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Abstract
Amino acid deprivation or supplementation can affect cellular and organismal life span, but we know little about the role of concentration changes in free, intracellular amino acids during aging. Here, we determine free amino acid levels during chronological aging of nondividing fission yeast cells. We compare wild-type with long-lived mutant cells that lack the Pka1 protein of the protein kinase A signalling pathway. In wild-type cells, total amino acid levels decrease during aging, but much less so in pka1 mutants. Two amino acids strongly change as a function of age: glutamine decreases, especially in wild-type cells, while aspartate increases, especially in pka1 mutants. Supplementation of glutamine is sufficient to extend the chronological life span of wild-type but not of pka1Δ cells. Supplementation of aspartate, on the other hand, shortens the life span of pka1Δ but not of wild-type cells. Our results raise the possibility that certain amino acids are biomarkers of aging, and their concentrations during aging can promote or limit cellular life span.
Highlights
Dietary restriction extends lifespan and decreases age-related pathologies [1,2]
Isoleucine, threonine and valine extend the chronological lifespan (CLS, the time post-mitotic cells remain viable in stationary phase) [6]
Lifespan is extended by the ip branched chain amino acids (BCAAs: leucine, isoleucine and valine) [9], while in flies, limitation of r BCAAs extends lifespan in a dietary-nitrogen-dependent manner [10]
Summary
Dietary restriction extends lifespan and decreases age-related pathologies [1,2]. These benefits may reflect protein or amino-acid restrictions rather than overall calorie intake [3,4]. Results Quantitative amino-acid analysis during cellular aging We used liquid chromatography selective reaction monitoring [19] to quantify the free, intracellular pools for 19 of the 20 canonical proteogenic amino acids (cysteine was excluded as it is readily t oxidized) during chronological aging of S. pombe wild-type and long-lived pka1Δ deletion-mutant ip cells. The concentration of total free amino acids declined in wild-type but less so in pka1Δ cells, even rising slightly at the last timepoint (Figure 1B).
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