May have a role in neuroendocrine differentiation. Monomer. Interacts with SH3RF2 (By similarity). Additional isoforms seem to exist. Found within the stromal cells in close contact to the vascular structure of placental villi, yolk sac, fetal liver, adrenal cortex and pancreas and in the beta cells of the islets of Langerhans in the adult pancreas. Found also in some forms of neuroendocrine lung tumor tissue. N- and O-glycosylated. O-glycosylated with core 1 or possibly core 8 glycans.