title: Glucagon-like peptide-2 receptor activation engages bad and glycogen synthase kinase-3 in a protein kinase A-dependent manner and prevents apoptosis following inhibition of phosphatidylinositol 3-kinase.
abstract: Activation of glucagon-like peptide-2 receptor (GLP-2R) signaling promotes expansion of the mucosal epithelium indirectly via activation of growth and anti-apoptotic pathways; however, the cellular mechanisms coupling direct GLP-2R activation to cell survival remain poorly understood. We now demonstrate that GLP-2, in a cycloheximide-insensitive manner, enhanced survival in baby hamster kidney cells stably transfected with the rat GLP-2R; reduced mitochondrial cytochrome c efflux; and attenuated the caspase-dependent cleavage of Akt, poly(ADP-ribose) polymerase, and beta-catenin following inhibition of phosphatidylinositol 3-kinase (PI3K) by LY294002. The prosurvival effects of GLP-2 on LY294002-induced cell death were independent of Akt, p90(Rsk), or p70 S6 kinase activation; were mimicked by forskolin; and were abrogated by inhibition of protein kinase A (PKA) activity. GLP-2 inhibited activation of glycogen synthase kinase-3 (GSK-3) through phosphorylation at Ser(21) in GSK-3alpha and at Ser(9) in GSK-3beta in a PI3K-independent, PKA-dependent manner. GLP-2 reduced LY294002-induced mitochondrial association of endogenous Bad and Bax and stimulated phosphorylation of a transfected Bad fusion protein at Ser(155) in a PI3K-independent, but H89-sensitive manner, a modification known to suppress Bad pro-apoptotic activity. These results suggest that GLP-2R signaling enhances cell survival independently of PI3K/Akt by inhibiting the activity of a subset of pro-apoptotic downstream targets of Akt in a PKA-dependent manner.
authors.affiliation: Department of Medicine, Toronto General Hospital, University Health Network, Banting and Best Diabetes Centre, University of Toronto, Ontario M5G 2C4, Canada.
authors.forename: Bernardo
authors.initials: B
authors.lastname: Yusta
authors.forename: Jennifer
authors.initials: J
authors.lastname: Estall
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Drucker
mesh_terms: D000818:Animals; D017209:Apoptosis; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002460:Cell Line; D002867:Chromones / Q000494:pharmacology; D006224:Cricetinae; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000067757:Glucagon-Like Peptide-1 Receptor; D038362:Glycogen Synthase Kinase 3; D038341:Glycogen Synthase Kinases; D009025:Morpholines / Q000494:pharmacology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D018027:Receptors, Glucagon / Q000378:metabolism*
chemical_list: D002867:Chromones; D004791:Enzyme Inhibitors; C000593835:Glp1r protein, rat; D000067757:Glucagon-Like Peptide-1 Receptor; D009025:Morpholines; D000081082:Phosphoinositide-3 Kinase Inhibitors; D018027:Receptors, Glucagon; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D038341:Glycogen Synthase Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3