title: The scaffold protein IB1/JIP-1 is a critical mediator of cytokine-induced apoptosis in pancreatic beta cells.
abstract: In insulin-secreting cells, cytokines activate the c-Jun N-terminal kinase (JNK), which contributes to a cell signaling towards apoptosis. The JNK activation requires the presence of the murine scaffold protein JNK-interacting protein 1 (JIP-1) or human Islet-brain 1(IB1), which organizes MLK3, MKK7 and JNK for proper signaling specificity. Here, we used adenovirus-mediated gene transfer to modulate IB1/JIP-1 cellular content in order to investigate the contribution of IB1/JIP-1 to beta-cell survival. Exposure of the insulin-producing cell line INS-1 or isolated rat pancreatic islets to cytokines (interferon-gamma, tumor necrosis factor-alpha and interleukin-1beta) induced a marked reduction of IB1/JIP-1 content and a concomitant increase in JNK activity and apoptosis rate. This JNK-induced pro-apoptotic program was prevented in INS-1 cells by overproducing IB1/JIP-1 and this effect was associated with inhibition of caspase-3 cleavage. Conversely, reducing IB1/JIP-1 content in INS-1 cells and isolated pancreatic islets induced a robust increase in basal and cytokine-stimulated apoptosis. In heterozygous mice carrying a selective disruption of the IB1/JIP-1 gene, the reduction in IB1/JIP-1 content in happloinsufficient isolated pancreatic islets was associated with an increased JNK activity and basal apoptosis. These data demonstrate that modulation of the IB1-JIP-1 content in beta cells is a crucial regulator of JNK signaling pathway and of cytokine-induced apoptosis.
authors.affiliation: Department of Internal Medicine, CHUV-1011 Lausanne, Switzerland. jhaeflig@chuv.hospvd.ch
authors.forename: Jacques-Antoine
authors.initials: JA
authors.lastname: Haefliger
authors.forename: Thomas
authors.initials: T
authors.lastname: Tawadros
authors.forename: Laure
authors.initials: L
authors.lastname: Meylan
authors.forename: Sabine Le
authors.initials: SL
authors.lastname: Gurun
authors.forename: Marc-Estienne
authors.initials: ME
authors.lastname: Roehrich
authors.forename: David
authors.initials: D
authors.lastname: Martin
authors.forename: Bernard
authors.initials: B
authors.lastname: Thorens
authors.forename: Gérard
authors.initials: G
authors.lastname: Waeber
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology*; D053938:DNA Fragmentation / Q000187:drug effects; D005838:Genotype; D007371:Interferon-gamma / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology; D007515:Islets of Langerhans / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases; D008297:Male; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D016207:Cytokines; D007375:Interleukin-1; C490666:MAPK8IP1 protein, human; C490665:Mapk8ip protein, mouse; C110528:Mapk8ip1 protein, rat; D009687:Nuclear Proteins; D015534:Trans-Activators; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases