C5

C5

Introduction

```mermaid
flowchart TD
classDef gene fill:#0a1f0a,stroke:#4caf50
classDef protein fill:#0a1929,stroke:#2196f3
classDef disease fill:#2d0f0f,stroke:#e91e63
classDef pathway fill:#3e2200,stroke:#ff9800
classDef mechanism fill:#1a0a1f,stroke:#9c27b0
classDef therapeutic fill:#e0f2f1,stroke:#009688
C5["C5"] -->|"implicated_in"| neurodegeneration["neurodegeneration"]
C5["C5"] -->|"mediates"| Membrane_Attack_Complex_Stress["Membrane Attack Complex Stress"]
C5["C5"] -->|"co_discussed"| CR1["CR1"]
C5["C5"] -->|"involved_in"| Membrane_Attack_Complex["Membrane Attack Complex"]
C5["C5"] -->|"involved_in"| Membrane_Attack_Complex_Stress["Membrane Attack Complex Stress"]
C5["C5"] ==>|"upregulates"| Glaucoma["Glaucoma"]
C5["C5"] -->|"involved_in"| Glaucoma["Glaucoma"]
C5["C5"] -.->|"inhibits"| CD19["CD19"]
C5["C5"] -->|"participates_in"| complement_cascade["complement cascade"]
C5["C5"] -->|"causes"| CFB["CFB"]
C5["C5"] -->|"causes"| CLU["CLU"]
C5["C5"] -->|"causes"| CTSF["CTSF"]
C5["C5"] -->|"causes"| SMPD1["SMPD1"]
C5["C5"] ==>|"activates"| CR1["CR1"]
C5["C5"] -->|"expressed_in"| DAM_microglia["DAM microglia"]
C5["C5"] -->|"participates_in"| blood_brain_barrier["blood-brain barrier"]
C5["C5"] -->|"participates_in"| ubiquitin_proteasome["ubiquitin-proteasome"]
C5["C5"] ==>|"activates"| Membrane_Attack_Complex_Formation["Membrane Attack Complex Formation"]
C3["C3"] -->|"co_discussed"| C5["C5"]
C1Q["C1Q"] -->|"co_discussed"| C5["C5"]
AQP4["AQP4"] -.->|"inhibit

C5

Introduction

C5 encodes the complement component 5, a critical protein in the [complement system](/entities/complement-system). C5 is cleaved into C5a (anaphylatoxin) and C5b, initiating the terminal complement pathway and membrane attack complex (MAC) formation. C5 plays a dual role in immune defense and inflammatory responses, with significant implications for neuroinflammation and neurodegenerative diseases. [@woodruff2011]

<div class="infobox infobox-gene"> [@pasinetti2012]
<table> [@brenner2013]
<tr><th colspan="2" style="background:#1a5f7a;color:white;">C5</th></tr>
</table>
</div>

Overview

The C5 gene encodes a component of the complement system, part of the innate immune system involved in inflammation and immune response.

<div class="infobox infobox-gene">
<div class="infobox-header">Complement Component 5</div>
<div class="infobox-row"><span class="infobox-label">Gene Symbol</span><span class="infobox-value">C5</span></div>
<div class="infobox-row"><span class="infobox-label">Full Name</span><span class="infobox-value">Complement Component 5</span></div>
<div class="infobox-row"><span class="infobox-label">Chromosomal Location</span><span class="infobox-value">9q33.2</span></div>
<div class="infobox-row"><span class="infobox-label">NCBI Gene ID</span><span class="infobox-value">[727](https://www.ncbi.nlm.nih.gov/gene/727)</span></div>
<div class="infobox-row"><span class="infobox-label">OMIM</span><span class="infobox-value">[120900](https://omim.org/entry/120900)</span></div>
<div class="infobox-row"><span class="infobox-label">Ensembl ID</span><span class="infobox-value">ENSG00000102755</span></div>
<div class="infobox-row"><span class="infobox-label">UniProt ID</span><span class="infobox-value">[P01031](https://www.uniprot.org/uniprot/P01031)</span></div>
<div class="infobox-row"><span class="infobox-label">Associated Diseases</span><span class="infobox-value">Age-Related Macular Degeneration, Huntington's Disease, Complement Deficiency</span></div>
</div>

Function

The C5 gene encodes complement component 5, a critical protein in the complement system. C5 is synthesized as a single polypeptide chain and is proteolytically cleaved into two functional fragments:

• C5a: A potent anaphylatoxin and pro-inflammatory mediator
• C5b: The initiating fragment for formation of the membrane attack complex (MAC)

Disease Associations

Neurodegenerative Disease Links

• [Alzheimer's Disease](/diseases/alzheimers-disease): C5a receptors are upregulated in AD brain, and C5a contributes to neuroinflammation and microglial activation. C5a/C5aR1 signaling promotes [amyloid-beta](/proteins/amyloid-beta) induced inflammation.
• [Parkinson's Disease](/diseases/parkinsons-disease): C5a is implicated in neuroinflammation in the substantia nigra and contributes to dopaminergic neuron degeneration.
• Huntington's Disease: Elevated C5a levels have been observed in HD models and may contribute to disease progression.
• Amyotrophic Lateral Sclerosis: Complement activation, including C5, is involved in the inflammatory response in ALS.
• Age-Related Macular Degeneration: Genetic variants in the C5 gene are associated with AMD risk.

Therapeutic Implications

• C5a receptor antagonists are being investigated as potential therapies for neuroinflammatory conditions.
• Eculizumab and ravulizumab (C5 inhibitors) are used for complement-mediated diseases and may have potential in neurodegenerative conditions.

Expression

C5 is expressed in various tissues:

• Brain: Synthesized by [neurons](/entities/neurons), [astrocytes](/entities/astrocytes), and [microglia](/cell-types/microglia-neuroinflammation). C5a receptors (C5AR1, C5AR2) are expressed in the brain.
• Liver: Primary site of complement protein synthesis
• Immune cells: Macrophages, neutrophils, monocytes

Background

The study of C5 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

• Complement System
• [Neuroinflammation](/mechanisms/neuroinflammation) [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• C6
• C7
• Complement- [Neuroinflammation](/mechanisms/neuroinflammation)ne System
• [Neuroinflammation](/mechanisms/neuroinflammation) [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)

External Links

• [NCBI Gene](https://www.ncbi.nlm.nih.gov/gene)
• [UniProt](https://www.uniprot.org)
• [OMIM](https://www.omim.org)

References

Pathway Diagram

The following diagram shows the key molecular relationships involving C5 discovered through SciDEX knowledge graph analysis: