LAUSR

High‐level reactive oxygen species (ROS) production in neutrophils is tightly regulated, as it can damage host cells. Neutrophils also undergo low‐level ROS production when stimulated by cytokines or chemoattractants, but its biologic significance remains largely unknown. Voltage‐gated proton channels (Hv1/VSOP) activity reportedly supports ROS production in neutrophils; however, we show here that Hv1/VSOP balances ROS production to suppress neutrophil directional migration in the presence of low concentrations of N‐formyl‐Met‐Leu‐Phe (fMLF). Neutrophils derived from Hvcn1 gene knockout mice produced more ROS than neutrophils from wild‐type mice in the stimulation with fMLF at concentration of 1 µM and nonstimulus condition. They also exhibited stronger chemotactic responses to low concentrations of fMLF than did wild‐type neutrophils. Receptor sensitivity to fMLF and evoked Ca2+ responses did not differ between Hv1/VSOP‐deficient and wild‐type neutrophils. Activation of ERK, but not p38, was enhanced and prolonged during the increased ROS production seen after fMLF stimulation in Hv1/VSOP‐deficient neutrophils. Inhibiting ROS production suppressed the enhanced ERK activation in Hv1/VSOP‐deficient neutrophils and their directional migration. These results indicate that Hv1/VSOP balances ROS production to reduce ERK signaling and suppress excessive neutrophil migration in response to fMLF. Our findings thus reveal a novel role for ROS in the directional migration of neutrophils.