Mitochondrial respiration is required to provide amino acids during fermentative proliferation of fission yeast

Abstract

When glucose is available, many organisms repress mitochondrial respiration in favour of aerobic glycolysis, or fermentation in yeast, that suffices for ATP production. Fission yeast cells, however, rely partially on respiration for rapid proliferation under fermentative conditions. Here we determined the limiting factors that require respiratory function during fermentation. When the electron transport chain was inhibited, supplementation with arginine was necessary and sufficient to restore rapid cell proliferation. Accordingly, a systematic screen for mutants growing poorly without arginine identified not only mutants defective in arginine synthesis but also mutants defective in mitochondrial oxidative metabolism. Genetic or pharmacological inhibition of respiration triggered a drop in intracellular levels of arginine and amino acids derived from the Krebs-cycle metabolite alpha-ketoglutarate: glutamine, lysine and glutamic acid. Conversion of arginine into these amino acids was required for rapid proliferation when the respiratory chain was blocked. The respiratory block triggered an immediate gene-expression response diagnostic of TOR inhibition, which was muted by arginine supplementation or without the AMPK-activating kinase Ssp1. The TOR-controlled proteins featured biased composition of amino acids reflecting their shortage after respiratory inhibition. We conclude that respiration supports rapid proliferation in fermenting cells of fission yeast by boosting the supply of Krebs-cycle derived amino acids.

Amino acids whose intracellular levels change most during aging alter chronological lifespan of fission yeast

“…We determined absolute concentrations of intracellular amino acids in nmol/6×10 7 cells (eTable 1). The amino-acid quantities, obtained from non-dividing cells, differed from those previously reported for fission yeast which have been obtained from rapidly proliferating cells (21,22). At the onset of stationary phase, the total amino-acid concentrations were lower in pka1Δ than in wild-type cells (Figure 1B).…”

“…Glutamine and aspartate both affect mitochondrial functions which might mediate their lifespan effects. Glutamine, derived from the Krebs-cycle metabolite alpha-ketoglutarate, is one of the amino acids recently shown to become limited when blocking respiration in fermentatively growing S. pombe cells (21). Further experiments will provide mechanistic insights into the roles of glutamine and aspartate during aging.…”

Amino Acids Whose Intracellular Levels Change Most During Aging Alter Chronological Life Span of Fission Yeast

“…We determined absolute concentrations of intracellular amino acids in nmol/6x10 7 cells (eTable 1). The amino-acid quantities, obtained from non-dividing cells, differed from those previously reported for fission yeast which have been obtained from rapidly proliferating cells (21,22). At the onset of stationary phase, the total amino-acid concentrations were lower in pka1Δ than in wild-type cells ( Figure 1B).…”

“…Glutamine and aspartate both affect mitochondrial functions which might mediate their lifespan effects. Glutamine, derived from the Krebs-cycle metabolite alpha-ketoglutarate, is one of the amino acids recently shown to become limited when blocking respiration in fermentatively growing S. pombe cells(21). Amino-acid supplementations at a later timepoint (Day 5) have weaker effects on longevity, likely reflecting the lower viability of the cell population at that time which diminishes any beneficial.…”

Growth-Rate Dependent And Nutrient-Specific Gene Expression Resource Allocation In Fission Yeast

“…Importantly, mitochondrial intermediates are required for amino acid biosynthesis even during fermentative energy generation (Malecki et al 2020). In fission yeast, a single point mutation in the pyruvate kinase Pyk1, affecting its activity, has been shown to rebalance the fluxes through the fermentation and respiration pathways alongside shifts in the transcriptome and proteome composition (Kamrad et al 2020), giving a prime example of how the cell co-adjusts perturbations in metabolic fluxes and expression burdens. Taken together, shifts in the metabolic demand propagate throughout the cell, as most metabolic pathways are tightly interlinked (Chubukov et al 2014).…”