Synaptotagmin-4 (SYT4) belongs to the synaptotagmin family, which is a group of membrane-trafficking proteins that contain two C-terminal C2 domains. Most of the synaptotagmins have a unique N-terminal domain that is involved in membrane anchoring or specific ligand binding. This entry represents SYT4 from chordates. SYT4 is a Ca2+-sensor in the fly but not in the rat []. Like all synaptotagmins, SYT4 contains the highly conserved C2A and C2B calcium-binding domains, but an amino acid substitution found in the C2A domain decreases SYT4's affinity for calcium under some conditions [, ]. In adult hypothalamic oxytocin neurons, SYT4 is specifically induced by high-fat diet, and this negatively regulates oxytocin exocytosis, which is associated with obesity []. In humans the SYT4 gene is localised to a locus linked to schizophrenia and bipolar disorder [].
