Analysis of the fine morphology of receptor-mediated mitophagy. Serial ultrathin sections of HeLa cells expressing mito-mCherry and GFP-LC3B, which were treated with DFP for 16 h and fixed with a mixture of aldehyde and osmium solutions. (A and B) Representative EM images of protruding (A) and slightly flattened (B) mitochondrial surfaces with tightly attached, electron-dense IMs (arrows). Red arrowheads indicate the frequently observed connections between ER (blue) and IM edges via thin linear/tubular structures. Boxed areas are magnified and shown in insets in A and below the main images in B. Section (sec) numbers are as indicated. Scale bars: 500 nm (lower magnification view) and 100 nm (higher magnification view).