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Göke R, Larsen PJ, Mikkelsen JD, Sheikh SP. Distribution of GLP-1 binding sites in the rat brain: evidence that exendin-4 is a ligand of brain GLP-1 binding sites. Eur J Neurosci 1995; 7:2294-300. [PMID: 8563978 DOI: 10.1111/j.1460-9568.1995.tb00650.x] [Citation(s) in RCA: 351] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The distribution and biochemical properties of glucagon-like peptide (GLP)-1(7-36) amide (GLP-1) binding sites in the rat brain were investigated. By receptor autoradiography of tissue sections, the highest densities of [125I]GLP-1 binding sites were identified in the lateral septum, the subfornical organ (SFO), the thalamus, the hypothalamus, the interpenduncular nucleus, the posterodorsal tegmental nucleus, the area postrema (AP), the inferior olive and the nucleus of the solitary tract (NTS). Binding studies with [125I][Tyr39] exendin-4, a GLP-1 receptor agonist, showed an identical distribution pattern of binding sites. Binding specificity and affinity was investigated using sections of the brainstem containing the NTS. Binding of [125I]GLP-1 to the NTS was inhibited concentration-dependently by unlabelled GLP-1 and [Tyr39]exendin-4 with KI values of 3.5 and 9.4 nM respectively. Cross-linking of hypothalamic membranes with [125I]GLP-1 or [125I][Tyr39]exendin-4 identified a single ligand-binding protein complex with a molecular mass of 63,000 Da. The fact that no GLP-1 binding sites were detected in the cortex but that they were detected in the phylogenetically oldest parts of the brain emphasizes that GLP-1 may be involved in the regulation of vital functions. In conclusion, the biochemical data support the idea that the central GLP-1 receptor resembles the peripheral GLP-1 receptor. Furthermore, the presence of GLP-1 binding sites in the circumventricular organs suggests that these may be receptors which act as the target for both peripheral blood-borne GLP-1 and GLP-1 in the nervous system.
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Volz A, Göke R, Lankat-Buttgereit B, Fehmann HC, Bode HP, Göke B. Molecular cloning, functional expression, and signal transduction of the GIP-receptor cloned from a human insulinoma. FEBS Lett 1995; 373:23-9. [PMID: 7589426 DOI: 10.1016/0014-5793(95)01006-z] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Glucose-dependent insulinotropic polypeptide (GIP) plays an important role in the regulation of postprandial insulin secretion and proinsulin gene expression of pancreatic beta-cells. This study demonstrates the molecular cloning of a cDNA for the GIP-receptor from a human insulinoma lambda gt11 cDNA library. The cloned cDNA encoded a seven transmembrane domain protein of 466 amino acids which showed high homology (41%) to the human glucagon-like peptide 1 (GLP-1) receptor. Homology to the GIP receptor from rat or hamster was 79% and 81%, respectively. When transfected stably into fibroblast CHL-cells a high affinity receptor was expressed which coupled to the adenylate cyclase with normal basal cAMP and increasing intracellular cAMP levels under stimulation with human GIP-1-42 (EC50 = 1.29 x 10(-13) M). The receptor accepted only human GIP 1-42 (Kd = 1.93 +/- 0.2 x 10(-8) M) and porcine truncated GIP 1-30 (Kd = 1.13 +/- 0.1 x 10(-8) M) as high affinity ligands. At 1 microM, exendin-4 and (9-39)amide weakly reduced GIP-binding (25%) whereas secretin, glucagon, glucagon-like peptide-1, vasoactive intestinal polypeptide, peptide histidine-isoleucine, and pituitary adenylyl cyclase activating peptide were without effect. In transfected CHL cells, GIP-1-42 did not increase intracellular calcium. Northern analysis revealed one transcript of human GIP receptor mRNA with an apparent size of 5.5 kb. The exact understanding of GIP receptor regulation and signal transduction will aid in the understanding of the incretin hormone's failure to exert its biological action at the pancreatic B-cell in type II diabetes mellitus.
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Hupe-Sodmann K, McGregor GP, Bridenbaugh R, Göke R, Göke B, Thole H, Zimmermann B, Voigt K. Characterisation of the processing by human neutral endopeptidase 24.11 of GLP-1(7-36) amide and comparison of the substrate specificity of the enzyme for other glucagon-like peptides. REGULATORY PEPTIDES 1995; 58:149-56. [PMID: 8577927 DOI: 10.1016/0167-0115(95)00063-h] [Citation(s) in RCA: 169] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The post-secretory processing of the potent insulinotropic peptide hormone, GLP-1(7-36)amide, probably involves one or more of a small group of membrane-bound ectopeptidases. Reported here, is the characterisation of the endoproteolysis of human GLP-1(7-36)amide by the recombinant human form of neutral endopeptidase (NEP) 24.11, which is one of the best characterised and widely-distributed of ectopeptidases and is involved in the processing of other peptide hormones. The products of the limited endoproteolysis were characterised by mass and primary structure following fractionation using high performance liquid chromatography. The rate of this endoproteolysis by NEP 24.11 was estimated and compared to that of GLP-1(7-36)amide-related peptides. GLP-1(7-36)amide appears to be good substrate for NEP 24.11 with most, but not all potential target bonds being cleaved. Also, the structurally-related peptides, secretin and glucagon appear to be good substrates whereas GIP and exendin-4 are very poor substrates. That the GLP-1(7-36)amide super-agonist, exendin-4 is a poor substrate for NEP 24.11 is significant for the possible use of this peptide as a prototype for the development of clinically-useful peptide agonists. Further studies should reveal whether NEP 24.11 is important for the metabolic clearance of GLP-1(7-36)amide and will be highly relevant for the attempts to realise the suggested therapeutic value of GLP-1(7-36)amide.
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Göke R, Larsen PJ, Mikkelsen JD, Sheikh SP. Identification of specific binding sites for glucagon-like peptide-1 on the posterior lobe of the rat pituitary. Neuroendocrinology 1995; 62:130-4. [PMID: 8584112 DOI: 10.1159/000126997] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Glucagon-like peptide-1 (GLP-1) immunoreactivity has been found in autonomic and neuroendocrine brain regions, whereas only limited data are available regarding the characterization and localization of brain GLP-1 receptors. In the present study, using quantitative in vitro autoradiography, a high density of specific binding sites for GLP-1 was characterized on sections of the posterior pituitary lobe of the rat. Low specific binding of radiolabeled GLP-1 was found in the anterior lobe and no specific binding in the intermediate lobe. To examine the specificity of GLP-1 binding sites, sections of the posterior lobe were incubated with radiolabeled GLP-1 in the presence of various peptides. Radiolabeled [Tyr39]exendin-4, a specific GLP-1 agonist, bound to these receptor sites with the same affinity as GLP-1, while glucagon and vasoactive intestinal peptide (VIP) were unable to displace 125I-GLP-1. Both unlabeled exendin-4 and GLP-1 inhibited this binding with equally high affinity. Using 125I-[Tyr39]exendin-4 as radiolabel, the concentration of biding sites was found to be 7.8 +/- 0.4 fmol/mg tissue. Further analysis of the binding data from experiments with tissue slices revealed the presence of high and low affinity binding sites. In experiments with unlabeled [Tyr39]exendin-4, the KdS were 6.2 +/- 1.4 x 10(-12) and 9.3 +/- 1.5 x 10(-10) M, respectively, and in experiments with unlabeled GLP-1, 3.4 +/- 1.8 x 10(-12) and 5.9 +/- 1.5 x 10(-10) M, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
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Fehmann HC, Göke R, Göke B. Cell and molecular biology of the incretin hormones glucagon-like peptide-I and glucose-dependent insulin releasing polypeptide. Endocr Rev 1995; 16:390-410. [PMID: 7671853 DOI: 10.1210/edrv-16-3-390] [Citation(s) in RCA: 339] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Göke B, Göke R, Fehmann HC, Arnold R. [Incretin research in the development of new strategies of diabetes therapy]. Internist (Berl) 1995; 36:343-9. [PMID: 7775082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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Herrmann C, Göke R, Richter G, Fehmann HC, Arnold R, Göke B. Glucagon-like peptide-1 and glucose-dependent insulin-releasing polypeptide plasma levels in response to nutrients. Digestion 1995; 56:117-26. [PMID: 7750665 DOI: 10.1159/000201231] [Citation(s) in RCA: 387] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The nutrient-dependent glucagon-like peptide-1 (7-36) amide (GLP-1) release was studied in comparison to the glucose-dependent insulin-releasing polypeptide (GIP) response in 10 healthy volunteers each undergoing various protocols. Plasma samples were saved up to 120 min after challenges by oral, intravenous or intraduodenal administration of nutrients. Basal plasma-GLP-1 concentrations ranged between 0.4 and 1.4 pM, maximal postprandial GLP-1 levels peaked between 10 and 12 pM. Intravenous glucose (25 g i.v.) did not change basal GLP-1 levels. Oral administration of glucose (50 g) induced a biphasic GLP-1 release peaking at 30-60 min and a biphasic GIP release peaking at 5 and 45 min. This increase paralleled the secretion of insulin. Oral galactose (100 g) and amino acids (25 g) also induced a rapid plasma GLP-1 response. After fat (67 g corn oil) a strong and long-lasting (> 120 min) increase of GLP-1 plasma levels occurred. When a mixed liquid meal was given (6 g soybean oil, 5 g casein, 13 g glucose) immunoreactive (IR)-GLP-1 rapidly increased and peaked after 5 min with declining levels after 30 min. In response to an intraduodenal infusion of a small glucose load (5.34 g within 120 min) a rapid, short-lasting GLP-1 response occurred whereas plasma GIP and insulin levels remained unaltered. Luminal perfusion of an isolated vascularly perfused rat ileum with a polydiet induced a rapid rise of portally released IR-GLP-1 which was followed by a sustained release. Glucose evoked sodium-dependently a sharp increase of IR-GLP-1 levels followed by a plateau release. The intraluminal infusion of a mixture of amino acids or fat was without any effect on IR-GLP-1. We hypothesize that in contrast to GIP the GLP-1 release from L cells is triggered by nervous reflexes, by putative humoral factor(s) being released from the upper small intestine in addition to nutrient stimuli acting at the luminal surface of the gut.
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Kolligs F, Fehmann HC, Göke R, Göke B. Reduction of the incretin effect in rats by the glucagon-like peptide 1 receptor antagonist exendin (9-39) amide. Diabetes 1995; 44:16-9. [PMID: 7813808 DOI: 10.2337/diab.44.1.16] [Citation(s) in RCA: 102] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Glucagon-like peptide 1 (7-37)/(7-36) amide (GLP-1) is derived from the intestinal proglucagon processing. It is considered an important insulin-releasing gut hormone. This study uses exendin (9-39) amide as a GLP-1 receptor antagonist to evaluate the contribution of GLP-1 to the incretin effect. Anesthetized rats were challenged by an intraduodenal glucose infusion to evaluate maximally occurring GLP-1 and gastric inhibitory polypeptide (GIP) plasma levels. Maximal immunoreactive (IR) GLP-1 plasma levels amounted to 10 pmol/l (IR-GIP 11 pmol/l). Exendin (9-39) amide abolished the insulin-stimulatory effect of 60 pmol of GLP-1 or of the GLP-1 agonist exendin-4 (0.5 nmol) injected as bolus, respectively. An intravenous bolus injection of 5.94 nmol of exendin (9-39) amide 3 min before enteral glucose infusion grossly reduced the total insulin secretory response (by 60%) and significantly increased circulating blood glucose levels (P < 0.05). In contrast, the GLP-1 antagonist left the insulin response after an intravenous glucose or glucose plus GIP (60 pmol) load unaltered. Our data support the concept that GLP-1 is an important incretin factor. Exendin (9-39) amide is a useful GLP-1 antagonist for in vivo studies.
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Göke B, Herrmann C, Göke R, Fehmann HC, Berghöfer P, Richter G, Arnold R. Intestinal effects of alpha-glucosidase inhibitors: absorption of nutrients and enterohormonal changes. Eur J Clin Invest 1994; 24 Suppl 3:25-30. [PMID: 8001623 DOI: 10.1111/j.1365-2362.1994.tb02252.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The present paper addresses the question how alpha-glucosidase inhibitors affect glucose homeostasis. To facilitate this already established data on the effects of induced malabsorption on gut hormones such as gastric inhibitory polypeptide (GIP) in connection with preliminary findings which deal with the new incretin hormone glucagon-like peptide 1 (7-36) amide (GLP-1) are discussed. To emphasize the possibly important impact of a regulated GLP-1 release in response to glucosidase inhibitor treatment we evaluate the recently introduced concept of 'glucose competence' of pancreatic beta-cells. The slowing of nutrient (i.e. glucose) absorption by therapeutic means (for example, acarbose) could supplement a new approach in the treatment of type 2 diabetics which would utilize the well-preserved insulinotropic activity of GLP-1 in these patients, its glucagon-lowering effect, and its possible inhibition of gastric emptying rates, the latter helping to reduce the requirement for rapid insulin secretory responses as is intended while using alpha-glucosidase inhibitor treatment.
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van Eyll B, Lankat-Buttgereit B, Bode HP, Göke R, Göke B. Signal transduction of the GLP-1-receptor cloned from a human insulinoma. FEBS Lett 1994; 348:7-13. [PMID: 7517895 DOI: 10.1016/0014-5793(94)00553-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
GLP-1 (glucagon-like peptide 1 (7-36) amide) plays an important role in the regulation of insulin secretion and proinsulin gene expression of pancreatic beta-cells. Patients with insulinoma tumors show uncontrolled insulin hypersecretion. This study demonstrates the molecular cloning of a cDNA for the GLP-1 receptor from a human insulinoma employing a lambda-gt11 cDNA library. The cloned cDNA encoded a seven transmembrane domain protein of 463 amino acids which showed high homology to the GLP-1 receptor in normal human pancreas. Four amino acid exchanges were found in comparison to a receptor sequence obtained from regular pancreatic islets. When transfected transiently into COS-7 or stably into fibroblast CHL cells a high affinity receptor was expressed which coupled to the adenylate cyclase with normal basal cAMP and increasing intracellular cAMP levels under GLP-1 stimulation. The receptor accepted GLP-1 and the non-mammalian agonist exendin-4 as high affinity ligands. In transfected COS-7 cells, GLP-1 did not influence intracellular calcium, whereas in the stably transfected fibroblasts GLP-1 transiently increased intracellular calcium to a small extent. The understanding of GLP-1 receptor regulation and signal transduction will aid in the discovery of compounds that act as agonists of the GLP-1 receptor for potential use in the treatment of diabetes and will facilitate the understanding of its expression under normal and pathophysiological conditions.
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Eissele R, Göke R, Weichardt U, Fehmann HC, Arnold R, Göke B. Glucagon-like peptide 1 immunoreactivity in gastroentero-pancreatic endocrine tumors: a light- and electron-microscopic study. Cell Tissue Res 1994; 276:571-9. [PMID: 8062345 DOI: 10.1007/bf00343955] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The preproglucagon gene encodes, in addition to glucagon, two smaller peptides with structural similarity: glucagon-like peptides 1 and 2. Glucagon-like peptide 1 (GLP-1) 7-36 amide is the most powerful incretin candidate. In the present study, GLP-1 immunoreactivity was investigated in tissue specimens of various types of gastroenteropancreatic tumors, and the serum-levels of GLP-1 were assayed. Immunohistochemical staining of 88 tumors revealed GLP-1 immunoreactivity in 17 neoplasias (19.3%), viz., in 7 out of 33 non-functioning tumors, 4 out of 20 gastrinomas, 4 out of 13 insulinomas, 1 out of 3 vasoactive-intestinal-polypeptide (VIP)omas and 1 adrenocorticotropic-hormone (ACTH)-producing tumor. In these tumors, GLP-1-immunoreactive cells were distributed either diffusely, arranged in clusters, or as single cells. All GLP-1-positive tumors were immunoreactive for glucagon or glicentin, 10 tumors were immunoreactive for pancreatic polypeptide, and 8 tumors for insulin. Ultrastructural analysis of 8 GLP-1-positive tumors, with the immunogold technique, demonstrated GLP-1 immunoreactivity mainly in cells resembling the A-cells of the pancreas or the L-cells of the gut. Of the 17 GLP-1-immunoreactive tumors, 15 were primarily located in the pancreas. Additionally, 2 non-functioning tumors of the rectum were GLP-1 immunoreactive. Five tumors were GLP-1 immunoreactive from 9 patients with multiple endocrine neoplasia I syndrome. Patients with GLP-1-immunoreactive tumors were characterized by a significantly lower rate of distant metastases (P < 0.01) and a higher rate of curative resections (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
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Göke R, Just R, Lankat-Buttgereit B, Göke B. Glycosylation of the GLP-1 receptor is a prerequisite for regular receptor function. Peptides 1994; 15:675-81. [PMID: 7937345 DOI: 10.1016/0196-9781(94)90095-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The GLP-1 receptor on RINm5F cells is a glycoprotein with a M(r) of 63,000. Treatment of the receptor with glycopeptidase F generated a protein with a M(r) of 51,000, indicating that the GLP-1 receptor contains N-linked glycans. Tunicamycin pretreatment concentration-dependently decreased GLP-1 binding to RINm5F cells due to a decreased receptor number without change of receptor affinity. Tunicamycin exerted no effect on the GLP-1 receptor mRNA expression. The stimulation of cAMP production was decreased in tunicamycin-treated cells. Our data show that glycosylation of the GLP-1 receptor is a precondition for regular receptor function.
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Lankat-Buttgereit B, Göke R, Stöckmann F, Jiang J, Fehmann HC, Göke B. Detection of the human glucagon-like peptide 1(7-36) amide receptor on insulinoma-derived cell membranes. Digestion 1994; 55:29-33. [PMID: 8112494 DOI: 10.1159/000201119] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
125I-glucagon-like peptide 1(7-36)amide was covalently cross-linked to a specific binding protein in human insulinoma cell membranes. A single radiolabeled band at M(r) 63,000 was identified by SDS-PAGE after solubilization of the ligand-binding protein complex. The molecular weight of this apparent GLP-1 receptor in human endocrine pancreatic tissue was of identical size as the GLP-1 receptor on rat insulinoma-derived RINm5F cell membranes. The radiolabeled band was undetectable when 1 microM of unlabeled GLP-1(7-36)amide or of the GLP-1 antagonist exendin(9-39)amide was included in the binding assay. Utilizing isolated poly-A+ RNA from the human insulinoma and a 1,500 bp Eco-RI fragment of the cDNA coding for the rat GLP-1(7-36)amide receptor for Northern blot analysis, a main hybridization signal at about 7 kb was found by Northern blotting. Our data provide the first direct evidence of the existence of GLP-1 receptors in human endocrine pancreatic tissue.
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Göke R, Wagner B, Fehmann HC, Göke B. Glucose-dependency of the insulin stimulatory effect of glucagon-like peptide-1 (7-36) amide on the rat pancreas. RESEARCH IN EXPERIMENTAL MEDICINE. ZEITSCHRIFT FUR DIE GESAMTE EXPERIMENTELLE MEDIZIN EINSCHLIESSLICH EXPERIMENTELLER CHIRURGIE 1993; 193:97-103. [PMID: 8516568 DOI: 10.1007/bf02576216] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The glucose-dependent action of GLP-1 (7-36) amide (GLP-1) on insulin secretion was studied in isolated islets and in the perfused rat pancreas. In islet experiments in the presence of non-stimulatory glucose levels (< 3 mmol/l) a GLP-1 concentration of 10 nmol/l increased insulin secretion by 83%. However, higher GLP-1 concentrations (25 and 100 nmol/l) could not further enhance this effect (85 and 83%, respectively). The onset of the stimulatory action of a supramaximal GLP-1-load (25 nmol/l) was at a glucose level of 3 mmol/l. In the perfused pancreas, 25 nmol/l GLP-1 induced a strong insulin release at 5 mmol/l glucose, but under basal glucose (2.8 mmol/l) only a slight enhancement of insulin secretion occurred during the late phase (30 to 54 min) of perfusion (P < 0.05). In conclusion, a slight but not dose-dependent stimulation of insulin secretion by supramaximal GLP-1 loads under basal glucose levels was found. The necessary GLP-1 concentrations to achieve this in vitro effect are beyond physiological or postprandial levels.
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Richter G, Feddersen O, Wagner U, Barth P, Göke R, Göke B. GLP-1 stimulates secretion of macromolecules from airways and relaxes pulmonary artery. THE AMERICAN JOURNAL OF PHYSIOLOGY 1993; 265:L374-81. [PMID: 8238371 DOI: 10.1152/ajplung.1993.265.4.l374] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Recent data revealed the existence of specific receptors for glucagon-like peptide-1(7-36)amide (GLP-1) on rat lung membranes. Utilizing slide-mount autoradiography of fresh frozen lung tissue sections, we have localized binding sites for GLP-1 on mucous glands in the trachea and on vascular smooth muscle of the pulmonary artery. When tracheas were incubated in a modified Ussing chamber, the addition of GLP-1 to the submucosal side increased 35S-sulfate-labeled macromolecule secretion (191 +/- 12% above basal, P < 0.005). The optimal secretory response elicited by GLP-1 was approximately 23% of the maximal secretory response after a maximal acetylcholine stimulation. Other proglucagon-derived peptides such as glucagon, oxyntomodulin, and GLP-2 had no effect. In isolated rings of arteries, GLP-1 (10(-8) to 10(-5) M) induced a dose-dependent and time-reversible relaxation of preconstricted arteries. In a preparation with denuded epithelium, GLP-1 lost its effect. In conclusion, GLP-1 might represent another neuropeptide that acts as neurotransmitter of the peptidergic, nonadrenergic-noncholinergic nervous system that innervates the airways.
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Göke R, Fehmann HC, Linn T, Schmidt H, Krause M, Eng J, Göke B. Exendin-4 is a high potency agonist and truncated exendin-(9-39)-amide an antagonist at the glucagon-like peptide 1-(7-36)-amide receptor of insulin-secreting beta-cells. J Biol Chem 1993; 268:19650-5. [PMID: 8396143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Exendin-4 purified from Heloderma suspectum venom shows structural relationship to the important incretin hormone glucagon-like peptide 1-(7-36)-amide (GLP-1). We demonstrate that exendin-4 and truncated exendin-(9-39)-amide specifically interact with the GLP-1 receptor on insulinoma-derived cells and on lung membranes. Exendin-4 displaced 125I-GLP-1, and unlabeled GLP-1 displaced 125I-exendin-4 from the binding site at rat insulinoma-derived RINm5F cells. Exendin-4 had, like GLP-1, a pronounced effect on intracellular cAMP generation, which was reduced by exendin-(9-39)-amide. When combined, GLP-1 and exendin-4 showed additive action on cAMP. They each competed with the radio-labeled version of the other peptide in cross-linking experiments. The apparent molecular mass of the respective ligand-binding protein complex was 63,000 Da. Exendin-(9-39)-amide abolished the cross-linking of both peptides. Exendin-4, like GLP-1, stimulated dose dependently the glucose-induced insulin secretion in isolated rat islets, and, in mouse insulinoma beta TC-1 cells, both peptides stimulated the proinsulin gene expression at the level of transcription. Exendin-(9-39)-amide reduced these effects. In conclusion, exendin-4 is an agonist and exendin-(9-39)-amide is a specific GLP-1 receptor antagonist.
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Göke R, Fehmann H, Linn T, Schmidt H, Krause M, Eng J, Göke B. Exendin-4 is a high potency agonist and truncated exendin-(9-39)-amide an antagonist at the glucagon-like peptide 1-(7-36)-amide receptor of insulin-secreting beta-cells. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(19)36565-2] [Citation(s) in RCA: 188] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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McGregor GP, Fehmann C, Hartel R, Voigt KH, Göke B, Göke R. Investigations of the expression and post-translational processing of the preprotachykinin-I (PPT-I) gene by rat pancreatic, insulin-producing tumor cell-lines. REGULATORY PEPTIDES 1993; 46:444-6. [PMID: 7692562 DOI: 10.1016/0167-0115(93)90114-n] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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Fehmann HC, Göke R, Göke B. [Isolation and sequencing of cDNA of the GLP-I receptor]. ZEITSCHRIFT FUR GASTROENTEROLOGIE 1993; 31:218-9. [PMID: 8386414] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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70
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Göke R, Kolligs F, Richter G, Lankat-Buttgereit B, Göke B. Solubilization of active receptors for glucagon-like peptide-1(7-36)amide from rat lung membranes. THE AMERICAN JOURNAL OF PHYSIOLOGY 1993; 264:L146-52. [PMID: 8383446 DOI: 10.1152/ajplung.1993.264.2.l146] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
We report on a protocol that allows the solubilization of active glucagon-like peptide (GLP)-1-(7-36)amide receptors from rat lung membranes. Digitonin-solubilized GLP-1(7-36)amide binding proteins from lung membranes most effectively, whereas (3-[(3-cholamidopropyl)- dimethylamino]-1-propane-sulfonate was less affective, and octyl-beta-glucoside, Triton X-100 and Lubrol PX were almost ineffective. Solubilization of binding activity was optimal at a digitonin concentration of 1%, a protein-to-detergent ratio of 1:10, and a pH between 7.0 and 8.0. Binding of GLP-1(7-36)amide to solubilized receptors was dependent on the concentration of solubilized protein. The presence of certain mono- and divalent cations was crucial for binding of GLP-1(7-36)amide to solubilized receptors. Scatchard analysis of the binding data revealed a single class of binding sites with dissociation and maximum binding constant values of 0.40 +/- 0.20 nM and 80.0 +/- 26.0 fmol/mg protein for membrane bound and 7.0 +/- 0.6 microM and 12.0 +/- 6.0 nmol/mg protein for solubilized receptors, respectively. In cross-linking experiments 125I-labeled GLP-1(7-36)amide was covalently attached to GLP-1(7-36)amide receptors on lung membranes. The apparent molecular mass of the solubilized receptor was 55,000 Da. This was proven in another experiment when receptor was consecutively cross-linked after solubilization. Nonhydrolyzable GTP analogues (GTP gamma S or GDP beta S) were unable to reduce GLP-1(7-36)amide-binding at solubilized receptors. This argues that the receptor is solubilized as a single protein and not as a receptor-G protein complex.(ABSTRACT TRUNCATED AT 250 WORDS)
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Göke R, McGregor GP, Göke B. Amylin alters the biological action of the incretin hormone GLP-1(7-36)amide. Life Sci 1993; 53:1367-72. [PMID: 7692203 DOI: 10.1016/0024-3205(93)90597-v] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We investigated the effect of amylin on the glucagon-like peptide-1(7-36)amide (GLP-1(7-36)amide) induced stimulation of cAMP production in RINm5F cells. Amylin and the structurally related calcitonin gene-related peptide (CGRP) inhibited the stimulatory effect of GLP-1(7-36)amide on cAMP generation while substance P was without effect. Amylin had no effect on the forskolin-induced cAMP-generation. These findings suggest that amylin alters the biological action of the incretin hormone GLP-1(7-36)amide. This could at least partly contribute to an amylin-induced impaired glucose tolerance which has been previously observed.
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Schardt C, Rotsch M, Erbil C, Göke R, Richter G, Havemann K. Characterization of insulin-like growth factor II receptors in human small cell lung cancer cell lines. Exp Cell Res 1993; 204:22-9. [PMID: 8380141 DOI: 10.1006/excr.1993.1004] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Small cell lung cancer (SCLC) cell lines were investigated for the expression of insulin-like growth factor (IGF) II receptor by means of radioreceptor assays, cross-linking techniques, and Northern blot analysis. 125I-IGF II binds to both the IGF I and the IGF II receptor on intact SCLC cells. Detailed receptor assays performed on microsomal and plasma membranes gave evidence that 125I-IGF II binds with high affinity (70-80 pM) to the IGF I receptor and with low affinity (2-4 nM) to the IGF II receptor, and not conversely. The presence of mannose-6-phosphate enhanced the binding of 125I-IGF II to the IGF II receptor of SCLC. Mannose-6-phosphate also increased the efficiency of N-hydroxysuccinimide ester in cross-linking 125I-IGF II to the IGF II receptor and facilitated the cross-linking of 125I-IGF II to a second protein of 240-250 kDa. Soluble IGF II receptor was also detected in conditioned media of SCLC cell lines.
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Lankat-Buttgereit B, Göke R, Fehmann HC, Niess C, Göke B. Expression of the ras-related rab3a gene in insulinoma-derived cell lines. FEBS Lett 1992; 312:183-6. [PMID: 1330692 DOI: 10.1016/0014-5793(92)80931-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
This study was designed to search for the expression of the small-molecular-weight GTP-binding protein rab3a in endocrine pancreatic cell lines. Total RNA was isolated from five different cell lines (RINm5F, RIN 104836, beta-TC1, HIT-15, and INRI-G9) and from whole rat brain. The expression of rab3a was analyzed by Northern blots. Similar as in brain two transcripts of 1300 and 1800 bp were detected in RIN-cells at low stringency conditions with the predominant signal at 1300 bp. At high stringency the stronger signal was at 1800 bp. When a 300 bp PstI fragment derived from the coding region of rab3a was utilized as probe the 1800 bp signal was predominant under each condition. Only a faint band at 1800 bp occurred in preparations from beta TC1-cells and no signal at all was found in HIT-15 and INRI-G9-cells. In conclusion, rab3a is expressed in rat insulin-releasing insulinoma-derived RIN-cells with a specific 1800 bp transcription product.
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McGregor GP, Hartel R, Fehmann HC, Lankat-Buttgereit B, Göke B, Göke R, Voigt K. Characterisation of the expression and post-translational processing of the preprotachykinin-I gene and the regulated release of tachykinins by the RINm5F cell-line. FEBS Lett 1992; 312:187-91. [PMID: 1426250 DOI: 10.1016/0014-5793(92)80932-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Normal transcription and postranslational processing of the preprotachykinin (PPT)-I gene and regulated release of substance P and neurokinin A by the rat pancreatic endocrine cell-line, RINm5F, has been demonstrated, using radioimmunoassays (RIAs), reversed-phase (rp)HPLC and Northern blot analysis. This is the first stable cell-line found to express the PPT-I gene and provides an opportunity for investigating PPT-I gene expression and tachykinin biosynthesis. RIN5mF cells are a model for the pancreatic beta-cell, which is not known to exhibit PPT-I gene expression which may, therefore, be a feature of the transformed state of these cells. These data may imply that the tachykinins are important in pancreatic islet embryogenesis.
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Abstract
Glucagon-like peptide-1 (GLP-1) is the main product of the intestinal processing of proglucagon. It is released from the intestinal K-cells into the circulation in response to the oral ingestion of food. At the pancreatic beta cell GLP-1 is a potent insulin secretagogue in the presence of elevated glucose levels, defining glucagon-like peptide-1 as a new incretin. Its action is mediated by specific receptors coupled to the adenylate cyclase system by a stimulatory G-protein. Finally, glucagon-like peptide-1 stimulates proinsulin gene expression and it is thus involved at several levels in the regulation of insulin synthesis and secretion.
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