Figure 2.

Identification of PD as a lysosome-targeting compound

(A) Schematic diagram depicting the strategy for the identification of amphiphilic drugs by virtual screening with a natural product library (2,212 compounds). (B) Pharmacophore mapping of fit compounds in the test set with 14 known amphiphilic drugs. Pharmacophore features: Green, HB acceptor; cyan, hydrophobic; orange, Ring aromatic; red, POS ionizable. (C) Cell viability measurement of HepG2 cells treated with the top 20 compounds at 10 μM for 24 h by WST-1 assay. Polyphyllin D (PD) with the highest inhibitory ratio on cell viability was marked in red. (D) Colocalization of PD with lysosomes. PD-Cy3 (1 μM) loaded HepG2 cells were stained with LysoTracker (green) or Mito-Tracker (green) or transfected with TMEM192-EGFP and LAMP1-EGFP, and subjected to confocal imaging. (E) The intensity profile of PD-Cy3 and TMEM192-EGFP along the white line was plotted in (D), with the colocalization sites marked with black arrows.