title: Human islet cells are killed by BID-independent mechanisms in response to FAS ligand.
abstract: Cell death via FAS/CD95 can occur either by activation of caspases alone (extrinsic) or by activation of mitochondrial death signalling (intrinsic) depending on the cell type. The BH3-only protein BID is activated in the BCL-2-regulated or mitochondrial apoptosis pathway and acts as a switch between the extrinsic and intrinsic cell death pathways. We have previously demonstrated that islets from BID-deficient mice are protected from FAS ligand-mediated apoptosis in vitro. However, it is not yet known if BID plays a similar role in human beta cell death. We therefore aimed to test the role of BID in human islet cell apoptosis immediately after isolation from human cadaver donors, as well as after de-differentiation in vitro. Freshly isolated human islets or 10-12 day cultured human islet cells exhibited BID transcript knockdown after BID siRNA transfection, however they were not protected from FAS ligand-mediated cell death in vitro as determined by DNA fragmentation analysis using flow cytometry. On the other hand, the same cells transfected with siRNA for FAS-associated via death domain (FADD), a molecule in the extrinsic cell death pathway upstream of BID, showed significant reduction in cell death. De-differentiated islets (human islet-derived progenitor cells) also demonstrated similar results with no difference in cell death after BID knockdown as compared to scramble siRNA transfections. Our results indicate that BID-independent pathways are responsible for FAS-dependent human islet cell death. These results are different from those observed in mouse islets and therefore demonstrate potentially alternate pathways of FAS ligand-induced cell death in human and mouse islet cells.
authors.affiliation: Diabetes and Islet Biology Group, NHMRC-Clinical Trials Centre, University of Sydney, Camperdown, Australia.
authors.forename: Mugdha V
authors.initials: MV
authors.lastname: Joglekar
authors.affiliation: St. Vincent's Institute of Medical Research, 41 Victoria Parade, Fitzroy, Melbourne, VIC, 3065, Australia.|Department of Medicine, St. Vincent's Hospital, The University of Melbourne, Melbourne, Australia.
authors.forename: Prerak M
authors.initials: PM
authors.lastname: Trivedi
authors.affiliation: St. Vincent's Institute of Medical Research, 41 Victoria Parade, Fitzroy, Melbourne, VIC, 3065, Australia.|Department of Medicine, St. Vincent's Hospital, The University of Melbourne, Melbourne, Australia.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Kay
authors.affiliation: The Centre for Transplant and Renal Research, Westmead Millennium Research Institute, University of Sydney, Westmead, Australia.
authors.forename: Wayne J
authors.initials: WJ
authors.lastname: Hawthorne
authors.affiliation: The Centre for Transplant and Renal Research, Westmead Millennium Research Institute, University of Sydney, Westmead, Australia.
authors.forename: Philip J
authors.initials: PJ
authors.lastname: O'Connell
authors.affiliation: Diabetes and Islet Biology Group, NHMRC-Clinical Trials Centre, University of Sydney, Camperdown, Australia.|Department of Medicine, St. Vincent's Hospital, The University of Melbourne, Melbourne, Australia.
authors.forename: Alicia J
authors.initials: AJ
authors.lastname: Jenkins
authors.affiliation: Diabetes and Islet Biology Group, NHMRC-Clinical Trials Centre, University of Sydney, Camperdown, Australia.
authors.forename: Anandwardhan A
authors.initials: AA
authors.lastname: Hardikar
authors.affiliation: St. Vincent's Institute of Medical Research, 41 Victoria Parade, Fitzroy, Melbourne, VIC, 3065, Australia. hthomas@svi.edu.au.|Department of Medicine, St. Vincent's Hospital, The University of Melbourne, Melbourne, Australia. hthomas@svi.edu.au.
authors.forename: Helen E
authors.initials: HE
authors.lastname: Thomas
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D051023:BH3 Interacting Domain Death Agonist Protein / Q000235:genetics / Q000378:metabolism*; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D003922:Diabetes Mellitus, Type 1 / Q000473:pathology; D053222:Fas Ligand Protein / Q000378:metabolism*; D053200:Fas-Associated Death Domain Protein / Q000235:genetics*; D006801:Humans; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D019014:fas Receptor / Q000378:metabolism
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; C505533:FADD protein, human; C491901:FAS protein, human; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D053200:Fas-Associated Death Domain Protein; D034741:RNA, Small Interfering; D019014:fas Receptor; D020169:Caspases
keywords: BID; FAS ligand; Human islets; Progenitor cells; Type 1 diabetes; siRNA