title: Mammalian Atg18 (WIPI2) localizes to omegasome-anchored phagophores and positively regulates LC3 lipidation.
abstract: Autophagosome formation is a complex process that begins with the nucleation of a pre-autophagosomal structure (PAS) that expands into a phagophore or isolation membrane, the precursor of the autophagosome. A key event in the formation of the phagophore is the production of PtdIns3P by the phosphatidylinsitol kinase Vps34. In yeast the two closely related proteins, Atg18 and Atg21, are the only known effectors of PtdIns3P that act in the autophagy pathway. The recruitment of Atg18 or Atg21 to the PAS is an essential step in the formation of the phagophore. Our bioinformatic analysis of the Atg18 and Atg21 orthologues in all eukaryotes shows that WIPI1 and WIPI2 are both mammalian orthologues of Atg18. We show that WIPI2 is a mammalian effector of PtdIns3P and is ubiquitously expressed in a variety of cell lines. WIPI2 is recruited to early autophagosomal structures along with Atg16L and ULK1 and is required for the formation of LC3-positive autophagosomes. Furthermore, when WIPI2 is depleted, we observe a remarkable accumulation of omegasomes, ER-localized PtdIns3P-containing structures labeled by DFCP1 (double FYVE domain-containing protein 1), which are thought to act as platforms for autophagosome formation. In view of our data we propose a role for WIPI2 in the progression of omegasomes into autophagosomes.
authors.affiliation: Secretory Pathways Laboratory, London Research Institute, Cancer Research UK, London, UK.
authors.forename: Hannah E J
authors.initials: HE
authors.lastname: Polson
authors.forename: Jane
authors.initials: J
authors.lastname: de Lartigue
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Rigden
authors.forename: Marco
authors.initials: M
authors.lastname: Reedijk
authors.forename: Sylvie
authors.initials: S
authors.lastname: Urbé
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Clague
authors.forename: Sharon A
authors.initials: SA
authors.lastname: Tooze
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001343:Autophagy; D000071183:Autophagy-Related Proteins; D015415:Biomarkers / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D005786:Gene Expression Regulation; D049452:Green Fluorescent Proteins / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D008055:Lipids / Q000737:chemistry*; D008322:Mammals / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D010588:Phagosomes / Q000378:metabolism*; D028044:Phosphate-Binding Proteins; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D010802:Phylogeny; D011485:Protein Binding; D021381:Protein Transport; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D000071183:Autophagy-Related Proteins; D015415:Biomarkers; D002352:Carrier Proteins; D008055:Lipids; C477012:MAP1LC3A protein, human; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D028044:Phosphate-Binding Proteins; D018129:Phosphatidylinositol Phosphates; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; C522812:WIPI1 protein, human; C569007:WIPI2 protein, human; C426003:ZFYVE1 protein, human; C055525:phosphatidylinositol 3-phosphate; D049452:Green Fluorescent Proteins