Figure 3: PtdIns(3)P in yeast autophagosomes.
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 autophagosomal membranes. A lower but still significant amount of labelling was also seen in the PF of autophagosome membranes as well as in the EF of the vacuolar membrane. Scale bar, 0.5 μm. (b) Autophagosomes in wild-type yeast cultured in S(-NC) for 4 h. The autophagosome was identified as a smooth-surfaced double-membrane structure, and seen in two different patterns, as shown in the diagrams in c. Upper panel: convex structures displaying the outer membrane EF and the inner membrane PF. Lower panel: concave structures displaying the outer membrane PF and the inner membrane EF. In both cases, PtdIns(3)P was labelled more intensely in the EF than in the PF. Scale bars, 0.2 μm. (c) Diagrams showing the membrane topologies of autophagosomes in freeze-fracture EM. Autophagosomes are observed as smooth-surfaced double-membrane structures in the cytoplasm. The outer and inner membranes can be distinguished based on the convexity or concavity of the structure, and whether the membrane appears as the near-side or far-side layer.
