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. Author manuscript; available in PMC: 2010 Sep 1.
Published in final edited form as: Biochim Biophys Acta. 2009 Feb 6;1793(9):1496–1507. doi: 10.1016/j.bbamcr.2009.01.016

Figure 1.

Figure 1

A schematic representation of the macroautophagy process. Following induction, a phagophore or isolation membrane is formed. This process is regulated by Atg1 (Ulk1), Atg9, and the PtdIns 3-kinase complex, which includes Beclin 1, Atg14L, and UVRAG (nucleation). Two ubiquitin-like conjugation systems, which produce Atg8-PE (LC3II) and Atg5-Atg12, mediate the elongation of the isolation membrane, closure, and the formation a double-membrane vacuole known as the autophagosome. Autophagosomes can undergo maturation and fusion with early and late endosomes and MVBs, to generate the amphisome, followed by fusion with lysosomes, to form the autolysosome. Trafficking, maturation, and fusion events are mediated by microtubules and specific SNARE and Rab proteins. ESCRT proteins are also essential for MVB fusion with autophagosomes. Alternatively, immature autophagosomes can fuse directly with lysosomes.