Ca2+‐binding‐region‐dependent cell surface localization of NADPH oxidase Nox5

Abstract

Six gene splice variants of superoxide‐generating NADPH oxidase 5 (Nox5) have been identified in humans, and they differ in the sequence of their N‐terminal cytoplasmic domains, which comprise four EF‐hand motifs. Here, we demonstrated that the Ca2+‐dependent association and dissociation between the N‐ and C‐terminal cytoplasmic domains of the Nox5β variant are affected by the alanine substitution of the conserved Ile‐113 or Leu‐115 at the connecting loop between the third and fourth EF‐hand motifs. These substitutions impair the cell surface localization of Nox5β. In addition, the Nox5ε/S variant, lacking all EF‐hand motifs, does not localize to the plasma membrane. Thus, the Ca2+‐sensitive intramolecular interaction determines the Nox5 subcellular localization, that is, whether Nox5 variants generate superoxide in the extracellular or intracellular space.