Synaptophysin Protein

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Synaptophysin Protein

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Synaptophysin Protein

Introduction

Synaptophysin Protein is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

<div class="infobox infobox-protein"> [@masliah1989]
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">Synaptophysin</th></tr>
<tr><td><strong>Protein Name</strong></td><td>Synaptophysin</td></tr>
<tr><td><strong>Gene</strong></td><td>[SYP](/genes/syp)</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[P08247](https://www.uniprot.org/uniprot/P08247)</td></tr>
<tr><td><strong>Protein Length</strong></td><td>313 amino acids</td></tr>
<tr><td><strong>Molecular Weight</strong></td><td>~38 kDa</td></tr>
<tr><td><strong>Subcellular Location</strong></td><td>Synaptic vesicle membrane</td></tr>
<tr><td><strong>Protein Family</strong></td><td>Synaptophysin family</td></tr>
<tr><td><strong>Associated Diseases</strong></td><td>Alzheimer's Disease, Parkinson's Disease, Epilepsy, Schizophrenia</td></tr>
</table>
</div>

Overview

...

Synaptophysin Protein

Introduction

Synaptophysin Protein is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

<div class="infobox infobox-protein"> [@masliah1989]
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">Synaptophysin</th></tr>
<tr><td><strong>Protein Name</strong></td><td>Synaptophysin</td></tr>
<tr><td><strong>Gene</strong></td><td>[SYP](/genes/syp)</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[P08247](https://www.uniprot.org/uniprot/P08247)</td></tr>
<tr><td><strong>Protein Length</strong></td><td>313 amino acids</td></tr>
<tr><td><strong>Molecular Weight</strong></td><td>~38 kDa</td></tr>
<tr><td><strong>Subcellular Location</strong></td><td>Synaptic vesicle membrane</td></tr>
<tr><td><strong>Protein Family</strong></td><td>Synaptophysin family</td></tr>
<tr><td><strong>Associated Diseases</strong></td><td>Alzheimer's Disease, Parkinson's Disease, Epilepsy, Schizophrenia</td></tr>
</table>
</div>

Overview

Synaptophysin (encoded by the SYP gene) is the most abundant integral membrane protein of synaptic vesicles, constituting approximately 6-8% of total synaptic vesicle protein content. As a founding member of the synaptophysin family, this protein serves as the gold standard marker for synaptic density and has been extensively utilized in neuropathology studies of neurodegenerative diseases[@wiedenmann1985]. Its universal presence in virtually all synaptic terminals makes it invaluable for assessing synaptic integrity in conditions ranging from Alzheimer's disease to epilepsy[@masliah1989].

Structure

Primary Structure

Length: 313 amino acids
Molecular weight: Approximately 38 kDa
Transmembrane domains: 4 hydrophobic regions

Topology

N-terminus: Cytoplasmic, contains phosphorylation sites
Transmembrane regions: Four transmembrane helices
C-terminus: Cytoplasmic, interacts with synaptic proteins

Quaternary Structure

Forms hexameric or heptameric channels
Creates a pore-like structure in synaptic vesicle membrane
Can form homo-oligomers

Post-Translational Modifications

Phosphorylation: Multiple serine residues (PKA, CaMKII sites)
Glycosylation: N-linked glycosylation in extracellular loops
Palmitoylation: Acyl chain modifications for membrane association

Molecular Function

Synaptic Vesicle Biology

As the major synaptic vesicle protein, synaptophysin participates in:

Vesicle Biogenesis

Critical for synaptic vesicle formation
Involved in vesicle maturation
Organizes vesicle protein composition

Vesicle Trafficking

Modulates synaptic vesicle recycling
Regulates endocytosis and exocytosis
Controls vesicle pool dynamics

Protein Interactions

SNARE Complex

Synaptobrevin-2/VAMP2: Direct interaction in SNARE complex
Syntaxin-1: Partner in synaptic fusion machinery
SNAP-25: Completes the SNARE complex

Calcium Sensing

Synaptotagmin-1: Calcium sensor for release
Coordinates fusion machinery with calcium influx

Other Partners

CSPα/DNAJC5: Chaperone for synaptic proteins
Hsc70: Heat shock protein involvement
AP-2: Clathrin adaptor in endocytosis

Normal Function in the Nervous System

Synaptic Transmission

Synaptophysin is essential for normal synaptic function:

Vesicle organization: Maintains synaptic vesicle pools

Release modulation: Regulates neurotransmitter release probability

Plasticity: Contributes to short-term and long-term plasticity

Homeostasis: Adapts to changing neural activity

Brain Region Distribution

Universal presynaptic marker across all brain regions
Highest density in: cerebral cortex, hippocampus, cerebellum
Expressed in both excitatory and inhibitory [neurons](/entities/neurons)

Role in Neurodegenerative Diseases

Alzheimer's Disease

Synaptophysin loss is a hallmark of AD:

[Hippocampus](/brain-regions/hippocampus): 30-50% reduction in AD vs. controls
[Cortex](/brain-regions/cortex): 20-40% reduction correlating with cognitive decline
[Entorhinal cortex](/brain-regions/entorhinal-cortex): Earliest synaptic loss in prodromal AD

Correlations:

Cognitive scores: MMSE, CDR correlations
Amyloid burden: Inverse correlation with plaque load
[Tau](/proteins/tau) pathology: Correlates with neurofibrillary tangles
Disease progression: MCI → AD transition marker[^3]

Parkinson's Disease

In PD and Lewy body diseases:

Loss of cortical synaptophysin in PD with dementia
Correlation with cognitive impairment severity
Early marker of terminal dysfunction
Dopaminergic terminal vulnerability

Epilepsy

Altered expression in epileptic foci
Marker of excitatory/inhibitory imbalance
Surgical target identification

Schizophrenia

Reduced synaptophysin in prefrontal cortex
Evidence for synaptic pathology
Correlates with cognitive deficits

Therapeutic Implications

Biomarker Applications

CSF Biomarker

Measures synaptic degeneration
Monitors disease progression
Treatment response biomarker

Neuroimaging

PET ligands for synaptic density (SV2A as proxy)
Correlates with cognitive function

Drug Development

Gene Therapy

SYP promoter-driven therapeutic expression
Viral vector approaches

Neuroprotective Strategies

Preserve synaptic terminals
Enhance synaptic function
Prevent synaptic loss

Research Directions

Biomarker validation: CSF synaptophysin clinical utility

Imaging: PET synaptic density ligands

Mechanism: Precise role in vesicle cycling

Therapy: Gene and cell-based approaches

Models: Transgenic and knockout studies

Animal Models

SYP knockout: Viable, subtle synaptic deficits
SYP overexpression: Enhanced plasticity and memory
AD models: Correlation with amyloid pathology

External Links

[UniProt: P08247](https://www.uniprot.org/uniprot/P08247)
[NCBI Protein: SYP](https://www.ncbi.nlm.nih.gov/protein/NP_003167.2)
[PDB: 1JX3](https://www.rcsb.org/structure/1JX3)
[Allen Brain Atlas: SYP](https://human.brain-map.org/microarray/search/show?search_term=SYP)

Background

The study of Synaptophysin Protein 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.

References

Wiedenmann B, Franke WW, Identification and localization of synaptophysin, an integral membrane glycoprotein of Mr 38,000 characteristic of presynaptic vesicles (1985)

Masliah E, Terry RD, DeTeresa R, Hansen LA, Immunohistochemical quantification of the synaptic marker synaptophysin in Alzheimer disease (1989)

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Related Entities

SYNAPTOPHYSINPROTEIN

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📊 Evidence Profile Foundational

Evidence Balance

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Certainty

100%

Debates

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Incoming

266

Outgoing

268

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📗 Cite This Artifact

Synaptophysin Protein

Synaptophysin Protein

Introduction

Overview

Synaptophysin Protein

Introduction

Overview

Structure

Primary Structure

Topology

Quaternary Structure

Post-Translational Modifications

Molecular Function

Synaptic Vesicle Biology

Vesicle Biogenesis

Vesicle Trafficking

Protein Interactions

SNARE Complex

Calcium Sensing

Other Partners

Normal Function in the Nervous System

Synaptic Transmission

Brain Region Distribution

Role in Neurodegenerative Diseases

Alzheimer's Disease

Parkinson's Disease

Epilepsy

Schizophrenia

Therapeutic Implications

Biomarker Applications

CSF Biomarker

Neuroimaging

Drug Development

Gene Therapy

Neuroprotective Strategies

Research Directions

Animal Models

See Also

External Links

Background

References

💬 Discussion