(A) CHOTGFα cells were incubated overnight with BB3103 (10 μM), and then chased for the indicated times in the absence of the compound. Cell lysates were prepared, and proTGFα forms were analysed by Western blotting (left-hand panel) and quantitative densitometry (right-hand panel). The right-hand panel shows the means±S.D. for two different experiments. (B) Action of CHX on the recovery of N-terminal shedding. CHOTGFα cells were incubated overnight with BB3103 (10 μM), and then chased for the indicated times in the absence of the drug. Where indicated, CHX (10 μg/ml) was added to the dishes 30 min before the start of the chase in BB3103-free medium, and CHX was kept throughout the experiment. Cell lysates were prepared, and proTGFα forms were analysed by Western blotting (upper panel) and quantitative densitometry (lower panels) as described in (A). The lower panels show the means±S.D. for two different experiments. Molecular masses are indicated in kDa for the blots.