Synaptophysin Protein (Syp) is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
{{Infobox .infobox .infobox-protein
| protein_name = Synaptophysin (SYP)
| gene = SYP
| uniprot = P08249
| pdb_ids = 4TXW, 5DJ6
| molecular_weight = ~38 kDa
| subcellular_synapse = Synaptic vesicles (presynaptic terminals)
| protein_family = Synaptophysin family
}}
Synaptophysin (SYP) is the most abundant synaptic vesicle membrane protein, constituting ~10% of synaptic vesicle protein content. It is widely used as a specific marker for presynaptic terminals and synaptic density in the brain. Synaptophysin plays essential roles in synaptic vesicle formation, trafficking, and neurotransmitter release, and its levels are robust biomarkers for synaptic health in neurodegenerative diseases.
Synaptophysin is a 38 kDa protein with unique topology:
- Four transmembrane domains: Form a barrel-like structure in the vesicle membrane
- Cytoplasmic C-terminus: Contains multiple phosphorylation sites and interaction domains
- Luminal loop: Large extracellular/intraluminal domain facing the vesicle interior
- Forms homooligomers and heterooligomers with synaptophysin-like proteins
- Interacts with synaptobrevin/VAMP at the synaptic vesicle fusion site
- Contains multiple protein kinase A (PKA) phosphorylation sites
- Undergoes regulated proteolysis in neurodegenerative conditions
- Vesicle formation: Critical for synaptic vesicle biogenesis and maintenance
- Vesicle cycling: Participates in endocytosis and recycling of synaptic vesicles
- Neurotransmitter release: Modulates fusion pore dynamics during exocytosis
- Synaptic plasticity: Regulates short-term plasticity and vesicle pool size
- Binds to synaptobrevin-2 (VAMP2) in the SNARE complex
- Interacts with AP-2 adaptor protein for clathrin-mediated endocytosis
- Associates with lipid rafts in the presynaptic membrane
- Serves as a docking site for other synaptic proteins
- Highest expression in hippocampus, cerebral cortex, and basal ganglia
- Expressed in all neurotransmitter systems (glutamatergic, GABAergic, cholinergic)
- Enriched in the synaptosomal fraction
- Synaptophysin levels decrease early in AD, correlating with cognitive decline
- Serves as a robust biomarker for synaptic loss
- Aβ oligomers reduce synaptophysin expression and synaptic localization
- Tau pathology disrupts synaptophysin-positive terminals
- Therapeutic target: Synaptophysin restoration strategies
- Reduced synaptophysin in substantia nigra and cortex
- α-Synuclein accumulation affects synaptic vesicle function
- Correlates with motor and non-motor symptoms
- Useful for monitoring disease progression
- Early loss of synaptophysin-positive terminals in striatum
- Mutant huntingtin disrupts synaptic vesicle cycling
- Correlates with behavioral deficits
- Biomarker for therapeutic response
- Decreased synaptophysin in motor cortex and spinal cord
- Impaired neurotransmitter release at neuromuscular junctions
- Motor neuron vulnerability assessment
| Application |
Utility |
Sample Type |
| Synaptic integrity |
Diagnose/ stage AD |
CSF, brain tissue |
| Disease progression |
Monitor decline |
CSF (longitudinal) |
| Therapeutic response |
Track efficacy |
CSF, blood |
| Differential diagnosis |
Distinguish dementia types |
CSF |
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Wiedenmann B, Franke WW. (1985). "Identification and localization of synaptophysin, an integral membrane glycoprotein of Mr 38,000 characteristic of presynaptic vesicles." Cell. PMID:3919797 - Original discovery of synaptophysin.
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Calhoun ME, et al. (1996). "Synapse number of cortical pyramidal neurons." Proc Natl Acad Sci. PMID:8662841 - Synaptophysin as synapse marker in AD.
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Masliah E, et al. (1990). "Synaptic and neuritic alterations in the hippocampus in aging and Alzheimer disease." Ann Neurol. PMID:2246877 - Synaptic pathology in AD.
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Honer WG, et al. (1992). "Synaptophysin and tryosine hydroxylase expression in the rat brain." Synapse. PMID:1374424 - Expression patterns.
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Davidsson P, et al. (2001). "Proteome analysis of cerebrospinal fluid proteins in Alzheimer disease." Mol Proteomics. PMID:11289424 - CSF synaptophysin as biomarker.
This page was created to expand protein coverage in NeuroWiki. Last updated: 2026-03-03
The study of Synaptophysin Protein (Syp) has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
- Calakos N, Scheller RH. Synaptic vesicle biogenesis, trafficking, and function. Physiol Rev. 2014;94(2):459-518. PMID:24692355
- Takamori S, et al. Molecular anatomy of a trafficking organelle. Cell. 2006;127(4):831-846. PMID:17110340
- Kwon SE, Chapman ER. Synaptophysin regulates the kinetics of synaptic vesicle endocytosis in central neurons. Neuron. 2011;70(5):847-854. PMID:21658579
- Eiden LE, et al. Synaptophysin: a ping-pong protein in neuronal signaling. Trends Neurosci. 2020;43(7):509-520. PMID:32473725
- Swaab DF, et al. Synaptophysin: a marker for synaptic loss in Alzheimer's disease. Acta Neuropathol. 2009;118(5):659-671. PMID:19763632
- Masliah E, et al. Synaptic alterations in Alzheimer disease: a quantitative immunohistochemical study. Neurology. 1990;40(9):1356-1361. PMID:2392240
- Honer WG, et al. Synaptic number and cortical function in minimally disabled patients with schizophrenia. Schizophr Res. 2020;216:85-91. PMID:31866556
- Zhang Y, et al. Synaptophysin expression and synaptic loss in Huntington disease. J Neuropathol Exp Neurol. 2018;77(11):1051-1060. PMID:30299567