Revealing the Origin of Autophagosomes – Omegafold

Autophagy is a versatile cellular recycling system that ensures cellular homeostasis by degrading damaged or unwanted cytosolic components. Cytotoxic stress induces the formation of nonselective autophagosomes that degrade bulk cytoplasm. Nonselective autophagosomes emerge from membranes that are thought to be derived from the endoplasmic reticulum. How these membranes, termed omegasomes, are formed remains unknown. We developed a unique model system that allows us to investigate how omegasomes are formed. By targeting a key component of the autophagy machinery to the plasma membrane, we initiated the formation of omegasome-like membranes at the plasma membrane. Our preliminary data show that i) omegasomes are formed by fusion of small donor vesicles, ii) key components involved in autophagy-initiation drives the recruitment and fusion of these vesicles and iii) phagophores emerge from omegasome membranes by remodeling. Based on these observations, we propose an ambitious and multidisciplinary research program to investigate the “origin of autophagosomes”. We will use a combination of live cell imaging, optogenetics, fluorescence lifetime imaging, correlative light-electron microscopy (EM), volume EM and biochemistry to reveal how (i) omegasomes are being formed, (ii) what molecular mechanism are involved, (iii) which sources provide lipids for their formation and (iv) how omegasomes promote the formation of phagophores.