly apposed pre- and post-synaptic sites. The most widely studied trans-synaptic junctional complexes, which direct synaptogenesis and foster the maintenance and stability of the mature terminal, are conjunctions of presynaptic neurexins and postsynaptic neuroligins. Fluctuations in the levels of neuroligins and neurexins can sway the balance between excitatory and inhibitory neurotransmission in the brain, and could lead to damage of synapses and dendrites. This review summarizes current understanding of the roles of neurexins and neuroligins proteolytic processing in synaptic plasticity in the human brain, and outlines their possible roles in β-amyloid metabolism and function, which are central pathogenic events in Alzheimer's disease progression.
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Affiliation(s)
- Ikhlas A Sindi
- Centre for Psychiatry and Clinical Neuroscience, School of Medicine, The University of Queensland, Brisbane, Australia
| | - Rudolph K Tannenberg
- Centre for Psychiatry and Clinical Neuroscience, School of Medicine, The University of Queensland, Brisbane, Australia; School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia
| | - Peter R Dodd
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia.
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38
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Contribution of Postsynaptic GluD2 to Presynaptic R-type Ca2+ Channel Function, Glutamate Release and Long-term Potentiation at Parallel Fiber to Purkinje Cell Synapses. THE CEREBELLUM 2013; 12:657-66. [DOI: 10.1007/s12311-013-0474-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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39
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Bang ML, Owczarek S. A Matter of Balance: Role of Neurexin and Neuroligin at the Synapse. Neurochem Res 2013; 38:1174-89. [DOI: 10.1007/s11064-013-1029-9] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Revised: 02/01/2013] [Accepted: 03/26/2013] [Indexed: 11/29/2022]
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40
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Drosophila neuroligin 2 is required presynaptically and postsynaptically for proper synaptic differentiation and synaptic transmission. J Neurosci 2013; 32:16018-30. [PMID: 23136438 DOI: 10.1523/jneurosci.1685-12.2012] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Trans-synaptic adhesion between Neurexins (Nrxs) and Neuroligins (Nlgs) is thought to be required for proper synapse organization and modulation, and mutations in several human Nlgs have shown association with autism spectrum disorders. Here we report the generation and phenotypic characterization of Drosophila neuroligin 2 (dnlg2) mutants. Loss of dnlg2 results in reduced bouton numbers, aberrant presynaptic and postsynaptic development at neuromuscular junctions (NMJs), and impaired synaptic transmission. In dnlg2 mutants, the evoked responses are decreased in amplitude, whereas the total active zone (AZ) numbers at the NMJ are comparable to wild type, suggesting a decrease in the release probability. Ultrastructurally, the presynaptic AZ number per bouton area and the postsynaptic density area are both increased in dnlg2 mutants, whereas the subsynaptic reticulum is reduced in volume. We show that both presynaptic and postsynaptic expression of Dnlg2 is required to restore synaptic growth and function in dnlg2 mutants. Postsynaptic expression of Dnlg2 in dnlg2 mutants and wild type leads to reduced bouton growth whereas presynaptic and postsynaptic overexpression in wild-type animals results in synaptic overgrowth. Since Nlgs have been shown to bind to Nrxs, we created double mutants. These mutants are viable and display phenotypes that closely resemble those of dnlg2 and dnrx single mutants. Our results provide compelling evidence that Dnlg2 functions both presynaptically and postsynaptically together with Neurexin to determine the proper number of boutons as well as the number of AZs and size of synaptic densities during the development of NMJs.
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41
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Mishina M, Uemura T, Yasumura M, Yoshida T. Molecular mechanism of parallel fiber-Purkinje cell synapse formation. Front Neural Circuits 2012. [PMID: 23189042 PMCID: PMC3505014 DOI: 10.3389/fncir.2012.00090] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The cerebellum receives two excitatory afferents, the climbing fiber (CF) and the mossy fiber-parallel fiber (PF) pathway, both converging onto Purkinje cells (PCs) that are the sole neurons sending outputs from the cerebellar cortex. Glutamate receptor δ2 (GluRδ2) is expressed selectively in cerebellar PCs and localized exclusively at the PF-PC synapses. We found that a significant number of PC spines lack synaptic contacts with PF terminals and some of residual PF-PC synapses show mismatching between pre- and postsynaptic specializations in conventional and conditional GluRδ2 knockout mice. Studies with mutant mice revealed that in addition to PF-PC synapse formation, GluRδ2 is essential for synaptic plasticity, motor learning, and the restriction of CF territory. GluRδ2 regulates synapse formation through the amino-terminal domain, while the control of synaptic plasticity, motor learning, and CF territory is mediated through the carboxyl-terminal domain. Thus, GluRδ2 is the molecule that bridges synapse formation and motor learning. We found that the trans-synaptic interaction of postsynaptic GluRδ2 and presynaptic neurexins (NRXNs) through cerebellin 1 (Cbln1) mediates PF-PC synapse formation. The synaptogenic triad is composed of one molecule of tetrameric GluRδ2, two molecules of hexameric Cbln1 and four molecules of monomeric NRXN. Thus, GluRδ2 triggers synapse formation by clustering four NRXNs. These findings provide a molecular insight into the mechanism of synapse formation in the brain.
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Affiliation(s)
- Masayoshi Mishina
- Brain Science Laboratory, The Research Organization of Science and Technology, Ritsumeikan University Shiga, Japan ; Molecular Neurobiology and Pharmacology, Graduate School of Medicine, The University of Tokyo Tokyo, Japan
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De Jaco A, Dubi N, Camp S, Taylor P. Congenital hypothyroidism mutations affect common folding and trafficking in the α/β-hydrolase fold proteins. FEBS J 2012; 279:4293-305. [PMID: 23035660 DOI: 10.1111/febs.12019] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Revised: 09/27/2012] [Accepted: 09/28/2012] [Indexed: 12/19/2022]
Abstract
The α/β-hydrolase fold superfamily of proteins is composed of structurally related members that, despite great diversity in their catalytic, recognition, adhesion and chaperone functions, share a common fold governed by homologous residues and conserved disulfide bridges. Non-synonymous single nucleotide polymorphisms within the α/β-hydrolase fold domain in various family members have been found for congenital endocrine, metabolic and nervous system disorders. By examining the amino acid sequence from the various proteins, mutations were found to be prevalent in conserved residues within the α/β-hydrolase fold of the homologous proteins. This is the case for the thyroglobulin mutations linked to congenital hypothyroidism. To address whether correct folding of the common domain is required for protein export, we inserted the thyroglobulin mutations at homologous positions in two correlated but simpler α/β-hydrolase fold proteins known to be exported to the cell surface: neuroligin3 and acetylcholinesterase. Here we show that these mutations in the cholinesterase homologous region alter the folding properties of the α/β-hydrolase fold domain, which are reflected in defects in protein trafficking, folding and function, and ultimately result in retention of the partially processed proteins in the endoplasmic reticulum. Accordingly, mutations at conserved residues may be transferred amongst homologous proteins to produce common processing defects despite disparate functions, protein complexity and tissue-specific expression of the homologous proteins. More importantly, a similar assembly of the α/β-hydrolase fold domain tertiary structure among homologous members of the superfamily is required for correct trafficking of the proteins to their final destination.
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Affiliation(s)
- Antonella De Jaco
- Department of Pharmacology, Skaggs School of Pharmacy & Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA, USA.
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Falivelli G, De Jaco A, Favaloro FL, Kim H, Wilson J, Dubi N, Ellisman MH, Abrahams BS, Taylor P, Comoletti D. Inherited genetic variants in autism-related CNTNAP2 show perturbed trafficking and ATF6 activation. Hum Mol Genet 2012; 21:4761-73. [PMID: 22872700 DOI: 10.1093/hmg/dds320] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Although genetic variations in several genes encoding for synaptic adhesion proteins have been found to be associated with autism spectrum disorders, one of the most consistently replicated genes has been CNTNAP2, encoding for contactin-associated protein-like 2 (CASPR2), a multidomain transmembrane protein of the neurexin superfamily. Using immunofluorescence confocal microscopy and complementary biochemical techniques, we compared wild-type CASPR2 to 12 point mutations identified in individuals with autism. In contrast to the wild-type protein, localized to the cell surface, some of the mutants show altered cellular disposition. In particular, CASPR2-D1129H is largely retained in the endoplasmic reticulum (ER) in HEK-293 cells and in hippocampal neurons. BiP/Grp78, Calnexin and ERp57, key ER chaperones, appear to be responsible for retention of this mutant and activation of one signaling pathway of the unfolded protein response (UPR). The presence of this mutation also lowers expression and activates proteosomal degradation. A frame-shift mutation that causes a form of syndromic epilepsy (CASPR2-1253*), results in a secreted protein with seemingly normal folding and oligomerization. Taken together, these data indicate that CASPR2-D1129H has severe trafficking abnormalities and CASPR2-1253* is a secreted soluble protein, suggesting that the structural or signaling functions of the membrane tethered form are lost. Our data support a complex genetic architecture in which multiple distinct risk factors interact with others to shape autism risk and presentation.
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Affiliation(s)
- Giulia Falivelli
- Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA 92093, USA
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Functional phenotypic rescue of Caenorhabditis elegans neuroligin-deficient mutants by the human and rat NLGN1 genes. PLoS One 2012; 7:e39277. [PMID: 22723984 PMCID: PMC3377638 DOI: 10.1371/journal.pone.0039277] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Accepted: 05/22/2012] [Indexed: 01/28/2023] Open
Abstract
Neuroligins are cell adhesion proteins that interact with neurexins at the synapse. This interaction may contribute to differentiation, plasticity and specificity of synapses. In humans, single mutations in neuroligin encoding genes lead to autism spectrum disorder and/or mental retardation. Caenorhabditis elegans mutants deficient in nlg-1, an orthologue of human neuroligin genes, have defects in different behaviors. Here we show that the expression of human NLGN1 or rat Nlgn1 cDNAs in C. elegans nlg-1 mutants rescues the fructose osmotic strength avoidance and gentle touch response phenotypes. Two specific point mutations in NLGN3 and NLGN4 genes, involved in autistic spectrum disorder, were further characterized in this experimental system. The R451C allele described in NLGN3, was analyzed with both human NLGN1 (R453C) and worm NLG-1 (R437C) proteins, and both were not functional in rescuing the osmotic avoidance behavior and the gentle touch response phenotype. The D396X allele described in NLGN4, which produces a truncated protein, was studied with human NLGN1 (D432X) and they did not rescue any of the behavioral phenotypes analyzed. In addition, RNAi feeding experiments measuring gentle touch response in wild type strain and worms expressing SID-1 in neurons (which increases the response to dsRNA), both fed with bacteria expressing dsRNA for nlg-1, provided evidence for a postsynaptic in vivo function of neuroligins both in muscle cells and neurons, equivalent to that proposed in mammals. This finding was further confirmed generating transgenic nlg-1 deficient mutants expressing NLG-1 under pan-neuronal (nrx-1) or pan-muscular (myo-3) specific promoters. All these results suggest that the nematode could be used as an in vivo model for studying particular synaptic mechanisms with proteins orthologues of humans involved in pervasive developmental disorders.
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Wahlin KJ, Hackler L, Adler R, Zack DJ. Alternative splicing of neuroligin and its protein distribution in the outer plexiform layer of the chicken retina. J Comp Neurol 2011; 518:4938-62. [PMID: 21031560 DOI: 10.1002/cne.22499] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Although synaptogenesis within the retina is obviously essential for vision, mechanisms responsible for the initiation and maintenance of retinal synapses are poorly understood. In addition to its scientific interest, understanding retinal synapse formation is becoming clinically relevant with ongoing efforts to develop transplantation-based approaches for the treatment of retinal degenerative disease. To extend our understanding, we have focused on the chick model system and have studied the neuroligin family of neuronal adhesion factors that has been shown to participate in synapse assembly in the brain. We identified chicken orthologs of neuroligins 1, -3, and -4, but could find no evidence of neuroligin 2. We investigated temporal and spatial patterns of mRNA and protein expression during development using standard polymerase chain reaction (RT-PCR), quantitative PCR (QPCR), laser-capture microdissection (LCM), and confocal microscopy. At the mRNA level, neuroligins were detected at the earliest period tested, embryonic day (ED)5, which precedes the period of inner retina synaptogenesis. Significant alternative splicing was observed through development. While neuroligin gene products were generally detected in the inner retina, low levels of neuroligin 1 mRNA were also detected in the photoreceptor layer. Neuroligin 3 and -4 transcripts, on the other hand, were only detected in the inner retina. At retinal synapses neuroligin 1 protein was detected in the inner plexiform layer, but its highest levels were detected in the outer plexiform layer on the tips of horizontal cell dendrites. This work lays the groundwork for future studies on the functional roles of the neuroligins within the retina.
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Affiliation(s)
- Karl J Wahlin
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA.
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Dinamarca MC, Weinstein D, Monasterio O, Inestrosa NC. The synaptic protein neuroligin-1 interacts with the amyloid β-peptide. Is there a role in Alzheimer's disease? Biochemistry 2011; 50:8127-37. [PMID: 21838267 DOI: 10.1021/bi201246t] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Amyloid β-peptide (Aβ) is the main component of the amyloid plaques associated with Alzheimer's disease (AD). In the early steps of the disease soluble Aβ oligomers are produced. According to the current "amyloid hypothesis" these oligomers can accumulate over time, leading progressively to the loss of synaptic function and the cognitive failure characteristic of AD. To understand the role of oligomeric Aβ species in AD pathology, it is important to understand the mechanism by which Aβ oligomers are targeted to synaptic junction. We report here the interaction between Aβ with neuroligin-1 (NL-1), a postsynaptic cell-adhesion protein specific for excitatory synapses, which shares a high degree of similarity with acetylcholinesterase, the first synaptic protein described to interact with Aβ. Using intrinsic fluorescence and surface plasmon resonance, we found that Aβ binds to the extracellular domain of NL-1 with a K(d) in the nanomolar range. In the case of NL-2, a postsynaptic cell-adhesion protein specific for inhibitory synapses, just a very weak interaction with Aβ was observed. Aβ polymerization analysis-studied by thioflavin-T assay and electron microscopy-indicated that NL-1 stabilized Aβ aggregates in vitro. Moreover, NL-1 acts as a nucleating factor during the Aβ aggregation process, stimulating the formation of Aβ oligomers. Besides, immunoprecipitation assays confirm that Aβ oligomers interact with NL-1 but not with NL-2. In conclusion, our results show that NL-1 interacts with Aβ increasing the formation of Aβ oligomers, suggesting that this interaction could triggers the targeting of Aβ oligomer to the postsynaptic regions of excitatory synapses.
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Affiliation(s)
- Margarita C Dinamarca
- Centro de Envejecimiento y Regeneración (CARE), Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
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Bottos A, Rissone A, Bussolino F, Arese M. Neurexins and neuroligins: synapses look out of the nervous system. Cell Mol Life Sci 2011; 68:2655-66. [PMID: 21394644 PMCID: PMC11115133 DOI: 10.1007/s00018-011-0664-z] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Revised: 02/16/2011] [Accepted: 02/22/2011] [Indexed: 12/18/2022]
Abstract
The scientific interest in the family of the so-called nervous vascular parallels has been growing steadily for the past 15 years, either by addition of new members to the group or, lately, by deepening the analysis of established concepts and mediators. Proteins governing both neurons and vascular cells are known to be involved in events such as cell fate determination and migration/guidance but not in the last and apparently most complex step of nervous system development, the formation and maturation of synapses. Hence, the recent addition to this family of the specific synaptic proteins, Neurexin and Neuroligin, is a double innovation. The two proteins, which were thought to be "simple" adhesive links between the pre- and post-synaptic sides of chemical synapses, are in fact extremely complex and modulate the most subtle synaptic activities. We will discuss the relevant data and the intriguing challenge of transferring synaptic activities to vascular functions.
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Affiliation(s)
- Alessia Bottos
- Department of Oncological Sciences, University of Torino, IRCC, Institute for Cancer Research and Treatment at Candiolo, Strada prov 142, km 3, 95, 10060 Candiolo (TO), Italy
| | - Alberto Rissone
- Department of Oncological Sciences, University of Torino, IRCC, Institute for Cancer Research and Treatment at Candiolo, Strada prov 142, km 3, 95, 10060 Candiolo (TO), Italy
| | - Federico Bussolino
- Department of Oncological Sciences, University of Torino, IRCC, Institute for Cancer Research and Treatment at Candiolo, Strada prov 142, km 3, 95, 10060 Candiolo (TO), Italy
| | - Marco Arese
- Department of Oncological Sciences, University of Torino, IRCC, Institute for Cancer Research and Treatment at Candiolo, Strada prov 142, km 3, 95, 10060 Candiolo (TO), Italy
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Miller MT, Mileni M, Comoletti D, Stevens RC, Harel M, Taylor P. The crystal structure of the α-neurexin-1 extracellular region reveals a hinge point for mediating synaptic adhesion and function. Structure 2011; 19:767-78. [PMID: 21620717 DOI: 10.1016/j.str.2011.03.011] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Revised: 03/09/2011] [Accepted: 03/13/2011] [Indexed: 10/18/2022]
Abstract
α- and β-neurexins (NRXNs) are transmembrane cell adhesion proteins that localize to presynaptic membranes in neurons and interact with the postsynaptic neuroligins (NLGNs). Their gene mutations are associated with the autism spectrum disorders. The extracellular region of α-NRXNs, containing nine independently folded domains, has structural complexity and unique functional characteristics, distinguishing it from the smaller β-NRXNs. We have solved the X-ray crystal structure of seven contiguous domains of the α-NRXN-1 extracellular region at 3.0 Å resolution. The structure reveals an arrangement where the N-terminal five domains adopt a more rigid linear conformation and the two C-terminal domains form a separate arm connected by a flexible hinge. In an extended conformation the molecule is suitably configured to accommodate a bound NLGN molecule, as supported by structural comparison and surface plasmon resonance. These studies provide the structural basis for a multifunctional synaptic adhesion complex mediated by α-NRXN-1.
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Affiliation(s)
- Meghan T Miller
- Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093, USA.
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Neuroligin 2 is required for synapse development and function at the Drosophila neuromuscular junction. J Neurosci 2011; 31:687-99. [PMID: 21228178 DOI: 10.1523/jneurosci.3854-10.2011] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Neuroligins belong to a highly conserved family of cell adhesion molecules that have been implicated in synapse formation and function. However, the precise in vivo roles of Neuroligins remain unclear. In the present study, we have analyzed the function of Drosophila neuroligin 2 (dnl2) in synaptic development and function. We show that dnl2 is strongly expressed in the embryonic and larval CNS and at the larval neuromuscular junction (NMJ). dnl2 null mutants are viable but display numerous structural defects at the NMJ, including reduced axonal branching and fewer synaptic boutons. dnl2 mutants also show an increase in the number of active zones per bouton but a decrease in the thickness of the subsynaptic reticulum and length of postsynaptic densities. dnl2 mutants also exhibit a decrease in the total glutamate receptor density and a shift in the subunit composition of glutamate receptors in favor of GluRIIA complexes. In addition to the observed defects in synaptic morphology, we also find that dnl2 mutants show increased transmitter release and altered kinetics of stimulus-evoked transmitter release. Importantly, the defects in presynaptic structure, receptor density, and synaptic transmission can be rescued by postsynaptic expression of dnl2. Finally, we show that dnl2 colocalizes and binds to Drosophila neurexin (dnrx) in vivo. However, whereas homozygous mutants for either dnl2 or dnrx are viable, double mutants are lethal and display more severe defects in synaptic morphology. Altogether, our data show that, although dnl2 is not absolutely required for synaptogenesis, it is required postsynaptically for synapse maturation and function.
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Smith RM, Sadee W. Synaptic signaling and aberrant RNA splicing in autism spectrum disorders. Front Synaptic Neurosci 2011; 3:1. [PMID: 21423409 PMCID: PMC3059609 DOI: 10.3389/fnsyn.2011.00001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2010] [Accepted: 01/12/2011] [Indexed: 11/13/2022] Open
Abstract
Interactions between presynaptic and postsynaptic cellular adhesion molecules (CAMs) drive synapse maturation during development. These trans-synaptic interactions are regulated by alternative splicing of CAM RNAs, which ultimately determines neurotransmitter phenotype. The diverse assortment of RNAs produced by alternative splicing generates countless protein isoforms necessary for guiding specialized cell-to-cell connectivity. Failure to generate the appropriate synaptic adhesion proteins is associated with disrupted glutamatergic and gamma-aminobutyric acid signaling, resulting in loss of activity-dependent neuronal plasticity, and risk for developmental disorders, including autism. While the majority of genetic mutations currently linked to autism are rare variants that change the protein-coding sequence of synaptic candidate genes, regulatory polymorphisms affecting constitutive and alternative splicing have emerged as risk factors in numerous other diseases, accounting for an estimated 40–60% of general disease risk. Here, we review the relationship between aberrant RNA splicing of synapse-related genes and autism spectrum disorders.
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Affiliation(s)
- Ryan M Smith
- Program in Pharmacogenomics, Department of Pharmacology, The Ohio State University Columbus, OH, USA
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