Role of NADPH oxidase DUOX2 in cytoskeletal dynamics and host defence

Dual Oxidase2 (DUOX2) is an important source of H2O2 in epithelial cells of the gastrointestinal and respiratory tracts. The loss of DUOX2 is associated with the pathogenesis of multiple disease states, but the exact role of DUOX2 at the mucosal surface is not fully understood. This project addresses two main topics of DUOX2 function, first in cell migration and wound healing, and then in infection resistance.
Reactive oxygen species (ROS) generation by NADPH oxidases (NOXs) has been linked to the regulation of the actin cytoskeleton including lamellipodia and focal adhesion formation, both essential for cell migration and wound healing. Cell taxis requires dynamic rearrangement of the actin cytoskeleton. ROS facilitates actin remodelling by regulating the rate of actin polymerization, incorporation of actin monomers into filaments and oxidative modification of proteins required for actin reorganisation. H2O2 has been shown to induce cortactin phosphorylation, thereby facilitating actin branching and promoting lamellipodia formation. While the importance of NOXs to actin dynamics and directed cell migration is recognised, the identity and spatiotemporal localisation of NOX isoforms to sites of actin remodelling in different cell types has remained elusive. Here we identify DUOX2 as a crucial H2O2 source within epithelial cells, promoting cortactin phosphorylation, actin structure turnover, and cell migration. We observed DUOX2 localising to lamellipodia and open-ended cell to cell membrane channels termed tunnelling nanotubes. Abolishing DUOX2 activity significantly altered single cell migration and sheet migration during wound healing. The effect of DUOX2 on wound healing carries implications for multiple gastroenteric and respiratory conditions.
DUOX2 derived H2O2 can diffuse across bacterial membranes and alter intrabacterial signalling, thereby attenuating virulence. DUOX enzymes are involved in infection control by reducing Helicobacter colonization in mice, and by discriminating between symbiotic and pathogenic microbes in Drosophila. The response of DUOX2 to pathogens is regulated at several levels including the expression pathway, intracellular localization and the activation pathway. Activated DUOX2 releases H2O2 into the intestinal lumen. Work from the Knaus laboratory placed DUOX2 at the Campylobacter invasion site in colon biopsies and revealed that DUOX2 activity limits bacterial invasion. Here I investigated the role of DUOX2 to common human and mouse intestinal pathogens. Using a combination of localization studies with in vitro and in vivo infections models, I show that DUOX2 provides a protective role during bacterial infection, where it localizes to the bacterial attachment site and around internalized bacteria and generates H2O2 as an immune response.