| Piccolo Protein | |
|---|---|
| Gene | PCLO |
| UniProt | Q9Y5J3 |
| PDB | N/A (large scaffold protein) |
| Mol. Weight | 550 kDa |
| Localization | Presynaptic active zone, cytoplasm |
| Family | Active zone protein family |
| Diseases | Parkinson's Disease, Alzheimer's Disease, Schizophrenia |
Piccolo (also known as Aczonin) is one of the largest synaptic proteins, functioning as a crucial scaffolding molecule at the presynaptic active zone[^1]. The name derives from the Italian for "little horn," reflecting its originally observed expression pattern in the cochlea[^2].
The PCLO gene encodes a protein of approximately 5,200 amino acids, making it one of the largest proteins in the nervous system. It is expressed specifically in presynaptic terminals throughout the brain, with highest expression in the hippocampus and cerebral cortex[^3].
Piccolo is an extremely large, multi-domain protein:
The N-terminal region contains unique domains involved in protein-protein interactions at the active zone.
Multiple PDZ domains throughout the protein mediate interactions with various synaptic proteins, including ion channels and other scaffolding molecules.
The C-terminal region contains binding sites for Bassoon, RIM, and components of the synaptic vesicle release machinery[^4].
Piccolo serves as a major scaffolding protein at the presynaptic active zone:
Piccolo helps organize the reserve pool of synaptic vesicles and participates in regulating the transitions between different vesicle pools[^5].
Through interactions with the actin cytoskeleton, Piccolo helps maintain the structural integrity of presynaptic terminals[^6].
Piccolo expression is altered in Alzheimer's disease brains, and it may play a role in the synaptic dysfunction induced by amyloid-beta oligomers[^7].
Changes in Piccolo have been documented in dopaminergic synapses in PD models, suggesting a role in the synaptic pathology of PD[^8].
Genome-wide association studies have identified PCLO as a risk gene for schizophrenia, implicating synaptic dysfunction in this psychiatric disorder[^9].
Therapeutic strategies include: