PJA1 (Praja1, encoded by the PJA1 gene) is a RING finger E3 ubiquitin ligase that plays a critical role in protein quality control and ubiquitination. Originally identified in mouse brain, Praja1 has emerged as an important regulator of neurodegeneration through its ability to ubiquitinate and degrade pathological proteins including tau, TDP-43, SOD1, FUS, α-synuclein, and huntingtin.[1]
| Property | Value |
|---|---|
| Official Symbol | PJA1 |
| Official Full Name | Praja RING Finger Protein 1 |
| Gene ID | 5292 |
| Chromosomal Location | Xq28 |
| Protein | Praja1 E3 ubiquitin ligase |
| Alias | E3 ubiquitin-protein ligase Praja1, RNF34 |
The PJA1 gene encodes a RING-type E3 ubiquitin ligase characterized by:
Praja1 is primarily localized to the endoplasmic reticulum (ER) and performs several key functions:
Praja1 has been shown to ubiquitinate:[1:1]
| Protein | Disease Relevance |
|---|---|
| Tau | Alzheimer's disease, PSP, CBD, Pick's disease |
| TDP-43 | ALS, FTLD |
| SOD1 | Familial ALS |
| FUS | ALS |
| α-synuclein | Parkinson's disease |
| Huntingtin | Huntington's disease |
Aoki et al. demonstrated that Praja1 ubiquitinates and degrades hyperphosphorylated tau, a key molecule in tauopathies including:[1:2]
This finding positions Praja1 as a potential therapeutic target for enhancing tau clearance in CBS and related disorders.
Beyond tau, Praja1's ability to degrade multiple disease-causing proteins suggests broad neuroprotective potential:
Several single nucleotide polymorphisms (SNPs) have been identified in the PJA1 gene, though their functional significance in neurodegeneration remains under investigation.
While PJA1 mutations are not a major cause of familial neurodegeneration, reduced Praja1 activity may contribute to:
Given Praja1's broad substrate specificity for disease proteins, strategies to enhance its activity could provide therapeutic benefits:
| E3 Ligase | Primary Target | CBS Relevance |
|---|---|---|
| Praja1 | Tau, TDP-43, α-syn | Direct - targets 4R tau |
| Parkin (PRKN) | Mitochondrial proteins | Indirect - mitophagy |
| HUWE1 | MYC, p53 | Indirect - cell survival |
| SEL1L | CFTR, ERAD | Indirect - protein quality |
Watabe K et al. Praja1 E3 ubiquitin ligase and the role it plays in neurodegeneration. FEBS J (2025). 2025. ↩︎ ↩︎ ↩︎