Measuring Dynamics of Bax Translocation in Living Cells during UV-induced Apoptosis

UV irradiation is a DNA-damage agent that triggers apoptosis through both the membrane death receptor and the mitochondrial apoptotic signaling pathways. Bax, a member of the Bcl-2 family of proteins, translocates from the cytosol to the mitochondrial membrane in response to most apoptotic stimuli, but the dynamics of Bax translocation by UV irradiation is not fully understood. In this study, co-transfecting GFP-Bax and DsRed-Mit into human lung adenocarcinoma cells (ASTC-a-1), we examined the dynamics of Bax translocation by UV irradiation in real time in a single cell. The results showed that Bax translocation was initiated at 5-6 h after UV irradiation and the translocation lasted about 20-30 min. Furthermore, when cells were pretreated with caspase-8 specific inhibitor (Z-IETD-fmk), the dynamics of Bax translocation was not affected. In summary, using real-time single-cell analysis, we observed the dynamics of Bax translocation during UV-induced apoptosis and it was a caspase-8 independent event. Real-time single-cell analysis was an effective method to study the dynamics of protein translocation in living cells during UV-induced apoptosis.