Figure 9.

Cathepsin D maturation is perturbed by expression of mutant dynamin. (A) Expression of the lysosomal enzyme cathepsin D (32 kDa) and its precursor procathepsin D (49 kDa) was analyzed by Western blotting of cell lysates (5% of total lysates) and of medium collected from the last 24 h of culture (immunoprecipitates from 50% of medium). When cells were grown without tetracycline (−) in the medium for 48 h, there was a clear increase in cell-associated procathepsin D (left panel). However, even after 72 h without tetracycline and in the presence of butyric acid for the last 24 h, no change was found in the amount of secreted cathepsin into the medium (right panel). Small arrows, procathepsin D; large arrows, mature cathepsin. (B) Graph illustrating the increase in cellular procathepsin D caused by dynK44A expression. The graph is based on scanned blots from three experiments performed after 48 h without tetracycline (○) and six experiments performed after 72 h without tetracycline and in the presence of butyric acid for the last 24 h (●). For a statistical analysis, see text.