Glucagon-like peptide-1 receptor expression in Xenopus oocytes stimulates inositol trisphosphate-dependent intracellular Ca2+ mobilization.

The signal transduction pathway of the cloned human glucagon-like peptide-1 (GLP-1) receptor was studied in voltage-clamped Xenopus oocytes. Binding of GLP-1(7-36)amide was associated with cAMP production, increased [Ca2+]i and activation of Ca2+-dependent Cl- current. The effect of GLP-1(7-36)amide reflects intracellular Ca2+ mobilization and was suppressed by injection of the Ca2+ chelator BAPTA and the inositol trisphosphate receptor antagonist heparin. The responses were not mimicked by the adenylate cyclase activator forskolin and unaffected by the protein kinase A (PKA) inhibitor Rp-cAMPS. We conclude that GLP-1 receptor expression in Xenopus oocytes evokes inositol trisphosphate-dependent intracellular Ca2+ mobilization independent of the cAMP/PKA signaling pathway.