Yin Z, Wheatley D N
Cell Pathology Laboratory, University Medical School, Aberdeen, Scotland, Great Britain.
Cytobios. 1994;79(319):201-21.
Protein turnover in serum-deprived Swiss 3T3(U) untransformed and 3T3(T) transformed cells was comprehensively studied. When 3T3(U) cells were cultured in 0.2% serum medium, protein synthesis fell to 28% of the control value by 48 h, but took at least 12 h to become manifest. Meanwhile the rates of degradation of medium- and long-lived proteins were increasing, with a 1.65-fold increase in degradation of the former within 2 h, and the turnover of long-lived proteins doubling in 24 h. A significant increase in the degradation of truly short-lived proteins was not apparent until 24 h of deprivation. After serum restoration in cultures deprived of serum for 24 h, protein synthesis increased from 25 to 40% of the control values within 1 h, reaching 93% by 24 h. The rate of medium-lived protein degradation in 3T3(U) cells quickly returned to control levels, and that of long-lived proteins fell to less than control levels by 3 h, decreasing to 67% by 24 h. This contrasted with short-lived protein turnover, which remained at the same level as the cells kept in 0.2% serum for a further 24 h. The turnover of medium- and long-lived proteins is initially more important than short-lived proteins in growth regulation following the removal of growth factors.
对血清饥饿状态下的未转化瑞士3T3（U）细胞和转化的3T3（T）细胞中的蛋白质周转进行了全面研究。当3T3（U）细胞在0.2%血清培养基中培养时，到48小时蛋白质合成降至对照值的28%，但至少需要12小时才会显现出来。与此同时，中等寿命和长寿命蛋白质的降解速率在增加，前者在2小时内降解增加了1.65倍，长寿命蛋白质的周转在24小时内翻倍。直到饥饿24小时后，真正短寿命蛋白质的降解才明显增加。在剥夺血清24小时的培养物中恢复血清后，蛋白质合成在1小时内从对照值的25%增加到40%，到24小时达到93%。3T3（U）细胞中中等寿命蛋白质的降解速率迅速恢复到对照水平，长寿命蛋白质的降解速率在3小时内降至对照水平以下，到24小时降至67%。这与短寿命蛋白质周转形成对比，短寿命蛋白质周转在细胞继续在0.2%血清中培养24小时的情况下保持在相同水平。在去除生长因子后的生长调节中，中等寿命和长寿命蛋白质的周转最初比短寿命蛋白质更重要。
