Cystathionine Β-synthase Research Articles

Post-Traumatic Expressions of Aromatase B, Glutamine Synthetase, and Cystathionine-Beta-Synthase in the Cerebellum of Juvenile Chum Salmon, Oncorhynchus keta.

In adult fish, neurogenesis occurs in many areas of the brain, including the cerebellum, with the ratio of newly formed cells relative to the total number of brain cells being several orders of magnitude greater than in mammals. Our study aimed to compare the expressions of aromatase B (AroB), glutamine synthetase (GS), and cystathionine-beta-synthase (CBS) in the cerebellum of intact juvenile chum salmon, Oncorhynchus keta. To identify the dynamics that determine the involvement of AroB, GS, and CBS in the cellular mechanisms of regeneration, we performed a comprehensive assessment of the expressions of these molecular markers during a long-term primary traumatic brain injury (TBI) and after a repeated acute TBI to the cerebellum of O. keta juveniles. As a result, in intact juveniles, weak or moderate expressions of AroB, GS, and CBS were detected in four cell types, including cells of the neuroepithelial type, migrating, and differentiated cells (graphic abstract, A). At 90 days post injury, local hypercellular areas were found in the molecular layer containing moderately labeled AroB+, GS+, and CBS+ cells of the neuroepithelial type and larger AroB+, GS+, and CBS+ cells (possibly analogous to the reactive glia of mammals); patterns of cells migration and neovascularization were also observed. A repeated TBI caused the number of AroB+, GS+, and CBS+ cells to further increase; an increased intensity of immunolabeling was recorded from all cell types (graphic abstract, C). Thus, the results of this study provide a better understanding of adult neurogenesis in teleost fishes, which is expected to clarify the issue of the reactivation of adult neurogenesis in mammalian species.

ATF3-CBS signaling axis coordinates ferroptosis and tumorigenesis in colorectal cancer

The induction of ferroptosis is promising for cancer therapy. However, the mechanisms enabling cancer cells to evade ferroptosis, particularly in low-cystine environments, remain elusive. Our study delves into the intricate regulatory mechanisms of Activating transcription factor 3 (ATF3) on Cystathionine β-synthase (CBS) under cystine deprivation stress, conferring resistance to ferroptosis in colorectal cancer (CRC) cells. Additionally, our findings establish a positively correlation between this signaling axis and CRC progression, suggesting its potential as a therapeutic target. Mechanistically, ATF3 positively regulates CBS to resist ferroptosis under cystine deprivation stress. In contrast, the suppression of CBS sensitizes CRC cells to ferroptosis through targeting the mitochondrial tricarboxylic acid (TCA) cycle. Notably, our study highlights that the ATF3-CBS signaling axis enhances ferroptosis-based CRC cancer therapy. Collectively, the findings reveal that the ATF3-CBS signaling axis is the primary feedback pathway in ferroptosis, and blocking this axis could be a potential therapeutic approach for colorectal cancer.

Polymorphic substitutions in folate cycle genes as predictors of hyperhomocysteinemia in children

Introduction. Mutant alleles of genes of folate cycle enzymes can lead to the significant deterioration of its function and varying severity of pathology. Several defects in these genes lead to severe hyperhomocysteinemia, the most common form of which is a deficiency of cystathionine beta-synthase B. 
 Aim: to establish polymorphic substitutions in the genes of folate cycle enzymes that contribute to the formation of hyperhomocysteinemia in children.
 Materials and methods. Two hundred seventy one children aged of 13–18 years were examined. The analysis of genetic polymorphisms of the folate cycle was carried out using a molecular genetic method. Quantitative determination of the blood homocysteine and folic acid level was performed by chemiluminescent immunoassay on microparticles. Statistical data processing was carried out using Statistica 6.1 application programs (StatSoft Inc., USA). 
 Results. The frequency of the T allele of the MTHFR 677 gene was revealed to be higher in adolescents of the main group compared with the control (p = 0.043). The frequency of the homozygous genotype 66 AA of the MTRR gene in children of the comparison group was significantly higher (p = 0.049), however, the heterozygous genotype 66 AG of the MTRR gene was significantly more often detected in adolescents of the main group (p = 0.008). The average concentrations of homocysteine in children of the main group were 11.6 mmol/L, in adolescents of the control group 9.3 mmol/L (p = 0.021). Hyperhomocysteinemia in children of the main group was detected in 217 (80.1%) adolescents, and in 57 (49.6%) children of the control group (p < 0.001). The baseline serum folate level was determined in the children of the main group. The average amount of vitamin B9 in the blood of children of the main group was 3.7 ng/ml, and in 145 (53.5%) children this indicator was significantly reduced.
 Conclusion. Low levels of folic acid contribute to an increase in homocysteine in blood plasma. Taking vitamin B9 and vitamin folate complexes significantly reduces the level of homocysteine in blood plasma (p < 0.001).

S-Allyl-L-Cysteine Affects Cell Proliferation and Expression of H2S-Synthetizing Enzymes in MCF-7 and MDA-MB-231 Adenocarcinoma Cell Lines.

S-allyl-L-cysteine (SAC) is a sulfur compound present in fresh garlic. The reference literature describes its anticancer, antioxidant and neuroprotective effects. Breast cancer is infamously known as one of the most commonly diagnosed malignancies among women worldwide. Its morbidity and mortality make it reasonable to complete and expand knowledge on this cancer's characteristics. Hydrogen sulfide (H2S) and its naturally occurring donors are well-known investigation subjects for diverse therapeutic purposes. This study was conducted to investigate the SAC antiproliferative potential and effect on three enzymes involved in H2S metabolism: 3-mercaptopyruvate sulfurtransferase (MPST), cystathionine γ-lyase (CTH), and cystathionine β-synthase (CBS). We chose the in vitro cellular model of human breast adenocarcinomas: MCF-7 and MDA-MB-231. The expression of enzymes after 2, 4, 6, 8, and 24 h incubation with 2.24 mM, 3.37 mM, and 4.50 mM SAC concentrations was examined. The number of living cells was determined by the MTS assay. Changes in cellular plasma membrane integrity were measured by the LDH test. Expression changes at the protein level were analyzed using Western blot. A significant decrease in viable cells was registered for MCF-7 cells after all incubation times upon 4.50 mM SAC exposure, and after 6 and 24 h only in MDA-MB-231 upon 4.50 mM SAC. In both cell lines, the MPST gene expression significantly increased after the 24 h incubation with 4.50 mM SAC. S-allyl-L-cysteine had opposite effects on changes in CTH and CBS expression in both cell lines. In our research model, we confirmed the antiproliferative potential of SAC and concluded that our studies provided current information about the increase in MPST gene expression mediated by S-allyl-L-cysteine in the adenocarcinoma in vitro cellular model for the MCF-7 and MDA-MB-231 cell lines. Further investigation of this in vitro model can bring useful information regarding sulfur enzyme metabolism of breast adenocarcinoma and regulating its activity and expression (gene silencing) in anticancer therapy.

The live biotherapeutic SYNB1353 decreases plasma methionine via directed degradation in animal models and healthy volunteers

Methionine is an essential proteinogenic amino acid, but its excess can lead to deleterious effects. Inborn errors of methionine metabolism resulting from loss of function in cystathionine β-synthase (CBS) cause classic homocystinuria (HCU), which is managed by a methionine-restricted diet. Synthetic biotics are gastrointestinal tract-targeted live biotherapeutics that can be engineered to replicate the benefits of dietary restriction. In this study, we assess whether SYNB1353, an E.coli Nissle 1917 derivative, impacts circulating methionine and homocysteine levels in animals and healthy volunteers. In both mice and nonhuman primates (NHPs), SYNB1353 blunts the appearance of plasma methionine and plasma homocysteine in response to an oral methionine load. A phase 1 clinical study conducted in healthy volunteers subjected to an oral methionine challenge demonstrates that SYNB1353 is well tolerated and blunts plasma methionine by 26%. Overall, SYNB1353 represents a promising approach for methionine reduction with potential utility for the treatment of HCU.

Understanding cystathionine beta synthase mechanism of action and interaction with substrates, product, inhibitors, allosteric modulators

Understanding cystathionine beta synthase mechanism of action and interaction with substrates, product, inhibitors, allosteric modulators

Hydrogen sulfide reduces oxidative stress in Huntington's disease via Nrf2.

JOURNAL/nrgr/04.03/01300535-202506000-00028/figure1/v/2024-08-05T133530Z/r/image-tiff The pathophysiology of Huntington's disease involves high levels of the neurotoxin quinolinic acid. Quinolinic acid accumulation results in oxidative stress, which leads to neurotoxicity. However, the molecular and cellular mechanisms by which quinolinic acid contributes to Huntington's disease pathology remain unknown. In this study, we established in vitro and in vivo models of Huntington's disease by administering quinolinic acid to the PC12 neuronal cell line and the striatum of mice, respectively. We observed a decrease in the levels of hydrogen sulfide in both PC12 cells and mouse serum, which was accompanied by down-regulation of cystathionine β-synthase, an enzyme responsible for hydrogen sulfide production. However, treatment with NaHS (a hydrogen sulfide donor) increased hydrogen sulfide levels in the neurons and in mouse serum, as well as cystathionine β-synthase expression in the neurons and the mouse striatum, while also improving oxidative imbalance and mitochondrial dysfunction in PC12 cells and the mouse striatum. These beneficial effects correlated with upregulation of nuclear factor erythroid 2-related factor 2 expression. Finally, treatment with the nuclear factor erythroid 2-related factor 2 inhibitor ML385 reversed the beneficial impact of exogenous hydrogen sulfide on quinolinic acid-induced oxidative stress. Taken together, our findings show that hydrogen sulfide reduces oxidative stress in Huntington's disease by activating nuclear factor erythroid 2-related factor 2, suggesting that hydrogen sulfide is a novel neuroprotective drug candidate for treating patients with Huntington's disease.

METHYLATION-ASSOCIATED PATHWAYS IN MACULAR TELANGIECTASIA TYPE 2 AND OPHTHALMOLOGIC FINDINGS IN PATIENTS WITH GENETIC METHYLATION DISORDERS.

Serine (Ser) and glycine (Gly) levels were reported to differ between patients with macular telangiectasia type 2 (MacTel) compared with healthy controls. Because they are closely related to methylation metabolism, this report investigates methylation-associated metabolite levels in patients with MacTel and retinal changes in monogenetic methylation disorders. Prospective, monocentric study on patients with MacTel and healthy controls underwent a standardized protocol including a blood draw. Methylation-associated metabolite levels in plasma were determined using targeted quantitative metabolomics. Furthermore, patient records of cystathionine beta-synthase, methylenetetrahydrofolate reductase, and methylmalonic aciduria and homocystinuria type C protein (MMACHC) deficiency were screened for reported retinal changes. In total, 29 patients with MacTel and 27 healthy controls were included. Patients with MacTel showed lower plasma Ser ( P = 0.02 and P = 0.01) and Gly ( P = 0.11 and P = 0.11) levels than controls. Principal component analyses revealed that methylation-associated metabolite, especially homocysteine, contributed to a distinct clustering of patients with MacTel. No retinal changes were seen in cystathionine beta-synthase (n = 1) and methylenetetrahydrofolate reductase (n = 2) deficiency, while two patients with MMACHC (n = 4) deficiency displayed extensive macular dystrophy. Patients with MacTel show distinct clustering of methylation-associated metabolite compared with controls. Of the three homocystinurias, only MMACHC resulted in macular dystrophy, possibly due to distinct compensatory pathways.

First clinical evidence that trimethylsulfonium can serve as a biomarker for the production of the signaling molecule hydrogen sulfide

BackgroundHydrogen sulfide (H2S) is established as the third gaseous signaling molecule and is known to be overproduced in down syndrome (DS) due to the extra copy of the CBS gene on chromosome 21, which has been suggested to contribute to the clinical manifestation of this condition. We recently discovered trimethylsulfonium (TMS) in human urine and highlighted its potential as a selective methylation metabolite of endogenously produced H2S, but the clinical utility of this novel metabolite has not been previously investigated. We hypothesize that the elevation of H2S production in DS would be reflected by an elevation in the methylation product TMS. MethodsTo test this hypothesis, a case-control study was performed and the urinary levels of TMS were found to be higher in the DS group (geo. mean 4.5 nM, 95 % CI 2.4–3.9) than in the control (N) group (3.1 nM, 3.5–6.0), p-value 0.01, whereas the commonly used biomarker of hydrogen sulfide, thiosulfate, failed to reflect this alteration in H2S production (15 µM (N) vs. 13 µM (DS), p-value 0.24. ResultsThe observed association is in line with the proposed hypothesis and provides first clinical evidence of the utility of TMS as a novel and more sensitive biomarker for the endogenous production of the third gaseous signaling molecule than the conventionally used biomarker thiosulfate, which is heavily dependent on bacterial hydrogen sulfide production. ConclusionThis work shows that TMS must be explored in clinical conditions where altered metabolism of hydrogen sulfide is implicated.

Association of Altered Ratio of Maternal Folic Acid and Vitamin B12 during Pregnancy with Newborn Birth Weight, Head Circumference, and Chest Circumference

Objective This study evaluated the effect of an altered ratio of maternal RBC folate (MRF) to serum vitamin B12 (MB12) on pregnancy and newborn outcomes. Methods Blood samples were collected from pregnant women and the umbilical cord at the time of delivery. Estimations of RBC folate and serum vitamin B12 from maternal and cord blood samples and total homocysteine (HCY) were performed. Maternal and newborn anthropometric parameters like placental weight (PW), head circumference (HC), chest circumference (CC), and body weight (BW) were measured in offsprings after birth. We stratified the pregnant women into six groups (a) vitamin B12 normal and folic acid normal (BNFN)-control group, (b) vitamin B12 normal and folic acid elevated (BNFE), (c) vitamin B12 normal and folic acid deficient (BNFD), (d) vitamin B12 deficient and folic acid normal (BDFN), (e) vitamin B12 deficient and folic acid elevated (BDFE) and (f) vitamin B12 deficient and folic acid deficient (BDFD) based on their levels of RBC folate (MRF) and vitamin B12 (MB12). The expression of the one-carbon metabolism genes (methionine synthase (MS), glycine N-methyltransferase (GNMT), and cystathionine β-synthase (CBS) was also studied in placental tissue by using real-time PCR. Results Cord blood RBC folate was significantly reduced in groups BDFE and BDFD as compared to the control group (BNFN). The cord blood vitamin B12 levels were also reduced in the BDFE group as compared to the BDFD. All the newborn parameters viz. PW, HC, CC, and BW, were reduced in the altered MRF/MB12 ratio (low & high vs. normal ratio). Total HCY was significantly elevated in the groups with (BDFE & BDFN) an imbalance of maternal RBC folate and serum vitamin B12 as compared to the control group. Downregulation of one-carbon metabolism genes like MS (p < 0.001), GNMT (p < 0.05), and CBS (p < 0.01) in placental tissue was observed in the high MRF/MB12 ratio group as compared to the normal ratio group. A strong positive correlation was also observed between MRF, MB12, and newborn parameters. Conclusions The altered ratio of folate to vitamin B12 in the maternal blood is associated with adverse growth and development of the newborn.

Homocysteine and mitochondrial quality control in diabetic retinopathy

BackgroundDiabetic retinopathy is a progressive disease, and one of the key metabolic abnormalities in the pathogenesis of diabetic retinopathy, mitochondrial damage, is also influenced by the duration of hyperglycemia. Mitochondrial quality control involves a coordination of mitochondrial dynamics, biogenesis and removal of the damaged mitochondria. In diabetes, these processes are impaired, and the damaged mitochondria continue to produce free radicals. Diabetic patients also have high homocysteine and reduced levels of hydrogen sulfide, and hyperhomocysteinemia is shown to exacerbate diabetes-induced mitochondrial damage and worsen their dynamics. This study aims to investigate the temporal relationship between hyperhomocysteinemia and retinal mitochondrial quality control in diabetic retinopathy.MethodsHuman retinal endothelial cells incubated in 20 mM d-glucose for 24 to 96 h, in the absence or presence of 100 µM homocysteine, with/without a hydrogen sulfide donor GYY4137, were analyzed for mitochondrial ROS (MitoSox fluorescence), DNA damage (transcripts of mtDNA-encoded ND6 and CytB), copy numbers, oxygen consumption rate (Seahorse XF analyzer) and mitophagy (mitophagosomes immunofluorescence labeling and flow cytometry). Results were confirmed in the retina from mice genetically manipulated for hyperhomocysteinemia (cystathionine β-synthase deficient mice, Cbs+/−), streptozotocin-induced diabetic for 8 to 24 weeks. At 24 weeks of diabetes, vascular health was evaluated by counting acellular capillaries in the trypsin digested retinal vasculature and by fluorescein angiography.ResultsHomocysteine, in high glucose medium, exacerbated mitochondrial ROS production, mtDNA damage and impaired mitochondrial respiration within 24 h, and slowed down/worsened mitochondrial biogenesis and mitophagy, as compared to 48 to 96 h in high glucose alone. GYY4137 supplementation ameliorated homocysteine + high glucose-induced mitochondrial damage and impairment in biogenesis and mitophagy. Similar results were obtained from Cbs+/− mice-mitochondrial ROS, mtDNA damage and decline in biogenesis and mitophagy were observed within eight weeks of diabetes vs. 16 to 24 weeks of diabetes in Cbs+/+ mice, and at 24 weeks of diabetes, Cbs+/− mice had significantly higher acellular capillaries and vascular leakage.ConclusionsHyperhomocysteinemia, in a hyperglycemic environment, overwhelms the mitochondria, accelerating and exacerbating their dysfunction, and also delays/worsens their removal, augmenting the development of diabetic retinopathy. Thus, our results strengthen the importance of maintaining homocysteine-hydrogen sulfide balance during the early stages of diabetes for a patient to prevent/retard vision loss.

Breast cancer cells have an increased ferroptosis risk induced by system xc− blockade after deliberately downregulating CYTL1 to mediate malignancy

Cytokine-like protein 1 (CYTL1) expression is deliberately downregulated during the progression of multiple types of cancers, especially breast cancer. However, the metabolic characteristics of cancer progression remain unclear. Here, we uncovered a risk of breast cancer cells harboring low CYTL1 expression, which is metabolically controlled during malignant progression. We performed metabolism comparison and revealed that breast cancer cells with low CYTL1 expression have highly suppressed transsulfuration activity that is driven by cystathionine β-synthase (CBS) and contributes to de novo cysteine synthesis. Mechanistically, CYTL1 activated Nrf2 by promoting autophagic Keap1 degradation, and Nrf2 subsequently transactivated CBS expression. Due to the lack of cellular cysteine synthesis, breast cancer cells with low CYTL1 expression showed hypersensitivity to system xc− blockade-induced ferroptosis in vitro and in vivo. Silencing CBS counteracted CYTL1-mediated ferroptosis resistance. Our results show the importance of exogeneous cysteine in breast cancer cells with low CYTL1 expression and highlight a potential metabolic vulnerability to target.

Heat shock factor 1 directly regulates transsulfuration pathway to promote prostate cancer proliferation and survival

There are limited therapeutic options for patients with advanced prostate cancer (PCa). We previously found that heat shock factor 1 (HSF1) expression is increased in PCa and is an actionable target. In this manuscript, we identify that HSF1 regulates the conversion of homocysteine to cystathionine in the transsulfuration pathway by altering levels of cystathionine-β-synthase (CBS). We find that HSF1 directly binds the CBS gene and upregulates CBS mRNA levels. Targeting CBS decreases PCa growth and induces tumor cell death while benign prostate cells are largely unaffected. Combined inhibition of HSF1 and CBS results in more pronounced inhibition of PCa cell proliferation and reduction of transsulfuration pathway metabolites. Combination of HSF1 and CBS knockout decreases tumor size for a small cell PCa xenograft mouse model. Our study thus provides new insights into the molecular mechanism of HSF1 function and an effective therapeutic strategy against advanced PCa.

Middle aged CAMKII-Cre:Cbsfl/fl mice: a new model for studying perioperative neurocognitive disorders.

Postoperative complications, such as perioperative neurocognitive disorders (PND), have become a major issue affecting surgical outcomes. However, the mechanism of PND remains unclear, and stable animal models of middle-aged PND are lacking. S-adenosylmethionine (SAM), a cystathionine beta-synthase (CBS) allosteric activator, can reduce the level of plasma homocysteine and prevent the occurrence of PND. However, the time and resource-intensive process of constructing models of PND in elderly animals have limited progress in PND research and innovative therapy development. The present study aimed to construct a stable PND model in middle-aged CAMKII-Cre:Cbsfl/fl mice whose Cbs was specifically knocked out in CAMKII positive neurons. Behavioral tests showed that these middle-aged mice displayed cognitive deficits which were aggravated by exploratory laparotomy under isoflurane anesthesia. Compared with typical PND mice which were 18-month-old, these middle-aged mice showed similar cognitive deficits after undergoing exploratory laparotomy under isoflurane anesthesia. Though there was no significant difference in the number of neurons in either the hippocampus or the cortex, a significant increase in numbers of microglia and astrocytes in the hippocampus was observed. These indicate that middle-aged CAMKII-Cre:Cbsfl/fl mice can be used as a new PND model for mechanistic studies and therapy development for PND.

Gaseous inhibition of the transsulfuration pathway by cystathionine β-synthase.

The transsulfuration pathway plays a key role in mammals for maintaining the balance between cysteine and homocysteine, whose concentrations are critical in several biochemical processes. Human cystathionine β-synthase is a heme-containing, pyridoxal 5'-phosphate (PLP)-dependent enzyme found in this pathway. The heme group does not participate directly in catalysis, but has a regulatory function, whereby CO or NO binding inhibits the PLP-dependent reactions. In this study, we explore the detailed structural changes responsible for inhibition using quantum chemical calculations to validate the experimentally observed bonding patterns associated with heme CO and NO binding and molecular dynamics simulations to explore the medium-range structural changes triggered by gas binding and propagating to the PLP active site, which is more than 20 Å distant from the heme group. Our results support a previously proposed mechanical signaling model, whereby the cysteine decoordination associated with gas ligand binding leads to breaking of a hydrogen bond with an arginine residue on a neighbouring helix. In turn, this leads to a shift in position of the helix, and hence also of the PLP cofactor, ultimately disrupting a key hydrogen bond that stabilizes the PLP in its catalytically active form.

An adult with cystathionine beta-synthase deficiency, camptodactyly-arthropathy-coxa vara-pericarditis syndrome, and deafness: A case report.

Massive sequencing platforms allow the identification of complex clinical phenotypes involving more than one autosomal recessive disorder. In this study, we report on an adult patient, born to a related couple (third degree cousins), referred for genetic evaluation due to ectopia lentis, deafness and previous diagnosis of juvenile idiopathic arthritis. He was biochemically diagnosed as having Classic Homocystinuria (HCU); Sanger sequencing of the CBS gene showed the genotype NM_000071.2(CBS):c.[833T>C];[833T>C], compatible with the diagnosis of pyridoxine-responsive HCU. As he also had symptoms not usually associated with HCU, exome sequencing was performed. In addition to the variants found in the Sanger sequencing, the following variants were identified: NM_001256317.1(TMPRSS3):c.[413C>A];[413C>A]; and the NM_005807.6(PRG4):c.[3756dup]:[3756dup], confirming the diagnosis of autosomal recessive nonsyndromic deafness and Camptodactyly-Arthropathy-Coxa Vara-Pericarditis Syndrome (CACP), respectively. Genomic analysis allowed the refinement of the diagnosis of a complex case and improvement of the patient's treatment.

H2S-Synthesizing Enzymes Are Putative Determinants in Lung Cancer Management toward Personalized Medicine.

Lung cancer is a lethal disease with no truly efficient therapeutic management despite the progresses, and metabolic profiling can be a way of stratifying patients who may benefit from new therapies. The present study is dedicated to profiling cysteine metabolic pathways in NSCLC cell lines and tumor samples. This was carried out by analyzing hydrogen sulfide (H2S) and ATP levels, examining mRNA and protein expression patterns of cysteine catabolic enzymes and transporters, and conducting metabolomics analysis using nuclear magnetic resonance (NMR) spectroscopy. Selenium-chrysin (SeChry) was tested as a therapeutic alternative with the aim of having an effect on cysteine catabolism and showed promising results. NSCLC cell lines presented different cysteine metabolic patterns, with A549 and H292 presenting a higher reliance on cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) to maintain H2S levels, while the PC-9 cell line presented an adaptive behavior based on the use of mercaptopyruvate sulfurtransferase (MST) and cysteine dioxygenase (CDO1), both contributing to the role of cysteine as a pyruvate source. The analyses of human lung tumor samples corroborated this variability in profiles, meaning that the expression of certain genes may be informative in defining prognosis and new targets. Heterogeneity points out individual profiles, and the identification of new targets among metabolic players is a step forward in cancer management toward personalized medicine.

Differences in nonoxidative sulfur metabolism between normal human breast MCF-12A and adenocarcinoma MCF-7 cell lines

Recent studies have revealed the role of endogenous hydrogen sulfide (H2S) in the development of breast cancer. The capacity of cells to generate H2S and the activity and expression of the main enzymes (cystathionine beta synthase; CBS, cystathionase γ-lyase; CGL, 3-mercaptopyruvate sulfurtransferase; MPST and thiosulfate sulfurtransferase; TST) involved in H2S metabolism were analyzed using an in vitro model of a non-tumourigenic breast cell line (MCF-12A) and a human breast adenocarcinoma cell line (MCF-7). In both cell lines, MPST, CGL, and TST expression was confirmed at the mRNA (RT-PCR) and the protein (Western Blot) level, while CBS expression was detected only in MCF-7 cells. Elevated levels of GSH, sulfane sulfur and increased CBS and TST activity were presented in the MCF-7 compared to the MCF-12A cells. It appears that cysteine might be mainly a substrate for GSH synthesis in breast adenocarcinoma. Increased capacity of the cells to generate H2S was shown for MCF-12A compared to MCF-7 cell line. Results suggest an important function of CBS in H2S metabolism in breast adenocarcinoma. The presented work may contribute to further research on new therapeutic possibilities for breast cancer - one of the most frequently diagnosed types of cancer among women.

Differential Impact of VNTR Polymorphism in the CBS Gene on Gastric and Breast Cancers Risk

Differential Impact of VNTR Polymorphism in the CBS Gene on Gastric and Breast Cancers Risk

The Structure and Nucleotide-Binding Characteristics of Regulated Cystathionine β-Synthase Domain-Containing Pyrophosphatase without One Catalytic Domain.

Regulatory adenine nucleotide-binding cystathionine β-synthase (CBS) domains are widespread in proteins; however, information on the mechanism of their modulating effects on protein function is scarce. The difficulty in obtaining structural data for such proteins is ascribed to their unusual flexibility and propensity to form higher-order oligomeric structures. In this study, we deleted the most movable domain from the catalytic part of a CBS domain-containing bacterial inorganic pyrophosphatase (CBS-PPase) and characterized the deletion variant both structurally and functionally. The truncated CBS-PPase was inactive but retained the homotetrameric structure of the full-size enzyme and its ability to bind a fluorescent AMP analog (inhibitor) and diadenosine tetraphosphate (activator) with the same or greater affinity. The deletion stabilized the protein structure against thermal unfolding, suggesting that the deleted domain destabilizes the structure in the full-size protein. A "linear" 3D structure with an unusual type of domain swapping predicted for the truncated CBS-PPase by Alphafold2 was confirmed by single-particle electron microscopy. The results suggest a dual role for the CBS domains in CBS-PPase regulation: they allow for enzyme tetramerization, which impedes the motion of one catalytic domain, and bind adenine nucleotides to mitigate or aggravate this effect.