Does proteostasis get lost in translation? Implications for protein aggregation across the lifespan.

Protein aggregation is a phenomenon of major relevance in neurodegenerative and neuromuscular disorders, cataracts, diabetes and many other diseases. Research has unveiled that proteins also aggregate in multiple tissues during healthy aging yet, the biological and biomedical relevance of this apparently asymptomatic phenomenon remains to be understood. It is known that proteome homeostasis (proteostasis) is maintained by a balanced protein synthesis rate, high protein synthesis accuracy, efficient protein folding and continual tagging of damaged proteins for degradation, suggesting that protein aggregation during healthy aging may be associated with alterations in both protein synthesis and the proteostasis network (PN) pathways. In particular, dysregulation of protein synthesis and alterations in translation fidelity are hypothesized to lead to the production of misfolded proteins which could explain the occurrence of age-related protein aggregation. Nevertheless, some data on this topic is controversial and the biological mechanisms that lead to widespread protein aggregation remain to be elucidated. We review the recent literature about the age-related decline of proteostasis, highlighting the need to build an integrated view of protein synthesis rate, fidelity and quality control pathways in order to better understand the proteome alterations that occur during aging and in age-related diseases.