Endogenous protein turnover during lysosomal storage in normal, Tay-Sachs' and Sandhoff's fibroblasts

At present it is difficult to relate these complex changes directly to intracellular storage. Previous work has shown that macrophages induced to store a number of endocytosable molecules exhibit decreased degradation; for example, 80 mM-sucrose inhibits degradation by 30%. We have similarly found that 80 mM-sucrose inhibits degradation in normal and lipid storage cells at confluence, although the extent of inhibition is more pronounced in normal (20%) than in both Tay-Sachs' (6%) and Sandhoff's (13%). This difference may indicate that lysosomal degradation is already partially inhibited in these storage-disease cells, but we have as yet no clear evidence for this. Indeed, dextran (200 μg/ml) and gangliosides (bovine brain, 200 μg/ml) have no effect on proteolysis on either normal or deseased fibroblasts when presented in the degradation medium, although this may be due to insufficient internalization in 24 hr. Further studies with lysosomotropic agents are required to determine the relevance of storage to these complex differences in degradation in various conditions of growth and during storage.