Immunogold Electron Microscopy of the Autophagosome Marker LC3

Even though autophagy was firstly observed by transmission electron microscopy already in the 1950s (reviewed in Eskelinen et al., 2011), nowadays this technique remains one of the most powerful systems to monitor autophagic processes. The autophagosome, an LC3-positive double membrane structures enclosing cellular materials, represents the key organelle in autophagy and its simple visualization and/or numeration allow to draw important conclusions about the autophagic flux. Therefore, the accurate identification of autophagosomes is crucial for a comprehensive and detailed dissection of autophagy. Here we present a simple protocol to identify autophagosomes by transmission electron microscopy coupled to immunogold labeling of LC3 starting from a relatively low cell number, which we recently developed to follow the autophagic pathway during viral-mediated human carcinogenesis.