The Hv1 voltage‐gated proton channel regulates the pH of neutrophil but not macrophage phagosomes

Abstract

Phagosomal acidification and reactive oxygen species (ROS) production are important for an effective immune response. Macrophage phagosomes acidify rapidly due to vATPase activity, whereas neutrophil phagosomes remain near‐neutral for >;30 min due to ROS‐dependent inhibition of vATPase activity. Hv1 proton channels sustain high level ROS production at the plasma membrane by extruding protons from the cytosol. Here we tested whether the phagosomal pH of neutrophils and macrophages is regulated by Hv1 channels. Immunostaining revealed that Hv1 was recruited to phagosomes of both neutrophils and macrophages. ROS production, measured with OxyBurst‐coupled targets, was reduced in neutrophil phagosomes of Hv1 knockout mice. Ratiometric imaging of fluorescein isothiocyanate‐coupled targets showed that macrophage phagosomes acidified rapidly and independently of Hv1. In contrast, neutrophil phagosomes remained neutral 30 min after target ingestion, while 80% of Hv1 knockout phagosomes were alkaline. The remaining 20% where highly acidic and this subpopulation of acidic phagosomes was eliminated by inhibition of vATPase. These data suggest that whereas Hv1 contributes little to macrophage phagosomal pH, in neutrophils Hv1 ablation deregulates phagosome pH, leading either to alkalinization or to early recruitment of vATPase.