Autophagosome formation from membrane compartments enriched in phosphatidylinositol 3-phosphate and dynamically connected to the endoplasmic reticulum

• Published in: The Journal of cell biology 2008-08, Vol.182 (4), p.685-701
• Main Authors: Axe, Elizabeth L, Walker, Simon A, Manifava, Maria, Chandra, Priya, Roderick, H. Llewelyn, Habermann, Anja, Griffiths, Gareth, Ktistakis, Nicholas T
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino Acids; Animals; Autophagy; Biochemistry; Carrier Proteins - chemistry; Carrier Proteins - metabolism; Cell Compartmentation; Cell Line; Cell lines; Cell Survival; Cellular biology; Clone Cells; Down-Regulation; Endoplasmic Reticulum - enzymology; Endoplasmic Reticulum - metabolism; Endoplasmic Reticulum - ultrastructure; Endosomes; Green Fluorescent Proteins - metabolism; Humans; Imaging; Intracellular Membranes - metabolism; Intracellular Membranes - ultrastructure; Membranes; Microtubule-Associated Proteins - metabolism; Models, Biological; Molecular Sequence Data; P branes; Phagosomes - enzymology; Phagosomes - metabolism; Phagosomes - ultrastructure; Phosphates; Phosphatidylinositol 3-Kinases - metabolism; Phosphatidylinositol Phosphates - metabolism; Phosphatidylinositols; Protein Structure, Tertiary; Protein Transport; Proteins; Rats; Recombinant Fusion Proteins - metabolism; Small interfering RNA; Starvation; Stem cells; Yeasts
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.200803137

Autophagy is the engulfment of cytosol and organelles by double-membrane vesicles termed autophagosomes. Autophagosome formation is known to require phosphatidylinositol 3-phosphate (PI(3)P) and occurs near the endoplasmic reticulum (ER), but the exact mechanisms are unknown. We show that double FYVE domain-containing protein 1, a PI(3)P-binding protein with unusual localization on ER and Golgi membranes, translocates in response to amino acid starvation to a punctate compartment partially colocalized with autophagosomal proteins. Translocation is dependent on Vps34 and beclin function. Other PI(3)P-binding probes targeted to the ER show the same starvation-induced translocation that is dependent on PI(3)P formation and recognition. Live imaging experiments show that this punctate compartment forms near Vps34-containing vesicles, is in dynamic equilibrium with the ER, and provides a membrane platform for accumulation of autophagosomal proteins, expansion of autophagosomal membranes, and emergence of fully formed autophagosomes. This PI(3)P-enriched compartment may be involved in autophagosome biogenesis. Its dynamic relationship with the ER is consistent with the idea that the ER may provide important components for autophagosome formation.