PARK2 — Parkin Gene Entity Page

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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

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:

The Ubl domain binds to the RING0-RING1-IBR region, blocking substrate access

The REP element occludes the catalytic site

E2 binding is obstructed by the auto-inhibitory conformation

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]:

Ubl domain release: Phosphorylation disrupts the inhibitory Ubl-RING interaction

RING domain repositioning: Catalytic domains become accessible

E2 recruitment: Activated parkin binds E2 enzymes

Catalytic activation: Cys431 becomes active for ubiquitin transfer

Substrate ubiquitination: Recognition of damaged mitochondria

The PINK1-Parkin Mitophagy Pathway

Mitochondrial Quality Control

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

Mermaid diagram (expand to render)

Key Steps in Mitophagy

Damage Detection: In healthy mitochondria, PINK1 is imported through the TOM/TIM complex and cleaved by MPP and PARL. In damaged mitochondria, membrane potential is lost, preventing PINK1 import and leading to its accumulation on the outer membrane[@narendra2008].

PINK1 Activation: Accumulated PINK1 undergoes autophosphorylation and activation.

Parkin Recruitment: PINK1 phosphorylates parkin at Ser65 (Ubl domain) and phosphorylates ubiquitin, creating a feed-forward activation loop.

Substrate Ubiquitination: Activated parkin ubiquitinates outer mitochondrial membrane proteins:

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

Receptor Recruitment: K63-linked ubiquitin chains are recognized by autophagic receptors (p62/SQSTM1, NDP52, OPTN) that link mitochondria to the growing autophagosome.

Lysosomal Degradation: The autophagosome fuses with lysosomes, completing the degradation of damaged mitochondria.

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.

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)

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PARK2 — Parkin Gene Entity Page

PARK2 — Parkin Gene Entity Page

PARK2 — Parkin Gene Entity Page

PARK2 — Parkin Gene Entity

Overview

Gene Structure and Mutation

Genomic Organization

Mutations in Parkinson's Disease

Protein Structure and Function

Domain Architecture[@trempe2013]

Auto-Inhibition Mechanism[@bhandari2021]

Activation by PINK1

The PINK1-Parkin Mitophagy Pathway

Mitochondrial Quality Control

Key Steps in Mitophagy

Substrates and Ubiquitin Linkages

Parkin Substrates[@suggests2023][@bhandari2021]

Ubiquitin Chain Types

Disease Mechanisms

Mitochondrial Dysfunction

Oxidative Stress

Relationship to Alpha-Synuclein[@schapansky2018]

Synaptic Dysfunction[@taylor2022]

Neuroinflammation[@lee2020]

Therapeutic Approaches

Gene Therapy

Pharmacological Approaches

Neuroprotective Strategies

Biomarkers

Parkin Activity

Mitochondrial Function

Genetic Testing

Animal Models

Knockout Models

Disease Models

Limitations

See Also

External Links