Predominantly cytoplasmic. A small proportion is associated with secretory granules and membrane fractions (By similarity). Detectable in human serum after ischemic neuronal damage. Expressed at high levels in the pancreatic islets of Langerhans and to a much lesser extent in the gastrointestinal tract (stomach, small intestine and colon), the adrenal medulla and cortex and the thyroid C-cells. In the brain, the expression is restricted to distinct subtypes of neurons with highest expression in the molecular layer of the cerebellum (stellate and basket cells), in the anterior part of the pituitary gland, in the thalamus, in the hypothalamus and in a subgroup of neocortical neurons.