Cells cultured on 8‐well chamber slides were washed with cold PBS, fixed in 4% formaldehyde and permeabilized with 0.1% Triton X‐100. After incubation with 2% normal goat serum (to block nonspecific staining), fixed cells were incubated overnight at 4°C with TOM20 antibody (1:500) (Santa Cruz, USA). Cells were washed with PBS and incubated for 60 min with FITC‐conjugated goat anti‐rabbit IgG (1:500 dilution). The cells were then washed gently with PBS and counterstained with Hoechst 33342 (1:10,000 dilution, Molecular Probes) to visualize nuclei. The coverslips were mounted with SlowFade anti‐fade reagent (Invitrogen), and images were acquired using an All‐in‐One Fluorescence Microscope BZ‐X700 (Keyence; Guo et al, 2013; Qi et al, 2013).