Bombesin and Analogs

Definition
Bombesin is a polypeptide that is found in the brain and gastrointestinal tract. Experimentally it has shown to cause the secretion of various substances (as gastrin and cholecystokinin) and to inhibit intestinal motility.

Discovery
Bombesin was isolated from the skin of the frog Bombina bonmina by Anastasi and team in 19711.

Classification
Bombesin-like peptides are grouped into three families - 1) Bombesin group, viz., bombesin and alytesin, 2) Ranatensin group viz., ranatensins, litorin, and Rohdei litorin, 3) Phyllolitorin group viz., Leu(8)- and Phe(8)-phyllolitorins.

Structural characteristics
Bombesin is a small peptide of 14 amino acids.

Mode of action
The biological activity of bombesin is mediated by binding to specific receptors viz., gastrin releasing peptide receptor (GRPR; called also BB2 receptor), neuromedin B receptor (NMBR; called also BB1 receptor) and bombesin receptor subtype 3 (BRS-3; called also BB3 receptor). Bombesin induce Ca2+ release from intracellular stores2.

Functions
Bombesin and bombesin-like factors show a wide spectrum of biological activities. It regulates the contraction of smooth muscle cells, induction of the secretion of neuropeptides and hormones. It is one of the most powerful substances showing anorexic effects in the hypothalamus. It induces the release of gastrin and cholecystokinin in the intestines and the pancreas. They also posses activities of cytokines.

References
1.Anastasi A, Erspamer V, Bucci M (1971). Isolation and structure of bombesin and alytesin, 2 analogous active peptides from the skin of the European amphibians Bombina and Alytes. Experientia., 27(2):166-167.
2. Wang JL, Kalyanaraman S, Vivo MD, Gautam N (1996). Bombesin and thrombin affect discrete pools of intracellular calcium through different G-proteins. Biochem J., 320:87-91.