PRKN (parkin RBR E3 ubiquitin protein ligase; HGNC:8607, NCBI Gene ID 5071) is a human locus mapped to chromosome band 6q26 that encodes cytosolic RING-between-RING (RBR) E3 ubiquitin ligase Parkin (465 aa; EC 2.3.2.31). PRKN acts in PINK1-Parkin ubiquitin-amplification feed-forward loop & autophagosomal clearance of damaged mitochondria, together with PINK1 (Mitochondrial Kinase Sensor Gene), PPARGC1A (PGC-1alpha Mitochondrial Biogenesis Gene), and Mitochondrion. Encodes the Parkin RBR E3 ubiquitin ligase activated by PINK1 to ubiquitylate outer mitochondrial membrane proteins for mitophagy.
PINK1-Parkin ubiquitin-amplification feed-forward loop & autophagosomal clearance of damaged mitochondria
Clinical / Therapeutic Role
Most common cause of Autosomal Recessive Juvenile/Early-Onset Parkinson Disease (PARK2)
Gene Structure & Expression
Genomic Organization & Cytogenetic Locus: 12-exon mega-gene spanning ~1.38 megabases within the FRA6E common fragile site on chromosome 6q26 (one of the largest genes in the human genome after DMD), encoding a 465-amino-acid autoinhibited enzyme composed of an N-terminal ubiquitin-like (Ubl) domain and four zinc-coordinating RING-like domains (RING0, RING1, IBR, and catalytic Cys431-containing RING2).
Cellular & Tissue Expression Profile: Abundantly expressed in central nervous system neurons (especially substantia nigra dopaminergic neurons), cardiac myocytes, skeletal muscle fibers, and hepatic hepatocytes.
Molecular Function & Pathways
Biochemical & Physiological Mechanism: Remains catalytically autoinhibited in the cytosol until PINK1-generated phospho-Ser65-ubiquitin on a depolarized mitochondrion binds Parkin RING1 and exposes the Parkin Ubl domain for Ser65 phosphorylation by PINK1; fully activated Parkin then conjugates K6-, K11-, K48-, and K63-linked polyubiquitin chains onto outer mitochondrial membrane proteins (MFN1, MFN2, VDAC1, MIRO1/RHOT1), which PINK1 further phosphorylates to recruit autophagy receptors OPTN and NDP52.
Clinical & Therapeutic Significance
Human Genetic Variants & Disease Phenotypes: Homozygous or compound heterozygous exon deletions, duplications, and point mutations in PRKN (formerly PARK2) are the single most frequent genetic cause of autosomal recessive juvenile and early-onset Parkinson disease (onset typically before age 40, often presenting without Lewy bodies), while loss of Parkin also releases cytosolic PARIS (ZNF746) to repress PGC-1alpha (PPARGC1A) transcription and mitochondrial biogenesis.
Therapeutic & Clinical Pharmacology: Targeted by USP30 deubiquitinase inhibitors (which prevent USP30 from stripping Parkin-assembled ubiquitin chains off damaged mitochondria) and small-molecule allosteric Parkin activators in neurodegenerative and cardiometabolic disease.