Vacuolar H⁺‐ATPases Targets for Drug Discovery?

Arrest of endosome acidification by bafilomycin A1 mimics insulin action on GLUT4 translocation in 3T3-L1 adipocytes

“…These results demonstrate : (1) that the effect of bafilomycin A " in increasing translocation of GLUT4 to the plasma membrane reaches its maximum exceedingly rapidly ; and (2) that this effect remains remarkably constant over a relatively long time period. Given the time course of the bafilomycin A " -induced inhibition of V-ATPase and increase in endosome pH [18,21], the results presented in Figures 1-4 are consistent with the idea that the arrest of endosome\lysosome acidification perturbs the retention mechanism that sequesters GLUT4 in intracellular storage locations, and induces its externalization to the cell surface.…”

“…A typical problem with this sort of experiment is that the weak bases, in addition to their effects on the acidity of the endosome compartment, may perturb essential events along the insulin-receptor-initiated signalling chain that could result in abrogation of the final biological response. Bafilomycin A " selectively inhibits V-ATPase, but not F " F o -or E " E o -ATPases at concentrations up to 1 µM, making this macrolide antibiotic a valuable tool for studying the role of the vacuolar proton pump and intravesicular acidity in membrane trafficking events [18,22,44]. The main focus of the present study was to analyse whether an arrest of endosome\lysosome acidification, achieved through specific inhibition of a H + -ATPase by bafilomycin A " , could modulate the mechanisms that retain GLUT4 in the intracellular membrane compartment in the basal state or induce its movement to the plasma membranes upon insulin stimulation of 3T3-L1 adipocytes.…”

“…To determine whether the mechanisms that sequester GLUT4 intracellularly or induce its movement to the cell surface in response to insulin are dependent upon acidification of the endomembrane system, 3T3-L1 adipocytes were treated acutely with bafilomycin A " , a specific inhibitor of the proton-translocating vacuolar-type V-ATPases [18,22]. This proton pump is found in almost all eukaryotic cells, associated with membranes of several organelles, including clathrin-coated vesicles, the Golgi complex, lysosomes, synaptic vesicles, chromaffin granules and vacuoles of plants, fungi and yeast [19].…”

“…A typical characteristic of eukaryotic endosomes, along with other organelles (i.e. Golgi and lysosomes), is their acidification, which is maintained by a vacuolar class of proton-translocating ATPases [17][18][19]. Although the role of endosome acidification is not completely understood, it is important for several aspects of endocytic trafficking.…”

Regulation of apoA1 gene expression with acidosis: requirement for a transcriptional repressor

“…Additional experiments with bafilomycin A1-treated Caco-2 cells showed a similar reduction in apoA 1 promoter activity (Table 1). Bafilomycin A1, a potent inhibitor of the vacuolar H + /ATPase (Harada et al 1997, Keeling et al 1997, prevents endosome acidification and decreases cytosolic pH. Caco-2 cells transfected with the plasmid pA1·474.CAT and treated with bafilomycin A (5 µg/ ml) showed decreased apoA 1 promoter activity to 57·8% relative to untreated cells (Table 1).…”