Impaired lysosomal activity in S1P-lyase KO cells.
A–D, Western blot analysis of cathepsin D in WT and S1PL-KO (A and B) and in siRNA transfected murine N9 cells (C and D). The ratio of active to immature (pro-/intermediate-) forms of cathepsin D is decreased in S1PL-KO (***, p < 0,001; n = 6) and upon knockdown of S1P-lyase (**, p < 0.01; n = 3). E–H, detection of lysosomally degraded Lamp-2 (E and F) and Gm2 activator protein (Gm2a) (G and H) in WT and S1PL-KO cell lysates by Western immunoblotting. Levels of Lamp-2 (F) and Gm2a (H) are increased in S1PL-KO cells, indicative for an impairment of lysosomal activity. Quantitative analysis was done by ECL imaging (E; *, p < 0.05; n = 3; and G; *, p < 0.05; n = 3). Cat. D or Cath D, cathepsin D.