Biomedical subjects

Hao Wu

Publications and source records attributed to Hao Wu.

At least 37 records · Page 2Linked to original sources

PubMed2006

Caspase-9 holoenzyme is a specific and optimal procaspase-3 processing machine.

Caspase-9 activation is critical for intrinsic cell death. The activity of caspase-9 is increased dramatically upon association with the apoptosome, and the apoptosome bound caspase-9 is the caspase-9 holoenzyme (C9Holo). In this study, we use quantitative enzymatic assays to fully characterize C9Holo and a leucine-zipper-linked dimeric caspase-9 (LZ-C9). We surprisingly show that LZ-C9 is more active than C9Holo for the optimal caspase-9 peptide substrate LEHD-AFC but is much less active than C9Holo for the physiological substrate procaspase-3. The measured Km values of C9Holo and LZ-C9 for LEHD-AFC are similar, demonstrating that dimerization is sufficient for catalytic activation of caspase-9. The lower activity of C9Holo against LEHD-AFC may be attributed to incomplete C9Holo assembly. However, the measured Km of C9Holo for procaspase-3 is much lower than that of LZ-C9. Therefore, in addition to dimerization, the apoptosome activates caspase-9 by enhancing its affinity for procaspase-3, which is important for procaspase-3 activation at the physiological concentration.

Animals↗

PubMed2006

Elongation factor-2 kinase regulates autophagy in human glioblastoma cells.

Elongation factor-2 kinase (eEF-2 kinase), also known as Ca(2+)/calmodulin-dependent kinase III, regulates protein synthesis by controlling the rate of peptide chain elongation. The activity of eEF-2 kinase is increased in glioblastoma and other malignancies, yet its role in neoplasia is uncertain. Recent evidence suggests that autophagy plays an important role in oncogenesis and that this can be regulated by mammalian target of rapamycin (mTOR). Because eEF-2 kinase lies downstream of mTOR, we studied the role of eEF-2 kinase in autophagy using human glioblastoma cell lines. Knockdown of eEF-2 kinase by RNA interference inhibited autophagy in glioblastoma cell lines, as measured by light chain 3 (LC3)-II formation, acidic vesicular organelle staining, and electron microscopy. In contrast, overexpression of eEF-2 kinase increased autophagy. Furthermore, inhibition of autophagy markedly decreased the viability of glioblastoma cells grown under conditions of nutrient depletion. Nutrient deprivation increased eEF-2 kinase activity and decreased the activity of S6 kinase, suggesting an involvement of mTOR pathway in the eEF-2 kinase regulation of autophagy. These results suggest that eEF-2 kinase plays a regulatory role in the autophagic process in tumor cells; and eEF-2 kinase is a downstream member of the mTOR signaling; eEF-2 kinase may promote cancer cell survival under conditions of nutrient deprivation through regulating autophagy. Therefore, eEF-2 kinase may be a part of a survival mechanism in glioblastoma and targeting this kinase may represent a novel approach to cancer treatment.

Autophagy↗

PubMed2006

Cytoplasmic male sterility of rice with boro II cytoplasm is caused by a cytotoxic peptide and is restored by two related PPR motif genes via distinct modes of mRNA silencing.

Cytoplasmic male sterility (CMS) and nucleus-controlled fertility restoration are widespread plant reproductive features that provide useful tools to exploit heterosis in crops. However, the molecular mechanism underlying this kind of cytoplasmic-nuclear interaction remains unclear. Here, we show in rice (Oryza sativa) with Boro II cytoplasm that an abnormal mitochondrial open reading frame, orf79, is cotranscribed with a duplicated atp6 (B-atp6) gene and encodes a cytotoxic peptide. Expression of orf79 in CMS lines and transgenic rice plants caused gametophytic male sterility. Immunoblot analysis showed that the ORF79 protein accumulates specifically in microspores. Two fertility restorer genes, Rf1a and Rf1b, were identified at the classical locus Rf-1 as members of a multigene cluster that encode pentatricopeptide repeat proteins. RF1A and RF1B are both targeted to mitochondria and can restore male fertility by blocking ORF79 production via endonucleolytic cleavage (RF1A) or degradation (RF1B) of dicistronic B-atp6/orf79 mRNA. In the presence of both restorers, RF1A was epistatic over RF1B in the mRNA processing. We have also shown that RF1A plays an additional role in promoting the editing of atp6 mRNAs, independent of its cleavage function.

Amino Acid Motifs↗

PubMed2006

The ups and downs of BDNF in Rett syndrome.

Rett syndrome (RTT) is an X-linked postnatal neurodevelopmental disorder, which is primarily caused by mutations in the gene encoding methyl-CpG binding protein 2 (MeCP2). A number of MeCP2 target genes have been identified, including the neurotrophic factor BDNF; however, the functional relevance of these targets has not been established. In this issue of Neuron, Chang et al. provide the first in vivo evidence for a functional interaction between BDNF and MeCP2.

Animals↗

PubMed2006

Coupling of cell migration with neurogenesis by proneural bHLH factors.

After cell birth, almost all neurons in the mammalian central nervous system migrate. It is unclear whether and how cell migration is coupled with neurogenesis. Here we report that proneural basic helix-loop-helix (bHLH) transcription factors not only initiate neuronal differentiation but also potentiate cell migration. Mechanistically, proneural bHLH factors regulate the expression of genes critically involved in migration, including down-regulation of RhoA small GTPase and up-regulation of doublecortin and p35, which, in turn, modulate the actin and microtubule cytoskeleton assembly and enable newly generated neurons to migrate. In addition, we report that several DNA-binding-deficient proneural genes that fail to initiate neuronal differentiation still activate migration, whereas a different mutation of a proneural gene that causes a failure in initiating cell migration still leads to robust neuronal differentiation. Collectively, these data suggest that transcription programs for neurogenesis and migration are regulated by bHLH factors through partially distinct mechanisms.

Actins↗

PubMed2006

Crystal structure of RAIDD death domain implicates potential mechanism of PIDDosome assembly.

Caspase-2 is implicated in stress-induced apoptosis that acts as an upstream initiator of mitochondrial permeabilization. Recent studies have shown that caspase-2 activation requires a molecular complex known as the PIDDosome comprising the p53-inducible protein PIDD, the adapter protein RAIDD and caspase-2. RAIDD has an N-terminal caspase recruitment domain (CARD) that interacts with the CARD of caspase-2 and a C-terminal death domain (DD) that interacts with the DD in PIDD. As a first step towards elucidating the molecular mechanisms of caspase-2 activation, we report the crystal structure of RAIDD DD at 2.0 A resolution. The high-resolution structure reveals important features of RAIDD DD that may be important for DD folding and dynamics and for assembly of the PIDDosome.

Adaptor Proteins, Signal Transducing↗

PubMed2006

A Psb27 homologue in Arabidopsis thaliana is required for efficient repair of photodamaged photosystem II.

Psb27 has been identified as a lumenal protein associated with photosystem II (PSII). To gain insight into the function of Psb27, we isolated a mutant Arabidopsis plant with a loss of psb27 function. The quantity of PSII complexes and electron transfer within PSII remained largely unaffected in the psb27 mutant. Our results also showed that under high-light-illumination, PSII activity and the content of the PSII reaction center protein D1 decreased more significantly in the psb27 mutant than in wild-type (WT) plant. Treatment of leaves with a chloroplast protein synthesis inhibitor resulted in similar light-induced PSII inactivation levels and D1 protein degradation rates in the WT and psb27 mutant plants. Recovery of PSII activity after photoinhibition was delayed in the psb27 mutant, suggesting that Psb27 is required for efficient recovery of the photodamaged PSII complex. Overall, these results demonstrated that Psb27 in Arabidopsis is not essential for oxygenic photosynthesis and PSII formation. Instead, our results provide evidence for the involvement of this lumenal protein in the recovery process of PSII.

Arabidopsis↗

PubMed2006

Native chemical ligation in covalent caspase inhibition by p35.

Wide-spectrum caspase inhibition by the baculoviral p35 protein was previously shown to be a consequence of covalent inhibition in which a thioester bond is stably formed between the cleavage residue Asp87 of p35 and the active site Cys360' of caspase-8. Here we show that the N-terminal fragment of cleaved p35 (p35-N) is a circular peptide when dissociated from the caspase. Biochemical and crystallographic data suggest that p35-N circularization results from the trapping of a native chemical ligation intermediate in the p35/caspase complex, in which the N-terminal Cys2 of p35 attacks the Asp87-Cys360' thioester to form an equilibrium between Asp87-Cys2 and Asp87-Cys360'. This provides a crucial covalent interaction for keeping the N terminus of p35 bound in the caspase active site, which explains the absolute requirement of Cys2 for caspase inhibition. Participation of native chemical ligation in caspase inhibition by p35 illustrates an unusual mechanism of protease inhibition.

Aspartic Acid↗

PubMed2006

Neural progenitors populate the cerebrospinal fluid of preterm patients with hydrocephalus.

OBJECTIVES: To evaluate cerebrospinal fluid (CSF) of preterm patients with hydrocephalus for neural progenitors. STUDY DESIGN: This report describes a prospective study of CSF obtained from preterm infants, either with progressive posthemorrhagic hydrocephalus (PPHH) or without known intercranial pathology. Cells recovered by centrifugation were analyzed by reverse transcriptase-polymerase chain reaction or by immunocytometry. Alternatively, cells were cultured by using methods permissive to neural progenitor growth and analyzed by immunocytochemistry and Western blotting. RESULTS: Human CSF cells were obtained from 20 preterm infants at approximately 27 weeks estimated gestational age (15 infants with PPHH, 5 control infants). The number of these cells removed over time from patients with PPHH were substantial, based on our calculations. Cells recovered from patients with PPHH transcribe markers for neural progenitors, all the mature cells types of the central nervous system, and a large battery of chondroitin sulfate proteoglycan genes, including the entire aggrecan/lectican family. These cells proliferated in culture, and precursor markers were detected by Western blotting, immunocytochemistry, and cytometry. Cells could not be cultured from control patients. CONCLUSIONS: Neural progenitor accumulation in CSF could confound the clinical interpretation of CSF cell counts in hydrocephalus and may play as yet undetermined roles in the biology of injury after hydrocephalus. These findings suggest the potential for neural stem cell propagation from CSF.

Biomarkers↗

PubMed2006

The KSHV oncoprotein vFLIP contains a TRAF-interacting motif and requires TRAF2 and TRAF3 for signalling.

Primary effusion lymphomas (PELs) characterized by infection with the Kaposi's sarcoma herpesvirus (KSHV; also called human herpesvirus 8) depend on the expression of the viral FADD-like interleukin-1-beta-converting enzyme (FLICE)/caspase-8-inhibitory protein (vFLIP) for their survival. This effect is achieved by activation of the transcription factor nuclear factor-kappaB (NF-kappaB). Tumour necrosis factor (TNF) receptor-associated factors (TRAFs) are direct mediators of NF-kappaB signalling by TNF family receptors and the Epstein-Barr virus oncoprotein latent membrane protein 1 and so we assessed the role of TRAFs in signalling by vFLIP. Here, we report the identification of a TRAF-interacting motif (PYQLT) in vFLIP, which is not present in other FLIP molecules. We show that vFLIP directly binds to TRAF2 in vitro and in PEL cells. TRAF2 and TRAF3 are required for induction of NF-kappaB and associated cell survival, as well as Jun amino-terminal kinase phosphorylation by vFLIP, whereas TRAF1, TRAF5 and TRAF6 are dispensable. Mutations in the P93 or Q95 amino acids within the TRAF-interacting motif of vFLIP abolish its ability to bind to TRAF2 and to signal to NF-kappaB. TRAF2, but not TRAF3, mediates the association of vFLIP with the IkappaB kinase complex. These data indicate that vFLIP uses TRAF2 and TRAF3 for signalling to NF-kappaB, which is crucial for KSHV-associated lymphomagenesis.

Animals↗

PubMed2006

Characterization of the gp120 of circulating HIV type 1 in a group of infected Chinese blood/plasma donors with asymptomatic and symptomatic stages of the disease.

The C2-V5 regions of the HIV envelope gene were cloned and sequenced from DNA samples of four asymptomatic and five AIDS patients from a cohort of HIV-1-infected Chinese plasma and blood donors. Sequence analysis revealed that regardless of the stage of disease, all the patient's HIV-1 belonged to either clade B' or circulating recombinant form 15 (CRF15) subtype. However, since these blood donors were infected at a time when circulating CRF15 was not known in that region, it is likely these HIV-1 types belong to clade B'. However, the C2-V5 sequences from AIDS patients clustered differently in the phylogenetic tree than those present in asymptomatic patients and showed a significantly higher divergence and lower diversity compared to those from asymptomatic patients. In addition, more syncytia-inducing viral genotypes were present in AIDS patients than in asymptomatic patients. These results contribute to a better understanding of the pathogenesis of circulating HIV-1 in infected Chinese plasma and blood donors, warrant additional investigation of the possible presence of CRF15 in Chinese blood donors, and may have important implications in the future design of therapeutic strategies for treating these infected patients.

Asian People↗

PubMed2006

A new way for multidimensional medical data management: volume of interest (VOI)-based retrieval of medical images with visual and functional features.

The advances in digital medical imaging and storage in integrated databases are resulting in growing demands for efficient image retrieval and management. Content-based image retrieval (CBIR) refers to the retrieval of images from a database, using the visual features derived from the information in the image, and has become an attractive approach to managing large medical image archives. In conventional CBIR systems for medical images, images are often segmented into regions which are used to derive two-dimensional visual features for region-based queries. Although such approach has the advantage of including only relevant regions in the formulation of a query, medical images that are inherently multidimensional can potentially benefit from the multidimensional feature extraction which could open up new opportunities in visual feature extraction and retrieval. In this study, we present a volume of interest (VOI) based content-based retrieval of four-dimensional (three spatial and one temporal) dynamic PET images. By segmenting the images into VOIs consisting of functionally similar voxels (e.g., a tumor structure), multidimensional visual and functional features were extracted and used as region-based query features. A prototype VOI-based functional image retrieval system (VOI-FIRS) has been designed to demonstrate the proposed multidimensional feature extraction and retrieval. Experimental results show that the proposed system allows for the retrieval of related images that constitute similar visual and functional VOI features, and can find potential applications in medical data management, such as to aid in education, diagnosis, and statistical analysis.

Algorithms↗

PubMed2006

Functional expression of the particulate methane mono-oxygenase gene in recombinant Rhodococcus erythropolis.

In order to construct an expression system for the particulate methane mono-oxygenase (pMMO) gene (pmo), the structural gene cluster pmoCAB amplified from Methylosinus trichosporium OB3b was inserted into a shuttle vector pBS305 under the control of a dsz promoter and transformed into Rhodococcus erythropolis LSSE8-1. A stable transformant was successfully obtained using ethane as the sole carbon source. Fluorescence in situ hybridization results showed that the dsz promoter allowed the pmo genes to be transcribed in the recombinant strain. The effects of Cu2+ and Zn2+ concentrations on cell growth and pMMO activity in ethane-containing medium were examined. It was discovered that 7.5 microM Cu2+ and 1.8 microM Zn2+ were suitable to achieve high cell concentration and pMMO activity, but the amount of methanol accumulated during methane oxidation by the recombinant strain was still low.

DNA, Bacterial↗

PubMed2006

Identification of a novel alpha-galactosidase from the hyperthermophilic archaeon Sulfolobus solfataricus.

Sulfolobus solfataricus is an aerobic crenarchaeon that thrives in acidic volcanic pools. In this study, we have purified and characterized a thermostable alpha-galactosidase from cell extracts of S. solfataricus P2 grown on the trisaccharide raffinose. The enzyme, designated GalS, is highly specific for alpha-linked galactosides, which are optimally hydrolyzed at pH 5 and 90 degrees C. The protein consists of 74.7-kDa subunits and has been identified as the gene product of open reading frame Sso3127. Its primary sequence is most related to plant enzymes of glycoside hydrolase family 36, which are involved in the synthesis and degradation of raffinose and stachyose. Both the galS gene from S. solfataricus P2 and an orthologous gene from Sulfolobus tokodaii have been cloned and functionally expressed in Escherichia coli, and their activity was confirmed. At present, these Sulfolobus enzymes not only constitute a distinct type of thermostable alpha-galactosidases within glycoside hydrolase clan D but also represent the first members from the Archaea.

Enzyme Activation↗

PubMed2006

Pharmacokinetics of puerarin and ginsenoside Rg1 of CBN injection and the relation with platelet aggregation in rats.

In order to study the pharmacokinetics of puerarin and ginsenoside Rg1 of cerebral blood nutrition (CBN) and its relationship with pharmacodynamics of platelet aggregation induced by ADP in rat, the blood samples after injection were collected. The concentrations of puerarin and ginsenoside Rg1 in plasma were determined by RP-HPLC, and the platelet aggregations were observed simultaneously. The data showed that there was distinct statistic significance (p < 0.01) for puerarin processing, which was a single compartment model with quick elimination rate (t(1/2beta) = 18 min) and MRT (26 min), while ginsenoside Rg1 processing was a double compartment model with rapid distribution rate (t(1/2alpha) = 8 min), slow elimination rate (t(1/2beta) = 11 hours) and MRT (3.3 hours). Effects of anti-platelet aggregation were presented at 5-10 min, 45-90 min and 6-8 hours after injection separately, and the corresponding concentrations of puerarin were 25-21 microg/ml, 4.5-0.8 microg/ml and 0 microg/ml, ginsenoside Rg1 were 7.6-6.7 microg/ml, 1.2-0.6 microg/ml and 1.8-0.5 microg/ml. The two components presented a positive correlation between their concentrations and the effect of anti-platelet aggregation in 5-10 min after CBN injection (coefficient of correlation were 0.999 and 0.995). However, it was noted that the effect was still stronger even when concentrations of puerarin and ginsenoside Rg1 in plasma decreased. Therefore, puerarin and ginsenoside Rg1 not only had different pharmacokinetics, but also had a positive correlation with platelet aggregation, just in 5-10 min after CBN injection.

Animals↗

PubMed2006

Epigenetic regulation of stem cell differentiation.

Stem cells undergo extensive self-renewal and have the capacity to differentiate along multiple cell lineages. Progression from stem cells into differentiated progeny requires long-lasting changes in gene expression. Epigenetic mechanisms, including DNA methylation, histone modifications, and non-coding RNA-mediated regulatory events, are essential to controlling the heritable cellular memory of gene expression during development. Recent studies on cell fate specification of embryonic and adult stem cells/progenitors have highlighted a general and critical role for dynamic epigenetic regulation in stem cell self-renewal and differentiation.

Adult↗

PubMed2006

Effect of Lycium barbarum polysaccharide on the improvement of antioxidant ability and DNA damage in NIDDM rats.

The effects of polysaccharide extracted from Lycium barbarum (LBP) on blood glucose, oxidative stress and DNA damage in rats with non-insulin dependent diabetes mellitus (NIDDM) were studied. The results show that LBP treatment (10 mg/kg.d) for 4 weeks led to decreased levels of blood glucose, malondialdehyde (MDA) and nitric oxide (NO) in serum of fasting rats; and to increased serum level of superoxidedismutase (SOD). Furthermore, LBP could reduce cellular DNA damage in peripheral lymphocytes of NIDDM rats. The DNA damage was determined by using the single cell gel (comet) assay with alkaline electrophoresis and was quantified by measuring tail length and tail moment. These results suggest that LBP can control blood glucose and modulate the metabolism of glucose, leading to significant improvement of oxidative stress markers (SOD, MDA) in rats with NIDDM. And that, LBP decreases DNA damage possibly via a decrease in oxidative stress levels. In conclusion, LBP as a dietary supplement may prevent the development of complications or even tendency to carcinogenesis in NIDDM rats.

Animals↗

PubMed2006

[Differential diagnosis of benign and malignant solitary pulmonary nodule with computer-aided detection].

OBJECTIVE: To investigate the morphological features of benign and malignant solitary pulmonary nodules (SPNs) and explore the radiological evidences for the differentiation of SPNs. METHODS: With SPN Dicom View software, we analyzed and compared images obtained from 23 patients with malignant SPNs and 22 patients with benign SPNs who received CT scanning with or without contrast medium injection. RESULTS: The enhancement in malignant SPNs group was significantly higher than in the benign SPNs group (P < 0.0001). The irregular enhancement in malignant SPNs group was significantly higher than in the benign SPNs group (P = 0. 0084). The mean range of enhancement was (45.04 +/- 26.76) HU in malignant SPNs group, which was significantly higher than that in the benign SPNs group [(15.70 +/- 17.84) HU, P = 0.033]. The mean peak enhancement value was (136.09 +/- 41.72) HU in malignant SPNs group, which was significantly higher than in benign SPNs group [ (60.60 +/- 60.27) HU, P = 0.007]. The mean enhancement area was (21.69 +/- 21.01)% in malignant SPNs group and (8.61 +/- 10.83)% in benign SPNs group (P = 0.203). CONCLUSION: The enhancement range and peak enhancement value as well as the morphologically irregular enhancement of SPNs may provide useful information in the clinical radiological diagnosis of SPNs.

Adult↗