Figure 4: PtdIns(3)P in yeast autophagic membranes.
From: Yeast and mammalian autophagosomes exhibit distinct phosphatidylinositol 3-phosphate asymmetries
(a) Wild-type yeast cultured in S(-NC) for 4 h. PtdIns(3)P was labelled intensely in the EF of autophagic body membranes in the vacuolar lumen. A lower amount of labelling was also seen in the PF of autophagic body membranes. Scale bar, 0.5 μm. (b) Diagrams showing the membrane topologies of autophagic bodies in freeze-fracture EM. Autophagic bodies are observed as single-membrane structures in the vacuolar lumen. When an autophagic body appears as a convex structure the observed layer is the PF, whereas when it appears as a concave structure the observed layer is the EF. (c) Labelling intensity of PtdIns(3)P in wild-type yeast cultured in S(-NC) for 4 h (average±s.e.m.). PtdIns(3)P was found in both leaflets of the autophagosome and autophagic body membrane, and the labelling was much stronger in the EF than in the PF. In the vacuolar membrane, significant labelling was found in the EF, albeit at much lower levels than in the PF. The experiment was repeated three times, and the number of colloidal gold particles per μm2 was measured in more than ten randomly selected images.
