Aims/hypothesis: Pro-inflammatory cytokines induce death of pancreatic beta cells, leading to the development of type 1 diabetes. We sought to identify novel players and the underlying mechanisms involved in this process. Methods: A high-throughput screen of 3,850 mouse small interfering RNAs (siRNAs) was performed in cytokine-treated MIN6 beta cells. Cells were transfected with the different siRNAs and then treated with a combination of TNFα, IL-1β and IFNγ. Cellular apoptosis (caspase-3/7 activity), and changes in cellular reducing power and cell morphology were monitored. The resulting data were analysed and the corresponding z scores calculated. Results: Several gene families were identified as promoting cytokine-induced beta cell apoptosis, the most prominent being those encoding ubiquitin ligases and serine/threonine kinases. Conversely, deubiquitinating enzymes appeared to reduce apoptosis, while protein phosphatases were mainly associated with lowering cellular reducing power. The screen suggested with high confidence the involvement of several novel genes in cytokine-induced beta cell death, including Camkk2, Epn3, Foxp3 and Tm7sf3, which encodes an orphan seven transmembrane receptor. siRNAs to Tm7sf3 promoted cytokine-induced death of MIN6 cells and human pancreatic islets, and abrogated insulin secretion in these cells. These findings implicate transmembrane 7 superfamily member 3 as a potential new player in the inhibition of cytokine-induced death and in the promotion of insulin secretion from pancreatic beta cells. Conclusions/interpretation: The signalling pathways and novel genes that we identified in this screen and that mediate beta cell death offer new possible targets for therapeutic intervention in diabetes and its adverse complications.
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Acknowledgements We thank G. Yona for his helpful advice and technical assistance. We also thank J.I. Miazaki (Osaka University, Osaka, Japan) for providing MIN6 cells and S. Sampson (Bar Ilan University, Israel) for his critical review of the manuscript. This work was supported by research grants from The Juvenile Diabetes Research Foundation International, The Israel Science Foundation (grant number 759/09), D-CURE Israel, The Mitchel Kaplan Fund and the Minerva Foundation. Y. Zick is the incumbent of the Marte R. Gomez Professorial Chair and B. Geiger is the incumbent of the E. Neter Professorial chair of Cell and Tumor Biology. Human islets were provided through the Juvenile Diabetes Research Foundation award 31-2008-413 (ECIT Islet for Basic Research programme).
- Pancreatic beta cells
- Pro-inflammatory cytokines
- siRNA screens