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The Journal of Pharmacology and... Aug 2022Allosteric ligands of various G-protein-coupled receptors are being increasingly described and are providing important advances in the development of ligands with novel...
Allosteric ligands of various G-protein-coupled receptors are being increasingly described and are providing important advances in the development of ligands with novel selectivity and efficacy. These unusual properties allow expanded opportunities for pharmacologic studies and treatment. Unfortunately, no allosteric ligands are yet described for the bombesin receptor family (BnRs), which are proposed to be involved in numerous physiologic/pathophysiological processes in both the central nervous system and peripheral tissues. In this study, we investigate the possibility that the bombesin receptor subtype-3 (BRS-3) specific nonpeptide receptor agonist MK-5046 [(2S)-1,1,1-trifluoro-2-[4-(1H-pyrazol-1-yl)phenyl]-3-(4-[[1-(trifluoromethyl)cyclopropyl]methyl]-1H-imidazol-2-yl)propan-2-ol] functions as a BRS-3 allosteric receptor ligand. We find that in BRS-3 cells, MK-5046 only partially inhibits iodine-125 radionuclide (I)-Bantag-1 [Boc-Phe-His-4-amino-5-cyclohexyl-2,4,5-trideoxypentonyl-Leu-(3-dimethylamino) benzylamide N-methylammonium trifluoroacetate] binding and that both peptide-1 (a universal BnR-agonist) and MK-5046 activate phospholipase C; however, the specific BRS-3 peptide antagonist Bantag-1 inhibits the action of peptide-1 competitively, whereas for MK-5046 the inhibition is noncompetitive and yields a curvilinear Schild plot. Furthermore, MK-5046 shows other allosteric behaviors, including slowing dissociation of the BRS-3 receptor ligand I-Bantag-1, dose-inhibition curves being markedly affected by increasing ligand concentration, and MK-5046 leftward shifting the peptide-1 agonist dose-response curve. Lastly, receptor chimeric studies and site-directed mutagenesis provide evidence that MK-5046 and Bantag-1 have different binding sites determining their receptor high affinity/selectivity. These results provide evidence that MK-5046 is functioning as an allosteric agonist at the BRS-3 receptor, which is the first allosteric ligand described for this family of receptors. SIGNIFICANCE STATEMENT: G-protein-coupled receptor allosteric ligands providing higher selectivity, selective efficacy, and safety that cannot be obtained using usual orthosteric receptor-based strategies are being increasingly described, resulting in enhanced usefulness in exploring receptor function and in treatment. No allosteric ligands exist for any of the mammalian bombesin receptor (BnR) family. Here we provide evidence for the first such example of a BnR allosteric ligand by showing that MK-5046, a nonpeptide agonist for bombesin receptor subtype-3, is functioning as an allosteric agonist.
Topics: Animals; Bombesin; Imidazoles; Ligands; Mammals; Peptides; Pyrazoles; Receptors, Bombesin
PubMed: 35644465
DOI: 10.1124/jpet.121.001033 -
The American Review of Respiratory... Dec 1990Quiescent cultures of Swiss 3T3 cells can be stimulated to recommence DNA synthesis by polypeptide growth factors, neuropeptides, and various pharmacologic agents that... (Review)
Review
Quiescent cultures of Swiss 3T3 cells can be stimulated to recommence DNA synthesis by polypeptide growth factors, neuropeptides, and various pharmacologic agents that act via multiple signal transduction pathways. Neuropeptides of the bombesin family provide potent mitogens to elucidate these pathways. These peptides bind to specific receptors that have been characterized by radioligand binding and sensitivity to antagonists and identified as glycoproteins with a Mr of 75,000-85,000 by chemical cross-linking. After binding, bombesin elicits a cascade of early molecular events including stimulation of phosphorylation of the acidic Mr 80,000 cellular protein, which is a major substrate of protein kinase C; Ca2+ mobilization mediated by Ins(1,4,5)P3, Na+ and K+ fluxes, transmodulation of EGF receptor, enhancement of cAMP accumulation, and expression of the proto-oncogenes c-fos and c-myc. Studies using membrane preparations and permeabilized 3T3 cells indicate that G proteins play a role in the transduction of the mitogenic signal triggered by the binding of bombesin to its receptor. A pertussis toxin-insensitive G protein couples the bombesin receptor to the generation of a signal that activates protein kinase C, whereas a pertussis toxin-sensitive G protein mediates cross-talk between transmembrane signaling pathways. Bombesin-mediated mitogenesis can be blocked by different antagonists and by interrupting the signal-transduction process at various postreceptor levels. Thus, prolonged treatment with vasopressin causes heterologous desensitization to the mitogenic action of bombesin. This mitogenic block is mediated by uncoupling the receptor from its signaling system. Loss of responsiveness to bombesin-stimulated DNA synthesis is also induced by down-regulation of protein kinase C.(ABSTRACT TRUNCATED AT 250 WORDS)
Topics: Amino Acid Sequence; Animals; Bombesin; Calcium; Carcinoma, Small Cell; Cells, Cultured; Cyclic AMP; Humans; Lung Neoplasms; Mitosis; Molecular Sequence Data; Protein Kinase C; Proto-Oncogenes; Receptors, Bombesin; Receptors, Neurotransmitter; Signal Transduction
PubMed: 2174658
DOI: 10.1164/ajrccm/142.6_Pt_2.S11 -
Peptides Nov 2000Bombesin is the first peptide shown to act in the brain to influence gastric function and the most potent peptide to inhibit acid secretion when injected into the... (Review)
Review
Bombesin is the first peptide shown to act in the brain to influence gastric function and the most potent peptide to inhibit acid secretion when injected into the cerebrospinal fluid (CSF) in rats and dogs. Bombesin responsive sites include specific hypothalamic nuclei (paraventricular nucleus, preoptic area and anterior hypothalamus), the dorsal vagal complex as well as spinal sites at T9-T10. The antisecretory effect of central bombesin encompasses a variety of endocrine/paracrine (gastrin, histamine) or neuronal stimulants. Bombesin into the CSF induces an integrated gastric response (increase in bicarbonate, and mucus, inhibition of acid, pepsin, vagally mediated contractions) enhancing the resistance of the mucosa to injury through autonomic pathways. The physiological significance of central action of bombesin on gastric function is still to be unraveled.
Topics: Animals; Bombesin; Brain; Cell Nucleus; Cerebrospinal Fluid; Digestive System; Dogs; Gastric Mucosa; Hypothalamus; Mice; Models, Biological; Rats; Stomach Ulcer
PubMed: 11090915
DOI: 10.1016/s0196-9781(00)00293-x -
Current Opinion in Endocrinology,... Feb 2011This review will highlight recent advances in the understanding of mammalian bombesin receptor-related pathophysiological roles in disease states and new insights into... (Review)
Review
PURPOSE OF REVIEW
This review will highlight recent advances in the understanding of mammalian bombesin receptor-related pathophysiological roles in disease states and new insights into bombesin receptor pharmacology.
RECENT FINDINGS
Studies regarding bombesin-like peptides and mammalian bombesin receptor functions have demonstrated significant biological impact on a broad array of physiological and pathophysiological conditions. Pharmacological experiments in vitro and in vivo as well as utilization of genetic rodent models of the gastrin-releasing peptide receptor (GRP-R/BB2) and neuromedin B receptor (NMB-R/BB1) further delineated roles in memory and fear behavior, inhibition of tumor cell growth, mediating signals for pruritus and male reproductive behavior. All three mammalian bombesin receptors were shown to possess some role in the regulation of energy balance. Novel synthesis of selective high affinity agonists and antagonists of the orphan bombesin receptor subtype-3 (BRS-3/BB3) has been accomplished and will facilitate further studies using animal model systems.
SUMMARY
Mammalian bombesin receptors participate in the regulation of energy homeostasis and may represent an attractive target for pharmacological treatment of obesity and certain eating disorders. Novel pharmacological insights of bombesin-like peptides and the interaction with their respective receptors have been elucidated to aid future treatment and imaging of epithelial cell-derived tumors.
Topics: Animals; Bombesin; Hormone Antagonists; Humans; Male; Mammals; Metabolism; Peptide Hormones; Pharmaceutical Preparations; Receptors, Bombesin; Rodentia
PubMed: 21042212
DOI: 10.1097/MED.0b013e328340ff93 -
Annals of the New York Academy of... Mar 1996We have shown that in the central nervous system BN receptors are closely associated with 5-HT systems. On a subpopulation of dorsal raphe neurons, NMB receptors are... (Review)
Review
We have shown that in the central nervous system BN receptors are closely associated with 5-HT systems. On a subpopulation of dorsal raphe neurons, NMB receptors are able to depolarize cells by reducing gK+. In one of the target regions of the dorsal raphe 5-HT neurons, the SCN, we have also shown that neurons are excited by BN-related peptides. In the SCN, the GRP receptors excite neurons by two different mechanisms: closure of gK+ and opening of an unidentified cation conductance. Expression of human BN receptors from the brain in CHO cells or Xenopus oocytes shows a very similar pharmacological profile to that seen in the rat brain slice preparations. In the CHO cell line, following BN receptor activation, a major second-messenger path involves hydrolysis of PIP2 by phospholipases to yield IP3, which releases Ca2+ from intracellular stores. In the oocyte expression system, a similar second messenger pathway is clearly apparent, and Ca2+-sensitive gCl- represents the last phase in a cascade of events. The final phase of the mechanism of action in the artificial systems does not involve gK+, suggesting a different second messenger cascade to that in neurons. However, the involvement of phospholipases and their phospholipid products have not been excluded in neurons.
Topics: Amino Acid Sequence; Animals; Bombesin; Brain; Consensus Sequence; Humans; Molecular Sequence Data; Neurons; Oligopeptides; Pyrrolidonecarboxylic Acid; Raphe Nuclei; Receptors, Bombesin; Serotonin; Structure-Activity Relationship
PubMed: 8602736
DOI: 10.1111/j.1749-6632.1996.tb15126.x -
Annals of Medicine Nov 2000Bombesin (BN)-like peptides and receptors for these peptides are widely distributed in mammalian peripheral tissues and the central nervous system. The physiological and... (Review)
Review
Bombesin (BN)-like peptides and receptors for these peptides are widely distributed in mammalian peripheral tissues and the central nervous system. The physiological and behavioural functions of these peptides have been clarified by both in vivo and in vitro studies. In spite of intensive investigations, the functions of endogenous BN-like peptides remain unclear. In order to specify these functions, our group and another laboratory generated by gene targeting mutant mice that lack one of the three BN-like peptide receptors found in mammals, ie neuromedin B receptor (NMB-R; BB1), gastrin-releasing peptide receptor (GRP-R; BB2), or bombesin receptor subtype-3 (BRS-3; BB3). Using these mutant mouse, we have found unexpected phenotypes, such as hyperphagia and obesity in the BRS-3-deficient mouse, and abnormal social behaviour in the GRP-R-deficient mouse. In the present study, we present our most recent findings in addition to previous studies and discuss the functions of BN-like peptides related to feeding and social behaviour from the point of view of knock-out mice studies.
Topics: Animals; Bombesin; Eating; Feeding Behavior; Male; Mice; Mice, Knockout; Phenotype; Receptor, Bradykinin B2; Receptors, Bombesin; Receptors, Bradykinin; Social Behavior
PubMed: 11127929
DOI: 10.3109/07853890008998831 -
Current Opinion in Endocrinology,... Feb 2008Mammalian bombesin-related peptides, gastrin-releasing peptide and neuromedin B actions are mediated by two receptors (BB1-receptor, BB2-receptor), which are closely... (Review)
Review
PURPOSE OF REVIEW
Mammalian bombesin-related peptides, gastrin-releasing peptide and neuromedin B actions are mediated by two receptors (BB1-receptor, BB2-receptor), which are closely related to the orphan receptor BRS-3 (BB3-receptor). The purpose of this review is to highlight advances in the understanding of these peptides in physiology/disease states.
RECENT FINDINGS
Pharmacologic/receptor-knockout studies show involvement of these receptors in a number of new processes/diseases. Neuromedin B/BB1-receptor is an important physiological regulator of pituitary-thyroid function; in mediating behavior, especially feas/anxiety; in mediating satiety through different cascades than gastrin-releasing peptide/BB2 receptors and for its autocrine tumor-growth effects. Gastrin-releasing peptide/BB2-receptor plays important roles in mediating signals for pruritus, lung development/injury, small intestinal mucosal defense, and central nervous system processes such as learning/memory. The signaling mechanisms of its potent growth effects are being elucidated and their possible therapeutic targets identified. BB3-receptor knockout mice provided insights for their obesity/glucose intolerance and demonstrated that this receptor may be important in the lung response to injury, tumor growth and gastrointestinal motility. Each receptor is frequently overexpressed in human tumors and has potent growth effects. This effect is being explored to develop new antitumor treatments, such as bombesin-receptor ligands conjugated to cytotoxic agents.
SUMMARY
This receptor family is involved in an increasing number of central nervous system/peripheral processes physiologically and in disease states, and increased understanding of its role may lead to novel treatments.
Topics: Animals; Antineoplastic Agents; Bombesin; Cell Proliferation; Humans; Neoplasms; Peptide Fragments; Receptors, Bombesin
PubMed: 18185064
DOI: 10.1097/MED.0b013e3282f3709b -
Brain, Behavior, and Immunity Dec 1988In recent years, a remarkable advance has been made in identifying the extracellular factors that control cell proliferation in a variety of cells. Bombesin-like... (Review)
Review
In recent years, a remarkable advance has been made in identifying the extracellular factors that control cell proliferation in a variety of cells. Bombesin-like peptides (BN-LP) are neuropeptides involved in the regulation of many important functions, including sensory transmission, regulation of central autonomic pathways, thermoregulation, pituitary, gastric, and pancreatic secretion, food intake, and satiety. They also may stimulate cellular proliferation in a developmental and tissue-specific manner. Their role in pathogenesis appears to be related to their properties as growth factors, especially in the lung, where BN-LP are proposed to induce growth of normal and neoplastic epithelial cells. The formulated hypothesis of control of SCLC growth by BN-LP will be tested using specific synthetic BN antagonists. Neuronal modulation of the release of BN-LP from neuroepithelial bodies and paracrine effects of BN-LP as sensory neurotransmitters indicate possible pathways of nervous system involvement in tissue development, proliferation, and differentiation, as well as repair processes and wound healing.
Topics: Animals; Bombesin; Mitogens; Neuropeptides
PubMed: 3076479
DOI: 10.1016/0889-1591(88)90032-3 -
The International Journal of... 2005Amphibian bombesin and its related peptides consist a family of neuropeptides in many vertebrate species. Bombesin and two major bombesin-like peptide in mammals,... (Review)
Review
Amphibian bombesin and its related peptides consist a family of neuropeptides in many vertebrate species. Bombesin and two major bombesin-like peptide in mammals, gastrin-releasing peptide (GRP) and neuromedin B (NMB), have been shown to elicit various physiological effects. These include inhibition of feeding, smooth muscle contraction, exocrine and endocrine secretions, thermoregulation, blood pressure and sucrose regulations and cell growth. Receptors for GRP and NMB (GRP-R and NMB-R), as well as third subtype of bombesin-like peptide receptor (BRS-3) have been cloned. These receptors are G-protein-coupled receptors and are expressed in various brain regions and in the digestive tract. In this paper, we will summarize studies on these peptides and their receptors, with special reference to research using gene-knockout mice. These studies clearly demonstrated the role of three receptors in vivo and in vitro. We will also discuss the phylogeny of these receptors.
Topics: Amino Acid Sequence; Amphibians; Animals; Bombesin; Brain Chemistry; Chickens; Cloning, Molecular; Conserved Sequence; Humans; Mice; Molecular Sequence Data; Rats; Receptors, Bombesin; Sequence Alignment; Sequence Homology, Amino Acid
PubMed: 15906244
DOI: 10.1387/ijdb.041954ho -
Annals of the New York Academy of... Oct 1994
Review
Topics: Afferent Pathways; Animals; Bombesin; Brain; Cerebral Ventricles; Electrophysiology; Feeding Behavior; Humans; Mouth
PubMed: 7832466
DOI: 10.1111/j.1749-6632.1994.tb19814.x