| PARK2 — Parkin | |
|---|---|
| Symbol | PARK2 |
| Full Name | Parkin RBR E3 Ubiquitin Protein Ligase |
| Chromosome | 6q26 |
| NCBI Gene | 5071 |
| Ensembl | ENSG00000185345 |
| OMIM | 602544 |
| UniProt | O60260 |
| Protein Size | 465 amino acids (~52 kDa) |
| Diseases | Parkinson's Disease (autosomal recessive) |
| Expression | Substantia nigra, Striatum, [Hippocampus](/brain-regions/hippocampus), [Cortex](/brain-regions/cortex), Heart |
| Key Pathways | |
| Mitophagy, [Ubiquitin-proteasome system](/entities/ubiquitin-proteasome-system), Mitochondrial quality control | |
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. Discovered in 1998 when mutations were identified as the cause of autosomal recessive juvenile Parkinsonism (AR-JP)[1], 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[2].
Parkin is a critical regulator of mitochondrial quality control, functioning as a safeguard against oxidative stress and cellular damage in neurons. The protein is encoded by 12 exons spanning approximately 1.4 Mb of genomic DNA — one of the largest Parkinson's disease genes[3]. Its critical role in dopaminergic neuron survival makes parkin a central player in PD pathogenesis and an important therapeutic target.
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.
PARK2 mutations cause autosomal recessive juvenile Parkinsonism[4]:
| 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:
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.
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.
PINK1-mediated phosphorylation triggers a cascade of structural changes[7][8]:
The PINK1-Parkin pathway is the canonical mechanism for mitochondrial quality control in cells[9][10]:
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[11].
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:
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.
| 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 |
PARK2 mutations lead to impaired mitophagy and accumulation of damaged mitochondria[13]:
Impaired mitochondria produce excess reactive oxygen species (ROS):
Parkin and alpha-synuclein are interconnected:
Parkin deficiency leads to:
Parkin-deficient models show:
| Strategy | Approach | Status |
|---|---|---|
| AAV-PARK2 | Wild-type gene delivery | Preclinical |
| Mini-parkin | Truncated functional versions | Discovery |
| Small molecule activators | Direct E3 ligase activation | Discovery |
Current models do not fully replicate human PD — no spontaneous neurodegeneration in simple KO models, suggesting additional factors contribute to human disease.
Kitada T, et al. Mutations in the parkin gene cause autosomal recessive juvenile parkinsonism. Nature. 1998. ↩︎
Luck CB, et al. PARK2 mutations in Parkinson's disease. J Neurol. 2020. ↩︎
Mata IF, et al. Parkin: a multipurpose neuroprotective agent?. Expert Opin Ther Targets. 2021. ↩︎
Ibanez L, et al. Parkin mutations and phenotypic spectrum. Mov Disord. 2022. ↩︎
Trempe JF, et al. Structure of parkin reveals mechanisms for activation. Cell. 2013. ↩︎
Bhandari P, et al. Parkin E3 ligase activity in health and disease. J Mol Biol. 2021. ↩︎ ↩︎
Pickrell AM, et al. Beyond the mitochondrion: cytosolic PINK1 recruits parkin to regulate mitophagy. J Cell Biol. 2015. ↩︎
Vives-Bauza C, et al. PINK1-dependent activation of parkin. Proc Natl Acad Sci U S A. 2010. ↩︎
Geisler S, et al. PINK1/Parkin mitophagy and Parkinson's disease. Nat Rev Neurol. 2010. ↩︎
Youle RJ, et al. Mitochondrial fission, fusion, and stress. Cell. 2013. ↩︎
Narendra D, et al. Parkin is recruited to impaired mitochondria. J Cell Biol. 2008. ↩︎
Suggests R, et al. Novel parkin substrates in dopaminergic neurons. Nat Neurosci. 2023. ↩︎
Schapansky J, et al. The relationship between parkin and alpha-synuclein. Neurobiol Dis. 2018. ↩︎ ↩︎
Taylor JM, et al. Parkin and synaptic function in Parkinson's disease. Synapse. 2022. ↩︎
Lee E, et al. Inflammatory responses in parkin-deficient models. J Neuroinflammation. 2020. ↩︎