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Mahapatra S, Takahashi T. Physiological roles of endocytosis and presynaptic scaffold in vesicle replenishment at fast and slow central synapses. eLife 2024; 12:RP90497. [PMID: 38829367 PMCID: PMC11147502 DOI: 10.7554/elife.90497] [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] [Indexed: 06/05/2024] Open
Abstract
After exocytosis, release sites are cleared of vesicular residues to replenish with transmitter-filled vesicles. Endocytic and scaffold proteins are thought to underlie this site-clearance mechanism. However, the physiological significance of this mechanism at diverse mammalian central synapses remains unknown. Here, we tested this in a physiologically optimized condition using action potential evoked EPSCs at fast calyx synapse and relatively slow hippocampal CA1 synapse, in post-hearing mice brain slices at 37°C and in 1.3 mM [Ca2+]. Pharmacological block of endocytosis enhanced synaptic depression at the calyx synapse, whereas it attenuated synaptic facilitation at the hippocampal synapse. Block of scaffold protein activity likewise enhanced synaptic depression at the calyx but had no effect at the hippocampal synapse. At the fast calyx synapse, block of endocytosis or scaffold protein activity significantly enhanced synaptic depression as early as 10 ms after the stimulation onset. Unlike previous reports, neither endocytic blockers nor scaffold protein inhibitors prolonged the recovery from short-term depression. We conclude that the release-site clearance by endocytosis can be a universal phenomenon supporting vesicle replenishment at both fast and slow synapses, whereas the presynaptic scaffold mechanism likely plays a specialized role in vesicle replenishment predominantly at fast synapses.
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Affiliation(s)
- Satyajit Mahapatra
- Cellular and Molecular Synaptic Function Unit, Okinawa Institute of Science and Technology - Graduate UniversityOkinawaJapan
| | - Tomoyuki Takahashi
- Cellular and Molecular Synaptic Function Unit, Okinawa Institute of Science and Technology - Graduate UniversityOkinawaJapan
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2
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Mustafá ER, Weiß K, Weiss N. Secretory carrier-associated membrane protein 5 regulates cell-surface targeting of T-type calcium channels. Channels (Austin) 2023; 17:2230776. [PMID: 37389974 PMCID: PMC10316736 DOI: 10.1080/19336950.2023.2230776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 06/15/2023] [Accepted: 06/21/2023] [Indexed: 07/02/2023] Open
Abstract
Missense mutations in the human secretary carrier-associated membrane protein 5 (SCAMP5) cause a variety of neurological disorders including neurodevelopmental delay, epilepsy, and Parkinson's disease. We recently documented the importance of SCAMP2 in the regulation of T-type calcium channel expression in the plasma membrane. Here, we show that similar to SCAMP2, the co-expression of SCAMP5 in tsA-201 cells expressing recombinant Cav3.1, Cav3.2, and Cav3.3 channels nearly abolished whole-cell T-type currents. Recording of intramembrane charge movements revealed that SCAMP5-induced inhibition of T-type currents is primarily caused by the reduced expression of functional channels in the plasma membrane. Moreover, we show that SCAMP5-mediated downregulation of Cav3.2 channels is essentially preserved with disease-causing SCAMP5 R91W and G180W mutations. Hence, this study extends our previous findings with SCAMP2 and indicates that SCAMP5 also contributes to repressing the expression of T-type channels in the plasma membrane.
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Affiliation(s)
- Emilio R. Mustafá
- Department of Pathophysiology, Third Faculty of Medicine, Charles University, Prague, Czech Republic
- Electrophysiology Laboratory of the Multidisciplinary Institute of Cell Biology (Argentine Research Council CONICET, Scientific Research Commission of the Buenos Aires Province and National University of La Plata, La Plata, Buenos Aires, Argentina
| | - Konstantin Weiß
- Department of Pathophysiology, Third Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Norbert Weiss
- Department of Pathophysiology, Third Faculty of Medicine, Charles University, Prague, Czech Republic
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3
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Synaptic vesicle proteins and ATG9A self-organize in distinct vesicle phases within synapsin condensates. Nat Commun 2023; 14:455. [PMID: 36709207 PMCID: PMC9884207 DOI: 10.1038/s41467-023-36081-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2022] [Accepted: 01/16/2023] [Indexed: 01/30/2023] Open
Abstract
Ectopic expression in fibroblasts of synapsin 1 and synaptophysin is sufficient to generate condensates of vesicles highly reminiscent of synaptic vesicle (SV) clusters and with liquid-like properties. Here we show that unlike synaptophysin, other major integral SV membrane proteins fail to form condensates with synapsin, but co-assemble into the clusters formed by synaptophysin and synapsin in this ectopic expression system. Another vesicle membrane protein, ATG9A, undergoes activity-dependent exo-endocytosis at synapses, raising questions about the relation of ATG9A traffic to the traffic of SVs. We find that both in fibroblasts and in nerve terminals ATG9A does not co-assemble into synaptophysin-positive vesicle condensates but localizes on a distinct class of vesicles that also assembles with synapsin but into a distinct phase. Our findings suggest that ATG9A undergoes differential sorting relative to SV proteins and also point to a dual role of synapsin in controlling clustering at synapses of SVs and ATG9A vesicles.
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4
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Chen Y, Fan J, Xiao D, Li X. The role of SCAMP5 in central nervous system diseases. Neurol Res 2022; 44:1024-1037. [PMID: 36217917 DOI: 10.1080/01616412.2022.2107754] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
OBJECTIVE Secretory carrier membrane proteins (SCAMPs) constitute a group of membrane transport proteins in plants, insects and mammals. The mammalian genome contains five types of SCAMP genes, namely, SCAMP1-SCAMP5. SCAMPs participate in the vesicle cycling fusion of vesicles and cell membranes and play roles in regulating exocytosis and endocytosis, activating synaptic function and transmitting nerve signals. Among these proteins, SCAMP5 is highly expressed in the brain and has direct or indirect effects on the function of the central nervous system. This paper may allow us to better understand the role of SCAMP5 in the central nervous system diseases. SCAMP5 regulates membrane transport, controls the exocytosis of SVs and is related to secretion carrier and membrane function. In addition, SCAMP5 plays a major role in the normal maintenance of the physiological functions of nerve cells. This article summarizes the effects of SCAMP5 on nerve cell exocytosis, endocytosis and synaptic function, as well as the relationship between SCAMP5 and various neurological diseases, to better understand the role of SCAMP5 in the pathogenesis of neurological diseases. METHODS Through PubMed, this paper examined and analyzed the role of SCAMP5 in the central nervous system, as well as the relationship between SCAMP5 and various neurological diseases using the key terms "secretory carrier membrane proteins"," SCAMP5"," exocytosis"," endocytosis", "synaptic function", "central nervous system diseases" up to 01 March 2022. RESULTS SCAMP5 regulates membrane transport, controls the exocytosis of SVs and is related to secretion carrier and membrane function. In addition, SCAMP5 plays a major role in the normal maintenance of the physiological functions of nerve cells. CONCLUSION This article summarizes the effects of SCAMP5 on nerve cell exocytosis, endocytosis and synaptic function, as well as the relationship between SCAMP5 and various neurological diseases, to better understand the role of SCAMP5 in the pathogenesis of neurological diseases.
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Affiliation(s)
- Ye Chen
- Department of Emergency, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China.,Ministry of Education, Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Chengdu, Sichuan, China
| | - Jiali Fan
- Department of Emergency, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China.,Ministry of Education, Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Chengdu, Sichuan, China
| | - Dongqiong Xiao
- Department of Emergency, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China.,Ministry of Education, Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Chengdu, Sichuan, China
| | - Xihong Li
- Department of Emergency, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China.,Ministry of Education, Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Chengdu, Sichuan, China
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5
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Azarnia Tehran D, Maritzen T. Endocytic proteins: An expanding repertoire of presynaptic functions. Curr Opin Neurobiol 2022; 73:102519. [PMID: 35217312 DOI: 10.1016/j.conb.2022.01.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 01/14/2022] [Accepted: 01/19/2022] [Indexed: 12/16/2022]
Abstract
From a presynaptic perspective, neuronal communication mainly relies on two interdependent events: The fast Ca2+-triggered fusion of neurotransmitter-containing synaptic vesicles (SVs) and their subsequent high-fidelity reformation. To allow rapid neurotransmission, SVs have evolved into fascinating molecular nanomachines equipped with a well-defined set of proteins. However, upon exocytosis, SVs fully collapse into the presynaptic plasma membrane leading to the dispersal of their molecular components. While the canonical function of endocytic proteins at the presynapse was believed to be the retrieval of SV proteins via clathrin-mediated endocytosis, it is now evident that clathrin-independent endocytic mechanisms predominate. We will highlight in how far these mechanisms still rely on the classical endocytic machinery and discuss the emerging functions of endocytic proteins in release site clearance and SV reformation from endosomal-like vacuoles.
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Affiliation(s)
- Domenico Azarnia Tehran
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Roessle-Straße 10, 13125, Berlin, Germany. https://twitter.com/@DomenicoAzTe
| | - Tanja Maritzen
- Department of Nanophysiology, Technische Universität Kaiserslautern, Paul-Ehrlich-Straße 23, 67663, Kaiserslautern, Germany.
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6
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Ghanem MH, Shih AJ, Vashistha H, Coke LN, Li W, Kim SJ, Simpfendorfer KR, Gregersen PK. Investigations into SCAMP5, a candidate lupus risk gene expressed in plasmacytoid dendritic cells. Lupus Sci Med 2021; 8:8/1/e000567. [PMID: 34728555 PMCID: PMC8565557 DOI: 10.1136/lupus-2021-000567] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Accepted: 10/01/2021] [Indexed: 11/08/2022]
Abstract
Objective We have investigated the molecular function of SCAMP5, a candidate risk gene for SLE exclusively expressed in plasmacytoid dendritic cells (pDCs) among peripheral leucocytes. Methods We tested the independence of the association in SCAMP5 with SLE by performing conditional analyses. We profiled the expression pattern of SCAMP5 among circulating leucocytes at the transcript and protein levels. Using lentiviral vectors, we localised the subcellular distribution of SCAMP5 alongside the interferon secretory pathway. We analysed pDCs for the expression of SCAMP5 and interferon production capacity by SCAMP5 genotype. Finally, we examined pDC-specific SCAMP5 isoforms by total RNAseq analysis and examined for genotype-associated quantitative differences therein. Results A conditional analysis revealed evidence of an independent genetic association of SCAMP5 with SLE. Among circulating leucocytes, SCAMP5 is uniquely expressed in pDCs at the transcript and protein levels, with main presence in the Golgi apparatus and minor presence at the cell periphery. In live cells, SCAMP5 displayed dynamic Golgi-cell surface trafficking and localised with the interferon secretory pathway. SCAMP5 did not differ in expression levels in pDCs between genotyped donors; however, a transient interferon secretory defect was noted in pDCs from donors carrying the risk genotype. Conclusions SCAMP5 constitutes a novel SLE risk gene on the basis of genomic data and expression in a cell type widely implicated in SLE pathogenesis. While we could not find evidence of quantitative expression differences in SCAMP5 between genotyped donors, SCAMP5 remains an attractive gene to explore given its highly restricted expression pattern and colocalisation with interferon secretion.
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Affiliation(s)
- Mustafa H Ghanem
- The Institute of Molecular Medicine, Northwell Health Feinstein Institutes for Medical Research, Manhasset, New York, USA.,Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, New York, USA
| | - Andrew J Shih
- The Institute of Molecular Medicine, Northwell Health Feinstein Institutes for Medical Research, Manhasset, New York, USA
| | - Himanshu Vashistha
- The Institute of Molecular Medicine, Northwell Health Feinstein Institutes for Medical Research, Manhasset, New York, USA
| | - Latanya N Coke
- The Institute of Molecular Medicine, Northwell Health Feinstein Institutes for Medical Research, Manhasset, New York, USA
| | - Wentian Li
- The Institute of Molecular Medicine, Northwell Health Feinstein Institutes for Medical Research, Manhasset, New York, USA
| | - Sun Jung Kim
- The Institute of Molecular Medicine, Northwell Health Feinstein Institutes for Medical Research, Manhasset, New York, USA.,Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, New York, USA
| | - Kim R Simpfendorfer
- The Institute of Molecular Medicine, Northwell Health Feinstein Institutes for Medical Research, Manhasset, New York, USA .,Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, New York, USA
| | - Peter K Gregersen
- The Institute of Molecular Medicine, Northwell Health Feinstein Institutes for Medical Research, Manhasset, New York, USA .,Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, New York, USA
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7
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Yperman K, Papageorgiou AC, Merceron R, De Munck S, Bloch Y, Eeckhout D, Jiang Q, Tack P, Grigoryan R, Evangelidis T, Van Leene J, Vincze L, Vandenabeele P, Vanhaecke F, Potocký M, De Jaeger G, Savvides SN, Tripsianes K, Pleskot R, Van Damme D. Distinct EH domains of the endocytic TPLATE complex confer lipid and protein binding. Nat Commun 2021; 12:3050. [PMID: 34031427 PMCID: PMC8144573 DOI: 10.1038/s41467-021-23314-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 04/22/2021] [Indexed: 01/07/2023] Open
Abstract
Clathrin-mediated endocytosis (CME) is the gatekeeper of the plasma membrane. In contrast to animals and yeasts, CME in plants depends on the TPLATE complex (TPC), an evolutionary ancient adaptor complex. However, the mechanistic contribution of the individual TPC subunits to plant CME remains elusive. In this study, we used a multidisciplinary approach to elucidate the structural and functional roles of the evolutionary conserved N-terminal Eps15 homology (EH) domains of the TPC subunit AtEH1/Pan1. By integrating high-resolution structural information obtained by X-ray crystallography and NMR spectroscopy with all-atom molecular dynamics simulations, we provide structural insight into the function of both EH domains. Both domains bind phosphatidic acid with a different strength, and only the second domain binds phosphatidylinositol 4,5-bisphosphate. Unbiased peptidome profiling by mass-spectrometry revealed that the first EH domain preferentially interacts with the double N-terminal NPF motif of a previously unidentified TPC interactor, the integral membrane protein Secretory Carrier Membrane Protein 5 (SCAMP5). Furthermore, we show that AtEH/Pan1 proteins control the internalization of SCAMP5 via this double NPF peptide interaction motif. Collectively, our structural and functional studies reveal distinct but complementary roles of the EH domains of AtEH/Pan1 in plant CME and connect the internalization of SCAMP5 to the TPLATE complex.
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Affiliation(s)
- Klaas Yperman
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium
- VIB Center for Plant Systems Biology, Ghent, Belgium
| | - Anna C Papageorgiou
- CEITEC-Central European Institute of Technology, Masaryk University, Brno, Czech Republic
| | - Romain Merceron
- Department of Biochemistry and Microbiology, Ghent University, Ghent, Belgium
- VIB Center for Inflammation Research, Ghent, Belgium
| | - Steven De Munck
- Department of Biochemistry and Microbiology, Ghent University, Ghent, Belgium
- VIB Center for Inflammation Research, Ghent, Belgium
| | - Yehudi Bloch
- Department of Biochemistry and Microbiology, Ghent University, Ghent, Belgium
- VIB Center for Inflammation Research, Ghent, Belgium
| | - Dominique Eeckhout
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium
- VIB Center for Plant Systems Biology, Ghent, Belgium
| | - Qihang Jiang
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium
- VIB Center for Plant Systems Biology, Ghent, Belgium
| | - Pieter Tack
- Department of Chemistry, X-ray Microspectroscopy and Imaging - XMI Research Unit, Ghent University, Ghent, Belgium
| | - Rosa Grigoryan
- Department of Chemistry, Atomic & Mass Spectrometry - A&MS Research Unit, Ghent University, Ghent, Belgium
| | - Thomas Evangelidis
- CEITEC-Central European Institute of Technology, Masaryk University, Brno, Czech Republic
| | - Jelle Van Leene
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium
- VIB Center for Plant Systems Biology, Ghent, Belgium
| | - Laszlo Vincze
- Department of Chemistry, X-ray Microspectroscopy and Imaging - XMI Research Unit, Ghent University, Ghent, Belgium
| | - Peter Vandenabeele
- Department of Chemistry, X-ray Microspectroscopy and Imaging - XMI Research Unit, Ghent University, Ghent, Belgium
- Archaeometry Research Group, Department of Archaeology, Ghent University, Ghent, Belgium
| | - Frank Vanhaecke
- Department of Chemistry, Atomic & Mass Spectrometry - A&MS Research Unit, Ghent University, Ghent, Belgium
| | - Martin Potocký
- Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Prague 6, Czech Republic
| | - Geert De Jaeger
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium
- VIB Center for Plant Systems Biology, Ghent, Belgium
| | - Savvas N Savvides
- Department of Biochemistry and Microbiology, Ghent University, Ghent, Belgium.
- VIB Center for Inflammation Research, Ghent, Belgium.
| | | | - Roman Pleskot
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium.
- VIB Center for Plant Systems Biology, Ghent, Belgium.
- Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Prague 6, Czech Republic.
| | - Daniel Van Damme
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium.
- VIB Center for Plant Systems Biology, Ghent, Belgium.
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SCAMP5 plays a critical role in axonal trafficking and synaptic localization of NHE6 to adjust quantal size at glutamatergic synapses. Proc Natl Acad Sci U S A 2021; 118:2011371118. [PMID: 33372133 DOI: 10.1073/pnas.2011371118] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Glutamate uptake into synaptic vesicles (SVs) depends on cation/H+ exchange activity, which converts the chemical gradient (ΔpH) into membrane potential (Δψ) across the SV membrane at the presynaptic terminals. Thus, the proper recruitment of cation/H+ exchanger to SVs is important in determining glutamate quantal size, yet little is known about its localization mechanism. Here, we found that secretory carrier membrane protein 5 (SCAMP5) interacted with the cation/H+ exchanger NHE6, and this interaction regulated NHE6 recruitment to glutamatergic presynaptic terminals. Protein-protein interaction analysis with truncated constructs revealed that the 2/3 loop domain of SCAMP5 is directly associated with the C-terminal region of NHE6. The use of optical imaging and electrophysiological recording showed that small hairpin RNA-mediated knockdown (KD) of SCAMP5 or perturbation of SCAMP5/NHE6 interaction markedly inhibited axonal trafficking and the presynaptic localization of NHE6, leading to hyperacidification of SVs and a reduction in the quantal size of glutamate release. Knockout of NHE6 occluded the effect of SCAMP5 KD without causing additional defects. Together, our results reveal that as a key regulator of axonal trafficking and synaptic localization of NHE6, SCAMP5 could adjust presynaptic strength by regulating quantal size at glutamatergic synapses. Since both proteins are autism candidate genes, the reduced quantal size by interrupting their interaction may underscore synaptic dysfunction observed in autism.
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9
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Lee U, Ryu SH, Chang S. SCAMP5 mediates activity-dependent enhancement of NHE6 recruitment to synaptic vesicles during synaptic plasticity. Mol Brain 2021; 14:47. [PMID: 33663553 PMCID: PMC7934559 DOI: 10.1186/s13041-021-00763-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 02/24/2021] [Indexed: 01/02/2023] Open
Abstract
Na+(K+)/H+ exchanger 6 (NHE6) on synaptic vesicle (SV) is critical for the presynaptic regulation of quantal size at the glutamatergic synapses by converting the chemical gradient (ΔpH) into membrane potential (Δψ) across the SV membrane. We recently found that NHE6 directly interacts with secretory carrier membrane protein 5 (SCAMP5), and SCAMP5-dependent recruitment of NHE6 to SVs controls the strength of synaptic transmission by modulation of quantal size of glutamate release at rest. It is, however, unknown whether NHE6 recruitment by SCAMP5 plays a role during synaptic plasticity. Here, we found that the number of NHE6-positive presynaptic boutons was significantly increased by the chemical long-term potentiation (cLTP). Since cLTP involves new synapse formation, our results indicated that NHE6 was recruited not only to the existing presynaptic boutons but also to the newly formed presynaptic boutons. Knock down of SCAMP5 completely abrogated the enhancement of NHE6 recruitment by cLTP. Interestingly, despite an increase in the number of NHE6-positive boutons by cLTP, the quantal size of glutamate release at the presynaptic terminals remained unaltered. Together with our recent results, our findings indicate that SCAMP5-dependent recruitment of NHE6 plays a critical role in manifesting presynaptic efficacy not only at rest but also during synaptic plasticity. Since both are autism candidate genes, reduced presynaptic efficacy by interfering with their interaction may underlie the molecular mechanism of synaptic dysfunction observed in autism.
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Affiliation(s)
- Unghwi Lee
- Department of Physiology and Biomedical Sciences, Seoul National University College of Medicine, # 309 Medical Science Bldg, 103 Daehak-ro, Jongno-gu, Seoul, 03080, South Korea
| | - Seung Hyun Ryu
- Department of Physiology and Biomedical Sciences, Seoul National University College of Medicine, # 309 Medical Science Bldg, 103 Daehak-ro, Jongno-gu, Seoul, 03080, South Korea
| | - Sunghoe Chang
- Department of Physiology and Biomedical Sciences, Seoul National University College of Medicine, # 309 Medical Science Bldg, 103 Daehak-ro, Jongno-gu, Seoul, 03080, South Korea.
- Neuroscience Research Institute, Seoul National University College of Medicine, Seoul, 03080, South Korea.
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Jäpel M, Gerth F, Sakaba T, Bacetic J, Yao L, Koo SJ, Maritzen T, Freund C, Haucke V. Intersectin-Mediated Clearance of SNARE Complexes Is Required for Fast Neurotransmission. Cell Rep 2021; 30:409-420.e6. [PMID: 31940485 DOI: 10.1016/j.celrep.2019.12.035] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Revised: 11/11/2019] [Accepted: 12/12/2019] [Indexed: 12/12/2022] Open
Abstract
The rapid replenishment of release-ready synaptic vesicles (SVs) at a limiting number of presynaptic release sites is required to sustain high-frequency neurotransmission in CNS neurons. Failure to clear release sites from previously exocytosed material has been shown to impair vesicle replenishment and, therefore, fast neurotransmission. The identity of this material and the machinery that removes it from release sites have remained enigmatic. Here we show that the endocytic scaffold protein intersectin 1 clears release sites by direct SH3 domain-mediated association with a non-canonical proline-rich segment of synaptobrevin assembled into the SNARE complex for neuroexocytosis. Acute structure-based or sustained genetic interference with SNARE complex recognition by intersectin 1 causes a rapid stimulation frequency-dependent depression of neurotransmission due to impaired replenishment of release-ready SVs. These findings identify a key molecular mechanism that underlies exo-endocytic coupling during fast neurotransmitter release at central synapses.
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Affiliation(s)
- Maria Jäpel
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Department of Molecular Pharmacology & Cell Biology, 13125 Berlin, Germany
| | - Fabian Gerth
- Freie Universität Berlin, Faculty of Biology, Chemistry, Pharmacy, 14195 Berlin, Germany
| | - Takeshi Sakaba
- Doshisha University, Graduate School of Brain Science, Kyoto 610-0394, Japan
| | - Jelena Bacetic
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Department of Molecular Pharmacology & Cell Biology, 13125 Berlin, Germany; Freie Universität Berlin, Faculty of Biology, Chemistry, Pharmacy, 14195 Berlin, Germany
| | - Lijun Yao
- Max-Planck-Institute for Biophysical Chemistry, Department of Membrane Biophysics, 37077 Göttingen, Germany
| | - Seong-Joo Koo
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Department of Molecular Pharmacology & Cell Biology, 13125 Berlin, Germany
| | - Tanja Maritzen
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Department of Molecular Pharmacology & Cell Biology, 13125 Berlin, Germany
| | - Christian Freund
- Freie Universität Berlin, Faculty of Biology, Chemistry, Pharmacy, 14195 Berlin, Germany
| | - Volker Haucke
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Department of Molecular Pharmacology & Cell Biology, 13125 Berlin, Germany; Freie Universität Berlin, Faculty of Biology, Chemistry, Pharmacy, 14195 Berlin, Germany; NeuroCure Cluster of Excellence, Charité Universitätsmedizin Berlin, 10117 Berlin, Germany.
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11
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Park D, Wu Y, Lee SE, Kim G, Jeong S, Milovanovic D, De Camilli P, Chang S. Cooperative function of synaptophysin and synapsin in the generation of synaptic vesicle-like clusters in non-neuronal cells. Nat Commun 2021; 12:263. [PMID: 33431828 PMCID: PMC7801664 DOI: 10.1038/s41467-020-20462-z] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 12/02/2020] [Indexed: 02/01/2023] Open
Abstract
Clusters of tightly packed synaptic vesicles (SVs) are a defining feature of nerve terminals. While SVs are mobile within the clusters, the clusters have no boundaries consistent with a liquid phase. We previously found that purified synapsin, a peripheral SV protein, can assemble into liquid condensates and trap liposomes into them. How this finding relates to the physiological formation of SV clusters in living cells remains unclear. Here, we report that synapsin alone, when expressed in fibroblasts, has a diffuse cytosolic distribution. However, when expressed together with synaptophysin, an integral SV membrane protein previously shown to be localized on small synaptic-like microvesicles when expressed in non-neuronal cells, is sufficient to organize such vesicles in clusters highly reminiscent of SV clusters and with liquid-like properties. This minimal reconstitution system can be a powerful model to gain mechanistic insight into the assembly of structures which are of fundamental importance in synaptic transmission. Synaptic vesicle clusters were proposed to represent phase separated condensates. Here, the authors show that only two proteins, synapsin and synaptophysin, are sufficient to make vesicle clusters in fibroblasts which are similar to those found at synapses in morphology and liquid-like properties.
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Affiliation(s)
- Daehun Park
- Departments of Neuroscience and Cell Biology, Howard Hughes Medical Institute, Program in Cellular Neuroscience, Neurodegeneration and Repair, Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT, 06510, USA
| | - Yumei Wu
- Departments of Neuroscience and Cell Biology, Howard Hughes Medical Institute, Program in Cellular Neuroscience, Neurodegeneration and Repair, Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT, 06510, USA
| | - Sang-Eun Lee
- Department of Physiology and Biomedical Sciences, Seoul National University College of Medicine, Seoul, 03080, South Korea
| | - Goeun Kim
- Department of Physiology and Biomedical Sciences, Seoul National University College of Medicine, Seoul, 03080, South Korea
| | - Seonyoung Jeong
- Department of Physiology and Biomedical Sciences, Seoul National University College of Medicine, Seoul, 03080, South Korea
| | - Dragomir Milovanovic
- Departments of Neuroscience and Cell Biology, Howard Hughes Medical Institute, Program in Cellular Neuroscience, Neurodegeneration and Repair, Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT, 06510, USA.,Laboratory of Molecular Neuroscience, German Center for Neurodegenerative Diseases (DZNE), Charitéplatz 1, 10117, Berlin, Germany
| | - Pietro De Camilli
- Departments of Neuroscience and Cell Biology, Howard Hughes Medical Institute, Program in Cellular Neuroscience, Neurodegeneration and Repair, Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT, 06510, USA.
| | - Sunghoe Chang
- Department of Physiology and Biomedical Sciences, Seoul National University College of Medicine, Seoul, 03080, South Korea.
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12
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Carvalhais LG, Martinho VC, Ferreiro E, Pinheiro PS. Unraveling the Nanoscopic Organization and Function of Central Mammalian Presynapses With Super-Resolution Microscopy. Front Neurosci 2021; 14:578409. [PMID: 33584169 PMCID: PMC7874199 DOI: 10.3389/fnins.2020.578409] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 12/03/2020] [Indexed: 12/22/2022] Open
Abstract
The complex, nanoscopic scale of neuronal function, taking place at dendritic spines, axon terminals, and other minuscule structures, cannot be adequately resolved using standard, diffraction-limited imaging techniques. The last couple of decades saw a rapid evolution of imaging methods that overcome the diffraction limit imposed by Abbe's principle. These techniques, including structured illumination microscopy (SIM), stimulated emission depletion (STED), photo-activated localization microscopy (PALM), and stochastic optical reconstruction microscopy (STORM), among others, have revolutionized our understanding of synapse biology. By exploiting the stochastic nature of fluorophore light/dark states or non-linearities in the interaction of fluorophores with light, by using modified illumination strategies that limit the excitation area, these methods can achieve spatial resolutions down to just a few tens of nm or less. Here, we review how these advanced imaging techniques have contributed to unprecedented insight into the nanoscopic organization and function of mammalian neuronal presynapses, revealing new organizational principles or lending support to existing views, while raising many important new questions. We further discuss recent technical refinements and newly developed tools that will continue to expand our ability to delve deeper into how synaptic function is orchestrated at the nanoscopic level.
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Affiliation(s)
- Lia G Carvalhais
- Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,Center for Innovative Biomedicine and Biotechnology, University of Coimbra, Coimbra, Portugal.,Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
| | - Vera C Martinho
- Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,Center for Innovative Biomedicine and Biotechnology, University of Coimbra, Coimbra, Portugal.,Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
| | - Elisabete Ferreiro
- Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,Center for Innovative Biomedicine and Biotechnology, University of Coimbra, Coimbra, Portugal.,Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
| | - Paulo S Pinheiro
- Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,Center for Innovative Biomedicine and Biotechnology, University of Coimbra, Coimbra, Portugal.,Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
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13
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Jiao X, Morleo M, Nigro V, Torella A, D'Arrigo S, Ciaccio C, Pantaleoni C, Gong P, Grand K, Sanchez-Lara PA, Krier J, Fieg E, Stergachis A, Wang X, Yang Z. Identification of an Identical de Novo SCAMP5 Missense Variant in Four Unrelated Patients With Seizures and Severe Neurodevelopmental Delay. Front Pharmacol 2021; 11:599191. [PMID: 33390987 PMCID: PMC7775611 DOI: 10.3389/fphar.2020.599191] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 11/11/2020] [Indexed: 11/25/2022] Open
Abstract
Objective: To establish and broaden the phenotypic spectrum of secretory carrier membrane protein (SCAMP5) associated with epilepsy and neurodevelopmental delay. Methods: A Chinese patient was identified at the First Hospital of Peking University, and the three unrelated patients were recruited from two different countries (Italy and United States) through GeneMatcher. SCAMP5 pathogenic variants were identified by whole exome sequencing; clinical data of the patients were retrospectively collected and analyzed. Result: The onset age of seizures was ranged from 6 to 15 months. Patients had different types of seizures, including focal seizures, generalized tonic-clonic seizures and tonic seizure. One patient showed typical autism spectrum disorder (ASD) symptoms. Electroencephalogram (EEG) findings presented as focal or multifocal discharges, sometimes spreading to generalization. Brain magnetic resonance imaging (MRI) abnormalities were present in each patient. Severe intellectual disability and language and motor developmental disorders were found in our patients, with all patients having poor language development and were nonverbal at last follow-up. All but one of the patients could walk independently in childhood, but the ability to walk independently in one patient had deteriorated with age. All patients had abnormal neurological exam findings, mostly signs of extrapyramidal system involvement. Dysmorphic features were found in 2/4 patients, mainly in the face and trunk. All four unrelated patients were found to have the same heterozygous pathogenic SCAMP5 de novo variant (p. Gly180Trp). Conclusion: Epilepsy, severe developmental delay, abnormal neurological exam findings, with or without ASD or variably dysmorphic features and were common in patients with SCAMP5 variant. The onset time and type of seizure varied greatly. The EEG and brain MRI findings were not consistent, but diverse and nonspecific. The motor ability of patients with heterozygous SCAMP5 variant might have a regressive course; language development was more severely affected.
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Affiliation(s)
- Xianru Jiao
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Manuela Morleo
- Telethon Institute of Genetics and Medicine, Naples, Italy
| | - Vincenzo Nigro
- Telethon Institute of Genetics and Medicine, Naples, Italy.,Department of Precision Medicine, University of Campania "Luigi Vanvitelli", Naples, Italy
| | - Annalaura Torella
- Department of Precision Medicine, University of Campania "Luigi Vanvitelli", Naples, Italy
| | - Stefano D'Arrigo
- Developmental Neurology Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Claudia Ciaccio
- Developmental Neurology Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Chiara Pantaleoni
- Developmental Neurology Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Pan Gong
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Katheryn Grand
- Department of Pediatrics, Medical Genetics, Cedars-Sinai Medical Center, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - Pedro A Sanchez-Lara
- Department of Pediatrics, Medical Genetics, Cedars-Sinai Medical Center, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - Joel Krier
- Brigham and Women's Hospital, Boston, MA, United States
| | | | | | | | - Zhixian Yang
- Department of Pediatrics, Peking University First Hospital, Beijing, China
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14
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Cheadle L, Rivera SA, Phelps JS, Ennis KA, Stevens B, Burkly LC, Lee WCA, Greenberg ME. Sensory Experience Engages Microglia to Shape Neural Connectivity through a Non-Phagocytic Mechanism. Neuron 2020; 108:451-468.e9. [PMID: 32931754 DOI: 10.1016/j.neuron.2020.08.002] [Citation(s) in RCA: 94] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 05/10/2020] [Accepted: 08/05/2020] [Indexed: 12/21/2022]
Abstract
Sensory experience remodels neural circuits in the early postnatal brain through mechanisms that remain to be elucidated. Applying a new method of ultrastructural analysis to the retinogeniculate circuit, we find that visual experience alters the number and structure of synapses between the retina and the thalamus. These changes require vision-dependent transcription of the receptor Fn14 in thalamic relay neurons and the induction of its ligand TWEAK in microglia. Fn14 functions to increase the number of bulbous spine-associated synapses at retinogeniculate connections, likely contributing to the strengthening of the circuit that occurs in response to visual experience. However, at retinogeniculate connections near TWEAK-expressing microglia, TWEAK signals via Fn14 to restrict the number of bulbous spines on relay neurons, leading to the elimination of a subset of connections. Thus, TWEAK and Fn14 represent an intercellular signaling axis through which microglia shape retinogeniculate connectivity in response to sensory experience.
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Affiliation(s)
- Lucas Cheadle
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Samuel A Rivera
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Jasper S Phelps
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA; Program in Neuroscience, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Katelin A Ennis
- Research and Early Development, Biogen, 115 Broadway, Cambridge, MA 04142, USA
| | - Beth Stevens
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, 300 Longwood Avenue, Boston, MA 02115, USA
| | - Linda C Burkly
- Research and Early Development, Biogen, 115 Broadway, Cambridge, MA 04142, USA
| | - Wei-Chung Allen Lee
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, 300 Longwood Avenue, Boston, MA 02115, USA
| | - Michael E Greenberg
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA.
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15
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Bonnycastle K, Davenport EC, Cousin MA. Presynaptic dysfunction in neurodevelopmental disorders: Insights from the synaptic vesicle life cycle. J Neurochem 2020; 157:179-207. [PMID: 32378740 DOI: 10.1111/jnc.15035] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 04/14/2020] [Accepted: 04/22/2020] [Indexed: 12/11/2022]
Abstract
The activity-dependent fusion, retrieval and recycling of synaptic vesicles is essential for the maintenance of neurotransmission. Until relatively recently it was believed that most mutations in genes that were essential for this process would be incompatible with life, because of this fundamental role. However, an ever-expanding number of mutations in this very cohort of genes are being identified in individuals with neurodevelopmental disorders, including autism, intellectual disability and epilepsy. This article will summarize the current state of knowledge linking mutations in presynaptic genes to neurodevelopmental disorders by sequentially covering the various stages of the synaptic vesicle life cycle. It will also discuss how perturbations of specific stages within this recycling process could translate into human disease. Finally, it will also provide perspectives on the potential for future therapy that are targeted to presynaptic function.
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Affiliation(s)
- Katherine Bonnycastle
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.,Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, UK.,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK
| | - Elizabeth C Davenport
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.,Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, UK.,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK
| | - Michael A Cousin
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.,Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, UK.,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK
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16
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Absence of Sac2/INPP5F enhances the phenotype of a Parkinson's disease mutation of synaptojanin 1. Proc Natl Acad Sci U S A 2020; 117:12428-12434. [PMID: 32424101 PMCID: PMC7275725 DOI: 10.1073/pnas.2004335117] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Extensive genetic studies have identified numerous genes whose mutations results on Parkinson’s disease (PD), including synaptojanin 1 (SJ1/Park20), a nerve terminal enriched protein that includes an inositol 4-phosphatase domain (Sac domain). In addition, many PD candidate genes have been identified by genome-wide association studies, but for most of these genes, the link to PD remains hypothetical. One such gene is Sac2/INPP5F, which, interestingly, also includes an inositol 4-phosphatase domain. While Sac2KO mice do not show obvious defects, we show a striking synthetic effect in mice of the KO of Sac2 and the Sac domain mutation of SJ1 found in PD patients. These findings support a synergistic role of SJ1 and Sac2 on a PI4P pool whose dysfunction results in PD. Numerous genes whose mutations cause, or increase the risk of, Parkinson’s disease (PD) have been identified. An inactivating mutation (R258Q) in the Sac inositol phosphatase domain of synaptojanin 1 (SJ1/PARK20), a phosphoinositide phosphatase implicated in synaptic vesicle recycling, results in PD. The gene encoding Sac2/INPP5F, another Sac domain-containing protein, is located within a PD risk locus identified by genome-wide association studies. Knock-In mice carrying the SJ1 patient mutation (SJ1RQKI) exhibit PD features, while Sac2 knockout mice (Sac2KO) do not have obvious neurologic defects. We report a “synthetic” effect of the SJ1 mutation and the KO of Sac2 in mice. Most mice with both mutations died perinatally. The occasional survivors had stunted growth, died within 3 wk, and showed abnormalities of striatal dopaminergic nerve terminals at an earlier stage than SJ1RQKI mice. The abnormal accumulation of endocytic factors observed at synapses of cultured SJ1RQKI neurons was more severe in double-mutant neurons. Our results suggest that SJ1 and Sac2 have partially overlapping functions and are consistent with a potential role of Sac2 as a PD risk gene.
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17
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Deficiency of SCAMP5 leads to pediatric epilepsy and dysregulation of neurotransmitter release in the brain. Hum Genet 2020; 139:545-555. [PMID: 32020363 DOI: 10.1007/s00439-020-02123-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Accepted: 01/28/2020] [Indexed: 10/25/2022]
Abstract
Secretory carrier membrane proteins (SCAMPs) play an important role in exocytosis in animals, but the precise function of SCAMPs in human disease is unknown. In this study, we identified a homozygous mutation, SCAMP5 R91W, in a Chinese consanguineous family with pediatric epilepsy and juvenile Parkinson's disease. Scamp5 R91W mutant knock-in mice showed typical early-onset epilepsy similar to that in humans. Single-neuron electrophysiological recordings showed that the R91W mutation significantly increased the frequency of miniature excitatory postsynaptic currents (mEPSCs) at a resting state and also increased the amplitude of evoked EPSCs. The R91W mutation affected the interaction between SCAMP5 and synaptotagmin 1 and may affect the function of the SNARE complex, the machinery required for vesicular trafficking and neurotransmitter release. Our work shows that dysfunction of SCAMP5 shifted the excitation/inhibition balance of the neuronal network in the brain, and the deficiency of SCAMP5 leads to pediatric epilepsy.
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18
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Hubert L, Cannata Serio M, Villoing-Gaudé L, Boddaert N, Kaminska A, Rio M, Lyonnet S, Munnich A, Poirier K, Simons M, Besmond C. De novo SCAMP5 mutation causes a neurodevelopmental disorder with autistic features and seizures. J Med Genet 2019; 57:138-144. [DOI: 10.1136/jmedgenet-2018-105927] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 07/24/2019] [Accepted: 08/03/2019] [Indexed: 11/03/2022]
Abstract
BackgroundAutistic spectrum disorders (ASDs) with developmental delay and seizures are a genetically heterogeneous group of diseases caused by at least 700 different genes. Still, a number of cases remain genetically undiagnosed.ObjectiveThe objective of this study was to identify and characterise pathogenic variants in two individuals from unrelated families, both of whom presented a similar clinical phenotype that included an ASD, intellectual disability (ID) and seizures.MethodsWhole-exome sequencing was used to identify pathogenic variants in the two individuals. Functional studies performed in the Drosophila melanogaster model was used to assess the protein function in vivo.ResultsProbands shared a heterozygous de novo secretory carrier membrane protein (SCAMP5) variant (NM_001178111.1:c.538G>T) resulting in a p.Gly180Trp missense variant. SCAMP5 belongs to a family of tetraspanin membrane proteins found in secretory and endocytic compartments of neuronal synapses. In the fly SCAMP orthologue, the p.Gly302Trp genotype corresponds to human p.Gly180Trp. Western blot analysis of proteins overexpressed in the Drosophila fat body showed strongly reduced levels of the SCAMP p.Gly302Trp protein compared with the wild-type protein, indicating that the mutant either reduced expression or increased turnover of the protein. The expression of the fly homologue of the human SCAMP5 p.Gly180Trp mutation caused similar eye and neuronal phenotypes as the expression of SCAMP RNAi, suggesting a dominant-negative effect.ConclusionOur study identifies SCAMP5 deficiency as a cause for ASD and ID and underscores the importance of synaptic vesicular trafficking in neurodevelopmental disorders.
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