May have a role in neuroendocrine differentiation. Monomer. 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. 2 isoforms of the human protein are produced by alternative splicing. Note: This description may include information from UniProtKB.