Gene Symbol: PARK2
Full Name: Parkin RBR E3 Ubiquitin Protein Ligase
Chromosomal Location: 6q26
NCBI Gene ID: 5071
OMIM: 600116
Ensembl ID: ENSG00000185358
UniProt ID: O60260
Associated Diseases: Parkinson's Disease, Autosomal Recessive Juvenile Parkinsonism
PARKIN (also known as PARK2, PRKN) is a critical gene in the study of neurodegenerative diseases, particularly Parkinson's disease. This gene encodes the parkin protein, an E3 ubiquitin ligase essential for mitochondrial quality control through mitophagy. Mutations in PARKIN cause autosomal recessive juvenile parkinsonism (ARJP), characterized by early-onset Parkinson's disease with a typically slow but progressive course.
The PARKIN gene is located on chromosome 6q26 and spans approximately 1.4 Mb, making it one of the largest genes in the human genome. It contains 12 exons encoding a 465-amino acid protein. The gene was first linked to Parkinson's disease in 1998 when homozygous mutations were identified in families with autosomal recessive juvenile parkinsonism.
Parkin is a cytosolic E3 ubiquitin ligase essential for mitochondrial maintenance and quality control. Its normal functions encompass several critical cellular processes:
Parkin plays a central role in maintaining mitochondrial homeostasis through multiple mechanisms:
The PINK1-Parkin pathway is the primary mechanism for mitochondrial quality control. Here's how it works:
PINK1 stabilization: In healthy mitochondria, PINK1 (PTEN-induced kinase 1) is imported and degraded. In damaged mitochondria, PINK1 accumulates on the outer mitochondrial membrane.
PINK1 activation: Activated PINK1 phosphorylates ubiquitin at Ser65 and the Ubl domain of parkin at Ser65.
Parkin activation: Phospho-ubiquitin binds to parkin's RING0 domain, triggering a conformational change that activates its E3 ligase activity.
Ubiquitin chain formation: Active parkin ubiquitinates outer mitochondrial membrane proteins, forming Lys63-linked polyubiquitin chains.
Autophagy receptor recruitment: p62/SQSTM1, OPTN, and NDP52 bind these ubiquitin chains and link mitochondria to the growing autophagosome.
Mitophagy execution: The LC3-coated autophagosome fuses with lysosomes, degrading the damaged mitochondrion.
Beyond mitophagy, parkin performs several other essential functions:
The parkin protein (465 amino acids, ~52 kDa) contains multiple functional domains arranged in a specific architecture:
| Domain | Amino Acids | Function |
|---|---|---|
| Ubl domain | 1-76 | Proteasome binding, phosphorylation target |
| RING0 | 140-200 | Phospho-ubiquitin binding, regulatory |
| RING1 | 212-255 | E2 enzyme binding |
| IBR | 321-380 | E2 enzyme binding, dimerization |
| RING2 | 418-465 | Catalytic, ubiquitin transfer |
The RBR (RING-IBR-RING) architecture is unique among E3 ligases. The RING1 domain binds E2~Ub conjugates, while RING2 contains the catalytic cysteine that transfers ubiquitin to substrates. The IBR domain bridges these two RINGs and contributes to substrate recognition.
PARKIN-linked ARJP (also called PARK2) accounts for approximately 50% of early-onset familial Parkinson's disease and about 10-20% of early-onset PD cases overall:
Beyond ARJP, PARKIN mutations contribute to Parkinson's disease in several ways:
The primary pathogenic mechanism in PARKIN-linked PD is impaired mitophagy:
Over 200 pathogenic mutations in PARKIN have been identified, including:
Common pathogenic variants include:
Several animal models have been developed to study PARKIN function:
Parkin interacts with numerous proteins forming a complex network:
| Partner | Interaction Type | Function |
|---|---|---|
| PINK1 | Phosphorylation | Mitophagy initiation |
| UBC6, UBC7 | E2 enzyme | Ubiquitin transfer |
| p62/SQSTM1 | Binding | Autophagy receptor |
| OPTN | Binding | Autophagy receptor |
| NDP52 | Binding | Autophagy receptor |
| VCP/p97 | Binding | Protein degradation |
| BCL2 | Binding | Anti-apoptotic |
| CDC37 | Binding | Chaperone function |
Current research focuses on: