Study on the Role of Cereblon (CRBN) as a Putative Antioxidant Response Regulator via Regulating de novo Synthesis of Glutathione Precursors in Lung Cancer

Abstract

Deregulation of redox homeostasis, increase of antioxidant capacity and reprogramming of cellular metabolism are the hallmarks of cancer. It has been recently proposed that altered glucose-derived serine synthetic flux in cancer cells replenishes the pool of glycine and cysteine which are the precursors of the fundamental antioxidant, glutathione. In this study, I used public multi-omics data and found that serine synthetic flux is increased in lung cancer. Cereblon (CRBN), a substrate receptor of E3 ubiquitin ligase complex, is downregulated in lung cancer and intriguingly depletion of CRBN in lung cancer cell lines were related to high intracellular glutathione level. I determined that loss of CRISPR/Cas9 mediated CRBN confers invulnerability to oxidative stress and increases synthetic flux of serine, glycine and cysteine by using survival assay, fluorescence based reactive species detection and GC/MS stable isotope tracing analysis. I also performed computational simulation of protein-protein interaction and proposed the novel putative CRBN binding proteins, serine hydroxymethyltransferase (SHMT) and cystathionine-beta-synthase (CBS) which were the enzymes that can produce precursors of glutathione. I identified CBS can interact with CRBN and the expression and activity of CBS were significantly increased in CRISPR/Cas9 and PROTAC mediated CRBN-deficient cells. Hence, downregulation of CRBN in lung cancer can contribute to alteration of glutathione biosynthesis and potentially it can induce cellular antioxidant defense during the cancer progression and detoxification against the cancer therapy.