Synaptotagmiinin

Synaptotagmiinin is likely a misspelling of synaptotagmin, the family of calcium-sensing proteins that regulate neurotransmitter release at chemical synapses. The synaptotagmin family comprises several isoforms, most notably synaptotagmin I (Syt1) and II (Syt2), with additional members such as Syt7, Syt9, and others expressed in neurons and other secretory cells.

These are type I membrane proteins anchored in synaptic vesicles by a single transmembrane domain, with a relatively short luminal N-terminus and a cytoplasmic C-terminus containing two C2 domains (C2A and C2B) that bind calcium and phospholipids. The C2 domains mediate interactions with phospholipid membranes and other proteins in a calcium-dependent manner.

Calcium binding induces conformational changes that promote interaction with SNARE proteins (syntaxin-1, SNAP25, synaptobrevin/VAMP2) and trigger rapid, synchronous neurotransmitter release. In addition to triggering fusion, synaptotagmins participate in vesicle priming and, in some isoforms, endocytosis and trafficking events that modulate release probability and kinetics.

Isoform-specific differences in calcium sensitivity, binding partners, and tissue distribution underlie distinct roles in neurotransmission and other secretory processes. In research, genetic knockouts and mutations in synaptotagmins affect evoked release and synaptic plasticity, highlighting their essential role in fast neurotransmission and their interest as potential targets for modulating synaptic function.