Mitochondrial complex III-derived ROS in astrocytic signaling and Alzheimer's disease-related pathogenesis

PROJECT SUMMARY/ABSTRACT
Mitochondrial reactive oxygen species (ROS) are strongly implicated in the pathogenesis of diverse aging-
associated neurological disorders, including Alzheimer's disease (AD) and frontotemporal dementia.
Mitochondria produce ROS during oxidative metabolism and increased production of mitochondrial ROS are
causally linked to various processes in AD, including aging, amyloid precursor protein/amyloid-β (APP/Aβ)
pathology, tauopathy, and neuroinflammation. Recent work suggests that ROS produced by different
mitochondrial sites have distinct roles in cell signaling and disease. However, previous tools to suppress
mitochondrial ROS were not site-selective, disrupted respiration, or inhibited ROS only after release rather than
blocking production. Thus, the roles of mitochondrial ROS in AD pathogenesis require investigation.
Mitochondrial complex III has a large capacity for ROS production and generates ROS toward the cytosol,
poising it to regulate intracellular signaling and disease mechanisms. To investigate the effects of complex III-
derived ROS, our lab has identified and characterized small molecules that suppress complex III ROS production
(S3QELs, “sequels”), but do not block ROS production by other mitochondrial sites or affect other mitochondrial
processes. In our preliminary studies using S3QELs, we found that AD-associated neuroimmune factors
enhance astrocytic complex III ROS and that complex III ROS promote JAK-STAT3 signaling and gene
expression changes linked to disease. In astrocytic-neuronal cultures, S3QELs prevented neuronal dysfunction
linked to tauopathy, but did not affect neurons cultured in isolation. In addition, S3QELs reduced neuroimmune
and glial alterations in mice expressing mutant human tau. These data implicate complex III ROS in astrocytic
signaling and AD-related cascades. I propose to test my central hypotheses that astrocytic complex III ROS are
increased by specific disease-related stimuli and modulate astrocytic functions and dementia-linked pathogenic
processes through oxidation of distinct cysteine targets, including those related to STAT3. In Aim 1, I will use a
genetically-encoded ratiometric H2O2 sensor targeted to specific subcellular compartments in primary mouse
and human iPSC-derived astrocytes to define the exact patterns and upstream triggers of astrocytic complex III
ROS. I will also use genetic and pharmacological tools to determine the roles of complex III ROS in astrocytic
signaling, gene expression, and astrocytic-neuronal interactions. In Aim 2, I will use innovative redox proteomics
methods to broadly profile complex III ROS-mediated cysteine oxidation and use targeted and cell-specific
genetic manipulations to assess how oxidation of specific cysteine sites alters astrocytic signaling and
pathological cascades linked to dementia. The proposed study is likely to elucidate novel oxidative mechanisms
that regulate glial signaling and disease cascades and could lead to the development of targeted and effective
therapies for aging-related dementias.

Grant Number: 5F31AG084165-03
NIH Institute/Center: NIH
Principal Investigator: Daniel Barnett