Decoding Hydrogen Peroxide Signaling at Cellular Membranes

PROJECT SUMMARY Eukaryotic cells employ different mechanisms to sense and respond to their environment and maintain tissue homeostasis. Cells have evolved strategies to co-opt stable reactive oxygen species such as hydrogen peroxide (H2O2) as non-transcriptional signaling molecules in order to rapidly respond and adapt to environmental changes. Numerous examples of the influence of H2O2 signaling have emerged, ranging from abiotic stress in plants to immune responses in humans. H2O2 signaling and subsequent regulation of target proteins is therefore an important but still underappreciated biological control mechanism. H2O2-regulated cell signaling is largely dependent on the presence of redox-sensitive thiol switches in protein cysteine residues, where the reactivity of these switches is highly dependent on the local H2O2 concentration. Our previous studies in epithelial cells have shown that key determinants of cellular H2O2 concentrations include generation of H2O2, by cell membrane surface enzymes such as the NADPH oxidases and permeability across cellular membranes which can be facilitated by Aquaporin (AQP) channels. A number of cellular processes such as innate immune signaling, vesicular trafficking and migration have been shown to be regulated by H2O2, but how cellular membranes allow for specific and privileged signaling by H2O2 remains incompletely understood. We therefore propose studies that aim to establish general rules and emergent concepts related to H2O2 signals at membranes. Our studies will encompass four major areas of inquiry that seek to address i) How does plasma membrane permeability to H2O2 influence redox signaling and regulation? ii.) How do H2O2 signals and subsequent regulation of proteins alter essential vesicular trafficking pathways in the cell? iii) How does H2O2 signaling occur at vesicular membranes? iv.) How does spatial control of cellular H2O2 regulate the directional migration of cells? To address these questions, we will apply and develop high resolution quantitative fluorescence imaging to follow the spatial and temporal dynamics of H2O2 signals at membranes, in combination with proteomic approaches to identify target modified cysteines. Further studies will investigate how oxidative modifications alter target protein structure, function and localization, constructing a mechanistic understanding of how H2O2 signals are relayed from cellular membranes. Future studies will build on this framework to uncover strategies to direct and manipulate H2O2 signals for treatment of human disease. Integrated to these studies will be the development of novel tools and approaches to study H2O2 signals at membranes that can be broadly applied for research in this field.