Acidocalcisome localization of membrane transporters and enzymes in Trypanosoma brucei

Abstract

ABSTRACT Acidocalcisomes of Trypanosoma brucei are membrane-bounded organelles characterized by their acidity and high content of polyphosphate and cations, like calcium and magnesium. They have important roles in cation and phosphorus storage, osmoregulation, autophagy initiation, calcium signaling, and virulence. Acidocalcisomes of T. brucei possess several membrane transporters, pumps, and channels, some of which were identified by proteomic and immunofluorescence analyses and validated as acidocalcisome proteins by their colocalization with the acidocalcisome marker vacuolar proton pyrophosphatase (VP1). Here, we report that a set of membrane transporters and enzymes, which were proposed to be present in acidocalcisomes by the morphological appearance of tagged proteins, colocalize with VP1, validating their character as acidocalcisome proteins.IMPORTANCEAcidocalcisomes are acidic organelles rich in polyphosphate and calcium present in a variety of eukaryotes and important for osmoregulation and calcium signaling. Several proteins were postulated to localize to acidocalcisomes based on their morphological characteristics. We provide validation of the localization of ten10 acidocalcisome proteins by their co-localization with enzymatic markers. These findings reveal the roles of acidocalcisomes in the storage of toxic metals, and the presence of enzymes involved in palmitoylation and polyphosphate metabolism.

Keywords

• Trypanosoma brucei
• acidocalcisome
• metal transporters
• palmitoyl acyltransferase