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T Cui

Publications and source records attributed to T Cui.

At least 19 recordsLinked to original sources
PubMed2001

Pivotal role of tyrosine phosphatase SHP-1 in AT2 receptor-mediated apoptosis in rat fetal vascular smooth muscle cell.

OBJECTIVE: To examine the possible crosstalk and the roles of angiotensin (Ang) II type 1 (AT1) and type 2 (AT2) receptors in the control of apoptosis in fetal vascular smooth muscle cells (VSMCs). METHODS: Fetal VSMCs were prepared from rat fetal aorta at embryonic day 20. Expression of Ang II receptors was measured by a radioligand binding assay. Apoptotic changes were assessed by caspase 3 activity and chromatin dye staining. Regulation of extracellular signal-regulated kinase (ERK) activity via Ang II receptors was analysed by determining phosphorylated ERK with Western blot. Ang II receptor-mediated activation of tyrosine phosphatase SHP-1 was assessed by protein tyrosine phosphatase assay. RESULTS: The expression of AT1 and AT2 receptors was approximately 70%: 30% per cell. Serum depletion induced apoptosis in fetal VSMCs and selective AT1 receptor stimulation attenuated the apoptotic changes, whereas selective AT2 receptor activation enhanced apoptosis. Ang II increased ERK phosphorylation, which was inhibited by addition of the AT1 receptor-specific antagonist CV11974, but enhanced by addition of the AT2 receptor-specific antagonist PD123319, suggesting that activation of AT2 receptor attenuated the AT1 receptor-mediated ERK phosphorylation. Moreover, we demonstrated that AT2 receptor stimulation activated SHP-1 in fetal VSMCs, whereas AT1 receptor stimulation did not. Transient transfection of a dominant-negative SHP-1 mutant into rat fetal VSMCs resulted in a significant decrease of the AT2 receptor-mediated inhibition of ERK phosphorylation and attenuated the proapoptotic effect of AT2 receptor. CONCLUSION: These results indicate that a crosstalk between AT1 and AT2 receptors regulates the survival of fetal VSMCs and substantiate SHP-1 as a key molecule in AT2 receptor signaling.

Analysis of Variance↗
PubMed2001

Involvement of bradykinin and nitric oxide in leptin-mediated glucose uptake in skeletal muscle.

Regulation of glucose metabolism in peripheral tissues by leptin has been highlighted recently, although its mechanism is unclear. In this study, we postulated that bradykinin and nitric oxide (NO) are involved in the effect of leptin-mediated glucose uptake in peripheral tissues and examined these possibilities. Injection of leptin (200 pg/mouse) into the ventromedial hypothalamus-enhanced glucose uptake in skeletal muscle and brown adipose tissue, but not in white adipose tissue. Treatment with Hoe140 (0.1 mg/kg), bradykinin B2 receptor antagonist, or L-NAME (N:(G)-nitro-L-arginine methyl ester) (30 mg/kg), nitric oxide synthase inhibitor, did not influence the basal level of glucose uptake in skeletal muscle and the adipose tissue, whereas Hoe140 and L-NAME inhibited leptin-mediated glucose uptake in skeletal muscles, but had no effect in adipose tissue. However, Hoe140 and L-NAME did not inhibit insulin (1.0 U/kg)-mediated glucose uptake in all tissues examined. Taken together, these results suggest that leptin enhances bradykinin and/or the NO system, which contributes at least partially to the enhanced glucose uptake in skeletal muscles.

Animals↗
PubMed2001

Fusion proteins from artificial and natural structural modules.

The purpose of preparing fusion proteins from designed and natural sequences is mainly twofold; it aims at the stabilization of structure and at the modification of biological activity. Fusion with beta-galactosidase, for example, can increase the intracellular stability and DDT-degrading activity of an artificial DDT-binding peptide, and fusions with a leucine zipper produce mono- and bifunctional single-chain variable domain antibody fragments or homodimeric and heterodimeric DNA-binding proteins like an artificial homodimeric HIV-1 enhancer-binding protein with increased binding specificity and repressor activity. Of importance are also short leader sequences that mediate the translocation of proteins across the cytoplasmic and the nuclear membrane. An interesting by-product of the leucine zipper-mediated dimerization of an HIV-1 enhancer-binding protein was the synthesis and the structural as well as functional characterization of a retro-leucine zipper.

Amino Acid Sequence↗
PubMed2001

[Effect of lead exposure during pregnancy on hippocampal long-term potentiation and expression of NMDAR-2A mRNA in the off-spring rats].

Chronic lead exposure during brain development is known to affect cognitive and behavioral functions in children and animals. The lead exposure on pregnant rats was used as a model to examine the effects of lead on the long-term potentiation(LTP) in hippocampal dentate gyrus(DG) region in vivo and the expression of NMDAR-2A mRNA by in situ hybridization in the off-springs. Female rats were exposed to 0.5 g/L or 2 g/L lead acetate in drinking water since 10 days before mating to weaning. The filial rats of 70-90 days old with blood lead levels below 100 micrograms/L were prepared for recording their DG-evoked population spike(PS) in the hippocampal DG area in vivo. The results showed that the range of LTP were (136 +/- 31)% in low lead group, (145 +/- 30)% in high lead group, and (319 +/- 114)% in control group. The reduction of NMDAR-2A mRNA expression 34%-44% in the granule and pyramidal cell layers caused by lead were seen in 21 days old rats. It indicated that the cognitive deficits induced by low-level lead exposure in early stage of life may persist to adulthood, and the modified NMDAR gene expression may play a key role in the cognitive deficits associated with lead exposure during development.

Animals↗
PubMed2000

ATRAP, novel AT1 receptor associated protein, enhances internalization of AT1 receptor and inhibits vascular smooth muscle cell growth.

We have identified a novel, membrane-located protein that interacts specifically with the carboxyl-terminal cytoplasmic domain of the AT1a receptor, which we named ATRAP (for AT1 receptor-associated protein). To further investigate the role of ATRAP in AT1 receptor function, we examined the effect of overexpression of ATRAP on angiotensin II (Ang II)-induced AT1 receptor desensitization and/or internalization, and cell proliferation in adult vascular smooth muscle cells (VSMCs). Transfection of ATRAP potentiated AT1 receptor internalization upon Ang II stimulation in these VSMCs. Moreover, we observed that AT1 receptor-induced DNA synthesis was markedly inhibited in ATRAP transfected VSMCs associated with the inhibition of the phosphorylation of signal transducers and activators of transcription (STAT) 3 and Akt. Our results suggest that ATRAP functions as a negative regulator in AT1 receptor-mediated cell proliferation in VSMCs.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Induction of apoptosis in glioma cell lines by TRAIL/Apo-2l.

TRAIL/Apo-2L, a novel cytokine, is a member of the tumor necrosis factor (TNF) family and serves as an extracellular signal triggering apoptosis. TRAIL/Apo-2L is capable of killing various transformed cells but not unstimulated primary T cells. In this study, five human glioma cells (U87, U118, U178, U563, and A172) were examined for their susceptibility to the apoptotic effects of TRAIL/Apo-2L. TRAIL/Apo-2L cDNA was isolated by RT-PCR, and recombinant TRAIL/Apo-2L protein was purified by the pMAL-c2 system (New England Biolabs, Beverly, MA). Exposure of A172 cells to bacterially expressed soluble TRAIL/Apo-2L fusion protein at a concentration of 1 microg/ml resulted in significant cell death over a 24-h period. Three experiments were performed to suggest that the TRAIL/Apo-2L killing was through the induction of apoptosis of A172 target cells. In addition, the expression of TRAIL/Apo-2L in different glioma cells was found to be variable, and TRAIL/Apo-2L-induced apoptosis was in a cell type-dependent manner. Some correlation between the susceptibility to TRAIL/Apo-2L and the expression level of one of its cognate receptors, DR4, was observed. In addition, cycloheximide worked synergistically with TRAIL/Apo-2L to induce apoptosis in glioma cells.

Apoptosis↗
PubMed2000

[Genetic polymorphism analysis of apoE intron 1 enhancer in patients with coronary heart disease and the association with serum lipid level].

OBJECTIVE: To investigate the association between the polymorphism of apolipoprotein E (apoE) intron 1 enhancer (IE1) and the level of serum lipid in patients with coronary heart disease (CHD). METHODS: ApoE IE1 genotypes of 81 patients with CHD and 108 healthy subjects were detected by polymerase chain reaction and restriction fragment length polymorphism. RESULTS: The frequency of G/G genotype in patients with CHD was significantly higher than that in control group (P < 0.05). The frequency of G allele was significantly higher in patients than in control group (P < 0.05). The gene polymorphism of apoE IE1 obviously influenced the serum lipid levels. The concentrations of TC, and LDL-C among different genotype groups were significantly different, and the level in G/G group was higher than that in C/C group (P < 0.05). CONCLUSION: ApoE IE1 gene polymorphism is closely related to serum lipid, and G/G genotype of apoE IE1 may be a risk factor of coronary heart disease in Han Chinese.

Aged↗
PubMed2000

Gene polymorphism in apolipoprotein E and presenilin-1 in patients with late-onset Alzheimer's disease.

OBJECTIVE: To evaluate the association of apolipoprotein E (apoE) and presenilin-1 (PS-1) gene polymorphism with late-onset Alzheimer's disease (AD). METHODS: A case-control study was undertaken to detect the polymorphism of apoE and PS-1 by polymerase chain reaction and digestion with the endonucleases of BspL I, Hha I and BamH I. RESULTS: The frequencies of apoE epsilon 3/4 genotype and epsilon 4 allele in late-onset AD (n = 42) were significantly higher than those of age-matched controls (P < 0.05). The frequencies of the apoE intron 1 enhancer (IE1) G/G genotype and G allele in late-onset AD were also significantly higher than those in controls (P < 0.05). The frequencies of the PS-1 1/1 genotype but not the 1 allele in AD were significantly higher than those in controls (P < 0.05). The apoE epsilon 4 allele was associated with a tripling of risk for late-onset AD compared with that with no epsilon 4 allele (odds ratio: 2.932). Homozygosity of the G allele in IE1 and 1/1 genotype in PS-1 was associated with a doubling of risk for late-onset AD, and odds ratios were 2.223 and 2.066, respectively. When the apoE epsilon 4 was controlled, the association between the IE1 G/G genotype AD was no longer statistically significant (P > 0.05). We sequenced the exon 4 of apoE in patients with late-onset AD, and found no other genetic polymorphism or mutation except for apoE epsilon 4 and IE1 G alleles associated with AD. CONCLUSION: apoE epsilon 4 gene appears to be the strongest gene risk factor for late-onset AD and its apparent association between the IE1 G/G genotype and late-onset AD is a consequence of the association between the epsilon 4 and IE1 G/G genotype. The PS-1/1 genotype is weakly associated with late-onset AD.

Aged↗
PubMed1999

Purification and crystallization of precursors and autoprocessed enzymes of Flavobacterium glycosylasparaginase: an N-terminal nucleophile hydrolase.

Glycosylasparaginase (GA) represents a novel group of proteins that are activated by self-catalyzed peptide-bond cleavage from a single-chain precursor to yield the two subunits required for hydrolase activity. The wild-type GA precursor autoproteolyzes spontaneously into alpha and beta subunits. Strategies are reported here for purification to homogeneity of GA from Flavobacterium meningosepticum in both single-chain precursor and mature (autoprocessed) forms. The recombinant proteins crystallize in different space groups: P1 and P2(1) for the precursor and mature enzymes, respectively. The precursor crystals diffract to 1.9 A resolution with laboratory X-ray radiation.

Aspartylglucosylaminase↗
PubMed1999

Mutations of endo-beta-N-acetylglucosaminidase H active site residueAs sp130 anG glu132: activities and conformations.

Endo-beta-N-acetylglucosaminidase H hydrolyzes the beta-(1-4)-glycosidic link of the N,N'-diacetylchitobiose core of high-mannose and hybrid asparagine-linked oligosaccharides. Seven mutants of the active site residues, Asp130 and Glu132, have been prepared, assayed, and crystallized. They include single site mutants of each residue to the corresponding amide, to Ala and to the alternate acidic residue, and to the double amide mutant. The mutants of Asp130 are more active than the corresponding Glu132 mutants, consistent with the assignment of the latter residue as the primary catalytic residue. The amide mutants are more active than the alternate acidic residue mutants, which in turn are more active than the Ala mutants. The structures of the Asn mutant of Asp130 and the double mutant are very similar to that of the wild-type enzyme. Several residues surrounding the mutated residues, including some that form part of the core of the beta-barrel and especially Tyr168 and Tyr244, adopt a very different conformation in the structures of the other two mutants of Asp130 and in the Asp mutant of Glu132. The results show that the residues in the upper layers of the beta-barrel can organize into two very distinct packing arrangements that depend on subtle electrostatic and steric differences and that greatly affect the geometry of the substrate-binding cleft. Consequently, the relative activities of several of the mutants are defined by structural changes, leading to impaired substrate binding, in addition to changes in functionality.

Amino Acid Sequence↗
PubMed1999

[Use of visual aids for vision of disabled children].

OBJECTIVE: To discuss the effect of using distance and near optical low vision devices for children in low vision clinic. METHOD: 139 subjects from age 6 to 14 years were provided with 2.5 X telescopes and + 8.00D to + 40.00D glasses for improving far and near sight respectively. RESULT: 22.3% subjects' distance visual acuity was >or= 0.5 and 53.2% subjects' near visual acuity was >or= 0.5 after using distance and near low vision aids. CONCLUSIONS: Low vision aid is essential and effective in low vision clinic. It not only improves the visual acuity of visual disabled children, but also helps the development of special education through visual rehabilitation.

Adolescent↗
PubMed1999

[Correlation of conformational change with enzyme activity of glucose isomerase in denaturants monitored with high performance liquid chromatography].

Glucose isomerase (GI) can catalyze in vitro the isomerization of D-glucose to D-fructose. So it is an extremely important industrial enzyme in the commercial conversion of starch to high fructose syrups. In the previous papers, we have purified and characterized the enzyme from streptomyces diastaticus M1033 of China and obtained the crystal structures by X-ray. In this paper, a method for measurement of the dynamic conformational change procedure of glucose isomerase in various concentrations of denaturants by HPLC has been established. At first the relative molecular mass of GI in solution is measured by HPLC on PROTEIN PAK 300SW (7.5 mm i.d. x 30 cm) column. The relative molecular mass of GI is about 150,000. So GI exists as tetramer in the solution without denaturants. In 0-5 mol/L guanidine hydrochloride, incubated at 30 degrees C for 30 min, GI is gradually dissociated into monomer, and at the same time its activity gradually disappears. In various concentrations of urea and incubation at 30 degrees C for 30 min (or 60 degrees C for 1 h), the results are different from that in guanidine, because the monomers peaks of GI is not found. Only in certain concentrations of urea, the small dimer peaks of GI is found, but the activity of GI significantly disappears. Moreover as the increase of the urea concentration, the retention time of tetramer peak is gradually decreases. From the fluorescence spectra, we found the conformation of GI changed in the solution of urea. So perhaps in urea, the conformation of GI become a little unfolded, and the active region is partly damaged, which makes GI partly inactive. Dissociation into inactive monomers and conformation partly unfolding are all the reason of GI inactivation in denaturants.

Aldose-Ketose Isomerases↗
PubMed1998

Recombinant dengue virus type 1 NS3 protein exhibits specific viral RNA binding and NTPase activity regulated by the NS5 protein.

The full-length dengue virus NS3 protein has been successfully expressed as a 94-kDa GST fusion protein in Escherichia coli. Treatment of the purified fusion protein with thrombin released a 68-kDa protein which is the expected molecular mass for the DEN1 NS3 protein. The identity of this protein was confirmed by Western blotting using dengue virus antisera. Two related activities of the recombinant NS3 protein were characterized, which were the binding of the protein to the 3'-noncoding region of the dengue virus RNA genome and NTPase activity. We demonstrated using a band shift assay that the DEN1 NS3 protein could form a complex with the stem-loop structure in the 3'-noncoding region (3'-NCR), although sites outside the stem-loop may also participate in binding. Using various unlabeled homopolymeric and heteropolymeric RNAs as competitors for binding, it was further shown that the DEN1 NS3 protein exhibits preferential binding to a 94-nt RNA transcript from the 3'-NCR of the dengue virus. The NTPase activity of the recombinant DEN1 NS3 protein was characterized using a thin-layer chromatography assay. We found that the DEN1 NS3 protein possesses some aspects of NTPase activity, which are distinct from those found in other flaviviruses. Although the NS3 protein was able to utilize all four ribonucleoside triphosphates as its substrates, the NS3 protein showed a distinct preference for purine triphosphates (i.e., ATP and GTP). The addition of poly(U) did not stimulate NTPase activity in DEN1 NS3 protein, which contrasts with the reports for other flaviviral NS3 proteins. However, NTPase activity was specifically stimulated by the viral NS5 protein, which was manifested by a more than twofold increase in the rate of ATP hydrolysis and a 25% increase in the yield of ADP at the end of a 120-min reaction. These data suggest that the NTPase activity of the NS3 protein may be regulated by the viral NS5 protein during virus replication.

Adenosine Triphosphatases↗
PubMed1998

Characterization and functional analysis of the cis-autoproteolysis active center of glycosylasparaginase.

Glycosylasparaginase is an N-terminal nucleophile hydrolase and is activated by intramolecular autoproteolytic processing. This cis-autoproteolysis possesses unique kinetics characterized by a reversible N-O acyl rearrangement step in the processing. Arg-180 and Asp-183, involved in binding of the substrate in the mature enzyme, are also involved in binding of free amino acids in the partially formed substrate pocket on certain mutant precursors. This binding site is sequestered in the wild-type precursor. Binding of free amino acids on mutant precursors can either inhibit or accelerate their processing, depending on the individual mutants and amino acids. The polypeptide sequence at the processing site, which is highly conserved, adopts a special conformation. Asp-151 is essential for maintaining this conformation, possibly by anchoring its side chain into the partially formed substrate pocket through interaction with Arg-180. The reactive nucleophile Thr-152 is activated not only by deprotonation by His-150 but also by interaction with Thr-170, suggesting a His-Thr-Thr active triad for the autoproteolysis.

ATP-Binding Cassette Transporters↗
PubMed1998

Crystal structure of glycosylasparaginase from Flavobacterium meningosepticum.

The crystal structure of recombinant glycosylasparaginase from Flavobacterium meningosepticum has been determined at 2.32 angstroms resolution. This enzyme is a glycoamidase that cleaves the link between the asparagine and the N-acetylglucosamine of N-linked oligosaccharides and plays a major role in the degradation of glycoproteins. The three-dimensional structure of the bacterial enzyme is very similar to that of the human enzyme, although it lacks the four disulfide bridges found in the human enzyme. The main difference is the absence of a small random coil domain at the end of the alpha-chain that forms part of the substrate binding cleft and that has a role in the stabilization of the tetramer of the human enzyme. The bacterial glycosylasparaginase is observed as an (alphabeta)2-tetramer in the crystal, despite being a dimer in solution. The study of the structure of the bacterial enzyme allows further evaluation of the effects of disease-causing mutations in the human enzyme and confirms the suitability of the bacterial enzyme as a model for functional analysis.

Aspartylglucosylaminase↗
PubMed1998

[Studies on the relationship between smoking and formation of DNA adducts in lung tissues].

OBJECTIVE: To explore the relationship between smoking and contents of DNA adducts in the lung tissues, and to study if there is any its difference between the patients with and without lung cancer and between males and females. METHODS: DNA was extracted from the normal lung tissues dissected from the concurrently hospitalized patients with and without lung cancer (19 and 18 each for males and females). Contents of DNA adducts in the lung tissues were determined by 32P-postlabelling assay. RESULTS: Smoking could cause increase in levels of DNA adducts in the lung tissues. There were no significant difference in DNA adduct levels between the lung tissues from men and women and from the patients with and without lung cancer, after the adjustment for smoking factor. CONCLUSION: More data should be accumulated to elucidate the relationship between DNA adduct levels in the human bodies and its biological effects.

DNA Adducts↗
PubMed1998

[Immobilization of rat liver microsomes with liquid lipid membrane encapsulation].

Rat liver microsomes were immobilized by encapsulating them into liquid lipid membranes (56% paraffin thick, 38% paraffin thin, 5% lecthin and 1% dodecanol). The resistance against heat and pH profile of the immobilized enzyme-NADPH-cytochrome C reductase was weakened. However, the activity and storage stability of the immobilized enzyme were enhanced.

Animals↗