ATP-induced beta-glucuronidase release from undifferentiated HL-60 cells is dependent on Ca2+ ions.
Extracellular ATP (0.1-100 microM) evoked a biphasic increase in cytosolic free Ca2+ ion concentration ([Ca2+]i) in fura-2 loaded undifferentiated HL-60 cells and activated the release of the lysosomal enzyme beta-glucuronidase. The EC50 for the elevation of [Ca2+]i was about 0.2 microM. However, the EC50 for the activation of beta-glucuronidase release was two orders of magnitude higher (about 20 microM). These data imply that the ATP-induced elevation in [Ca2+]i is not sufficient to provoke beta-glucuronidase release. The role of [Ca2+]i in ATP-induced beta-glucuronidase release was further investigated using Ca(2+)-free solutions and by loading HL-60 cells with the non-fluorescent Ca(2+)-chelator BAPTA-AM. Ca2+ ions from both intracellular and extracellular sources were necessary for the activation of beta-glucuronidase secretion by extracellular ATP. However, the internal store is the major source of Ca2+ ions for the response.
Packham
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DE
Department of Biochemistry, University of Sydney, NSW, Australia.
Jiang
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L
Conigrave
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AD
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D002118:Calcium / Q000502:physiology*; D002454:Cell Differentiation; D002614:Chelating Agents / Q000494:pharmacology; D003594:Cytoplasmic Granules / Q000201:enzymology / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000502:physiology; D005966:Glucuronidase / Q000378:metabolism*; D018922:HL-60 Cells / Q000187:drug effects*; D006801:Humans; D008247:Lysosomes / Q000201:enzymology / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*
D002614:Chelating Agents; D009363:Neoplasm Proteins; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; D000255:Adenosine Triphosphate; D005966:Glucuronidase; D019204:GTP-Binding Proteins; D002118:Calcium