An autophagosome is a unique, double-membraned organelle that is a key component of macroautophagy (a type of autophagy). Its formation is the first step in autophagy after the genesis of a phagophore, and it mediates the sequestering of cytosolic macromolecules.
Once autophagy is stimulated by the inactivation of mTOR, vesicles containing Atg9 proteins form the isolation membrane at the nucleation site. An Atg5-Atg12-Atg16 complex forms at the site of expansion on the isolation membrane, where it can mediate the fusion of vesicles containing light-chain 3 proteins (LC3) with the isolation membrane. The isolation membrane will continue to grow around the target cell component until a sealed double-membrane structure has completely formed - the autophagosome.
- ↑ Lodish H, Berk A, Kaiser CA, Krieger M, Bretscher A, Ploegh H, Amon A, Scott MP. Molecular Cell Biology. 7th edition. New York: Macmillan Higher Education; 2013