The impact of reductive stress on cells and the influence of genetic and environmental factors

Abstract

Depletion of glutathione (GSH) has been linked to oxidative stress and perturbations in iron homeostasis. Little is known about how excess cellular GSH affects cells except that cells can experience excess GSH-associated reductive stress. Additionally, the mechanisms that cells possess that maintain the upper threshold of GSH to avoid GSH accumulation remain elusive. The aim of this study was to identify and understand the pathways that work to ensure GSH homeostasis is maintained when intracellular GSH levels are in excess. A genome-wide approach was implemented which involved screening the Saccharomyces cerevisiae (S. cerevisiae) non-essential gene deletion and gene overexpression collections with high concentration exogenous GSH (80mM and 40mM GSH respectively). The deletion of 156 non-essential genes caused sensitivity whilst the loss of 31 non-essential genes conferred resistance to exogenous GSH. Furthermore, the over-expression of 240 genes caused sensitivity to GSH treatment whilst the overexpression of only 1 gene resulted in resistance. To identify strains that play a role in GSH homeostasis maintenance, the non-physiological cell permeable reductant dithiothreitol (DTT) was used. The use of DTT identified 31 non-essential genes, when deleted and 72 genes, when over-expressed, which caused sensitive to only GSH (and not DTT) treatment and the deletion of 24 genes which resulted in resistance. Focused studies identified that inhibition of TORC1 mediated by the SEACIT pathway, the SPS sensor system and the nitrogen catabolite repression pathway are all involved in cellular response to GSH-induced reductive stress. Furthermore, findings of this study implicate Ecm38p as having a more pivotal role in GSH degradation and that the dipeptidase Yol057wp may possess cys-gly cleavage activity. The outcomes of this study can contribute to better understanding the mechanisms involved in diseases such as Alzheimer's disease which are associated with excess GSH-induced stress whilst also having biotechnological applications in wine production.

Date of Award	2021
Original language	English