Figure 6: VAMP2 regulates autophagic precursor maturation.

(a) Size of endogenous ATG12 vesicles in HeLa cells stably expressing either wild-type or mutant VAMP2. Confocal pictures are presented with magnified areas showing ATG12 vesicles. Data are representative of three independent experiments and shown as mean ±s.d. (n≥100 vesicles; *P<0.05; two tail t-test). Scale bars, 5 μm. (b) Co-localization between ATG12 and LC3 in HeLa cells stably expressing either wild-type clone 11 or mutant clone 12 VAMP2. Confocal pictures are presented with magnified areas showing ATG12-LC3 co-localization. The Pearson’s coefficient between ATG12 and LC3 is shown. Data are representative of three independent experiments and shown as mean ±s.d. (n≥100 vesicles; *P<0.05; two-tailed t-test). Scale bars, 5 μm. (c) Size and number of endogenous ATG12 vesicles in VAMP2-knockdown HeLa cells in starvation condition. Confocal pictures are shown with arrows indicating ATG12 vesicles. Data are representative of three independent experiments and shown as mean ±s.d. for the size of ATG12 vesicle. (n≥100 vesicles; *P<0.05; based two-tailed t-test). Scale bars, 5 μm. (d) Live-cell imaging of ATG16L1-GFP in VAMP2-knockdown HeLa cells. Confocal pictures from various time points of a 5-min movie are shown in inverted greyscale. Arrows indicate ATG16L1 vesicles. The number of fusion events per 5 min is shown. Data are representative of five movies and shown as mean ±s.d. (*P<0.05; two-tailed t-test). Scale bars, 5 μm. (e) In vitro fusion assay of post-nuclear supernatants from control and VAMP2 knockdown HeLa cells expressing either GFP-ATG16L1 or mStrawberry-ATG16L1. Confocal pictures are shown where ATG16L1-mStrawberry signal is shown in purple to enable better visualization. Fused vesicles appear in white. The ATP-negative condition, which prevents SNARE-dependent fusion, is also shown as a control of reaction. Magnified areas are shown to allow visualization of the vesicles. The percentage of fused vesicles (white) is represented. Data are representative of two independent experiments and shown as mean ±s.d. (n≥100 vesicles). Scale bars, 5 μm. (*P<0.05; two-tailed t-test). n=numbers of vesicles scored per field.