Chromogranin A

Chromogranin A or parathyroid secretory protein 1 (gene name CHGA) is a member of the is_associated_with::granin family of neuroendocrine secretory proteins, i.e., it is located in secretory vesicles of neurons and endocrine cells such as islet beta cell secretory granules in pancreas. In humans, chromogranin A is_associated_with::protein is encoded by the CHGA is_associated_with::gene.

Tissue distribution
Examples of cells producing chromogranin A (ChgA) are chromaffin cells of the is_associated_with::adrenal medulla, is_associated_with::paraganglia, is_associated_with::enterochromaffin-like cells and is_associated_with::beta cells of the pancreas. It is present in islet beta cell secretory granules.

Function
Chromogranin A is the precursor to several functional peptides including vasostatin-1, vasostatin-2, pancreastatin, catestatin and parastatin. These peptides negatively modulate the neuroendocrine function of the releasing cell (is_associated_with::autocrine) or nearby cells (is_associated_with::paracrine).

Chromogranin A induces and promotes the generation of is_associated_with::secretory granules such as those containing is_associated_with::insulin in pancreatic islet beta cells.

Clinical significance
Chromogranin A is elevated in is_associated_with::pheochromocytomas. It has been identified as autoantigen in type 1 diabetes. A peptide fragment of ChgA located in the Vasostatin-1, namely ChgA29-42 has been identified as the antigenic epitope recognized by diabetogenic BDC2.5 T cells from type 1 diabetes prone NOD mice.

It is used as an indicator for pancreas and is_associated_with::prostate cancer and in is_associated_with::carcinoid syndrome. It might play a role in early neoplasic progression. Chromogranin A is cleaved by an endogenous prohormone convertase to produce several peptide fragments. See chromogranin A GeneRIFs for references. In is_associated_with::immunohistochemistry it can be used to identify a range of neuroendocrine tumours and is highly specific for both benign and malignant cells of this type.