CST3 (Cystatin C) Protein

CST3 (Cystatin C) Protein

Introduction

Cst3 (Cystatin C) 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"> [@alzheimers]
<h3>CST3 (Cystatin C) Protein</h3> [@nih]
<table>
<tr><th>Protein Name</th><td>Cystatin C</td></tr>
<tr><th>Gene</th><td>[CST3](/genes/cst3)</td></tr>
<tr><th>UniProt ID</th><td><a href="https://www.uniprot.org/uniprot/P01034" target="_blank">P01034</a></td></tr>
<tr><th>PDB ID</th><td>1G96, 3LXB, 4N8M</td></tr>
<tr><th>Molecular Weight</th><td>13.3 kDa</td></tr>
<tr><th>Subcellular Localization</th><td>Extracellular, Secreted</td></tr>
<tr><th>Protein Family</th><td>Cystatin family</td></tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
</div>

Structure

Cystatin C is a 13.3 kDa secreted cysteine protease inhibitor belonging to the type 2 cystatin family. The protein has a characteristic cystatin-like fold:

• N-terminal signal peptide for secretion
• Highly conserved N-terminal region required for protease inhibition
• Two hairpin loops that interact with target proteases
• Forms dimers and tetramers in solution

Normal Function

Cystatin C is a potent inhibitor of cysteine proteases including cathepsins B, H, L, and S:

CST3 (Cystatin C) Protein

Introduction

Cst3 (Cystatin C) 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"> [@alzheimers]
<h3>CST3 (Cystatin C) Protein</h3> [@nih]
<table>
<tr><th>Protein Name</th><td>Cystatin C</td></tr>
<tr><th>Gene</th><td>[CST3](/genes/cst3)</td></tr>
<tr><th>UniProt ID</th><td><a href="https://www.uniprot.org/uniprot/P01034" target="_blank">P01034</a></td></tr>
<tr><th>PDB ID</th><td>1G96, 3LXB, 4N8M</td></tr>
<tr><th>Molecular Weight</th><td>13.3 kDa</td></tr>
<tr><th>Subcellular Localization</th><td>Extracellular, Secreted</td></tr>
<tr><th>Protein Family</th><td>Cystatin family</td></tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
</div>

Structure

Cystatin C is a 13.3 kDa secreted cysteine protease inhibitor belonging to the type 2 cystatin family. The protein has a characteristic cystatin-like fold:

• N-terminal signal peptide for secretion
• Highly conserved N-terminal region required for protease inhibition
• Two hairpin loops that interact with target proteases
• Forms dimers and tetramers in solution

Normal Function

Cystatin C is a potent inhibitor of cysteine proteases including cathepsins B, H, L, and S:

Primary functions:

• Protease inhibition: Regulates cathepsin activity in extracellular spaces
• Antimicrobial defense: Part of the innate immune system
• Regulation of bone resorption: Modulates cathepsin K activity in osteoclasts
• Extracellular protein homeostasis

• Ubiquitously expressed
• High expression in brain ([neurons](/entities/neurons) and glia)
• Found in all body fluids

Neurodegeneration" style="color:#4fc3f7;margin:1.5rem 0 0.6rem;font-size:1.15rem;font-weight:700;border-bottom:2px solid rgba(79,195,247,0.3);padding-bottom:0.3rem">Role in Neurodegeneration

Alzheimer's Disease

• CST3 is a genetic risk factor for AD (protective variant A/A at position 42)
• The A allele produces less cystatin C and is associated with reduced AD risk
• Cystatin C co-localizes with amyloid plaques
• May modulate [Aβ](/proteins/amyloid-beta) aggregation
• Altered CSF levels in AD patients

Parkinson's Disease

• Cystatin C levels are altered in PD
• May protect against dopaminergic neuron loss
• Genetic variants associated with PD risk

Cerebral Amyloid Angiopathy

• Cystatin C deposits in cerebral vessels
• Hereditary cerebral amyloid angiopathy (Icelandic type) caused by CST3 mutation

Stroke" style="color:#e0e0e0;margin:1.2rem 0 0.5rem;font-size:1rem;font-weight:600;border-bottom:1px solid rgba(255,255,255,0.08);padding-bottom:0.3rem">Stroke

• CST3 is a biomarker for stroke risk
• Predictive of post-stroke outcomes

Therapeutic Targeting

Research Applications

• Cystatin C as a biomarker for neurodegenerative diseases
• Gene therapy approaches to modulate cystatin C levels

Key Publications

Background

The study of Cst3 (Cystatin C) 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.

Cross-references

• Gene: [CST3](genes/cst3)
• Diseases: [Alzheimer's Disease](diseases/alzheimers), [Parkinson's Disease](diseases/parkinsons), [Cerebral Amyloid Angiopathy](diseases/cerebral-amyloid-angiopathy)
• Pathways: [Protease Inhibition|Protease Inhibition], [Amyloid Plaque Formation|Amyloid Plaque Formation]

Overview

CST3 encodes Cystatin C, a cysteine protease inhibitor that plays important roles in protein regulation and has been implicated in Alzheimer's disease and cerebral amyloid angiopathy.

See Also

• Cystatin C - Protein overview
• Alzheimer Disease - AD disease
• Cerebral Amyloid Angiopathy - CAA
• Protease Inhibitors - Protein class

External Links

• [CST3 - NCBI Gene](https://www.ncbi.nlm.nih.gov/gene/1471)
• [Cystatin C - UniProt](https://www.uniprot.org/uniprot/P01019)

References