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Glycosylation-deficient Chinese hamster ovary (CHO) cell lines have been instrumental in the discovery of N-glycosylation machinery. Yet, the molecular causes of the glycosylation defects in the Lec5 and Lec9 mutants have been elusive, even though for both cell lines a defect in dolichol formation from polyprenol was previously established. We recently found that dolichol synthesis from polyprenol occurs in three steps consisting of the conversion of polyprenol to polyprenal by DHRSX, the reduction of polyprenal to dolichal by SRD5A3 and the reduction of dolichal to dolichol, again by DHRSX. This led us to investigate defective dolichol synthesis in Lec5 and Lec9 cells. Both cell lines showed increased levels of polyprenol and its derivatives, concomitant with decreased levels of dolichol and derivatives, but no change in polyprenal levels, suggesting DHRSX deficiency. Accordingly, N-glycan synthesis and changes in polyisoprenoid levels were corrected by complementation with human DHRSX but not with SRD5A3. Furthermore, the typical polyprenol dehydrogenase and dolichal reductase activities of DHRSX were absent in membrane preparations derived from Lec5 and Lec9 cells, while the reduction of polyprenal to dolichal, catalyzed by SRD5A3, was unaffected. Long-read whole genome sequencing of Lec5 and Lec9 cells did not reveal mutations in the ORF of SRD5A3, but the genomic region containing DHRSX was absent. Lastly, we established the sequence of Chinese hamster DHRSX and validated that this protein has similar kinetic properties to the human enzyme. Our work therefore identifies the basis of the dolichol synthesis defect in CHO Lec5 and Lec9 cells.
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Dolichol is a lipid critical for N-glycosylation as a carrier for activated sugars and nascent oligosaccharides. It is commonly thought to be directly produced from polyprenol by the enzyme SRD5A3. Instead, we found that dolichol synthesis requires a three-step detour involving additional metabolites, where SRD5A3 catalyzes only the second reaction. The first and third steps are performed by DHRSX, whose gene resides on the pseudoautosomal regions of the X and Y chromosomes. Accordingly, we report a pseudoautosomal-recessive disease presenting as a congenital disorder of glycosylation in patients with missense variants in DHRSX (DHRSX-CDG). Of note, DHRSX has a unique dual substrate and cofactor specificity, allowing it to act as a NAD+-dependent dehydrogenase and as a NADPH-dependent reductase in two non-consecutive steps. Thus, our work reveals unexpected complexity in the terminal steps of dolichol biosynthesis. Furthermore, we provide insights into the mechanism by which dolichol metabolism defects contribute to disease.
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Dolicóis , Dolicóis/metabolismo , Dolicóis/biossíntese , Humanos , Glicosilação , 3-Oxo-5-alfa-Esteroide 4-Desidrogenase/metabolismo , 3-Oxo-5-alfa-Esteroide 4-Desidrogenase/genética , Proteínas de Membrana/metabolismo , Proteínas de Membrana/genética , Defeitos Congênitos da Glicosilação/metabolismo , Defeitos Congênitos da Glicosilação/genética , Masculino , Mutação de Sentido Incorreto , FemininoRESUMO
Investigating the function of target proteins for functional prospection or therapeutic applications typically requires the production and purification of recombinant proteins. The fusion of these proteins with tag peptides and fluorescently derived proteins allows the monitoring of candidate proteins using SDS-PAGE coupled with western blotting and fluorescent microscopy, respectively. However, protein engineering poses a significant challenge for many researchers. In this protocol, we describe step-by-step the engineering of a recombinant protein with various tags: TAT-HA (trans-activator of transduction-hemagglutinin), 6×His and EGFP (enhanced green fluorescent protein) or mCherry. Fusion proteins are produced in E. coli BL21(DE3) cells and purified by immobilized metal affinity chromatography (IMAC) using a Ni-nitrilotriacetic acid (NTA) column. Then, tagged recombinant proteins are introduced into cultured animal cells by using the penetrating peptide TAT-HA. Here, we present a thorough protocol providing a detailed guide encompassing every critical step from plasmid DNA molecular assembly to protein expression and subsequent purification and outlines the conditions necessary for protein transduction technology into animal cells in a comprehensive manner. We believe that this protocol will be a valuable resource for researchers seeking an exhaustive, step-by-step guide for the successful production and purification of recombinant proteins and their entry by transduction within living cells. © 2024 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: DNA cloning, molecular assembly strategies, and protein production Basic Protocol 2: Protein purification Basic Protocol 3: Protein transduction in mammalian cells.
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Escherichia coli , Peptídeos , Animais , Escherichia coli/genética , Proteínas Recombinantes/genética , Proteínas Recombinantes/química , Peptídeos/genética , Peptídeos/metabolismo , Indicadores e Reagentes/metabolismo , Produtos do Gene tat/metabolismo , Corantes/metabolismo , DNA/metabolismo , Mamíferos/genética , Mamíferos/metabolismoRESUMO
An accelerated de novo lipogenesis (DNL) flux is a common characteristic of cancer cells required to sustain a high proliferation rate. The DNL enzyme fatty acid synthase (FASN) is overexpressed in many cancers and is pivotal for the increased production of fatty acids. There is increasing evidences of the involvement of FASN in several hallmarks of cancer linked to its ability to promote cell proliferation via membranes biosynthesis. In this review we discuss about the implication of FASN in the resistance to cell death and in the deregulation of cellular energetics by increasing nucleic acids, protein and lipid synthesis. FASN also promotes cell proliferation, cell invasion, metastasis and angiogenesis by enabling the building of lipid rafts and consequently to the localization of oncogenic receptors such as HER2 and c-Met in membrane microdomains. Finally, FASN is involved in immune escape by repressing the activation of pro-inflammatory cells and promoting the recruitment of M2 macrophages and T regulatory cells in the tumor microenvironment. Here, we provide an overview of the involvement of the pro-oncogenic enzyme in the hallmarks of cancer making FASN a promising target in anti-cancer therapy to circumvent resistance to chemotherapies.
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The Sda carbohydrate epitope and its biosynthetic B4GALNT2 enzyme are expressed in the healthy colon and down-regulated to variable extents in colon cancer. The human B4GALNT2 gene drives the expression of a long and a short protein isoform (LF-B4GALNT2 and SF-B4GALNT2) sharing identical transmembrane and luminal domains. Both isoforms are trans-Golgi proteins and the LF-B4GALNT2 also localizes to post-Golgi vesicles thanks to its extended cytoplasmic tail. Control mechanisms underpinning Sda and B4GALNT2 expression in the gastrointestinal tract are complex and not fully understood. This study reveals the existence of two unusual N-glycosylation sites in B4GALNT2 luminal domain. The first atypical N-X-C site is evolutionarily conserved and occupied by a complex-type N-glycan. We explored the influence of this N-glycan using site-directed mutagenesis and showed that each mutant had a slightly decreased expression level, impaired stability, and reduced enzyme activity. Furthermore, we observed that the mutant SF-B4GALNT2 was partially mislocalized in the endoplasmic reticulum, whereas the mutant LF-B4GALNT2 was still localized in the Golgi and post-Golgi vesicles. Lastly, we showed that the formation of homodimers was drastically impaired in the two mutated isoforms. An AlphaFold2 model of the LF-B4GALNT2 dimer with an N-glycan on each monomer corroborated these findings and suggested that N-glycosylation of each B4GALNT2 isoform controlled their biological activity.
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Retículo Endoplasmático , Complexo de Golgi , N-Acetilgalactosaminiltransferases , Humanos , Retículo Endoplasmático/metabolismo , Glicosilação , Complexo de Golgi/metabolismo , Polissacarídeos/metabolismo , Isoformas de Proteínas/metabolismo , N-Acetilgalactosaminiltransferases/genéticaRESUMO
Free oligosaccharides (fOSs) are soluble oligosaccharide species generated during N-glycosylation of proteins. Although little is known about fOS metabolism, the recent identification of NGLY1 deficiency, a congenital disorder of deglycosylation (CDDG) caused by loss of function of an enzyme involved in fOS metabolism, has elicited increased interest in fOS processing. The catabolism of fOSs has been linked to the activity of a specific cytosolic mannosidase, MAN2C1, which cleaves α1,2-, α1,3-, and α1,6-mannose residues. In this study, we report the clinical, biochemical, and molecular features of six individuals, including two fetuses, with bi-allelic pathogenic variants in MAN2C1; the individuals are from four different families. These individuals exhibit dysmorphic facial features, congenital anomalies such as tongue hamartoma, variable degrees of intellectual disability, and brain anomalies including polymicrogyria, interhemispheric cysts, hypothalamic hamartoma, callosal anomalies, and hypoplasia of brainstem and cerebellar vermis. Complementation experiments with isogenic MAN2C1-KO HAP1 cells confirm the pathogenicity of three of the identified MAN2C1 variants. We further demonstrate that MAN2C1 variants lead to accumulation and delay in the processing of fOSs in proband-derived cells. These results emphasize the involvement of MAN2C1 in human neurodevelopmental disease and the importance of fOS catabolism.
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Cistos do Sistema Nervoso Central/genética , Defeitos Congênitos da Glicosilação/genética , Hamartoma/genética , Deficiência Intelectual/genética , Oligossacarídeos/metabolismo , Peptídeo-N4-(N-acetil-beta-glucosaminil) Asparagina Amidase/deficiência , Polimicrogiria/genética , alfa-Manosidase/genética , Adolescente , Alelos , Tronco Encefálico/metabolismo , Tronco Encefálico/patologia , Linhagem Celular Tumoral , Cistos do Sistema Nervoso Central/metabolismo , Cistos do Sistema Nervoso Central/patologia , Vermis Cerebelar/metabolismo , Vermis Cerebelar/patologia , Criança , Pré-Escolar , Defeitos Congênitos da Glicosilação/metabolismo , Defeitos Congênitos da Glicosilação/patologia , Feminino , Feto , Glicosilação , Hamartoma/metabolismo , Hamartoma/patologia , Humanos , Hipotálamo/metabolismo , Hipotálamo/patologia , Deficiência Intelectual/metabolismo , Deficiência Intelectual/patologia , Leucócitos/metabolismo , Leucócitos/patologia , Masculino , Manose/metabolismo , Peptídeo-N4-(N-acetil-beta-glucosaminil) Asparagina Amidase/genética , Peptídeo-N4-(N-acetil-beta-glucosaminil) Asparagina Amidase/metabolismo , Polimicrogiria/metabolismo , Polimicrogiria/patologia , Língua/metabolismo , Língua/patologia , alfa-Manosidase/deficiênciaRESUMO
INTRODUCTION: Chronic kidney disease (CKD) affects > 10% of the population but not all CKD patients require referral to a nephrologist. Various recommendations for referral to nephrologists are proposed worldwide. We examined the profile of French patients consulting a nephrologist for the first time and compared these characteristics with the recommendations of the International Kidney Disease: Improving Global Outcomes (KDIGO), the French "Haute Autorité de Santé" (HAS), and the Canadian Kidney Failure Risk Equation (KFRE). METHODS: University Hospital electronic medical records were used to study patients referred for consultation with a nephrologist for the first time from 2016 to 2018. Patient characteristics (age, sex, diabetic status, estimated glomerular filtration rate (eGFR) and urine protein-to-creatinine ratio (PCR), etiology reported by the nephrologist) and 1-year patient follow-up were analyzed and compared with the KDIGO, HAS and Canadian-KFRE recommendations for referral to a nephrologist. The stages were defined according to the KDIGO classification, based upon kidney function and proteinuria. RESULTS: The 1,547 included patients had a median age of 71 [61-79] years with 56% males and 37% with diabetes. The main nephropathies were vascular (40%) and glomerular (20%). The KDIGO classification revealed 30%, 47%, 19%, 4% stages G1-2 to G5, and 50%, 22%, 28% stages A1-A3, respectively. According to KDIGO, HAS and KFRE scores, nephrologist referral was indicated for 42%, 57% and 80% of patients respectively, with poor agreement between recommendations. Furthermore, we observed 890 (57%) patients with an eGFR> 30 ml/min and a urine protein to creatinine ratio 0.5 g/g, mostly aged over 65 years (67%); 40% were diabetic, and 57% had a eGFR > 45 ml/min/1.73m2, 56% were diagnosed as vascular nephropathy and 11% with unknown nephropathy. CONCLUSION: These results underline the importance of better identifying patients for referral to a nephrologist and informing general practitioners. Other referral criteria (age and etiology of the nephropathy) are debatable.
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Falência Renal Crônica , Insuficiência Renal Crônica , Idoso , Canadá , Creatinina/urina , Feminino , Taxa de Filtração Glomerular , Humanos , Falência Renal Crônica/epidemiologia , Masculino , Pessoa de Meia-Idade , Nefrologistas , Pacientes Ambulatoriais , Encaminhamento e Consulta , Insuficiência Renal Crônica/complicações , Insuficiência Renal Crônica/diagnóstico , Insuficiência Renal Crônica/terapiaRESUMO
Alteration of O-GlcNAcylation, a dynamic posttranslational modification, is associated with tumorigenesis and tumor progression. Its role in chemotherapy response is poorly investigated. Standard treatment for colorectal cancer (CRC), 5-fluorouracil (5-FU), mainly targets Thymidylate Synthase (TS). TS O-GlcNAcylation was reported but not investigated yet. We hypothesize that O-GlcNAcylation interferes with 5-FU CRC sensitivity by regulating TS. In vivo, we observed that combined 5-FU with Thiamet-G (O-GlcNAcase (OGA) inhibitor) treatment had a synergistic inhibitory effect on grade and tumor progression. 5-FU decreased O-GlcNAcylation and, reciprocally, elevation of O-GlcNAcylation was associated with TS increase. In vitro in non-cancerous and cancerous colon cells, we showed that 5-FU impacts O-GlcNAcylation by decreasing O-GlcNAc Transferase (OGT) expression both at mRNA and protein levels. Reciprocally, OGT knockdown decreased 5-FU-induced cancer cell apoptosis by reducing TS protein level and activity. Mass spectrometry, mutagenesis and structural studies mapped O-GlcNAcylated sites on T251 and T306 residues and deciphered their role in TS proteasomal degradation. We reveal a crosstalk between O-GlcNAcylation and 5-FU metabolism in vitro and in vivo that converges to 5-FU CRC sensitization by stabilizing TS. Overall, our data propose that combining 5-FU-based chemotherapy with Thiamet-G could be a new way to enhance CRC response to 5-FU.
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Timidilato SintaseRESUMO
The HER2 receptor and its MUC4 mucin partner form an oncogenic complex via an extracellular region of MUC4 encompassing three EGF domains that promotes tumor progression of pancreatic cancer (PC) cells. However, the molecular mechanism of interaction remains poorly understood. Herein, we decipher at the molecular level the role and impact of the MUC4EGF domains in the mediation of the binding affinities with HER2 and the PC cell tumorigenicity. We used an integrative approach combining in vitro bioinformatic, biophysical, biochemical, and biological approaches, as well as an in vivo study on a xenograft model of PC. In this study, we specified the binding mode of MUC4EGF domains with HER2 and demonstrate their "growth factor-like" biological activities in PC cells leading to stimulation of several signaling proteins (mTOR pathway, Akt, and ß-catenin) contributing to PC progression. Molecular dynamics simulations of the MUC4EGF/HER2 complexes led to 3D homology models and identification of binding hotspots mediating binding affinity with HER2 and PC cell proliferation. These results will pave the way to the design of potential MUC4/HER2 inhibitors targeting the EGF domains of MUC4. This strategy will represent a new efficient alternative to treat cancers associated with MUC4/HER2 overexpression and HER2-targeted therapy failure as a new adapted treatment to patients.
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BACKGROUND: The Sda antigen and corresponding biosynthetic enzyme B4GALNT2 are primarily expressed in normal colonic mucosa and are down-regulated to a variable degree in colon cancer tissues. Although their expression profile is well studied, little is known about the underlying regulatory mechanisms. METHODS: To clarify the molecular basis of Sda expression in the human gastrointestinal tract, we investigated the transcriptional regulation of the human B4GALNT2 gene. The proximal promoter region was delineated using luciferase assays and essential trans-acting factors were identified through transient overexpression and silencing of several transcription factors. RESULTS: A short cis-regulatory region restricted to the -72 to +12 area upstream of the B4GALNT2 short-type transcript variant contained the essential promoter activity that drives the expression of the human B4GALNT2 regardless of the cell type. We further showed that B4GALNT2 transcriptional activation mostly requires ETS1 and to a lesser extent SP1. CONCLUSIONS: Results presented herein are expected to provide clues to better understand B4GALNT2 regulatory mechanisms.
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N-Acetilgalactosaminiltransferases/genética , Proteína Proto-Oncogênica c-ets-1/metabolismo , Colo , Células HT29 , Humanos , Mucosa Intestinal , N-Acetilgalactosaminiltransferases/metabolismo , Oligossacarídeos/biossíntese , Regiões Promotoras Genéticas , Fator de Transcrição Sp1/metabolismo , Ativação TranscricionalRESUMO
The Sda carbohydrate antigen and the corresponding biosynthetic enzyme B4GALNT2 are primarily expressed in human normal colonic mucosa and are down-regulated to variable degrees in colon cancer. On the other hand, the tumor associated antigen SLex is not detected in the healthy colon and is upregulated in colon cancer. High level of B4GALNT2 gene expression appears to be a good marker of prognosis in colon cancer; however, the molecular mechanisms regulating these carbohydrate antigens' expression are still poorly understood. We review here the most recent progress made towards understanding this balanced expression of blood group carbohydrate epitopes Sda and SLex . In particular in recent years, we have attained a better understanding of genetic and epigenetic regulation of the B4GALNT2 gene and of the subcellular fate of B4GALNT2 isoforms.
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Colo/metabolismo , Neoplasias do Colo/metabolismo , N-Acetilgalactosaminiltransferases/metabolismo , Oligossacarídeos/biossíntese , Antígeno Sialil Lewis X/biossíntese , Neoplasias do Colo/diagnóstico , Humanos , PrognósticoRESUMO
Fatty acid synthase (FASN) participates in many fundamental biological processes, including energy storage and signal transduction, and is overexpressed in many cancer cells. We previously showed in a context of lipogenesis that FASN is protected from degradation by its interaction with O-GlcNAc transferase (OGT) in a nutrient-dependent manner. We and others also reported that OGT and O-GlcNAcylation up-regulate the PI3K/AKT/mTOR pathway that senses mitogenic signals and nutrient availability to drive cell cycle. Using biochemical and microscopy approaches, we show here that FASN co-localizes with OGT in the cytoplasm and, to a lesser extent, in the membrane fraction. This interaction occurs in a cell cycle-dependent manner, following the pattern of FASN expression. Moreover, we show that FASN expression depends on OGT upon serum stimulation. The level of FASN also correlates with the activation of the PI3K/AKT/mTOR pathway in hepatic cell lines, and in livers of obese mice and in a chronically activated insulin and mTOR signaling mouse model (PTEN-null mice). These results indicate that FASN is under a dual control of O-GlcNAcylation and mTOR pathways. In turn, blocking FASN with the small-molecule inhibitor C75 reduces both OGT and O-GlcNAcylation levels, and mTOR activation, highlighting a novel reciprocal regulation between these actors. In addition to the role of O-GlcNAcylation in tumorigenesis, our findings shed new light on how aberrant activity of FASN and mTOR signaling may promote the emergence of hepatic tumors.
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Biomarcadores Tumorais/metabolismo , Carcinoma Hepatocelular/patologia , Ácido Graxo Sintase Tipo I/metabolismo , Neoplasias Hepáticas/patologia , N-Acetilglucosaminiltransferases/metabolismo , Animais , Apoptose , Biomarcadores Tumorais/genética , Carcinoma Hepatocelular/genética , Carcinoma Hepatocelular/metabolismo , Proliferação de Células , Ácido Graxo Sintase Tipo I/genética , Regulação Neoplásica da Expressão Gênica , Humanos , Neoplasias Hepáticas/genética , Neoplasias Hepáticas/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Obesos , N-Acetilglucosaminiltransferases/genética , Serina-Treonina Quinases TOR/genética , Serina-Treonina Quinases TOR/metabolismo , Células Tumorais Cultivadas , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Colorectal cancer (CRC) affects both women and men living in societies with a high sedentary lifestyle. Amongst the phenotypic changes exhibited by tumor cells, a wide range of glycosylation has been reported for colon cancer-derived cell lines and CRC tissues. These aberrant modifications affect different aspects of glycosylation, including an increase in core fucosylation and GlcNAc branching on N-glycans, alteration of O-glycans, upregulated sialylation, and O-GlcNAcylation. Although O-GlcNAcylation and complex glycosylations differ in many aspects, sparse evidences report on the interference of O-GlcNAcylation with complex glycosylation. Nevertheless, this relationship is still a matter of debate. Combining different approaches on three human colon cell lines (HT29, HCT116 and CCD841CoN), it is herein reported that silencing O-GlcNAc transferase (OGT, the sole enzyme driving O-GlcNAcylation), only slightly affects overall N- and O-glycosylation patterns. Interestingly, silencing of OGT in HT29 cells upregulates E-cadherin (a major actor of epithelial-to-mesenchymal transition) and changes its glycosylation. On the other hand, OGT silencing perturbs biosynthesis of glycosphingolipids resulting in a decrease in gangliosides and an increase in globosides. Together, these results provide novel insights regarding the selective regulation of complex glycosylations by O-GlcNAcylation in colon cancer cells.
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Caderinas/genética , Neoplasias Colorretais/genética , N-Acetilglucosaminiltransferases/genética , Neoplasias Colorretais/patologia , Transição Epitelial-Mesenquimal/genética , Regulação Neoplásica da Expressão Gênica/genética , Inativação Gênica , Glicoesfingolipídeos/biossíntese , Glicoesfingolipídeos/genética , Glicosilação , Células HCT116 , Células HT29 , Humanos , Polissacarídeos/genéticaRESUMO
Cyclin D1 is the regulatory partner of the cyclin-dependent kinases (CDKs) CDK4 or CDK6. Once associated and activated, the cyclin D1/CDK complexes drive the cell cycle entry and G1 phase progression in response to extracellular signals. To ensure their timely and accurate activation during cell cycle progression, cyclin D1 turnover is finely controlled by phosphorylation and ubiquitination. Here we show that the dynamic and reversible O-linked ß-N-Acetyl-glucosaminylation (O-GlcNAcylation) regulates also cyclin D1 half-life. High O-GlcNAc levels increase the stability of cyclin D1, while reduction of O-GlcNAcylation strongly decreases it. Moreover, elevation of O-GlcNAc levels through O-GlcNAcase (OGA) inhibition significantly slows down the ubiquitination of cyclin D1. Finally, biochemical and cell imaging experiments in human cancer cells reveal that the O-GlcNAc transferase (OGT) binds to and glycosylates cyclin D1. We conclude that O-GlcNAcylation promotes the stability of cyclin D1 through modulating its ubiquitination.
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O-GlcNAcylation of proteins is governed by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). The homeostasis of O-GlcNAc cycling is regulated during cell cycle progression and is essential for proper cellular division. We previously reported the O-GlcNAcylation of the minichromosome maintenance proteins MCM2, MCM3, MCM6 and MCM7. These proteins belong to the MCM2-7 complex which is crucial for the initiation of DNA replication through its DNA helicase activity. Here we show that the six subunits of MCM2-7 are O-GlcNAcylated and that O-GlcNAcylation of MCM proteins mainly occurs in the chromatin-bound fraction of synchronized human cells. Moreover, we identify stable interaction between OGT and several MCM subunits. We also show that down-regulation of OGT decreases the chromatin binding of MCM2, MCM6 and MCM7 without affecting their steady-state level. Finally, OGT silencing or OGA inhibition destabilizes MCM2/6 and MCM4/7 interactions in the chromatin-enriched fraction. In conclusion, OGT is a new partner of the MCM2-7 complex and O-GlcNAcylation homeostasis might regulate MCM2-7 complex by regulating the chromatin loading of MCM6 and MCM7 and stabilizing MCM/MCM interactions.
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Cromatina/genética , Inativação Gênica , Proteínas de Manutenção de Minicromossomo/genética , N-Acetilglucosaminiltransferases/genética , Western Blotting , Linhagem Celular Tumoral , Cromatina/metabolismo , Glicosilação , Células HEK293 , Humanos , Células MCF-7 , Proteínas de Manutenção de Minicromossomo/metabolismo , N-Acetilglucosaminiltransferases/metabolismo , Ligação Proteica , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Subunidades Proteicas/genética , Subunidades Proteicas/metabolismo , beta-N-Acetil-Hexosaminidases/genética , beta-N-Acetil-Hexosaminidases/metabolismoRESUMO
Pancreatic adenocarcinoma (PDAC) is one of the most deadly cancers in the Western world because of a lack of early diagnostic markers and efficient therapeutics. At the time of diagnosis, more than 80% of patients have metastasis or locally advanced cancer and are therefore not eligible for surgical resection. Pancreatic cancer cells also harbour a high resistance to chemotherapeutic drugs such as gemcitabine that is one of the main palliative treatments for PDAC. Proteins involved in TGF-ß signaling pathway (SMAD4 or TGF-ßRII) are frequently mutated in PDAC (50â»80%). TGF-ß signalling pathway plays antagonistic roles during carcinogenesis by initially inhibiting epithelial growth and later promoting the progression of advanced tumors and thus emerged as both tumor suppressor and oncogenic pathways. In order to decipher the role of TGF-ß in pancreatic carcinogenesis and chemoresistance, we generated CAPAN-1 and CAPAN-2 cell lines knocked down for TGF-ßRII (first actor of TGF-ß signaling). The impact on biological properties of these TGF-ßRII-KD cells was studied both in vitro and in vivo. We show that TGF-ßRII silencing alters tumor growth and migration as well as resistance to gemcitabine. TGF-ßRII silencing also leads to S727 STAT3 and S63 c-Jun phosphorylation, decrease of MRP3 and increase of MRP4 ABC transporter expression and induction of a partial EMT phenotype. These markers associated with TGF-ß signaling pathways may thus appear as potent therapeutic tools to better treat/manage pancreatic cancer.
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The Sda /Cad antigen reported on glycoconjugates of human tissues has an increasingly recognized wide impact on the physio-pathology of different biological systems. The last step of its biosynthesis relies on the enzymatic activity of the ß1,4-N-acetylgalactosaminyltransferase-II (B4GALNT2), which shows the highest expression level in healthy colon. Previous studies reported the occurrence in human colonic cells of two B4GALNT2 protein isoforms that differ in the length of their cytoplasmic tail, the long isoform showing an extended 66-amino acid tail. We examined here, the subcellular distribution of the two B4GALNT2 protein isoforms in stably transfected colonic LS174T cells and in transiently transfected HeLa cells using fluorescence microscopy. While a similar subcellular distribution at the trans-Golgi cisternae level was observed for the two isoforms, our study pointed to an atypical subcellular localization of the long B4GALNT2 isoform into dynamic vesicles. We demonstrated a critical role of its extended cytoplasmic tail for its Golgi targeting and post-Golgi sorting and highlighted the existence of a newly described post-Golgi sorting signal as well as a previously undescribed fate of a Golgi glycosyltransferase. DATABASE: The proteins ß1,4GalNAcT II, ß1,4-GalT1, FucT I, FucT VI and ST3Gal IV are noted B4GALNT2, B4GALT1, FUT1, FUT6 and ST3GAL4, whereas the corresponding human genes are noted B4GALNT2, B4GALT1, FUT1, FUT6 and ST3GAL4 according to the HUGO nomenclature.
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Neoplasias do Colo/metabolismo , Complexo de Golgi/metabolismo , N-Acetilgalactosaminiltransferases/metabolismo , Frações Subcelulares/metabolismo , Sequência de Aminoácidos , Neoplasias do Colo/patologia , Células HeLa , Humanos , Isoformas de Proteínas , Transporte Proteico , Homologia de Sequência , Células Tumorais CultivadasRESUMO
PURPOSE: Cancer cells often elicit a higher glycolytic rate than normal cells, supporting the development of glycolysis inhibitors as therapeutic agents. 2-Deoxyglucose (2-DG) is used in this context due to its ability to compete with glucose. However, many studies do not take into account that 2-DG inhibits not only glycolysis but also N-glycosylation. Since there are limited publications on 2-DG mechanism of action in breast cancer, we studied its effects in breast cancer cell lines to determine the part played by glycolysis inhibition and N-linked glycosylation interference. METHODS AND RESULTS: 2-Deoxyglucose behaved as an anticancer agent with a similar efficiency on cell number decrease between the hormone-dependent MCF-7 and hormone-independent MDA-MB-231 breast cancer cells. It also interfered with the N-linked glycosylation process in both cell lines as illustrated by the migration profile of the lysosomal-associated membrane protein 2 and calumenin. These results are reinforced by the appearance of an abnormal Man7GlcNAc2 structure both on lipid-linked oligosaccharides and N-linked glycoproteins of 2-DG incubated MDA-MB-231 cells. Besides, 2-DG-induced a transient endoplasmic reticulum stress that was more sustained in MDA-MB-231 cells. Both changes were abrogated by mannose. 2-DG, even in the presence of mannose, decreased glycolysis in both cell lines. Mannose partially reversed the effects of 2-DG on cell numbers with N-linked glycosylation interference accounting for 37 and 47% of 2-DG anti-cancerous effects in MDA-MB-231 and MCF-7 cells, respectively. CONCLUSION: N-linked glycosylation interference and glycolysis disruption both contribute to the anticancer properties of 2-DG in breast cancer cells.
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Neoplasias da Mama/tratamento farmacológico , Desoxiglucose/farmacologia , Glicólise/efeitos dos fármacos , Glicosilação/efeitos dos fármacos , Apoptose/efeitos dos fármacos , Neoplasias da Mama/metabolismo , Neoplasias da Mama/patologia , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Feminino , Glucose/metabolismo , Glicoproteínas/antagonistas & inibidores , Glicoproteínas/química , Humanos , Células MCF-7RESUMO
Since its cloning a decade ago, TRPM8 channel has emerged as a promising prognostic marker and a putative therapeutic target in prostate cancer (PCa). However, recent studies have brought to light the complexity of TRPM8 isoforms in PCa. Consequently, the respective role of each TRPM8 isoform needs to be deciphered prior to considering TRPM8 as an attractive therapeutic target. Full-length (6 transmembrane (TM)-domain) TRPM8 channel is overexpressed in early PCa and repressed in advanced prostate tumors whereas the localization of the truncated, 4TM-TRPM8 channel (4 transmembrane (TM)-domain), in the membranes of endoplasmic reticulum (ER) is independent of the pathogenic status of epithelial cells. In the same line, expression of non-channel cytoplasmic small TRPM8 isoforms (namely sM8) is conserved in cancer cells. In this study, we identify sM8s as putative regulator of PCa cell death. Indeed, suppression of sM8 isoforms was found to induce concomitantly ER stress, oxidative stress, p21 expression and apoptosis in human epithelial prostate cancer cells. We furthermore demonstrate that induction of such mechanisms required the activity of 4TM-TRPM8 channels at the ER-mitochondria junction. Our study thus suggests that targeting sM8 could be an appropriate strategy to fight prostate cancer.
Assuntos
Neoplasias da Próstata/patologia , Canais de Cátion TRPM/metabolismo , Animais , Apoptose/fisiologia , Linhagem Celular Tumoral , Feminino , Xenoenxertos , Humanos , Masculino , Camundongos , Camundongos Nus , Neoplasias da Próstata/metabolismo , Isoformas de Proteínas/metabolismoRESUMO
Nuclear all-trans retinoic acid receptors (RARs) initiate early transcriptional events which engage pluripotent cells to differentiate into specific lineages. RAR-controlled transactivation depends mostly on agonist-induced structural transitions in RAR C-terminus (AF-2), thus bridging coactivators or corepressors to chromatin, hence controlling preinitiation complex assembly. However, the contribution of other domains of RAR to its overall transcriptional activity remains poorly defined. A proteomic characterization of nuclear proteins interacting with RAR regions distinct from the AF-2 revealed unsuspected functional properties of the RAR N-terminus. Indeed, mass spectrometry fingerprinting identified the Bromodomain-containing protein 4 (BRD4) and ALL1-fused gene from chromosome 9 (AF9/MLLT3), known to associate with and regulates the activity of Positive Transcription Elongation Factor b (P-TEFb), as novel RAR coactivators. In addition to promoter sequences, RAR binds to genomic, transcribed regions of retinoid-regulated genes, in association with RNA polymerase II and as a function of P-TEFb activity. Knockdown of either AF9 or BRD4 expression affected differentially the neural differentiation of stem cell-like P19 cells. Clusters of retinoid-regulated genes were selectively dependent on BRD4 and/or AF9 expression, which correlated with RAR association to transcribed regions. Thus RAR establishes physical and functional links with components of the elongation complex, enabling the rapid retinoid-induced induction of genes required for neuronal differentiation. Our data thereby extends the previously known RAR interactome from classical transcriptional modulators to components of the elongation machinery, and unravel a functional role of RAR in transcriptional elongation.