Human cysteine dioxygenase type I (CDO-I; EC 1.13.11.20): 5' flanking region and intron-exon structure of the gene

Cysteine Dioxygenase 1 Mediates Erastin-Induced Ferroptosis in Human Gastric Cancer Cells

BACKGROUND

Ferroptosis is a recently discovered form of iron-dependent nonapoptotic cell death. It is characterized by loss of the activity of the lipid repair enzyme, glutathione peroxidase 4 (GPX4), and accumulation of lethal reactive lipid oxygen species. However, we still know relatively little about ferroptosis and its molecular mechanism in gastric cancer (GC) cells. Here, we demonstrate that erastin, a classic inducer of ferroptosis, induces this form of cell death in GC cells and that cysteine dioxygenase 1 (CDO1) plays an important role in this process.

METHODS

We performed quantitative real-time polymerase chain reaction, Western blotting, cell viability assay, reactive oxygen species (ROS) assay, glutathione assay, lipid peroxidation assay, RNAi and gene transfection, immunofluorescent staining, dual-luciferase reporter assay, transmission electron microscopy, and chromatin immunoprecipitation assay to study the regulation of ferroptosis in GC cells. Mouse xenograft assay was used to figure out the mechanism in vivo.

RESULTS

Silencing CDO1 inhibited erastin-induced ferroptosis in GC cells both in vitro and in vivo. Suppression of CDO1 restored cellular GSH levels, prevented ROS generation, and reduced malondialdehyde, one of the end products of lipid peroxidation. In addition, silencing COO1 maintained mitochondrial morphologic stability in erastin-treated cells. Mechanistically, c-Myb transcriptionally regulated CDO1, and inhibition of CDO1 expression upregulated GPX4 expression.

CONCLUSIONS

Our findings give a better understanding of ferroptosis and its molecular mechanism in GC cells, gaining insight into ferroptosis-mediated cancer treatment.

Sézary syndrome is a unique cutaneous T-cell lymphoma as identified by an expanded gene signature including diagnostic marker molecules CDO1 and DNM3

Sezary syndrome (SS) is a rare, aggressive CD4+ cutaneous T-cell lymphoma (CTCL); molecular traits differentiating SS from nonleukemic mycosis fungoides (MF) and from inflammatory skin diseases (ID) are not sufficiently characterized. Peripheral blood mononuclear cells (PBMC) of 10 SS patients and 10 healthy donors (HD) were screened by Affymetrix U133Plus2.0 chips for differential gene expression. Ten candidate genes were confirmed by qRT-PCR to be significantly overexpressed in CD4+ T cells of SS versus HD/ID. For easier clinical use, these genes were re-analyzed in PBMC; qRT-PCR confirmed five novel (DNM3, IGFL2, CDO1, NEDD4L, KLHDC5) and two known genes (PLS3, TNFSF11) to be significantly overexpressed in SS. Multiple logistic regression analysis revealed that CDO1 and DNM3 had the highest discriminative power in combination. Upon comparison of PBMC and skin samples of SS versus MF, CDO1 and DNM3 were found upregulated only in SS. Using anti-CDO1 antisera, differential expression of CDO1 protein was confirmed in SS CD4+ T cells. Interestingly, DNM3 and CDO1 are known to be regulated by SS-associated transcription factors TWIST1 and c-myb, respectively. Furthermore, CDO1 catalyzes taurine synthesis and taurine inhibits apoptosis and promotes chemoprotection. In summary, CDO1 and DNM3 may improve the diagnosis of SS and open novel clues to its pathogenesis.

Taurine biosynthetic enzymes and taurine transporter: molecular identification and regulations

Many biological effects of taurine rely upon its cellular concentration, which is primarily controlled by taurine biosynthetic enzymes cysteine dioxygenase (CDO) and cysteine sulfinate decarboxylase (CSD) and taurine transporter (TauT). The cloning of CDO, CSD and TauT in various species provided first-hand information on these proteins, as well as molecular tools to investigate their regulations. CDO upregulation in hepatocytes in response to high sulfur amino acids appears clearly as the most spectacular among the regulations of the biosynthetic enzymes. Downregulation of TauT activity by activation of PKC appears particularly well documented. A unique serine residue could be identified as a phosphorylation site that leads to an inactive form of TauT. The previously revealed downregulation of TauT expression by taurine and hypertonicity-induced upregulation of TauT expression were shown to result from a modified transcription rate of TauT gene, but the precise molecular mechanisms are not yet formally established. Other regulations of taurine transporter expression were more recently reported, which involve glucose, tumor suppressor protein p53, tumor necrosis factor-alpha, and nitric oxide. This review reports the experimental models and data that support these various regulations but also points out the aspects that remain poorly understood or unknown concerning their molecular basis and physiological significance.

Murine cysteine dioxygenase gene: structural organization, tissue-specific expression and promoter identification

The murine gene encoding cysteine dioxygenase (CDO; EC 1.13.11.20), a key enzyme of L-cysteine metabolism, was isolated and characterized, and the proximal promoter was identified. A bacterial artificial chromosome mouse library was screened and a single clone containing the entire CDO gene was isolated. The murine CDO gene contains five exons and spans about 15 kb. The open reading frame is encoded within all five exons. All intron/exon splice junctions and all intron sizes are conserved with the rat CDO gene and are very similar to those of the human CDO gene. The primary transcriptional initiation site is located 213 bp upstream of the initiation ATG codon. The nucleotide sequence of the 5'-promoter region is highly conserved between the mouse and rat genes and contains a TATA-box-like sequence and GC boxes. A variety of consensus cis-acting elements were also identified in the 5'-flanking region. These included HNF-3 beta, HFH-1, HFH-2, HFH-3, C/EBP, and C/EBP beta, all of which are consistent with the tissue-specific expression profiles of the gene. Gene reporter studies of the CDO 5'-region indicated the presence of an active promoter within the first 223 bp upstream of the transcriptional initiation site and the possible presence of repressor elements upstream of bp -223. Northern blot analyses indicated that the CDO gene displays tissue-specific expression, with the highest mRNA level present in liver and with detectable levels found in kidney, lung, brain and small intestine. Western blot analyses indicated that CDO protein levels parallel mRNA levels. These results are consistent with the known function of CDO in whole-body cysteine homeostasis.

Cysteine dioxygenase: regional localisation of protein and mRNA in rat brain

Cysteine dioxygenase (CDO) converts cysteine to cysteinesulphinic acid and is the rate-limiting step in sulphate production. Most studies have centred upon the hepatic form of the enzyme, but several studies have investigated brain CDO using activity assays and western blotting. The aim of this study was to investigate the expression of CDO in the rat brain using a combination of immunohistochemistry and in situ hybridisation. Affinity-purified anti-R and anti-H CDO antibodies were immunoprecipitated using rat brain homogenate to determine whether the antibodies could remove enzyme activity. Immunohistochemistry and in situ hybridisation were then used to determine the cellular and regional expression of both CDO protein and mRNA. Immunoprecipitation of rat brain homogenate removed up to 98% and 70% (anti-R and anti-H, respectively) of enzyme activity. Nonimmune sheep serum had no effect upon enzyme activity. CDO protein and mRNA was localised solely to the neurones of the brain, including the pyramidal cells of the hippocampus and the Purkinje cells of the cerebellum. Regional localisation varied, with high levels of expression in the hippocampus, the dentate gyrus, the outer cortices of the brain, and the substantia nigra. The relative expression of CDO activity and protein in these regions is most probably a result of the relative abundance of neurones in these regions. CDO expression in the brain may have several possibilities functions, the most likely being the prevention of free radical production by the autoxidation of cysteine and dopamine.

Microbial relatives of the seed storage proteins of higher plants: conservation of structure and diversification of function during evolution of the cupin superfamily

This review summarizes the recent discovery of the cupin superfamily (from the Latin term "cupa," a small barrel) of functionally diverse proteins that initially were limited to several higher plant proteins such as seed storage proteins, germin (an oxalate oxidase), germin-like proteins, and auxin-binding protein. Knowledge of the three-dimensional structure of two vicilins, seed proteins with a characteristic beta-barrel core, led to the identification of a small number of conserved residues and thence to the discovery of several microbial proteins which share these key amino acids. In particular, there is a highly conserved pattern of two histidine-containing motifs with a varied intermotif spacing. This cupin signature is found as a central component of many microbial proteins including certain types of phosphomannose isomerase, polyketide synthase, epimerase, and dioxygenase. In addition, the signature has been identified within the N-terminal effector domain in a subgroup of bacterial AraC transcription factors. As well as these single-domain cupins, this survey has identified other classes of two-domain bicupins including bacterial gentisate 1, 2-dioxygenases and 1-hydroxy-2-naphthoate dioxygenases, fungal oxalate decarboxylases, and legume sucrose-binding proteins. Cupin evolution is discussed from the perspective of the structure-function relationships, using data from the genomes of several prokaryotes, especially Bacillus subtilis. Many of these functions involve aspects of sugar metabolism and cell wall synthesis and are concerned with responses to abiotic stress such as heat, desiccation, or starvation. Particular emphasis is also given to the oxalate-degrading enzymes from microbes, their biological significance, and their value in a range of medical and other applications.

Human cysteine dioxygenase gene: structural organization, tissue-specific expression and downregulation by phorbol 12-myristate 13-acetate

The organization of the human cysteine dioxygenase (CDO) gene was found to be similar to its rat counterpart, and the location of the introns in the protein structure was identical to the rat CDO gene. The major transcription start site, identified by primer extension, was located 260 bp upstream from the ATG codon. The sequence of the 5'-immediate upstream region was highly conserved between the human and rat CDO genes. The putative promoter region contained a TATA-box-like sequence, and many putative cis-acting elements including HNF5, GRE, TRE, CRE, CArG box, ARE, MBS, and NF-kB. A Northern blot analysis revealed that CDO mRNA was strongly expressed in the liver and placenta, and weakly in the heart, brain and pancreas. CDO mRNA was also detected in human hepatoblastoma HepG2 cells. The CDO mRNA level in HepG2 cells was decreased after 2 h and reached a minimum 6 h-8 h after a phorbol 12-myristate 13-acetate (PMA) treatment, and then gradually returned to the basal level.

Cysteine dioxygenase: regional expression of activity in rat brain

The levels of expression of cysteine dioxygenase (CDO) protein and activity were investigated in nine functionally distinct regions of the rat brain before and after induction with methionine by Western analysis and an activity assay. Activity expression ranged from no activity in the brain-stem to high activity expression in the olfactory bulb and basal ganglia. Upon exposure to 400 mg/l methionine for 5 days, significant induction of expression was observed in the basal ganglia, brain-stem, cerebellum, hippocampus, midbrain and olfactory bulb. Protein expression appeared to correlate with activity expression when levels before and after induction were compared. This non-uniformity of expression may reflect different physiological functions of CDO in these areas.