title: Rate of Homologous Desensitization and Internalization of the GLP-1 Receptor.
abstract: The glucagon-like peptide-1 receptor (GLP-1R) is an important target in the treatment of type 2 diabetes mellitus. The aim of this study was to compare the rate of agonist stimulated desensitization and internalization of GLP-1R. To this end, an N-terminally myc-tagged GLP-1R was stably expressed in HEK-293 cells. Homologous desensitization was assessed by measuring the cAMP response to agonist stimulation following pre-incubation with agonist for up to 120 min. Receptor internalization was monitored using an indirect ELISA-based method and confocal microscopy. Pre-incubation with GLP-1 resulted in a time-dependent loss of response to a second stimulation. Washing cells following pre-incubation failed to bring cAMP levels back to basal. Taking this into account, two desensitization rates were calculated: "apparent" (t1/2= 19.27 min) and "net" (t1/2= 2.99 min). Incubation of cells with GLP-1 also resulted in a time-dependent loss of receptor cell surface expression (t1/2= 2.05 min). Rapid agonist-stimulated internalization of GLP-1R was confirmed using confocal microscopy. Stimulation of GLP-1R with GLP-1 results in rapid desensitization and internalization of the receptor. Interestingly, the rate of "net" desensitization closely matches the rate of internalization. Our results suggest that agonist-bound GLP-1R continues to generate cAMP after it has been internalized.
authors.affiliation: Department of Pharmacology & Toxicology, Faculty of Medicine, Kuwait University, PO Box 24923, 13110 Safat, Kuwait. ginaboss72@gmail.com.
authors.forename: Ghina
authors.initials: G
authors.lastname: Shaaban
authors.affiliation: Department of Pharmacology & Toxicology, Faculty of Medicine, Kuwait University, PO Box 24923, 13110 Safat, Kuwait. oriowo@hsc.edu.kw.
authors.forename: Mabayoje
authors.initials: M
authors.lastname: Oriowo
authors.affiliation: Department of Pharmacology & Toxicology, Faculty of Medicine, Kuwait University, PO Box 24923, 13110 Safat, Kuwait. Suleiman@hsc.edu.kw.
authors.forename: Suleiman
authors.initials: S
authors.lastname: Al-Sabah
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D000242:Cyclic AMP / Q000096:biosynthesis*; D004305:Dose-Response Relationship, Drug; D015870:Gene Expression; D017930:Genes, Reporter; D052216:Glucagon-Like Peptide 1 / Q000378:metabolism* / Q000494:pharmacology; D000067757:Glucagon-Like Peptide-1 Receptor / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D007700:Kinetics; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism; D013194:Staining and Labeling / Q000379:methods; D013997:Time Factors; D019076:Transgenes; D000097789:Glucagon-Like Peptide-1 Receptor Agonists
chemical_list: D001426:Bacterial Proteins; C000593833:GLP1R protein, human; D000067757:Glucagon-Like Peptide-1 Receptor; D008164:Luminescent Proteins; C489427:MYC protein, human; D016271:Proto-Oncogene Proteins c-myc; C054562:yellow fluorescent protein, Bacteria; D052216:Glucagon-Like Peptide 1; D000242:Cyclic AMP; D008156:Luciferases; D000097789:Glucagon-Like Peptide-1 Receptor Agonists
keywords: GLP-1; desensitization; internalization; receptor