Does Cellular Hydrogen Peroxide Diffuse or Act Locally?

Understanding of redox signaling requires data on the spatiotemporal distribution of hydrogen peroxide (H2O2) within the cell. The fluorescent reporter HyPer is a powerful instrument for H2O2 imaging. However, rapid diffusion of HyPer throughout the nucleocytoplasmic compartment does not allow visualization of H2O2 gradients on the micrometer scale. Here we dramatically improved the spatial resolution of H2O2 imaging by applying subcytoplasmic targeting of HyPer. The membrane-attached reporters identified microdomains'' of elevated H2O2 levels within the cytoplasm of the cells exposed to growth factors. We demonstrate that diffusion of H2O2 across the cytoplasm was strongly limited, providing evidence that H2O2 acts locally inside cells. Antioxid. Redox Signal. 14, 1-7.