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synaptophysin

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">SYNAPTOPHYSIN (SYP)</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td><strong>SYP</strong></td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Synaptophysin</td>
</tr>
<tr>
<td class="label">Chromosome</td>
<td>Xp11.23</td>
</tr>
<tr>
<td class="label">NCBI Gene</td>
<td><a href="https://www.ncbi.nlm.nih.gov/gene/6855" target="_blank">6855</a></td>
</tr>
<tr>
<td class="label">Ensembl</td>
<td><a href="https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000100391" target="_blank">ENSG00000100391</a></td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/P21579" target="_blank">P21579</a></td>
</tr>
<tr>
<td class="label">Protein Length</td>
<td>316 amino acids</td>
</tr>
<tr>
<td class="label">Diseases</td>
<td>[Alzheimer's Disease](/diseases/alzheimers-disease), [Parkinson's Disease](/diseases/parkinsons-disease), Huntington's Disease, ALS</td>
</tr>
<tr>
<td class="label">Expression</td>
<td>Brain (cortex, hippocampus), cerebellum, retina, neuroendocrine cells</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/aging" style="color:#ef9a9a">Aging</a>, <a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">Alzheimer</a>, <a href="/wiki/dementia" style="color:#ef9a9a">Dementia</a></td>
</tr>

...

synaptophysin

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">SYNAPTOPHYSIN (SYP)</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td><strong>SYP</strong></td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Synaptophysin</td>
</tr>
<tr>
<td class="label">Chromosome</td>
<td>Xp11.23</td>
</tr>
<tr>
<td class="label">NCBI Gene</td>
<td><a href="https://www.ncbi.nlm.nih.gov/gene/6855" target="_blank">6855</a></td>
</tr>
<tr>
<td class="label">Ensembl</td>
<td><a href="https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000100391" target="_blank">ENSG00000100391</a></td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/P21579" target="_blank">P21579</a></td>
</tr>
<tr>
<td class="label">Protein Length</td>
<td>316 amino acids</td>
</tr>
<tr>
<td class="label">Diseases</td>
<td>[Alzheimer's Disease](/diseases/alzheimers-disease), [Parkinson's Disease](/diseases/parkinsons-disease), Huntington's Disease, ALS</td>
</tr>
<tr>
<td class="label">Expression</td>
<td>Brain (cortex, hippocampus), cerebellum, retina, neuroendocrine cells</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/aging" style="color:#ef9a9a">Aging</a>, <a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">Alzheimer</a>, <a href="/wiki/dementia" style="color:#ef9a9a">Dementia</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">197 edges</a></td>
</tr>
</table>

Pathway Diagram

Mermaid diagram (expand to render)

Introduction

Synaptophysin (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.

The SYP gene encodes Synaptophysin, a major synaptic vesicle glycoprotein essential for synaptic transmission.

Overview

SYNAPTOPHYSIN is a gene/protein encoding a key neuronal protein involved in synaptic function, signal transduction, and cellular homeostasis. Dysfunction of SYNAPTOPHYSIN is associated with neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, and related disorders.

Function

Synaptophysin is the most abundant synaptic vesicle membrane protein, constituting up to 10% of all synaptic vesicle proteins. It plays critical roles in:

Synaptic vesicle biogenesis and trafficking: Forms channels in synaptic vesicles that facilitate neurotransmitter release
Neurotransmitter release: Regulates the fusion of synaptic vesicles with the presynaptic membrane
Synapse formation: Essential for proper synaptic connectivity during development
Calcium sensing: Interacts with synaptogyrin to regulate synaptic vesicle exocytosis

Disease Associations

Alzheimer's Disease

Synaptophysin levels are significantly reduced in AD brains, correlating with cognitive decline
Loss of synaptophysin-positive terminals is a hallmark of early AD
Used as a biomarker for synaptic integrity in CSF

Parkinson's Disease

Decreased synaptophysin expression in the substantia nigra
Associated with dopaminergic neuron loss

Expression

High expression in:

Cerebral [cortex](/brain-regions/cortex) (especially layers II-III)
[Hippocampus](/brain-regions/hippocampus) (CA1-CA3 regions)
Cerebellum
Retina

Key Publications

Wiedenmann B, Franke WW (1985). Identification and localization of synaptophysin, an integral membrane glycoprotein of Mr 38,000 characteristic of presynaptic vesicles. Cell. PMID: 2578939(https://pubmed.ncbi.nlm.nih.gov/2578939/)
Calhoun ME et al. (1996). Comparative evaluation of synaptophysin-based immunohistochemistry and image analysis of [beta-amyloid](/proteins/amyloid-beta) in [entorhinal cortex](/brain-regions/entorhinal-cortex). J Neuropathol Exp Neurol. PMID: 8786408(https://pubmed.ncbi.nlm.nih.gov/8786408/)

Cross-links

[Neurons](entities/neurons)
[Synaptic Vesicle Cycling](mechanisms/synaptic-vesicle-trafficking-pathway)
[Alzheimer's Disease](diseases/alzheimers)
[Parkinson's Disease](diseases/parkinsons)

External Links

[NCBI Gene](https://www.ncbi.nlm.nih.gov/gene/) UniProt

Background

The study of Synaptophysin (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.

Structure and Function

Synaptophysin is a hexameric integral membrane protein of synaptic vesicles, encoded by the SYP gene located on chromosome Xp11.23[@bellen1993]. It is one of the most abundant synaptic vesicle proteins, comprising approximately 6-8% of the total vesicle protein pool[@wiedenmann1985]. The protein possesses four transmembrane domains and forms channels that facilitate neurotransmitter release through a mechanism involving vesicle fusion and recycling[@valtorta2018].

Molecular Characteristics

The human SYP gene spans approximately 5.5 kb and contains five exons. The protein product is 316 amino acids in length with a molecular weight of approximately 38 kDa[@leube1994]. Synaptophysin interacts with synaptobrevin (VAMP) in the synaptic vesicle release machinery, forming a essential component of the SNARE complex[@edwards2007].

Role in Synaptic Transmission

Synaptophysin plays a critical role in synaptic vesicle biogenesis, trafficking, and neurotransmitter release[@kwon2011]. It is involved in:

Vesicle formation: Essential for synaptic vesicle assembly
Neurotransmitter release: Modulates exocytosis through channel formation
Vesicle recycling: Facilitates endocytosis and vesicle reuse
Synaptic plasticity: Influences [long-term potentiation](/mechanisms/long-term-potentiation) and depression

Role in Neurodegenerative Diseases

Alzheimer's Disease

Synaptophysin is a key marker of synaptic integrity in Alzheimer's disease (AD)[@masliah1991]. In AD brains, significant reductions in synaptophysin immunoreactivity correlate with cognitive decline[@terry1991]. The loss of synaptophysin-positive synapses precedes overt neuron loss and correlates with memory impairment[@scheff1993]. Studies show that:

Synaptophysin levels are reduced by 25-45% in AD hippocampus
Early AD cases show synaptic loss in entorhinal cortex
CSF synaptophysin is being investigated as a biomarker[@brinkmalm2019]

Parkinson's Disease

In Parkinson's disease (PD), synaptophysin expression is altered in specific brain regions[@cheng2011]. Loss of dopaminergic nerve terminals in the striatum is associated with reduced synaptophysin immunoreactivity[@kordower2013]. The protein is also involved in [alpha-synuclein](/proteins/alpha-synuclein) aggregation pathways[@burr2013].

Other Neurodegenerative Conditions

Huntington's Disease: Reduced synaptophysin in striatal regions[@ferrante1991]
Frontotemporal Dementia: Variable changes depending on subtype[@neary1998]
Amyotrophic Lateral Sclerosis: Early synaptic dysfunction markers[@sikls1996]

Clinical Significance

Diagnostic Marker

Synaptophysin is widely used as an immunohistochemical marker for:

Neuroendocrine tumors (parathyroid, pituitary, gastrointestinal)
Synaptic integrity assessment in postmortem brain tissue
Research biomarker for synaptic function[@weyer2015]

Therapeutic Targets

Research into synaptophysin-based therapies includes:

Gene therapy approaches to restore synaptic function
Small molecules that enhance synaptophysin expression
Immunotherapy targeting synaptic proteins

Interacting Proteins and Pathways

Synaptophysin interacts with several key proteins involved in neurodegeneration[@gretenharrison2010]:

| Protein | Interaction Type | Relevance |
|---------|-----------------|-----------|
| Synaptobrevin/VAMP | SNARE complex | Neurotransmission |
| Alpha-synuclein | Co-aggregation | PD pathogenesis |
| [Amyloid precursor protein](/entities/app-protein) | Trafficking | AD mechanisms |
| CSPα | Chaperone complex | Synaptic protection |

Research Methods

Common experimental approaches include:

Immunohistochemistry: Postmortem brain tissue analysis
Western blotting: Protein level quantification
ELISA: CSF biomarker measurements
Live cell imaging: Vesicle dynamics studies

Synaptic Vesicle Biogenesis

Synaptophysin plays a critical role in synaptic vesicle biogenesis. As the most abundant synaptic vesicle protein, it constitutes 6-8% of total synaptic vesicle protein [20]. The protein:

Forms channels in the synaptic vesicle membrane
Participates in vesicle formation at the presynaptic terminal
Interacts with other synaptic vesicle proteins to form a functional vesicle

The formation of synaptic vesicles involves a complex process of membrane trafficking and protein sorting. Synaptophysin contains signals for synaptic vesicle targeting and is itself sorted into synaptic vesicles through interactions with the vesicle trafficking machinery [21].

Molecular Interactions

SNARE Complex

Synaptophysin interacts with key components of the synaptic vesicle release machinery:

| Interaction | Function |
|-------------|----------|
| Synaptobrevin/VAMP | Part of SNARE complex for fusion |
| SNAP-25 | SNARE partner |
| Syntaxin | SNARE partner |
| Synaptotagmin | Calcium sensor |

These interactions are essential for synaptic vesicle exocytosis [22].

Synaptogyrin

Synaptophysin interacts with synaptogyrin to:

Form heteromeric complexes in the vesicle membrane
Regulate synaptic vesicle exocytosis
Modulate vesicle dynamics

This interaction is important for proper synaptic vesicle function [21].

Alpha-Synuclein

Synaptophysin has a particularly important relationship with alpha-synuclein:

Both are enriched in presynaptic terminals
Alpha-synuclein can modulate synaptophysin function
Pathological interactions may contribute to Parkinson's disease [13]

Role in Neurodegenerative Diseases

Alzheimer's Disease

Synaptophysin is one of the most widely used markers for synaptic integrity in Alzheimer's disease research:

Pathological changes:

Synaptophysin levels reduced by 25-45% in AD hippocampus [9]
Loss precedes overt neuron loss
Correlates with cognitive decline severity
Early changes in entorhinal cortex [24]

Mechanisms:

Amyloid-beta toxicity affects synaptophysin function
Tau pathology disrupts synaptic vesicle trafficking
Both contribute to synaptic dysfunction

Biomarker potential:

CSF synaptophysin as a biomarker for synaptic loss [10]
Correlates with disease progression
Potential for early diagnosis

Parkinson's Disease

In Parkinson's disease, synaptophysin changes reflect the progressive loss of dopaminergic terminals:

Striatal changes:

Marked reduction in synaptophysin immunoreactivity in the striatum [11]
Loss correlates with disease severity [12]
Contributes to motor symptoms

Mechanisms:

Alpha-synuclein aggregation affects synaptic function
Mitochondrial dysfunction impacts synaptic vesicles
Dopamine toxicity to presynaptic terminals

Huntington's Disease

Synaptophysin changes in Huntington's disease:

Reduced synaptophysin in striatal regions [14]
Contributes to synaptic dysfunction
Correlates with motor and cognitive symptoms

Frontotemporal Dementia

In frontotemporal lobar degeneration:

Variable changes depending on subtype [15]
Synaptic loss is a key pathological feature
Different patterns from AD [25]

Amyotrophic Lateral Sclerosis

Synaptophysin in ALS:

Early synaptic dysfunction markers [16]
Changes in motor neuron synapses
May precede motor symptoms [26]

Clinical Applications

Diagnostic Marker

Synaptophysin is widely used as:

Neuroendocrine tumor marker: Diagnostic marker for tumors including:

Pheochromocytoma
Neuroblastoma
Small cell lung carcinoma
Pituitary tumors

Research marker: For studying synaptic integrity in:

Postmortem brain tissue
Animal models
Cell culture systems

Therapeutic Approaches

Research into synaptophysin-based therapies includes:

Gene therapy:

Viral vector-mediated synaptophysin expression
Promoting synaptic function in disease states

Small molecules:

Compounds that enhance synaptophysin expression
Synaptic function enhancers

Biomarker development:

CSF synaptophysin measurement [17]
Blood-based synaptic markers
Imaging of synaptic density

Research Methods

Experimental Techniques

| Method | Application |
|--------|-------------|
| Immunohistochemistry | Postmortem tissue analysis |
| Western blot | Protein quantification |
| ELISA | CSF biomarker measurement |
| Electron microscopy | Ultrastructural analysis |
| Live cell imaging | Vesicle dynamics |
| Proteomics | Global synaptic protein analysis |

Animal Models

Synaptophysin knockout mice show:

Reduced synaptic vesicle number
Impaired synaptic transmission
Compensatory changes in other proteins

These models are valuable for understanding synaptophysin function [18].

Synaptic Plasticity

Synaptophysin plays a role in synaptic plasticity:

Long-term potentiation (LTP):

Synaptophysin levels correlate with LTP
Modulates synaptic strength
Important for memory formation [4]

Long-term depression (LTD):

Involved in synaptic weakening
Regulated by synaptic activity
Contributes to circuit refinement

The protein's role in plasticity makes it relevant to learning and memory processes affected in neurodegenerative diseases.

Future Directions

Research Priorities

Biomarker validation: Further validation of CSF synaptophysin as a clinical biomarker

Therapeutic development: Finding ways to enhance synaptophysin function in disease

Mechanism studies: Deeper understanding of synaptophysin's role in disease pathogenesis

Imaging: Development of PET ligands for synaptic density

Emerging Approaches

Synaptic proteomics: Comprehensive analysis of synaptic changes
iPSC models: Patient-derived neurons for mechanistic studies
Gene editing: CRISPR approaches to modify synaptophysin expression
Combination therapies: Targeting multiple aspects of synaptic dysfunction

Conclusion

Synaptophysin (SYP) is a fundamental synaptic vesicle protein with critical roles in neurotransmitter release and synaptic function. Its significance in neurodegenerative diseases, particularly as a marker of synaptic loss, makes it an important focus for research into disease mechanisms and therapeutic interventions. The ongoing development of synaptophysin-based biomarkers and therapies holds promise for improving diagnosis and treatment of neurodegenerative conditions.

External Links

NCBI Gene: [https://www.ncbi.nlm.nih.gov/gene/6855](https://www.ncbi.nlm.nih.gov/gene/6855)
UniProt: [https://www.uniprot.org/uniprot/P21579](https://www.uniprot.org/uniprot/P21579)
Ensembl: [https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000100391](https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000100391)
Allen Brain Atlas: [https://human.brain-map.org/microarray/search/show?search_term=SYP](https://human.brain-map.org/microarray/search/show?search_term=SYP)

References

[Bellen HJ, et al. The synaptophysin gene family in Drosophila. EMBO J (1993)](https://pubmed.ncbi.nlm.nih.gov/8415632/)

[Wiedenmann B, Franke WW. Identification and localization of synaptophysin, an integral membrane glycoprotein. Cell (1985)](https://pubmed.ncbi.nlm.nih.gov/2994718/)

[Valtorta F, et al. Synaptophysin: leading actor or walk-on in the neuroendocrine tumor story? Endocr Relat Cancer (2018)](https://doi.org/10.1530/ERC-18-0055)

[Leube RE. Expression of the synaptophysin gene in neuronal and neuroendocrine cells. Cell Tissue Res (1994)](https://pubmed.ncbi.nlm.nih.gov/8004095/)

[Edwards RH. The neurotransmitter cycle and quantal size. Neuron (2007)](https://pubmed.ncbi.nlm.nih.gov/17646654/)

[Kwon SE, Chapman ER. Synaptophysin regulates the kinetics of synaptic vesicle endocytosis in central neurons. Neuron (2011)](https://pubmed.ncbi.nlm.nih.gov/21205207/)

[Masliah E, et al. Synaptic alterations in the entorhinal cortex in Alzheimer's disease. Ann Neurol (1991)](https://pubmed.ncbi.nlm.nih.gov/1833233/)

[Terry RD, et al. Synaptic loss is a major pathological feature in Alzheimer's disease. Prog Neuropsychopharmacol Biol Psychiatry (1991)](https://pubmed.ncbi.nlm.nih.gov/2016056/)

[Scheff SW, et al. Synapse loss in the temporal lobe in Alzheimer's disease. Ann Neurol (1993)](https://pubmed.ncbi.nlm.nih.gov/8415621/)

[Brinkmalm G, et al. Synaptic proteins in CSF as biomarkers for neurodegenerative disease. Nat Rev Neurol (2019)](https://pubmed.ncbi.nlm.nih.gov/30755016/)

[Cheng HC, et al. Loss of striatal dopaminergic nerve terminals in Parkinson's disease. Mov Disord (2011)](https://pubmed.ncbi.nlm.nih.gov/21407258/)

[Kordower JH, et al. Disease duration and the integrity of the nigrostriatal system in Parkinson's disease. Brain (2013)](https://pubmed.ncbi.nlm.nih.gov/23728387/)

[Burré J, et al. Properties of native brain α-synuclein. J Exp Med (2013)](https://pubmed.ncbi.nlm.nih.gov/24012066/)

[Ferrante RJ, et al. Neuropeptide Y, somatostatin, and synaptophysin in the striatum in Huntington's disease. Exp Neurol (1991)](https://pubmed.ncbi.nlm.nih.gov/1706321/)

[Neary D, et al. Frontotemporal lobar degeneration: a consensus on clinical diagnostic criteria. Neurology (1998)](https://pubmed.ncbi.nlm.nih.gov/9839343/)

[Siklós L, et al. Ultrastructural evidence for synaptophagy in motoneurons. J Neurosci Res (1996)](https://pubmed.ncbi.nlm.nih.gov/8824292/)

[Weyer G, et al. Cerebrospinal fluid markers for synaptic function in Alzheimer's disease. Alzheimers Dement (2015)](https://pubmed.ncbi.nlm.nih.gov/26282280/)

[Greten-Harrison B, et al. αβγ-Synuclein triple knockout mice reveal age-dependent neuronal dysfunction. Proc Natl Acad Sci U S A (2010)](https://pubmed.ncbi.nlm.nih.gov/21059569/)

[Takamori S, et al. Molecular anatomy of the synaptic vesicle. Nature (2006)](https://doi.org/10.1038/nature04753)

[Südhof TC. The synaptic vesicle cycle. Ann Rev Neurosci (2004)](https://doi.org/10.1146/annurev.neuro.26.041002.131445)

[Dormont D, et al. Synaptophysin and Alzheimer's disease. J Alzheimers Dis (2019)](https://doi.org/10.3233/JAD-190801)

[Chen X, et al. Synaptophysin in CSF as a biomarker for synaptotoxicity. Neurology (2018)](https://pubmed.ncbi.nlm.nih.gov/30482795/)

[Berchtold NC, et al. Synaptic genes in aging and Alzheimer's disease. Neurobiol Aging (2013)](https://doi.org/10.1016/j.neurobiolaging.2013.04.010)

[Petersen MA, et al. CSF synaptic proteins in neurodegenerative disease. Alzheimer's & Dementia (2019)](https://doi.org/10.1016/j.jalz.2019.02.012)

[Jackson J, et al. Synaptic changes in Parkinson's disease. Brain (2017)](https://doi.org/10.1093/brain/awx279)

[Calhoun ME, et al. Synaptophysin immunoreactivity in AD. J Neuropathol Exp Neurol (1996)](https://pubmed.ncbi.nlm.nih.gov/8786408/)

[Mass J, et al. Synaptophysin and synaptic biomarkers in FTD. Acta Neuropathol (2019)](https://doi.org/10.1007/s00401-019-01996-5)

[Kumar P, et al. Synaptic vesicle proteins in ALS. Mol Neurobiol (2018)](https://doi.org/10.1007/s12035-017-0849-8)

Pathway Diagram

The following diagram shows the key molecular relationships involving synaptophysin discovered through SciDEX knowledge graph analysis:

Mermaid diagram (expand to render)

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Related Entities

SYNAPTOPHYSIN

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slug	genes-synaptophysin
kg_node_id	SYNAPTOPHYSIN
entity_type	gene
origin_type	v1_polymorphic_backfill
source_table	wiki_pages
wiki_page_id	wp-95dd03fd8f8e
__merged_from	{'merged_at': '2026-05-13', 'unprefixed_id': 'genes-synaptophysin'}
_schema_version	1

📊 Evidence Profile Foundational

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Outgoing

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📗 Cite This Artifact

synaptophysin

synaptophysin

synaptophysin

Pathway Diagram

Introduction

Overview

Function

Disease Associations

Alzheimer's Disease

Parkinson's Disease

Expression

Key Publications

Cross-links

See Also

External Links

Background

Structure and Function

Molecular Characteristics

Role in Synaptic Transmission

Role in Neurodegenerative Diseases

Alzheimer's Disease

Parkinson's Disease

Other Neurodegenerative Conditions

Clinical Significance

Diagnostic Marker

Therapeutic Targets

Interacting Proteins and Pathways

Research Methods

Synaptic Vesicle Biogenesis

Molecular Interactions

SNARE Complex

Synaptogyrin

Alpha-Synuclein

Role in Neurodegenerative Diseases

Alzheimer's Disease

Parkinson's Disease

Huntington's Disease

Frontotemporal Dementia

Amyotrophic Lateral Sclerosis

Clinical Applications

Diagnostic Marker

Therapeutic Approaches

Research Methods

Experimental Techniques

Animal Models

Synaptic Plasticity

Future Directions

Research Priorities

Emerging Approaches

Conclusion

See Also

External Links

References

Pathway Diagram

💬 Discussion