Postdoctoral Scholar Gladstone Institutes San Francisco, California, United States
Abstract: Neurons depend heavily on ATP production via the mitochondrial oxidative phosphorylation (OXPHOS) pathway. Dysfunction of mitochondrial respiratory complex I (MCI), a key component of OXPHOS, has been observed in multiple neurodegenerative disorders such as Alzheimer’s disease (AD) and Parkinson’s disease (PD). A recent study showed that disruption of MCI in dopaminergic neurons in mice leads to decreased dopamine production and PD-like symptoms. However, how MCI reduction is related to the degeneration of human neurons remains poorly understood. Here, we investigated the relationship between MCI and neurodegeneration by reducing MCI subunit expression using CRISPR interference (CRISPRi) or CRISPR-Cas9 in human iPSC-derived neurons. We found decreasing MCI subunit expression in hiPSCs did not affect their differentiation into neurons or the viability and morphology of the resulting neurons under normal culture conditions. Compared with control neurons, those with reduced MCI subunit expression showed upregulation of the glutathione synthesis pathway, an essential antioxidant defense mechanism. In addition, when treated with a cell death inducer, MCI-deficient neurons exhibited higher survival rates, maintained mitochondrial membrane potential for longer, and produced lower levels of ROS than controls. Our results demonstrate that reducing MCI subunit expression enhances glutathione-mediated antioxidant defenses and reduces ROS generation, thereby ameliorating cell death. Thus, this study offers a new perspective that reducing the mitochondrial complex I subunit may lead to a promising neuroprotective strategy, in contrast to the previous view that MCI inhibition leads to neuronal death. Furthermore, it underscores the potential clinical application of this approach to slow or prevent neuronal loss in AD, PD, and other neurodegenerative disorders.
Funding Source: Masason Foundation California Institute for Regenerative Medicine (CIRM) The on-site laboratory initiative launched by Kyoto University Funding from Mr. Hiroshi Mikitani and Mr. Marc Benioff National Institutes of Health (NIH)
