The glucagon-like peptide 1 receptor (GLP-1R) belongs to a distinct subgroup of G protein-coupled peptide hormone receptors (class B) that has been difficult to target by small molecule drugs. Here, we report that a non-peptide compound, T-0632, binds with micromolar affinity to the human GLP-1R and blocks GLP-1-induced cAMP production. Furthermore, the observation that T-0632 has almost 100-fold selectivity for the human versus the highly homologous rat GLP-1R provided an opportunity to map determinants of non-peptide binding. Radioligand competition experiments utilizing a series of chimeric human/rat GLP-1R constructs revealed that partial substitution of the amino terminus of the rat GLP-1R with the corresponding sequence from the human homolog was sufficient to confer high T-0632 affinity. Follow-up analysis of receptors where individual candidate amino acids had been exchanged between the human and rat GLP-1Rs identified a single residue that explained species selectivity of non-peptide binding. Replacement of tryptophan 33 in the human GLP-1R by serine (the homologous amino acid in the rat GLP-1R) resulted in a 100-fold loss of T-0632 affinity, whereas the converse mutation in the rat GLP-1R led to a reciprocal gain-of-function phenotype. These observations suggest that in a class B receptor, important determinants of non-peptide affinity reside within the extracellular amino-terminal domain. Compound T-0632 may mimic, and thereby interfere with, the putative "pseudo-tethering" mechanism by which the amino terminus of class B receptors initiates the binding of cognate hormones.

Background: We and others have described increased expression ofCOX-2 in H. pylori-infected tissues and cells.Production of the main COX-2 product, PGE z, is relatively low in epithelial cell lines, compared with that produced by monocytic cells.COX-2 overexpression is linked to GI carcinogenesis by its inhibition of epithelial apoptosis.We have demonstrated that addition of PGE z effectively inhibits H. pylori-stimulated apoptosis in gastric epithelial AGS cells.Aim: To determine if H. pyloristimulated gastric epithelial cells can produce sufficient levels of PGE z by the COX-2 pathway to alter cellular events such as apoptosis.Methods and Results: We screened a variety of gastric cancer cell lines for PGE z production in response to whole or lysed H. pylori.AGS, MKN-28, and KATOm cells all produced very low levels of PGE z of < 0.2 ngl10 6 cells

BACKGROUND & AIMS.Raised plasma gastrin secondary to achlorhydria is associated with increased expression of several genes in ECL cells, notably histidine decarboxylase (HDC) and vesicular monoamine transporter type 2 (VMAT2).It is not clear whether endogenous gastrin regulates expression of these genes when gastric acid secretion is uninhibited.We have examined expression of these genes in ECL cells in INS-GAS transgenic mice that express the coding sequence of the human gastrin gene in pancreatic 13-cells and in which parietal cell function is uninhibited.METHODS.Plasma gastrin was measured by radioimmunoassay using antibody L2 (COOH-terminal specific for amidated gastrins) and L6 (specific for human G17).Gastrin release from 13-cells was stimulated by oral glucose.ECL cell function was assessed by Northem analysis of HDC and VMAT2 mRNAs.RESULTS.In INS-GAS mice fasted for 6hr, plasma human G17 was 67-+ 11 pM.When fasted mice were then allowed access to 20% glucose, plasma human G17 significantly increased (30min, 242 ± 33; 120min, 133 _+ 19 pM; n = 6; both p<0.01).Following glucose, corpus VMAT2 and HDC mRNA abundances increased to 119--.6% and 147 ± 14%, relative to control (both p<0.05), respectively.In INS-GAS mice fed ab libitum with access to 20% glucose for 5 days, plasma gastrin was 283 ± 50 pM compared with 85 ± 29 pM in control INS-GAS mice (n = 6, p<0.01).Moreover, in INS-GAS mice with access to glucose for 5 days, VMAT2 mRNA abundance was increased by 255 ± 28% and HDC mRNA by 163 + 24% compared to INS-GAS mice fed ad libitum (both p<0.05).In wild type mice, human G17 was not detected in the plasma, and access to glucose did not influence plasma amidated, ie antral, gastrin (control, 82 ± 18: glucose, 86 ± I0 pM); neither did glucose influence HDC (control, 100 ± 18; glucose, 111 ± 8%) and VMAT2 (control, 100 ± 9; glucose, 95 ± 8%) mRNA abundances.CONCLUSIONS.1. Oral glucose stimulates human G17 release in INS-GAS mice, but has no effect on antral gastrin release.2. Moderate hypergastrinemia is associated with increases in HDC and VMAT2 mRNA in gastric corpus.3. Hypergastrinemia-induced expression of HDC and VMAT2 in ECL ceils does not depend on achlorhydria.