Sialylation, or the covalent addition of sialic acid to the terminal end of glycoproteins, is a biologically important modification that is involved in embryonic development, neurodevelopment, reprogramming, oncogenes...Sialylation, or the covalent addition of sialic acid to the terminal end of glycoproteins, is a biologically important modification that is involved in embryonic development, neurodevelopment, reprogramming, oncogenesis and immune responses. In this review, we have given a comprehensive overview of the current literature on the involvement of sialylation in cell fate decision during development, reprogramming and cancer progressionSialylation is essential for early embryonic development and the deletion of UDP-GIcNAc 2-epimerase, a rate-limiting enzyme in sialic acid biosynthesis, is embryonically lethal. Furthermore, the sialyltransferase ST6GAL1 is required for somatic cell reprogramming, and its downregulation is associated with decreased reprogramming efficiency. In addition, sialylation levels and patterns are altered during cancer progression, indicating the potential of sialylated molecules as cancer biomarkers. Taken together, the current evidences demonstrate that sialylation is involved in crucial cell fate decision.展开更多
Sialylated N-glycan isomers withα2-3 orα2-6 linkage(s)have distinctive roles in glycoproteins,but are difficult to distinguish.Wild-type(WT)and glycoengineered(mutant)therapeutic glycoproteins,cytotoxic T lymphocyte...Sialylated N-glycan isomers withα2-3 orα2-6 linkage(s)have distinctive roles in glycoproteins,but are difficult to distinguish.Wild-type(WT)and glycoengineered(mutant)therapeutic glycoproteins,cytotoxic T lymphocyte-associated antigen-4-immunoglobulin(CTLA4-Ig),were produced in Chinese hamster ovary cell lines;however,their linkage isomers have not been reported.In this study,N-glycans of CTLA4-Igs were released,labeled with procainamide,and analyzed by liquid chromatography-tandem mass spectrometry(MS/MS)to identify and quantify sialylated N-glycan linkage isomers.The linkage isomers were distinguished by comparison of 1)intensity of the N-acetylglucosamine ion to the sialic acid ion(Ln/Nn)using different fragmentation stability in MS/MS spectra and 2)retention time-shift for a selective m/z value in the extracted ion chromatogram.Each isomer was distinctively identified,and each quantity(>0.1%)was obtained relative to the total N-glycans(100%)for all observed ionization states.Twenty sialylated N-glycan isomers with onlyα2-3 linkage(s)in WT were identified,and each isomer's sum of quantities was 50.4%.Furthermore,39 sialylated N-glycan isomers(58.8%)in mono-(3 N-glycans;0.9%),bi-(18;48.3%),tri-(14;8.9%),and tetra-(4;0.7%)antennary structures of mutant were obtained,which comprised mono-(15 N-glycans;25.4%),di-(15;28.4%),tri-(8;4.8%),and tetra-(1;0.2%)sialylation,respectively,with onlyα2-3(10 N-glycans;4.8%),bothα2-3 andα2-6(14;18.4%),and onlyα2-6(15;35.6%)linkage(s).These results are consistent with those forα2-3 neuraminidase-treated N-glycans.This study generated a novel plot of Ln/Nn versus retention time to distinguish sialylated N-glycan linkage isomers in glycoprotein.展开更多
Malignant tumors are complex structures composed of cancer cells and tumor microenvironmental cells.In this complex structure,cells cross-talk and interact,thus jointly promoting cancer development and metastasis.Rece...Malignant tumors are complex structures composed of cancer cells and tumor microenvironmental cells.In this complex structure,cells cross-talk and interact,thus jointly promoting cancer development and metastasis.Recently,immunoregulatory molecule-based cancer immunotherapy has greatly improved treatment efficacy for solid cancers,thus enabling some patients to achieve persistent responses or cure.However,owing to the development of drug-resistance and the low response rate,immunotherapy against the available targets PD-1/PD-L1 or CTLA-4 has limited benefits.Although combination therapies have been proposed to enhance the response rate,severe adverse effects are observed.Thus,alternative immune checkpoints must be identified.The SIGLECs are a family of immunoregulatory receptors(known as glyco-immune checkpoints)discovered in recent years.This review systematically describes the molecular characteristics of the SIGLECs,and discusses recent progress in areas including synthetic ligands,monoclonal antibody inhibitors,and Chimeric antigen receptor T(CAR-T)cells,with a focus on available strategies for blocking the sialylated glycan-SIGLEC axis.Targeting glyco-immune checkpoints can expand the scope of immune checkpoints and provide multiple options for new drug development.展开更多
Neurodegenerative diseases are often associated with the accumulation of oxidative stress and neuroinflammation.Edible bird’s nest(EBN)is a glycoprotein(sialylated mucin glycopeptides)found to be beneficial against n...Neurodegenerative diseases are often associated with the accumulation of oxidative stress and neuroinflammation.Edible bird’s nest(EBN)is a glycoprotein(sialylated mucin glycopeptides)found to be beneficial against neurodegenerative diseases.Antioxidative,anti-inflammatory,and anti-apoptotic properties of EBN in preserving neuronal cells were widely researched using in vitro and in vivo models.Functional effects of EBN are often linked to its great number of antioxidants and anti-inflammatory glycopeptides.Bioactive compounds in EBN,especially sialic acid,add value to neurotrophic potential of EBN and contribute to neuronal repair and protection.Various studies reporting the neuroprotective effects of EBN,their molecular mechanisms,and neuroactive composition were gathered in this review to provide better insights on the neuroprotective effects of EBN.展开更多
目的:了解P-选择素及其配体sLeA、sLeX在食管癌组织及区域淋巴结中的表达,探讨其与食管癌侵袭转移的关系。方法:应用组织芯片技术结合免疫组化检测食管鳞癌86例及其淋巴结P-选择素和sialy lewis A(sLeA)、sialylewis X(sLe X)的表达情况...目的:了解P-选择素及其配体sLeA、sLeX在食管癌组织及区域淋巴结中的表达,探讨其与食管癌侵袭转移的关系。方法:应用组织芯片技术结合免疫组化检测食管鳞癌86例及其淋巴结P-选择素和sialy lewis A(sLeA)、sialylewis X(sLe X)的表达情况,并与16例正常食管鳞状上皮对照。结果:P-选择素在食管癌组织、正常食管鳞状上皮表达率分别为59.3%、12.5%(P<0.05),在转移淋巴结、非转移淋巴结中表达率分别为92.9%、31.3%(P<0.05)。sLeA在食管癌组织,正常食管组织中表达率分别为77.9%、6.25%(P<0.05),在转移淋巴结和非转移淋巴结中表达率分别为97.6%、20.3%(P<0.05)。sLe X食管癌组织、正常食管组织中表达率分别为15.1%、6.25%(P>0.05)。P-选择素和配体sLeA过度表达与食管鳞癌病理分级,TNM分期及淋巴结转移成显著相关性;而配体sLeX在食管癌组织中无过度表达。结论:P-选择素和配体sLeA在食管鳞癌组织、转移淋巴结中表达率明显升高,其与食管癌的侵袭转移有一定关系;配体sLeX与食管癌侵袭转移无关。展开更多
目的探讨大肠腺癌组织粘蛋白MUC2和sialyl lewis X(sLex)的分型与临床各个病理参数之间的关系。方法应用免疫组织化学双染法对34例远切端大肠黏膜、18例大肠腺瘤及55例大肠腺癌组织进行粘蛋白MUC2、sLex检测。结果远切端大肠黏膜、大肠...目的探讨大肠腺癌组织粘蛋白MUC2和sialyl lewis X(sLex)的分型与临床各个病理参数之间的关系。方法应用免疫组织化学双染法对34例远切端大肠黏膜、18例大肠腺瘤及55例大肠腺癌组织进行粘蛋白MUC2、sLex检测。结果远切端大肠黏膜、大肠腺瘤及大肠腺癌中,黏蛋白MUC2阳性表达率分别为100%、94.4%和58.2%(P<0.01);sLex阳性表达率分别为5.9%、50.0%和80.0%(P<0.05)。根据MUC2和sLex在大肠腺癌中的表达把大肠腺癌分为四型:MUC2+/sLex+、MUC2+/sLex-、MUC2-/sLex+、MUC2-/sLex-。MUC2+/sLex+型与患者的性别具有相关性;MUC2+/sLex-型与淋巴结转移、Duke’s分期具有相关性;MUC2-/sLex+型与发生部位、分化程度具有相关性;MUC2-/sLex-型与大肠腺癌临床病理参数均不具有相关性。结论 MUC2的下调表达或sLex的上调表达可能参与了大肠肿瘤的发生及恶性转化,各型大肠腺癌不同程度与其分化、生物学行为相关,对临床上判断预后具有较大的意义。展开更多
The sialyl Lewis X（SLe;） antigen encoded by the FUT7 gene is the ligand of endotheliam-selectin（E-selectin）. The combination of SLe;antigen and E-selectin represents an important way for malignant tumor metastasis...The sialyl Lewis X（SLe;） antigen encoded by the FUT7 gene is the ligand of endotheliam-selectin（E-selectin）. The combination of SLe;antigen and E-selectin represents an important way for malignant tumor metastasis. In the present study, the effect of the SLe;-binding DNA aptamer on the adhesion and metastasis of hepatocellular carcinoma HepG2 cells in vitro was investigated. Reverse transcription-polymerase chain reaction（RT-PCR） and immunofluorescence staining were conducted to detect the expression of FUT7 at both transcriptional and translational levels. The SLe;expression in HepG2 cells treated with different concentrations of SLe;-binding DNA aptamer was detected by flow cytometry. Besides, the adhesion, migration, and invasion of HepG2 cells were measured by cell adhesion assay, and the Transwell migration and invasion assay. The results showed that the FUT7 expression was up-regulated at both mR NA and protein levels in HepG2 cells. SLe;-binding DNA aptamer could significantly decrease the expression of SLe;in HepG2 cells. The cell adhesion assay revealed that the SLe;-binding DNA aptamer could effectively inhibit the interactions between E-selectin and SLe;in the HepG2 cells. Additionally, SLe;-binding DNA aptamers at 20 nmol/L were found to have the similar effect to the monoclonal antibody CSLEX-1. The Transwell migration and invasion assay revealed that the number of penetrating cells on the down-side of Transwell membrane was significantly less in cells treated with 5, 10, 20 nmol/L SLe;-binding DNA aptamer than those in the negative control group（P<0.01）. Our study demonstrated that the SLe;-binding DNA aptamer could significantly inhibit the in vitro adhesion, migration, and invasion of HepG2 cells, suggesting that the SLe;-binding DNA aptamer may be used as a potential molecular targeted drug against metastatic hepatocellular carcinoma.展开更多
An efficient enzymatic assembly strategy was developed for the concise synthesis of structurally well-defined sialylated chitooligosaccharides.Two enzyme modules for theβ-1,3-N-acetyl-glucosaminylation andβ-1,4-gala...An efficient enzymatic assembly strategy was developed for the concise synthesis of structurally well-defined sialylated chitooligosaccharides.Two enzyme modules for theβ-1,3-N-acetyl-glucosaminylation andβ-1,4-galactosylation were applied for the grafting N-acetyl lactosamine(LacNAc)unit(s)onto the chitooligosaccharides.The LacNAc grafted chitooligosaccharides were further modified withα-2,3-orα-2,6-sialylation by two enzymatic sialylation modules to generate a total of 20 sialylated chitooligosaccharides.The inhibition study of influenza virus-induced cytopathy with synthetic sialylated chitooligosaccharides indicated that the sialic acid linkage and chain length both contribute to the binding preference and inhibition potency.展开更多
Sialylation of glycoproteins is vital for the function or physicochemical properties of a protein. It becomes more and more important to develop approaches that can be used to efficiently isolate and identify sialylat...Sialylation of glycoproteins is vital for the function or physicochemical properties of a protein. It becomes more and more important to develop approaches that can be used to efficiently isolate and identify sialylated glycopep- tides or glycoproteins for monitoring changes in glycoproteome. In the present study, we analyze intact structures of the enriched sialylated glycopeptides of bovine fetuin by matrix-assisted laser desorption/ionization-tandem mass spectrometry （MALDI-MS/MS）, without any chemical derivation. The experimental data show that the optimal loading buffer for TiO2 as matrix is 80% acetonitrile/2% TFA （trifluoroacetic acid）/100 mg/mL DHB （2,5-dihydroxybenzoic acid） which is also compatible with MALDI-mass spectrometric analysis. This study indi- cates that the improved enrichment approach combined with MALDI-MS/MS may be a powerful tool to analyze intact structures and components of the sialylated glycopeptides from complex peptide mixture.展开更多
E-selectin is a cell-adhesion molecule of the vascular endothelium that promotes essential leukocyte rolling in the early inflammatory response by binding to glycoproteins containing the tetrasaccharide sialyl Lewisx(...E-selectin is a cell-adhesion molecule of the vascular endothelium that promotes essential leukocyte rolling in the early inflammatory response by binding to glycoproteins containing the tetrasaccharide sialyl Lewisx(sLex).Efficient leukocyte recruitment under vascular flow conditions depends on an increased lifetime of E-selectin/ligand complexes under tensile force in a so-called catch-bond binding mode.Co-crystal structures of a representative fragment of the extracellular E-selectin region with sLex and a glycomimetic antagonist thereof reveal an extended E-selectin conformation,which is identified as a high-affinity binding state of E-selectin by molecular dynamics simulations.Small-angle X-ray scattering experiments demonstrate a direct link between ligand binding and E-selectin conformational transition under static conditions in solution.This permits tracing a series of concerted structural changes connecting ligand binding to conformational stretching as the structural basis of E-selectin catch-bond-mediated leukocyte recruitment.The detailed molecular view of the binding site paves the way for the design of a new generation of selectin antagonists.This is of special interest,since their therapeutic potentialwas recently demonstrated with the pan-selectin antagonists GMI-1070(Rivipansel).展开更多
基金National Key Research and Development Program 2016YFA (0101700) and 2017YFA0102800the National Natural Science Foundation of China (Grant Nos. 31771639 and 81703086)+3 种基金Guangdong Innovative and Entrepreneurial Research Team Program 2016ZT06S029the Fundamental Research Funds for the Central Universities (17ykzd04)Thousand Youth Talents Plan to J. Ding and J. W., the National Natural Science Foundation of China (Grant No. 31771)a project funded by China Postdoctoral Science Foundation (2017M622863).
文摘Sialylation, or the covalent addition of sialic acid to the terminal end of glycoproteins, is a biologically important modification that is involved in embryonic development, neurodevelopment, reprogramming, oncogenesis and immune responses. In this review, we have given a comprehensive overview of the current literature on the involvement of sialylation in cell fate decision during development, reprogramming and cancer progressionSialylation is essential for early embryonic development and the deletion of UDP-GIcNAc 2-epimerase, a rate-limiting enzyme in sialic acid biosynthesis, is embryonically lethal. Furthermore, the sialyltransferase ST6GAL1 is required for somatic cell reprogramming, and its downregulation is associated with decreased reprogramming efficiency. In addition, sialylation levels and patterns are altered during cancer progression, indicating the potential of sialylated molecules as cancer biomarkers. Taken together, the current evidences demonstrate that sialylation is involved in crucial cell fate decision.
基金supported by the Basic Science Research Program through the National Research Foundation of Korea(NRF)and funded by the Ministry of Education,Korea(Grant No.:2021R1A6A1A03044296)This study was supported by the Chung-Ang University Graduate Research Scholarship in 2022.
文摘Sialylated N-glycan isomers withα2-3 orα2-6 linkage(s)have distinctive roles in glycoproteins,but are difficult to distinguish.Wild-type(WT)and glycoengineered(mutant)therapeutic glycoproteins,cytotoxic T lymphocyte-associated antigen-4-immunoglobulin(CTLA4-Ig),were produced in Chinese hamster ovary cell lines;however,their linkage isomers have not been reported.In this study,N-glycans of CTLA4-Igs were released,labeled with procainamide,and analyzed by liquid chromatography-tandem mass spectrometry(MS/MS)to identify and quantify sialylated N-glycan linkage isomers.The linkage isomers were distinguished by comparison of 1)intensity of the N-acetylglucosamine ion to the sialic acid ion(Ln/Nn)using different fragmentation stability in MS/MS spectra and 2)retention time-shift for a selective m/z value in the extracted ion chromatogram.Each isomer was distinctively identified,and each quantity(>0.1%)was obtained relative to the total N-glycans(100%)for all observed ionization states.Twenty sialylated N-glycan isomers with onlyα2-3 linkage(s)in WT were identified,and each isomer's sum of quantities was 50.4%.Furthermore,39 sialylated N-glycan isomers(58.8%)in mono-(3 N-glycans;0.9%),bi-(18;48.3%),tri-(14;8.9%),and tetra-(4;0.7%)antennary structures of mutant were obtained,which comprised mono-(15 N-glycans;25.4%),di-(15;28.4%),tri-(8;4.8%),and tetra-(1;0.2%)sialylation,respectively,with onlyα2-3(10 N-glycans;4.8%),bothα2-3 andα2-6(14;18.4%),and onlyα2-6(15;35.6%)linkage(s).These results are consistent with those forα2-3 neuraminidase-treated N-glycans.This study generated a novel plot of Ln/Nn versus retention time to distinguish sialylated N-glycan linkage isomers in glycoprotein.
基金supported by the Shanghai Science and Technology Committee (Grant Nos. 20DZ2201900 to Y.Y. and 23ZR1432500 to W.P.)National Natural Science Foundation of China (Grant Nos. 82072602 to Y.Y.+4 种基金91853121, 21977066, and 22177069 to W.P.)Innovation Foundation of Translational Medicine of Shanghai Jiao Tong University School of Medicine(Grant No. TM202001 to Y.Y.)Collaborative Innovation Center for Clinical and Translational Science by Chinese Ministry of Education&Shanghai (Grant No. CCTS-2022202 to Y.Y.)Shanghai Pilot Program for Basic Research-Shanghai Jiao Tong University (Grant No. 21TQ1400210 to W.P.)Medical-Engineering Interdisciplinary Research Foundation of Shanghai Jiao Tong University (Grant No. YG2022ZD001 to W.P.)
文摘Malignant tumors are complex structures composed of cancer cells and tumor microenvironmental cells.In this complex structure,cells cross-talk and interact,thus jointly promoting cancer development and metastasis.Recently,immunoregulatory molecule-based cancer immunotherapy has greatly improved treatment efficacy for solid cancers,thus enabling some patients to achieve persistent responses or cure.However,owing to the development of drug-resistance and the low response rate,immunotherapy against the available targets PD-1/PD-L1 or CTLA-4 has limited benefits.Although combination therapies have been proposed to enhance the response rate,severe adverse effects are observed.Thus,alternative immune checkpoints must be identified.The SIGLECs are a family of immunoregulatory receptors(known as glyco-immune checkpoints)discovered in recent years.This review systematically describes the molecular characteristics of the SIGLECs,and discusses recent progress in areas including synthetic ligands,monoclonal antibody inhibitors,and Chimeric antigen receptor T(CAR-T)cells,with a focus on available strategies for blocking the sialylated glycan-SIGLEC axis.Targeting glyco-immune checkpoints can expand the scope of immune checkpoints and provide multiple options for new drug development.
基金supported by the Research Excellence Consortium(KKP/2020/UKM-UKM/5/1)provided by Ministry of Higher Education,Malaysiasupported by the Fundamental Research Grant Scheme(FRGS),Project No.FP016-2019A,Reference Code:FRGS/1/2019/SKK09/UM/02/2.
文摘Neurodegenerative diseases are often associated with the accumulation of oxidative stress and neuroinflammation.Edible bird’s nest(EBN)is a glycoprotein(sialylated mucin glycopeptides)found to be beneficial against neurodegenerative diseases.Antioxidative,anti-inflammatory,and anti-apoptotic properties of EBN in preserving neuronal cells were widely researched using in vitro and in vivo models.Functional effects of EBN are often linked to its great number of antioxidants and anti-inflammatory glycopeptides.Bioactive compounds in EBN,especially sialic acid,add value to neurotrophic potential of EBN and contribute to neuronal repair and protection.Various studies reporting the neuroprotective effects of EBN,their molecular mechanisms,and neuroactive composition were gathered in this review to provide better insights on the neuroprotective effects of EBN.
文摘目的探讨大肠腺癌组织粘蛋白MUC2和sialyl lewis X(sLex)的分型与临床各个病理参数之间的关系。方法应用免疫组织化学双染法对34例远切端大肠黏膜、18例大肠腺瘤及55例大肠腺癌组织进行粘蛋白MUC2、sLex检测。结果远切端大肠黏膜、大肠腺瘤及大肠腺癌中,黏蛋白MUC2阳性表达率分别为100%、94.4%和58.2%(P<0.01);sLex阳性表达率分别为5.9%、50.0%和80.0%(P<0.05)。根据MUC2和sLex在大肠腺癌中的表达把大肠腺癌分为四型:MUC2+/sLex+、MUC2+/sLex-、MUC2-/sLex+、MUC2-/sLex-。MUC2+/sLex+型与患者的性别具有相关性;MUC2+/sLex-型与淋巴结转移、Duke’s分期具有相关性;MUC2-/sLex+型与发生部位、分化程度具有相关性;MUC2-/sLex-型与大肠腺癌临床病理参数均不具有相关性。结论 MUC2的下调表达或sLex的上调表达可能参与了大肠肿瘤的发生及恶性转化,各型大肠腺癌不同程度与其分化、生物学行为相关,对临床上判断预后具有较大的意义。
基金supported by grants from the National Natural Science Foundation of China(No.81072152)the Natural Science Foundation of Hubei Province(No.2015CFA027)+1 种基金the Research Foundation of Health and Family Planning Commission of Hubei Province(No.WJ2015MA010)the Clinical Medical Research Center of Peritoneal Cancer of Wuhan(No.2015060911020462)
文摘The sialyl Lewis X（SLe;） antigen encoded by the FUT7 gene is the ligand of endotheliam-selectin（E-selectin）. The combination of SLe;antigen and E-selectin represents an important way for malignant tumor metastasis. In the present study, the effect of the SLe;-binding DNA aptamer on the adhesion and metastasis of hepatocellular carcinoma HepG2 cells in vitro was investigated. Reverse transcription-polymerase chain reaction（RT-PCR） and immunofluorescence staining were conducted to detect the expression of FUT7 at both transcriptional and translational levels. The SLe;expression in HepG2 cells treated with different concentrations of SLe;-binding DNA aptamer was detected by flow cytometry. Besides, the adhesion, migration, and invasion of HepG2 cells were measured by cell adhesion assay, and the Transwell migration and invasion assay. The results showed that the FUT7 expression was up-regulated at both mR NA and protein levels in HepG2 cells. SLe;-binding DNA aptamer could significantly decrease the expression of SLe;in HepG2 cells. The cell adhesion assay revealed that the SLe;-binding DNA aptamer could effectively inhibit the interactions between E-selectin and SLe;in the HepG2 cells. Additionally, SLe;-binding DNA aptamers at 20 nmol/L were found to have the similar effect to the monoclonal antibody CSLEX-1. The Transwell migration and invasion assay revealed that the number of penetrating cells on the down-side of Transwell membrane was significantly less in cells treated with 5, 10, 20 nmol/L SLe;-binding DNA aptamer than those in the negative control group（P<0.01）. Our study demonstrated that the SLe;-binding DNA aptamer could significantly inhibit the in vitro adhesion, migration, and invasion of HepG2 cells, suggesting that the SLe;-binding DNA aptamer may be used as a potential molecular targeted drug against metastatic hepatocellular carcinoma.
基金supported by the National Key Research and Development Program of China(2021YFC210500 and 2022YFC2104900)the National Natural Science Foundation of China(21961142016,22277111 and 22107094)Department of Science and Technology of Shandong Province(2020CXGC010601,2021ZDSYS22 and ZR2021QB061)。
文摘An efficient enzymatic assembly strategy was developed for the concise synthesis of structurally well-defined sialylated chitooligosaccharides.Two enzyme modules for theβ-1,3-N-acetyl-glucosaminylation andβ-1,4-galactosylation were applied for the grafting N-acetyl lactosamine(LacNAc)unit(s)onto the chitooligosaccharides.The LacNAc grafted chitooligosaccharides were further modified withα-2,3-orα-2,6-sialylation by two enzymatic sialylation modules to generate a total of 20 sialylated chitooligosaccharides.The inhibition study of influenza virus-induced cytopathy with synthetic sialylated chitooligosaccharides indicated that the sialic acid linkage and chain length both contribute to the binding preference and inhibition potency.
基金Project supported by National High-Technology Research and Development Program of China （No. 2006AA02Z154） and the National Natural Science Foundation of China （No. 21075137）.
文摘Sialylation of glycoproteins is vital for the function or physicochemical properties of a protein. It becomes more and more important to develop approaches that can be used to efficiently isolate and identify sialylated glycopep- tides or glycoproteins for monitoring changes in glycoproteome. In the present study, we analyze intact structures of the enriched sialylated glycopeptides of bovine fetuin by matrix-assisted laser desorption/ionization-tandem mass spectrometry （MALDI-MS/MS）, without any chemical derivation. The experimental data show that the optimal loading buffer for TiO2 as matrix is 80% acetonitrile/2% TFA （trifluoroacetic acid）/100 mg/mL DHB （2,5-dihydroxybenzoic acid） which is also compatible with MALDI-mass spectrometric analysis. This study indi- cates that the improved enrichment approach combined with MALDI-MS/MS may be a powerful tool to analyze intact structures and components of the sialylated glycopeptides from complex peptide mixture.
基金supported by the Swiss National Science Foundation(grant number 200020_129935 and R’EQUIP 145023).
文摘E-selectin is a cell-adhesion molecule of the vascular endothelium that promotes essential leukocyte rolling in the early inflammatory response by binding to glycoproteins containing the tetrasaccharide sialyl Lewisx(sLex).Efficient leukocyte recruitment under vascular flow conditions depends on an increased lifetime of E-selectin/ligand complexes under tensile force in a so-called catch-bond binding mode.Co-crystal structures of a representative fragment of the extracellular E-selectin region with sLex and a glycomimetic antagonist thereof reveal an extended E-selectin conformation,which is identified as a high-affinity binding state of E-selectin by molecular dynamics simulations.Small-angle X-ray scattering experiments demonstrate a direct link between ligand binding and E-selectin conformational transition under static conditions in solution.This permits tracing a series of concerted structural changes connecting ligand binding to conformational stretching as the structural basis of E-selectin catch-bond-mediated leukocyte recruitment.The detailed molecular view of the binding site paves the way for the design of a new generation of selectin antagonists.This is of special interest,since their therapeutic potentialwas recently demonstrated with the pan-selectin antagonists GMI-1070(Rivipansel).
