Metabolic Regulation of Copper Homeostasis Governs the Sec61-Dependent Protein Translocation Process in <i>Saccharomyces cerevisiae</i>

The concentration of cellular labile pool of copper must be strictly regulated because disruption in copper homeostasis results in diseases. In <i>Saccharomyces cerevisiae</i>, elevated levels of labile copper impair cell viability by inhibiting Sec61-mediated protein translocation into the endoplasmic reticulum. We investigated how metabolic pathways, specifically mitochondrial respiration and autophagy, contribute to copper homeostasis and the translocation of secretory proteins. We show that copper selectively inhibits protein translocation in yeast cells grown in minimal medium but not in a rich medium, highlighting a critical role of nutrients in modulating copper toxicity. Supplementation of specific amino acids suppresses the copper-induced defects in protein translocation and cell death, identifying amino acids as suppressors of the copper toxicity. Using a panel of gene deletion mutants affecting mitochondrial functions, autophagy, peroxisomes, and lipid droplets, we demonstrate that metabolic pathways regulate subcellular concentration of copper and translocation of secretory proteins. Further, disruption of redox and pH homeostasis, and pharmacological inhibition of respiration, reveals that correct subcellular concentration of copper is essential to prevent inhibitory effects on protein translocation. Together, our findings provide mechanistic insights into how metabolic status influences cellular copper homeostasis and the secretory pathway of proteins, with broader implications for understanding diseases of copper metabolism.