Autophagy: a forty-year search for a missing membrane source

Abbreviations: Atg, autophagy-related gene; ER, endoplasmic reticulum; IM, isolation membrane; PAS, preautophagosomal structure Autophagy is the major self-degradative process in eukaryotic cells, with fundamental roles in cellular and organismal homeostasis, and is involved in many developmental and pathological situations. Little was known about the molecular mechanisms of autophagy until the last decade, when yeast genetic screens revealed ~27 autophagy-related genes (Atg), whose products are necessary for autophagy [16].\n Similarly, conventional vesicular structures have not been observed by electron microscopy at the PAS in yeast, although retrograde transport of some Atg proteins has recently been demonstrated, presumably involving a vesicular mechanism [23].