Vacuolin-1

Vacuolin-1 is a potent and cell-permeable lysosomal exocytosis inhibitor. Vacuolin-1 blocks the Ca²⁺-dependent exocytosis of lysosomes and prevents the release of lysosomal content without affecting the process of resealing. vacuolin‐1 is a potent and selective PIKfyve inhibitor and inhibits late‐stage autophagy by impairing lysosomal maturation. Vacuolin-1 can induce vacuole formation and increase the percentage of enucleated cells^[1][2][4].
In Vitro: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^[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^[1].
Vacuolin-1 (5 or 10 μM; 2 hours) blocks the Ca²⁺-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%)^[1].