¶ CALCOCO2 — Calcium Binding and Coiled-Coil Domain 2
| Calcium Binding and Coiled-Coil Domain 2 |
|---|
| Gene Symbol | CALCOCO2 |
| Full Name | Calcium Binding and Coiled-Coil Domain 2 |
| Chromosome | 17q25.1 |
| NCBI Gene ID | [10241](https://www.ncbi.nlm.nih.gov/gene/10241) |
| OMIM | 604551 |
| Ensembl ID | ENSG00000136436 |
| UniProt ID | [Q9BQB6](https://www.uniprot.org/uniprot/Q9BQB6) |
| Aliases | NDP52, TAX1BP1, CALCOCO2 |
| Associated Diseases | [Alzheimer's Disease](/diseases/alzheimers-disease), [Parkinson's Disease](/diseases/parkinsons-disease), Inflammatory Disorders, Cancer |
CALCOCO2 (Calcium Binding and Coiled-Coil Domain 2), also known as NDP52 (Nuclear Dot Protein 52), is a selective autophagy receptor that plays critical roles in xenophagy, mitophagy, and aggrephagy. This protein is essential for recognizing and targeting ubiquitinated cargo for autophagic degradation, making it a key player in neurodegenerative disease pathogenesis.
The CALCOCO2 gene is located on chromosome 17q25.1 and encodes a 446-amino acid protein (52 kDa). The protein contains several functional domains:
- LC3-interacting region (LIR): Binds LC3/GABARAP family proteins
- Coiled-coil domain: Mediates homodimerization and interactions with autophagy proteins
- Skp2-binding domain: Regulates protein stability
CALCOCO2 functions as a selective autophagy receptor through its ability to recognize ubiquitinated cargo:
- Xenophagy: Recognition and elimination of intracellular pathogens including bacteria, viruses, and parasites
- Mitophagy: Selective degradation of damaged mitochondria via PINK1/Parkin-dependent pathway
- Aggrephagy: Clearance of protein aggregates
- Ferritinophagy: Iron homeostasis through ferritin degradation
CALCOCO2 recruits autophagosomes to target cargo through:
- Ubiquitin recognition: Binds K63-linked polyubiquitin chains on damaged organelles and aggregates
- LC3 interaction: LIR domain binds LC3/GABARAP on forming autophagosomes
- TBK1 phosphorylation: CALCOCO2 phosphorylation by TBK1 enhances its autophagy receptor function
- Cooperative binding: Works with other receptors like OPTN and SQSTM1
- LC3/GABARAP: Autophagosome membrane protein
- TBK1: Kinase that phosphorylates CALCOCO2
- OPTN: Co-operating autophagy receptor
- MyD88: Innate immune signaling adaptor
- TAX1BP1: Homologous protein with overlapping functions
In Alzheimer's disease, CALCOCO2 dysfunction contributes to:
- Mitophagy impairment: Reduced clearance of damaged mitochondria leads to oxidative stress
- Protein aggregate accumulation: Impaired aggrephagy contributes to amyloid and tau pathology
- Neuroinflammation: Dysregulated xenophagy affects microglial function
CALCOCO2 is particularly important in Parkinson's disease through:
- PINK1/Parkin mitophagy: CALCOCO2 is recruited to damaged mitochondria in a Parkin-dependent manner
- Alpha-synuclein clearance: Required for selective autophagy of alpha-synuclein aggregates
- Dopaminergic neuron protection: Maintains mitochondrial quality in substantia nigra neurons
- Regulates microglial autophagy in response to pathogens
- Controls inflammatory responses through NF-kappaB signaling
- Mutations affect immune cell function
CALCOCO2 is expressed in various tissues:
- High expression: Immune cells (macrophages, microglia, dendritic cells), epithelial cells
- Moderate expression: Brain, lung, liver
- Cellular localization: Cytoplasmic, associated with autophagosomes and endosomes
In the brain, CALCOCO2 is highly expressed in microglia where it plays crucial roles in clearance of pathogens and protein aggregates.
- Enhancing mitophagy: Small molecules that activate CALCOCO2-mediated mitophagy
- Gene therapy: Increasing CALCOCO2 expression in neurons
- TBK1 activators: Enhancing CALCOCO2 phosphorylation
- AD/PD: Boosting CALCOCO2 function may protect against neurodegeneration
- Cancer: CALCOCO2 can act as tumor suppressor; context determines therapeutic approach
- Inflammatory diseases: Modulating CALCOCO2 may regulate immune response