CD55

CD55

Overview

```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
CD55["CD55"] -->|"implicated_in"| neurodegeneration["neurodegeneration"]
CD55["CD55"] ==>|"activates"| CD59["CD59"]
CD55["CD55"] ==>|"activates"| STAT3["STAT3"]
CD55["CD55"] ==>|"activates"| RNA["RNA"]
CD55["CD55"] -->|"regulates"| CD59["CD59"]
CD55["CD55"] -->|"participates_in"| complement_cascade["complement cascade"]
CD55["CD55"] -->|"expressed_in"| neurons["neurons"]
CD55["CD55"] -.->|"inhibits"| CD59["CD59"]
CD55["CD55"] ==>|"activates"| IDE["IDE"]
CD55["CD55"] ==>|"activates"| JAK2["JAK2"]
CD55["CD55"] -->|"participates_in"| JAK_STAT_signaling["JAK-STAT signaling"]
CD55["CD55"] -->|"participates_in"| NF_kB_signaling["NF-kB signaling"]
CD55["CD55"] ==>|"activates"| CFH["CFH"]
CD55["CD55"] ==>|"activates"| LIMK1["LIMK1"]
CD55["CD55"] ==>|"activates"| ROCK1["ROCK1"]
CD55["CD55"] -->|"participates_in"| unfolded_protein_response["unfolded protein response"]
CD55["CD55"] -->|"expressed_in"| astrocytes["astrocytes"]
C4B["C4B"] -->|"regulated_by"| CD55["CD55"]
C1QA["C1QA"] ==>|"activates"| CD55["CD55"]
C4B["C4B"] ==>|"activates"| CD55["CD55"]
CD46["CD46"] ==>|"activates"| CD55["CD55"]
CD46["CD46"] -->|"regulates"| CD55["CD55"]
C3["C3"] -.->|"inhibits"

CD55

Overview

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">CD55</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td><strong>CD55</strong></td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>CD55</td>
</tr>
<tr>
<td class="label">Type</td>
<td>Gene</td>
</tr>
<tr>
<td class="label">NCBI</td>
<td><a href="https://www.ncbi.nlm.nih.gov/gene/?term=CD55" target="_blank">Search NCBI</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">2 edges</a></td>
</tr>
</table>

CD55 (Cluster of Differentiation 55, also known as Decay-Accelerating Factor or DAF) is a cell surface protein encoded by the CD55 gene located on chromosome 1q32.2. CD55 is a key regulator of complement activation and also plays important roles in cell adhesion, signal transduction, and neuroprotection. Recent research has revealed that CD55 is increasingly recognized for its involvement in neurodegenerative diseases, particularly Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS).

Gene and Protein Structure

The CD55 gene spans approximately 40 kb and consists of 11 exons encoding a 381-amino-acid protein[@lublin1989]. CD55 is a glycosylphosphatidylinositol (GPI)-anchored protein that belongs to the regulators of complement activation (RCA) family[@lublin1989]. The protein structure includes:

• Four short consensus repeat (SCR) domains
• A serine/threonine-rich region (O-glycosylated)
• A GPI anchor for membrane attachment

Normal Physiological Function

Complement Regulation

CD55's primary function is to protect cells from complement-mediated lysis by accelerating the decay of C3/C5 convertases[@lublin1989]. This prevents unwanted tissue damage during immune responses.

Cell Adhesion and Signaling

CD55 participates in cell-cell adhesion processes and can trigger intracellular signaling cascades upon ligand binding or cross-linking[@miyamoto2018]. It interacts with various signaling molecules and influences cellular responses.

T Cell Activation

CD55 is expressed on T cells and regulates their activation threshold, contributing to immune homeostasis[@miyamoto2018].

Role in Neurodegeneration

Alzheimer's Disease

In Alzheimer's disease, CD55 has been implicated through several mechanisms[@zhang2019][@stambulic2021]:

Parkinson's Disease

In Parkinson's disease, CD55 involvement has been studied[@depboylu2012]:

Multiple Sclerosis

CD55 has been extensively studied in multiple sclerosis[@rus2001]:

Expression Patterns

CD55 is widely expressed in human tissues:

• Hematopoietic cells (T cells, B cells, monocytes)
• Endothelial cells
• Epithelial cells
• Neurons and glia in the brain
• Peripheral nerves

Therapeutic Implications

CD55-based therapeutic strategies are being developed for neurodegenerative diseases[@morgan2016]:

Key Research Findings

• CD55 is significantly decreased in AD brain tissue, particularly in regions vulnerable to neurodegeneration[@zhang2019].
• Genetic polymorphisms in CD55 have been associated with susceptibility to AD and PD in some populations[@may2020].
• CD55 overexpression protects against complement-mediated neurotoxicity in cellular models[@depboylu2012].
• CSF levels of soluble CD55 are altered in AD and PD patients, suggesting potential biomarker utility[@stambulic2021].

Summary

CD55 is a complement regulatory protein with important functions in immune regulation, cell adhesion, and neuroprotection. Its dysfunction contributes to neurodegeneration through complement-mediated synaptic loss, neuroinflammation, and blood-brain barrier impairment. CD55 represents a promising therapeutic target for neurodegenerative diseases, with several approaches in development.

See Also

• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)

External Links

• [PubMed](https://pubmed.ncbi.nlm.nih.gov/)
• [KEGG Pathways](https://www.genome.jp/kegg/pathway.html)

References

Pathway Diagram

The following diagram shows the key molecular relationships involving CD55 discovered through SciDEX knowledge graph analysis: