UC Berkeley

Hydrogen peroxide (H2O2) has long been considered a toxic byproduct of cellular metabolism and a causative agent of disease, particularly of neurodegenerative diseases such as Alzheimer's and Parkinson's. While high concentrations of this reactive molecule are undoubtedly deleterious, a more nuanced view of its biological activity has developed over the last two decades as evidence of a beneficial signaling role and deliberate H2O2 production by mammalian tissues has emerged. Indeed, there is even evidence that H2O2 plays a signaling role in the brain despite its potential to wreak havoc in this sensitive organ. This dissertation addresses this surprising result and demonstrates well-regulated physiological production and transport of H2O2 by brain neurons and its reactivity with potential cellular signaling targets. Specifically, fluorescent probes for H2O2 are used in live cultured neurons to demonstrate that this molecule is produced by the membrane-bound NADPH oxidase 2 (Nox2) enzyme in cortical neurons in response to activation of N-methyl-D-apartic acid receptors (NMDARs). Furthermore, intercellular transmission of H2O2 is demonstrated in a Nox2 knockout-rescue system. A signaling role for this endogenous H2O2 is proposed, inasmuch as the Nox2-sensitive oxidation of protein cysteinyl residues contingent on NMDAR stimulation is detected, and the affected proteins are identified. Finally, the H2O2-mediated modulation of neuronal actin dynamics is demonstrated to be Nox2-dependent as well, suggesting a role for redox signaling in neuronal plasticity.