(a) and (b) Lysates prepared from HeLa cells treated with GSNO (50 μM) and/or CCCP (10 μM) for different time periods as indicated were immunoblotted with anti-Tom20, anti-HSP60 and anti-beta-actin antibodies (upper panel). The quantity of Tom20 (a) and HSP60 (b), as measured by scanning densitometry, is expressed as a percentage of control, normalized with respect to beta-actin (lower panel). Data shown are mean ± SE (n = 4); **p < 0.01 versus GSNO-untreated samples, and # means p < 0.01 versus control. (c) and (d) HeLa cells transfected with the Venus-tagged parkin expression plasmid were incubated with GSNO (50 μM) and/or CCCP (10 μM) for different time periods as indicated, and then immunostained with anti-Tom20 antibody. The compaction index was calculated from the images stained with anti-Tom20 antibody as described in Materials and Methods (c). The data used for the wild-type cells without CCCP was the same data as in Figure 1e. Data shown are mean ± SE (n = 15); **p < 0.01 versus GSNO-untreated samples. The quantity of Tom20, as measured from scanned images using ImageJ (NIH), is expressed as a percentage of parkin-negative cells (d). Data shown are mean ± SE (n = 10); **p < 0.01 versus GSNO-untreated cells. Full scans of the blots in a and b are available in Supplementary Information, Fig.S10.