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Biomedical subjects

Wei Li

Publications and source records attributed to Wei Li.

At least 145 records · Page 8Linked to original sources
PubMed2006

Antithrombin-S195A factor Xa-heparin structure reveals the allosteric mechanism of antithrombin activation.

Regulation of blood coagulation is critical for maintaining blood flow, while preventing excessive bleeding or thrombosis. One of the principal regulatory mechanisms involves heparin activation of the serpin antithrombin (AT). Inhibition of several coagulation proteases is accelerated by up to 10,000-fold by heparin, either through bridging AT and the protease or by inducing allosteric changes in the properties of AT. The anticoagulant effect of short heparin chains, including the minimal AT-specific pentasaccharide, is mediated exclusively through the allosteric activation of AT towards efficient inhibition of coagulation factors (f) IXa and Xa. Here we present the crystallographic structure of the recognition (Michaelis) complex between heparin-activated AT and S195A fXa, revealing the extensive exosite contacts that confer specificity. The heparin-induced conformational change in AT is required to allow simultaneous contacts within the active site and two distinct exosites of fXa (36-loop and the autolysis loop). This structure explains the molecular basis of protease recognition by AT, and the mechanism of action of the important therapeutic low-molecular-weight heparins.

Allosteric Regulation↗
PubMed2006

Effects of heat shock protein gp96 on human dendritic cell maturation and CTL expansion.

We reported previously that heat shock protein gp96 and its N-terminal fragment were able to stimulate CTL expansion specific for a HBV peptide (SYVNTNMGL) in BALB/c mice. Here we characterized the adjuvant effects of gp96 on human HLA-A2 restricted T cells. Full-length gp96 isolated from healthy human liver and recombinant fragments both from prokaryotic cells and eukaryotic cells were analyzed for their ability to stimulate maturation of human dendritic cells. It was found that in vitro these proteins were capable of maturating human monocyte-derived dendritic cells (MDDC) isolated from healthy donors as well as from HBV-positive, hepatocellular carcinoma (HCC) patients. In HLA-A2.1/Kb transgenic mice, gp96 and the recombinant fragments were found to augment CTL response specific for the HBcAg(18-27) FLPSDFFPSV peptide of hepatitis B virus.

Animals↗
PubMed2006

Expression and characterization of full-length human huntingtin, an elongated HEAT repeat protein.

Huntington disease is an inherited neurodegenerative disorder that is caused by expanded CAG trinucleotide repeats, resulting in a polyglutamine stretch of >37 on the N terminus of the protein huntingtin (htt). htt is a large (347 kDa), ubiquitously expressed protein. The precise functions of htt are not clear, but its importance is underscored by the embryonic lethal phenotype in htt knock-out mice. Despite the fact that the htt gene was cloned 13 years ago, little is known about the properties of the full-length protein. Here we report the expression and preliminary characterization of recombinant full-length wild-type human htt. Our results support a model of htt composed entirely of HEAT repeats that stack to form an elongated superhelix.

Animals↗
PubMed2006

A C. elegans stretch receptor neuron revealed by a mechanosensitive TRP channel homologue.

The nematode Caenorhabditis elegans is commonly used as a genetic model organism for dissecting integration of the sensory and motor systems. Despite extensive genetic and behavioural analyses that have led to the identification of many genes and neural circuits involved in regulating C. elegans locomotion behaviour, it remains unclear whether and how somatosensory feedback modulates motor output during locomotion. In particular, no stretch receptors have been identified in C. elegans, raising the issue of whether stretch-receptor-mediated proprioception is used by C. elegans to regulate its locomotion behaviour. Here we have characterized TRP-4, the C. elegans homologue of the mechanosensitive TRPN channel. We show that trp-4 mutant worms bend their body abnormally, exhibiting a body posture distinct from that of wild-type worms during locomotion, suggesting that TRP-4 is involved in stretch-receptor-mediated proprioception. We show that TRP-4 acts in a single neuron, DVA, to mediate its function in proprioception, and that the activity of DVA can be stimulated by body stretch. DVA both positively and negatively modulates locomotion, providing a unique mechanism whereby a single neuron can fine-tune motor activity. Thus, DVA represents a stretch receptor neuron that regulates sensory-motor integration during C. elegans locomotion.

Animals↗
PubMed2006

Five mutations of ATP2A2 gene in Chinese patients with Darier's disease and a literature review of 86 cases reported in China.

Darier's disease (DD) is an autosomal dominantly inherited skin disorder characterized by loss of adhesion between epidermal cells (acantholysis) and abnormal keratinization. To date, at least 140 mutations in the ATP2A2 gene have been identified as the genetic basis of DD. Here we reported three familial and two sporadic Chinese DD patients totally with four missense mutations (N767D, M494I, M494L, C318F) and one splice-site mutation (1288-6A-->G) in ATP2A2 gene, and presented a literature review of DD cases reported in China since 1989. Our data add new variants to the repertoire of ATP2A2 gene in DD and confirms that most mutations in the ATP2A2 gene are private and missense type. Likewise, the literature review indicates that DD is not uncommon in China and presents more information about genotype-phenotype correlations.

Asian People↗
PubMed2006

3D-QSAR studies of orvinol analogs as kappa-opioid agonists.

Orvinols are potent analgesics that target opioid receptors. However, their analgesic mechanism remains unclear and no significant preference for subtype opioid receptor has been achieved. In order to find new orvinols that target the kappa-receptor, comparative 3D-QSAR studies were performed on 26 orvinol analogs using comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA). The best predictions for the kappa-receptor were obtained with the CoMFA standard model (q2 = 0.686, r2 = 0.947) and CoMSIA model combined steric, electrostatic, hydrophobic, and hydrogen bond donor/acceptor fields (q2 = 0.678, r2 = 0.914). The models built were further validated by a test set made up of seven compounds, leading to predictive r2 values of 0.672 for CoMFA and 0.593 for CoMSIA. The study could be helpful for designing and prepare new category kappa-agonists from orvinols.

Analgesics, Opioid↗
PubMed2006

A "traffic control" role for TGFbeta3: orchestrating dermal and epidermal cell motility during wound healing.

Cell migration is a rate-limiting event in skin wound healing. In unwounded skin, cells are nourished by plasma. When skin is wounded, resident cells encounter serum for the first time. As the wound heals, the cells experience a transition of serum back to plasma. In this study, we report that human serum selectively promotes epidermal cell migration and halts dermal cell migration. In contrast, human plasma promotes dermal but not epidermal cell migration. The on-and-off switch is operated by transforming growth factor (TGF) beta3 levels, which are undetectable in plasma and high in serum, and by TGFbeta receptor (TbetaR) type II levels, which are low in epidermal cells and high in dermal cells. Depletion of TGFbeta3 from serum converts serum to a plasmalike reagent. The addition of TGFbeta3 to plasma converts it to a serumlike reagent. Down-regulation of TbetaRII in dermal cells or up-regulation of TbetaRII in epidermal cells reverses their migratory responses to serum and plasma, respectively. Therefore, the naturally occurring plasma-->serum-->plasma transition during wound healing orchestrates the orderly migration of dermal and epidermal cells.

Activin Receptors, Type I↗
PubMed2006

Angiopoietin-1 promotes functional neovascularization that relieves ischemia by improving regional reperfusion in a swine chronic myocardial ischemia model.

This study investigates the long-term angiogenic effects of ANG-1 and VEGF in a swine chronic myocardial ischemia model. Four-weeks after gradual occlusion of the left circumflex coronary artery by ameroid constrictor, animals were injected with recombinant adenoviral vectors carrying either human ANG-1 (n=9), human VEGF(165) (n=10) or empty vector (n=7) into the left ventricle free wall supplied by the constricted artery. Left ventricular perfusion in animals that received AdANG-1 (3.25+/-0.16 ml/min/g, p<0.05) recovered robustly 4 weeks after gene transfer while ischemia persisted in the AdVEGF (1.09+/-0.13 ml/min/g) and empty vector (1.20+/-0.03 ml/min/g) groups. Microvascular densities in the left ventricles of animals that received AdANG-1 (19.61+/-1.76/0.572 mm(2) myocardial tissue, p<0.05) and AdVEGF (18.17+/-1.43/0.572 mm(2) myocardial tissue, p<0.05) were significantly higher than animals that received empty vector (13.53+/-0.92/0.572 mm(2) myocardial tissue) 12 weeks after gene transfer. ANG-1, but not VEGF, contributed to enhanced regional perfusion by increasing arteriolar density (1.9+/-0.4/0.572 mm(2) myocardial tissue vs. 0.7+/-0.2/0.572 mm(2) myocardial tissue, p<0.05) of large-sized (50-100 microm) arterioles. These data demonstrate that gene transfer of ANG-1 and VEGF enhances angiogenesis, but ANG-1 promotes sustained improvement of ventricular perfusion that expedites recovery of ischemic myocardium via arteriogenesis.

Adenoviridae↗
PubMed2006

Ginsenoside metabolites, rather than naturally occurring ginsenosides, lead to inhibition of human cytochrome P450 enzymes.

There is still an argument about ginseng-prescription drug interactions. To evaluate the influence on cytochrome P450 (P450) activities of ginseng in the present study, the influence on P450 activities of naturally occurring ginsenosides and their degradation products in human gut lumen was assayed by using human liver microsomes and cDNA-expressed CYP3A4. The results showed that the naturally occurring ginsenosides exhibited no inhibition or weak inhibition against human CYP3A4, CYP2D6, CYP2C9, CYP2A6, or CYP1A2 activities; however, their main intestinal metabolites demonstrated a wide range of inhibition of the P450-mediated metabolism. There was no mechanism-based inhibition found on these P450 isoforms. It is noteworthy that Compound K, protopanaxadiol (Ppd), and protopanaxatriol (Ppt) all exhibited moderate inhibition against CYP2C9 activity, and Ppd and Ppt also exhibited potent competitive inhibition against CYP3A4 activity. We suggest that after oral administration, naturally occurring ginsenosides might influence hepatic P450 activity in vivo via their intestinal metabolites.

Animals↗
PubMed2006

Mouse follicular and marginal zone B cells show differential expression of Dnmt3a and sensitivity to 5'-azacytidine.

Mature B cells in the spleen of mouse and human comprise of two main subsets, the follicular (Fo) B cells and the marginal zone (MZ) B cells. In this study, we report that Fo and MZ B cells express different levels of DNA methyltransferase Dnmt3a. By using RT-PCR and immunohistochemistry, we found that Fo B cells expressed high level of Dnmt3a while MZ B cells expressed little. Treatment of mice by in vivo administration of 5'-azacytidine, an inhibitor of DNA methyltransferases, induced B cell loss in both the bone marrow and the spleen. We noticed that this treatment resulted in a much faster and more severe disappearance of Fo B cells than MZ B cells in the spleen. Further analysis showed that MZ progenitors increased significantly in mice treated with 5'-azacytidine. These results suggest that epigenetic mechanisms involving Dnmt3a might participate in the development of B cells including the differentiation of Fo B cells and MZ B cells in the periphery.

Animals↗
PubMed2006

Novel potent agonist [(pF)Phe4,Aib7,Aib11,Arg14,Lys15]N/OFQ-NH2 and antagonist [Nphe1,(pF)Phe4,Aib7,Aib11,Arg14,Lys15]N/OFQ-NH2 of nociceptin/orphanin FQ receptor.

Two novel ligands for the nociceptin/orphanin FQ (N/OFQ) receptor (NOP), [(pF)Phe4,Aib7, Aib11,Arg14,Lys15]N/OFQ-NH2 (peptide-1) and [Nphe1,(pF)Phe4,Aib7,Aib11,Arg14,Lys15]N/OFQ-NH2 (peptide-2), have been generated by combining different modifications of N/OFQ sequence. In the present study, we investigated the actions of two analogues and compared them with those of N/OFQ in four assays. Peptide-1 mimicked N/OFQ effects in mouse vas deferens and mouse colon and showed similar maximal effects but higher potency relative to N/OFQ. The effects of peptide-1 were sensitive to NOP receptor selective antagonist ([Nphe1]N/OFQ(1-13)-NH2) but not to naloxone in vitro. Peptide-1 (25 pmol, i.c.v.) mimicked the pronociceptive action of N/OFQ (2.5 nmol, i.c.v.) in mouse tail withdrawal assay, displaying higher potency and longer lasting effects. In anesthetized rats, peptide-1 (1 nmol/kg, i.v.) produced a marked decrease in mean arterial pressure, which was comparable to that evoked by i.v. N/OFQ (100 nmol/kg). Peptide-2 did not produce any effect per se but antagonized N/OFQ actions in mouse vas deferens and mouse colon assays. Peptide-2 is active in vivo where it prevented the pronociceptive effect induced by 2.5 nmol N/OFQ i.c.v. in the mouse tail withdrawal assay. Furthermore, peptide-2 at 5 nmol produced alone a robust and long lasting antinociceptive effect. Moreover, peptide-2 (10 and 40 nmol/kg i.v.) didn't produce any effect per se but antagonized hypotensive actions produced by i.v. administration of N/OFQ. Collectively, these findings demonstrate that [(pF)Phe4,Aib7,Aib11, Arg14,Lys15]N/OFQ-NH2 behaves as a highly potent NOP receptor agonist which produces long lasting effects in vivo and [Nphe1,(pF)Phe4,Aib7,Aib11,Arg14,Lys15]N/OFQ-NH2 acts as a pure and competitive antagonist of the NOP receptor.

Animals↗
PubMed2006

Discovery of bitriazolyl compounds as novel antiviral candidates for combating the tobacco mosaic virus.

Bitriazolyl compounds were synthesized and their activity against tobacco mosaic virus was assessed. Two of them showed promising antiviral activity and were more potent than the reference compounds. Moreover, these compounds are predicted not to be carcinogenic or mutagenic based on the prediction systems. Therefore, the bitriazolyl compounds may provide interesting new leads or scaffolds for use in further attempts to screen novel antiviral candidates.

Antiviral Agents↗
PubMed2006

Prolonged diabetes reversal after intraportal xenotransplantation of wild-type porcine islets in immunosuppressed nonhuman primates.

Cell-based diabetes therapy requires an abundant cell source. Here, we report reversal of diabetes for more than 100 d in cynomolgus macaques after intraportal transplantation of cultured islets from genetically unmodified pigs without Gal-specific antibody manipulation. Immunotherapy with CD25-specific and CD154-specific monoclonal antibodies, FTY720 (or tacrolimus), everolimus and leflunomide suppressed indirect activation of T cells, elicitation of non-Gal pig-specific IgG antibody, intragraft expression of proinflammatory cytokines and invasion of infiltrating mononuclear cells into islets.

Animals↗
PubMed2006

Role of HMGB1 in cardiovascular diseases.

A nuclear protein, high mobility group box 1 (HMGB1), is released passively by necrotic cells, and actively by macrophages/monocytes in response to exogenous and endogenous inflammatory stimuli. After binding to the receptor for advanced glycation end products (RAGE) or toll-like receptor 4 (TLR4), HMGB1 activates vascular endothelial cells and macrophages/monocytes to express proinflammatory cytokines, chemokines and adhesion molecules. Pharmacological suppression of its activities or release is protective against lethal endotoxemia and sepsis, establishing HMGB1 as a critical mediator of lethal systemic inflammation. In light of the pathogenic role of inflammation in cardiovascular diseases, we propose that HMGB1, a proinflammatory cytokine derived from both injured endothelium and activated macrophages/monocytes, could contribute to the progression of atherosclerosis and other cardiovascular diseases.

Amino Acid Sequence↗
PubMed2006

A normal mucin-binding lectin from the sponge Craniella australiensis.

A lectin, Craniella australiensis (CAL), was isolated from sponge C. australiensis by ion-exchange on DEAE-Sephacel and purified by gel filtration on Sephadex G-150 and HPLC on DEAE-5PW. The purified lectin was a trimeric protein as revealed by SDS-PAGE and MALDI-TOF analysis. SDS-PAGE showed that the CAL protein had a molecular mass of 54 kDa, and consisted of three 18 kDa subunits. Gel filtration of purified lectin on Sephadex G-200 indicates that it exists as a 54 kDa protein in its native state. The amino acid composition was rich in Thr and Glx. CAL was found to agglutinate native and trypsinized human A, B erythrocytes, and agglutinate native erythrocytes of mouse, sheep, rabbit and chicken, and trypsinized erythrocytes of sheep and rabbit. The hemagglutination activity was inhibited by glycoproteins such as PSM and asialo-PSM, but not by any of the monosaccharides tested. The activity was stable between 20 and 70 degrees C. Significant CAL activity was observed between pH 5 and 8. The lectin reaction is independent of the presence of divalent cations Ca2+ and Mg2+. The sequence of N-terminal residues of CAL was determined as TSSCQSIVVE. The lectin showed a potent mitogenic response towards BALB/c splenocytes.

Amino Acid Sequence↗