Various membrane ATPases have been tested for their sensitivity to Bafilomycin A1, a macrolide antibiotic. Bafilomycin A1 is a specific and reversible inhibitor of vacuolar H+-ATPase (V-ATPase). It is used as an autophagy inhibitor at the late stage. Bafilomycin A1 blocks autophagosome-lysosome fusion and inhibits acidification and protein degradation in lysosomes of cultured cells. In addition, it induces apoptosis. Bafilomycin A1 also displays different types of membrane ATPases with the I50 of 400 nmol/mg, 4 nmol/mg and 50 nmol/mg for the vacuolar ATPases of a fungus (N. crassa), a plant (Z. mays), and an animal (bovine abrenal medulla). The I50 values refer as μmol of Bafilomycin A1 per mg of protein giving 50% inhibition of ATPase activity.
Bafilomycin A1, a macrolide antibiotic, is a specific and reversible inhibitor of V-ATPase and an autophagy inhibitor at the late stage.
Bafilomycin A1 disrupts autophagic flux by inhibiting both V-ATPase-dependent acidification and Ca-P60A/SERCA-dependent autophagosome-lysosome fusion. It at a low concentration (1 nM) effectively and specifically inhibits and kills pediatric B-cell acute lymphoblastic leukemia cells. Moreover, it also targets both early and late stages of the autophagy pathway, mitochondria and induces caspase-independent apoptosis. In addition, Bafilomycin A1 induces the binding of Beclin 1 to Bcl-2, which further inhibits autophagy and promotes apoptotic cell death. Furthermore, Bafilomycin A1 also inhibits the growth of a variety of cultured cells dose-dependently. They include golden hamster embryo and NIH-3T3 fibroblasts and PC12 and HeLa cells. The IC50 of Bafilomycin A1 for inhibition of cell growth ranges from 10 to 50 nM.
In summary, Bafilomycin A1 is a potent and selective inhibitor of V-ATPases. Thus, it can study the physiological role of this class of enzymes. Bafilomycin A1 targets both autophagy and apoptosis pathways in pediatric B-cell acute lymphoblastic leukemia.