ATAD3B is a mitophagy receptor mediating clearance of oxidative stress-induced damaged mitochondrial DNA (2021)
Figure 1

Figure 1. Mitophagy is required for the clearance of oxidative stress-induced damaged mtDNA

Assessment of mtDNA damage by quantitative PCR. HEK293 cells infected with control (empty vector) or shATG5 for 5 days. Cells were then incubated with DMSO or 4 mM 3-NPA for 2 h and either immediately harvested or washed with fresh medium and incubated for another 1 h. Cells with or without washout were used for the extraction of total DNA. All DNA samples were used for amplification of 8.9 kb mtDNA fragment using quantitative PCR and were normalized to amplification of a 221 bp mtDNA fragment. PCR products were quantitated by PicoGreen staining using Micro Plate Reader. Data are presented as mean ± SD (n = 3 independent experiments), statistical significance was assessed by two-tailed student's t-test, N.S., not significant, *p < 0.05, **p < 0.01.

The data in (A) were further calculated for the frequency of mtDNA damage. The equation was seen in "Materials and Methods". Data are presented as mean ± SD (n = 3 independent experiments), statistical significance was assessed by a two-tailed student's t-test, N.S., not significant, **p < 0.01.

Representative images show 8-oxo-dG staining. Control or shATG5 HeLa cells were treated with DMSO, 200 µM H2O2, or 4 mM 3-NPA for 2 h, and then either fixed immediately or washed with fresh medium and incubated for another 1 h. Cells were immunostained with DAPI and anti-8-oxo-dG antibody and analyzed by confocal microscopy. Scale bar, 10 µm.

Quantification of the relative 8-oxo-dG fluorescence intensity in (C). Data are presented as mean ± SD (n = 3 independent experiments, 20 cells per experiment), statistical significance was assessed by a two-tailed student's t-test, N.S., not significant, *p < 0.05, **p < 0.01.

Control or shATG5 HEK293 cells stably expressing mito-Keima. Control cells were treated with DMSO, 200 µM H2O2, or 4 mM 3-NPA for 2 h, and shATG5 cells were treated with 200 µM H2O2 as a negative control. Cells were then imaged with 458 nm (measuring mitochondria with a neutral pH) and 561 nm (measuring mitochondria with an acidic pH) laser excitation for mito-Keima by confocal microscopy. Right panels show the pixel intensity of red (mitochondria within lysosomes) and green (mitochondria in the cytoplasm) from a line. Scale bar, 10 µm.

Quantification of the relative ratio of red to green fluorescence intensity (561 nm/458 nm) of the cells described in (E). Data are presented as mean ± SD (n = 3 independent experiments, 20 cells per experiment), statistical significance was assessed by a two-way ANOVA, N.S., not significant, **p < 0.01.

HeLa cells expressing GFP-LC3 were treated with DMSO, 200 µM H2O2, or 4 mM 3-NPA for 2 h. Cells were stained with anti-Tom20 and anti-DNA antibodies, then analyzed by confocal microscopy. The white arrows were indicated the LC3 punta colocalizing or contacting with mtDNA/Tom20. Scale bar, 10 µm.

Quantification of the LC3 punta colocalizing or contacting with mtDNA/Tom20 in a cell. n = 30 cells from 3 coverslips, Data are presented as mean ± SD (n = 30), statistical significance was assessed by a one-way ANOVA with Tukey's multiple comparisons test, ***p < 0.001.