Tsa1-Mediated Regulation of PKA Tunes Trehalose Metabolism in Saccharomyces cerevisiae

Cells continuously adjust their metabolism to adapt to changing nutrient conditions, a process that in yeast requires tight coordination between metabolic and stress-response pathways. The peroxiredoxin Tsa1, the main cytosolic 2-Cys peroxiredoxin in Saccharomyces cerevisiae , is well-known for its antioxidant role, but there is an increased interest in understanding its contribution to metabolic regulation. Here we show that Tsa1 exerts a broad regulatory influence on central carbon metabolism, through modulation of the Ras/cAMP/PKA nutrient-signalling pathway. Using dynamic flux balance analysis, we demonstrate that deletion of TSA1 leads to a marked reduction in gluconeogenic flux during the post-diauxic phase, resulting in diminished trehalose and glycogen accumulation. The tsa1 Δ mutant displays persistent PKA activation under glucose-depleted conditions, evidenced by sustained phosphorylation of the trehalase Nth1 and impaired nuclear localization of the stress-responsive transcription factor Msn2. Consequently, genes under Msn2/4 control, including those involved in trehalose synthesis, are repressed. Despite normal abundance and activity of the trehalose synthase complex, increased Nth1 protein levels and activity indicate enhanced PKA-dependent trehalose degradation in the absence of Tsa1. Moreover, tsa1 Δ cells exhibit altered cell size homeostasis and defective cell cycle re-entry following glucose replenishment, linking Tsa1-mediated metabolic regulation to proliferative control. Our results show the regulatory function of Tsa1 as a negative modulator of PKA signalling, coordinating the balance between stress protection, carbohydrate metabolism and growth. This study establishes Tsa1 as a key integrative node connecting metabolic and cell cycle regulation in yeast.