Figure S5.
Additional control experiments and a model relating potassium ion homeostasis to mitochondrial function through the activity of transporter Trk1p. (A) Internal potassium as a function of external potassium including data for WT (blue) or sis2Δ mutants (orange) grown in ammonium and 200 mM KCl. (B) MMPs as a function of internal potassium for conditions shown in A. (C) Lifespan curves of strains grown in 7.35 mM (dark) or 200 mM (light) KCl. Data are from two experiments with n = 3,214 for WT and n = 2,789 for sis2Δ. (D) Cell diameter distributions of a representative young, exponentially growing culture (blue) and a culture that has been aged 48 h on the MAD (orange). (E) Concentration of potassium in the exponentially growing cultures (blue) and two estimates for old cells in the 48-h culture (right peak of orange curve). “Old” (purple) was calculated by assuming that daughters of old cells (left peak of orange curve in D) have same potassium content of cells from an exponential culture (blue curve in D). “Old max.” (brown) provides the maximum upper bound on the potassium concentration of old cells, by making the (unlikely) assumption that daughters of old cells contain no potassium. Data are from two experiments, with three replicate “young” and old cultures per experiment. (F and G) RNAseq data from cultures grown in typical (7.35 mM, F) and low (0.5 mM, G) external potassium. Maximum -log10(p adj.) was capped at 20. Truncated values are indicated by an “x.” (H) Gene set enrichments (Materials and methods) for genes with less expression in sis2Δ vs WT in both potassium environments. (I) Mitochondria isolated from sis2Δ mutants were treated as in Fig. 7 A. Slopes of -adp, -fccp and +adp, -fccp conditions are significantly different from zero (P < 0.001 in each case). Differences between -adp, -fccp (green) and +adp, -fccp (orange) at KCl concentrations below 250 mM are significant with P ≤ 0.01. The difference between these groups at 250 mM is not significant (P = 0.54). (J) MMP (as measured by the TMRM ratio) of isolated mitochondria incubated in the indicated buffers. After measuring the TMRM ratio, FCCP was added to dissipate the MMP and samples were measured again. Data are from two experiments, with three replicates per condition. In all cases, error bars show 95% CIs. In J, error bars are smaller than the points. (K) Model depicting the relationship between potassium ion homeostasis and mitochondrial function.

Additional control experiments and a model relating potassium ion homeostasis to mitochondrial function through the activity of transporter Trk1p. (A) Internal potassium as a function of external potassium including data for WT (blue) or sis2Δ mutants (orange) grown in ammonium and 200 mM KCl. (B) MMPs as a function of internal potassium for conditions shown in A. (C) Lifespan curves of strains grown in 7.35 mM (dark) or 200 mM (light) KCl. Data are from two experiments with n = 3,214 for WT and n = 2,789 for sis2Δ. (D) Cell diameter distributions of a representative young, exponentially growing culture (blue) and a culture that has been aged 48 h on the MAD (orange). (E) Concentration of potassium in the exponentially growing cultures (blue) and two estimates for old cells in the 48-h culture (right peak of orange curve). “Old” (purple) was calculated by assuming that daughters of old cells (left peak of orange curve in D) have same potassium content of cells from an exponential culture (blue curve in D). “Old max.” (brown) provides the maximum upper bound on the potassium concentration of old cells, by making the (unlikely) assumption that daughters of old cells contain no potassium. Data are from two experiments, with three replicate “young” and old cultures per experiment. (F and G) RNAseq data from cultures grown in typical (7.35 mM, F) and low (0.5 mM, G) external potassium. Maximum -log10(p adj.) was capped at 20. Truncated values are indicated by an “x.” (H) Gene set enrichments (Materials and methods) for genes with less expression in sis2Δ vs WT in both potassium environments. (I) Mitochondria isolated from sis2Δ mutants were treated as in Fig. 7 A. Slopes of -adp, -fccp and +adp, -fccp conditions are significantly different from zero (P < 0.001 in each case). Differences between -adp, -fccp (green) and +adp, -fccp (orange) at KCl concentrations below 250 mM are significant with P ≤ 0.01. The difference between these groups at 250 mM is not significant (P = 0.54). (J) MMP (as measured by the TMRM ratio) of isolated mitochondria incubated in the indicated buffers. After measuring the TMRM ratio, FCCP was added to dissipate the MMP and samples were measured again. Data are from two experiments, with three replicates per condition. In all cases, error bars show 95% CIs. In J, error bars are smaller than the points. (K) Model depicting the relationship between potassium ion homeostasis and mitochondrial function.

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