Blocking of N-acetylglucosaminyltransferase V induces cellular endoplasmic reticulum stress in human hepatocarcinoma 7721 cells

N-acetylglucosaminyltransferase V （GnT-V） is an important tumorigenesis and metastasis-associated enzyme. To study its biofunction, the GnT-V stably suppressed cell line （GnT-V-AS/7721） was constructed from 7721 hepatocarcinoma cells in previous study. In this study, cDNA array gene expression profiles were compared between GnT-V-AS/7721 and parental 7721 cells. The data indicated that GnT-V-AS/7721 showed a characteristic expression pattern consistent with the ER stress. The molecular mechanism of the ER stress was explored in GnT-V-AS/7721 by the analysis on key molecules in both two unfolded protein response （UPR） pathways. For ATF6 and Irel/XBP-1 pathway, it was evidenced by the up-regulation of BIP at mRNA and protein level, and the appearance of the spliced form ofXBP-1. As for PERK/eIF2α pathway, the activation of ER eIF2α kinase PERK was observed. To confirm the results from GriT-V-AS/7721 cells, the key molecules in the UPR were examined again in 7721 cells interfered with the GnT-V by the specific RNAi treatment. The results were similar with those from GnT-V-AS/7721, indicating that blocking of GnT-V can specifically activate ER stress in 7721 cells. Rate of 3H-Man incorporation corrected with rate of 3H-Leu incorporation in GnT-V-AS/7721 was down-regulated greatly compared with the control, which demonstrated the deficient function of the enzyme synthesizing N-glycans after GnT-V blocking. Moreover, the faster migrating form of chaperone GRP94 associated with the underglycosylation, and the extensively changed N-glycans structures of intracellular glycoproteins were also detected in GnT-V-AS/7721. These results supported the mechanism that blocking of GnT-V expression impaired functions of chaperones and N-glycan-synthesizing enzymes, which caused UPR in vivo.

O-linked N-acetylglucosamine transferase(OGT) is overexpressed and promotes O-linked protein glycosylation in esophageal squamous cell carcinoma

The aim of this present study was to explore the expression and clinical significance of O-linked N-acetylglucosamine（O-GlcNAc） transferase（OGT） and enzymatic O-linked glycosylation（O-GlcNAcation） through the addition of O-linked-β-N-acetylglucosamine in esophageal squamous cell carcinoma.OGT expression and O-GlcNAcation in 40 samples from patients with esophageal squamous cell carcinoma was detected by immunohistochemical staining with anti-OGT antib ody and O-GlcNAc-specific antibody RL 2,respectively.The relationship between pathological and clinical factors of patients was analyzed.We found that the expression of OGT was higher in esophageal squamous cell carcinoma samples compared to the normal tissues.RL 2 antibody level was positively correlated with OGT expression,and the metastasis of lymph node,which means the level of O-GlcNAcation was high and related to the metastasis of lymph node in esophageal squamous cell carcinoma.In conclusion,OGT activation is the main reason for promoting the level of O-GlcNAcation in esophageal squamous cell carcinoma.O-GlcNAcylation may play an important role in esophageal squamous cell carcinoma.

Extracellular O-linked β-N-acetylglucosamine: Its biology and relationship to human disease

The O-linked β-N-acetylglucosamine(O-GlcNAc)ylation of cytoplasmic and nuclear proteins regulates basic cellular functions and is involved in the etiology of neurodegeneration and diabetes. Intracellular O-GlcNAcylation is catalyzed by a single O-GlcNAc transferase, O-GlcNAc transferase(OGT). Recently, an atypical O-GlcNAc transferase, extracellular O-linked β-N-acetylglucosamine(EOGT), which is responsible for the modification of extracellular O-GlcNAc, was identified. Although both OGT and EOGT are regulated through the common hexosamine biosynthesis pathway, EOGT localizes to the lumen of the endoplasmic reticulum and transfers GlcNAc to epidermal growth factor-like domains in an OGT-independent manner. In Drosophila, loss of Eogt gives phenotypes similar to those caused by defects in the apical extracellular matrix. Dumpy, a membrane-anchored apical extracellular matrix protein, was identified as a major O-GlcNAcylated protein, and EOGT mediates Dumpy-dependent cell adhesion. In mammals, extracellular O-GlcNAc was detected on extracellular proteins including heparan sulfate proteoglycan 2, Nell1, laminin subunit alpha-5, Pamr1, and transmembrane proteins, including Notch receptors. Although the physiological function of O-GlcNAc in mammals has not yet been elucidated, exome sequencing identified homozygous EOGT mutations in patients with Adams-Oliver syndrome, a rare congenital disorder characterized by aplasia cutis congenita and terminal transverse limb defects. This review summarizes the current knowledge of extracellular O-GlcNAc and its implications in the pathological processes in Adams-Oliver syndrome.

基于FANUC I/O-Link轴外围设备控制的刀库选刀程序设计

为降低加工中心刀库选刀故障率,提出应用FANUC I/O-Link轴外围设备控制技术、通过伺服电机驱动刀盘分度与定位的方法,并对I/O-Link轴的功能指令格式与作用、地址分配、参数设定、PMC程序设计做了详细的介绍。经过机电联调,验证了基于I/O-Link轴的刀库选刀控制精准,可靠性高,换刀时间短。

VLDL受体在人和家兔主要组织中的分布

根据极低密度脂蛋白受体 (VLDL R)是否含有胞膜外 O-L ink糖链结合域分为两型 :I型为含 O-Link糖链结合域 ; 型则不含 O-L ink糖链结合域。采用逆转录技术从人和家兔的主要组织中获得 VLDLR的 c DNA,PCR扩增后经电泳鉴定显示 , 型受体分布于心肌、骨骼肌、脾、肾、脂肪、肝 ,而 型受体分布于脂肪、脾脏、肾脏。由于两种受体的功能不尽相同 ,不同 VLDL受体在组织中的分布存在差异。人和家兔的 VL

AS模型兔主动脉平滑肌与骨骼肌中VLDL受体亚型的分布和表达

极低密度脂蛋白受体(VLDLR)分为两型,Ⅰ型受体含有胞外O-连接糖链结合域,Ⅱ型受体不含O-连接糖链结合域。在疾病状态下,某些组织中VLDLR亚型分布发生改变,为了验证VLDLR亚型分布变化是否与机体脂质代谢紊乱有关,运用RT-PCR技术对VLDLR亚型在动脉硬化(AS)家兔模型组织中的分布和表达进行研究。研究发现,与正常家兔相比,在AS家兔中,骨骼肌Ⅰ型受体表达略有上调,主动脉平滑肌Ⅰ型受体上调幅度比骨骼肌高,但亚型分布并没有明显改变。

Correlation of glycosyltransferases mRNA expression in extrahepatic bile duct carcinoma with clinical pathological characteristics

BACKGROUND: The incidence of extrahepatic bile duct carcinoma (EBDC) has been increasing, especially in aged people, but the glycobiology of the tumor is not elucida- ted. In this study we investigated the expressions of three glycosyltransferases in 35 patients with EBDC and 35 pa- tients with benign biliary duct disease (BBDD) as well as their clinicopathological significance. METHOD: The patients were divided into several sub- groups by tumor differentiation, TNM stage, and invasion by the standards recommended by UICC. Tumor samples were immediately frozen in liquid nitrogen after resection, followed by mRNA determination of enzymes in the tissue using a mRNA selective reverse trancriptase-polymerase chain reaction kit. The mRNA levels of different groups were semi-quantitatively compared. RESULTS: The mRNA levels of N-acetylglucosaminyltrans- ferase V (GnT-V) and a subtype of α2,3 sialyltransferases for N-glycans, ST3Gal- were elevated 7.75 and 5.39 times in EBDC as compared with BBDD, respectively, and they were correlated to several clinicopathological factors including tumor advancement, differentiation, metastasis, and invasiveness. The mRNA expression of another sialyl- transferase, ST6Gal- , was also 0.63-fold higher in EBDC than in BBDD, but not involved in the clinicopathological characteristics. CONCLUSION: The elevated expression of these three gly- cosyltransferases can be considered as an important molecu- lar event in the occurrence and progression of EBDC.

A living cell-based fluorescent reporter for high-throughput screening of anti-tumor drugs

Suppression of cellular O-linkedβ-N-acetylglucosaminylation(O-Glc NAcylation)can repress proliferation and migration of various cancer cells,which opens a new avenue for cancer therapy.Based on the regulation of insulin gene transcription,we designed a cell-based fluorescent reporter capable of sensing cellular O-Glc NAcylation in HEK293 T cells.The fluorescent reporter mainly consists of a reporter(green fluorescent protein(GFP)),an internal reference(red fluorescent protein),and an operator(neuronal differentiation 1),which serves as a"sweet switch"to control GFP expression in response to cellular OGlc NAcylation changes.The fluorescent reporter can efficiently sense reduced levels of cellular OGlc NAcylation in several cell lines.Using the fluorescent reporter,we screened 120 natural products and obtained one compound,sesamin,which could markedly inhibit protein O-Glc NAcylation in He La and human colorectal carcinoma-116 cells and repress their migration in vitro.Altogether,the present study demonstrated the development of a novel strategy for anti-tumor drug screening,as well as for conducting gene transcription studies.

Synthesis and Crystal Structure of Spiro[1-bromo-4-l-menthyloxy-5-oxo-6-oxa-bicyclo[3.1.0]hexane-2,2'-3'-(16''-methoxyacetatyl-4'-l-menthyloxybutyrolactone)]

The title compound, spiro[ 1-bromo-4-l-menthyloxy-5-oxo-6-oxa-bicyclo[3.1.0]- hexane-2,2＇-3＇-（16＇-methoxyacetatyl-4＇-l-menthyloxybutyrolactone）] 1, was obtained via tandem asymmetric double Michael addition/internal nucleophilic substitution of the chiral synthon, 5-l-menthyloxy-3-bromo-2-（5H）-furanone 2 with methoxy α-chloroacetate as a nucleophile under mild conditions, and structurally [letermined by single-crystal X-ray diffraction. Crystal data： C31H47BrO9, Mr = 643.60, orthorhombic, space group P212121. α = 9.6564（7）, b = 14.8994（11）, c = 23.6771（17） A, V= 3406.5（4） A^3, Z = 4, Dc= 1.255 g/cm^3, 2（MoKa） = 0.71073 A,μ= 1.254 mm^-1 and F（000） = 1360. The structure was refined to R =[0.0324 and wR = 0.0737 for 5123 observed reflections （I〉 2σ（I））. The crystallographic results of molecule 1 show that the interesting reaction of 2 with methoxy α-chloroacetate, in the usual manner, gave the spiro-cyclopropane skeleton with O-linked derivative containing multiple stereogenic centers 1 rather than the expected C-linked derivative.

Synthesis and Crystal Structure of Spiro[1-bromo-4-methoxy-5-oxa-6-oxo-bicyclo[3.1.0]hexane-2,2＇-（3＇-cyclohexanoxy-4＇-methoxybutyrolactone）

The title compound, spiro[1-bromo-4-l-menthyloxy-5-oxo-6-oxa-bicyclo[3.1.0]-hexane-2,2-3-(16-methoxyacetatyl-4-l-menthyloxybutyrolactone)] 1, was obtained via tandem asymmetric double Michael addition/internal nucleophilic substitution of the chiral synthon, 5-l-menthyloxy-3-bromo-2-(5H)-furanone 2 with methoxy α-chloroacetate as a nucleophile under mild conditions, and structurally determined by single-crystal X-ray diffraction. Crystal data: C31H47BrO9, Mr = 643.60, orthorhombic, space group P212121, a = 9.6564(7), b = 14.8994(11), c = 23.6771(17) , V = 3406.5(4) 3, Z = 4, Dc = 1.255 g/cm3, λ(MoKα) = 0.71073 , μ = 1.254 mm-1 and F(000) = 1360. The structure was refined to R = 0.0324 and wR = 0.0737 for 5123 observed reflections (I > 2σ(I)). The crystallographic results of molecule 1 show that the interesting reaction of 2 with methoxy α-chloroacetate, in the usual manner, gave the spiro-cyclopropane skeleton with O-linked derivative containing multiple stereogenic centers 1 rather than the expected C-linked derivative.