Gastrin-releasing peptide GRP, is a neuropeptide, a regulatory molecule encoded in the human by the GRP gene. 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. Its 148-amino acid preproprotein, 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. 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. 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.
GRP is also involved in the biology of the circadian system, playing a role in the signaling of light to the master circadian oscillator in the suprachiasmatic nuclei of the hypothalamus.
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.
Clinical significance
Gastrin-releasing peptide and neuromedin C, it is postulated, play a role in human cancers of the lung, colon, stomach, pancreas, breast, and prostate.