Essential role of caspase-3 in apoptosis of mouse beta-cells transfected with human Fas

Several recent studies hare indicated that the Fas-Fas ligand system may be critical for pancreatic beta-cell destruction in type 1 diabetes. Although the fundamental roles of caspases in the mammalian apoptotic machinery hav e been elucidated, it is not known which caspase or caspases play a major r ole in Fas-mediated apoptosis of beta-cells. In this study we transfected h uman Fas cDNA into a mouse beta-cell line (beta TC1) and established a beta -cell clone expressing human Fas. This clone, designated hFas/beta TC1, und erwent apoptosis when exposed to anti-Fas, showing hallmarks of apoptosis ( chromatin condensation nucleolar disintegration, internucleosomal DNA fragm entation, and annexin V staining), indicating that the mouse beta-cell line has the intact machinery of Fas-mediated apoptosis. The cross-linking of F as by anti-Fas resulted in the elevation of caspase-3-like, but, not caspas e-1-like, protease activity 2-12 h after the addition of the anti-Fas. A ca spase-3 inhibitor, Z-Asp-Glu-Val-Asp-fluoromethyl ketone, attenuated the Fa s-mediated beta-cell apoptosis, while a caspase-1 inhibitor, acetyl-Tyr-Val -Ala-Asp-chloromethylketone failed to suppress the apoptosis. Thus the Fas- induced death signal apparently bypassed caspase-1 in the cells. Furthermor e, an antisense caspase-3 construct blocked caspase-3 activation and substa ntially suppressed Fas-triggered apoptosis of hFas/beta TC1 cells. These ob servations suggest the essential role of caspase-3 in Fas-mediated apoptosi s of the beta-cell line.