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NOX4 activity is determined by mRNA levels and reveals a unique pattern of ROS generation

  • Serrander, Lena Foundation for Medical Research, University of Geneva, 64 av de la Roseraie, 1205, Geneva, Switzerland
  • Cartier, Laetitia Department of Immunology and Pathology, University of Geneva, Rue Michel Servet 1, 1206 Geneva, Switzerland
  • Bedard, Karen Department of Immunology and Pathology, University of Geneva, Rue Michel Servet 1, 1206 Geneva, Switzerland
  • Banfi, Botond Department of Anatomy and Cell Biology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, U.S.A.
  • Lardy, Bernard Department of Enzymology, GREPI, Hôpital Albert Michallon, BP 217-CHU Grenoble Cedex 9, France
  • Plastre, Olivier Department of Immunology and Pathology, University of Geneva, Rue Michel Servet 1, 1206 Geneva, Switzerland
  • Sienkiewicz, Andrzej Institute of Physics of Complex Matter, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
  • Fórró, Lászlo Institute of Physics of Complex Matter, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
  • Schlegel, Werner Foundation for Medical Research, University of Geneva, 64 av de la Roseraie, 1205, Geneva, Switzerland
  • Krause, Karl-Heinz Department of Immunology and Pathology, University of Geneva, Rue Michel Servet 1, 1206 Geneva, Switzerland
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  • 2007-7-26
Published in:
  • Biochemical Journal. - Portland Press Ltd.. - 2007, vol. 406, no. 1, p. 105-114
English NOX4 is an enigmatic member of the NOX (NADPH oxidase) family of ROS (reactive oxygen species)-generating NADPH oxidases. NOX4 has a wide tissue distribution, but the physiological function and activation mechanisms are largely unknown, and its pharmacology is poorly understood. We have generated cell lines expressing NOX4 upon tetracycline induction. Tetracycline induced a rapid increase in NOX4 mRNA (1 h) followed closely (2 h) by a release of ROS. Upon tetracycline withdrawal, NOX4 mRNA levels and ROS release decreased rapidly (<24 h). In membrane preparations, NOX4 activity was selective for NADPH over NADH and did not require the addition of cytosol. The pharmacological profile of NOX4 was distinct from other NOX isoforms: DPI (diphenyleneiodonium chloride) and thioridazine inhibited the enzyme efficiently, whereas apocynin and gliotoxin did not (IC50>100 μM). The pattern of NOX4-dependent ROS generation was unique: (i) ROS release upon NOX4 induction was spontaneous without need for a stimulus, and (ii) the type of ROS released from NOX4-expressing cells was H2O2, whereas superoxide (O2−) was almost undetectable. Probes that allow detection of intracellular O2− generation yielded differential results: DHE (dihydroethidium) fluorescence and ACP (1-acetoxy-3-carboxy-2,2,5,5-tetramethylpyrrolidine) ESR measurements did not detect any NOX4 signal, whereas a robust signal was observed with NBT. Thus NOX4 probably generates O2− within an intracellular compartment that is accessible to NBT (Nitro Blue Tetrazolium), but not to DHE or ACP. In conclusion, NOX4 has a distinct pharmacology and pattern of ROS generation. The close correlation between NOX4 mRNA and ROS generation might hint towards a function as an inducible NOX isoform.
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  • English
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green
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https://folia.unifr.ch/global/documents/53054
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