cysteine toxicity drives age related mitochondrial decline

1. Introduction

1.1. 1.Lysosome like vacuoles compartmentalize amino acids thus maintaining mitochondrial respiration.

1.2. 2. Poor vacuole function due to improper acidification leads to poor compartmentalization, which leads to decrease in intracellular iron level, which in turn affects mitochondrial respiration

1.3. 3. Cysteine is most toxic in this way for mitochondrial respiration

2. Methods

2.1. growth experiment of yeast cells in glycerol media . cells that were vph-null and vma-null or Conconamycin A treated in comparison with normal cells to find out the role of vacuoles in yeast cell growth

2.2. imaging of mitochondrial structure and estimation of mitochondrial membrane potential of above mentioned cells

2.3. overexpression assay and single gene deletion assay of genes to find out which gene can suppress the effect of vacuole-activity inhibition

2.4. overexpression of the inhibitor protein found above and iron supplementation of cells

2.5. localization study of Aft1 upon vacuole dysfunction

2.6. measurement of amount of ISC proteins upon inhibition of vacuoles

2.7. measurement of amount of mitochondrial respiratory complexes in vacuole inhibited cells and to find out which amino acid affects mitochondrial respiration the most, individual amino acids are added to vacuole-inhibited cells grown in minimal media

3. doi: https://doi.org/10.1016/j.cell.2019.12.035

4. Results

4.1. 1.impairment of vacuole acidification or inhibition of vacuoles inhibits proper growth of cells and also disrupts mitochondrial structure and function

4.2. Activation of FET4 or deletion of ROX1 resurrected iron homeostasis, thus reversing the effect of vacuole inhibition

4.3. Iron supplementation reversed the effect of vacuole inhibition, and so did overexpression of inhibitor FET4

4.4. Aft1 localized quickly to nucleus upon vacuole inhibition

4.5. Amount of ISC proteins decreased upon vacuole inhibition

4.6. Mitochondrial respiratory complex 2 and 3 level decreased

4.7. Cysteine was found to be most toxic as it sequestered intracellular iron level.

5. Discussion

5.1. Amino acids are sequestered into vacuoles via their proton gradient and this maintains intracellular iron level.

5.2. Defect of vacuole acidification increases intracellular amino acid level which sequesters intracellular iron molecules

5.3. Decrease of intracellular iron level impairs mitochondrial respiration, as the ISCs are not formed properly