Acts as a negative regulator of SRC by activating CSK which inhibits SRC activity and downstream signaling, leading to impaired cell spreading and migration. Regulates dendritic spine morphology. Involved in calcium-dependent exocytosis. May play a role in neurotransmitter release or synapse maintenance. Interacts with the N-terminal coiled-coil region of SNAP25. Interacts with BCAR1/p130Cas and SRC through its C-terminal domain. Interacts with CSK, CTTN, SORBS3/vinexin, SYP and MAPRE3/EB3. Expressed in some primary breast carcinomas where its presence is significantly associated with increased tumor size. Not detected in normal breast tissue. Belongs to the SRCIN1 family. 4 isoforms of the human protein are produced by alternative splicing. Note: This description may include information from UniProtKB.