CHAC1 degrades glutathione, sensitizing cells to oxidative injury (663.10)

Abstract

CHAC1 is a pro‐apoptotic member of the endoplasmic reticulum stress pathway. The yeast homologue (YER163c) is the first known cytosolic protein to actively degrade glutathione (GSH), the most abundant antioxidant in the cell. However, the enzymatic activity of CHAC1 has not been fully characterized in mammalian cells. Herein, we investigate the effects of modulating CHAC1 in vitro on levels of cellular GSH and components of the GSH metabolic pathway in mammalian cells. Additionally, we define a role for CHAC1 in sensitizing cells to oxidative damage following heme treatment. Overexpression of CHAC1 in human and mouse cells leads to a large decrease in total GSH, comparable to treatment with 250uM buthionine sulphoximine, a chemical inhibitor of GSH synthesis. We probed the effects of co‐administration of excess heme, an inducer of intracellular oxidative stress. CHAC1 overexpression increased sensitivity to heme‐mediated toxicity and decreased total GSH. Supplementation with N‐acetyl cysteine, a GSH precursor, alleviated this sensitivity. CHAC1 overexpression and knockdown leads to modulation of the mRNA for the GSH anabolic enzymes as measured by qPCR. Collectively, this evidence suggests that CHAC1 sensitizes cells to oxidative stress due to degradation of GSH and potential feedback in the GSH anabolic pathway. Grant Funding Source: RRC supported by Louisiana Board of Regents Fellowship #LESQSF; INM supported by NIH grant #HL094709

The Role of ATP-Binding Cassette Proteins in Stem Cell Pluripotency

“…Importantly, ABCC1 can export both GSH and various oxidized glutathione derivatives (e.g., glutathione disulfide (GSSG)), although with distinct substrate affinity [103][104][105]. Therefore, in addition to cellular enzymes that can degrade GSH (e.g., CHAC1 [106,107]) or regenerate GSH from GSSG (e.g., GSH reductase [108]), ABCC1 likely plays an integral role in maintaining the redox equilibrium in PSCs. It has been shown that oxidative stress downregulates key PSC-specific transcription factors OCT4 and SOX2, and compromises AKT signaling [97].…”