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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] [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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Benfenati F, Onofri F, Giovedí S. Protein-protein interactions and protein modules in the control of neurotransmitter release. Philos Trans R Soc Lond B Biol Sci 1999; 354:243-57. [PMID: 10212473 PMCID: PMC1692491 DOI: 10.1098/rstb.1999.0376] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Information transfer among neurons is operated by neurotransmitters stored in synaptic vesicles and released to the extracellular space by an efficient process of regulated exocytosis. Synaptic vesicles are organized into two distinct functional pools, a large reserve pool in which vesicles are restrained by the actin-based cytoskeleton, and a quantitatively smaller releasable pool in which vesicles approach the presynaptic membrane and eventually fuse with it on stimulation. Both synaptic vesicle trafficking and neurotransmitter release depend on a precise sequence of events that include release from the reserve pool, targeting to the active zone, docking, priming, fusion and endocytotic retrieval of synaptic vesicles. These steps are mediated by a series of specific interactions among cytoskeletal, synaptic vesicle, presynaptic membrane and cytosolic proteins that, by acting in concert, promote the spatial and temporal regulation of the exocytotic machinery. The majority of these interactions are mediated by specific protein modules and domains that are found in many proteins and are involved in numerous intracellular processes. In this paper, the possible physiological role of these multiple protein-protein interactions is analysed, with ensuing updating and clarification of the present molecular model of the process of neurotransmitter release.
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Affiliation(s)
- F Benfenati
- Department of Neuroscience, University of Roma Tor Vergata, Italy
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