Fig. 4: Knockdown of STX18 activates lipophagy dependent on ATG14.

a Representative fluorescence images of HeLa cells transfected with indicated siRNAs and treated with 200 μM OA for 6 h. Number of LDs in each cell was counted from 50 cells of three independent experiments. b The concentration of TAG in cells was analyzed according to manufacturer’s instructions. c HeLa cells were transfected with STX18 siRNA and treated with 200 μM OA for 12 h and 100 μM CQ for 6 h before cells were fixed and immunostained with anti-LC3. Cells were imaged by confocal microscopy. Number of colocalization of LC3/LDs per cell was counted from 50 cells of three independent experiments. d–g Representative transmission electron micrograph. Blue arrows indicate LDs. Red arrows indicated autolysosome. The number of lipophagy per cell in d and f was counted from 20 cells of three independent experiments. h, i Representative fluorescence images of HeLa cells transfected with indicated siRNAs and treated with 200 μM OA for 6 h. Number of LDs per cell was counted from 50 cells of three independent experiments. j, k Representative fluorescence images of HeLa cells expressing RFP-GFP-Plin2 transfected with indicated siRNAs and treated with 200 μM OA for 12 h. Number of RFP + GFP- dots per cell was counted from 50 cells of three independent experiments. l, m Representative fluorescence images of Stx18 knockout HeLa cells transfected with indicated plasmids and treated with 200 μM OA for 6 h. Number of LDs per cell was counted from 50 cells in three independent experiments. n The concentration of triglyceride in cells was analyzed according to manufacturer’s instructions. o, p Representative fluorescence images of Atg14 knockout HeLa cells expressing indicated proteins transfected with STX18 siRNA and treated with 200 μM OA for 6 h. Number of LDs per cell was counted from 50 cells in three independent experiments. Data information: LDs were labeled with BODIPY-493/503, the nuclei were stained with DAPI, and the scar bar represents 10 μm for all fluorescence images. Error bars, mean ± SD of three independent experiments. Two-tailed Unpaired Student’s t test. Source data are provided as a Source Data file.