Synaptotagmin-9 is a protein that in humans is encoded by the SYT9 gene. SYT9 has been shown to interact with SYNCRIP, TUBB and TRPV1. May be involved in Ca2+-dependent exocytosis of secretory vesicles through Ca2+ and phospholipid binding to the C2 domain or may serve as Ca2+ sensors in the process of vesicular trafficking and exocytosis.