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Ju-Chien Cheng

Publications and source records attributed to Ju-Chien Cheng.

9 recordsLinked to original sources
PubMed2006

Disabled-2 is a novel alphaIIb-integrin-binding protein that negatively regulates platelet-fibrinogen interactions and platelet aggregation.

Platelet aggregation plays a pivotal role in the haemostatic process and is involved in the pathological counterpart of arterial thrombosis. We have shown that the adapter protein disabled-2 (DAB2) is expressed abundantly in platelets. In this study, DAB2 was found to distribute in the platelet alpha-granules and was released from the granular compartment upon platelet activation. The secreted DAB2 binds to the extracellular region of alphaIIbbeta3 integrin on the platelet surface through the phosphotyrosine-binding domain. The DAB2-platelet interactions result in the inhibition of agonist-induced platelet aggregation with the exception of thrombin, a DAB2 protease that renders DAB2 inactive. Biochemical and mutational analysis revealed that the DAB2 cell-adhesion Arg-Gly-Asp (RGD) motif (amino acid residues 64-66) and the alphaIIb-integrin-fibrinogen-binding region (amino acid residues 171-464) are important for the DAB2-platelet interactions. Such interactions compete for the binding of alphaIIb integrin with fibrinogen and provide a mechanism for DAB2 to inhibit platelet aggregation. Accordingly, the synthetic RGD-motif-containing DAB2 peptide PDARGDKM also elicited anti-platelet aggregation activity. These findings demonstrate for the first time that DAB2 is an alphaIIb-integrin-binding protein that plays a novel role in the control of platelet-fibrinogen interactions and platelet aggregation.

Adaptor Proteins, Signal Transducing↗
PubMed2006

Rapid detection and identification of clinically important bacteria by high-resolution melting analysis after broad-range ribosomal RNA real-time PCR.

BACKGROUND: Broad-range PCR provides valuable information for detecting bacterial infections. This study assesses the combined use of broad-range real-time PCR and high-resolution melting analysis for rapid detection and identification of clinically important bacteria. METHODS: We subjected 46 bacterial culture colonies representing 25 clinically important bacterial species to LightCycler real-time PCR amplification of the 16S rRNA gene in the presence of LCGreen I fluorescent dye. We performed high-resolution melting analysis of the PCR products with the HR-1 instrument and used melting profiles as molecular fingerprints for bacterial species identification. We validated this method via assessment of 54 consecutive bacteria culture colonies obtained from a clinical microbiology laboratory. RESULTS: The 16S rRNA gene of all 25 bacterial species was amplifiable by this method, with PCR product lengths of 216 or 217 bp. Of the 25 bacterial species, we identified 11 via a 1-step post-PCR high-resolution melting analysis. The remaining bacterial species were identified via the high-resolution melting plots obtained by heteroduplex formation between the PCR products of the tested and reference bacterial species or by a 2nd real-time PCR targeting a different region of the 16S rRNA gene. A high-resolution melting database and a working protocol were established for identifying these 25 bacterial species. In the validation assay, a 94% accuracy rate was achieved when the bacterial species were in the high-resolution melting database. CONCLUSIONS: This assay requires no multiplexing or hybridization probes and provides a new approach for bacterial species identification in a molecular diagnostic laboratory.

Bacteria↗
PubMed2006

Quantitative assessment of serum NV-F virus DNA concentrations in samples from patients coinfected with hepatitis B or C virus.

A novel hepatotropic virus, named NV-F virus, was recently identified. The clinical information for this virus is still scarce. Using PCR assay, NV-F viral DNA (NV-F-DNA) was detected in 12 of 50 (24%) hepatitis C virus (HCV)-infected patients (HCV-coinfected [HCVCI] group), 34 of 250 (13.6%) hepatitis B virus (HBV)-infected patients (HBV-coinfected [HBVCI] group), and 28 of 100 (28%) non-A-to-E (NAE) hepatitis patients. Basic clinical parameters were not significantly different among the three groups. By use of a PCR-based quantitative assay, the NV-F-DNA concentration was found to be above the detection limit (1.2 x 10(5) copies/ml) in 12/12 (100%) HCVCI patients, 14/34 (41.2%) HBVCI patients, and 4/28 (14.3%) NAE patients. The median serum NV-F-DNA concentration was 9.3 x 10(5) copies/ml in HCVCI patients, but it was below the detection limit in HBVCI and NAE patients (P values were 0.0045 and 0.0001, respectively). Stepwise multiple regression analysis identified the presence of anti-HCV as an independent factor for NV-F-DNA concentrations (beta = 6.2 x 10(9); P = 0.0245). In HBVCI patients, the NV-F-DNA concentration was inversely correlated with the HBV DNA concentration. The median NV-F-DNA concentration was below the detection limit in patients with HBV DNA concentrations above 1.4 x 10(5) copies/ml, but it was 1.58 x 10(6) copies/ml in patients with HBV DNA concentrations below 1.4 x 10(5) copies/ml (P = 0.030). In conclusion, NV-F-DNA concentrations were higher in HCVCI patients. A reciprocal relationship was found between NV-F-DNA and HBV DNA concentrations in HBVCI patients, indicating the presence of viral interference between these two DNA viruses.

Adult↗
PubMed2005

Independent association between triglycerides and coronary artery disease in Taiwanese type 2 diabetic patients.

BACKGROUND: This study evaluated the association between triglycerides (TG) and coronary artery disease (CAD) in Taiwanese adults with type 2 diabetes mellitus (T2DM). METHODS: A total of 1150 patients (542 men and 608 women) aged 62.5+/-11.6 years were studied. CAD was diagnosed by history or an abnormal electrocardiogram (coronary probable or possible by Minnesota codes). Age, body mass index (BMI), smoking, use of insulin, anti-hypertensive agents and lipid-lowering agents, fasting plasma glucose (FPG), hemoglobin A1c (HbA1c), systolic blood pressure (SBP), diastolic blood pressure (DBP), serum total cholesterol (TC), high-density lipoprotein cholesterol (HDL-c) and low-density lipoprotein cholesterol (LDL-c) were considered as potential confounders. RESULTS: Patients with CAD were older, had higher prevalences of use of anti-hypertensive and lipid-lowering agents, and had higher BMI, SBP, DBP and TG. CAD increased significantly with increasing quartiles of TG (P-trend < 0.001). Ln(TG) was significantly correlated with BMI, FPG, HbA1c, DBP, TC, HDL-c (inversely) and LDL-c. Ln(TG) was associated with CAD with an unadjusted odds ratio of 1.411 (1.145-1.740). The odds ratio after adjustment for all confounders was slightly attenuated but still statistically significant: 1.380 (1.043-1.826). None of the other lipid parameters of TC, HDL-c and LDL-c were significantly associated with CAD in logistic models when they were entered for adjustment either separately or simultaneously. Sensitivity analyses by using history alone or history and coronary probable as diagnostic criteria for CAD did not change the association between TG and CAD. CONCLUSIONS: TG is an independent risk factor for CAD in Taiwanese T2DM, independent of TC, HDL-c, LDL-c or other confounders.

Aged↗
PubMed2005

Autocrine signaling of platelet-derived growth factor regulates disabled-2 expression during megakaryocytic differentiation of K562 cells.

Platelet-derived growth factor (PDGF) is involved in megakaryocytopoiesis and is secreted into the culture medium during megakaryocytic differentiation of human leukemic cells. We investigate whether PDGF plays a role in the regulation of the adapter protein Disabled-2 (DAB2) that expresses abundantly in platelets and megakaryocytes. Western blot analysis revealed that conditioned medium from 12-O-tetradecanoylphorbol-13-acetate (TPA)-treated, megakaryocytic differentiating K562 cells upregulated DAB2 expression. DAB2 induction and megakaryocytic differentiation was abrogated when cells were co-treated with the PDGF receptor inhibitor STI571 or when the conditioned medium was derived from TPA-plus STI571-treated cells. Although the level of PDGF mRNA was not altered by STI571, an approximate 44% decrease in PDGF in the conditioned medium was observed. Consistent with these findings, interfering PDGF signaling by PDGF neutralization antibody or dominant negative PDGF receptors attenuated DAB2 expression. Accordingly, transfection of an expression plasmid encoding secreted PDGF upregulated DAB2. This study shows for the first time that PDGF autocrine signaling regulates DAB2 expression during megakaryocytic differentiation.

Adaptor Proteins, Signal Transducing↗
PubMed2005

A gene cluster for the fatty acid catabolism from Pseudonocardia autotrophica BCRC12444.

Genes involved in fatty acid degradation (fad) were isolated from Pseudonocardia autotrophica BBRC12444. Six open reading frames and a bi-directional promoter region were identified by DNA sequence analyses and primer extension. The fad gene cluster included five ORFs, designated fadA, fadB, fadR, fadC, and fadD. Base on their amino acid sequence identity, the gene products were identified as acyl-CoA ligase (FadA), enoyl-CoA hydratase (FadB), transcriptional regulator (FadR), cytochrome P450 monooxygenase (FadC), and ferredoxin (FadD). Regulatory protein, FadR, could bind to an operator sequence located in the divergent promoter region between fadR and fadC genes, implicating the control of fatty acid degradation. The real-time quantitative PCR assays revealed that the expression of the fadA, fadB, fadR, and fadC genes was induced by long chain fatty acids and repressed by glucose. All results demonstrated that the fad gene cluster participated in the pathway of the fatty acid catabolism. This is the first bacterial fad gene cluster to be reported.

Actinomycetales↗
PubMed2004

Disabled-2 is a negative regulator of integrin alpha(IIb)beta(3)-mediated fibrinogen adhesion and cell signaling.

Disabled-2 (DAB2) is an adapter protein that is up-reg-ulated during megakaryocytic differentiation of hematopoietic cells and is abundantly expressed in platelets. In this study, the role of DAB2 in integrin alpha(IIb)beta(3)-mediated matrix protein fibrinogen adhesion and cell signaling was investigated. In K562 cells differentiating to the megakaryocytic lineage, down-regulation of DAB2 by DAB2 small interfering RNA augmented integrin alpha(IIb)beta(3) activation and resulted in an increase in cell adhesion to fibrinogen. Ectopic expression of DAB2 reversed the DAB2 small interfering RNA effect or, by itself, decreased fibrinogen adhesion of K562 cells. Mutational analysis revealed that a DAB2 Ser(24) phosphorylation mutant (S24A) abrogated the inhibitory function of DAB2. The spatial and temporal association/interaction of DAB2 and platelet integrin alpha(IIb)beta(3) (CD61) in both megakaryocytic cells and platelets led us to examine the effect of Ser(24) phosphorylation on the interaction between DAB2 and integrin beta(3). Through cellular localization and co-immunoprecipitation analysis, we demonstrate for the first time that Ser(24) phosphorylation promotes membrane translocation of DAB2 and its subsequent interaction with integrin beta(3), thereby defining a mechanism for DAB2 in regulating integrin alpha(IIb)beta(3) activation and inside-out signaling. Consistent with the effect on fibrinogen adhesion, Ser(24) phosphorylation of DAB2 was also involved in the negative regulation of alpha(IIb)beta(3)-induced T cell factor transcriptional activity. In contrast, the S24A mutant acted like wild-type DAB2 and inhibited both beta-catenin- and plakoglobin-mediated T cell factor transactivation. Hence, DAB2 elicits distinct regulatory mechanisms in alpha(IIb)beta(3) and beta-catenin/plakoglobin signaling in a Ser(24) phosphorylation-dependent and -independent manner, respectively. These findings indicate Ser(24) phosphorylation as a molecular basis for DAB2 acting as a negative regulator in alpha(IIb)beta(3) inside-out signaling and contribute to our understanding of DAB2 in megakaryocytic differentiation and platelet function.

Adaptor Proteins, Signal Transducing↗
PubMed2003

Disabled-2 small interfering RNA modulates cellular adhesive function and MAPK activity during megakaryocytic differentiation of K562 cells.

Previous studies have shown that Disabled-2 (DAB2) is up-regulated during megakaryocytic differentiation of human K562 cells. To delineate the consequences of DAB2 induction, a DNA vector-based small interfering RNA (siRNA) was designed to intervene in DAB2 expression. We found that DAB2 siRNA specifically inhibited DAB2 induction, resulting in the modulation of cell-cell adhesion and mitogen-activated protein kinase (MAPK) phosphorylation. The morphological changes and beta3 integrin expression associated with megakaryocytic differentiation were not affected. Since the MAPK pathway has been shown to involve DAB2 induction [Tseng et al., Biochem. Biophys. Res. Commun. 285 (2001) 129-135], our results suggest a reciprocal regulation between DAB2 and MAPK in the differentiation of K562 cells. In addition, we have demonstrated for the first time that DAB2 siRNA is a valuable tool for unveiling the biological consequences of DAB2 expression.

Adaptor Proteins, Signal Transducing↗