title: Polyphosphate is a novel pro-inflammatory regulator of mast cells and is located in acidocalcisomes.
abstract: Polyphosphate (polyP) is a pro-inflammatory agent and a potent modulator of the human blood-clotting system. The presence of polyP of 60 phosphate units was identified in rat basophilic leukemia (RBL-2H3) mast cells using specific enzymatic assays, urea-polyacrylamide gel electrophoresis of cell extracts, and staining of cells with 4,6-diamidino-2-phenylindole (DAPI), and the polyP-binding domain of Escherichia coli exopolyphosphatase. PolyP co-localizes with serotonin- but not with histamine-containing granules. PolyP levels greatly decreased in mast cells stimulated to degranulate by IgE. Mast cell granules were isolated and found to be acidic and decrease their polyP content upon alkalinization. In agreement with these results, when RBL-2H3 mast cells were loaded with the fluorescent calcium indicator fura-2 acetoxymethyl ester to measure their intracellular Ca(2+) concentration ([Ca(2+)](i)), they were shown to possess a significant amount of Ca(2+) stored in an acidic compartment different from lysosomes. PolyP derived from RBL-2H3 mast cells stimulated bradykinin formation, and it was also detected in human basophils. All of these characteristics of mast cell granules, together with their known elemental composition, and high density, are similar to those of acidocalcisomes. The results suggest that mast cells polyP could be an important mediator of their pro-inflammatory and pro-coagulant activities.
authors: Unidad de Investigación, Hospital Universitario Puerta del Mar, Facultad de Medicina, Universidad de Cádiz, 11009 Cádiz, Spain.
authors: David
authors: D
authors: Moreno-Sanchez
authors: Laura
authors: L
authors: Hernandez-Ruiz
authors: Felix A
authors: FA
authors: Ruiz
authors: Roberto
authors: R
authors: Docampo
mesh_terms: D000818:Animals; D001491:Basophils / Q000378:metabolism; D001920:Bradykinin / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D005260:Female; D006801:Humans; D018836:Inflammation Mediators / Q000378:metabolism*; D008247:Lysosomes / Q000378:metabolism; D008297:Male; D008407:Mast Cells / Q000378:metabolism*; D011122:Polyphosphates / Q000378:metabolism*; D051381:Rats; D012701:Serotonin / Q000378:metabolism
chemical_list: D018836:Inflammation Mediators; D011122:Polyphosphates; D012701:Serotonin; D001920:Bradykinin; D002118:Calcium