(c) HEK293 cells were treated as in b, in the presence of leupeptin and stained by anti-AMBRA1 (red) and anti-ULK1 (green) antibodies. The merge of the two signals and DAPI (blue) for nuclear staining is shown in the right panels. Scale bar, 6 μm. The outlined areas are shown at a higher magnification in the lower panels. White arrows point to the co-localization puncta. Measurements by Metamorph indicate a co-localization ratio of 46% between ULK1 and AMBRA1 on autophagy induction. 