RT Journal Article
SR Electronic
T1 Non-canonical autophagy drives alternative ATG8 conjugation to phosphatidylserine
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2020.05.14.096115
DO 10.1101/2020.05.14.096115
A1 Joanne Durgan
A1 Alf H. Lystad
A1 Katherine Sloan
A1 Sven R. Carlsson
A1 Michael I. Wilson
A1 Elena Marcassa
A1 Rachel Ulferts
A1 Judith Webster
A1 Andrea F. Lopez-Clavijo
A1 Michael J. Wakelam
A1 Rupert Beale
A1 Anne Simonsen
A1 David Oxley
A1 Oliver Florey
YR 2020
UL http://biorxiv.org/content/early/2020/05/15/2020.05.14.096115.abstract
AB Autophagy is a fundamental catabolic process essential for development, homeostasis and proper immune function 1. During autophagy, a cascade of ATG proteins target intracellular cargoes for lysosomal degradation and recycling 2. This pathway utilises a unique post-translational modification, the conjugation of ATG8 proteins to phosphatidylethanolamine (PE) at autophagosomes, which modulates cargo selection and maturation. ATG8 lipidation also occurs during non-canonical autophagy, a parallel pathway involving Single Membrane ATG8 Conjugation (SMAC) to endolysosomal compartments, which plays a key role in phagocytosis and other processes 3. It has been widely assumed that SMAC involves the same lipidation of ATG8 to PE, but this has yet to be formally tested. Here, we show that ATG8 undergoes alternative lipidation to phosphatidylserine (PS) during non-canonical autophagy/SMAC. Using mass spectrometry, we find that activation of SMAC, by pharmacological agents 4,5, or during non-canonical autophagy processes such as LC3-associated phagocytosis 6,7 and Influenza A virus infection 8, induces the covalent conjugation of ATG8 to PS, as well as PE. This alternative lipidation event is dependent on the ATG16L1 WD40 domain, and occurs at PS enriched endolysosomal membranes. Importantly, we find that the ATG8-PS and ATG8-PE adducts are differentially delipidated by isoforms of the ATG4 family, indicating significant molecular distinctions and mechanisms between these two species.Together, these results provide an important new insight into autophagy signalling, revealing an alternative form of the hallmark ATG8-lipidation event, so widely used to define and assay autophagy. Furthermore, ATG8-PS lipidation provides a specific ‘molecular signature’ for non-canonical autophagy, uncovering a novel means of detecting and monitoring this emerging pathway.Competing Interest StatementThe authors have declared no competing interest.