Gastrin-releasing peptideGRP, is a neuropeptide, a regulatory molecule encoded in the human by the GRPgene. GRP has been implicated in a number of physiological and pathophysiological processes. Most notably, GRP stimulates the release of gastrin from the G cells of the stomach.
GRP encodes a number of bombesin-like peptides.[5][6][7][8] Its 148-amino acidpreproprotein, following cleavage of a signal peptide, is further processed to produce either the 27-amino acid gastrin-releasing peptide or the 10-amino acid neuromedin C.[9] These smaller peptides regulate numerous functions of the gastrointestinal and central nervous systems, including release of gastrointestinal hormones, smooth muscle cell contraction, and epithelial cell proliferation.[5]
Gastrin-releasing peptide is a regulatory human peptide that elicits gastrin release and regulates gastric acid secretion and enteric motor function.[10] The post-ganglionic fibers of the vagus nerve that innervate bombesin/GRP neurons of the stomach release GRP, which stimulates the G cells to release gastrin.
Furthermore, GRP seems to mediate certain aspects of stress. This is the reason for the observed fact that atropine does not block the vagal effect on gastrin release.
GRP is located on chromosome 18q21. PreproGRP (the unprocessed form of GRP) is encoded in three exons separated by two introns.[8]Alternative splicing results in multiple transcript variants encoding different isoforms.[5]
PreproGRP begins with signal peptidase cleavage to generate the pro-gastrin-releasing-peptide (proGRP), which is then processed by proteolytic cleavages, to form smaller GRP peptides.[10]
These smaller peptides are released by the post-ganglionic fibers of the vagus nerve, which innervate the G cells of the stomach and stimulate them to release gastrin. GRP regulates numerous functions of the gastrointestinal and central nervous systems, including release of gastrointestinal hormones, smooth muscle cell contraction, and epithelial cell proliferation.[10]
Gastrin-releasing peptide and neuromedin C, it is postulated, play a role in human cancers of the lung, colon, stomach, pancreas, breast, and prostate.[5]
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