Synaptosomal-associated protein 25 kDa (SNAP-25)

Synaptosomal-associated protein 25 kDa (SNAP‑25) is a presynaptic plasma membrane–associated t-SNARE/Q-SNARE protein encoded by the *SNAP25* gene on chromosome 20p12.2 in humans. It is a core component of the SNARE complex that mediates synaptic vesicle docking and Ca²⁺‑triggered fusion with the presynaptic membrane during neurotransmitter release. The SNARE complex consists of four α-helices—two contributed by SNAP‑25 and one each from syntaxin‑1 and synaptobrevin/VAMP2—which assemble into a coiled-coil structure to drive membrane fusion. SNAP‑25 is palmitoylated for membrane association but lacks a transmembrane domain.\n\nTwo main isoforms exist due to alternative splicing—SNAP‑25a (embryonic) and SNAP‑25b (postnatal/adult)—with distinct roles in secretion dynamics. Genetic ablation or proteolytic cleavage by botulinum toxins abolishes fast synaptic transmission. Beyond its central role in exocytosis at neuronal synapses, SNAP‑25 also influences postsynaptic receptor trafficking, dendritic spine morphology/density, neuronal development/plasticity, metabolism regulation outside the nervous system, and has been implicated in several neurological/psychiatric diseases including ADHD, schizophrenia, bipolar disorder, epilepsy, Alzheimer’s disease as well as learning disabilities.

Other names

Synaptosome associated protein 25t-SNAREQ-SNARESuP (super protein)SNAP25aSNAP25b

Cleavage/inhibition by botulinum neurotoxins blocks SNARE complex formation and exocytosis of neurotransmitters leading to neuroparalysis