| Bassoon Protein | |
|---|---|
| Gene | BSN |
| UniProt | O75786 |
| PDB | N/A (large scaffold protein) |
| Mol. Weight | 420 kDa |
| Localization | Presynaptic active zone, synaptic ribbons (retina) |
| Family | Active zone protein family |
| Diseases | Parkinson's Disease, Alzheimer's Disease, Epilepsy |
Bassoon is one of the largest known synaptic proteins, functioning as a critical scaffolding molecule at the presynaptic active zone[^1]. Named after its bovine homolog (bovine synaptic novel protein, Bsn), Bassoon is essential for organizing the presynaptic release machinery and maintaining synaptic vesicle pools[^2].
The BSN gene encodes a protein of approximately 3,900 amino acids, making it one of the largest synaptic proteins identified. It is expressed predominantly in the brain, particularly in hippocampal mossy fiber synapses and cortical synapses[^3].
Bassoon is an extremely large, multi-domain scaffolding protein:
The N-terminal region contains zinc-finger motifs that mediate interactions with other active zone proteins and may be involved in synaptic targeting.
Multiple extended coiled-coil domains form the backbone of the protein, allowing it to function as a molecular scaffold that bridges different active zone components.
The C-terminal region contains PDZ domains that bind to various synaptic proteins, including voltage-gated calcium channels and other active zone scaffolds[^4].
Bassoon plays a central role in organizing the cytomatrix of the active zone (CAZ):
In retinal photoreceptor cells and bipolar cells, Bassoon is a core component of synaptic ribbons—specialized electron-dense structures that tether synaptic vesicles for rapid, tonic release[^5].
Bassoon directly interacts with voltage-gated calcium channels (Cav2.1 and Cav2.2), helping to position them near release sites[^6].
Alzheimer's disease is associated with synaptic dysfunction that precedes neuronal loss. Bassoon levels are altered in AD brains, and the protein may be involved in the synaptic effects of amyloid-beta toxicity[^7].
Changes in presynaptic protein expression, including Bassoon, have been documented in PD models and patients, contributing to dopaminergic synaptic dysfunction[^8].
Given its critical role in synaptic transmission, Bassoon dysfunction has been linked to epileptogenesis. Mutations in BSN have been associated with certain forms of epilepsy in animal models[^9].
Therapeutic strategies related to Bassoon include: