Figure 8

The proteasome inhibitor lactacystin increases susceptibility of the mutant insulin expressing clone to apoptosis. A. Clone #4S2 cells were untreated or treated with 2 μg/ml doxycycline for 48 h. Cells were then untreated or treated with 10 μM of lactacystin (LC) or an equivalent volume of DMSO for the times indicated. Apoptosis was measured using a cell death detection ELISA kit as described in the Methods. Shown are the mean ± SE of 3 independent experiments. *p < 0.05. B. Following 42 h of doxycycline treatment, cells were untreated, or treated with 10 μM of lactacystin (LC) or an equivalent volume of DMSO for 6 h in the presence of doxycycline. The cells were washed in PBS and lysed. Cell lysates (left panel) or TX-100 insoluble material (right panel) were resolved by SDS-PAGE and immunoblotted using the indicated antibodies. Note the increase in the levels of degradation products detected by the GFP antibody with LC treatment (arrowheads).