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 (By similarity). 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 (By similarity). Localized to the perinuclear region, lamellopodia, cortical actin and actin stress fibers but not to focal adhesions. Strongly expressed in axons and dendrites of the CA1 and CA3 hippocampal regions and of the dentate gyrus. Detected in both presynapses and postsynapses and enriched in postsynaptic density fractions. Expressed predominantly in central nervous system with high levels detected in cortex, cerebellum, midbrain and spinal cord (at protein level). Also expressed in testis and epithelial-rich tissues such as mammary gland, lung and kidney. Tyrosine-phosphorylated in response to EGF and to cell adhesion to integrin ligands. Belongs to the SRCIN1 family.