Chromogranin

The chromogranin/secretogranin (granins) are a family of regulated secretory proteins ubiquitously found in the cores of amine and peptide hormone and neurotransmitter dense-core secretory vesicles, and consist of several independent proteins:


 * chromogranin A (CgA)
 * chromogranin B (CgB)
 * secretogranin II (SgII) (see also secretoneurin)

Four other proteins (secretogranin III-VI) are also proposed to belong to the granins on the basis of their physico-chemical properties.

Granins function as pro-hormones, giving rise to an array of peptide fragments for which autocrine, paracrine, and endocrine activities have been demonstrated in vitro and in vivo.

The intracellular biochemistry of granins includes binding of Ca2+, ATP and catecholamines (epinephrine, norepinephrine) within the hormone storage vesicle core.

There is evidence that CgA, and perhaps other granins, regulate the biogenesis of dense-core secretory vesicles in neuroendocrine cells.