Yeast and mammalian autophagosomes exhibit distinct phosphatidylinositol 3-phosphate asymmetries

• Published in: Nature communications 2014-02, Vol.5 (1), p.3207-3207, Article 3207
• Main Authors: Cheng, Jinglei, Fujita, Akikazu, Yamamoto, Hayashi, Tatematsu, Tsuyako, Kakuta, Soichiro, Obara, Keisuke, Ohsumi, Yoshinori, Fujimoto, Toyoshi
• Format: Article
• Language: English
• Subjects: 14; 14/28; 631/80/39; 631/80/642/2384; Autophagy; Freeze Fracturing; Humanities and Social Sciences; Humans; Intracellular Membranes - metabolism; multidisciplinary; Phagosomes - metabolism; Phosphatidylinositol Phosphates - metabolism; Phosphoric Monoester Hydrolases - metabolism; Saccharomyces cerevisiae - physiology; Science; Science (multidisciplinary); Staining and Labeling - methods
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms4207

Phosphatidylinositol 3-kinase is indispensable for autophagy but it is not well understood how its product, phosphatidylinositol 3-phosphate (PtdIns(3)P), participates in the biogenesis of autophagic membranes. Here, by using quick-freezing and freeze-fracture replica labelling, which enables determination of the nanoscale distributions of membrane lipids, we show that PtdIns(3)P in yeast autophagosomes is more abundant in the luminal leaflet (the leaflet facing the closed space between the outer and inner autophagosomal membranes) than in the cytoplasmic leaflet. This distribution is drastically different from that of the mammalian autophagosome in which PtdIns(3)P is confined to the cytoplasmic leaflet. In mutant yeast lacking two cytoplasmic phosphatases, ymr1Δ and sjl3Δ , PtdIns(3)P in the autophagosome is equally abundant in the two membrane leaflets, suggesting that the PtdIns(3)P asymmetry in wild-type yeast is generated by unilateral hydrolysis. The observed differences in PtdIns(3)P distribution suggest that autophagy in yeast and mammals may involve substantially different processes. The core mechanisms of autophagy are generally assumed to be broadly conserved between yeast and mammals. Cheng et al . show that the distribution of PtdIns(3)P between cytoplasmic and luminal leaflets of autophagosomes differs dramatically in yeast and mammalian cells, suggestive of different underlying mechanisms.