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Lan Xu

Publications and source records attributed to Lan Xu.

33 records · Page 2Linked to original sources
PubMed2004

Virtual screening of human 5-aminoimidazole-4-carboxamide ribonucleotide transformylase against the NCI diversity set by use of AutoDock to identify novel nonfolate inhibitors.

AICAR transformylase (5-aminoimidazole-4-carboxamide ribonucleotide transformylase) is a folate-dependent activity of the bifunctional protein ATIC (AICAR transformylase and IMP cyclohydrolase) and is responsible for catalyzing the penultimate step of the de novo purine biosynthetic pathway. As such, AICAR transformylase has been proposed as a potential target for antineoplastic drug design. Virtual screening of the human AICAR transformylase active site by use of AutoDock against the NCI diversity set, a library of compounds with nonredundant pharmacophore profiles, has revealed 44 potential inhibitor candidates. In vitro inhibition assay of 16 soluble compounds from this list revealed that eight compounds with novel scaffolds, relative to the general folate template, had micromolar inhibition. Subsequent extension of docking trials on compounds with similar scaffolds from the entire NCI-3D database has unveiled 11 additional inhibitors that were confirmed by the in vitro inhibition assay. In particular, one compound, NSC30171, had nanomolar inhibition (K(i) = 154 nM, IC(50) = 600 nM) against AICAR transformylase. These 19 inhibitors serve as novel templates/scaffolds for development of more potent and specific non-folate-based AICAR transformylase inhibitors.

Binding Sites↗
PubMed2004

Electrochemical impedance behavior of DNA biosensor based on colloidal Ag and bilayer two-dimensional sol-gel as matrices.

A novel method for fabrication of DNA biosensors has been developed by means of self-assembling colloidal Ag (Ag) to a thiol-containing sol-gel network. The thiol groups of 3-mercaptopropyltrimethoxysilane (MPTS) serve as binding sites for the covalent attachment to gold electrode surface. Then the one-dimensional network of silane unites (1dMPTS) was combined together into a two-dimensional sol-gel network (2dMPTS) by dipping into aqueous NaOH. The second silane layer (B2dMPTS) was formed by immersing electrodes back into the MPTS solution overnight, and then the Ag nanoparticles were chemisorbed onto the thiol groups of the second silane layer. Finally, the mercapto oligonucleotide was self-assembled onto the surface via the Ag nanoparticles. The modified process was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). In addition, we utilized the impedance spectroscopy as a platform for DNA sensing assay. The factors influencing the performance of the resulting biosensor were studied in detail. The linear range of the biosensor was from 8.0 x 10(-9) to 1.0 x 10(-6) M with a detection limit of 4.0 x 10(-9) M at 3sigma. In addition, the experiment results indicate that oligonucleotide immobilized on this way exhibits a good sensitivity and selectivity, high stability and a long-term maintenance of bioactivity.

Binding Sites↗
PubMed2004

Crystal structure of avian aminoimidazole-4-carboxamide ribonucleotide transformylase in complex with a novel non-folate inhibitor identified by virtual ligand screening.

Aminoimidazole-4-carboxamide ribonucleotide transformylase (AICAR Tfase), one of the two folate-dependent enzymes in the de novo purine biosynthesis pathway, is a promising target for anti-neoplastic chemotherapy. Although classic antifolates, such as methotrexate, have been developed as anticancer agents, their general toxicity and drug resistance are major issues associated with their clinical use and future development. Identification of inhibitors with novel scaffolds could be an attractive alternative. We present here the crystal structure of avian AICAR Tfase complexed with the first non-folate based inhibitor identified through virtual ligand screening of the National Cancer Institute Diversity Set. The inhibitor 326203-A (2-[5-hydroxy-3-methyl-1-(2-methyl-4-sulfophenyl)-1H-pyrazol-4-ylazo]-4-sulfo-benzoic acid) displayed competitive inhibition against the natural cofactor, 10-formyl-tetrahydrofolate, with a K(i) of 7.1 mum. The crystal structure of AICAR Tfase with 326203-A at 1.8 A resolution revealed a unique binding mode compared with antifolate inhibitors. The inhibitor also accessed an additional binding pocket that is not occupied by antifolates. The sulfonate group of 326203-A appears to form the dominant interaction of the inhibitor with the proposed oxyanion hole through interaction with a helix dipole and Lys(267). An aromatic interaction with Phe(316) also likely contributes to favorable binding. Based on these structural insights, several inhibitors with improved potency were subsequently identified in the National Cancer Institute Compound Library and the Available Chemical Directory by similarity search and molecular modeling methods. These results provide further support for our combined virtual ligand screening rational design approach for the discovery of novel, non-folate-based inhibitors of AICAR Tfase.

Animals↗
PubMed2003

Distinct domain utilization by Smad3 and Smad4 for nucleoporin interaction and nuclear import.

Smad proteins undergo rapid nuclear translocation upon stimulation by transforming growth factor-beta (TGFbeta) and in so doing transduce the signal into the nucleus. In this report we unraveled nuclear import mechanisms of Smad3 and Smad4 that are dependent on their interaction with FG-repeat-containing nucleoporins such as CAN/Nup214, without the involvement of importin molecules that are responsible for most of the known nuclear import events. A surface hydrophobic corridor within the MH2 domain of Smad3 is critical for association with CAN/Nup214 and nuclear import, whereas Smad4 interaction with CAN/Nup214, and nuclear import requires structural elements present only in the full-length Smad4. As exemplified by the different susceptibility to inhibition of import by cytoplasmic retention factor SARA (Smad anchor for receptor activation), such utilization of distinct domains for nuclear import of Smad3 and Smad4 suggests that nuclear transport of Smad3 and Smad4 is subject to control by different retention factors.

Active Transport, Cell Nucleus↗
PubMed2003

IL-13 is necessary, not simply sufficient, for epicutaneously induced Th2 responses to soluble protein antigen.

Th2 responses are clearly involved in the pathogenesis of atopic disease. Thus, understanding the factors responsible for Th2 sensitization at sites of allergen exposure, such as airway and skin, is crucial for directing therapeutic or preventive strategies. Contrary to other models of Th2 sensitization to proteins, we have reported that Th2 responses induced by epicutaneous exposure to OVA are IL-4 independent. Combined deficiency of both IL-4 and IL-13 signaling did prevent Th2 generation, suggesting that IL-13 was mediating these IL-4-independent responses. It was not clear, however, whether IL-13 was simply replacing the need for IL-4 in genetically deficient mice or if IL-13 played a unique role. In the present study, we show that Th2 responses induced by epicutaneous OVA exposure (including lung inflammatory responses after inhaled Ag challenge, OVA-specific IgG1, and draining lymph node IL-5 production) are impaired in IL-13-deficient (IL-13(-/-)) mice compared with wild type. In contrast, i.p. sensitization of IL-13(-/-) mice resulted in responses equivalent to wild type. Generation of contact hypersensitivity to dinitrofluorobenzene, which involves Th1 and CD8(+) effector cells, was also intact in IL-13(-/-) mice. Taken together, the data indicate that IL-13 is the major inducer of Th2 generation in the cutaneous microenvironment, being required independently of IL-4. This fact, in combination with the known abundance of IL-13 in atopic dermatitis skin lesions, emphasizes the potentially important role of the skin as a site for Th2 sensitization to environmental allergens, particularly in atopic individuals.

Administration, Cutaneous↗
PubMed2003

The receptor binding protein P2 of PRD1, a virus targeting antibiotic-resistant bacteria, has a novel fold suggesting multiple functions.

Bacteriophage PRD1 is unusual, with an internal lipid membrane, but has striking resemblances to adenovirus that include receptor binding spikes. The PRD1 vertex complex contains P2, a 590 residue monomer that binds to receptors on antibiotic-resistant strains of E. coli and so is the functional counterpart to adenovirus fiber. P2 structures from two crystal forms, at 2.2 and 2.4 A resolution, reveal an elongated club-shaped molecule with a novel beta propeller "head" showing pseudo-6-fold symmetry. An extended loop with another novel fold forms a long "tail" containing a protruding proline-rich "fin." The head and fin structures are well suited to recognition and attachment, and the tail is likely to trigger the processes of vertex disassembly, membrane tube formation, and subsequent DNA injection.

Amino Acid Sequence↗
PubMed2003

Differential roles for CD4 and CD8 T cells after diisocyanate sensitization: genetic control of TH2-induced lung inflammation.

BACKGROUND: Exposure to diisocyanates is a major cause of occupational asthma. We previously developed a novel mouse model of diisocyanate-induced asthma involving epicutaneous sensitization to hexamethylene diisocyanate (HDI) that demonstrates many features of the human disease, including airway eosinophilia and mucus hypersecretion. OBJECTIVE: To determine what factors are critical for the development of HDI-induced airway inflammation, we investigated the strain distribution of this response and the roles of CD4(+) and CD8(+) T cells. METHODS: Mice were epicutaneously exposed to HDI and then challenged with HDI, either by means of inhalation to induce airway inflammation or on the ear to induce contact hypersensitivity (CHS). Lymph node cytokine production and serum antibodies were also measured. RESULTS: Induction of airway eosinophilia was highly dependent on the mouse strain used, with C57BL/6, A/J, CBA, C3H, and C57BL/10 mice all having significantly fewer eosinophils than BALB/c mice. HDI-specific antibodies and lymph node IL-5 and IL-13 production were also diminished in non-BALB/c strains. In contrast, CHS to HDI developed in all strains tested. Studies in mice deficient in either CD4(+) or CD8(+) T cells revealed that CD4(+) T cells were critical for HDI-induced airway eosinophilia, whereas CD8(+) T cells were the major effector cells in CHS. CONCLUSION: The data suggest that, in contrast to CHS, induction of T(H)2 responses after epicutaneous exposure to diisocyanates is strongly genetically influenced. Furthermore, the lung inflammatory response to inhaled HDI appears to depend primarily on effective generation of these CD4(+) T(H)2 responses, as is the case in atopic asthma.

Animals↗
PubMed2003

[Influence of irradiation on the dynamic three-dimension distribution of abl and bcr genes in the interphase nuclei of IM-9 cell].

OBJECTIVE: To investigate the material foundation of the fusion of bcr and abl genes, and to explore the pathogenesis of chronic myeloid leukemia. METHODS: By FISH combined with laser confocal scanning microscopy, the three-dimension (3D) distribution of bcr and abl genes in the interphase nuclei of normal and irradiated IM-9 cells was studied in each cell cycle phases. RESULTS: abl and bcr genes distributed non-randomly in the interphase nuclei of IM-9 cells. abl gene preferably located at the outer layer and bcr near the core of the nucleus. The two genes were drawn near each other most in G(0) phase. The relative distance between the homologous genes was greater at proliferation phase than at quiescence phase. After irradiation, the relative distances from the two genes to the core and between the two genes were shortened, with the shortest distance between the two genes in S phase. CONCLUSION: Irradiation could change the 3D-distribution of abl and bcr genes in the interphase nuclei of IM-9 cell and accelerate them to draw near each other.

Cell Nucleus↗
PubMed2002

Smad2 nucleocytoplasmic shuttling by nucleoporins CAN/Nup214 and Nup153 feeds TGFbeta signaling complexes in the cytoplasm and nucleus.

The transcription factor Smad2 is released from cytoplasmic retention by TGFbeta receptor-mediated phosphorylation, accumulating in the nucleus where it associates with cofactors to regulate transcription. We uncovered direct interactions of Smad2 with the nucleoporins CAN/Nup214 and Nup153. These interactions mediate constitutive nucleocytoplasmic shuttling of Smad2. CAN/Nup214 and Nup153 compete with the cytoplasmic retention factor SARA and the nuclear Smad2 partner FAST-1 for binding to a hydrophobic corridor on the MH2 surface of Smad2. TGFbeta receptor-mediated phosphorylation stimulates nuclear accumulation of Smad2 by modifying its affinity for SARA and Smad4 but not for CAN/Nup214 or Nup153. Thus, by directly contacting the nuclear pore complex, Smad2 undergoes constant shuttling, providing a dynamic pool that is competitively drawn by cytoplasmic and nuclear signal transduction partners.

3T3 Cells↗
PubMed2002

The myelodysplastic syndromes: analysis of prognostic factors and comparison of prognostic systems in 128 Chinese patients from a single institution.

INTRODUCTION: Although retrospective analysis were frequently undertaken, and many prognostic systems for myelodysplastic syndromes (MDS) have been proposed worldwide, few such studies have been performed and the effectiveness of different scoring systems have not yet been verified in independent patient populations in China. The aim of this single center study was to evaluate the prognostic factors and compare the prognostic scoring systems in Chinese patients with MDS. MATERIALS AND METHODS: One hundred and twenty-eight patients diagnosed as primary MDS in our Institution were studied retrospectively to identify significant prognostic factors and to assess the predictive value of 11 previously described prognostic systems, including French-American-British (FAB) classification, World Health Organization (WHO) classification, Mufti, Sanz, Morra, Aul, Oguma, Toyama, Morel and international prognostic scoring system (IPSS). RESULTS: The median age of the patients was 50 years (range 13-82). The 2- and 5-year survival rate of the patients were 55.22+/-4.90% and 26.09+/-6.36% respectively, with a median survival of 31 months (range 1-127 months). Fifty patients (39.1%) had progressed to acute leukemia (AL) with a median time of 8 months (range 1-43 months). Major independent variables indicated by multivariate analysis were the percentage of bone marrow (BM) blast cells and complex karyotype aberrations for survival (P=0.042 and 0.042, respectively) and only the percentage of BM blast cells for AL transformation (P=0.023). All the systems except Mufti scores successfully discriminated risk groups concerning both survival and AL evolution, especially in the high risk group, ranging from 10 to 20 months and from 4 to 7 months, respectively. The FAB and WHO classification, as well as Sanz, Oguma, Morel and IPSS possessed lower P value (P<0.0001) than that of the rest scoring systems. CONCLUSION: The patients in our study were younger than these of the Western population, whereas the survival and AL transformation ratio were comparable to these previous studies. The BM blast proportion and complex chromosomal defects were highly significant for predicting outcome in MDS patients. Most investigated systems effectively stratified patients into groups with different life expectancies and identified a subset of patients with poor clinical outcome. The FAB, WHO classification, as well as Sanz, Oguma, Morel and IPSS scoring systems were more applicable for predicting survival and leukemia progression.

Adolescent↗
PubMed2002

A novel mouse model of diisocyanate-induced asthma showing allergic-type inflammation in the lung after inhaled antigen challenge.

BACKGROUND: Exposure to diisocyanates, a group of highly reactive, low-molecular-weight compounds, is a major cause of occupational asthma. In contrast to mouse models of atopic asthma, previous mouse models of diisocyanate-induced asthma have failed to show lung inflammation with characteristics of human disease. OBJECTIVE: Our goal was to establish a novel mouse model of diisocyanate-induced asthma in which lung inflammation reminiscent of that seen in human asthma is generated after inhaled antigen challenge. METHODS: BALB/c mice were epicutaneously sensitized to hexamethylene diisocyanate (HDI) and then challenged with an HDI-protein conjugate administered by means of an intranasal droplet. RESULTS: HDI sensitization resulted in development of contact hypersensitivity and HDI-specific antibody production. Most importantly, however, vigorous inflammatory responses with characteristics of human asthma were generated in the lung after inhaled HDI challenge. Challenge of sensitized, but not unsensitized, mice resulted in airway eosinophilia, mucus hypersecretion, and production of T(H)1-type (IFN-gamma) and T(H)2-type (IL-4, IL-5, and IL-13) cytokines by lung inflammatory cells. Despite the mixed T(H)1/T(H)2 response induced by HDI sensitization, use of cytokine-deficient mice revealed that airway eosinophilia was mediated by T(H)2 cytokines and not by IFN-gamma. CONCLUSION: We report a novel mouse model of diisocyanate-induced asthma that, in contrast to previous models, demonstrates antigen-induced lung inflammation with characteristics of human disease. This model will allow investigation of the immunopathogenesis of diisocyanate-induced asthma and should provide insight into this common form of occupational disease.

Administration, Inhalation↗
PubMed2002

ES-2 Dummy Biomechanical Responses.

This technical paper presents the results of biomechanical testing conducted on the ES-2 dummy by the Occupant Safety Research Partnership and Transport Canada. The ES-2 is a production dummy, based on the EuroSID-1 dummy, that was modified to further improve testing capabilities as recommended by users of the EuroSID-1 dummy. Biomechanical response data were obtained by completing a series of drop, pendulum, and sled tests that are outlined in the International Organization of Standardization Technical Report 9790 that describes biofidelity requirements for the midsize adult male side impact dummy. A few of the biofidelity tests were conducted on both sides of the dummy to evaluate the symmetry of its responses. Full vehicle crash tests were conducted to verify if the changes in the EuroSID-1, resulting in the ES-2 design, did improve the dummy's testing capability. In addition to the biofidelity testing, the ES-2 dummy repeatability, reproducibility and durability are discussed. Finally, this technical paper will compare the biofidelity ratings of the current adult side impact dummies with the ES-2 dummy, which received an overall dummy biofidelity rating of 4.6.

Journal Article↗
PubMed2002

[Establishment and application of multiplex FISH in detection of the complex chromosome abnormalities in leukemia].

OBJECTIVE: To set up the technical system of multiplex fluorescence in situ hybridization M-FISH and to explore its application in detection of the complex chromosome abnormalities in leukemia. METHODS: The complex chromosome abnormalities of two leukemia patients were analyzed by the combination use of classical cytogenetics, chromosome painting (CP), FISH and M-FISH. RESULTS: In a case of acute lymphoblastic leukemia-L2, the complex karyotype: 46,XY,der(2)t(2;9),der(9)t(9;12;22) was identified by M-FISH, which was detected as 46,XY,der(9)t(9;12) by classical cytogenetics; In a case of acute monocytic leukemia-M5, the complex chromosome abnormalities: 46,XY,der(2)t(2;17), der(10)t(10;11;17), der(11)t(11;?) was revealed by M-FISH, which was confirmed by CP and FISH, and mixed lineage leukemia (MLL) gene was also found involved in this complex chromosome translocation. CONCLUSION: M-FISH was proved to be a powerful tool to examine the complicated karyotypes and hopefully to elucidate nearly all chromosomal aberrations in leukemia and other cancers.

Chromosome Aberrations↗
PubMed2002

[Role of the three-dimensional distribution of abl and bcr genes in the formation of bcr/abl fusion gene in interphase neucleus].

OBJECTIVE: To explore the mechanism of bcr/abl fusion gene formation in view of its biological stereology. METHODS: Assisted by fluorescent in situ hybridization combined with confocal laser scanning microscopy, we observed the effect of gamma-ray exposure on three-dimensional distribution of bcr and abl genes in the interphase nucleus of IM-9 cell line. RESULTS: In interphase nuclei of IM-9 cells, abl and bcr genes retained their own definite distribution patterns that were dynamically and regularly modulated along with the phases of the cell cycle. gamma-ray exposure, however, produced shortened distances between the 2 genes. CONCLUSION: The accessibility of abl and bcr genes to each other in the interphase nuclei is one of the factors for bcr/acl fusion gene formation.

Cell Cycle↗