8 nmol/mg of protein in unstimulated cells to 97.5 ± 9.2 nmol/mg of protein in the STA-treated cells. STA increased caspase-3 activity in MITO-GFP cells to 126.2 ± 22.2 nmol/mg of protein, whereas the level of caspase-3 activity was 54.4 ± 6.4 nmol/mg of protein in SKHep1 cells expressing PV-MITO-GFP (P < 0.001, n = 3; Fig. 3C). Next, we investigated whether the caspase-independent intrinsic pathway was also Cyclopamine purchase affected by Ca buffering. Confocal immunofluorescence imaging of AIF demonstrated

that targeting PV to mitochondria reduced the expression of this proapoptotic factor in comparison with SKHep1 cells transfected with the control construct MITO-GFP (Fig. 3D). These data show that the expression of PV in mitochondria protected cells from STA-induced cell death through the caspase-dependent and caspase-independent intrinsic apoptotic pathway. We also investigated whether PV-MITO affected the extrinsic apoptotic pathway. The activity of caspase-8 and caspase-3 was measured in control cells and in cells transfected with PV-MITO-GFP or MITO-GFP and treated with 100 ng/mL TNF-α for 6 hours. TNF-α increased

caspase-8 and caspase-3 activity levels to 246.7 ± 15.2 and 63.3 ± 10.4 nmol/mg of protein, respectively; the levels of activity were 72.0 ± 2.6 and 25 ± 5 nmol/mg of protein, respectively, under control conditions. PV-MITO-GFP expression reduced the level of TNF-α–dependent caspase-8 activity to 150 ± 20 nmol/mg of protein (296.7 ± 30.5 nmol/mg of protein in MITO-GFP cells), and it completely abolished caspase-3 activity (P < 0.001, n = 3; Fig. 3E,F). These data demonstrate that Ca buffering also prevents apoptotic cell medchemexpress learn more death through the extrinsic pathway. Apoptosis can be modulated through the expression of antiapoptotic and proapoptotic genes,24 so we investigated whether alterations of Ca handling could affect the expression of such genes. Real-time PCR showed that Ca buffering reduced the expression of several proapoptotic genes under baseline or STA treatment conditions (Fig. 4A-D). The expression of each gene was normalized to its expression level in unstimulated, nontransfected

cells. The expression of p53 was reduced to 0.72 ± 0.03 au in PV-MITO-GFP cells in comparison with the control (P < 0.001, n = 3). After the STA treatment, the expression of p53 increased to 2.2 ± 0.1 au in untransfected cells, whereas in PV-MITO-GFP cells, it remained at 1.08 ± 0.06 au (P < 0.001, n = 3; Fig. 4A). The expression of bax was reduced to 0.41 ± 0.04 au in PV-MITO-GFP cells in comparison with the control (P < 0.001), and after the STA treatment, the level of bax expression was 2.0 ± 0.2 au in nontransfected cells and 0.72 ± 0.06 au in PV-MITO-GFP cells (P < 0.001, n = 3; Fig. 4B). Although apoptotic peptidase activating factor 1 (apaf-1) expression was not altered between unstimulated control and transfected cells, after the STA treatment, apaf-1 expression increased to 1.69 ± 0.07 au in control cells and remained at 0.83 ± 0.