Quantitative proteomic profiling of agerelated protein aggregation in the healthy mouse liver

Abstract

The aging process is a major risk factor for the development of several diseases especially neurodegenerative and metabolic disorders. As cells age, their ability to maintain protein homeostasis (proteostasis) progressively declines, leading to the accumulation of misfolded insoluble proteins, a phenomenon known as protein aggregation. The formation of insoluble protein aggregates has been established as a biological hallmark of several age-related diseases such as Alzheimer´s Disease and Type II Diabetes. It has been reported that proteins aggregate during healthy tissue aging yet, the altered biological mechanisms remain to be elucidated. The question is whether protein aggregation arises as a consequence of alterations in protein synthesis and degradation pathways during aging. We hypothesize that protein aggregation occurs during natural tissue aging due to an age-associated decline of proteostasis responses responsible for misfolded protein degradation. In this study, we performed SWATH mass spectrometry analysis to detect age-related shifts in protein expression that occur in young, middle-aged, old, and late old aged C57BL/6 mice. Detergent-soluble and insoluble proteins were isolated from total protein extracts of hepatic tissues to produce SWATH aging profiles for the identification of aggregation-prone proteins and their respective biological processes. Our results reveal that the proteins present in insoluble liver aggregates of middle- and old aged mouse groups are largely involved in proteostasis-related degradation processes. In summary, we show for the first time that detergent-insoluble protein aggregates containing proteostasis-related components accumulate during natural aging in the mouse liver. Future studies will examine the eligibility of these proteins as targets for anti-aging therapeutic strategies.