Dominant-negative suppression of HNF-1 alpha results in mitochondrial dysfunction, INS-1 cell apoptosis, and increased sensitivity to ceramide-, but not to high glucose-induced cell death.
Maturity onset diabetes of the young (MODY) 3 is a monogenic form of diabetes caused by mutations in the transcription factor hepatocyte nuclear factor (HNF)-1 alpha. We investigated the involvement of apoptotic events in INS-1 insulinoma cells overexpressing wild-type HNF-1 alpha (WT-HNF-1 alpha) or a dominant-negative mutant (DN-HNF-1 alpha) under control of a doxycycline-dependent transcriptional activator. Forty-eight h after induction of DN-HNF-1 alpha, INS-1 cells activated caspase-3 and underwent apoptotic cell death, while cells overexpressing WT-HNF-1 alpha remained viable. Mitochondrial cytochrome c release and activation of caspase-9 accompanied DN-HNF-1 alpha-induced apoptosis, suggesting the involvement of the mitochondrial apoptosis pathway. Activation of caspases was preceded by mitochondrial hyperpolarization and decreased expression of the anti-apoptotic protein Bcl-xL. Transient overexpression of Bcl-xL was sufficient to rescue INS-1 cells from DN-HNF-1 alpha-induced apoptosis. Both WT- and DN-HNF-1 alpha-expressing cells demonstrated similar increases in apoptosis when cultured at high glucose (25 mm). In contrast, induction of DN-HNF-1 alpha highly sensitized cells to ceramide toxicity. In cells cultured at low glucose, DN-HNF-1 alpha induction also caused up-regulation of the cell cycle inhibitor p27(KIP1). Therefore, our data indicate that increased sensitivity to the mitochondrial apoptosis pathway and decreased cell proliferation may account for the progressive loss of beta-cell function seen in MODY 3 subjects.
Wobser
Hella
H
Interdisciplinary Center for Clinical Research (IZKF), Research Group Apoptosis and Cell Death, Westphalian Wilhelms-University, D-48149 Münster, Germany.
Düssmann
Heiko
H
Kögel
Donat
D
Wang
Haiyan
H
Reimertz
Claus
C
Wollheim
Claes B
CB
Byrne
Maria M
MM
Prehn
Jochen H M
JH
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics / Q000503:physiopathology; D004318:Doxycycline / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology; D051537:Hepatocyte Nuclear Factor 1; D051538:Hepatocyte Nuclear Factor 1-alpha; D051539:Hepatocyte Nuclear Factor 1-beta; D006801:Humans; D007340:Insulinoma; D008928:Mitochondria / Q000502:physiology*; D009154:Mutation; D009687:Nuclear Proteins; D010190:Pancreatic Neoplasms; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011994:Recombinant Proteins / Q000096:biosynthesis; D013489:Suppression, Genetic; D014157:Transcription Factors / Q000235:genetics*; D015533:Transcriptional Activation / Q000187:drug effects; D014162:Transfection; D014407:Tumor Cells, Cultured; D051020:bcl-X Protein
C494811:BCL2L1 protein, human; C494813:Bcl2l1 protein, rat; D004268:DNA-Binding Proteins; C496487:HNF1A protein, human; C496495:HNF1B protein, human; D051538:Hepatocyte Nuclear Factor 1-alpha; C496489:Hnf1a protein, rat; D009687:Nuclear Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011994:Recombinant Proteins; D014157:Transcription Factors; D051020:bcl-X Protein; D051537:Hepatocyte Nuclear Factor 1; D051539:Hepatocyte Nuclear Factor 1-beta; D005947:Glucose; D004318:Doxycycline