Fig. 8. The Rab10-EHBP1-EHD2 complex mediates the engulfment of LDs by autophagic organelles.
(A) Live-cell confocal fluorescence microscopy of two distinct LDs (stained with MDH, blue) from Hep3B cells expressing either mCherry-Rab10 (top series) or GFP-Rab10 (lower series). Imaging reveals the association of LD-bound Rab10 at early time points with phagophore/autophagosome-associated Rab10 (0 s) extending to nearly surround the perimeter of LDs at later time points. Dashed outlines provide fiducial points of reference as the envelopment of the LD by the phagophore progresses. These events are representative of data from more than 30 individual cells examined by live-cell imaging. (B and C) Quantification of the percentage of LDs associated with LC3- or Atg16L1-positive structures in Hep3B hepatoma cells after 48-hour siRNA treatment with the indicated siRNAs (Tri-siRNA, triple knockdown). Cells were preloaded with 150 μM oleic acid overnight. (D and E) Quantification of the percentage of LDs associated with LC3- or Atg16L1-positive structures after culture in low-serum conditions in WT or Rab10 KO MEFs. Cells were preloaded with 400 μM oleic acid overnight. (F) Quantification of the percentage of LDs associated with LAMP1-positive structures after 48-hour siRNA treatment followed by 48-hour starvation from n = 3 independent experiments, measuring 20 cells per condition. Cells were preloaded with 150 μM oleic acid overnight. (G and H) LDs visualized from WT or Rab10 KO MEFs were divided into three groups on the basis of their association with LAMP-1: “none,” “attached,” or “engulfed” (G). Manual counting of LDs (H) in each group from WT and Rab10 KO MEFs. The graphs represent observations from n = 3 independent experiments, measuring 20 cells per condition. Cells were preloaded with 400 μM oleic acid overnight. Data are represented as means ± SD. *P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001. Scale bars, 1 μm.