[Cell sensitivity to Fas-mediated apoptosis depends on three forms of Fas-antigen]

It is known that binding of specific anti-Fas antibodies to Fas-receptor induces apoptosis in various cell lines. But the mechanisms of functional regulation and realization of apoptosis remain so far unknown. We obtained HeLa cells transfected with cDNA of Fas-antigen, whose expression was located under the promoter controlled by isopropoyl beta-D-thiogalactopiranoside. Analysis of transfectants has shown that expression of Fas above a certain critical level leads to redistribution of Fas in the cells and is accompanied by changes in the cell cycles and cell sensitivity to the cytotoxic effects of anti-Fas and tumor necrosis factor (TNF). We propose that the sensitivity of cells to Fas-mediated apoptosis depends on the ratio of transmembrane, intracellular and soluble Fas-antigen in the cells.