title: Dynamic association of the ULK1 complex with omegasomes during autophagy induction.
abstract: Induction of autophagy requires the ULK1 protein kinase complex and the Vps34 lipid kinase complex. PtdIns3P synthesised by Vps34 accumulates in omegasomes, membrane extensions of the ER within which some autophagosomes form. The ULK1 complex is thought to target autophagosomes independently of PtdIns3P, and its functional relationship to omegasomes is unclear. Here we show that the ULK1 complex colocalises with omegasomes in a PtdIns3P-dependent way. Live-cell imaging of Atg13 (a ULK1 complex component), omegasomes and LC3 establishes and annotates for the first time a complete sequence of steps leading to autophagosome formation, as follows. Upon starvation, the ULK1 complex forms puncta associated with the ER and sporadically with mitochondria. If PtdIns3P is available, these puncta become omegasomes. Subsequently, the ULK1 complex exits omegasomes and autophagosomes bud off. If PtdIns3P is unavailable, ULK1 puncta are greatly reduced in number and duration. Atg13 contains a region with affinity for acidic phospholipids, required for translocation to punctate structures and autophagy progression.
authors.affiliation: Signalling Programme, The Babraham Institute, Babraham, Cambridge CB22 3AT,, UK.
authors.forename: Eleftherios
authors.initials: E
authors.lastname: Karanasios
authors.forename: Eloise
authors.initials: E
authors.lastname: Stapleton
authors.forename: Maria
authors.initials: M
authors.lastname: Manifava
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kaizuka
authors.forename: Noboru
authors.initials: N
authors.lastname: Mizushima
authors.forename: Simon A
authors.initials: SA
authors.lastname: Walker
authors.forename: Nicholas T
authors.initials: NT
authors.lastname: Ktistakis
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D001343:Autophagy / Q000235:genetics*; D000071189:Autophagy-Related Protein-1 Homolog; D000071183:Autophagy-Related Proteins; D058546:Class III Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D010588:Phagosomes / Q000378:metabolism; D018129:Phosphatidylinositol Phosphates / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism
chemical_list: C534291:ATG13 protein, human; D048868:Adaptor Proteins, Signal Transducing; D000071183:Autophagy-Related Proteins; D047908:Intracellular Signaling Peptides and Proteins; D046912:Multiprotein Complexes; D018129:Phosphatidylinositol Phosphates; C055525:phosphatidylinositol 3-phosphate; D058546:Class III Phosphatidylinositol 3-Kinases; D000071189:Autophagy-Related Protein-1 Homolog; D017346:Protein Serine-Threonine Kinases; C484754:ULK1 protein, human
keywords: Autophagy; Imaging; Omegasomes; Phosphatidylinositol 3-phosphate; ULK complex