Human Platelet Dense Granules Contain Polyphosphate and Are Similar to Acidocalcisomes of Bacteria and Unicellular Eukaryotes
| Autor: | Eric Oldfield, Felix A. Ruiz, Roberto Docampo, Christopher R. Lea |
|---|---|
| Rok vydání: | 2004 |
| Předmět: |
Blood Platelets
Serotonin Magnetic Resonance Spectroscopy Time Factors Nigericin Fura-2 Volutin granules Biology H(+)-K(+)-Exchanging ATPase Biochemistry Pyrophosphate Ammonium Chloride chemistry.chemical_compound Polyphosphates Centrifugation Density Gradient Humans Urea Pyrophosphatases Molecular Biology Fluorescent Dyes Adenosine Triphosphatases Perchlorates Bacteria X-Rays Polyphosphate Thrombin Bafilomycin Cell Biology Diphosphates Acidocalcisome Microscopy Electron Microscopy Fluorescence chemistry Potassium Calcium Electrophoresis Polyacrylamide Gel Macrolides Protons |
| Zdroj: | Journal of Biological Chemistry. 279:44250-44257 |
| ISSN: | 0021-9258 |
| DOI: | 10.1074/jbc.m406261200 |
| Popis: | Inorganic polyphosphate (polyP) has been identified and measured in human platelets. Millimolar levels (in terms of Pi residues) of short chain polyP were found. The presence of polyP of approximately 70-75 phosphate units was identified by 31P NMR and by urea-polyacrylamide gel electrophoresis of platelet extracts. An analysis of human platelet dense granules, purified using metrizamide gradient centrifugation, indicated that polyP was preferentially located in these organelles. This was confirmed by visualization of polyP in the dense granules using 4',6-diamidino-2-phenylindole and by its release together with pyrophosphate and serotonin upon thrombin stimulation of intact platelets. Dense granules were also shown to contain large amounts of calcium and potassium and both bafilomycin A1-sensitive ATPase and pyrophosphatase activities. In agreement with these results, when human platelets were loaded with the fluorescent calcium indicator Fura-2 acetoxymethyl ester to measure their intracellular Ca2+ concentration ([Ca2+]i), they were shown to possess a significant amount of Ca2+ stored in an acidic compartment. This was indicated by the following: 1) the increase in [Ca2+]i induced by nigericin, monensin, or the weak base, NH4Cl, in the nominal absence of extracellular Ca2 and 2) the effect of ionomycin, which could not take Ca2+ out of acidic organelles and was more effective after alkalinization of this compartment by the previous addition of nigericin, monensin, or NH4Cl. All of these characteristics of the platelet dense granules, together with their known acidity and high density (both by weight and by electron microscopy), are similar to those of acidocalcisomes (volutin granules, polyP bodies) of bacteria and unicellular eukaryotes. The results suggest that acidocalcisomes have been conserved during evolution from bacteria to humans. |
| Databáze: | OpenAIRE |
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