Most aging hypotheses revolve around the accumulation of some sort of damage resulting in gradual physiological decline and ultimately death. Avoiding protein damage accumulation by enhanced turnover should slow down the aging process and extend lifespan. However, lowering translational efficiency extends rather than shortens lifespan in C. elegans. We studied turnover of individual proteins in the conserved Insulin/Insulin-like Growth Factor (IGF-1) receptor mutant daf-2 by combining Stable Isotope Labeling by Nitrogen in Caenorhabditis elegans (SILeNCe) and accurate mass spectrometry. Intriguingly, the majority of proteins displayed prolonged half-lives in daf-2, while others remained unchanged, signifying that longevity is not supported by high protein turnover. This slow-down of protein turnover was most prominent for components of the translation machinery and mitochondria. In contrast, the high turnover of lysosomal hydrolases and very low turnover of cytoskeletal proteins remained largely unchanged in daf-2. The slow-down of protein dynamics and low abundance of the translational machinery may point at the importance of anabolic attenuation in lifespan extension as suggested by the hyperfunction theory.
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