Molecular Biology and Morphology of Alternative Macroautophagy
Abstract: Atg5 and Atg7 are considered as essential molecules for induction of macroautophagy. However, we found that cells lacking Atg5 or Atg7 can still form autophagosomes/autolysosomes and perform autophagy-mediated protein degradation when subjected to certain stresses. Although lipidation of LC3 is accepted to be a good indicator of macroautophagy, it did not occur during the Atg5/Atg7-independent alternative macroautophagy. Unlike conventional macroautophagy, autophagosomes seemed to be generated in a Rab9-dependent manner by the fusion of the phagophore with vesicles derived from the trans-Golgi and late endosomes. Mammalian macroautophagy can occur via at least two different pathways, which are an Atg5/Atg7-dependent conventional pathway and an Atg5/Atg7-independent alternative pathway.
Key words: Alternative macroautophagy, Golgi apparatus, LC3, Rab9