3-Iodobenzaldehyde[4-(diphenylamino)-6-(4-morpholinyl)-1,3,5-triazin-2-yl]hydrazone

Vacuolin-1 (1 μM; Pretreatment 1 hour) blocks ionomycin-induced exocytosis of lysosomes but not of enlargeosomes. It results in vacuolation of lysosomes (A) and complete inhibition of the surface expression of Lamp-1. Vacuolin-1 (1 μM; 20-180 min) disrupts the segregation of inner and limiting membranes characteristic of endosomes and lysosomes. Ultrastructural analysis also shows that vacuolin-1 favours fusion of inner and limiting membranes. Vacuolin-1 (5 or 10 μM; 2 hours) blocks the Ca ²⁺ -dependent release of β-hexosaminidase from lysosomes. In HeLa cells, ionomycin results in the expected release of 18-20% of lysosomal β-hexosaminidase. But when cells pretreated with vacuolin-1, releases no more β-hexosaminidase compared with cells that are not exposed to ionomycin (4%).