Synaptotagmin family member which does not bind Ca(2+) (PubMed:23999003) (By similarity). Involved in neuronal dense core vesicles (DCVs) mobility through its interaction with KIF1A. Upon increased neuronal activity, phosphorylation by MAPK8/JNK1 destabilizes the interaction with KIF1A and captures DCVs to synapses (By similarity). Plays a role in dendrite formation by melanocytes (PubMed:23999003). Interacts with KIF1A; the interaction increases in presence of calcium and decreases when SYT4 is phosphorylated at Ser-135. Expressed in melanocytes (PubMed:23999003). Expressed in brain. Within brain, expression is highest in hippocampus, with substantial levels also detected in amygdala and thalamus (PubMed:23999003). Unlike in other synaptotagmin family members, the first C2 domain/C2A does not bind Ca(2+) neither mediates Ca(2+)-dependent phospholipid binding. An aspartate-to-serine substitution in this domain inactivates Ca(2+)/phospho-lipid binding. Phosphorylation at Ser-135 by MAPK8/JNK1 reduces interaction with KIF1A and neuronal dense core vesicles mobility. Belongs to the synaptotagmin family. Extended N-terminus.