Tartrate-resistant acid phosphatase facilitates hydroxyl radical formationand colocalizes with phagocytosed Staphylococcus aureus in alveolar macrophages

Tartrate-resistant acid phosphatase (TRAP) is an enzyme expressed specifica lly in osteoclasts and activated macrophages, two phagocytosing cell types originating from the same hematopoietic stem cells. TRAP contains a binucle ar iron centre which has been shown to generate reactive oxygen species (RO S). In this study murine macrophage like cell line RAW-264 overexpressing T RAP was shown to produce elevated levels of hydroxyl radicals compared to p arental cells. TRAP transfected cells also had reduced growth rate indicati ng harmful effects of excessive intracellular ROS levels. Using TRAP specif ic antibody TRAP protein was shown in alveolar macrophages partially coloca lize with late endosomal/lysosomal markers Rab7, Lamp 1 and MHC II molecule s that bind antigenic peptides. TRAP also colocalized into compartments whe re Staphylococcus aureus were phagocytosed. These results suggest that TRAP may have an important biological function in the defence mechanism of macr ophages by generating intracellular ROS which would be targeted to destroy phagocytosed foreign material. (C) 2001 Academic Press.