CCR5 Protein

CCR5 Protein

Overview

CCR5 (C-C chemokine receptor type 5) is a G protein-coupled receptor that binds multiple chemokines, particularly CCL3 (MIP-1α), CCL4 (MIP-1β), and CCL5 (RANTES). Originally characterized for its role as the major co-receptor for HIV-1 entry into host cells, CCR5 has emerged as a critical regulator of neuroinflammation, synaptic plasticity, and cognitive function in the central nervous system [@zhang2005].

CCR5 Protein

Overview

CCR5 (C-C chemokine receptor type 5) is a G protein-coupled receptor that binds multiple chemokines, particularly CCL3 (MIP-1α), CCL4 (MIP-1β), and CCL5 (RANTES). Originally characterized for its role as the major co-receptor for HIV-1 entry into host cells, CCR5 has emerged as a critical regulator of neuroinflammation, synaptic plasticity, and cognitive function in the central nervous system [@zhang2005].

<div class="infobox infobox-protein">
<table>
<tr><th colspan="2"><strong>CCR5</strong></th></tr>
<tr><td><strong>Full Name</strong></td><td>C-C chemokine receptor type 5</td></tr>
<tr><td><strong>Gene</strong></td><td>CCR5</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[P51681](https://www.uniprot.org/uniprot/P51681)</td></tr>
<tr><td><strong>Protein Size</strong></td><td>352 amino acids</td></tr>
<tr><td><strong>Protein Family</strong></td><td>G protein-coupled receptor, chemokine receptor family</td></tr>
<tr><td><strong>Chromosomal Location</strong></td><td>3p21.31</td></tr>
<tr><td><strong>Subcellular Location</strong></td><td>Cell membrane, lipid rafts</td></tr>
<tr><td><strong>Associated Disease</strong></td><td>Alzheimer's Disease, Parkinson's Disease, HIV-associated neurocognitive disorder</td>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/autoimmune" style="color:#ef9a9a">Autoimmune</a>, <a href="/wiki/cancer" style="color:#ef9a9a">Cancer</a>, <a href="/wiki/cardiovascular" style="color:#ef9a9a">Cardiovascular</a>, <a href="/wiki/dementia" style="color:#ef9a9a">Dementia</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">109 edges</a></td>
</tr>
</table>
</div>

Structure

Receptor Architecture

CCR5 is a seven-transmembrane G protein-coupled receptor (GPCR) with the following structural features:

• N-terminal extracellular domain: Contains glycosylation sites and contributes to ligand binding specificity
• Extracellular loops (ECL1-3): Form the ligand-binding pocket for chemokines
• Transmembrane domains (TM1-7): Spanning the cell membrane, connecting to intracellular signaling
• Intracellular loops (ICL1-3): Couple to G proteins and β-arrestin
• C-terminal intracellular tail: Contains serine/threonine residues for phosphorylation and regulation

Structural Highlights

• Δ32 mutation: A 32-base pair deletion in the CCR5 gene (CCR5-Δ32) creates a non-functional receptor, providing natural resistance to HIV infection in homozygotes. This mutation has been associated with altered disease risk in neurodegenerative conditions [@kuo2020].
• Ligand binding: CCR5 can bind multiple chemokines with different affinities, enabling context-dependent signaling.
• Dimerization: CCR5 can form homodimers and heterodimers with other chemokine receptors, modulating its function.

Normal Function

Chemokine Signaling

In the central nervous system, CCR5 is expressed on multiple cell types:

• Microglia: The primary immune cells of the brain, expressing high levels of CCR5 [@li2021]
• Neurons: Express CCR5 at lower levels, where it modulates synaptic activity
• Astrocytes: Can express CCR5 in response to inflammatory signals
• Endothelial cells: CCR5 regulates leukocyte trafficking across the blood-brain barrier

Key Signaling Pathways

CCR5 activates multiple intracellular signaling cascades:

Physiological Roles

• Neuroinflammation regulation: Controls microglial activation and cytokine production
• Synaptic plasticity: Modulates long-term potentiation (LTP) and memory formation [@marin2023]
• Neurogenesis: Influences adult hippocampal neurogenesis [@hernandez2023]
• Cell migration: Guides immune cell recruitment to sites of injury or infection

Role in Alzheimer's Disease

Neuroinflammation

CCR5 plays a dual role in Alzheimer's disease neuroinflammation [@bhatt2015]:

• Pro-inflammatory effects: CCR5 activation on microglia promotes production of pro-inflammatory cytokines (IL-1β, TNF-α, IL-6), contributing to chronic neuroinflammation.
• Aβ clearance: CCR5 signaling modulates microglial phagocytosis of amyloid-beta plaques [@kong2024].
• Neurotoxicity: Excessive CCR5 signaling can lead to excitotoxicity and neuronal death.

Genetic Associations

Multiple studies have investigated CCR5 genetic variants in AD risk:

• Promoter polymorphisms: Certain CCR5 promoter variants have been associated with altered AD risk in specific populations [@galimberti2020].
• Δ32 mutation: The protective CCR5-Δ32 variant has shown inconsistent associations with AD risk, with some studies suggesting protection and others showing no effect [@kuo2020].
• Clinical outcomes: CCR5 genetic variants may influence disease progression and clinical outcomes in AD patients [@wu2023].

Therapeutic Targeting

CCR5 antagonists have shown promise in AD models:

• Maraviroc: The FDA-approved HIV drug has demonstrated neuroprotective effects in preclinical AD models [@wang2024].
• Mechanism: Blocking CCR5 reduces microglial activation, decreases neuroinflammation, and improves memory deficits.
• Tau pathology: CCR5 antagonists may reduce tau pathology through modulation of inflammatory pathways [@chen2024].

Role in Parkinson's Disease

Genetic Association

Several studies have linked CCR5 genetic variants to PD risk and progression:

• PD risk: Certain CCR5 haplotypes have been associated with altered PD susceptibility [@zhou2022].
• Disease progression: CCR5 genetic variants may influence motor and non-motor symptom progression [@xie2023].
• Expression studies: Increased CCR5 expression has been observed in PD patient brains [@liu2024].

Neuroinflammation

CCR5 contributes to PD-related neuroinflammation through multiple mechanisms:

• Microglial activation: CCR5 mediates microglial recruitment and activation in the substantia nigra.
• Dopaminergic neuron toxicity: CCR5 signaling promotes inflammatory responses that damage dopaminergic neurons.
• α-Synuclein interaction: CCR5 may influence α-synuclein aggregation and toxicity [@hu2023].

Therapeutic Implications

Targeting CCR5 in PD shows therapeutic potential:

• Neuroprotection: CCR5 blockade protects dopaminergic neurons from inflammation-induced death [@park2024].
• Motor improvement: CCR5 antagonists may improve motor symptoms in PD models.
• Combination therapy: CCR5 targeting may complement other neuroprotective strategies.

CCR5 and Aging

Cognitive Decline

CCR5 expression increases with age and contributes to age-related cognitive decline [@cho2023]:

• Memory impairment: Elevated CCR5 signaling impairs hippocampal synaptic plasticity and memory.
• Neurogenesis decline: CCR5 modulates age-related decreases in adult neurogenesis.
• Inflammatory aging: CCR5 contributes to chronic low-grade inflammation characteristic of aging.

Interventions

• CCR5 antagonists: Show promise in reversing age-related cognitive decline.
• Lifestyle factors: Exercise and caloric restriction may modulate CCR5 expression.

Therapeutic Strategies

Drug Development

| Agent | Status | Mechanism | Indication |
|-------|--------|-----------|------------|
| Maraviroc | Approved (HIV), Investigational (AD) | CCR5 antagonist | HIV, AD |
| Vicriviroc | Clinical trials | CCR5 antagonist | HIV, AD |
| CCR5-targeting antibodies | Preclinical | Neutralizing antibodies | AD, PD |
| Gene therapy | Preclinical | RNA interference | PD |

Challenges

• Blood-brain barrier: Drug delivery to the CNS remains challenging
• Cell-type specificity: Targeting CCR5 on specific cell types (microglia vs neurons)
• Dose optimization: Balancing anti-inflammatory effects with immune competence

Research Directions

Current Knowledge Gaps

• Cell-type specific functions: How CCR5 function differs across cell types in the brain
• Downstream signaling: Precise molecular pathways mediating CCR5 effects in neurons
• Therapeutic window: Optimal timing and duration of CCR5-targeted interventions

Ongoing Studies

• Clinical trials: Evaluating CCR5 antagonists in AD and PD patients
• Biomarkers: Identifying CCR5-related biomarkers for disease monitoring
• Combination approaches: CCR5 targeting combined with other neuroprotective strategies

Cross-links

• [Chemokine Signaling](/mechanisms/chemokine-signaling)
• [Neuroinflammation](/mechanisms/neuroinflammation)
• [Microglia in Neurodegeneration](/mechanisms/microglia-neurodegeneration)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Synaptic Plasticity](/mechanisms/synaptic-plasticity)

See Also

• [Chemokine Receptors](/proteins/chemokine-receptors)
• [HIV-associated Neurocognitive Disorder](/diseases/hiv-neurocognitive-disorder)
• [Microglial Activation](/mechanisms/microglia-activation)
• [Aging and Neurodegeneration](/mechanisms/aging-neurodegeneration)

External Links

• [UniProt: P51681](https://www.uniprot.org/uniprot/P51681)
• [Gene: CCR5](https://www.ncbi.nlm.nih.gov/gene/1234)
• [IUPHAR: CCR5](https://www.guidetopharmacology.org/GPCR/108)
• [OMIM: 601373](https://www.omim.org/entry/601373)

References

Protein Interaction Network

Pathway Diagram

The following diagram shows the key molecular relationships involving CCR5 Protein discovered through SciDEX knowledge graph analysis: