Respiratory supercomplexes act as a platform for complex III-mediated maturation of human mitochondrial complexes I and IV (2019)
Figure 2

Figure 2: Reduced steady-state levels of structural MRC subunits in ∆4-CYB cells.

(A) Scatter plot generated from the peptide content analyzed by mass spectrometry in each of the 64 slices excised from BNGE and after quantifying the heavy to light (H/L) and (L/H) ratios in both reciprocal labeling experiments performed with mitochondria isolated from WT and ∆4-CYB cells (see also Figure EV1). The logarithmic ratios were calculated using MaxQuant (Cox & Mann, 2008) and the statistical significance of the differences for the enrichment or depletion of the proteins were determined with Perseus (Cox & Mann, 2011, Tyanova et al., 2016).

(B) Labeling of the thirteen mtDNA-encoded MRC structural subunits. Cells were incubated with [35S]-L-Met for one hour in the presence of emetine 100 μg/ml to inhibit cytoplasmic translation.

(C) Immunodetection of complex III structural subunits on Western blots of total cell lysates separated by SDS-PAGE, from three independent replicates of WT and ∆4-CYB cells. The graph shows the densitometric quantification of the signals corresponding to each subunit normalized to that of the β-Actin. The mean of the three control (WT) samples was set to 1.0 and all the measurements were referenced to that value. The values plotted in the graphs are the mean ± SD (n=3). 2-way ANOVA with Sidak's multiple comparisons test ****p<0.0001; ***p=0.0007.

(D) Immunodetection of complex I structural subunits on Western blots of total cell lysates separated by SDS-PAGE, from three independent replicates of WT and ∆4-CYB cells. The graph shows the densitometric quantification of the signals corresponding to each subunit normalized to that of the β-Actin. The mean of the three control (WT) samples was set to 1.0 and all the measurements were referenced to that value. The values plotted in the graphs are the mean ± SD (n=3). 2-way ANOVA with Sidak's multiple comparisons test ****p<0.0001; **p=0.0024 (NDUFS3); **p=0.0061 (NDUFB8).

(E) Immunodetection of complex IV structural subunits on Western blots of total cell lysates separated by SDS-PAGE, from three independent replicates of WT and ∆4-CYB cells. The graph shows the densitometric quantification of the signals corresponding to each subunit normalized to that of the β-Actin. The mean of the three control (WT) samples was set to 1.0 and all the measurements were referenced to that value. The values plotted in the graphs are the mean ± SD (n=3). 2-way ANOVA with Sidak's multiple comparisons test **p=0.0011.

(F) Immunodetection of complex II structural subunits on Western blots of total cell lysates separated by SDS-PAGE, from three independent replicates of WT and ∆4-CYB cells. The graph shows the densitometric quantification of the signals corresponding to each subunit normalized to that of the β-Actin. The mean of the three control (WT) samples was set to 1.0 and all the measurements were referenced to that value. The values plotted in the graphs are the mean ± SD (n=3). 2-way ANOVA with Sidak's multiple comparisons test ****p<0.0001.

(G) Immunodetection of complex V structural subunits on Western blots of total cell lysates separated by SDS-PAGE, from three independent replicates of WT and ∆4-CYB cells. The graph shows the densitometric quantification of the signals corresponding to each subunit normalized to that of the β-Actin. The mean of the three control (WT) samples was set to 1.0 and all the measurements were referenced to that value. The values plotted in the graphs are the mean ± SD (n=3). There were no differences in the steady-state levels of the tested subunits (2-way ANOVA with Sidak's multiple comparisons test).