Differences in cell death in methionine versus cysteine depletion

Abstract

Restriction of the sulfur amino acids methionine and cysteine has recently been proposed as potential adjuvant therapy in cancer. While cysteine depletion has been associated with ferroptotic cell death, methionine depletion has not. We hypothesized that comparing the response of melanoma cell lines to depletion of the amino acids methionine and cysteine would give us insight into the critical role in cancer of these two closely related amino acids. We analyzed the response to three conditions: methionine depletion, methionine replacement with homocysteine, and cysteine depletion. In cancer cells, the transcription factor ATF4 was induced by all three tested conditions. The replacement of methionine with homocysteine produced a strong ferroptotic gene signature. We also detected an activation of the NRF2 antioxidant pathway by both methionine and cysteine depletion. Total glutathione levels were decreased by 42% in melanoma cells grown without methionine, and by 95% in cells grown without cysteine. Lipid peroxidation was increased in cells grown without cysteine, but not in cells grown without methionine. Despite the large degree of overlap in gene expression between methionine and cysteine depletion, methionine depletion and replacement of methionine with homocysteine was associated with apoptosis while cysteine depletion was associated with ferroptosis. Glutamine depletion produced comparable gene expression patterns and was associated with a 28% decrease in glutathione. Apoptosis was detected in these cells. In this experiment, a strong ATF4‐driven ferroptotic gene signature was insufficient to induce ferroptosis without a concomitant profound decrease in glutathione levels.

Ferroptosis turns 10: Emerging mechanisms, physiological functions, and therapeutic applications

“…An siRNA screen for suppressors of ferroptosis in 2016 revealed that the top hit was the knockdown of CARS, the cysteinyl-tRNA synthetase, which suppressed erastin-induced ferroptosis through activating the transsulfuration pathway (Hayano et al, 2016). The transsulfuration pathway metabolite homocysteine was reported to enhance ferroptosis rather than drive resistance to ferroptosis when supplemented in the culture medium (Wallis et al, 2021).…”

A Multi-Omics Approach to Evaluate the Toxicity Mechanisms Associated with Silver Nanoparticles Exposure

“…Cysteine is one of the most important amino acids involved in the maintenance of the redox balance, since it takes part in the synthesis of glutathione (GSH) [ 27 ]. After AgNPs exposure, cysteine levels were found depleted (RM = 0.33); this has been linked to impaired cellular growth and cellular death due to the proliferation of oxidative stress and the limitation of iron-sulfur clusters, which are necessary for the electron transport chain (ETC) operation [ 28 , 29 ]. The low levels of cysteine might be explained by the downregulation of the CBS transcript (FC = 0.37) which is a key enzyme involved in the transsufuration pathway that, alongside CTH (FC = 0.70), also found to be downregulated, leads to the formation of cysteine.…”

Identification of potential ferroptosis hub genes in acute-on-chronic liver failure based on bioinformatics analysis and experimental verification

“…The biosynthesis of amino acids pathway is crucial in the ferroptosis mechanism [21][22][23][24][25].GSH is synthesized from three key amino acids, cysteine, glutamate, and glycine [26,27]. Both glycine and cysteine can be produced through the metabolic axis from glucose to serine.…”