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Song SH, Augustine GJ. A role for synapsin tetramerization in synaptic vesicle clustering. J Physiol 2024. [PMID: 38979871 DOI: 10.1113/jp286177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2024] [Accepted: 06/06/2024] [Indexed: 07/10/2024] Open
Abstract
Although synapsins have long been proposed to be key regulators of synaptic vesicle (SV) clustering, their mechanism of action has remained mysterious and somewhat controversial. Here, we review synapsins and their associations with each other and with SVs. We highlight the recent hypothesis that synapsin tetramerization is a mechanism for SV clustering. This hypothesis, which aligns with numerous experimental results, suggests that the larger size of synapsin tetramers, in comparison to dimers, allows tetramers to form optimal bridges between SVs that overcome the repulsive force associated with the negatively charged membrane of SVs and allow synapsins to form a reserve pool of SVs within presynaptic terminals.
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Affiliation(s)
| | - George J Augustine
- Temasek Life sciences Laboratory, Singapore
- Department of Physiology, National University of Singapore, Singapore
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2
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Longfield SF, Gormal RS, Feller M, Parutto P, Reingruber J, Wallis TP, Joensuu M, Augustine GJ, Martínez-Mármol R, Holcman D, Meunier FA. Synapsin 2a tetramerisation selectively controls the presynaptic nanoscale organisation of reserve synaptic vesicles. Nat Commun 2024; 15:2217. [PMID: 38472171 PMCID: PMC10933366 DOI: 10.1038/s41467-024-46256-1] [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: 03/22/2023] [Accepted: 02/21/2024] [Indexed: 03/14/2024] Open
Abstract
Neurotransmitter release relies on the regulated fusion of synaptic vesicles (SVs) that are tightly packed within the presynaptic bouton of neurons. The mechanism by which SVs are clustered at the presynapse, while preserving their ability to dynamically recycle to support neuronal communication, remains unknown. Synapsin 2a (Syn2a) tetramerization has been suggested as a potential clustering mechanism. Here, we used Dual-pulse sub-diffractional Tracking of Internalised Molecules (DsdTIM) to simultaneously track single SVs from the recycling and the reserve pools, in live hippocampal neurons. The reserve pool displays a lower presynaptic mobility compared to the recycling pool and is also present in the axons. Triple knockout of Synapsin 1-3 genes (SynTKO) increased the mobility of reserve pool SVs. Re-expression of wild-type Syn2a (Syn2aWT), but not the tetramerization-deficient mutant K337Q (Syn2aK337Q), fully rescued these effects. Single-particle tracking revealed that Syn2aK337QmEos3.1 exhibited altered activity-dependent presynaptic translocation and nanoclustering. Therefore, Syn2a tetramerization controls its own presynaptic nanoclustering and thereby contributes to the dynamic immobilisation of the SV reserve pool.
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Affiliation(s)
- Shanley F Longfield
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Rachel S Gormal
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Matis Feller
- Group of Data Modelling and Computational Biology, IBENS, Ecole Normale Superieure, 75005, Paris, France
| | - Pierre Parutto
- Group of Data Modelling and Computational Biology, IBENS, Ecole Normale Superieure, 75005, Paris, France
| | - Jürgen Reingruber
- Group of Data Modelling and Computational Biology, IBENS, Ecole Normale Superieure, 75005, Paris, France
| | - Tristan P Wallis
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Merja Joensuu
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, QLD 4072, Australia
| | | | - Ramón Martínez-Mármol
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
| | - David Holcman
- Group of Data Modelling and Computational Biology, IBENS, Ecole Normale Superieure, 75005, Paris, France
- Department of Applied Mathematics and Theoretical Physics (DAMPT) visitor, University of Cambridge, and Churchill College, CB30DS, Cambridge, UK
| | - Frédéric A Meunier
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia.
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD 4072, Australia.
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Song SH, Augustine GJ. Different mechanisms of synapsin-induced vesicle clustering at inhibitory and excitatory synapses. Cell Rep 2023; 42:113004. [PMID: 37597184 DOI: 10.1016/j.celrep.2023.113004] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Revised: 06/26/2023] [Accepted: 08/02/2023] [Indexed: 08/21/2023] Open
Abstract
Synapsins cluster synaptic vesicles (SVs) to provide a reserve pool (RP) of SVs that maintains synaptic transmission during sustained activity. However, it is unclear how synapsins cluster SVs. Here we show that either liquid-liquid phase separation (LLPS) or tetramerization-dependent cross-linking can cluster SVs, depending on whether a synapse is excitatory or inhibitory. Cell-free reconstitution reveals that both mechanisms can cluster SVs, with tetramerization being more effective. At inhibitory synapses, perturbing synapsin-dependent LLPS impairs SV clustering and synchronization of gamma-aminobutyric acid (GABA) release, while preventing synapsin tetramerization does not. At glutamatergic synapses, the opposite is true: synapsin tetramerization enhances clustering of glutamatergic SVs and mobilization of these SVs from the RP, while synapsin LLPS does not. Comparison of inhibitory and excitatory transmission during prolonged synaptic activity reveals that synapsin LLPS serves as a brake to limit GABA release, while synapsin tetramerization enables rapid mobilization of SVs from the RP to sustain glutamate release.
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Affiliation(s)
- Sang-Ho Song
- Neuroscience and Mental Health Program, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore 308232, Singapore
| | - George J Augustine
- Neuroscience and Mental Health Program, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore 308232, Singapore.
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Moschetta M, Ravasenga T, De Fusco A, Maragliano L, Aprile D, Orlando M, Sacchetti S, Casagrande S, Lignani G, Fassio A, Baldelli P, Benfenati F. Ca 2+ binding to synapsin I regulates resting Ca 2+ and recovery from synaptic depression in nerve terminals. Cell Mol Life Sci 2022; 79:600. [PMID: 36409372 PMCID: PMC9678998 DOI: 10.1007/s00018-022-04631-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Revised: 10/23/2022] [Accepted: 11/13/2022] [Indexed: 11/22/2022]
Abstract
Synapsin I (SynI) is a synaptic vesicle (SV)-associated phosphoprotein that modulates neurotransmission by controlling SV trafficking. The SynI C-domain contains a highly conserved ATP binding site mediating SynI oligomerization and SV clustering and an adjacent main Ca2+ binding site, whose physiological role is unexplored. Molecular dynamics simulations revealed that the E373K point mutation irreversibly deletes Ca2+ binding to SynI, still allowing ATP binding, but inducing a destabilization of the SynI oligomerization interface. Here, we analyzed the effects of this mutation on neurotransmitter release and short-term plasticity in excitatory and inhibitory synapses from primary hippocampal neurons. Patch-clamp recordings showed an increase in the frequency of miniature excitatory postsynaptic currents (EPSCs) that was totally occluded by exogenous Ca2+ chelators and associated with a constitutive increase in resting terminal Ca2+ concentrations. Evoked EPSC amplitude was also reduced, due to a decreased readily releasable pool (RRP) size. Moreover, in both excitatory and inhibitory synapses, we observed a marked impaired recovery from synaptic depression, associated with impaired RRP refilling and depletion of the recycling pool of SVs. Our study identifies SynI as a novel Ca2+ buffer in excitatory terminals. Blocking Ca2+ binding to SynI results in higher constitutive Ca2+ levels that increase the probability of spontaneous release and disperse SVs. This causes a decreased size of the RRP and an impaired recovery from depression due to the failure of SV reclustering after sustained high-frequency stimulation. The results indicate a physiological role of Ca2+ binding to SynI in the regulation of SV clustering and trafficking in nerve terminals.
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Affiliation(s)
- Matteo Moschetta
- Center for Synaptic Neuroscience and Technology, Istituto Italiano Di Tecnologia, Largo Rosanna Benzi 10, 16132 Genoa, Italy ,Department of Experimental Medicine, University of Genova, Viale Benedetto XV, 3, 16132 Genoa, Italy
| | - Tiziana Ravasenga
- Center for Synaptic Neuroscience and Technology, Istituto Italiano Di Tecnologia, Largo Rosanna Benzi 10, 16132 Genoa, Italy ,IRCCS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132 Genoa, Italy
| | - Antonio De Fusco
- Center for Synaptic Neuroscience and Technology, Istituto Italiano Di Tecnologia, Largo Rosanna Benzi 10, 16132 Genoa, Italy ,Department of Experimental Medicine, University of Genova, Viale Benedetto XV, 3, 16132 Genoa, Italy
| | - Luca Maragliano
- Center for Synaptic Neuroscience and Technology, Istituto Italiano Di Tecnologia, Largo Rosanna Benzi 10, 16132 Genoa, Italy ,Department of Life and Environmental Sciences, Polytechnic University of Marche, Via Brecce Bianche, 60131 Ancona, Italy
| | - Davide Aprile
- Department of Experimental Medicine, University of Genova, Viale Benedetto XV, 3, 16132 Genoa, Italy ,Present Address: High-Definition Disease Modelling Lab, Campus IFOM-IEO, Milan, Italy
| | - Marta Orlando
- Center for Synaptic Neuroscience and Technology, Istituto Italiano Di Tecnologia, Largo Rosanna Benzi 10, 16132 Genoa, Italy ,Present Address: Charitè Universitätsmedizin Berlin, Freie Universität Berlin and Humboldt-Universität Zu Berlin, Berlin Institute of Health, NeuroCure Cluster of Excellence, Berlin, Germany
| | - Silvio Sacchetti
- Center for Synaptic Neuroscience and Technology, Istituto Italiano Di Tecnologia, Largo Rosanna Benzi 10, 16132 Genoa, Italy
| | - Silvia Casagrande
- Department of Experimental Medicine, University of Genova, Viale Benedetto XV, 3, 16132 Genoa, Italy
| | - Gabriele Lignani
- Center for Synaptic Neuroscience and Technology, Istituto Italiano Di Tecnologia, Largo Rosanna Benzi 10, 16132 Genoa, Italy ,Present Address: Queens Square Institute of Neurology, University College London, London, UK
| | - Anna Fassio
- Department of Experimental Medicine, University of Genova, Viale Benedetto XV, 3, 16132 Genoa, Italy ,IRCCS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132 Genoa, Italy
| | - Pietro Baldelli
- Department of Experimental Medicine, University of Genova, Viale Benedetto XV, 3, 16132 Genoa, Italy ,IRCCS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132 Genoa, Italy
| | - Fabio Benfenati
- Center for Synaptic Neuroscience and Technology, Istituto Italiano Di Tecnologia, Largo Rosanna Benzi 10, 16132 Genoa, Italy ,IRCCS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132 Genoa, Italy
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Longhena F, Faustini G, Brembati V, Pizzi M, Benfenati F, Bellucci A. An updated reappraisal of synapsins: structure, function and role in neurological and psychiatric disorders. Neurosci Biobehav Rev 2021; 130:33-60. [PMID: 34407457 DOI: 10.1016/j.neubiorev.2021.08.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 07/29/2021] [Accepted: 08/09/2021] [Indexed: 01/02/2023]
Abstract
Synapsins (Syns) are phosphoproteins strongly involved in neuronal development and neurotransmitter release. Three distinct genes SYN1, SYN2 and SYN3, with elevated evolutionary conservation, have been described to encode for Synapsin I, Synapsin II and Synapsin III, respectively. Syns display a series of common features, but also exhibit distinctive localization, expression pattern, post-translational modifications (PTM). These characteristics enable their interaction with other synaptic proteins, membranes and cytoskeletal components, which is essential for the proper execution of their multiple functions in neuronal cells. These include the control of synapse formation and growth, neuron maturation and renewal, as well as synaptic vesicle mobilization, docking, fusion, recycling. Perturbations in the balanced expression of Syns, alterations of their PTM, mutations and polymorphisms of their encoding genes induce severe dysregulations in brain networks functions leading to the onset of psychiatric or neurological disorders. This review presents what we have learned since the discovery of Syn I in 1977, providing the state of the art on Syns structure, function, physiology and involvement in central nervous system disorders.
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Affiliation(s)
- Francesca Longhena
- Division of Pharmacology, Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123, Brescia, Italy.
| | - Gaia Faustini
- Division of Pharmacology, Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123, Brescia, Italy.
| | - Viviana Brembati
- Division of Pharmacology, Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123, Brescia, Italy.
| | - Marina Pizzi
- Division of Pharmacology, Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123, Brescia, Italy.
| | - Fabio Benfenati
- Italian Institute of Technology, Via Morego 30, Genova, Italy; IRCSS Policlinico San Martino Hospital, Largo Rosanna Benzi 10, 16132, Genova, Italy.
| | - Arianna Bellucci
- Division of Pharmacology, Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123, Brescia, Italy; Laboratory for Preventive and Personalized Medicine, Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123, Brescia, Italy.
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Synapsin Is Required for Dense Core Vesicle Capture and cAMP-Dependent Neuropeptide Release. J Neurosci 2021; 41:4187-4201. [PMID: 33820857 DOI: 10.1523/jneurosci.2631-20.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 02/11/2021] [Accepted: 03/09/2021] [Indexed: 11/21/2022] Open
Abstract
Release of neuropeptides from dense core vesicles (DCVs) is essential for neuromodulation. Compared with the release of small neurotransmitters, much less is known about the mechanisms and proteins contributing to neuropeptide release. By optogenetics, behavioral analysis, electrophysiology, electron microscopy, and live imaging, we show that synapsin SNN-1 is required for cAMP-dependent neuropeptide release in Caenorhabditis elegans hermaphrodite cholinergic motor neurons. In synapsin mutants, behaviors induced by the photoactivated adenylyl cyclase bPAC, which we previously showed to depend on ACh and neuropeptides (Steuer Costa et al., 2017), are altered as in animals with reduced cAMP. Synapsin mutants have slight alterations in synaptic vesicle (SV) distribution; however, a defect in SV mobilization was apparent after channelrhodopsin-based photostimulation. DCVs were largely affected in snn-1 mutants: DCVs were ∼30% reduced in synaptic terminals, and their contents not released following bPAC stimulation. Imaging axonal DCV trafficking, also in genome-engineered mutants in the serine-9 protein kinase A phosphorylation site, showed that synapsin captures DCVs at synapses, making them available for release. SNN-1 colocalized with immobile, captured DCVs. In synapsin deletion mutants, DCVs were more mobile and less likely to be caught at release sites, and in nonphosphorylatable SNN-1B(S9A) mutants, DCVs traffic less and accumulate, likely by enhanced SNN-1 dependent tethering. Our work establishes synapsin as a key mediator of neuropeptide release.SIGNIFICANCE STATEMENT Little is known about mechanisms that regulate how neuropeptide-containing dense core vesicles (DCVs) traffic along the axon, how neuropeptide release is orchestrated, and where it occurs. We found that one of the longest known synaptic proteins, required for the regulation of synaptic vesicles and their storage in nerve terminals, synapsin, is also essential for neuropeptide release. By electrophysiology, imaging, and electron microscopy in Caenorhabditis elegans, we show that synapsin regulates this process by tethering the DCVs to the cytoskeleton in axonal regions where neuropeptides are to be released. Without synapsin, DCVs cannot be captured at the release sites and, consequently, cannot fuse with the membrane, and neuropeptides are not released. We suggest that synapsin fulfills this role also in vertebrates, including humans.
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Giving names to the actors of synaptic transmission: The long journey from synaptic vesicles to neural plasticity. ADVANCES IN PHARMACOLOGY 2021; 90:19-37. [PMID: 33706933 DOI: 10.1016/bs.apha.2020.09.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
Abstract
More than a scientific paper or a review article, this is a remembrance of a unique time of science and life that the authors spent in Paul Greengard's laboratory at the Rockefeller University in New York in the 1980s and 1990s, forming the so-called synaptic vesicle group. It was a time in which the molecular mechanisms of synaptic transmission and the nature of the organelles in charge of storing and releasing neurotransmitter were just beginning to be understood. It was an exciting time in which the protein composition of synaptic vesicles started to be identified. It turned out that the interactions of synaptic vesicle proteins with the cytoskeleton and the presynaptic membrane and their modulation by protein phosphorylation represented an essential network regulating the efficiency of neurotransmitter release and thereby synaptic strength and plasticity. This is also a description of the distinct scientific journeys that the three authors took on going back to Europe and how they were strongly influenced by the generous and outstanding mentorship of Paul Greengard, his genuine interest in their lives and careers and the life-long friendship with him.
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Patzke C, Brockmann MM, Dai J, Gan KJ, Grauel MK, Fenske P, Liu Y, Acuna C, Rosenmund C, Südhof TC. Neuromodulator Signaling Bidirectionally Controls Vesicle Numbers in Human Synapses. Cell 2020; 179:498-513.e22. [PMID: 31585084 DOI: 10.1016/j.cell.2019.09.011] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 06/28/2019] [Accepted: 09/06/2019] [Indexed: 10/25/2022]
Abstract
Neuromodulators bind to pre- and postsynaptic G protein-coupled receptors (GPCRs), are able to quickly change intracellular cyclic AMP (cAMP) and Ca2+ levels, and are thought to play important roles in neuropsychiatric and neurodegenerative diseases. Here, we discovered in human neurons an unanticipated presynaptic mechanism that acutely changes synaptic ultrastructure and regulates synaptic communication. Activation of neuromodulator receptors bidirectionally controlled synaptic vesicle numbers within nerve terminals. This control correlated with changes in the levels of cAMP-dependent protein kinase A-mediated phosphorylation of synapsin-1. Using a conditional deletion approach, we reveal that the neuromodulator-induced control of synaptic vesicle numbers was largely dependent on synapsin-1. We propose a mechanism whereby non-phosphorylated synapsin-1 "latches" synaptic vesicles to presynaptic clusters at the active zone. cAMP-dependent phosphorylation of synapsin-1 then removes the vesicles. cAMP-independent dephosphorylation of synapsin-1 in turn recruits vesicles. Synapsin-1 thereby bidirectionally regulates synaptic vesicle numbers and modifies presynaptic neurotransmitter release as an effector of neuromodulator signaling in human neurons.
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Affiliation(s)
- Christopher Patzke
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305, USA.
| | - Marisa M Brockmann
- Institut für Neurophysiologie, Charité Universitätsmedizin, 10117 Berlin, Germany
| | - Jinye Dai
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305, USA
| | - Kathlyn J Gan
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305, USA
| | - M Katharina Grauel
- Institut für Neurophysiologie, Charité Universitätsmedizin, 10117 Berlin, Germany
| | - Pascal Fenske
- Institut für Neurophysiologie, Charité Universitätsmedizin, 10117 Berlin, Germany
| | - Yu Liu
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305, USA
| | - Claudio Acuna
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305, USA
| | - Christian Rosenmund
- Institut für Neurophysiologie, Charité Universitätsmedizin, 10117 Berlin, Germany
| | - Thomas C Südhof
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305, USA
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Abstract
Emerging evidence indicates that liquid-liquid phase separation, the formation of a condensed molecular assembly within another diluted aqueous solution, is a means for cells to organize highly condensed biological assemblies (also known as biological condensates or membraneless compartments) with very broad functions and regulatory properties in different subcellular regions. Molecular machineries dictating synaptic transmissions in both presynaptic boutons and postsynaptic densities of neuronal synapses may be such biological condensates. Here we review recent developments showing how phase separation can build dense synaptic molecular clusters, highlight unique features of such condensed clusters in the context of synaptic development and signaling, discuss how aberrant phase-separation-mediated synaptic assembly formation may contribute to dysfunctional signaling in psychiatric disorders, and present some challenges and opportunities of phase separation in synaptic biology.
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Rocchi A, Sacchetti S, De Fusco A, Giovedi S, Parisi B, Cesca F, Höltje M, Ruprecht K, Ahnert-Hilger G, Benfenati F. Autoantibodies to synapsin I sequestrate synapsin I and alter synaptic function. Cell Death Dis 2019; 10:864. [PMID: 31727880 PMCID: PMC6856194 DOI: 10.1038/s41419-019-2106-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 10/25/2019] [Accepted: 10/31/2019] [Indexed: 12/18/2022]
Abstract
Synapsin I is a phosphoprotein that coats the cytoplasmic side of synaptic vesicles and regulates their trafficking within nerve terminals. Autoantibodies against Syn I have been described in sera and cerebrospinal fluids of patients with numerous neurological diseases, including limbic encephalitis and clinically isolated syndrome; however, the effects and fate of autoantibodies in neurons are still unexplored. We found that in vitro exposure of primary hippocampal neurons to patient's autoantibodies to SynI decreased the density of excitatory and inhibitory synapses and impaired both glutamatergic and GABAergic synaptic transmission. These effects were reproduced with a purified SynI antibody and completely absent in SynI knockout neurons. Autoantibodies to SynI are internalized by FcγII/III-mediated endocytosis, interact with endogenous SynI, and promote its sequestration and intracellular aggregation. Neurons exposed to human autoantibodies to SynI display a reduced density of SVs, mimicking the SynI loss-of-function phenotype. Our data indicate that autoantibodies to intracellular antigens such as SynI can reach and inactivate their targets and suggest that an antibody-mediated synaptic dysfunction may contribute to the evolution and progression of autoimmune-mediated neurological diseases positive for SynI autoantibodies.
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Affiliation(s)
- Anna Rocchi
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Largo Rosanna Benzi 10, 16132, Genova, Italy
- IRCSS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132, Genova, Italy
| | - Silvio Sacchetti
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Largo Rosanna Benzi 10, 16132, Genova, Italy
| | - Antonio De Fusco
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Largo Rosanna Benzi 10, 16132, Genova, Italy
- Department of Experimental Medicine, University of Genova, Viale Benedetto XV, 3, 16132, Genova, Italy
| | - Silvia Giovedi
- IRCSS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132, Genova, Italy
- Department of Experimental Medicine, University of Genova, Viale Benedetto XV, 3, 16132, Genova, Italy
| | - Barbara Parisi
- IRCSS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132, Genova, Italy
- Department of Experimental Medicine, University of Genova, Viale Benedetto XV, 3, 16132, Genova, Italy
| | - Fabrizia Cesca
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Largo Rosanna Benzi 10, 16132, Genova, Italy
- Department of Life Science, University of Trieste, via Giorgieri, 5, 34127, Trieste, Italy
| | - Markus Höltje
- Institute of Integrative Neuroanatomy, Charité - Universitätsmedizin Berlin, Corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Klemens Ruprecht
- Department of Neurology, Charité - Universitätsmedizin Berlin, Corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Gudrun Ahnert-Hilger
- Institute of Integrative Neuroanatomy, Charité - Universitätsmedizin Berlin, Corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Fabio Benfenati
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Largo Rosanna Benzi 10, 16132, Genova, Italy.
- IRCSS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132, Genova, Italy.
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Vaden JH, Banumurthy G, Gusarevich ES, Overstreet-Wadiche L, Wadiche JI. The readily-releasable pool dynamically regulates multivesicular release. eLife 2019; 8:47434. [PMID: 31364987 PMCID: PMC6716946 DOI: 10.7554/elife.47434] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Accepted: 07/30/2019] [Indexed: 01/04/2023] Open
Abstract
The number of neurotransmitter-filled vesicles released into the synaptic cleft with each action potential dictates the reliability of synaptic transmission. Variability of this fundamental property provides diversity of synaptic function across brain regions, but the source of this variability is unclear. The prevailing view is that release of a single (univesicular release, UVR) or multiple vesicles (multivesicular release, MVR) reflects variability in vesicle release probability, a notion that is well-supported by the calcium-dependence of release mode. However, using mouse brain slices, we now demonstrate that the number of vesicles released is regulated by the size of the readily-releasable pool, upstream of vesicle release probability. Our results point to a model wherein protein kinase A and its vesicle-associated target, synapsin, dynamically control release site occupancy to dictate the number of vesicles released without altering release probability. Together these findings define molecular mechanisms that control MVR and functional diversity of synaptic signaling. Our nervous system allows us to rapidly sense and respond to the world around us via cells called neurons that relay electrical signals around the brain and body. When an electrical impulse travelling along one neuron reaches a junction – called a synapse – with a neighboring neuron, it stimulates small containers known as vesicles from the first cell to release their contents into the synapse. These contents then travel across to the neighboring cell and may generate a new electrical impulse. The number of vesicles at a synapse that are ready to be released varies from one to ten. The more vesicles the neuron releases, the more likely the second cell will produce an electrical signal of its own. However, not all electrical signals reaching a synapse stimulate vesicles to be released and some signals only release a single vesicle. What determines how many vesicles are released by a single electrical signal? Some vesicles have a higher likelihood of being released than others, but this “eagerness” does not always predict how many vesicles an individual synapse will actually discharge. Now, Vaden et al. have used brain tissue from mice to test an alternative possibility: the simple idea that the number of vesicles available at the synapse affects how many vesicles are released without altering their eagerness for release. Vaden et al. found that activating an enzyme called protein kinase A increased the number of vesicles released from synapses without changing how likely individual vesicles were to be released. Inhibiting protein kinase A also did not change individual vesicle’s eagerness to be released, but did decrease the number of vesicles that were discharged. Further experiments found that protein kinase A modifies a molecule on the surface of vesicles, known as synapsin, which controls the number of vesicles that are available for release. These findings show that the number of vesicles released at a synapse is controlled by two independently regulated parameters: the number of vesicles that are available, as well as how eager individual vesicles are to be released. The ability of neurons to communicate with each other is disrupted in autism spectrum disorders, Alzheimer’s disease and many other diseases. Learning how neurons communicate in healthy brains will help us understand what happens in the neurons of individuals with these conditions.
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Affiliation(s)
- Jada H Vaden
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, United States
| | | | - Eugeny S Gusarevich
- Department of Fundamental and Applied Physics, Northern (Arctic) Federal University named after M.V. Lomonosov, Arkhangelsk, Russian Federation
| | | | - Jacques I Wadiche
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, United States
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12
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Marte A, Russo I, Rebosio C, Valente P, Belluzzi E, Pischedda F, Montani C, Lavarello C, Petretto A, Fedele E, Baldelli P, Benfenati F, Piccoli G, Greggio E, Onofri F. Leucine‐rich repeat kinase 2 phosphorylation on synapsin I regulates glutamate release at pre‐synaptic sites. J Neurochem 2019; 150:264-281. [PMID: 31148170 DOI: 10.1111/jnc.14778] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Revised: 05/20/2019] [Accepted: 05/28/2019] [Indexed: 12/25/2022]
Abstract
Leucine-rich repeat kinase 2 (LRRK2) is a large multidomain scaffolding protein with kinase and GTPase activities involved in synaptic vesicle (SV) dynamics. While its role in Parkinson's disease has been largely investigated, little is known about LRRK2 physiological role and until now few proteins have been described as substrates. We have previously demonstrated that LRRK2 through its WD40 domain interacts with synapsin I, an important SV-associated phosphoprotein involved in neuronal development and in the regulation of neurotransmitter release. To test whether synapsin I is substrate for LRRK2 and characterize the properties of its phosphorylation, we used in vitro kinase and binding assays as well as cellular model and site-direct mutagenesis. Using synaptosomes in superfusion, patch-clamp recordings in autaptic WT and synapsin I KO cortical neurons and SypHy assay on primary cortical culture from wild-type and BAC human LRRK2 G2019S mice we characterized the role of LRRK2 kinase activity on glutamate release and SV trafficking. Here we reported that synapsin I is phosphorylated by LRRK2 and demonstrated that the interaction between LRRK2 WD40 domain and synapsin I is crucial for this phosphorylation. Moreover, we showed that LRRK2 phosphorylation of synapsin I at threonine 337 and 339 significantly reduces synapsin I-SV/actin interactions. Using complementary experimental approaches, we demonstrated that LRRK2 controls glutamate release and SV dynamics in a kinase activity and synapsin I-dependent manner. Our findings show that synapsin I is a LRRK2 substrate and describe a novel mechanisms of regulation of glutamate release by LRRK2 kinase activity.
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Affiliation(s)
- Antonella Marte
- Department of Experimental Medicine University of Genova Genova Italy
| | | | | | - Pierluigi Valente
- Department of Experimental Medicine University of Genova Genova Italy
- IRCCS Ospedale Policlinico San Martino Genova Italy
| | - Elisa Belluzzi
- Rheumatology Unit, Department of Medicine‐DIMED University Hospital of Padova Padova Italy
| | - Francesca Pischedda
- Center for Integrative Biology (CIBIO) University of Trento Trento Italy
- Dulbecco Telethon Institute Trento Italy
| | - Caterina Montani
- Center for Integrative Biology (CIBIO) University of Trento Trento Italy
- Dulbecco Telethon Institute Trento Italy
| | - Chiara Lavarello
- Laboratory of Mass Spectrometry ‐ Core Facilities Istituto Giannina Gaslini Genova Italy
| | - Andrea Petretto
- Laboratory of Mass Spectrometry ‐ Core Facilities Istituto Giannina Gaslini Genova Italy
| | - Ernesto Fedele
- Department of Pharmacy University of Genova Genova Italy
- IRCCS Ospedale Policlinico San Martino Genova Italy
| | - Pietro Baldelli
- Department of Experimental Medicine University of Genova Genova Italy
- IRCCS Ospedale Policlinico San Martino Genova Italy
| | - Fabio Benfenati
- IRCCS Ospedale Policlinico San Martino Genova Italy
- Center for Synaptic Neuroscience and Technology Istituto Italiano di Tecnologia Genova Italy
| | - Giovanni Piccoli
- Center for Integrative Biology (CIBIO) University of Trento Trento Italy
- Dulbecco Telethon Institute Trento Italy
| | - Elisa Greggio
- Department of Biology University of Padova Padova Italy
| | - Franco Onofri
- Department of Experimental Medicine University of Genova Genova Italy
- IRCCS Ospedale Policlinico San Martino Genova Italy
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13
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Yu XB, Uhde M, Green PH, Alaedini A. Autoantibodies in the Extraintestinal Manifestations of Celiac Disease. Nutrients 2018; 10:E1123. [PMID: 30127251 PMCID: PMC6115844 DOI: 10.3390/nu10081123] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 08/15/2018] [Accepted: 08/17/2018] [Indexed: 02/07/2023] Open
Abstract
Increased antibody reactivity towards self-antigens is often indicative of a disruption of homeostatic immune pathways in the body. In celiac disease, an autoimmune enteropathy triggered by the ingestion of gluten from wheat and related cereals in genetically predisposed individuals, autoantibody reactivity to transglutaminase 2 is reflective of the pathogenic role of the enzyme in driving the associated inflammatory immune response. Autoantibody reactivity to transglutaminase 2 closely corresponds with the gluten intake and clinical presentation in affected patients, serving as a highly useful biomarker in the diagnosis of celiac disease. In addition to gastrointestinal symptoms, celiac disease is associated with a number of extraintestinal manifestations, including those affecting skin, bones, and the nervous system. Investigations of these manifestations in celiac disease have identified a number of associated immune abnormalities, including B cell reactivity towards various autoantigens, such as transglutaminase 3, transglutaminase 6, synapsin I, gangliosides, and collagen. Clinical relevance, pathogenic potential, mechanism of development, and diagnostic and prognostic value of the various identified autoantibody reactivities continue to be subjects of investigation and will be reviewed here.
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Affiliation(s)
- Xuechen B Yu
- Department of Medicine, Columbia University Medical Center, 1130 Saint Nicholas Ave., New York, NY 10032, USA.
- Celiac Disease Center, Columbia University, New York, NY 10032, USA.
- Institute of Human Nutrition, Columbia University, New York, NY 10032, USA.
| | - Melanie Uhde
- Department of Medicine, Columbia University Medical Center, 1130 Saint Nicholas Ave., New York, NY 10032, USA.
- Celiac Disease Center, Columbia University, New York, NY 10032, USA.
| | - Peter H Green
- Department of Medicine, Columbia University Medical Center, 1130 Saint Nicholas Ave., New York, NY 10032, USA.
- Celiac Disease Center, Columbia University, New York, NY 10032, USA.
| | - Armin Alaedini
- Department of Medicine, Columbia University Medical Center, 1130 Saint Nicholas Ave., New York, NY 10032, USA.
- Celiac Disease Center, Columbia University, New York, NY 10032, USA.
- Institute of Human Nutrition, Columbia University, New York, NY 10032, USA.
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14
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Glycans and glycosaminoglycans in neurobiology: key regulators of neuronal cell function and fate. Biochem J 2018; 475:2511-2545. [PMID: 30115748 DOI: 10.1042/bcj20180283] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Revised: 07/14/2018] [Accepted: 07/18/2018] [Indexed: 12/16/2022]
Abstract
The aim of the present study was to examine the roles of l-fucose and the glycosaminoglycans (GAGs) keratan sulfate (KS) and chondroitin sulfate/dermatan sulfate (CS/DS) with selected functional molecules in neural tissues. Cell surface glycans and GAGs have evolved over millions of years to become cellular mediators which regulate fundamental aspects of cellular survival. The glycocalyx, which surrounds all cells, actuates responses to growth factors, cytokines and morphogens at the cellular boundary, silencing or activating downstream signaling pathways and gene expression. In this review, we have focused on interactions mediated by l-fucose, KS and CS/DS in the central and peripheral nervous systems. Fucose makes critical contributions in the area of molecular recognition and information transfer in the blood group substances, cytotoxic immunoglobulins, cell fate-mediated Notch-1 interactions, regulation of selectin-mediated neutrophil extravasation in innate immunity and CD-34-mediated new blood vessel development, and the targeting of neuroprogenitor cells to damaged neural tissue. Fucosylated glycoproteins regulate delivery of synaptic neurotransmitters and neural function. Neural KS proteoglycans (PGs) were examined in terms of cellular regulation and their interactive properties with neuroregulatory molecules. The paradoxical properties of CS/DS isomers decorating matrix and transmembrane PGs and the positive and negative regulatory cues they provide to neurons are also discussed.
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15
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Large-scale computational drug repositioning to find treatments for rare diseases. NPJ Syst Biol Appl 2018; 4:13. [PMID: 29560273 PMCID: PMC5847522 DOI: 10.1038/s41540-018-0050-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 01/22/2018] [Accepted: 02/03/2018] [Indexed: 11/08/2022] Open
Abstract
Rare, or orphan, diseases are conditions afflicting a small subset of people in a population. Although these disorders collectively pose significant health care problems, drug companies require government incentives to develop drugs for rare diseases due to extremely limited individual markets. Computer-aided drug repositioning, i.e., finding new indications for existing drugs, is a cheaper and faster alternative to traditional drug discovery offering a promising venue for orphan drug research. Structure-based matching of drug-binding pockets is among the most promising computational techniques to inform drug repositioning. In order to find new targets for known drugs ultimately leading to drug repositioning, we recently developed eMatchSite, a new computer program to compare drug-binding sites. In this study, eMatchSite is combined with virtual screening to systematically explore opportunities to reposition known drugs to proteins associated with rare diseases. The effectiveness of this integrated approach is demonstrated for a kinase inhibitor, which is a confirmed candidate for repositioning to synapsin Ia. The resulting dataset comprises 31,142 putative drug-target complexes linked to 980 orphan diseases. The modeling accuracy is evaluated against the structural data recently released for tyrosine-protein kinase HCK. To illustrate how potential therapeutics for rare diseases can be identified, we discuss a possibility to repurpose a steroidal aromatase inhibitor to treat Niemann-Pick disease type C. Overall, the exhaustive exploration of the drug repositioning space exposes new opportunities to combat orphan diseases with existing drugs. DrugBank/Orphanet repositioning data are freely available to research community at https://osf.io/qdjup/.
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16
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Liu A, Zhang Y, Han L, He G, Xie W, Zhou Z, Jia Z. Regulation of Neurotransmitter Release by Amyloid Precursor Protein Through Synapsin Phosphorylation. Neurochem Res 2017; 44:683-691. [PMID: 29052089 DOI: 10.1007/s11064-017-2418-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Revised: 10/01/2017] [Accepted: 10/09/2017] [Indexed: 12/19/2022]
Abstract
Abnormal processing of amyloid precursor protein (APP) and aggregation of the Aβ peptide are known to play a key role in the pathogenesis of Alzheimer disease, but the function of endogenous APP under normal physiological conditions remains poorly understood. In this study, we investigated presynaptic changes in APP knockout (KO) mice. We demonstrate that both sucrose-induced neurotransmission and synaptic depletion in response to high frequency stimulation are significantly enhanced in APP KO compared to wild type littermates. In addition, the level of phosphorylated forms of synapsins, but not total synapsins, is elevated in the KO mice. Furthermore, we show that the inhibition of L-type calcium channels normalizes phosphorylated synapsins and slows down the high frequency induced synaptic depletion in APP KO mice. These results suggest a new mechanism by which APP regulates synaptic vesicle dynamics through synapsin-dependent phosphorylation.
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Affiliation(s)
- An Liu
- Institute of Life Sciences, The Key Laboratory of Developmental Genes and Human Disease, Jiangsu Co-innovation Center of Neuroregeneration, Southeast University, Nanjing, 210096, China
| | - Ying Zhang
- Institute of Life Sciences, The Key Laboratory of Developmental Genes and Human Disease, Jiangsu Co-innovation Center of Neuroregeneration, Southeast University, Nanjing, 210096, China
| | - Lifang Han
- Institute of Life Sciences, The Key Laboratory of Developmental Genes and Human Disease, Jiangsu Co-innovation Center of Neuroregeneration, Southeast University, Nanjing, 210096, China
| | - Guiqin He
- Institute of Life Sciences, The Key Laboratory of Developmental Genes and Human Disease, Jiangsu Co-innovation Center of Neuroregeneration, Southeast University, Nanjing, 210096, China
| | - Wei Xie
- Institute of Life Sciences, The Key Laboratory of Developmental Genes and Human Disease, Jiangsu Co-innovation Center of Neuroregeneration, Southeast University, Nanjing, 210096, China
| | - Zikai Zhou
- Institute of Life Sciences, The Key Laboratory of Developmental Genes and Human Disease, Jiangsu Co-innovation Center of Neuroregeneration, Southeast University, Nanjing, 210096, China
| | - Zhengping Jia
- Neurosciences & Mental Health, the Hospital for Sick Children, 555 University Ave., Toronto, ON, M5G 1X8, Canada. .,Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada.
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17
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Milovanovic D, De Camilli P. Synaptic Vesicle Clusters at Synapses: A Distinct Liquid Phase? Neuron 2017; 93:995-1002. [PMID: 28279363 DOI: 10.1016/j.neuron.2017.02.013] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 02/06/2017] [Accepted: 02/06/2017] [Indexed: 11/17/2022]
Abstract
Phase separation in the cytoplasm is emerging as a major principle in intracellular organization. In this process, sets of macromolecules assemble themselves into liquid compartments that are distinct from the surrounding medium but are not delimited by membrane boundaries. Here, we discuss how phase separation, in which a component of one of the two phases is vesicles rather than macromolecules, could underlie the formation of synaptic vesicle (SV) clusters in proximity to presynaptic sites. The organization of SVs into a liquid phase could explain how SVs remain tightly clustered without being stably bound to a scaffold so that they can be efficiently recruited to release site by active zone components.
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Affiliation(s)
- Dragomir Milovanovic
- Departments of Neuroscience and Cell Biology, Program in Cellular Neuroscience, Neurodegeneration and Repair, Kavli Institute for Neuroscience, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Pietro De Camilli
- Departments of Neuroscience and Cell Biology, Program in Cellular Neuroscience, Neurodegeneration and Repair, Kavli Institute for Neuroscience, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06520, USA.
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18
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Wang YH, Chang SH, Mau-Hsu D, Wang JH, Young TH. Poly(N-(4-aminobutyl)-acrylamide) as mimetic polylysine for improving survival and differentiation of cerebellar granule neurons. J Biomed Mater Res B Appl Biomater 2017; 106:1194-1201. [PMID: 28561950 DOI: 10.1002/jbm.b.33932] [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: 12/22/2016] [Revised: 04/11/2017] [Accepted: 05/12/2017] [Indexed: 11/06/2022]
Abstract
Poly(N-(4-aminobutyl)-acrylamide) (P4Am) and poly-d-lysine (PDL) possess the same butylamine side chain. The main difference is the peptide structure, which is in the main chain of PDL but in the side chain of P4Am. PDL has been extensively used in the preparation of neuronal cultures. We assumed neurons are sensitive enough to distinguish such structure difference so these two cationic polymers were compared at serial coating concentrations for culturing cerebellar granule neurons from 7-day-old Wistar rats in this study. Cellular viability and morphology assay showed no obvious difference for neurons cultured at high coating concentrations (>0.31 µg/mL) of these two polymers. In contrast, the difference in the peptide structure between P4Am and PDL could be distinguished by neurons at low coating concentrations (< 0.16 µg/mL). P4Am at low coating concentration could keep aggregates with three or four thick processes to support a more complete neural network with higher cellular viability than PDL. This suggests the interaction between neurons and the specific peptide structure of P4Am at low coating concentration was able to improve survival and differentiation of cultured cerebellar granule neurons. Although neural cells exhibited different morphologies and activities on high and low P4Am coating concentrations, immunofluorescence imaging confirmed most of cultured cells were functionally mature neurons, stained by neurofilament, synapsin I, and GAP43. The information should be useful for designing new biomaterials for regeneration of damaged circuits following disease or trauma. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1194-1201, 2018.
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Affiliation(s)
- Yu-Hsin Wang
- Institute of Biomedical Engineering, College of Medicine and College of Engineering, National Taiwan University, Taipei, Taiwan
| | - Shao-Hsuan Chang
- Institute of Biomedical Engineering, College of Medicine and College of Engineering, National Taiwan University, Taipei, Taiwan
| | - Daxen Mau-Hsu
- Institute of Biomedical Engineering, College of Medicine and College of Engineering, National Taiwan University, Taipei, Taiwan
| | - Jyh-Horng Wang
- Department of Orthopedic Surgery, National Taiwan University Hospital, Taipei, Taiwan
| | - Tai-Horng Young
- Institute of Biomedical Engineering, College of Medicine and College of Engineering, National Taiwan University, Taipei, Taiwan
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19
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Minges A, Ciupka D, Winkler C, Höppner A, Gohlke H, Groth G. Structural intermediates and directionality of the swiveling motion of Pyruvate Phosphate Dikinase. Sci Rep 2017; 7:45389. [PMID: 28358005 PMCID: PMC5371819 DOI: 10.1038/srep45389] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Accepted: 02/23/2017] [Indexed: 12/13/2022] Open
Abstract
Pyruvate phosphate dikinase (PPDK) is a vital enzyme in cellular energy metabolism catalyzing the ATP- and Pi-dependent formation of phosphoenolpyruvate from pyruvate in C4 -plants, but the reverse reaction forming ATP in bacteria and protozoa. The multi-domain enzyme is considered an efficient molecular machine that performs one of the largest single domain movements in proteins. However, a comprehensive understanding of the proposed swiveling domain motion has been limited by not knowing structural intermediates or molecular dynamics of the catalytic process. Here, we present crystal structures of PPDKs from Flaveria, a model genus for studying the evolution of C4 -enzymes from phylogenetic ancestors. These structures resolve yet unknown conformational intermediates and provide the first detailed view on the large conformational transitions of the protein in the catalytic cycle. Independently performed unrestrained MD simulations and configurational free energy calculations also identified these intermediates. In all, our experimental and computational data reveal strict coupling of the CD swiveling motion to the conformational state of the NBD. Moreover, structural asymmetries and nucleotide binding states in the PPDK dimer support an alternate binding change mechanism for this intriguing bioenergetic enzyme.
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Affiliation(s)
- Alexander Minges
- Cluster of Excellence on Plant Sciences (CEPLAS), Institute of Biochemical Plant Physiology, Heinrich Heine University Düsseldorf, 40204 Düsseldorf, Germany
| | - Daniel Ciupka
- Institute of Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, 40204 Düsseldorf, Germany
| | - Christian Winkler
- Cluster of Excellence on Plant Sciences (CEPLAS), Institute of Biochemical Plant Physiology, Heinrich Heine University Düsseldorf, 40204 Düsseldorf, Germany
| | - Astrid Höppner
- Cluster of Excellence on Plant Sciences (CEPLAS), Institute of Biochemical Plant Physiology, Heinrich Heine University Düsseldorf, 40204 Düsseldorf, Germany
| | - Holger Gohlke
- Institute of Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, 40204 Düsseldorf, Germany
| | - Georg Groth
- Cluster of Excellence on Plant Sciences (CEPLAS), Institute of Biochemical Plant Physiology, Heinrich Heine University Düsseldorf, 40204 Düsseldorf, Germany
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20
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Cheng Q, Song SH, Augustine GJ. Calcium-Dependent and Synapsin-Dependent Pathways for the Presynaptic Actions of BDNF. Front Cell Neurosci 2017; 11:75. [PMID: 28392759 PMCID: PMC5364187 DOI: 10.3389/fncel.2017.00075] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Accepted: 03/02/2017] [Indexed: 11/19/2022] Open
Abstract
We used cultured hippocampal neurons to determine the signaling pathways mediating brain-derived neurotrophic factor (BDNF) regulation of spontaneous glutamate and GABA release. BDNF treatment elevated calcium concentration in presynaptic terminals; this calcium signal reached a peak within 1 min and declined in the sustained presence of BDNF. This BDNF-induced transient rise in presynaptic calcium was reduced by SKF96365, indicating that BDNF causes presynaptic calcium influx via TRPC channels. BDNF treatment increased the frequency of miniature excitatory postsynaptic currents (mEPSCs). This response consisted of two components: a transient component that peaked within 1 min of initiating BDNF application and a second component that was sustained, at a lower mEPSC frequency, for the duration of BDNF application. The initial transient component was greatly reduced by removing external calcium or by treatment with SKF96365, as well as by Pyr3, a selective blocker of TRPC3 channels. In contrast, the sustained component was unaffected in these conditions but was eliminated by U0126, an inhibitor of the MAP kinase (MAPK) pathway, as well as by genetic deletion of synapsins in neurons from a synapsin triple knock-out (TKO) mouse. Thus, two pathways mediate the ability of BDNF to enhance spontaneous glutamate release: the transient component arises from calcium influx through TRPC3 channels, while the sustained component is mediated by MAPK phosphorylation of synapsins. We also examined the ability of these two BDNF-dependent pathways to regulate spontaneous release of the inhibitory neurotransmitter, GABA. BDNF had no effect on the frequency of spontaneous miniature inhibitory postsynaptic currents (mIPSCs) in neurons from wild-type (WT) mice, but surprisingly did increase mIPSC frequency in synapsin TKO mice. This covert BDNF response was blocked by removal of external calcium or by treatment with SKF96365 or Pyr3, indicating that it results from calcium influx mediated by TRPC3 channels. Thus, the BDNF-activated calcium signaling pathway can also enhance spontaneous GABA release, though this effect is suppressed by synapsins under normal physiological conditions.
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Affiliation(s)
- Qing Cheng
- Department of Neurobiology, Duke University Medical Center Durham, NC, USA
| | - Sang-Ho Song
- Center for Functional Connectomics, Korea Institute of Science and TechnologySeoul, South Korea; Lee Kong Chian School of Medicine, Nanyang Technological UniversitySingapore, Singapore; Institute of Molecular and Cell BiologySingapore, Singapore
| | - George J Augustine
- Center for Functional Connectomics, Korea Institute of Science and TechnologySeoul, South Korea; Lee Kong Chian School of Medicine, Nanyang Technological UniversitySingapore, Singapore; Institute of Molecular and Cell BiologySingapore, Singapore
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21
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Song SH, Augustine GJ. Synapsin Isoforms and Synaptic Vesicle Trafficking. Mol Cells 2015; 38:936-40. [PMID: 26627875 PMCID: PMC4673407 DOI: 10.14348/molcells.2015.0233] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 11/09/2015] [Accepted: 11/10/2015] [Indexed: 11/27/2022] Open
Abstract
Synapsins were the first presynaptic proteins identified and have served as the flagship of the presynaptic protein field. Here we review recent studies demonstrating that different members of the synapsin family play different roles at presynaptic terminals employing different types of synaptic vesicles. The structural underpinnings for these functions are just beginning to be understood and should provide a focus for future efforts.
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Affiliation(s)
- Sang-Ho Song
- Lee Kong Chian School of Medicine,
Singapore 637553,
Singapore
- Institute of Molecular and Cell Biology,
Singapore 138673,
Singapore
| | - George J. Augustine
- Lee Kong Chian School of Medicine,
Singapore 637553,
Singapore
- Institute of Molecular and Cell Biology,
Singapore 138673,
Singapore
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22
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ATP binding to synaspsin IIa regulates usage and clustering of vesicles in terminals of hippocampal neurons. J Neurosci 2015; 35:985-98. [PMID: 25609616 DOI: 10.1523/jneurosci.0944-14.2015] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Synaptic transmission is expensive in terms of its energy demands and was recently shown to decrease the ATP concentration within presynaptic terminals transiently, an observation that we confirm. We hypothesized that, in addition to being an energy source, ATP may modulate the synapsins directly. Synapsins are abundant neuronal proteins that associate with the surface of synaptic vesicles and possess a well defined ATP-binding site of undetermined function. To examine our hypothesis, we produced a mutation (K270Q) in synapsin IIa that prevents ATP binding and reintroduced the mutant into cultured mouse hippocampal neurons devoid of all synapsins. Remarkably, staining for synaptic vesicle markers was enhanced in these neurons compared with neurons expressing wild-type synapsin IIa, suggesting overly efficient clustering of vesicles. In contrast, the mutation completely disrupted the capability of synapsin IIa to slow synaptic depression during sustained 10 Hz stimulation, indicating that it interfered with synapsin-dependent vesicle recruitment. Finally, we found that the K270Q mutation attenuated the phosphorylation of synapsin IIa on a distant PKA/CaMKI consensus site known to be essential for vesicle recruitment. We conclude that ATP binding to synapsin IIa plays a key role in modulating its function and in defining its contribution to hippocampal short-term synaptic plasticity.
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23
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Functional role of ATP binding to synapsin I in synaptic vesicle trafficking and release dynamics. J Neurosci 2015; 34:14752-68. [PMID: 25355227 DOI: 10.1523/jneurosci.1093-14.2014] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Synapsins (Syns) are synaptic vesicle (SV)-associated proteins involved in the regulation of synaptic transmission and plasticity, which display a highly conserved ATP binding site in the central C-domain, whose functional role is unknown. Using molecular dynamics simulations, we demonstrated that ATP binding to SynI is mediated by a conformational transition of a flexible loop that opens to make the binding site accessible; such transition, prevented in the K269Q mutant, is not significantly affected in the absence of Ca(2+) or by the E373K mutation that abolishes Ca(2+)-binding. Indeed, the ATP binding to SynI also occurred under Ca(2+)-free conditions and increased its association with purified rat SVs regardless of the presence of Ca(2+) and promoted SynI oligomerization. However, although under Ca(2+)-free conditions, SynI dimerization and SV clustering were enhanced, Ca(2+) favored the formation of tetramers at the expense of dimers and did not affect SV clustering, indicating a role of Ca(2+)-dependent dimer/tetramer transitions in the regulation of ATP-dependent SV clustering. To elucidate the role of ATP/SynI binding in synaptic physiology, mouse SynI knock-out hippocampal neurons were transduced with either wild-type or K269Q mutant SynI and inhibitory transmission was studied by patch-clamp and electron microscopy. K269Q-SynI expressing inhibitory synapses showed increased synaptic strength due to an increase in the release probability, an increased vulnerability to synaptic depression and a dysregulation of SV trafficking, when compared with wild-type SynI-expressing terminals. The results suggest that the ATP-SynI binding plays predocking and postdocking roles in the modulation of SV clustering and plasticity of inhibitory synapses.
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Ingle BL, Cundari TR. Impact of divalent metal cations on the catalysis of peptide bonds: a DFT study. J COORD CHEM 2014. [DOI: 10.1080/00958972.2014.964223] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Brandall L. Ingle
- Center for Advanced Scientific Computing and Modeling (CASCaM), Department of Chemistry, University of North Texas, Denton, TX, USA
| | - Thomas R. Cundari
- Center for Advanced Scientific Computing and Modeling (CASCaM), Department of Chemistry, University of North Texas, Denton, TX, USA
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Abstract
Synaptic vesicles release their vesicular contents to the extracellular space by Ca(2+)-triggered exocytosis. The Ca(2+)-triggered exocytotic process is regulated by synaptotagmin (Syt), a vesicular Ca(2+)-binding C2 domain protein. Synaptotagmin 1 (Syt1), the most studied major isoform among 16 Syt isoforms, mediates Ca(2+)-triggered synaptic vesicle exocytosis by interacting with the target membranes and SNARE/complexin complex. In synapses of the central nervous system, synaptobrevin 2, a major vesicular SNARE protein, forms a ternary SNARE complex with the plasma membrane SNARE proteins, syntaxin 1 and SNAP25. The affinities of Ca(2+)-dependent interactions between Syt1 and its targets (i.e., SNARE complexes and membranes) are well correlated with the efficacies of the corresponding exocytotic processes. Therefore, different SNARE protein isoforms and membrane lipids, which interact with Syt1 with various affinities, are capable of regulating the efficacy of Syt1-mediated exocytosis. Otoferlin, another type of vesicular C2 domain protein that binds to the membrane in a Ca(2+)-dependent manner, is also involved in the Ca(2+)-triggered synaptic vesicle exocytosis in auditory hair cells. However, the functions of otoferlin in the exocytotic process are not well understood. In addition, at least five different types of synaptic vesicle proteins such as synaptic vesicle protein 2, cysteine string protein α, rab3, synapsin, and a group of proteins containing four transmembrane regions, which includes synaptophysin, synaptogyrin, and secretory carrier membrane protein, are involved in modulating the exocytotic process by regulating the formation and trafficking of synaptic vesicles.
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Affiliation(s)
- Ok-Ho Shin
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, Texas
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26
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Hwang S, Li Z, Bar-Peled Y, Aronov A, Ericson J, Bar-Peled M. The biosynthesis of UDP-d-FucNAc-4N-(2)-oxoglutarate (UDP-Yelosamine) in Bacillus cereus ATCC 14579: Pat and Pyl, an aminotransferase and an ATP-dependent Grasp protein that ligates 2-oxoglutarate to UDP-4-amino-sugars. J Biol Chem 2014; 289:35620-32. [PMID: 25368324 DOI: 10.1074/jbc.m114.614917] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Surface glycan switching is often observed when micro-organisms transition between different biotic and abiotic niches, including biofilms, although the advantages of this switching to the organism are not well understood. Bacillus cereus grown in a biofilm-inducing medium has been shown to synthesize an unusual cell wall polysaccharide composed of the repeating subunit →6)Gal(α1-2)(2-R-hydroxyglutar-5-ylamido)Fuc2NAc4N(α1-6)GlcNAc(β1→, where galactose is linked to the hydroxyglutarate moiety of FucNAc-4-amido-(2)-hydroxyglutarate. The molecular mechanism involved in attaching 2-hydroxyglutarate to 4-amino-FucNAc has not been determined. Here, we show two genes in B. cereus ATCC 14579 encoding enzymes involved in the synthesis of UDP-FucNAc-4-amido-(2)-oxoglutarate (UDP-Yelosamine), a modified UDP-sugar not previously reported to exist. Using mass spectrometry and real time NMR spectroscopy, we show that Bc5273 encodes a C4″-aminotransferase (herein referred to as Pat) that, in the presence of pyridoxal phosphate, transfers the primary amino group of l-Glu to C-4″ of UDP-4-keto-6-deoxy-d-GlcNAc to form UDP-4-amino-FucNAc and 2-oxoglutarate. Pat also converts 4-keto-xylose, 4-keto-glucose, and 4-keto-2-acetamido-altrose to their corresponding UDP-4-amino-sugars. Bc5272 encodes a carboxylate-amine ligase (herein referred as Pyl) that, in the presence of ATP and Mg(II), adds 2-oxoglutarate to the 4-amino moiety of UDP-4-amino-FucNAc to form UDP-Yelosamine and ADP. Pyl is also able to ligate 2-oxoglutarate to other 4-amino-sugar derivatives to form UDP-Yelose, UDP-Solosamine, and UDP-Aravonose. Characterizing the metabolic pathways involved in the formation of modified nucleotide sugars provides a basis for understanding some of the mechanisms used by bacteria to modify or alter their cell surface polysaccharides in response to changing growth and environmental challenges.
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Affiliation(s)
- Soyoun Hwang
- From the Complex Carbohydrate Research Center and
| | - Zi Li
- From the Complex Carbohydrate Research Center and Department of Plant Biology, University of Georgia, Athens, Georgia 30602
| | | | - Avi Aronov
- From the Complex Carbohydrate Research Center and
| | | | - Maor Bar-Peled
- From the Complex Carbohydrate Research Center and Department of Plant Biology, University of Georgia, Athens, Georgia 30602
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27
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Wang Y, Xu H, Harich KC, White RH. Identification and Characterization of a Tyramine–Glutamate Ligase (MfnD) Involved in Methanofuran Biosynthesis. Biochemistry 2014; 53:6220-30. [DOI: 10.1021/bi500879h] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Yu Wang
- Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, United States
| | - Huimin Xu
- Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, United States
| | - Kim C. Harich
- Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, United States
| | - Robert H. White
- Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, United States
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Giovedí S, Corradi A, Fassio A, Benfenati F. Involvement of synaptic genes in the pathogenesis of autism spectrum disorders: the case of synapsins. Front Pediatr 2014; 2:94. [PMID: 25237665 PMCID: PMC4154395 DOI: 10.3389/fped.2014.00094] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Accepted: 08/21/2014] [Indexed: 12/03/2022] Open
Abstract
Autism spectrum disorders (ASDs) are heterogeneous neurodevelopmental disorders characterized by deficits in social interaction and social communication, restricted interests, and repetitive behaviors. Many synaptic protein genes are linked to the pathogenesis of ASDs, making them prototypical synaptopathies. An array of mutations in the synapsin (Syn) genes in humans has been recently associated with ASD and epilepsy, diseases that display a frequent comorbidity. Syns are pre-synaptic proteins regulating synaptic vesicle traffic, neurotransmitter release, and short-term synaptic plasticity. In doing so, Syn isoforms control the tone of activity of neural circuits and the balance between excitation and inhibition. As ASD pathogenesis is believed to result from dysfunctions in the balance between excitatory and inhibitory transmissions in neocortical areas, Syns are novel ASD candidate genes. Accordingly, deletion of single Syn genes in mice, in addition to epilepsy, causes core symptoms of ASD by affecting social behavior, social communication, and repetitive behaviors. Thus, Syn knockout mice represent a good experimental model to define synaptic alterations involved in the pathogenesis of ASD and epilepsy.
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Affiliation(s)
- Silvia Giovedí
- Department of Experimental Medicine, University of Genova , Genova , Italy
| | - Anna Corradi
- Department of Experimental Medicine, University of Genova , Genova , Italy
| | - Anna Fassio
- Department of Experimental Medicine, University of Genova , Genova , Italy ; Department of Neuroscience and Brain Technologies, Fondazione Istituto Italiano di Tecnologia , Genova , Italy
| | - Fabio Benfenati
- Department of Experimental Medicine, University of Genova , Genova , Italy ; Department of Neuroscience and Brain Technologies, Fondazione Istituto Italiano di Tecnologia , Genova , Italy
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Diegelmann S, Klagges B, Michels B, Schleyer M, Gerber B. Maggot learning and Synapsin function. ACTA ACUST UNITED AC 2013; 216:939-51. [PMID: 23447663 DOI: 10.1242/jeb.076208] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Drosophila larvae are focused on feeding and have few neurons. Within these bounds, however, there still are behavioural degrees of freedom. This review is devoted to what these elements of flexibility are, and how they come about. Regarding odour-food associative learning, the emerging working hypothesis is that when a mushroom body neuron is activated as a part of an odour-specific set of mushroom body neurons, and coincidently receives a reinforcement signal carried by aminergic neurons, the AC-cAMP-PKA cascade is triggered. One substrate of this cascade is Synapsin, and therefore this review features a general and comparative discussion of Synapsin function. Phosphorylation of Synapsin ensures an alteration of synaptic strength between this mushroom body neuron and its target neuron(s). If the trained odour is encountered again, the pattern of mushroom body neurons coding this odour is activated, such that their modified output now allows conditioned behaviour. However, such an activated memory trace does not automatically cause conditioned behaviour. Rather, in a process that remains off-line from behaviour, the larvae compare the value of the testing situation (based on gustatory input) with the value of the odour-activated memory trace (based on mushroom body output). The circuit towards appetitive conditioned behaviour is closed only if the memory trace suggests that tracking down the learned odour will lead to a place better than the current one. It is this expectation of a positive outcome that is the immediate cause of appetitive conditioned behaviour. Such conditioned search for reward corresponds to a view of aversive conditioned behaviour as conditioned escape from punishment, which is enabled only if there is something to escape from - much in the same way as we only search for things that are not there, and run for the emergency exit only when there is an emergency. One may now ask whether beyond 'value' additional information about reinforcement is contained in the memory trace, such as information about the kind and intensity of the reinforcer used. The Drosophila larva may allow us to develop satisfyingly detailed accounts of such mnemonic richness - if it exists.
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Affiliation(s)
- Sören Diegelmann
- Leibniz Institut für Neurobiologie (LIN), Abteilung Genetik von Lernen und Gedächtnis, Brenneckestrasse 6, 39118 Magdeburg, Germany
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Giannandrea M, Guarnieri FC, Gehring NH, Monzani E, Benfenati F, Kulozik AE, Valtorta F. Nonsense-mediated mRNA decay and loss-of-function of the protein underlie the X-linked epilepsy associated with the W356× mutation in synapsin I. PLoS One 2013; 8:e67724. [PMID: 23818987 PMCID: PMC3688603 DOI: 10.1371/journal.pone.0067724] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Accepted: 05/21/2013] [Indexed: 11/22/2022] Open
Abstract
Synapsins are a family of neuronal phosphoproteins associated with the cytosolic surface of synaptic vesicles. Experimental evidence suggests a role for synapsins in synaptic vesicle clustering and recycling at the presynaptic terminal, as well as in neuronal development and synaptogenesis. Synapsin knock-out (Syn1(-/-) ) mice display an epileptic phenotype and mutations in the SYN1 gene have been identified in individuals affected by epilepsy and/or autism spectrum disorder. We investigated the impact of the c.1067G>A nonsense transition, the first mutation described in a family affected by X-linked syndromic epilepsy, on the expression and functional properties of the synapsin I protein. We found that the presence of a premature termination codon in the human SYN1 transcript renders it susceptible to nonsense-mediated mRNA decay (NMD). Given that the NMD efficiency is highly variable among individuals and cell types, we investigated also the effects of expression of the mutant protein and found that it is expressed at lower levels compared to wild-type synapsin I, forms perinuclear aggregates and is unable to reach presynaptic terminals in mature hippocampal neurons grown in culture. Taken together, these data indicate that in patients carrying the W356× mutation the function of synapsin I is markedly impaired, due to both the strongly decreased translation and the altered function of the NMD-escaped protein, and support the value of Syn1(-/-) mice as an experimental model mimicking the human pathology.
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MESH Headings
- Animals
- Blotting, Northern
- Cells, Cultured
- Codon, Nonsense
- Epilepsy/genetics
- Epilepsy/metabolism
- Female
- Gene Expression
- Genetic Diseases, X-Linked/genetics
- Genetic Diseases, X-Linked/metabolism
- HeLa Cells
- Hippocampus/cytology
- Hippocampus/metabolism
- Humans
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Microscopy, Fluorescence
- Microtubule-Associated Proteins/metabolism
- Neurons/metabolism
- Nonsense Mediated mRNA Decay
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Rats
- Rats, Sprague-Dawley
- Synapsins/genetics
- Synapsins/metabolism
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Affiliation(s)
- Maila Giannandrea
- Division of Neuroscience, San Raffaele Scientific Institute and Vita-Salute University, Milan, Italy
| | - Fabrizia C. Guarnieri
- Division of Neuroscience, San Raffaele Scientific Institute and Vita-Salute University, Milan, Italy
| | | | - Elena Monzani
- Division of Neuroscience, San Raffaele Scientific Institute and Vita-Salute University, Milan, Italy
| | - Fabio Benfenati
- Department of Neuroscience and Brain Technologies, The Italian Institute of Technology, Genoa, Italy
- Department of Experimental Medicine, University of Genoa, Genoa, Italy
| | - Andreas E. Kulozik
- Department of Pediatric Oncology, Hematology and Immunology, University of Heidelberg Medical Center and Molecular Medicine Partnership Unit, EMBL and University of Heidelberg, Heidelberg, Germany
| | - Flavia Valtorta
- Division of Neuroscience, San Raffaele Scientific Institute and Vita-Salute University, Milan, Italy
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Fawaz MV, Topper M, Firestine SM. The ATP-grasp enzymes. Bioorg Chem 2011; 39:185-91. [PMID: 21920581 PMCID: PMC3243065 DOI: 10.1016/j.bioorg.2011.08.004] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Revised: 08/12/2011] [Accepted: 08/13/2011] [Indexed: 12/17/2022]
Abstract
The ATP-grasp enzymes consist of a superfamily of 21 proteins that contain an atypical ATP-binding site, called the ATP-grasp fold. The ATP-grasp fold is comprised of two α+β domains that "grasp" a molecule of ATP between them and members of the family typically have an overall structural design containing three common conserved focal domains. The founding members of the family consist of biotin carboxylase, d-ala-d-ala ligase and glutathione synthetase, all of which catalyze the ATP-assisted reaction of a carboxylic acid with a nucleophile via the formation of an acylphosphate intermediate. While most members of the superfamily follow this mechanistic pathway, studies have demonstrated that two enzymes catalyze only the phosphoryl transfer step and thus are kinases instead of ligases. Members of the ATP-grasp superfamily are found in several metabolic pathways including de novo purine biosynthesis, gluconeogenesis, and fatty acid synthesis. Given the critical nature of these enzymes, researchers have actively sought the development of potent inhibitors of several members of the superfamily as antibacterial and anti-obseity agents. In this review, we will discuss the structure, function, mechanism, and inhibition of the ATP-grasp enzymes.
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Affiliation(s)
| | | | - Steven M. Firestine
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI 48201
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32
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Dopamine release and molecular modeling study of some coumarin derivatives. Neurochem Int 2011; 59:906-12. [DOI: 10.1016/j.neuint.2011.08.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2011] [Revised: 07/31/2011] [Accepted: 08/01/2011] [Indexed: 11/20/2022]
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Tubulin tyrosine ligase structure reveals adaptation of an ancient fold to bind and modify tubulin. Nat Struct Mol Biol 2011; 18:1250-8. [PMID: 22020298 PMCID: PMC3342691 DOI: 10.1038/nsmb.2148] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Accepted: 08/12/2011] [Indexed: 12/03/2022]
Abstract
Tubulin tyrosine ligase (TTL) catalyzes the post-translational C-terminal tyrosination of α–tubulin. Tyrosination regulates recruitment of microtubule interacting proteins. TTL is essential. Its loss causes morphogenic abnormalities and is associated with cancers of poor prognosis. We present the first crystal structure of TTL (from Xenopus tropicalis), defining the structural scaffold upon which the diverse TTL-like family of tubulin-modifying enzymes is built. TTL recognizes tubulin using a bipartite strategy. It engages the tubulin tail through low-affinity, high-specificity interactions, and co-opts what is otherwise a homo-oligomerization interface in structurally related ATP-grasp fold enzymes to form a tight hetero-oligomeric complex with the tubulin body. Small-angle X-ray scattering and functional analyses reveal that TTL forms an elongated complex with the tubulin dimer and prevents its incorporation into microtubules by capping the tubulin longitudinal interface, possibly modulating the partition of tubulin between monomeric and polymeric forms.
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Porton B, Wetsel WC, Kao HT. Synapsin III: role in neuronal plasticity and disease. Semin Cell Dev Biol 2011; 22:416-24. [PMID: 21827867 DOI: 10.1016/j.semcdb.2011.07.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2011] [Accepted: 07/13/2011] [Indexed: 12/31/2022]
Abstract
Synapsin III was discovered in 1998, more than two decades after the first two synapsins (synapsins I and II) were identified. Although the biology of synapsin III is not as well understood as synapsins I and II, this gene is emerging as an important factor in the regulation of the early stages of neurodevelopment and dopaminergic neurotransmission, and in certain neuropsychiatric illnesses. Molecular genetic and clinical studies of synapsin III have determined that its neurodevelopmental effects are exerted at the levels of neurogenesis and axonogenesis. In vitro voltammetry studies have shown that synapsin III can control dopamine release in the striatum. Since dopaminergic dysfunction is implicated in many neuropsychiatric conditions, one may anticipate that polymorphisms in synapsin III can exert pervasive effects, especially since it is localized to extrasynaptic sites. Indeed, mutations in this gene have been identified in individuals diagnosed with schizophrenia, bipolar disorder and multiple sclerosis. These and other findings indicate that the roles of synapsin III differ significantly from those of synapsins I and II. Here, we focus on the unique roles of the newest synapsin, and where relevant, compare and contrast these with the actions of synapsins I and II.
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Affiliation(s)
- Barbara Porton
- Department of Psychiatry and Human Behavior, Brown University, BioMedical Center, 171 Meeting Street, Room 187, Providence, RI 02912, USA
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35
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Nuwal T, Heo S, Lubec G, Buchner E. Mass spectrometric analysis of synapsins in Drosophila melanogaster and identification of novel phosphorylation sites. J Proteome Res 2010; 10:541-50. [PMID: 21028912 DOI: 10.1021/pr100746s] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Synapsins are synaptic vesicle-associated phosphoproteins that play a major role in the fine regulation of neurotransmitter release. In Drosophila, synapsins are required for complex behavior including learning and memory. Synapsin isoforms were immunoprecipitated from homogenates of wild-type Drosophila heads using monoclonal antibody 3C11. Synapsin null mutants (Syn(97)) served as negative controls. The eluted proteins were separated by SDS-PAGE and visualized by silver staining. Gel pieces picked from five bands specific for wild type were analyzed by nano-LC-ESI-MS/MS following multienzyme digestion (trypsin, chymotrypsin, AspN, subtilisin, pepsin, and proteinase K). The protein was unambiguously identified with high sequence coverage (90.83%). A number of sequence conflicts were observed and the N-terminal amino acid was identified as methionine rather than leucine expected from the cDNA sequence. Several peptides from the larger isoform demonstrated that the in-frame UAG stop codon at position 582 which separates two large open reading frames is read through by tRNAs for lysine. Seven novel phosphorylation sites in Drosophila synapsin were identified at Thr-86, Ser-87, Ser-464, Thr-466, Ser-538, Ser-961, and Tyr-982 and verified by phosphatase treatment. No phosphorylation was observed at the conserved PKA/CaM kinase-I/IV site (RRFS, edited to RGFS) in domain A or a potential PKA site near domain E.
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Affiliation(s)
- Tulip Nuwal
- Department of Neurobiology and Genetics, Biozentrum, University of Wuerzburg, Wuerzburg, Germany
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Fadden P, Huang KH, Veal JM, Steed PM, Barabasz AF, Foley B, Hu M, Partridge JM, Rice J, Scott A, Dubois LG, Freed TA, Silinski MAR, Barta TE, Hughes PF, Ommen A, Ma W, Smith ED, Spangenberg AW, Eaves J, Hanson GJ, Hinkley L, Jenks M, Lewis M, Otto J, Pronk GJ, Verleysen K, Haystead TA, Hall SE. Application of chemoproteomics to drug discovery: identification of a clinical candidate targeting hsp90. ACTA ACUST UNITED AC 2010; 17:686-94. [PMID: 20659681 DOI: 10.1016/j.chembiol.2010.04.015] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Revised: 03/16/2010] [Accepted: 04/14/2010] [Indexed: 12/15/2022]
Abstract
A chemoproteomics-based drug discovery strategy is presented that utilizes a highly parallel screening platform, encompassing more than 1000 targets, with a focused chemical library prior to target selection. This chemoproteomics-based process enables a data-driven selection of both the biological target and chemical hit after the screen is complete. The methodology has been exemplified for the purine binding proteome (proteins utilizing ATP, NAD, FAD). Screening of an 8000 member library yielded over 1500 unique protein-ligand interactions, which included novel hits for the oncology target Hsp90. The approach, which also provides broad target selectivity information, was used to drive the identification of a potent and orally active Hsp90 inhibitor, SNX-5422, which is currently in phase 1 clinical studies.
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De Franchi E, Schalon C, Messa M, Onofri F, Benfenati F, Rognan D. Binding of protein kinase inhibitors to synapsin I inferred from pair-wise binding site similarity measurements. PLoS One 2010; 5:e12214. [PMID: 20808948 PMCID: PMC2922380 DOI: 10.1371/journal.pone.0012214] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2010] [Accepted: 07/26/2010] [Indexed: 11/18/2022] Open
Abstract
Predicting off-targets by computational methods is getting increasing importance in early drug discovery stages. We herewith present a computational method based on binding site three-dimensional comparisons, which prompted us to investigate the cross-reaction of protein kinase inhibitors with synapsin I, an ATP-binding protein regulating neurotransmitter release in the synapse. Systematic pair-wise comparison of the staurosporine-binding site of the proto-oncogene Pim-1 kinase with 6,412 druggable protein-ligand binding sites suggested that the ATP-binding site of synapsin I may recognize the pan-kinase inhibitor staurosporine. Biochemical validation of this hypothesis was realized by competition experiments of staurosporine with ATP-gamma(35)S for binding to synapsin I. Staurosporine, as well as three other inhibitors of protein kinases (cdk2, Pim-1 and casein kinase type 2), effectively bound to synapsin I with nanomolar affinities and promoted synapsin-induced F-actin bundling. The selective Pim-1 kinase inhibitor quercetagetin was shown to be the most potent synapsin I binder (IC50 = 0.15 microM), in agreement with the predicted binding site similarities between synapsin I and various protein kinases. Other protein kinase inhibitors (protein kinase A and chk1 inhibitor), kinase inhibitors (diacylglycerolkinase inhibitor) and various other ATP-competitors (DNA topoisomerase II and HSP-90alpha inhibitors) did not bind to synapsin I, as predicted from a lower similarity of their respective ATP-binding sites to that of synapsin I. The present data suggest that the observed downregulation of neurotransmitter release by some but not all protein kinase inhibitors may also be contributed by a direct binding to synapsin I and phosphorylation-independent perturbation of synapsin I function. More generally, the data also demonstrate that cross-reactivity with various targets may be detected by systematic pair-wise similarity measurement of ligand-annotated binding sites.
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Affiliation(s)
- Enrico De Franchi
- Department of Neuroscience and Brain Technologies, The Italian Institute of Technology, Genova, Italy
| | - Claire Schalon
- Structural Chemogenomics, Laboratory of Therapeutic Innovation, CNRS UMR 7200, Université de Strasbourg, Illkirch, France
| | - Mirko Messa
- Department of Neuroscience and Brain Technologies, The Italian Institute of Technology, Genova, Italy
| | - Franco Onofri
- Department of Experimental Medicine, University of Genova and Istituto Nazionale di Neuroscienze, Genova, Italy
| | - Fabio Benfenati
- Department of Neuroscience and Brain Technologies, The Italian Institute of Technology, Genova, Italy
- Department of Experimental Medicine, University of Genova and Istituto Nazionale di Neuroscienze, Genova, Italy
| | - Didier Rognan
- Structural Chemogenomics, Laboratory of Therapeutic Innovation, CNRS UMR 7200, Université de Strasbourg, Illkirch, France
- * E-mail:
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38
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Messa M, Congia S, Defranchi E, Valtorta F, Fassio A, Onofri F, Benfenati F. Tyrosine phosphorylation of synapsin I by Src regulates synaptic-vesicle trafficking. J Cell Sci 2010; 123:2256-65. [PMID: 20530578 DOI: 10.1242/jcs.068445] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Synapsins are synaptic vesicle (SV)-associated phosphoproteins involved in the regulation of neurotransmitter release. Synapsins reversibly tether SVs to the cytoskeleton and their phosphorylation by serine/threonine kinases increases SV availability for exocytosis by impairing their association with SVs and/or actin. We recently showed that synapsin I, through SH3- or SH2-mediated interactions, activates Src and is phosphorylated by the same kinase at Tyr301. Here, we demonstrate that, in contrast to serine phosphorylation, Src-mediated tyrosine phosphorylation of synapsin I increases its binding to SVs and actin, and increases the formation of synapsin dimers, which are both potentially involved in SV clustering. Synapsin I phosphorylation by Src affected SV dynamics and was physiologically regulated in brain slices in response to depolarization. Expression of the non-phosphorylatable (Y301F) synapsin I mutant in synapsin-I-knockout neurons increased the sizes of the readily releasable and recycling pools of SVs with respect to the wild-type form, which is consistent with an increased availability of recycled SVs for exocytosis. The data provide a mechanism for the effects of Src on SV trafficking and indicate that tyrosine phosphorylation of synapsins, unlike serine phosphorylation, stimulates the reclustering of recycled SVs and their recruitment to the reserve pool.
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Affiliation(s)
- Mirko Messa
- Department of Experimental Medicine, University of Genova and Istituto Nazionale di Neuroscienze, Viale Benedetto XV 3, 161632 Genova, Italy
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Fornasiero EF, Bonanomi D, Benfenati F, Valtorta F. The role of synapsins in neuronal development. Cell Mol Life Sci 2010; 67:1383-96. [PMID: 20035364 PMCID: PMC11115787 DOI: 10.1007/s00018-009-0227-8] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2009] [Revised: 11/22/2009] [Accepted: 12/04/2009] [Indexed: 12/23/2022]
Abstract
The synapsins, the first identified synaptic vesicle-specific proteins, are phosphorylated on multiple sites by a number of protein kinases and are involved in neurite outgrowth and synapse formation as well as in synaptic transmission. In mammals, the synapsin family consists of at least 10 isoforms encoded by 3 distinct genes and composed by a mosaic of conserved and variable domains. The synapsins are highly conserved evolutionarily, and orthologues have been found in invertebrates and lower vertebrates. Within nerve terminals, synapsins are implicated in multiple interactions with presynaptic proteins and the actin cytoskeleton. Via these interactions, synapsins control several mechanisms important for neuronal homeostasis. In this review, we describe the main functional features of the synapsins, in relation to the complex role played by these phosphoproteins in neuronal development.
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Affiliation(s)
- Eugenio F. Fornasiero
- San Raffaele Scientific Institute, Vita-Salute University, Via Olgettina 58, 20132 Milan, Italy
- Unit of Molecular Neuroscience, The Italian Institute of Technology, Via Olgettina 58, 20132 Milan, Italy
| | - Dario Bonanomi
- San Raffaele Scientific Institute, Vita-Salute University, Via Olgettina 58, 20132 Milan, Italy
- Present Address: Salk Institute, 10010 North Torrey Pines Road, La Jolla, CA 92037 USA
- Unit of Molecular Neuroscience, The Italian Institute of Technology, Via Olgettina 58, 20132 Milan, Italy
| | - Fabio Benfenati
- Department of Neuroscience and Brain Technologies, The Italian Institute of Technology, Via Morego 30, 16163 Genoa, Italy
- Department of Experimental Medicine, University of Genova, Viale Benedetto XV, 3, 16132 Genoa, Italy
| | - Flavia Valtorta
- San Raffaele Scientific Institute, Vita-Salute University, Via Olgettina 58, 20132 Milan, Italy
- Unit of Molecular Neuroscience, The Italian Institute of Technology, Via Olgettina 58, 20132 Milan, Italy
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Terwilliger TC. Rapid model building of alpha-helices in electron-density maps. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2010; 66:268-75. [PMID: 20179338 PMCID: PMC2827347 DOI: 10.1107/s0907444910000314] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/07/2009] [Accepted: 01/04/2010] [Indexed: 12/04/2022]
Abstract
A method for the identification of alpha-helices in electron-density maps at low resolution followed by interpretation at moderate to high resolution is presented. Rapid identification is achieved at low resolution, where alpha-helices appear as tubes of density. The positioning and direction of the alpha-helices is obtained at moderate to high resolution, where the positions of side chains can be seen. The method was tested on a set of 42 experimental electron-density maps at resolutions ranging from 1.5 to 3.8 A. An average of 63% of the alpha-helical residues in these proteins were built and an average of 76% of the residues built matched helical residues in the refined models of the proteins. The overall average r.m.s.d. between main-chain atoms in the modeled alpha-helices and the nearest atom with the same name in the refined models of the proteins was 1.3 A.
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41
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Terwilliger TC. Rapid model building of beta-sheets in electron-density maps. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2010; 66:276-84. [PMID: 20179339 PMCID: PMC2827348 DOI: 10.1107/s0907444910000302] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/07/2009] [Accepted: 01/04/2010] [Indexed: 11/29/2022]
Abstract
A method for rapidly building beta-sheets into electron-density maps is presented. beta-Strands are identified as tubes of high density adjacent to and nearly parallel to other tubes of density. The alignment and direction of each strand are identified from the pattern of high density corresponding to carbonyl and C(beta) atoms along the strand averaged over all repeats present in the strand. The beta-strands obtained are then assembled into a single atomic model of the beta-sheet regions. The method was tested on a set of 42 experimental electron-density maps at resolutions ranging from 1.5 to 3.8 A. The beta-sheet regions were nearly completely built in all but two cases, the exceptions being one structure at 2.5 A resolution in which a third of the residues in beta-sheets were built and a structure at 3.8 A in which under 10% were built. The overall average r.m.s.d. of main-chain atoms in the residues built using this method compared with refined models of the structures was 1.5 A.
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42
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Terwilliger TC. Rapid chain tracing of polypeptide backbones in electron-density maps. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2010; 66:285-94. [PMID: 20179340 PMCID: PMC2827349 DOI: 10.1107/s0907444910000272] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/07/2009] [Accepted: 01/04/2010] [Indexed: 11/22/2022]
Abstract
A method for rapid chain tracing of polypeptide backbones at moderate resolution is presented. A method for the rapid tracing of polypeptide backbones has been developed. The method creates an approximate chain tracing that is useful for visual evaluation of whether a structure has been solved and for use in scoring the quality of electron-density maps. The essence of the method is to (i) sample candidate Cα positions at spacings of approximately 0.6 Å along ridgelines of high electron density, (ii) list all possible nonapeptides that satisfy simple geometric and density criteria using these candidate Cα positions, (iii) score the nonapeptides and choose the highest scoring ones, and (iv) find the longest chains that can be made by connecting nonamers. An indexing and storage scheme that allows a single calculation of most distances and density values is used to speed up the process. The method was applied to 42 density-modified electron-density maps at resolutions from 1.5 to 3.8 Å. A total of 21 428 residues in these maps were traced in 24 CPU min with an overall r.m.s.d. of 1.61 Å for Cα atoms compared with the known refined structures. The method appears to be suitable for rapid evaluation of electron-density map quality.
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Candiani S, Moronti L, Pennati R, De Bernardi F, Benfenati F, Pestarino M. The synapsin gene family in basal chordates: evolutionary perspectives in metazoans. BMC Evol Biol 2010; 10:32. [PMID: 20113475 PMCID: PMC2825198 DOI: 10.1186/1471-2148-10-32] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2009] [Accepted: 01/29/2010] [Indexed: 01/07/2023] Open
Abstract
Background Synapsins are neuronal phosphoproteins involved in several functions correlated with both neurotransmitter release and synaptogenesis. The comprehension of the basal role of the synapsin family is hampered in vertebrates by the existence of multiple synapsin genes. Therefore, studying homologous genes in basal chordates, devoid of genome duplication, could help to achieve a better understanding of the complex functions of these proteins. Results In this study we report the cloning and characterization of the Ciona intestinalis and amphioxus Branchiostoma floridae synapsin transcripts and the definition of their gene structure using available C. intestinalis and B. floridae genomic sequences. We demonstrate the occurrence, in both model organisms, of a single member of the synapsin gene family. Full-length synapsin genes were identified in the recently sequenced genomes of phylogenetically diverse metazoans. Comparative genome analysis reveals extensive conservation of the SYN locus in several metazoans. Moreover, developmental expression studies underline that synapsin is a neuronal-specific marker in basal chordates and is expressed in several cell types of PNS and in many, if not all, CNS neurons. Conclusion Our study demonstrates that synapsin genes are metazoan genes present in a single copy per genome, except for vertebrates. Moreover, we hypothesize that, during the evolution of synapsin proteins, new domains are added at different stages probably to cope up with the increased complexity in the nervous system organization. Finally, we demonstrate that protochordate synapsin is restricted to the post-mitotic phase of CNS development and thereby is a good marker of postmitotic neurons.
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Affiliation(s)
- Simona Candiani
- Department of Biology, University of Genoa, Viale Benedetto XV5, 16132 Genova, Italy.
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The highly conserved synapsin domain E mediates synapsin dimerization and phospholipid vesicle clustering. Biochem J 2010; 426:55-64. [PMID: 19922412 DOI: 10.1042/bj20090762] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Synapsins are abundant SV (synaptic vesicle)-associated phosphoproteins that regulate synapse formation and function. The highly conserved C-terminal domain E was shown to contribute to several synapsin functions, ranging from formation of the SV reserve pool to regulation of the kinetics of exocytosis and SV cycling, although the molecular mechanisms underlying these effects are unknown. In the present study, we used a synthetic 25-mer peptide encompassing the most conserved region of domain E (Pep-E) to analyse the role of domain E in regulating the interactions between synapsin I and liposomes mimicking the phospholipid composition of SVs (SV-liposomes) and other pre-synaptic protein partners. In affinity-chromatography and cross-linking assays, Pep-E bound to endogenous and purified exogenous synapsin I and strongly inhibited synapsin dimerization, indicating a role in synapsin oligomerization. Consistently, Pep-E (but not its scrambled version) counteracted the ability of holo-synapsin I to bind and coat phospholipid membranes, as analysed by AFM (atomic force microscopy) topographical scanning, and significantly decreased the clustering of SV-liposomes induced by holo-synapsin I in FRET (Förster resonance energy transfer) assays, suggesting a causal relationship between synapsin oligomerization and vesicle clustering. Either Pep-E or a peptide derived from domain C was necessary and sufficient to inhibit both dimerization and vesicle clustering, indicating the participation of both domains in these activities of synapsin I. The results provide a molecular explanation for the effects of domain E in nerve terminal physiology and suggest that its effects on the size and integrity of SV pools are contributed by the regulation of synapsin dimerization and SV clustering.
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Terwilliger TC, Adams PD, Read RJ, McCoy AJ, Moriarty NW, Grosse-Kunstleve RW, Afonine PV, Zwart PH, Hung LW. Decision-making in structure solution using Bayesian estimates of map quality: the PHENIX AutoSol wizard. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2009; 65:582-601. [PMID: 19465773 PMCID: PMC2685735 DOI: 10.1107/s0907444909012098] [Citation(s) in RCA: 733] [Impact Index Per Article: 48.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/14/2008] [Accepted: 03/31/2009] [Indexed: 11/13/2022]
Abstract
Ten measures of experimental electron-density-map quality are examined and the skewness of electron density is found to be the best indicator of actual map quality. A Bayesian approach to estimating map quality is developed and used in the PHENIX AutoSol wizard to make decisions during automated structure solution. Estimates of the quality of experimental maps are important in many stages of structure determination of macromolecules. Map quality is defined here as the correlation between a map and the corresponding map obtained using phases from the final refined model. Here, ten different measures of experimental map quality were examined using a set of 1359 maps calculated by re-analysis of 246 solved MAD, SAD and MIR data sets. A simple Bayesian approach to estimation of map quality from one or more measures is presented. It was found that a Bayesian estimator based on the skewness of the density values in an electron-density map is the most accurate of the ten individual Bayesian estimators of map quality examined, with a correlation between estimated and actual map quality of 0.90. A combination of the skewness of electron density with the local correlation of r.m.s. density gives a further improvement in estimating map quality, with an overall correlation coefficient of 0.92. The PHENIX AutoSol wizard carries out automated structure solution based on any combination of SAD, MAD, SIR or MIR data sets. The wizard is based on tools from the PHENIX package and uses the Bayesian estimates of map quality described here to choose the highest quality solutions after experimental phasing.
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Tsuchiya Y, Nakamura H, Kinoshita K. Discrimination between biological interfaces and crystal-packing contacts. Adv Appl Bioinform Chem 2008; 1:99-113. [PMID: 21918609 PMCID: PMC3169932 DOI: 10.2147/aabc.s4255] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
A discrimination method between biologically relevant interfaces and artificial crystal-packing contacts in crystal structures was constructed. The method evaluates protein-protein interfaces in terms of complementarities for hydrophobicity, electrostatic potential and shape on the protein surfaces, and chooses the most probable biological interfaces among all possible contacts in the crystal. The method uses a discriminator named as "COMP", which is a linear combination of the complementarities for the above three surface features and does not correlate with the contact area. The discrimination of homo-dimer interfaces from symmetry-related crystal-packing contacts based on the COMP value achieved the modest success rate. Subsequent detailed review of the discrimination results raised the success rate to about 88.8%. In addition, our discrimination method yielded some clues for understanding the interaction patterns in several examples in the PDB. Thus, the COMP discriminator can also be used as an indicator of the "biological-ness" of protein-protein interfaces.
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Affiliation(s)
- Yuko Tsuchiya
- Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minatoku, Tokyo, 108-8639, Japan
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Evergren E, Benfenati F, Shupliakov O. The synapsin cycle: a view from the synaptic endocytic zone. J Neurosci Res 2008; 85:2648-56. [PMID: 17455288 DOI: 10.1002/jnr.21176] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Although the synapsin phosphoproteins were discovered more than 30 years ago and are known to play important roles in neurotransmitter release and synaptogenesis, a complete picture of their functions within the nerve terminal is lacking. It has been shown that these proteins play an important role in the clustering of synaptic vesicles (SVs) at active zones and function as modulators of synaptic strength by acting at both pre- and postdocking levels. Recent studies have demonstrated that synapsins migrate to the endocytic zone of central synapses during neurotransmitter release, which suggests that there are additional functions for these proteins in SV recycling.
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Affiliation(s)
- E Evergren
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
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Abstract
G-proteins (guanine nucleotide-binding proteins) are membrane-attached proteins composed of three subunits, alpha, beta, and gamma. They transduce signals from G-protein coupled receptors (GPCRs) to target effector proteins. The agonistactivated receptor induces a conformational change in the G-protein trimer so that the alpha-subunit binds GTP in exchange for GDP and alpha-GTP, and betagamma-subunits separate to interact with the target effector. Effector-interaction is terminated by the alpha-subunit GTPase activity, whereby bound GTP is hydrolyzed to GDP. This is accelerated in situ by RGS proteins, acting as GTPase-activating proteins (GAPs). Galpha-GDP and Gbetagamma then reassociate to form the Galphabetagamma trimer. G-proteins primarily involved in the modulation of neurotransmitter release are G(o), G(q) and G(s). G(o) mediates the widespread presynaptic auto-inhibitory effect of many neurotransmitters (e.g., via M2/M4 muscarinic receptors, alpha(2) adrenoreceptors, micro/delta opioid receptors, GABAB receptors). The G(o) betagamma-subunit acts in two ways: first, and most ubiquitously, by direct binding to CaV2 Ca(2+) channels, resulting in a reduced sensitivity to membrane depolarization and reduced Ca(2+) influx during the terminal action potential; and second, through a direct inhibitory effect on the transmitter release machinery, by binding to proteins of the SNARE complex. G(s) and G(q) are mainly responsible for receptor-mediated facilitatory effects, through activation of target enzymes (adenylate cyclase, AC and phospholipase-C, PLC respectively) by the GTP-bound alpha-subunits.
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Affiliation(s)
- David A Brown
- Department of Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.
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Füser G, Steinbüchel A. Analysis of genome sequences for genes of cyanophycin metabolism: identifying putative cyanophycin metabolizing prokaryotes. Macromol Biosci 2007; 7:278-96. [PMID: 17390395 DOI: 10.1002/mabi.200600207] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
CGP, a copolymer of aspartate and arginine, serves as a storage compound for nitrogen, carbon and energy in many cyanobacteria. Analysis of available genome sequences from prokaryotes identified ORFs putatively encoding proteins of high similarity to known cyanophycin synthetases and cyanophycinases from cyanobacteria in various strains of bacteria belonging to different phylogenetic taxa and not closely related to cyanobacteria. Genes of CGP metabolism occur in a wide range of bacteria exhibiting diverse metabolic capabilities, including aerobic and anaerobic respiration, fermentation, phototrophy and chemolithoautotrophy. This study identified different groups of cyanophycin synthetases and cyanophycinases, respectively, and proposes a collective terminology for the putative genes and enzymes of cyanophycin metabolism. Among 570 different microbial strains, whose genomes have been partially or completely sequenced and are publicly accessible, we identified 44 prokaryotes which possess a cyanophycin synthetase and are putatively able to synthesize CGP. From these, 31 prokaryotes harbor also a cyanophycinase enabling them to degrade CGP to dipeptides. From the latter, 24 strains possess in addition a dipeptidase necessary to hydrolyze beta-Asp-Arg dipeptides, thereby enabling them to completely utilize CGP. Therefore, CGP seems to have a much wider distribution among prokaryotes than previously recognized. Genes putatively encoding cyanophycin synthetase homologues were not identified in the genomes of Eukarya and Archaea and are therefore obviously only occurring in Eubacteria. In addition, the outcome of this detailed in silico analysis proposes to distinguish 10 different groups of cyanophycin synthetases.
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Affiliation(s)
- Gregor Füser
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Corrensstrasse 3, Münster, Germany
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Alaedini A, Okamoto H, Briani C, Wollenberg K, Shill HA, Bushara KO, Sander HW, Green PHR, Hallett M, Latov N. Immune cross-reactivity in celiac disease: anti-gliadin antibodies bind to neuronal synapsin I. THE JOURNAL OF IMMUNOLOGY 2007; 178:6590-5. [PMID: 17475890 DOI: 10.4049/jimmunol.178.10.6590] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Celiac disease is an immune-mediated disorder triggered by ingestion of wheat gliadin and related proteins in genetically susceptible individuals. In addition to the characteristic enteropathy, celiac disease is associated with various extraintestinal manifestations, including neurologic complications such as neuropathy, ataxia, seizures, and neurobehavioral changes. The cause of the neurologic manifestations is unknown, but autoimmunity resulting from molecular mimicry between gliadin and nervous system proteins has been proposed to play a role. In this study, we sought to investigate the immune reactivity of the anti-gliadin Ab response toward neural proteins. We characterized the binding of affinity-purified anti-gliadin Abs from immunized animals to brain proteins by one- and two-dimensional gel electrophoresis, immunoblotting, and peptide mass mapping. The major immunoreactive protein was identified as synapsin I. Anti-gliadin Abs from patients with celiac disease also bound to the protein. Such cross-reactivity may provide clues into the pathogenic mechanism of the neurologic deficits that are associated with gluten sensitivity.
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Affiliation(s)
- Armin Alaedini
- Department of Neurology and Neuroscience, Cornell University, and St. Vincent's Hospital Manhattan, New York, NY 10021, USA.
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