PS inhibitors DAPT and DupE, not JLK2, decrease the expression of CD44 and inhibit the release of CD44ICD. (A) Rat alveolar macrophages (5 × 106 cells/35-mm dish) were cultured for the indicated times, treated or not with DAPT (10 μM), DupE (0.5 μM), or JLK2 (20 μM), then lysed and subjected to Western blot analysis. In parallel wells, 24-hour cell supernatants from macrophages were collected and analyzed for CD44 content using Western blotting. (B) Schematic diagram of the CD44 constructs generated for this study. (C) Rat alveolar macrophages were transduced with the retroviral vector MigR1 empty (control) or encoding CD44ΔE, and then treated or not with DAPT (10 μM), DupE (0.5 μM), or JLK2 (20 μM) for 24 hours. The cell lysates were subjected to Western blotting analysis using an mAb directed against myc. The cleavage of CD44 ΔE into CD44ICD was inhibited by DAPT and DupE, but not by JLK2.
