Figure 6. HSP70 is released by caspase-dependent lysosomal exocytosis from LAMP3-overexpressing epithelial cells.

(A–H) HSG cells were transfected with empty and/or LAMP3 expression plasmids and then treated with vacuolin-1 (at the indicated concentration), ZVAD (20 μM), ZDEVD (10 μM), or YVAD (50 μM). Lysosomal exocytosis was monitored by quantifying LAMP1 expression on the cell surface, and the intracellular Ca²⁺ concentration was determined by Fluo-4 fluorescence by flow cytometry 48 hours after transfection. (I) The HSP70 concentration was evaluated in culture supernatant collected from HSG cells 72 hours after transfection with or without ZVAD (20 μM) or vacuolin-1 (10 μM). Values shown are the mean ± SEM from 3 (I) or 4 (A–H) independent experiments. **P < 0.01, by Student’s t test with multiple testing correction using Tukey’s method (B) or Dunnett’s method (D, F, H, and I). Max, maximum.