Gastrin-releasing peptide

Gene

GRP is located on chromosome 18q21. PreproGRP (the unprocessed form of GRP) is encoded in three exons separated by two introns. Alternative splicing results in multiple transcript variants encoding different isoforms.

Synthesis

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.

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.

Function

Gastrin-releasing peptide is a regulatory human peptide that elicits gastrin release and regulates gastric acid secretion and enteric motor function. 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.

References

References

1. "Entrez Gene: GRP gastrin-releasing peptide".
2. (September 1984). "Cloning and characterization of cDNAs encoding human gastrin-releasing peptide". Proceedings of the National Academy of Sciences of the United States of America.
3. (January 1986). "Two prohormones for gastrin-releasing peptide are encoded by two mRNAs differing by 19 nucleotides". Proceedings of the National Academy of Sciences of the United States of America.
4. (January 1987). "Human gastrin-releasing peptide gene maps to chromosome band 18q21". Somatic Cell and Molecular Genetics.
5. "Neuromedin C".
6. (October 1999). "Role of bombesin-related peptides in the control of food intake". Neuropeptides.
7. (March 2005). "Orchestrating time: arrangements of the brain circadian clock". Trends in Neurosciences.