THE OVEREXPRESSION OF BAX PRODUCES CELL-DEATH UPON INDUCTION OF THE MITOCHONDRIAL PERMEABILITY TRANSITION

Stably transfected Jurkat T cells were produced in which Bax expressio n is inducible by muristerone A. The cell death resulting from inducti on of the overexpression of Bar was prevented by inhibition of the mit ochondrial permeability transition (MPT) with cyclosporin A (CyA) in c ombination with the phospholipase A(2) inhibitor aristolochic acid (Ar A), The caspase-3 inhibitor Z-Asp-Glu-Val aspartic acid fluoromethylke tone (Z-DEVD-FMK) had no effect on the loss of viability, The MPT was measured as the CyA plus ArA-preventable loss of the mitochondrial mem brane potential (Delta Psi(m)). The MPT was accompanied by the release of cytochrome c from the mitochondria, caspase-3 activation in the cy tosol, cleavage of the nuclear enzyme poly(ADP-ribose)polymerase (PARP ), and DNA fragmentation, all of which were inhibited by CyA plus ArA, Z-DEVD-FMK had no effect on the loss of Delta Psi(m) and the redistri bution of cytochrome c but did prevent caspase-3 activation, PARP clea vage, and DNA fragmentation. It is concluded that Bar induces the MPT, a critical event in the loss of cell viability. In addition to the ce ll death, the MPT mediates other typical manifestations of apoptosis i n this model, namely release of cytochrome c, caspase activation with PARP cleavage, and DNA fragmentation.