Proline metabolism regulates replicative lifespan in the yeast .

In many plants and microorganisms, intracellular proline has a protective role against various stresses, including heat-shock, oxidation and osmolarity. Environmental stresses induce cellular senescence in a variety of eukaryotes. Here we showed that intracellular proline regulates the replicative lifespan in the budding yeast . Deletion of the proline oxidase gene and expression of the γ-glutamate kinase mutant gene that is less sensitive to feedback inhibition accumulated proline and extended the replicative lifespan of yeast cells. Inversely, disruption of the proline biosynthetic genes , and decreased stationary proline level and shortened the lifespan of yeast cells. Quadruple disruption of the proline transporter genes unexpectedly did not change intracellular proline levels and replicative lifespan. Overexpression of the stress-responsive transcription activator gene reduced intracellular proline levels by inducing the expression of , resulting in a short lifespan. Thus, the intracellular proline levels at stationary phase was positively correlated with the replicative lifespan. Furthermore, multivariate analysis of amino acids in yeast mutants deficient in proline metabolism showed characteristic metabolic profiles coincident with longevity: acidic and basic amino acids and branched-chain amino acids positively contributed to the replicative lifespan. These results allude to proline metabolism having a physiological role in maintaining the lifespan of yeast cells.