Affinage

SYN1

Synapsin-1 · UniProt P17600

Length
705 aa
Mass
74.1 kDa
Annotated
2026-04-28
30 papers in source corpus 7 papers cited in narrative 7 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

SYN1 encodes Synapsin I, a presynaptic phosphoprotein that governs synaptic vesicle pool size, clustering, mobility, and neurotransmitter release at both excitatory and inhibitory synapses. Its proline-rich D-domain is required for vesicle pool maintenance and nerve-terminal targeting, and disease-associated D-domain truncations (Q555X) selectively deplete the readily releasable pool at inhibitory synapses while increasing asynchronous release, causing network hyperexcitability (PMID:21441247, PMID:23406870). The B-domain senses membrane curvature; the S79W mutation traps vesicles in excessively tight clusters, elevates spontaneous excitatory release, and impairs vesicle mobility (PMID:28973667). SYN1 transcription is driven by Sp1 and Foxp2 binding to its promoter and repressed by REST and CpG methylation, while Cdk5-mediated phosphorylation at Ser-553 modulates vesicle anchoring and GABA release (PMID:23250796, PMID:31545395, PMID:35723394).

Mechanistic history

Synthesis pass · year-by-year structured walk · 6 steps
  1. 2011 High

    Establishing that the proline-rich D-domain is the critical determinant of Synapsin I's vesicle-regulatory function resolved which region of the protein controls vesicle pool size, trafficking, and nerve-terminal targeting.

    Evidence KO rescue in SynI-null hippocampal neurons with wild-type versus D-domain mutant (Q555X, A550T, T567A) human SYN1; live imaging, phosphorylation, and neurite outgrowth assays

    PMID:21441247

    Open questions at the time
    • Structural basis of D-domain interaction with vesicle or cytoskeletal partners not resolved
    • Whether D-domain mutations affect inhibitory versus excitatory terminals differently was not addressed
  2. 2012 High

    Identifying Sp1 as a direct transcriptional activator and REST as its antagonist at the SYN1 promoter established the core cis-regulatory logic controlling neuron-specific SYN1 expression.

    Evidence ChIP, co-immunoprecipitation, functional promoter assays, REST knockdown/overexpression in Neuro2a cells

    PMID:23250796

    Open questions at the time
    • Whether REST repression operates through recruitment of specific corepressors at the SYN1 locus was not determined
    • In vivo relevance of CpG methylation at Sp1 sites during neuronal differentiation not shown
  3. 2013 High

    Demonstrating that Q555X selectively depletes the readily releasable pool at inhibitory synapses while altering release probability at excitatory synapses explained how a single SYN1 mutation produces network hyperexcitability and epilepsy.

    Evidence Patch-clamp electrophysiology, electron microscopy, and multi-electrode arrays in SynI KO neurons expressing WT or Q555X-hSynI

    PMID:23406870

    Open questions at the time
    • Molecular basis for the differential impact on inhibitory versus excitatory terminals remains unclear
    • Whether asynchronous release increase is a direct consequence of vesicle pool depletion or an independent effect of the mutation
  4. 2017 High

    Mapping S79W to the membrane-curvature-sensing B-domain and showing it causes vesicle immobilization and aberrant clustering extended the functional map of Synapsin I beyond the D-domain to a distinct lipid-interaction surface.

    Evidence Expression of S79W SYN1 in Syn1 KO hippocampal neurons; fluorescence imaging, electrophysiology, vesicle mobility assays

    PMID:28973667

    Open questions at the time
    • Direct biophysical evidence for altered curvature sensing by the S79W B-domain not provided
    • Whether somatic vesicle accumulation reflects a trafficking defect or ectopic anchoring is unresolved
  5. 2019 Medium

    Identifying Foxp2 as a second transcriptional activator of SYN1, subject to miR-134-5p–mediated repression, added an additional regulatory layer to SYN1 expression control beyond Sp1/REST.

    Evidence ChIP-qPCR for Foxp2 at SYN1 promoter; dual luciferase assay for miR-134-5p targeting Foxp2; in vivo antagomir injection

    PMID:31545395

    Open questions at the time
    • Whether Foxp2 and Sp1 act cooperatively or independently at the SYN1 promoter is unknown
    • Single-lab finding; independent replication needed
  6. 2021 Medium

    Showing that Cdk5 negatively regulates SYN1 phosphorylation at Ser-553, thereby reducing GABA release, linked a specific kinase-substrate event to inhibitory neurotransmission.

    Evidence In vivo rat and in vitro experiments with Cdk5 inhibition/activation; western blotting for p-SYN1(Ser-553); GABA release measurements

    PMID:35723394

    Open questions at the time
    • Direct in vitro kinase assay for Cdk5 on Ser-553 not shown; inference is largely correlative
    • Whether Ser-553 phosphorylation state directly controls vesicle docking or a downstream step is unresolved

Open questions

Synthesis pass · forward-looking unresolved questions
  • How B-domain curvature sensing and D-domain protein interactions coordinate to position vesicles within the reserve versus readily releasable pools, and how phosphorylation at distinct sites integrates these functions in vivo, remains mechanistically unresolved.
  • No structural model of full-length Synapsin I on a vesicle membrane
  • Phosphorylation-dependent conformational changes linking kinase cascades to vesicle release have not been reconstituted biochemically
  • Relative contributions of individual Synapsin I domains to inhibitory versus excitatory synapse maintenance not systematically addressed

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0008092 cytoskeletal protein binding 2 GO:0008289 lipid binding 1
Localization
GO:0031410 cytoplasmic vesicle 3
Pathway
R-HSA-112316 Neuronal System 4 R-HSA-74160 Gene expression (Transcription) 3
Partners
CDK5FOXP2RESTSP1

Evidence

Reading pass · 7 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2011 SYN1 D-domain mutations (Q555X, A550T, T567A) fail to rescue synaptic vesicle pool size and trafficking defects in SynI knockout neurons, demonstrating that the proline-rich D-domain is essential for synaptic vesicle pool regulation. The Q555X nonsense mutation additionally impairs phosphorylation by MAPK/Erk and neurite outgrowth, while missense mutants A550T and T567A show impaired targeting to nerve terminals. SynI KO neuron rescue assay with human wild-type and mutant SynI expression; live imaging of synaptic vesicle pools; phosphorylation assays; neurite outgrowth assays Human molecular genetics High 21441247
2013 The epileptogenic Q555X SYN1 mutation causes a parallel decrease in the synaptic vesicle readily releasable pool in inhibitory synapses and reduced release probability in excitatory synapses, accompanied by increased asynchronous release and altered short-term plasticity, leading to network hyperexcitability. Patch-clamp electrophysiology, electron microscopy, multi-electrode arrays in SynI KO hippocampal neurons expressing wild-type or Q555X-hSynI via lentiviral transduction Human molecular genetics High 23406870
2017 The S79W SYN1 mutation, located in the B-domain involved in recognition of highly curved membranes, causes aberrant accumulation of small clear vesicles in the soma, increased clustering of synaptic vesicles at presynaptic terminals, increased frequency of excitatory spontaneous release events, and strongly reduced mobility of synaptic vesicles when expressed in Syn1 KO hippocampal neurons. Expression of human S79W Synapsin I in Syn1 KO hippocampal neurons; fluorescence imaging; electrophysiology; vesicle mobility assays Human molecular genetics High 28973667
2012 SYN1 gene transcription is activated by the transcription factor Sp1 binding to conserved GC-box cis-sites in the SYN1 promoter, and REST directly inhibits Sp1-mediated SYN1 transcription. CpG methylation of Sp1 cis-sites provides an additional level of SYN1 transcriptional repression. Functional promoter assays, ChIP, co-immunoprecipitation of Sp1 on SYN1 promoter, REST knockdown and overexpression in Neuro2a cells The Journal of biological chemistry High 23250796
2021 Cdk5 acts as a negative regulator of SYN1 phosphorylation at Ser-553; upregulation of Cdk5 via the Calpain-p25 pathway after microwave exposure decreases p-SYN1 (Ser-553), which leads to reduced GABA release, implicating Cdk5-mediated SYN1 phosphorylation in vesicular anchoring and neurotransmitter release regulation. In vivo (rat) and in vitro experiments with Cdk5 inhibition/activation, western blotting for p-SYN1, GABA release measurements, MEK inhibition controls Current issues in molecular biology Medium 35723394
2019 Foxp2 transcription factor binds the SYN1 promoter at −400/−600 bp upstream of the transcription start site, and miR-134-5p downregulates Foxp2, thereby reducing SYN1 expression and contributing to synaptic protein loss. ChIP-qPCR showing Foxp2 binding to SYN1 promoter; dual luciferase assay confirming miR-134-5p targeting Foxp2; Foxp2 silencing experiments; in vivo miR-134-5p antagomir injection International journal of molecular medicine Medium 31545395
2024 SP1 binds to the SYN1 promoter and positively regulates SYN1 expression; SYN1 knockdown reduces hemin-induced apoptosis, inflammation, and oxidative stress in PC12 cells, and si-SYN1 administration in ICH rats improves neurological function, reduces brain edema, and ameliorates blood-brain barrier disruption. ChIP and luciferase reporter assay for SP1-SYN1 promoter binding; si-SYN1 knockdown in PC12 cells and in vivo ICH rat model; LDH, CCK-8, TUNEL, western blotting, Evans blue extravasation assays Pathology, research and practice Medium 39561537

Source papers

Stage 0 corpus · 30 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2011 SYN1 loss-of-function mutations in autism and partial epilepsy cause impaired synaptic function. Human molecular genetics 189 21441247
1999 Isolation and characterization of SYN1, a RAD21-like gene essential for meiosis in Arabidopsis. The Plant cell 171 10072401
2003 The Arabidopsis SYN1 cohesin protein is required for sister chromatid arm cohesion and homologous chromosome pairing. Journal of cell science 170 12783989
2003 Epitope mapping and specificity of the anti-alpha-synuclein monoclonal antibody Syn-1 in mouse brain and cultured cell lines. Neuroscience letters 67 12946570
2013 Epileptogenic Q555X SYN1 mutant triggers imbalances in release dynamics and short-term plasticity. Human molecular genetics 54 23406870
1999 Meiotic activation of rat pachytene spermatocytes with okadaic acid: the behaviour of synaptonemal complex components SYN1/SCP1 and COR1/SCP3. Journal of cell science 50 9914155
2012 Specificity protein 1 (Sp1)-dependent activation of the synapsin I gene (SYN1) is modulated by RE1-silencing transcription factor (REST) and 5'-cytosine-phosphoguanine (CpG) methylation. The Journal of biological chemistry 48 23250796
2018 Gold-Catalyzed syn-1,2-Difunctionalization of Ynamides via Nitrile Activation. Organic letters 46 30540197
2008 Concise asymmetric synthesis of (+)-CP-99,994 and (+)-L-733,060 via efficient construction of homochiral syn-1,2-diamines and syn-1,2-amino alcohols. The Journal of organic chemistry 40 18331063
1993 Role of the Na+,K+ pump in herpes simplex type 1-induced cell fusion: melittin causes specific reversion of syncytial mutants with the syn1 mutation to Syn+ (wild-type) phenotype. Virology 37 8396802
2017 A novel SYN1 missense mutation in non-syndromic X-linked intellectual disability affects synaptic vesicle life cycle, clustering and mobility. Human molecular genetics 35 28973667
2012 Dg-Dys-Syn1 signaling in Drosophila regulates the microRNA profile. BMC cell biology 32 23107381
1997 Regional localization of two genes for nonspecific X-linked mental retardation to Xp22.3-p22.2 (MRX49) and Xp11.3-p11.21 (MRX50). American journal of medical genetics 24 9415477
2022 The different clinical facets of SYN1-related neurodevelopmental disorders. Frontiers in cell and developmental biology 22 36568968
2015 Efficient Synthesis of Differentiated syn-1,2-Diol Derivatives by Asymmetric Transfer Hydrogenation-Dynamic Kinetic Resolution of α-Alkoxy-Substituted β-Ketoesters. Chemistry (Weinheim an der Bergstrasse, Germany) 22 26139327
2019 miR‑134‑5p/Foxp2/Syn1 is involved in cognitive impairment in an early vascular dementia rat model. International journal of molecular medicine 19 31545395
2023 The Impact of BDNF, NTRK2, NGFR, CREB1, GSK3B, AKT, MAPK1, MTOR, PTEN, ARC, and SYN1 Genetic Polymorphisms in Antidepressant Treatment Response Phenotypes. International journal of molecular sciences 15 37047730
2013 Porcine synapsin 1: SYN1 gene analysis and functional characterization of the promoter. FEBS open bio 15 24251104
2021 Familial SYN1 variants related neurodevelopmental disorders in Asian pediatric patients. BMC medical genomics 10 34243774
2021 SYN1 Mutation Causes X-Linked Toothbrushing Epilepsy in a Chinese Family. Frontiers in neurology 10 34616357
2016 Expression profiling of RE1-silencing transcription factor (REST), REST corepressor 1 (RCOR1), and Synapsin 1 (SYN1) genes in human gliomas. Journal of B.U.ON. : official journal of the Balkan Union of Oncology 10 27685921
2018 Effects of SYN1Q555X mutation on cortical gray matter microstructure. Human brain mapping 8 29671924
2021 Low p-SYN1 (Ser-553) Expression Leads to Abnormal Neurotransmitter Release of GABA Induced by Up-Regulated Cdk5 after Microwave Exposure: Insights on Protection and Treatment of Microwave-Induced Cognitive Dysfunction. Current issues in molecular biology 7 35723394
2021 Multiparametric Evaluation of Post-MI Small Animal Models Using Metabolic ([18F]FDG) and Perfusion-Based (SYN1) Heart Viability Tracers. International journal of molecular sciences 6 34830471
2008 The non-neuronal syntaxin SYN-1 regulates defecation behavior and neural activity in C. elegans through interaction with the Munc13-like protein AEX-1. Biochemical and biophysical research communications 5 19028454
2024 Predictive Value of SYN-1 Levels for Mortality in Sepsis Patients in the Emergency Department. Journal of inflammation research 3 39618931
2024 SYN1 variant causes X-linked neurodevelopmental disorders: a case report of variable clinical phenotypes in siblings. Frontiers in neurology 2 38576531
2024 SP1-mediated SYN1 promotes hemin-induced damage in PC12 cells in vitro and exacerbates blood-barrier disruption and brain injury after intracerebral hemorrhage in vivo. Pathology, research and practice 2 39561537
2025 A Neuroprotective Peptide Modulates Retinal cAMP Response Element-Binding Protein (CREB), Synapsin I (SYN1), and Growth-Associated Protein 43 (GAP43) in Rats with Silicone Oil-Induced Ocular Hypertension. Biomolecules 1 40001522
2025 Treating seizures in SYN1-related epilepsy: a systematic review. Seizure 1 40554312