OLA1, an Obg-like ATPase, suppresses antioxidant response via nontranscriptional mechanisms

Abstract

Oxidative stress has been implicated in diverse disease states and aging. To date, induction of cellular responses to combat oxidative stress has been characterized largely at the transcriptional level, with emphasis on Nrf2-mediated activation of antioxidant response elements. In this study, we demonstrate that OLA1, a novel Obg-like ATPase, functions as a negative regulator of the cellular antioxidant response independent of transcriptional processes. Knockdown of OLA1 in human cells elicited an increased resistance to oxidizing agents including tert-butyl hydroperoxide (tBH) and diamide without affecting cell proliferation, baseline apoptosis, or sensitivity to other cytotoxic agents that target the mitochondria, cytoskeleton, or DNA. Conversely, overexpression of OLA1 increased cellular sensitivity to tBH and diamide. When challenged with oxidants, OLA1-knockdown cells had decreased production of intracellular reactive oxygen species and exhibited less depletion of reduced glutathione. Surprisingly, knockdown of OLA1 caused only minimal genomic response; no changes were found in the mRNA levels of genes encoding antioxidant enzymes, enzymes that produce antioxidants (including glutathione), or other genes known to respond to Nrf2. Moreover, when de novo protein synthesis was blocked by cycloheximide in OLA1-knockdown cells, they continued to demonstrate increased resistance to both tBH and diamide. These data demonstrate that OLA1 suppresses the antioxidant response through nontranscriptional mechanisms. The beneficial effects observed upon OLA1-knockdown suggest that this regulatory ATPase is a potential novel target for antioxidative therapy.