Pyrophosphate Stimulates the Phosphate-Sodium Symporter of Trypanosoma brucei Acidocalcisomes and Saccharomyces cerevisiae Vacuoles

Abstract

Acidocalcisomes, first described in trypanosomes and known to be present in a variety of cells, have similarities with S. cerevisiae vacuoles in their structure and composition. Both organelles share a Na + /P i symporter involved in P i release to the cytosol, where it is needed for biosynthetic reactions. Here we show that PP i , at physiological cytosolic concentrations, stimulates the symporter expressed in either Xenopus oocytes or yeast vacuoles via its SPX domain, revealing a signaling role of this molecule.