Required for depolarization-dependent survival of cultured cerebellar granule neurons. May mediate homophilic as well as heterophilic cell-cell interaction with AMIGO1 or AMIGO3. May contribute to signal transduction through its intracellular domain. May be required for tumorigenesis of a subset of gastric adenocarcinomas. Binds itself as well as AMIGO1 and AMIGO3. Associated with nucleus as well as plasma membrane. Restricted to somata of cerebellar as well as hippocampal neurons (By similarity). Highest levels in breast, ovary, cervix, and uterus. Lower levels in lung, colon, and rectum. Differentially expressed in 56% of thyroid, 57% of pancreatic and 45% of stomach cancers. Belongs to the immunoglobulin superfamily. AMIGO family.