Abstract
The selective autophagy pathways of xenophagy and mitophagy are initiated when the adaptor NDP52 recruits the ULK1 complex to autophagic cargo. Hydrogen-deuterium exchange coupled to mass spectrometry (HDX-MS) was used to map the membrane and NDP52 binding sites of the ULK1 complex to unique regions of the coiled coil of the FIP200 subunit. Electron microscopy of the full-length ULK1 complex shows that the FIP200 coiled coil projects away from the crescent-shaped FIP200 N-terminal domain dimer. NDP52 allosterically stimulates membrane-binding by FIP200 and the ULK1 complex by promoting a more dynamic conformation of the membrane-binding portion of the FIP200 coiled coil. Giant unilamellar vesicle (GUV) reconstitution confirmed that membrane recruitment by the ULK1 complex is triggered by NDP52 engagement. These data reveal how the allosteric linkage between NDP52 and the ULK1 complex could drive the first membrane recruitment event of phagophore biogenesis in xenophagy and mitophagy.
Highlights
Autophagy is a cellular process that maintains homeostasis via clearance of cellular components, degradation of damaged organelles and protection against viral and bacterial invasion (Boya, Reggiori, & Codogno, 2013)
Wild-type family interacting protein of 200 kDa (FIP200) was expressed with a glutathione S-transferase (GST) tag fused to the N-terminus and a maltose binding protein (MBP) tag on the C terminus
Density for the GST tag can be seen in the center of the FIP200 N-terminal domain (NTD) dimer (Figure S1B)
Summary
Autophagy is a cellular process that maintains homeostasis via clearance of cellular components, degradation of damaged organelles and protection against viral and bacterial invasion (Boya, Reggiori, & Codogno, 2013). Autophagy entails the de novo formation of a double membrane structure (termed the isolation membrane), maturation into a sealed autophagosome and delivery of substrates to the lysosome for degradation Macroautophagy functions by the initial formation of an isolation membrane at ER exit sites and expands Selective autophagy functions via a set of autophagy adaptor proteins, which bind cargos directly or via polyubiquitin chains (Zaffagnini & Martens, 2016). Selective autophagy pathways for mitochondria (mitophagy), aggregates (aggrephagy), lysosomes (lysophagy), endoplasmic reticulum (ER-phagy), bacteria (xenophagy) and other cargos have been discovered (Zaffagnini & Martens, 2016). Nuclear domain 10 protein 52 (NDP52), optineurin, CCPG1, TAX1BP1 and p62 represent a subset of such adaptors (Kirkin & Rogov, 2019)
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