CD200R1 (CD200 Receptor 1) encodes the receptor for CD200 (OX-2), a membrane glycoprotein expressed on various cell types including neurons and astrocytes. CD200R1 is primarily expressed on microglia, macrophages, and other myeloid cells, where it transduces inhibitory signals upon engagement with CD200. This receptor-ligand pair forms a crucial immune regulatory pathway that maintains microglial quiescence and prevents excessive neuroinflammation in the healthy brain.
CD200R1 is a member of the immunoglobulin superfamily and contains immunoreceptor tyrosine-based inhibition motifs (ITIMs) in its cytoplasmic domain. Upon CD200 binding, CD200R1 recruits phosphatases (SHP-1 and SHP-2) that counteract activation signals in microglia, thereby suppressing pro-inflammatory cytokine production and phagocytic activity. Dysregulation of this pathway contributes to chronic neuroinflammation in neurodegenerative diseases.
| Property |
Value |
| Gene Symbol |
CD200R1 |
| Protein |
CD200 receptor 1 |
| Synonyms |
MOX2, CD200R, OX2R |
| Chromosomal Location |
3q13.2 (human) |
| NCBI Gene ID |
13190 |
| UniProt ID |
Q9Y5U5 (human) |
| Gene Family |
Immunoglobulin superfamily |
| Protein Length |
502 amino acids |
| Molecular Weight |
~60 kDa |
The CD200R1 receptor transduces inhibitory signals:
CD200 (on neurons/astrocytes)
↓
Binds CD200R1
↓
(on microglia)
↓
ITIM phosphorylation
↓
SHP-1/SHP-2 recruitment
↓
Phosphatase activation
↓
↓ inflammatory signaling
↓
Microglial quiescence
CD200R1 signaling involves:
- ITIM motifs: Two ITIMs in cytoplasmic domain
- Phosphatase recruitment: SHP-1 and SHP-2 binding
- Kinase inhibition: Counteracts activation pathways
- Cytokine suppression: Reduces pro-inflammatory mediator production
CD200R1 is primarily expressed on:
- Microglia: Highest expression in brain
- Macrophages: Peripheral immune cells
- Dendritic cells: Antigen-presenting cells
- Neutrophils: Some expression
- T cells: Subset of T cells
- Immune homeostasis: Maintains myeloid cell quiescence
- Inflammation regulation: Controls inflammatory responses
- Self-tolerance: Prevents autoimmunity
- Tissue protection: Limits tissue damage from inflammation
CD200R1 dysfunction contributes to AD pathogenesis:
- Loss of inhibition: Reduced CD200R1 signaling leads to microglial activation
- Pro-inflammatory state: Chronic production of inflammatory cytokines
- Aβ clearance: Impaired phagocytic function
- Synaptic loss: Contributes to synapse elimination
- CD200R1 agonists: Enhance inhibitory signaling
- Gene therapy: Increase CD200R1 expression
- Small molecule activators: Receptor modulators
CD200R1 plays protective roles in PD:
- Microglial quiescence: Maintaining microglial quiet state
- Neuroprotection: Protecting dopaminergic neurons
- Neuroinflammation reduction: Reducing chronic inflammation
- Alpha-synuclein clearance: Improving microglial function
- Agonist development: CD200R1 agonist antibodies
- Gene therapy: Viral vector approaches
- Neuroprotection: Protecting against neuroinflammation
- Motor neuron interactions: CD200R1 on microglia
- Disease progression: Contributes to progression
- Therapeutic target: CD200R1-based approaches
- Demyelination: Role in demyelinating diseases
- Microglial control: Limits demyelination damage
- Therapeutic potential: CD200R1 modulation
| Component |
Function |
| ITIM |
Phosphotyrosine motif |
| SHP-1 |
Phosphatase recruitment |
| SHP-2 |
Negative regulation |
| PI3K |
Survival signaling |
| MAPK inhibition |
Reduced activation |
- Extracellular domain: IgV-like ligand binding domain
- Transmembrane domain: Single pass
- Cytoplasmic domain: Contains ITIMs
- SHP binding sites: Phosphatase recruitment motifs
| Partner |
Interaction |
Effect |
| CD200 |
Ligand binding |
Activation |
| SHP-1 |
ITIM binding |
Phosphatase |
| SHP-2 |
ITIM binding |
Phosphatase |
| PILRα |
Protein interaction |
Co-receptor |
| Approach |
Development Stage |
Description |
| Agonist antibodies |
Preclinical |
CD200R1 activation |
| Gene therapy |
Preclinical |
Expression enhancement |
| Small molecules |
Research |
Receptor modulators |
| Cell therapy |
Research |
Myeloid cell approaches |
- Agonist antibodies show efficacy
- Gene therapy approaches tested in models
- Combination with anti-inflammatory therapies
- No CD200R1-targeted therapies in clinical trials
- Immune checkpoint modulation in oncology
- Potential for neurodegenerative diseases
- CRISPR-Cas9: CD200R1 knockout
- Antibodies: Agonist and antagonist
- Recombinant CD200: Ligand for receptor studies
- Fluorescent reporters: Expression tracking
- CD200R1 knockout mice: Complete loss
- Transgenic models: Overexpression
- Disease models: AD, PD, MS models
- Flow cytometry: Receptor expression
- Immunohistochemistry: Brain localization
- Cytokine analysis: Inflammatory markers
- Behavior: Functional testing
- Human: Full-length CD200R1
- Mouse: High conservation
- Rat: Similar structure
- Evolution: Immune regulatory function conserved
The CD200R family shows complex evolution:
Gene Family Expansion:
- Humans: CD200R1, CD200R2, CD200R3, CD200R4, CD200R5
- Mice: Multiple paralogs
- Functional diversification in different species
Ortholog Relationships:
- CD200R1 is most conserved across species
- Species-specific duplications in rodents
- Loss in some vertebrate lineages
CD200R1 expression is epigenetically controlled:
- Promoter methylation: Inversely correlates with expression
- Cell-type specificity: Differential patterns in myeloid cells
- Disease states: Altered patterns in neurodegeneration
- Environmental influence: Epigenetic plasticity
Chromatin states regulate CD200R1:
- H3K27ac marks: Active enhancers in microglia
- H3K4me1: Permissive enhancer marks
- H3K9me3: Repressive marks in non-immune cells
Transcription factors affecting CD200R1:
- PU.1: Master regulator in myeloid cells
- IRF8: Interferon response factor
- C/EBPβ: CCAAT enhancer binding protein
¶ Protein Domain Architecture
CD200R1 contains multiple functional domains:
Extracellular Region:
- IgV-like domain (N-terminal): High-affinity CD200 binding
- IgSF domain 2: Dimerization interface
- IgSF domain 3: Stabilizing domain
- Mucin-like region: Provides structural flexibility
Transmembrane Region:
- Single-pass α-helical transmembrane domain
- Lipid raft association motif
Intracellular Region:
- ITIM 1: Phosphotyrosine recruitment
- ITIM 2: Extended inhibitory signaling
- C-terminal tail: Localization signals
The extracellular domain structure reveals:
- IgV fold: Typical immunoglobulin topology
- CD200 binding pocket: Hydrophobic interface
- Dimerization interface: Mediates receptor clustering
- Glycosylation sites: N-linked carbohydrates
Ligand-induced changes:
- Receptor dimerization upon CD200 binding
- Extracellular domain rearrangement
- ITIM phosphorylation cascade
- Signaling complex assembly
The canonical inhibitory pathway:
- CD200 engagement: Binds extracellular IgV domain
- Receptor clustering: Induces dimer formation
- ITIM phosphorylation: Src family kinases not required
- SHP recruitment: Binds phosphorylated ITIMs
- Phosphatase activation: Dephosphorylates activation substrates
- Signaling inhibition: Blocks downstream activation
Non-ITIM pathways:
- TRAF-independent signaling: Alternative adapters
- Cross-talk with other receptors: Integrates with activation signals
- Cell type-specific effects: Myeloid cell variations
Transcriptional outcomes:
- Reduced inflammatory gene expression
- Altered cytokine profiles
- Modulated phagocytic activity
Cellular consequences:
- Inhibited ROS production
- Reduced nitric oxide synthesis
- Suppressed matrix metalloproteinases
Agonist Development:
| Agent Type |
Stage |
Advantages |
Limitations |
| Agonist antibodies |
Preclinical |
High affinity |
BBB penetration |
| CD200-Fc |
Preclinical |
Natural ligand |
Immunogenicity |
| Small molecules |
Research |
Oral bioavailability |
Selectivity |
| Peptide mimetics |
Research |
Brain penetration |
Stability |
Current status:
- No active clinical trials for neurodegeneration
- Oncology applications: CD200R1 antagonists in cancer
- Autoimmune disease: Investigational in preclinical
Potential biomarkers:
- CD200R1 expression: On circulating monocytes
- Soluble CD200: CSF levels
- Genetic variants: SNPs in CD200R1 gene
- Inflammatory profiles: Baseline cytokine levels
| Model |
Genetic Background |
Phenotype |
Use |
| CD200R1 KO |
C57BL/6 |
Spontaneous activation |
Basic research |
| CD200R1 tg |
C57BL/6 |
Suppressed activation |
Therapy testing |
| CD200R1 flox |
C57BL/6 |
Conditional KO |
Cell-type specific |
| CD200R1 reporter |
Multiple |
LacZ/EGFP expression |
Expression mapping |
Alzheimer's Disease:
- 5×FAD × CD200R1 KO: Accelerated pathology
- APP/PS1 × CD200R1 agonist: Protected phenotype
Parkinson's Disease:
- MPTP × CD200R1 KO: Exacerbated loss
- α-Syn × CD200R1 agonist: Reduced pathology
Behavioral and pathological assessment:
- Microglial morphology: Iba1 staining quantification
- Cytokine levels: IL-1β, TNF-α, IL-6 measurement
- Cognitive testing: Morris water maze, novel object recognition
- Motor testing: Rotarod, cylinder test
CD200R1 intersects multiple networks:
CD200R1 Signaling Network
┌─────────────┐
│ MAPK │
│ Inhibition│
└──────┬──────┘
│
┌──────────┐ ┌────────▼────────┐
│ SHP-1 │──────▶│ Inflammatory │
│ SHP-2 │ │ Suppression │
└────┬─────┘ └────────▲────────┘
│ │
│ ┌────────┴────────┐
│ │ │
▼ ▼ ▼
┌─────────────────┐ ┌──────────┐ ┌─────────────┐
│ ITIM Signaling │ │Cytokine │ │ Phagocytosis│
│ │ │Reduction │ │ Inhibition │
└─────────────────┘ └──────────┘ └─────────────┘
│
▼
┌─────────────────┐
│ NF-κB │
│ Suppression │
└─────────────────┘
CD200R1 interactome includes:
- Toll-like receptors: TLR2, TLR4 cross-talk
- Complement receptors: CR3, CR4 integration
- Fc receptors: γ-chain involvement
- Other ITIM receptors: Coordinated regulation
- Brain delivery: CNS-targeting approaches
- Selective agonists: Specific receptor activation
- Biomarkers: Patient selection
- Clinical translation: Safe candidates
- Gene therapy: AAV delivery
- Cell therapy: Engrafted cells
- Biomarkers: Inflammatory markers
- Personalized approaches: Genetic markers
- Structural studies: Full CD200/CD200R1 complex
- Functional validation: Human microglia models
- Clinical development: Safe therapeutic candidates
- Biomarkers: Patient stratification markers