title: Rapamycin protects against dominant negative-HNF1A-induced apoptosis in INS-1 cells.
abstract: HNF1A-maturity onset diabetes of the young (HNF1A-MODY) is caused by mutations in Hnf1a gene encoding the transcription factor hepatocyte nuclear factor 1alpha (HNF1A). An increased rate of apoptosis has been associated with the decrease in beta-cell mass that is a hallmark of HNF1A-MODY and other forms of diabetes. In a cellular model of HNF1A-MODY, we have recently shown that signalling through mammalian target of rapamycin (mTOR) is decreased by the overexpression of a dominant-negative mutant of HNF1A (DN-HNF1A). mTOR is a protein kinase which has important roles in cell metabolism and growth, but also in cell survival, where it has been shown to be both protective and detrimental. Here, we show that pharmacological inhibition of mTOR activity with rapamycin protected INS-1 cells against DN-HNF1A-induced apoptosis. Rapamycin also prevented DN-HNF1A-induced activation of AMP-activated protein kinase (AMPK), an intracellular energy sensor which we have previously shown to mediate DN-HNF1A-induced apoptosis. Conversely, activation of mTOR with leucine potentiated DN-HNF1A-induced apoptosis. Gene silencing of raptor (regulatory associated protein of mTOR), a subunit of mTOR complex 1 (mTORC1), also conferred protection on INS-1 cells against DN-HNF1A-induced apoptosis, confirming that mTORC1 mediates the protective effect. The potential relevance of this effect with regards to the clinical use of rapamycin as an immunosuppressant in diabetics post-transplantation is discussed.
authors.affiliation: Department of Endocrinology, Mater Misericordiae University Hospital, Eccles Street, Dublin 7, Ireland.
authors.forename: Angela M
authors.initials: AM
authors.lastname: Farrelly
authors.forename: Seán M
authors.initials: SM
authors.lastname: Kilbride
authors.forename: Caroline
authors.initials: C
authors.lastname: Bonner
authors.forename: Jochen H M
authors.initials: JH
authors.lastname: Prehn
authors.forename: Maria M
authors.initials: MM
authors.lastname: Byrne
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003922:Diabetes Mellitus, Type 1 / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D005786:Gene Expression Regulation / Q000187:drug effects; D005799:Genes, Dominant; D051538:Hepatocyte Nuclear Factor 1-alpha / Q000235:genetics / Q000378:metabolism*; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000187:drug effects*; D007340:Insulinoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D007930:Leucine / Q000494:pharmacology; D009154:Mutation; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D051381:Rats; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction; D020123:Sirolimus / Q000494:pharmacology / Q000627:therapeutic use; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism
chemical_list: D051538:Hepatocyte Nuclear Factor 1-alpha; C496489:Hnf1a protein, rat; C546845:mTOR protein, rat; D058570:TOR Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases; D007930:Leucine; D020123:Sirolimus