AGO2 Protein

AGO2 Protein — Argonaute RISC Component 2

<div class="infobox infobox-protein">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">AGO2 Protein</th></tr>
<tr><td><strong>Protein Name</strong></td><td>Argonaute RISC Component 2</td></tr>
<tr><td><strong>Gene</strong></td><td>[AGO2](/genes/ago2)</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[Q9UQ21](https://www.uniprot.org/uniprot/Q9UQ21)</td></tr>
<tr><td><strong>PDB ID</strong></td><td>4w5n, 4w5r, 5oui</td></tr>
<tr><td><strong>Molecular Weight</strong></td><td>~97 kDa</td></tr>
<tr><td><strong>Subcellular Localization</strong></td><td>Cytoplasm, P-bodies, Stress granules</td></tr>
<tr><td><strong>Protein Family</strong></td><td>Argonaute family, PIWI/AGO superfamily</td></tr>
<tr><td><strong>Expression</strong></td><td>Ubiquitous; high in brain, heart, muscle</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/breast-cancer" style="color:#ef9a9a">Breast Cancer</a>, <a href="/wiki/cancer" style="color:#ef9a9a">Cancer</a>, <a href="/wiki/depression" style="color:#ef9a9a">Depression</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">48 edges</a></td>
</tr>
</table>
</div>

Overview

AGO2 Protein — Argonaute RISC Component 2

<div class="infobox infobox-protein">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">AGO2 Protein</th></tr>
<tr><td><strong>Protein Name</strong></td><td>Argonaute RISC Component 2</td></tr>
<tr><td><strong>Gene</strong></td><td>[AGO2](/genes/ago2)</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[Q9UQ21](https://www.uniprot.org/uniprot/Q9UQ21)</td></tr>
<tr><td><strong>PDB ID</strong></td><td>4w5n, 4w5r, 5oui</td></tr>
<tr><td><strong>Molecular Weight</strong></td><td>~97 kDa</td></tr>
<tr><td><strong>Subcellular Localization</strong></td><td>Cytoplasm, P-bodies, Stress granules</td></tr>
<tr><td><strong>Protein Family</strong></td><td>Argonaute family, PIWI/AGO superfamily</td></tr>
<tr><td><strong>Expression</strong></td><td>Ubiquitous; high in brain, heart, muscle</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/breast-cancer" style="color:#ef9a9a">Breast Cancer</a>, <a href="/wiki/cancer" style="color:#ef9a9a">Cancer</a>, <a href="/wiki/depression" style="color:#ef9a9a">Depression</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">48 edges</a></td>
</tr>
</table>
</div>

Overview

AGO2 (Argonaute RISC Component 2) is the central effector protein of the RNA-induced silencing complex (RISC), mediating microRNA (miRNA) and small interfering RNA (siRNA)-guided gene silencing. It is the only Argonaute with catalytic slicer activity in humans, enabling it to cleave target RNAs, making it essential for both miRNA-mediated repression and siRNA-mediated RNA interference.^[1]

Structure

AGO2 contains multiple conserved domains that orchestrate small RNA binding and target cleavage:

N-Terminal Domain

• Lobes N-terminal: Flexible region involved in small RNA loading
• Contains the slicer-independent silencing functions

PAZ Domain (PIWI-Argonaute-Zwille)

• Binds the 3' end of small RNAs (miRNAs, siRNAs)
• Recognizes the 2-nucleotide 3' overhang of duplex siRNAs
• Anchors the guide strand while the passenger strand is discarded

Mid Domain

• Binds the 5' phosphate of the guide small RNA
• Contains the seed region (nucleotides 2-8) that mediates target recognition
• Interfaces with GW182 for miRNA-mediated silencing

PIWI Domain

• Contains the catalytic DEDH Asp triad (D597, D669, D709)
• Possesses endonucleolytic slicer activity
• Binds the guide-target RNA duplex central region

Linker Regions

• Connect domains for conformational flexibility
• Allosteric regulation of catalytic activity

Normal Function

MicroRNA-Mediated Gene Silencing

miRNA Loading

Target Recognition

• miRNA "seed region" (nucleotides 2-8) pairs with complementary sites in target mRNA 3' UTRs
• Additional pairing downstream supports stable binding
• Multiple miRNA binding sites cooperatively enhance repression

Silencing Mechanisms

• Transcriptional: Rarely, miRNA-AGO2 complexes enter nucleus to modulate transcription
• Post-transcriptional:
• Translation inhibition (initiation and elongation blocks)
• mRNA destabilization (deadenylation and decay)
• Ribosome drop-off

Slicer-Dependent Functions

• siRNA-mediated cleavage: Complete complementarity leads to target mRNA cleavage
• miRNA "slicing": In rare cases of near-perfect complementarity
• miRNA maturation: Some pri-miRNA processing by nuclear AGO2

Non-Catalytic Functions

• miRNA-independent gene regulation
• Cellular stress responses
• Telomere maintenance

Role in Disease

Neurodegeneration

Alzheimer's Disease

• Altered miRNA processing: Global miRNA dysregulation in AD brains
• Amyloid processing: AGO2 regulates [APP](/entities/app-protein) and [BACE1](/entities/bace1) expression via miRNAs
• [Tau](/proteins/tau) pathology: miRNA-AGO2 targeting of tau kinases and phosphatases
• Synaptic dysfunction: miRNA-AGO2 dysregulation affects synaptic proteins
• Neuronal vulnerability: Reduced AGO2 activity in AD [neurons](/entities/neurons)

Parkinson's Disease

• [Alpha-synuclein](/proteins/alpha-synuclein) aggregation affects miRNA processing^[4]
• AGO2 involved in regulating [LRRK2](/entities/lrrk2) expression
• miRNA dysregulation in PD substantia nigra

Amyotrophic Lateral Sclerosis (ALS)

• AGO2 mutations cause familial ALS^[5]
• Altered miRNA processing in motor neurons
• Stress granule dynamics affected

Huntington's Disease

• Mutant [HTT](/proteins/huntingtin) sequesters AGO2
• Global miRNA dysregulation
• Derepression of beneficial miRNA targets

Cancer

AGO2 is frequently overexpressed in cancers:

• Promotes tumor growth and metastasis
• Therapeutic target under investigation
• Regulates oncogenes and tumor suppressors via miRNAs

Neurological Development

• Essential for neuronal development
• Regulates neurogenesis
• Controls axon guidance
• Modulates synaptic plasticity

Therapeutic Implications

Neurodegeneration

miRNA-Based Therapies

• miRNA mimics: Restore beneficial miRNA levels
• miRNA antagonists (antagomirs): Block pathogenic miRNAs
• AGO2 modulators: Enhance or inhibit function

siRNA Therapeutics

• AGO2 enables siRNA-based gene silencing
• Being developed for neurodegenerative targets
• Delivery to brain remains challenge

Cancer Therapy

• AGO2 inhibitors: Being developed to block oncogenic miRNA function
• Combination with chemotherapy: Sensitize tumors
• siRNA delivery: Exploit AGO2's slicer activity

Key Publications

External Links

• [Wikipedia](https://en.wikipedia.org/)
• [NCBI Resources](https://www.ncbi.nlm.nih.gov/)

References

^[1] [Argonaute proteins: Evolution and function (2020)](https://pubmed.ncbi.nlm.nih.gov/32781038/)
^[2] [Mechanisms of miRNA-mediated silencing (2013)](https://pubmed.ncbi.nlm.nih.gov/23574579/)
^[3] [MicroRNA in Alzheimer's disease (2017)](https://pubmed.ncbi.nlm.nih.gov/28771250/)
^[4] [AGO2 and alpha-synuclein in PD (2019)](https://pubmed.ncbi.nlm.nih.gov/30626711/)
^[5] [AGO2 mutations in ALS (2018)](https://pubmed.ncbi.nlm.nih.gov/30030412/)
^[6] [Therapeutic potential of RNA interference (2021)](https://pubmed.ncbi.nlm.nih.gov/33539672/)

See Also

• AGO2 Gene
• [MicroRNA Biogenesis](/content/genes)
• RNA-Induced Silencing Complex
• [Alzheimer's Disease Mechanisms](/mechanisms/alzheimers-disease-mechanisms)
• [Parkinson's Disease Mechanisms](/mechanisms/parkinsons-disease-mechanisms)
• [Synaptic Dysfunction](/mechanisms/synaptic-dysfunction)