PARK2 — Parkin Gene Entity Page

PARK2 — Parkin Gene Entity Page

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">PARK2 — Parkin</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td><strong>PARK2</strong></td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Parkin RBR E3 Ubiquitin Protein Ligase</td>
</tr>
<tr>
<td class="label">Chromosome</td>
<td>6q26</td>
</tr>
<tr>
<td class="label">NCBI Gene</td>
<td><a href="https://www.ncbi.nlm.nih.gov/gene/5071" target="_blank">5071</a></td>
</tr>
<tr>
<td class="label">Ensembl</td>
<td><a href="https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000185345" target="_blank">ENSG00000185345</a></td>
</tr>
<tr>
<td class="label">OMIM</td>
<td><a href="https://omim.org/entry/602544" target="_blank">602544</a></td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/O60260" target="_blank">O60260</a></td>
</tr>
<tr>
<td class="label">Protein Size</td>
<td>465 amino acids (~52 kDa)</td>
</tr>
<tr>
<td class="label">Diseases</td>
<td><a href="/diseases/parkinsons-disease">Parkinson's Disease</a> (autosomal recessive)</td>
</tr>
<tr>
<td class="label">Expression</td>
<td>Substantia nigra, Striatum, Hippocampus, Cortex, Heart</td>
</tr>
<tr>
<th class="infobox-subheader" colspan="2">Key Pathways</th>
</tr>
<tr>
<td colspan="2" style="font-size:0.85em">Mitophagy, Ubiquitin-proteasome system, Mitochondrial quality control</td>
</tr>
</table>

PARK2 — Parkin Gene Entity Page

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">PARK2 — Parkin</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td><strong>PARK2</strong></td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Parkin RBR E3 Ubiquitin Protein Ligase</td>
</tr>
<tr>
<td class="label">Chromosome</td>
<td>6q26</td>
</tr>
<tr>
<td class="label">NCBI Gene</td>
<td><a href="https://www.ncbi.nlm.nih.gov/gene/5071" target="_blank">5071</a></td>
</tr>
<tr>
<td class="label">Ensembl</td>
<td><a href="https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000185345" target="_blank">ENSG00000185345</a></td>
</tr>
<tr>
<td class="label">OMIM</td>
<td><a href="https://omim.org/entry/602544" target="_blank">602544</a></td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/O60260" target="_blank">O60260</a></td>
</tr>
<tr>
<td class="label">Protein Size</td>
<td>465 amino acids (~52 kDa)</td>
</tr>
<tr>
<td class="label">Diseases</td>
<td><a href="/diseases/parkinsons-disease">Parkinson's Disease</a> (autosomal recessive)</td>
</tr>
<tr>
<td class="label">Expression</td>
<td>Substantia nigra, Striatum, Hippocampus, Cortex, Heart</td>
</tr>
<tr>
<th class="infobox-subheader" colspan="2">Key Pathways</th>
</tr>
<tr>
<td colspan="2" style="font-size:0.85em">Mitophagy, Ubiquitin-proteasome system, Mitochondrial quality control</td>
</tr>
</table>

PARK2 — Parkin Gene Entity

Overview

PARK2 (Parkin RBR E3 Ubiquitin Protein Ligase) is a gene located on chromosome 6q26 that encodes the parkin protein — a RING-between-RING (RBR) family E3 ubiquitin ligase that serves as the central effector of the [PINK1-Parkin mitophagy pathway](/mechanisms/pink1-parkin-mitophagy). Discovered in 1998 when mutations were identified as the cause of autosomal recessive juvenile Parkinsonism (AR-JP)[@kitada1998], PARK2 is now recognized as one of the most frequently mutated genes in familial Parkinson's disease, accounting for approximately 50% of AR-JP cases and up to 20% of early-onset PD[@luck2020].

Parkin is a critical regulator of mitochondrial quality control, functioning as a safeguard against oxidative stress and cellular damage in [neurons](/entities/neurons). The protein is encoded by 12 exons spanning approximately 1.4 Mb of genomic DNA — one of the largest Parkinson's disease genes[@mata2021]. Its critical role in dopaminergic neuron survival makes parkin a central player in PD pathogenesis and an important therapeutic target.

Gene Structure and Mutation

Genomic Organization

The PARK2 gene is exceptionally large for a single gene at ~1.4 Mb. The 12 exons encode a 465-amino acid protein (~52 kDa). The gene's large size makes it susceptible to deletions, duplications, and other structural variations that disrupt protein function.

Mutations in Parkinson's Disease

PARK2 mutations cause autosomal recessive juvenile Parkinsonism[@ibanez2022]:

| Mutation Type | Frequency | Examples |
|--------------|-----------|---------|
| Exon deletions | 30-40% | Complete exon loss |
| Missense | 20-30% | R42P, C250F, T415N |
| Nonsense | 10-15% | Q34X, R245X |
| Splice site | 5-10% | IVS1+1G>A |
| Multi-exon deletions | 15-20% | Spanning 2-5 exons |
| Duplications | 5-10% | Partial gene copy number |

Inheritance: Autosomal recessive — both alleles must be mutated for disease. Heterozygous carriers show no phenotype (complete recessiveness).

Clinical features:

• Onset typically before age 20 (juvenile)
• Early motor fluctuations and dystonia
• Tremor (less prominent than idiopathic PD)
• Slow progression compared to idiopathic PD
• Good levodopa response
• Sleep benefit (patients feel better after sleep)

Protein Structure and Function

Domain Architecture[@trempe2013]

Parkin has a complex multi-domain structure with unique features:

Ubiquitin-like (Ubl) Domain (residues 1-76): Located at the N-terminus. Adopts a β-grasp fold similar to ubiquitin. Can be autoubiquitinated. Critical for activation — PINK1 phosphorylates Ser65 within this domain.

RING0 Domain (residues 141-217): Unique RING-like element not found in other RING finger proteins. Contains the "RING-helix-RING" motif essential for E2 enzyme binding.

RING1 Domain (residues 237-328): Mediates binding to E2 ubiquitin-conjugating enzymes (particularly UBC7/UBC7). Contains the canonical C3H2C3 RING finger motif.

In-between-RING (IBR) Domain (residues 329-380): A unique structural element between RING1 and RING2. Contributes to substrate recognition and proper positioning of catalytic domains.

RING2 Domain (residues 418-465): Contains the catalytic cysteine (Cys431) that forms a thioester intermediate with ubiquitin during the ubiquitination reaction.

Repressor Element (REP) (residues 466-494): Autoinhibitory region that blocks substrate access when parkin is in the inactive conformation.

Auto-Inhibition Mechanism[@bhandari2021]

Parkin exists in an autoinhibited state under normal conditions:

This autoinhibition is relieved by PINK1 phosphorylation at Ser65, which triggers major conformational changes that activate parkin's E3 ligase activity.

Activation by PINK1

PINK1-mediated phosphorylation triggers a cascade of structural changes[@pickrell2015][@vives2010]:

The PINK1-Parkin Mitophagy Pathway

Mitochondrial Quality Control

The PINK1-Parkin pathway is the canonical mechanism for mitochondrial quality control in cells[@geisler2010][@youle2013]:

Key Steps in Mitophagy

• VDAC1: Voltage-dependent anion channel 1
• Tomm20: Translocase of outer membrane 20
• Miro1: Mitochondrial Rho GTPase
• MFN1/2: Mitofusins

Substrates and Ubiquitin Linkages

Parkin Substrates[@suggests2023][@bhandari2021]

| Substrate | Ubiquitin Linkage | Function |
|-----------|------------------|---------|
| VDAC1 | K63 | Mitochondrial pore, mitophagy receptor |
| Tomm20 | K27, K63 | Protein translocase |
| MFN1/2 | K48, K63 | Mitochondrial fusion |
| Miro1 | K48 | Mitochondrial motility |
| Pael-R | K48 | Proteasomal degradation |
| Synphilin-1 | K48, K63 | Protein aggregation |
| p53 | K48 | Apoptosis regulation |
| Hsp70 | K48 | Chaperone, protein quality control |
| CDC27 | K48 | Cell cycle regulation |

Ubiquitin Chain Types

• K48-linked chains: Signal for proteasomal degradation
• K63-linked chains: Signal for mitophagy and signaling
• K27-linked chains: Specific for mitophagy initiation

Disease Mechanisms

Mitochondrial Dysfunction

PARK2 mutations lead to impaired mitophagy and accumulation of damaged mitochondria[@schapansky2018]:

• Defective clearance: Damaged mitochondria persist in cells
• ATP depletion: Insufficient energy for neuronal function
• ROS accumulation: Oxidative stress damages cellular components
• Calcium dysregulation: Mitochondrial calcium handling impaired
• Dopaminergic vulnerability: High metabolic demand makes SNc neurons particularly susceptible

Oxidative Stress

Impaired mitochondria produce excess [reactive oxygen species](/entities/reactive-oxygen-species) (ROS):

• Oxidative damage to proteins, lipids, and DNA
• Activation of stress pathways
• Contribution to alpha-synuclein aggregation
• Progressive neuronal dysfunction

Relationship to Alpha-Synuclein[@schapansky2018]

Parkin and alpha-synuclein are interconnected:

• Parkin ubiquitinates alpha-synuclein for degradation
• Oxidative stress promotes alpha-synuclein aggregation
• Aggregated alpha-synuclein impairs mitochondrial function
• Loss of parkin function accelerates synuclein pathology
• Both proteins aggregate in Lewy bodies

Synaptic Dysfunction[@taylor2022]

Parkin deficiency leads to:

• Impaired synaptic vesicle trafficking
• Altered neurotransmitter release
• Synaptic terminal degeneration
• Preclinical changes before neuronal death

Neuroinflammation[@lee2020]

Parkin-deficient models show:

• Enhanced microglial activation
• Increased pro-inflammatory cytokine production
• Chronic neuroinflammation
• Contributions to progressive neurodegeneration

Therapeutic Approaches

Gene Therapy

| Strategy | Approach | Status |
|---------|----------|--------|
| AAV-PARK2 | Wild-type gene delivery | Preclinical |
| Mini-parkin | Truncated functional versions | Discovery |
| Small molecule activators | Direct E3 ligase activation | Discovery |

Pharmacological Approaches

• Parkin activators: Compounds that enhance E3 ligase activity
• Mitochondrial protectants: Targeting downstream effects of parkin loss
• Antioxidants: Counteracting oxidative stress (CoQ10, MitoQ)
• Autophagy enhancers: mTOR-independent pathways to compensate

Neuroprotective Strategies

• BDNF expression: Supporting neuronal survival
• Mitochondrial dynamics modulators: FIS1, OPA1 modulators
• Calcium stabilizers: Protecting mitochondrial calcium handling

Biomarkers

Parkin Activity

• E3 ligase activity assays
• Ubiquitin chain analysis
• Phospho-Ser65 parkin detection

Mitochondrial Function

• Live-cell imaging of mitophagy (mt-Keima)
• Membrane potential measurements
• ATP production rates
• ROS production

Genetic Testing

• Comprehensive mutation screening
• Copy number analysis
• Split-read sequencing for structural variants

Animal Models

Knockout Models

• Parkin⁻/⁻ mice: No spontaneous neurodegeneration, but altered dopamine metabolism and enhanced vulnerability to mitochondrial toxins
• Parkin⁻/⁻ zebrafish: Developmental defects, mitochondrial dysfunction

Disease Models

• MPTP + Parkin KO: Enhanced vulnerability to mitochondrial toxins
• α-Syn + Parkin KO: Synergistic protein aggregation and加重 pathology
• PINK1/Parkin double KO: Severe mitochondrial dysfunction

Limitations

Current models do not fully replicate human PD — no spontaneous neurodegeneration in simple KO models, suggesting additional factors contribute to human disease.

See Also

• [PARK2 Gene Page](/genes/park2) — Comprehensive gene-level page
• [PINK1 Gene](/genes/pink1) — Partner in mitophagy pathway
• [Parkin Protein](/proteins/parkin) — Protein-level page
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [PINK1-Parkin Mitophagy Pathway](/mechanisms/pink1-parkin-mitophagy)
• [Mitochondrial Dysfunction in PD](/mechanisms/mitochondrial-dysfunction-parkinsons)
• [Alpha-Synuclein](/genes/snca) — Interacting protein in PD

External Links

• NCBI Gene: [5071](https://www.ncbi.nlm.nih.gov/gene/5071)
• Ensembl: [ENSG00000185345](https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000185345)
• OMIM: [602544](https://www.omim.org/entry/602544)
• UniProt: [O60260](https://www.uniprot.org/uniprot/O60260)
• PDGene: [PARK2 overview](https://www.pdgene.org/geneoverview?geneid=5071)
• Allen Human Brain Atlas: [PARK2 expression](https://human.brain-map.org/microarray/search/show?search_term=PARK2)