SNAP91 (Synaptosomal‑Associated Protein 91)
Gene and Protein
- Gene symbol: SNAP91
- Full name: Synaptosomal‑Associated Protein 91
- Encoded protein: AP180 (also called clathrin assembly protein AP180)
- Chromosomal location (human): 7p21.3
Protein characteristics
- AP180 is a neuronal adaptor protein that participates in clathrin‑mediated endocytosis.
- The protein contains an N‑terminal ANTH (AP180 N‑terminal homology) domain that binds phosphatidylinositol‑4,5‑bisphosphate (PI(4,5)P₂) on the plasma membrane.
- The C‑terminal region is rich in clathrin‑binding motifs and facilitates the assembly of clathrin coats on budding vesicles.
Biological function
- AP180 regulates the size and number of synaptic vesicles by mediating the recruitment of clathrin to sites of vesicle retrieval at presynaptic terminals.
- It cooperates with other endocytic proteins such as dynamin, adaptor protein complex 2 (AP‑2), and synaptophysin during synaptic vesicle recycling.
- In non‑neuronal cells, AP180 can promote clathrin coat formation on endocytic vesicles, although its expression is highest in brain tissue.
Expression profile
- RNA and protein expression are predominant in the central nervous system, particularly in the cerebral cortex, hippocampus, and cerebellum.
- Lower levels have been detected in peripheral tissues, reflecting a primarily neuronal role.
Model organisms and research relevance
- The Drosophila melanogaster ortholog of SNAP91 (also named AP180) has been used to study clathrin‑mediated endocytosis and synaptic function.
- Mouse knockout studies indicate that loss of Snap91 leads to defects in synaptic vesicle recycling and altered neurotransmission, underscoring its essential role in neuronal physiology.
Clinical and biomedical significance
- To date, no definitive disease‑causing mutations in SNAP91 have been established in human genetic studies.
- Some large‑scale genomic analyses have reported rare variants of uncertain significance in individuals with neurodevelopmental phenotypes, but causal relationships remain unconfirmed.
References and sources
- UniProtKB entry Q9UPI3 (human SNAP91).
- NCBI Gene database entry for SNAP91 (Gene ID: 10686).
- Primary literature describing AP180 function in clathrin‑mediated endocytosis (e.g., Ford et al., Nature, 2002; Mishra et al., J. Neurosci., 2008).
This summary reflects information available from peer‑reviewed scientific databases and literature as of the knowledge cut‑off date.
