Regulation of lysosomal autophagy in transformed and non-transformed mouse fibroblasts under several growth conditions.
The role of the lysosomal system in accelerated protein degradation was investigated in 3T3 mouse fibroblasts and in the SV40 virus-transformed derivative, SV3T3. Rates of protein degradation and quantitative electron microscopic alterations in the lysosomal system were compared under four different growing conditions: exponential growth, confluent phase, serum deprivation, and confluent phase together with serum deprivation. We found a significant correlation between increases in rates of proteolysis of long-lived proteins and fractional volume of lysosomes, suggesting a causal relationship between the two, as well as a morphological explanation for the differences in rates of protein degradation in transformed and non-transformed cultured cells. The increase in lysosomal fractional volume resulted from an increase in dense bodies only (in serum-deprived exponential or confluent cultures) or from an increase in autophagic vacuoles and dense bodies (in serum-supplemented confluent cultures).
D000818:Animals; D002455:Cell Division; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D003470:Culture Media; D007700:Kinetics; D008247:Lysosomes / Q000502:physiology* / Q000648:ultrastructure; D051379:Mice; D008807:Mice, Inbred BALB C; D008854:Microscopy, Electron; D011506:Proteins / Q000378:metabolism*; D013539:Simian virus 40 / Q000235:genetics*; D014617:Vacuoles / Q000648:ultrastructure
D003470:Culture Media; D011506:Proteins