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.
This work was supported by IZKF Universität Münster Grant BMBF 01 KS 9604/0 (to J. H. M. P.) and Swiss National Science Foundation Grant 32-49755.96 (to C. B. W.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
CommentsThis article is also available at http://www.jbc.org/content/277/8/6413.full.pdf
Published CitationWobser H, Düssmann H, Kögel D, Wang H, Reimertz C, Wollheim CB, Byrne MM, Prehn JH. 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. Journal of Biological Chemistry. 2002;277(8):6413-21.
- Physiology and Medical Physics