Mitochondrial Efficiency-Dependent Viability of Saccharomyces cerevisiae Mutants Carrying Individual Electron Transport Chain Component Deletions

Abstract

Mitochondria play a crucial role in eukaryotic cells; the mitochondrial electron transport chain (ETC) generates adenosine triphosphate (ATP), which serves as an energy source for numerous critical cellular activities. However, the ETC also generates deleterious reactive oxygen species (ROS) as a natural byproduct of oxidative phosphorylation. ROS are considered the major cause of aging because they damage proteins, lipids, and DNA by oxidation. We analyzed the chronological life span, growth phenotype, mitochondrial membrane potential (MMP), and intracellular ATP and mitochondrial superoxide levels of 33 single ETC component-deleted strains during the chronological aging process. Among the ETC mutant strains, 14 (sdh1Δ, sdh2Δ, sdh4Δ, cor1Δ, cyt1Δ, qcr7Δ, qcr8Δ, rip1Δ, cox6Δ, cox7Δ, cox9Δ, atp4Δ, atp7Δ, and atp17Δ) showed a significantly shorter life span. The deleted genes encode important elements of the ETC components succinate dehydrogenase (complex II) and cytochrome c oxidase (complex IV), and some of the deletions lead to structural instability of the membrane-F1F0-ATP synthase due to mutations in the stator stalk (complex V). These short-lived strains generated higher superoxide levels and produced lower ATP levels without alteration of MMP. In summary, ETC mutations decreased the life span of yeast due to impaired mitochondrial efficiency.

Iron Supplementation Delays Aging and Extends Cellular Lifespan through Potentiation of Mitochondrial Function

“…Thus, these findings suggest that iron supplementation increases the level of ATP which is required for the extension of cellular lifespan. Our results are consistent with the previous reports showing the role of ATP in the cellular lifespan [ 51 , 64 , 65 ]. Further, we utilized iron supplementation to enhance the mitochondrial functions and rescued the short lifespan and oxidative stress-sensitive phenotype of the AMPK mutant.…”

Iron Supplementation Delays Aging and Extends Cellular Lifespan through Potentiation of Mitochondrial Function

“…Thus, these findings suggest that iron supplementation increases the level of ATP which is required for the extension of cellular lifespan. Our results are consistent with the previous reports showing the role of ATP in the cellular lifespan [ 51 , 64 , 65 ]. Further, we utilized iron supplementation to enhance the mitochondrial functions and rescued the short lifespan and oxidative stress-sensitive phenotype of the AMPK mutant.…”

Metabolic profiling of isolated mitochondria and cytoplasm reveals compartment-specific metabolic responses

“…Even though complex II activity is blocked in sdh2 Δ, reducing equivalents can be transferred to the electron transport chain via the NADH-dehydrogenases in the inner membrane (Marres et al 1991 ; Luttik et al 1998 ). This is supported by Kwon et al ( 2015 ), showing a slightly decreased oxygen consumption rate in sdh2 Δ cells and no oxygen consumption in atp4 Δ cells.…”

The mitochondrial copper chaperone COX11 has an additional role in cellular redox homeostasis

“…This shows that the loss of the COX complex and respiratory deficiency on their own do not explain the observed PQ hypersensitivity of the Δ Sccox11 Δ Scsod1 strain. We confirmed this further by testing the PQ sensitivity of the Δ Sccyt1 Δ Scsod1 yeast strain, which lacks Cytochrome c1 from the third respiratory (cytochrome b) complex and is also respiratory deficient ( S3C Fig ) [ 30 ]. Similar to the Δ Sccox7 Δ Scsod1 results, the growth of the Δ Sccyt1 Δ Scsod1 strain was comparable to the Δ Scsod1 single mutant ( S3D Fig ).…”

Iron Supplementation Delays Aging and Extends Cellular Lifespan through Potentiation of Mitochondrial Function

“…Thus, these findings suggest that iron supplementation increases the level of ATP which is required for the extension of cellular lifespan. Our results are consistent with the previous reports showing the role of ATP in the cellular lifespan [ 51 , 64 , 65 ]. Further, we utilized iron supplementation to enhance the mitochondrial functions and rescued the short lifespan and oxidative stress-sensitive phenotype of the AMPK mutant.…”

Metabolic profiling of isolated mitochondria and cytoplasm reveals compartment-specific metabolic responses

“…Even though complex II activity is blocked in sdh2 Δ, reducing equivalents can be transferred to the electron transport chain via the NADH-dehydrogenases in the inner membrane (Marres et al 1991 ; Luttik et al 1998 ). This is supported by Kwon et al ( 2015 ), showing a slightly decreased oxygen consumption rate in sdh2 Δ cells and no oxygen consumption in atp4 Δ cells.…”

The mitochondrial copper chaperone COX11 has an additional role in cellular redox homeostasis

“…This shows that the loss of the COX complex and respiratory deficiency on their own do not explain the observed PQ hypersensitivity of the Δ Sccox11 Δ Scsod1 strain. We confirmed this further by testing the PQ sensitivity of the Δ Sccyt1 Δ Scsod1 yeast strain, which lacks Cytochrome c1 from the third respiratory (cytochrome b) complex and is also respiratory deficient ( S3C Fig ) [ 30 ]. Similar to the Δ Sccox7 Δ Scsod1 results, the growth of the Δ Sccyt1 Δ Scsod1 strain was comparable to the Δ Scsod1 single mutant ( S3D Fig ).…”

Iron Supplementation Delays Aging and Extends Cellular Lifespan through Potentiation of Mitochondrial Function

“…Thus, these findings suggest that iron supplementation increases the level of ATP which is required for the extension of cellular lifespan. Our results are consistent with the previous reports showing the role of ATP in the cellular lifespan [ 51 , 64 , 65 ]. Further, we utilized iron supplementation to enhance the mitochondrial functions and rescued the short lifespan and oxidative stress-sensitive phenotype of the AMPK mutant.…”

Metabolic profiling of isolated mitochondria and cytoplasm reveals compartment-specific metabolic responses

“…Even though complex II activity is blocked in sdh2 Δ, reducing equivalents can be transferred to the electron transport chain via the NADH-dehydrogenases in the inner membrane (Marres et al 1991 ; Luttik et al 1998 ). This is supported by Kwon et al ( 2015 ), showing a slightly decreased oxygen consumption rate in sdh2 Δ cells and no oxygen consumption in atp4 Δ cells.…”

The mitochondrial copper chaperone COX11 has an additional role in cellular redox homeostasis

“…This shows that the loss of the COX complex and respiratory deficiency on their own do not explain the observed PQ hypersensitivity of the Δ Sccox11 Δ Scsod1 strain. We confirmed this further by testing the PQ sensitivity of the Δ Sccyt1 Δ Scsod1 yeast strain, which lacks Cytochrome c1 from the third respiratory (cytochrome b) complex and is also respiratory deficient ( S3C Fig ) [ 30 ]. Similar to the Δ Sccox7 Δ Scsod1 results, the growth of the Δ Sccyt1 Δ Scsod1 strain was comparable to the Δ Scsod1 single mutant ( S3D Fig ).…”