Mutations to the Third Cytoplasmic Domain of the Glucagon-Like Peptide 1 (GLP-1) Receptor Can Functionally Uncouple GLP-1-Stimulated Insulin Secretion in HIT-T15 Cells

Autor: Herbert Y. Gaisano, Michael B. Wheeler, Patrick E. MacDonald, Anne Marie F. Salapatek
Rok vydání: 1999
Předmět:
endocrine system
medicine.medical_specialty
medicine.medical_treatment
Biology
Transfection
Glucagon
Glucagon-Like Peptide-1 Receptor
Cell Line
Adenylyl cyclase
Islets of Langerhans
Structure-Activity Relationship
chemistry.chemical_compound
Endocrinology
Glucagon-Like Peptide 1
Internal medicine
Insulin receptor substrate
Insulin Secretion
Cyclic AMP
Receptors
Glucagon
medicine
Animals
Humans
Insulin
Secretion
Protein Precursors
Receptor
Molecular Biology
Glucagon-like peptide 1 receptor
digestive
oral
and skin physiology
Electric Conductivity
General Medicine
3-Pyridinecarboxylic acid
1
4-dihydro-2
6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-
Methyl ester
Peptide Fragments
Rats
Calcium Channel Agonists
Insulin receptor
Glucose
chemistry
Barium
Mutagenesis
biology.protein
Gene Deletion
hormones
hormone substitutes
and hormone antagonists
Zdroj: Molecular Endocrinology. 13:1305-1317
ISSN: 1944-9917
0888-8809
Popis: Glucagon-like peptide-1 (GLP-1) is an insulinotropic hormone with powerful antidiabetogenic effects that are thought to be mediated by adenylyl cyclase (AC). Recently, we generated two GLP-1 receptor mutant isoforms (IC3-1 and DM-1) that displayed efficient ligand binding and the ability to promote Ca2+ mobilization from intracellular stores but lacked the ability to couple to AC. In the present study, the wild-type rat GLP-1 receptor (WT-GLP-1 R) or the IC3-1 and DM-1 mutant forms were expressed for the first time in the insulin-producing HIT-T15 cells. Only cells expressing WT-GLP-1 R displayed dramatically elevated GLP-1-induced cAMP responses and elevated insulin secretion. The increase in GLP-1-stimulated secretion in cells expressing WT-GLP-1 R, however, was not accompanied by differences in glucose-stimulated insulin release. Prolonged exposure to GLP-1 (10 nM, 17 h), not only led to an increase in insulin secretion but also increased insulin mRNA levels, but only in cells expressing the WT-GLP-1 R and not the mutant isoforms. Electrophysiological analyses revealed that GLP-1 application enhanced L-type voltage-dependent Ca2+ channel (VDCC) currents > 2-fold and caused a positive shift in VDCC voltage-dependent inactivation in WT-GLP-1R cells only, not control or mutant (DM-1) cells. This action on the Ca2+ current was further enhanced by the VDCC agonist, BAYK8644, suggesting GLP-1 acts via a distinct mechanism dependent on cAMP. These studies demonstrate that the GLP-1 receptor efficiently couples to AC to stimulate insulin secretion and that receptors lacking critical residues in the proximal region of the third intracellular loop can effectively uncouple the receptor from cAMP production, VDCC activity, insulin secretion, and insulin biosynthesis.
Databáze: OpenAIRE
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