Synaptotagmin IX (SYT9)

Syt9 was expressed in brain, but not in other organs. Within brain, expression was detected in the limbic system, including hypothalamus, bed nucleus of stria terminalis, septal area, and medial amygdala, and in the basal ganglia, including putamen, nucleus accumbens, and pars reticulata of the substantia nigra. Syt9 was also expressed in the plexiform layer of the main olfactory bulb and the mitral cell layer of accessory olfactory bulb.Syt9 colocalized with internalized transferrin (TF) in perinuclear structures in a rat basophilic leukemia cell line, with faint staining of the plasma membrane and peripheral vesicles. Syt9 mediated fast synaptic transmission and fast synchronous neurotransmitter release. Syt9 functioned as a calcium sensor with kinetics and calcium sensitivity different than those of Syt1 and Syt2.