Figure 1. Protein turnover is an important proteostatic mechanism.

A, cells are exposed to a variety of stresses. Stresses that may be more unrelenting with increasing age include reactive oxygen species (ROS) and advanced glycation endproducts (AGE). B, prolonged exposure to these stresses can result in damage to proteins (and lipids and DNA), represented here as red ovals. C, when protein turnover is maintained at relatively high rates, damaged proteins are quickly degraded and replaced with newly synthesized proteins, preventing accumulation of damaged proteins despite continued exposure to stresses (left). However, when protein turnover rates are slow, it is more likely that protein damage will accumulate (right). Therefore, maintaining rates of protein turnover represents an important mechanism for supporting proteome fidelity.