In silico approaches to study the human asparagine synthetase: An insight of the interaction between the enzyme active sites and its substrates.

Cancer is a leading concern and important cause of death worldwide. Cancer is a non-communicable illness defined as uncontrolled division of cells. It can develop into metastatic cancer when tumor cells migrate to other organs. In recent years evidence has emerged that the bioavailability of Asn play a crucial role in cancer metastasis. Asn is a non-essential amino acid formed from an ATP dependent catalyzed reaction by the enzyme asparagine synthetase (ASNS), where Asp and Gln are converted to Asn and Glu, respectively. The human ASNS enzyme consist of 561 amino acids, with a molecular weight of 64 KDa. ASNS governs the activation of transcriptional factors that regulate the process of metastasis. In this work the 3D model of ASNS in E. coli (AS-B) and the human ASNS docked with its different ligands have been used to study the 3D mechanism of the conversion of Asp and Gln to Asn and Glu, in human ASNS. The stability evaluation of the docked complexes was checked by molecular dynamic simulation through the bioinformatic tool Desmond. The binding residues and their interactions can be exploited for the development of inhibitors, as well as for finding new drug molecules against ASNS and prevention of metastatic cancer.

Biochemical characterization of l-asparagine synthetase from Streptococcus thermophilus and its application in the enzymatic synthesis of ß-aspartyl compounds.

ß-Aspartyl compounds, such as ß-aspartyl hydroxamate (serine racemase inhibitor), ß-aspartyl-l-lysine (moisture retention), and ß-aspartyl-l-tryptophan (immunomodulator) are physiologically active compounds. There is limited literature on the development of effective methods of production of ß-aspartyl compounds. In this study, we describe the biochemical characterization of asparagine synthetase (AS) from Streptococcus thermophilus NBRC 13957 (StAS) and the enzymatic synthesis of ß-aspartyl compounds using StAS. Recombinant StAS was expressed in Escherichia coli BL21(DE3) and it displayed activity towards hydroxylamine, methylamine, ethylamine, and ammonia, as acceptors of the ß-aspartyl moiety. StAS exhibited higher activity toward hydroxylamine and ethylamine as acceptor substrates compared with the enzymes from Lactobacillus delbrueckii NBRC 13953, Lactobacillus reuteri NBRC 15892, and E. coli. The coupling of the synthesis of ß-aspartyl compounds by StAS with an ATP-regeneration system using polyphosphate kinase from Deinococcus proteoliticus NBRC 101906 displayed an approximately 2.5-fold increase in the production of ß-aspartylhydroxamate from 1.06 mM to 2.53 mM after a 76-h reaction.

Exploring the potential of asparagine restriction in solid cancer treatment: recent discoveries, therapeutic implications, and challenges.

Asparagine is a non-essential amino acid crucial for protein biosynthesis and function, and therefore cell maintenance and growth. Furthermore, this amino acid has an important role in regulating several metabolic pathways, such as tricarboxylic acid cycle and the urea cycle. When compared to normal cells, tumor cells typically present a higher demand for asparagine, making it a compelling target for therapy. In this review article, we investigate different facets of asparagine bioavailability intricate role in malignant tumors raised from solid organs. We take a comprehensive look at asparagine synthetase expression and regulation in cancer, including the impact on tumor growth and metastasis. Moreover, we explore asparagine depletion through L-asparaginase as a potential therapeutic method for aggressive solid tumors, approaching different formulations of the enzyme and combinatory therapies. In summary, here we delve into studies about endogenous and exogenous asparagine availability in solid cancers, analyzing therapeutic implications and future challenges.

Growth characteristics of HCT116 xenografts lacking asparagine synthetase vary according to sex.

BACKGROUND: Sex-related differences in colorectal (CRC) incidence and mortality are well-documented. However, the impact of sex on metabolic pathways that drive cancer growth is not well understood. High expression of asparagine synthetase (ASNS) is associated with inferior survival for female CRC patients only. Here, we used a CRISPR/Cas9 technology to generate HCT116 ASNS-/- and HCT 116 ASNS+/+ cancer cell lines. We examine the effects of ASNS deletion on tumor growth and the subsequent rewiring of metabolic pathways in male and female Rag2/IL2RG mice. RESULTS: ASNS loss reduces cancer burden in male and female tumor-bearing mice (40% reduction, q < 0.05), triggers metabolic reprogramming including gluconeogenesis, but confers a survival improvement (30 days median survival, q < 0.05) in female tumor-bearing mice alone. Transcriptomic analyses revealed upregulation of G-protein coupled estrogen receptor (GPER1) in tumors from male and female mice with HCT116 ASNS-/- xenograft. Estradiol activates GPER1 in vitro in the presence of ASNS and suppresses tumor growth. CONCLUSIONS: Our study indicates that inferior survival for female CRC patients with high ASNS may be due to metabolic reprogramming that sustains tumor growth. These findings have translational relevance as ASNS/GPER1 signaling could be a future therapeutic target to improve the survival of female CRC patients.

Reverse Phase Proteomic Array Profiling of Asparagine Synthetase Expression in Newly Diagnosed Acute Myeloid Leukemia.

Asparaginase-based therapy is a cornerstone in acute lymphoblastic leukemia (ALL) treatment, capitalizing on the methylation status of the asparagine synthetase (ASNS) gene, which renders ALL cells reliant on extracellular asparagine. Contrastingly, ASNS expression in acute myeloid leukemia (AML) has not been thoroughly investigated, despite studies suggesting that AML with chromosome 7/7q deletions might have reduced ASNS levels. Here, we leverage reverse phase protein arrays to measure ASNS expression in 810 AML patients and assess its impact on outcomes. We find that AML with inv(16) has the lowest overall ASNS expression. While AML with deletion 7/7q had ASNS levels slightly lower than those of AML without deletion 7/7q, this observation was not significant. Low ASNS expression correlated with improved overall survival (46 versus 54 weeks, respectively, p = 0.011), whereas higher ASNS levels were associated with better response to venetoclax-based therapy. Protein correlation analysis demonstrated association between ASNS and proteins involved in methylation and DNA repair. In conclusion, while ASNS expression was not lower in patients with deletion 7/7q as initially predicted, ASNS levels were highly variable across AML patients. Further studies are needed to assess whether patients with low ASNS expression are susceptible to asparaginase-based therapy due to their inability to augment compensatory ASNS expression upon asparagine depletion.

Inhibition of asparagine synthetase effectively retards polycystic kidney disease progression.

Polycystic kidney disease (PKD) is a genetic disorder characterized by bilateral cyst formation. We showed that PKD cells and kidneys display metabolic alterations, including the Warburg effect and glutaminolysis, sustained in vitro by the enzyme asparagine synthetase (ASNS). Here, we used antisense oligonucleotides (ASO) against Asns in orthologous and slowly progressive PKD murine models and show that treatment leads to a drastic reduction of total kidney volume (measured by MRI) and a prominent rescue of renal function in the mouse. Mechanistically, the upregulation of an ATF4-ASNS axis in PKD is driven by the amino acid response (AAR) branch of the integrated stress response (ISR). Metabolic profiling of PKD or control kidneys treated with Asns-ASO or Scr-ASO revealed major changes in the mutants, several of which are rescued by Asns silencing in vivo. Indeed, ASNS drives glutamine-dependent de novo pyrimidine synthesis and proliferation in cystic epithelia. Notably, while several metabolic pathways were completely corrected by Asns-ASO, glycolysis was only partially restored. Accordingly, combining the glycolytic inhibitor 2DG with Asns-ASO further improved efficacy. Our studies identify a new therapeutic target and novel metabolic vulnerabilities in PKD.

Asparagine Synthetase Marks a Distinct Dependency Threshold for Cardiomyocyte Dedifferentiation.

BACKGROUND: Adult mammalian cardiomyocytes have limited proliferative capacity, but in specifically induced contexts they traverse through cell-cycle reentry, offering the potential for heart regeneration. Endogenous cardiomyocyte proliferation is preceded by cardiomyocyte dedifferentiation (CMDD), wherein adult cardiomyocytes revert to a less matured state that is distinct from the classical myocardial fetal stress gene response associated with heart failure. However, very little is known about CMDD as a defined cardiomyocyte cell state in transition. METHODS: Here, we leveraged 2 models of in vitro cultured adult mouse cardiomyocytes and in vivo adeno-associated virus serotype 9 cardiomyocyte-targeted delivery of reprogramming factors (Oct4, Sox2, Klf4, and Myc) in adult mice to study CMDD. We profiled their transcriptomes using RNA sequencing, in combination with multiple published data sets, with the aim of identifying a common denominator for tracking CMDD. RESULTS: RNA sequencing and integrated analysis identified Asparagine Synthetase (Asns) as a unique molecular marker gene well correlated with CMDD, required for increased asparagine and also for distinct fluxes in other amino acids. Although Asns overexpression in Oct4, Sox2, Klf4, and Myc cardiomyocytes augmented hallmarks of CMDD, Asns deficiency led to defective regeneration in the neonatal mouse myocardial infarction model, increased cell death of cultured adult cardiomyocytes, and reduced cell cycle in Oct4, Sox2, Klf4, and Myc cardiomyocytes, at least in part through disrupting the mammalian target of rapamycin complex 1 pathway. CONCLUSIONS: We discovered a novel gene Asns as both a molecular marker and an essential mediator, marking a distinct threshold that appears in common for at least 4 models of CMDD, and revealing an Asns/mammalian target of rapamycin complex 1 axis dependency for dedifferentiating cardiomyocytes. Further study will be needed to extrapolate and assess its relevance to other cell state transitions as well as in heart regeneration.

[Clinical and genetic spectrum of 6 cases with asparagine synthetase deficiency].

Objective: To explore the clinical and genetic characteristics of asparagine synthase deficiency. Methods: Case series studies. Retrospective analysis and summary of the clinical data of 6 cases with asparagine synthase deficiency who were diagnosed by genetic testing and admitted to the Third Affiliated Hospital of Zhengzhou University from May 2017 to April 2023 were analyzed retrospectively. The main clinical features, laboratory and imaging examination characteristics of the 6 cases were summarized, and the gene variation sites of them were analyzed. Results: All of the 6 cases were male, with onset ages ranging from 1 month to 1 year and 4 months. All of the 6 cases had cognitive and motor developmental delay, with 3 cases starting with developmental delay, 3 cases starting with convulsions and later experiencing developmental arrest or even regression. All of 6 cases had epilepsy, in whom 2 cases with severe microcephaly developed epileptic encephalopathy in the early stages of infancy with spasms as the main form of convulsions, 4 cases with mild or no microcephaly gradually evolved into convulsions with no fever after multiple febrile convulsions with focal seizures, tonic clonic seizures and tonic seizure as the main forms of convulsions. Three cases of 4 gradually developed into stagnation or even regression of development and ataxia after multiple convulsions with no fever. There were normal cranial imaging in 2 cases, dysplasia of the brains in 1 cases, frontal lobe apex accompanied by abnormal white matter signal in the frontal lobe and thin corpus callosum in 1 case, thin corpus callosum and abnormal lateral ventricular morphology in 1 case, and normal in early stage, but gradually developing into cerebellar atrophy at the age of 5 years and 9 months in 1 case. Two cases underwent visual evoked potential tests, the results of which were both abnormal. Three cases underwent auditory evoked potential examination, with 1 being normal and 2 being abnormal. All of 6 cases had variations in the asparagine synthase gene, with 2 deletion variations and 7 missense variations. The variations of 2 cases had not been reported so far, including c.1341_1343del and c.1283A>G, c.1165_1167del and c.1075G>A. The follow-up time ranged from 3 months to 53 months. Two cases who had severe microcephaly died in infancy, while the other 4 cases with mild or no microcephaly were in survival states until the follow-up days but the control of epilepsy was poor. Conclusions: Asparagine synthase deficiency has a certain degree of heterogeneity in clinical phenotype. Children with obvious microcephaly often present as severe cases, while children with mild or no microcephaly have relatively mild clinical manifestations. The variation of asparagine synthetase gene is mainly missense variation.

Utility of ASNS gene methylation evaluated with the HPLC method as a pharmacogenomic biomarker to predict asparaginase sensitivity in BCP-ALL.

Asparaginase is an important agent for the treatment of acute lymphoblastic leukaemia (ALL), but it is occasionally associated with severe adverse events. Thus, for safer and more efficacious therapy, a clinical biomarker predicting asparaginase sensitivity is highly anticipated. Asparaginase depletes serum asparagine by deaminating asparagine into aspartic acid, and ALL cells are thought to be sensitive to asparaginase due to reduced asparagine synthetase (ASNS) activity. We have recently shown that allele-specific methylation of the ASNS gene is highly involved in asparaginase sensitivity in B-precursor ALL (BCP-ALL) by using next-generation sequence (NGS) analysis of bisulphite PCR products of the genomic DNA. Here, we sought to confirm the utility of methylation status of the ASNS gene evaluated with high-performance liquid chromatography (HPLC) analysis of bisulphite PCR products for future clinical applications. In the global methylation status of 23 CpG sites at the boundary region of promoter and exon 1 of the ASNS gene, a strong positive correlation was confirmed between the mean percent methylation evaluated with the HPLC method and that with the NGS method in 79 BCP-ALL cell lines (R2 = 0.85, p = 1.3 × 10-33) and in 63 BCP-ALL clinical samples (R2 = 0.84, p = 5.0 × 10-26). Moreover, methylation status of the ASNS gene evaluated with the HPLC method was significantly associated with in vitro asparaginase sensitivities as well as gene and protein expression levels of ASNS. These observations indicated that the ASNS gene methylation status evaluated with the HPLC method is a reliable biomarker for predicting the asparaginase sensitivity of BCP-ALL.

Ketogenic diet-responsive drug-resistant epilepsy in a case of asparagine synthetase deficiency with a novel compound heterozygous missense variant.

Asparagine synthetase deficiency (ASNSD) is a rare autosomal recessive neurometabolic disorder caused by homozygous or compound heterozygous mutations in the ASNS gene. Most of the patients have early-onset intractable seizures. A 7-year-old boy was first admitted to our clinic with intractable febrile and afebrile seizures that started when he was 6 months old. He had axial hypotonia with spastic quadriparesis, mild facial dysmorphism, and acquired microcephaly at 1 year-old. Metabolic tests showed a borderline-low serum asparagine level. The electroencephalogram demonstrated epileptic discharges with a high incidence of multifocal spike-wave activity. Brain MRI showed mild cerebral atrophy. His seizures continued despite combinations of multiple antiseizure agents. Whole-exome sequencing (WES) revealed a novel compound heterozygous missense variant of the ASNS gene, and the variants were confirmed by Sanger sequencing. He was started on a ketogenic diet at five years and six months of age. In the first month of the ketogenic diet, we observed that the frequency of seizures significantly decreased. He showed a remarkable improvement in seizures and milder improvement in cognitive skills. To our knowledge, our case is the first report describing significant improvement with a ketogenic diet in intractable seizures due to ASNSD.

Metabolomic Profiling of Asparagine Deprivation in Asparagine Synthetase Deficiency Patient-Derived Cells.

The natural amino acid asparagine (Asn) is required by cells to sustain function and proliferation. Healthy cells can synthesize Asn through asparagine synthetase (ASNS) activity, whereas specific cancer and genetically diseased cells are forced to obtain asparagine from the extracellular environment. ASNS catalyzes the ATP-dependent synthesis of Asn from aspartate by consuming glutamine as a nitrogen source. Asparagine Synthetase Deficiency (ASNSD) is a disease that results from biallelic mutations in the ASNS gene and presents with congenital microcephaly, intractable seizures, and progressive brain atrophy. ASNSD often leads to premature death. Although clinical and cellular studies have reported that Asn deprivation contributes to the disease symptoms, the global metabolic effects of Asn deprivation on ASNSD-derived cells have not been studied. We analyzed two previously characterized cell culture models, lymphoblastoids and fibroblasts, each carrying unique ASNS mutations from families with ASNSD. Metabolomics analysis demonstrated that Asn deprivation in ASNS-deficient cells led to disruptions across a wide range of metabolites. Moreover, we observed significant decrements in TCA cycle intermediates and anaplerotic substrates in ASNS-deficient cells challenged with Asn deprivation. We have identified pantothenate, phenylalanine, and aspartate as possible biomarkers of Asn deprivation in normal and ASNSD-derived cells. This work implies the possibility of a novel ASNSD diagnostic via targeted biomarker analysis of a blood draw.

Transcriptional repressor RST1 controls salt tolerance and grain yield in rice by regulating gene expression of asparagine synthetase.

Salt stress impairs nutrient metabolism in plant cells, leading to growth and yield penalties. However, the mechanism by which plants alter their nutrient metabolism processes in response to salt stress remains elusive. In this study, we identified and characterized the rice (Oryza sativa) rice salt tolerant 1 (rst1) mutant, which displayed improved salt tolerance and grain yield. Map-based cloning revealed that the gene RST1 encoded an auxin response factor (OsARF18). Molecular analyses showed that RST1 directly repressed the expression of the gene encoding asparagine synthetase 1 (OsAS1). Loss of RST1 function increased the expression of OsAS1 and improved nitrogen (N) utilization by promoting asparagine production and avoiding excess ammonium (NH4+) accumulation. RST1 was undergoing directional selection during domestication. The superior haplotype RST1Hap III decreased its transcriptional repression activity and contributed to salt tolerance and grain weight. Together, our findings unravel a synergistic regulator of growth and salt tolerance associated with N metabolism and provide a new strategy for the development of tolerant cultivars.

Targeting Asparagine Synthetase in Tumorgenicity Using Patient-Derived Tumor-Initiating Cells.

Reprogramming of energy metabolism is regarded as one of the hallmarks of cancer; in particular, oncogenic RAS has been shown to be a critical regulator of cancer metabolism. Recently, asparagine metabolism has been heavily investigated as a novel target for cancer treatment. For example, Knott et al. showed that asparagine bioavailability governs metastasis in a breast cancer model. Gwinn et al. reported the therapeutic vulnerability of asparagine biosynthesis in KRAS-driven non-small cell lung cancer. We previously reported that KRAS-mutated CRC cells can adapt to glutamine depletion through upregulation of asparagine synthetase (ASNS), an enzyme that synthesizes asparagine from aspartate. In our previous study, we assessed the efficacy of asparagine depletion using human cancer cell lines. In the present study, we evaluated the clinical relevance of asparagine depletion using a novel patient-derived spheroid xenograft (PDSX) mouse model. First, we examined ASNS expression in 38 spheroid lines and found that 12 lines (12/37, 32.4%) displayed high ASNS expression, whereas 26 lines (25/37, 67.6%) showed no ASNS expression. Next, to determine the role of asparagine metabolism in tumor growth, we established ASNS-knockdown spheroid lines using lentiviral short hairpin RNA constructs targeting ASNS. An in vitro cell proliferation assay demonstrated a significant decrease in cell proliferation upon asparagine depletion in the ASNS-knockdown spheroid lines, and this was not observed in the control spheroids lines. In addition, we examined asparagine inhibition with the anti-leukemia drug L-asparaginase (L-Asp) and observed a considerable reduction in cell proliferation at a low concentration (0.1 U/mL) in the ASNS-knockdown spheroid lines, whereas it exhibited limited inhibition of control spheroid lines at the same concentration. Finally, we used the PDSX model to assess the effects of asparagine depletion on tumor growth in vivo. The nude mice injected with ASNS-knockdown or control spheroid lines were administered with L-Asp once a day for 28 days. Surprisingly, in mice injected with ASNS-knockdown spheroids, the administration of L-Asp dramatically inhibited tumor engraftment. On the other hands, in mice injected with control spheroids, the administration of L-Asp had no effect on tumor growth inhibition at all. These results suggest that ASNS inhibition could be critical in targeting asparagine metabolism in cancers.

Anticancer Properties of N,N-dibenzylasparagine as an Asparagine (Asp) analog, Using Colon Cancer Caco-2 Cell Line.

OBJECTIVES: This study was conducted to investigate the potential anticancer properties of N, N-dibenzyl asparagine (NNDAsp), as an Asparagine (Asp) analog, using colon cancer Caco-2 cell and the normal NCM-460 cell line. METHODS: Cell viability rate and levels of produced lactate dehydrogenase (LDH) were achieved upon treatment with NNDAsp compared to Asp treatment using MTT assay and LDH production kit. The protein expression profile of asparagine synthetase (ASNS) was achieved by using ELISA and flow cytometry assay. The levels of released inflammatory cytokines, including interleukin-1 alpha (IL-1α) and IL-1 beta (IL-ß), were monitored using an ELISA assay. RESULTS: Our findings showed significant inhibition of colon cancer cell proliferation accompanied by a high level of produced LDH in a dose-dependent of an NNDAsp treatment without detectable toxic effect in normal cells. Interestingly, NNDAsp showed competitive inhibition of ASNS protein expression, in almost 3% of stained cancer cells, compared to 18% and 35% of untreated cells and cells pre-treated with Asp, respectively. Likewise, the concentration of ASNS protein was dramatically depleted in a dose and time-dependent of NNDAsp treatment in comparison with Asp treatment indicated by ELISA assay. Furthermore, as an apoptotic indicator, the expression of P53 and Caspase 3 (Caps3) was significantly increased in Caco-2 cells treated with NNDAsp at both RNA and protein levels. In contrast, their expression was markedly depleted in Asp-treated cells. In addition, the expression of both IL-1α and IL-1 ß was markedly increased in Caco-2 cells in a dose and time-dependent of NNDAsp exogenous treatment. Moreover, targeting of ASNS by the Asp analog, NNDAsp, was further confirmed by the docking analysis of inhibitors ligands and crystal structure of ASNS protein. CONCLUSION: These data provide evidence for the effectiveness of NNDAsp in cancer treatment via selective degradation of ASNS protein expression in colon cancer cells.

Tumoral microenvironment prevents de novo asparagine biosynthesis in B cell lymphoma, regardless of ASNS expression.

Depletion of circulating asparagine with l-asparaginase (ASNase) is a mainstay of leukemia treatment and is under investigation in many cancers. Expression levels of asparagine synthetase (ASNS), which catalyzes asparagine synthesis, were considered predictive of cancer cell sensitivity to ASNase treatment, a notion recently challenged. Using [U-13C5]-l-glutamine in vitro and in vivo in a mouse model of B cell lymphomas (BCLs), we demonstrated that supraphysiological or physiological concentrations of asparagine prevent de novo asparagine biosynthesis, regardless of ASNS expression levels. Overexpressing ASNS in ASNase-sensitive BCL was insufficient to confer resistance to ASNase treatment in vivo. Moreover, we showed that ASNase's glutaminase activity enables its maximal anticancer effect. Together, our results indicate that baseline ASNS expression (low or high) cannot dictate BCL dependence on de novo asparagine biosynthesis and predict BCL sensitivity to dual ASNase activity. Thus, except for ASNS-deficient cancer cells, ASNase's glutaminase activity should be considered in the clinic.

Asparagine synthetase regulates lung-cancer metastasis by stabilizing the ß-catenin complex and modulating mitochondrial response.

The availability of asparagine is the limitation of cell growth and metastasis. Asparagine synthetase (ASNS) was an essential enzyme for endogenous asparagine products. In our study, ASNS-induced asparagine products were essential to maintain tumor growth and colony formations in vitro. But mutated ASNS which defected endogenous asparagine products still upregulated cell invasiveness, which indicated that ASNS promoted invasiveness by alternative pathways. Mechanically, ASNS modulated Wnt signal transduction by promoting GSK3ß phosphorylation on ser9 and stabilizing the ß-catenin complex, as result, ASNS could promote more ß-catenin translocation into nucleus independent of endogenous asparagine. At the same time, ASNS modulated mitochondrial response to Wnt stimuli with increased mitochondrial potential and membrane fusion. In summary, ASNS promoted metastasis depending on Wnt pathway and mitochondrial functions even without endogenous asparagine products.

Amino acid stress response genes promote L-asparaginase resistance in pediatric acute lymphoblastic leukemia.

Understanding the genomic and epigenetic mechanisms of drug resistance in pediatric acute lymphoblastic leukemia (ALL) is critical for further improvements in treatment outcomes. The role of transcriptomic response in conferring resistance to l-asparaginase (LASP) is poorly understood beyond asparagine synthetase (ASNS). We defined reproducible LASP response genes in LASP-resistant and LASP-sensitive ALL cell lines as well as primary leukemia samples from newly diagnosed patients. Defining target genes of the amino acid stress response-related transcription factor activating transcription factor 4 (ATF4) in ALL cell lines using chromatin immunoprecipitation sequencing (ChIP-seq) revealed 45% of genes that changed expression after LASP treatment were direct targets of the ATF4 transcription factor, and 34% of these genes harbored LASP-responsive ATF4 promoter binding events. SLC7A11 was found to be a response gene in cell lines and patient samples as well as a direct target of ATF4. SLC7A11 was also one of only 2.4% of LASP response genes with basal level gene expression that also correlated with LASP ex vivo resistance in primary leukemia cells. Experiments using chemical inhibition of SLC7A11 with sulfasalazine, gene overexpression, and partial gene knockout recapitulated LASP resistance or sensitivity in ALL cell lines. These findings show the importance of assessing changes in gene expression following treatment with an antileukemic agent for its association with drug resistance and highlight that many response genes may not differ in their basal expression in drug-resistant leukemia cells.

An intractable epilepsy phenotype of ASNS novel mutation in two patients with asparagine synthetase deficiency.

BACKGROUND AND OBJECTIVE: Asparagine synthetase deficiency (ASNSD) is a rare neurometabolic disease caused by variations of the ASNS gene. It manifests as microcephaly, severe developmental delay, and spastic quadriplegia. 71% of ASNSD patients died during early infancy. We aim to investigate mutations related to intractable epilepsy in one Chinese genealogy. MATERIAL AND METHODS: Head Magnetic Resonance Imaging (MRI), whole exome sequencing (WES), and Liquid Chromatography-Mass Spectrometry (LC-MS) to help 2 patients with intractable epilepsy find the underlying mechanisms of disease. RESULTS: These two patients had a compound heterozygous mutation (c.224A > G, p.N75S and c.1612A > G, p.M538V) in the ASNS gene, of which c.1612A > G was a novel mutation. The asparagine levels in patients' plasmas were normal. In addition, they had a later onset, longer survival, and were milder than previously reported ASNSD patients. CONCLUSIONS: Two patients were diagnosed with a milder form of ASNSD. Clinically, the asparagine level in the patient's plasma cannot be used as the only basis to diagnose this disease. This study has expanded the disease phenotype spectrum of ASNSD and broadened the variation profile of the ASNS gene, which can assist in the clinical diagnosis and treatment of ASNSD patients.

Genome-wide expression analysis reveals involvement of asparagine synthetase family in cotton development and nitrogen metabolism.

Asparagine synthetase (ASN) is one of the key enzymes of nitrogen (N) metabolism in plants. The product of ASN is asparagine, which is one of the key compounds involved in N transport and storage in plants. Complete genome-wide analysis and classifications of the ASN gene family have recently been reported in different plants. However, little is known about the systematic analysis and expression profiling of ASN proteins in cotton development and N metabolism. Here, various bioinformatics analysis was performed to identify ASN gene family in cotton. In the cotton genome, forty-three proteins were found that determined ASN genes, comprising of 20 genes in Gossypium hirsutum (Gh), 13 genes in Gossypium arboreum, and 10 genes in Gossypium raimondii. The ASN encoded genes unequally distributed on various chromosomes with conserved glutamine amidotransferases and ASN domains. Expression analysis indicated that the majority of GhASNs were upregulated in vegetative and reproductive organs, fiber development, and N metabolism. Overall, the results provide proof of the possible role of the ASN genes in improving cotton growth, fiber development, and especially N metabolism in cotton. The identified hub genes will help to functionally elucidate the ASN genes in cotton development and N metabolism.

The edited UPF1 is correlated with elevated asparagine synthetase in pancreatic ductal adenocarcinomas.

BACKGROUND: Pancreatic ductal adenocarcinomas (PDACs) is a malignant disorder and is the most common pancreatic cancer type. The malignant cells depend on the uptake of asparagine (Asn) for growth. The synthesis of Asn occurs through the enzyme asparagine synthetase (ASNS). Interestingly, ASNS is known as is direct target of nonsense-mediated RNA decay (NMD). We have previously reported that NMD major factor UPF1 mutations in the pancreatic tumors. However, the relationship between NMD and the level of ASNS is unknown. METHOD: We constructed point mutations by site-specific mutagenesis. To evaluate NMD magnitude, we assessed the expression ratio of an exogenously expressed wild-type and mutated ß-globin mRNA with N39 allele, and five known NMD targets. Then, reverse transcription-polymerase chain reaction (RT-PCR), RT-qPCR and western bolt to determine RNA or protein levels, after knockdown of endogenous UPF1 by small RNA interference in the cells. RESULTS: An RNA editing event (c.3101 A > G) at UPF1 transcripts resulting in an Asparagine (p.1034) changed to a Serine is found in one primary PDAC patient. The edited UPF1 increases the ability of degrading of NMD provoking transcripts, such as ß-globin mRNA with N39 allele and 5 out of 5 known endogenous NMD substrate mRNAs, including ASNS. In addition, ASNS mRNA is subjected to NMD degradation by virtue of its possessing uORFs at the 5'UTR. A reduction of endogenous ASNS RNA and the increased protein expression level is found either in the PDAC patient or in the cells with edited UPF1 at c.3101 A > G relative to the controls. CONCLUSIONS: This edited UPF1 found in the PDAC results in hyperactivated NMD, which is tightly correlation to elevated expression level of ASNS. The targeting of knockdown of ASNS may improve the antitumor potency in PDACs.