Bombesinlike

Bombesin-like peptides are a family of neuropeptides that resemble bombesin, a peptide originally isolated from amphibian skin. In mammals, the best-characterized members are gastrin-releasing peptide (GRP) and neuromedin B (NMB). They share a common C-terminal motif and activate a set of bombesin receptors, including GRPR (gastrin-releasing peptide receptor, BB2) and NMBR (neuromedin B receptor, BB1); a third receptor, BRS-3 (bombesin receptor subtype-3), is considered orphan with respect to a clearly defined endogenous ligand.

These peptides are widely distributed in the central nervous system and peripheral tissues. Their signaling is mediated by G protein-coupled receptors. GRP binds predominantly to GRPR, while NMB binds to NMBR; BRS-3 may respond to various ligands and is thought to have physiological roles that are not entirely overlapped with GRPR or NMBR functions.

Physiological roles of bombesin-like peptides are diverse and include regulation of gastric acid and pancreatic secretions, modulation of gastrointestinal motility, and control of feeding and energy balance. They also participate in neuroendocrine signaling, locomotor and learning processes, and nociception. In the brain, they influence cognitive and emotional processes, while in peripheral tissues they influence secretory and motor functions.

Clinically, bombesin-like signaling is relevant in oncology. Many neuroendocrine tumors and small cell lung carcinomas overexpress bombesin receptors, particularly GRPR, making receptor-targeted imaging and therapy an area of investigation. Antagonists and radiolabeled ligands are studied for diagnostic and therapeutic applications.

Terminology: the term “bombesin-like” emphasizes similarity to bombesin in receptor activation and sequence, encompassing GRP, NMB, and related amphibian and mammalian peptides.