Fas-induced apoptosis of glioma cells is associated with down-regulation of the hSCO1 protein, a subunit of complex IV.
ApoI/Fas belongs to the tumor necrosis factor receptor (TNFR) superfamily and mediates cell death in various cell types. Earlier studies from this laboratory have shown that Fas-mediated cell death of glioma cells occur, in part, through the production of reactive oxygen species (ROS). To further dissect the molecular mechanisms that are involved in Fas-induced cell death, we compared gene expression between Fas-treated and saline-treated human neuroglioma H4 cells by using the technique of mRNA differential display. This approach led to the identification of hSCO1, a component of the inner mitochondrial membrane, which is required for the correct assembly, and catalytic function of cytochrome-c oxidase, as a Fas down-regulated gene. The decrease in hSCO1 mRNA expression was time-dependent, becoming most prominent after 4 h of Fas-treatment. Morphological changes observed by confocal microscopy revealed that after 4 h of Fas-treatment, the cells undergo membrane blebbing and early formation of apoptotic bodies. These observations are discussed in terms of their support for an important role of mitochondrial events in Fas-induced apoptosis.