AIM2 Protein — Absent in Melanoma 2

AIM2 Protein — Absent in Melanoma 2

<div class="infobox infobox-protein">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">AIM2 Protein</th></tr>
<tr><td><strong>Protein Name</strong></td><td>AIM2 (Absent in Melanoma 2)</td></tr>
<tr><td><strong>Gene</strong></td><td>[AIM2](https://www.ncbi.nlm.nih.gov/gene/9447)</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[Q9UBR9](https://www.uniprot.org/uniprot/Q9UBR9)</td></tr>
<tr><td><strong>Molecular Weight</strong></td><td>~37 kDa</td></tr>
<tr><td><strong>Subcellular Localization</strong></td><td>Cytoplasm, nucleus</td></tr>
<tr><td><strong>Protein Family</strong></td><td>HIN-200 family (Pyrin/ AIM2-like receptors)</td></tr>
<tr><td><strong>Ligand</strong></td><td>Double-stranded DNA (dsDNA)</td></tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/aging" style="color:#ef9a9a">Aging</a>, <a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/atherosclerosis" style="color:#ef9a9a">Atherosclerosis</a>, <a href="/wiki/autoimmune" style="color:#ef9a9a">Autoimmune</a>, <a href="/wiki/bacterial-infection" style="color:#ef9a9a">Bacterial Infection</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">218 edges</a></td>
</tr>
</table>
</div>

Overview

AIM2 Protein — Absent in Melanoma 2

<div class="infobox infobox-protein">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">AIM2 Protein</th></tr>
<tr><td><strong>Protein Name</strong></td><td>AIM2 (Absent in Melanoma 2)</td></tr>
<tr><td><strong>Gene</strong></td><td>[AIM2](https://www.ncbi.nlm.nih.gov/gene/9447)</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[Q9UBR9](https://www.uniprot.org/uniprot/Q9UBR9)</td></tr>
<tr><td><strong>Molecular Weight</strong></td><td>~37 kDa</td></tr>
<tr><td><strong>Subcellular Localization</strong></td><td>Cytoplasm, nucleus</td></tr>
<tr><td><strong>Protein Family</strong></td><td>HIN-200 family (Pyrin/ AIM2-like receptors)</td></tr>
<tr><td><strong>Ligand</strong></td><td>Double-stranded DNA (dsDNA)</td></tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/aging" style="color:#ef9a9a">Aging</a>, <a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/atherosclerosis" style="color:#ef9a9a">Atherosclerosis</a>, <a href="/wiki/autoimmune" style="color:#ef9a9a">Autoimmune</a>, <a href="/wiki/bacterial-infection" style="color:#ef9a9a">Bacterial Infection</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">218 edges</a></td>
</tr>
</table>
</div>

Overview

AIM2 (Absent in Melanoma 2) is a critical cytosolic DNA sensor that plays a central role in the innate immune response by forming the AIM2 inflammasome. Discovered as a tumor suppressor whose loss contributes to melanoma progression, AIM2 has emerged as a key player in neuroinflammation and neurodegenerative diseases [1]. The AIM2 inflammasome detects foreign and endogenous double-stranded DNA in the cytosol, triggering a pro-inflammatory cascade that contributes to the chronic neuroinflammation observed in Alzheimer's disease (AD), Parkinson's disease (PD), and other neurodegenerative conditions [2].

The AIM2 protein is expressed in various cell types within the central nervous system (CNS), including [neurons](/entities/neurons), [astrocytes](/cell-types/astrocytes), [microglia](/cell-types/microglia-neuroinflammation), and oligodendrocytes. Its activation in these cell types contributes to the neuroinflammatory milieu that drives disease progression in multiple neurodegenerative disorders [3]. Understanding the AIM2 inflammasome pathway has become a major focus for developing therapeutic interventions aimed at modulating neuroinflammation in these devastating diseases.

Structure

AIM2 possesses a distinctive bipartite structure that enables its dual function as both a DNA sensor and an inflammasome scaffold:

Pyrin Domain (PYD)

• Interaction with ASC: The PYD recruits the adaptor protein ASC (PYCARD) through PYD-PYD interactions
• Oligomerization: AIM2 PYD mediates the formation of the inflammasome complex
• Signal integration: Serves as a platform for integrating upstream activation signals

HIN-200 Domain

• Oligosaccharide-binding (OB) folds: Two OB folds form a DNA-binding pocket
• dsDNA recognition: Binds double-stranded DNA of various lengths without sequence specificity
• Charge-dependent binding: DNA binding is mediated by electrostatic interactions with positively charged residues

Linker Region

• Conformational flexibility: Allows the protein to adapt to different DNA binding scenarios
• Auto-inhibition: May contribute to keeping AIM2 in an inactive state in the absence of DNA

Normal Function

DNA Sensing and Inflammasome Assembly

AIM2 functions as a pattern recognition receptor (PRR) for cytosolic double-stranded DNA:

Physiological Roles

In the normal CNS, AIM2-mediated inflammasome activation serves protective functions:

• Defense against pathogens: Detects viral and bacterial DNA in infected cells
• Tumor surveillance: Recognizes DNA from abnormal cells
• DNA damage response: May sense genomic instability
• Cell death regulation: Controls pyroptotic cell death pathways

Expression Pattern

AIM2 is expressed throughout the body with particular relevance to immune cells:

• Microglia: High expression in brain-resident macrophages
• Neurons: Moderate expression, increases with cellular stress
• Astrocytes: Constitutive expression, upregulated in inflammation
• Peripheral immune cells: B cells, dendritic cells, macrophages

Role in Neurodegeneration

Alzheimer's Disease

AIM2 plays a significant role in Alzheimer's disease pathogenesis through multiple mechanisms [4]:

Amyloid-β-Induced Inflammasome Activation:

• Aβ plaques contain DNA that can activate AIM2
• Aβ directly interacts with microglia to increase AIM2 expression
• AIM2 inflammasome activation contributes to chronic neuroinflammation

• Elevated IL-1β in AD brain correlates with disease severity
• IL-1β promotes tau phosphorylation and aggregation
• Sustained IL-1β release drives synaptic dysfunction

• AIM2 activation creates a feed-forward inflammatory loop
• Cytokine release attracts additional immune cells
• Contributes to the chronic inflammatory microenvironment

• AIM2 inhibitors under development for AD
• Targeting inflammasome components may reduce neuroinflammation

Parkinson's Disease

AIM2 contributes to Parkinson's disease through several pathways [5]:

α-Synuclein-Induced Activation:

• α-Synuclein aggregates can trigger AIM2 inflammasome
• Microglial activation by α-synuclein increases AIM2 expression
• Inflammasome activation contributes to dopaminergic neuron loss

• Post-mortem studies show increased AIM2 in PD substantia nigra
• IL-1β levels elevated in PD cerebrospinal fluid
• Inflammasome activation exacerbates motor symptoms

• Damaged mitochondria release mitochondrial DNA
• AIM2 may sense mitochondrial DNA in stressed neurons
• Contributes to inflammatory responses in PD

Multiple Sclerosis

AIM2 has been implicated in multiple sclerosis (MS):

• Demyelination: Inflammasome activation in oligodendrocytes
• Blood-brain barrier: Disruption through inflammatory mediators
• Lesion formation: Contributes to chronic demyelinating lesions

Amyotrophic Lateral Sclerosis (ALS)

In ALS, AIM2 contributes to motor neuron degeneration:

• Motor neuron vulnerability: High AIM2 expression in affected neurons
• Glial inflammation: Microglial AIM2 drives progressive inflammation
• Disease progression: Inflammasome activation correlates with progression

Inflammasome Signaling Pathway

Activation Triggers

AIM2 inflammasome can be activated by:

Signaling Cascade

dsDNA → AIM2 → ASC → Pro-caspase-1
↓
Active caspase-1
↓
┌───────────────────┴───────────────────┐
↓ ↓
Pro-IL-1β → IL-1β Pro-IL-18 → IL-18
↓ ↓
Pyroptosis Inflammation
Cell death Immune recruitment

Regulatory Mechanisms

AIM2 activity is tightly regulated:

• Post-translational modifications: Phosphorylation, ubiquitination
• Negative regulators: ASC antagonists, caspase inhibitors
• Cellular localization: Sequestration prevents inappropriate activation
• Epigenetic control: Transcriptional regulation of AIM2 expression

Therapeutic Targeting

Drug Development

Several approaches target AIM2 inflammasome:

| Approach | Mechanism | Status | Example |
|----------|-----------|--------|---------|
| AIM2 inhibitors | Block DNA binding | Preclinical | Small molecule inhibitors |
| ASC inhibitors | Prevent inflammasome assembly | Preclinical | MCC950 |
| Caspase-1 inhibitors | Block cytokine cleavage | Clinical | VX-765 |
| IL-1R antagonists | Block cytokine signaling | Approved | Anakinra, Canakinumab |

Clinical Applications

Alzheimer's Disease:

• Ongoing trials with NLRP3 inflammasome inhibitors
• IL-1β targeting strategies in early trials
• Gene therapy approaches to reduce AIM2 expression

• Inflammasome inhibitors in preclinical models
• IL-1β blockade shows neuroprotective effects
• Targeting microglial AIM2 activation

Challenges

• Specificity: Ensuring AIM2 selectivity over other inflammasomes
• Delivery: Crossing the blood-brain barrier
• Timing: Optimal intervention point in disease course
• Safety: Balancing inflammation suppression with host defense

Animal Models

Transgenic Models

• AIM2 knockout mice: Reduced inflammation in disease models
• AIM2 overexpression: Increased susceptibility to inflammatory damage
• Humanized models: AIM2 expressed in human cells

Disease Models

• AD models: 5xFAD, APP/PS1 mice with AIM2 modulation
• PD models: MPTP, α-synuclein transgenic mice
• MS models: EAE (Experimental Autoimmune Encephalomyelitis)

Genetic Variation

Polymorphisms in the AIM2 gene have been associated with:

• Autoimmune diseases: SLE, rheumatoid arthritis
• Infectious disease susceptibility: Viral infections
• Cancer risk: Melanoma, other malignancies
• Neurological disease: Potential modifiers of AD/PD risk

Biomarkers

AIM2-related biomarkers under investigation:

• IL-1β levels: Peripheral and CSF measurements
• ASC specks: Circulating inflammasome components
• AIM2 expression: Gene expression in immune cells
• Genetic markers: SNP associations with disease

See Also

• [Neuroinflammation](/cell-types/microglia-neuroinflammation)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Inflammasome Signaling](/mechanisms/nlrp3-inflammasome)
• [Microglia](/cell-types/microglia-neuroinflammation)
• [Cytokines in Neurodegeneration](/biomarkers/inflammatory-biomarkers)

External Links

• [UniProt Q9UBR9](https://www.uniprot.org/uniprot/Q9UBR9)
• [NCBI Gene AIM2](https://www.ncbi.nlm.nih.gov/gene/9447)
• [IUPHAR Database](https://www.guidetopharmacology.org/)
• [Human Protein Atlas](https://www.proteinatlas.org/)

References