Protein aggregation: A detrimental symptom or an adaptation mechanism?

Protein quality control mechanisms oversee numerous aspects of protein lifetime. From the point of protein synthesis, protein homeostasis machineries take part in folding, solubilization, and/or degradation of impaired proteins. Some proteins follow an alternative path upon loss of their solubility, thus are secluded from the cytosol and form protein aggregates. Protein aggregates differ in their function and composition, rendering protein aggregation a complex phenomenon that continues to receive plenty of attention in the scientific and medical communities. Traditionally, protein aggregates have been associated with aging and a large spectrum of protein folding diseases, such as neurodegenerative diseases, type 2 diabetes, or cataract. However, a body of evidence suggests that they may act as an adaptive mechanism to overcome transient stressful conditions, serving as a sink for the removal of misfolded proteins from the cytosol or storage compartments for machineries required upon stress release. In this review, we present examples and evidence elaborating different possible roles of protein aggregation and discuss their potential roles in stress survival, aging, and disease, as well as possible anti-aggregation interventions.