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Biomedical subjects

Ping Wang

Publications and source records attributed to Ping Wang.

At least 217 records · Page 12Linked to original sources
PubMed2004

A Drosophila temperature-sensitive seizure mutant in phosphoglycerate kinase disrupts ATP generation and alters synaptic function.

A novel paralytic mutant, nubian, was identified in a behavioral screen for conditional temperature-sensitive seizure mutants in Drosophila melanogaster. nubian mutants display reduced lifespan, abnormal motor behavior, altered synaptic structure, and defective neurotransmitter release. The nubian mutant disrupts phosphoglycerate kinase (PGK), an enzyme required for ATP generation in the terminal stage of the glycolytic pathway. Consistent with altered ATP generation in nubian animals, brain extracts show a threefold reduction in resting ATP levels compared with controls. Microarray analysis of nubian mutants reveals altered transcription of genes implicated in glucose and lipid metabolism. Disruption of ATP generation in nubian animals is accompanied by temperature-dependent defects in neuronal activity, with initial seizure activity, followed by an activity-dependent loss of synaptic transmission. nubian mutants also display structural defects at the synapse, with larger varicosity size but normal varicosity number, indicating that these synaptic parameters are regulated independently. Both exocytotic (NSF) and endocytotic (dynamin) ATPase/GTPase activity are required for normal synaptic transmission. Biochemical and physiological analyses indicate that synaptic defects in nubian animals are secondary to defective endocytosis, suggesting that endocytotic pathways may be generally more sensitive to altered ATP levels than those used for exocytosis. Alterations in ATP metabolism likely disrupt similar pathways in humans, because PGK deficiency is associated with mental retardation, seizures, and exercise intolerance. Given the behavioral similarities between disruptions of PGK function in Drosophila and humans, the analysis of nubian animals may reveal conserved neuronal responses associated with altered ATP generation within the brain.

Adenosine Triphosphate↗
PubMed2004

Insulin induces SOCS-6 expression and its binding to the p85 monomer of phosphoinositide 3-kinase, resulting in improvement in glucose metabolism.

The suppressors of cytokine signaling (SOCS) family is thought to act largely as a negative regulator of signaling by cytokines and some growth factors. Surprisingly, the SOCS-6 transgenics had no significant defects in the cytokine signaling and hematopoietic system but displayed significant improvements in glucose metabolism. Insulin stimulation of Akt/protein kinase B was also potentiated. Biochemical analysis showed that, after insulin stimulation, SOCS-6 interacted with the monomeric p85 subunit of class-Ia phosphoinositide (PI) 3-kinase but not with p85/p110 dimers. Furthermore, SOCS-6 expression is transiently increased by serum and insulin in normal fibroblasts. However, both the mRNA and protein of SOCS-6 were rapidly degraded after induction by insulin. The degradation of the SOCS-6 protein was partially inhibited by a proteasome inhibitor, suggesting a proteasome-mediated degradation mechanism. In contrast, SOCS-6-associated p85 was not degraded and could be recruited to the newly synthesized SOCS-6 molecules in the presence of insulin, suggesting that SOCS-6 expression and its interaction with p85, but not the degradation, is regulated by insulin. The phenotype of SOCS-6 transgenic mice bears a striking resemblance to p85 knock-out mouse models in which glucose metabolism stimulated by insulin is significantly improved despite reduced activation of PI 3-kinase. This suggests that monomeric p85 might play a physiologically important role in attenuating signaling through PI 3-kinase-dependent pathways in unstimulated cells. Therefore, our results indicate that SOCS-6 may provide a dynamically regulated mechanism by which insulin can transiently overcome the negative effects that p85 monomers have on signaling via PI 3-kinase-dependent signaling pathways.

Animals↗
PubMed2004

ILKAP regulates ILK signaling and inhibits anchorage-independent growth.

ILKAP is a protein phosphatase 2C that selectively associates with integrin linked kinase, ILK, to modulate cell adhesion and growth factor signaling. We investigated the role of endogenous cellular ILKAP in antagonizing ILK signaling of two key targets, PKB and GSK3beta. Silencing of endogenous ILKAP by short interfering RNA (siRNA) stimulated GSK3beta phosphorylation at S9, with no effect on PKB S473 phosphorylation. In LNCaP prostate carcinoma cells, transient or stable expression of ILKAP suppressed ILK immune complex kinase activity, demonstrating an interaction between ILKAP and ILK. Consistent with the silencing data, ILKAP inhibition of ILK selectively inhibited S9 phosphorylation of GSK3beta without affecting S473 phosphorylation of PKB. The ILKAP-mediated inhibition of S9 phosphorylation was rescued by overexpression of ILK, but not by a dominant-negative ILK mutant. The expression level of cyclin D1, a target of ILK-GSK3beta signaling, was inversely correlated with ILKAP protein levels, suggesting that antagonism of ILK modulates cell cycle progression. ILKAP expression increased the proportion of LNCaP cells in G1, relative to vector control cells, and siRNA suppression of ILKAP increased entry of cells into the S phase, consistent with ILK antagonism. Anchorage-independent growth of LNCaP cells was inhibited by ILKAP, suggesting a critical role in the suppression of cellular transformation. Taken together, our results indicate that endogenous ILKAP activity inhibits the ILK-GSK3beta signaling axis, and suggest that ILKAP activity plays an important role in inhibiting oncogenic transformation.Oncogene (2004) 23, 3454-3461. doi:10.1038/sj.onc.1207473 Published online 1 March 2004

Cell Cycle↗
PubMed2004

Nickel(II) and cobalt(II) complexes of hydroxyl-substituted triazamacrocyclic ligand as potential antitumor agents.

The stability constants for the formation of nickel(II) and cobalt(II) complexes of the ligand [1,4,7]triazecan-9-ol (L) were presented. Antitumor activity of two complexes was reported. Nuclei of [NiL]-stimulated BEL-7402 cells clearly exhibited condensation and break down into chromatin clumps typical of apoptosis. Also it exhibited perturbation effects to cell cycle, and optimal induction of apoptosis was found by Flow-Cytometric analysis. But CoL complex did not exhibit introduction effects to BEL-7402 cells apoptosis; and could not perturb cell cycle. NiL and CuL complexes could cleave supercoiled DNA (pBR 322 DNA) to nicked and linear DNA, and DNA of cells treated with NiL or CuL complex was obviously damaged; while CoL complex only could cleave supercoiled DNA (pBR 322 DNA) to nicked DNA, and DNA of cells treated with CoL complex had no significant difference with control.

Antineoplastic Agents↗
PubMed2004

Mint-3 regulates the retrieval of the internalized membrane-type matrix metalloproteinase, MT5-MMP, to the plasma membrane by binding to its carboxyl end motif EWV.

Membrane type matrix metalloproteinases (MT-MMPs) play a critical role in promoting cell growth and migration within the extracellular matrix by trafficking to specialized areas. Here we show that the carboxyl EWV motif of MT5-MMP serves as a retrieval signal for internalized MT5-MMP by interacting with Mint-3, a protein with two type III PDZ domains. Deletion of the EWV signal impairs the recycling of MT5-MMP without affecting its internalization, leading to decreased activity on the cell surface. A yeast two-hybrid screening identified Mint-3 as the EWV-binding protein. Mint-3 stimulates MT5-MMP activity when expressed at low levels in an EWV-dependent fashion, but inhibits its activity at higher levels independent of the EWV motif. siRNA-mediated knockdown of endogenous Mint-3 decreased MT5-MMP activity. Furthermore, Mint-3 significantly increased the level of MT5-MMP on the cell surface without affecting its synthesis and internalization. Therefore, Mints may be the adaptor proteins that regulate the trafficking of MT-MMPs.

Adaptor Proteins, Signal Transducing↗
PubMed2004

Mucopolysaccharidosis type VII in a German Shepherd Dog.

A 12-week-old male German Shepherd Dog was evaluated because of a 3-week history of a progressive inability to ambulate. Clinical and laboratory findings included skeletal deformities, corneal cloudiness, cytoplasmic granules in the neutrophils and lymphocytes of blood and CSF and glycosaminoglycans in a urine sample (detected via a toluidine blue spot test). Enzyme activity and DNA analyses confirmed mucopolysaccharidosis type VII as a result of severe beta-glucuronidase deficiency; this condition had been identified in a mixed-breed dog (likely of German Shepherd Dog descent) that was reported 20 years earlier and caused by the same missense mutation. Because of the progressive nature of this disease, the puppy was euthanatized and all tissues examined contained evidence of lysosomal storage leading to marked cellular distention. Mucopolysaccharidosis type VII is only one of many hereditary lysosomal storage diseases identified in companion animals. It is important that clinicians recognize the typical signs of lysosomal storage diseases and are aware of the cytologic and urinary screening tests for mucopolysaccharidosis disorders. Furthermore, there are specific blood enzyme and DNA-based tests to distinguish the forms of mucopolysaccharidosis in affected and carrier animals.

Animals↗
PubMed2004

Separation of purine and pyrimidine bases by capillary electrophoresis using beta-cyclodextrin as an additive.

Capillary electrophoresis was applied to separate purine and pyrimidine bases in the basis of their partial ionization in the alkaline buffer. The effects of buffer pH, buffer and beta-cylclodextrin concentration were systematically investigated using a commercial capillary electrophoresis instrument with UV detector at 254nm. We found that the resolutions of bases (especially for adenine and thymine) were significantly improved in the presence of beta-cylclodextrin. The satisfactory separation of five bases such as cytosine, thymine, adenine, guanine and uracil were achieved by capillary electrophoresis using beta-cylclodextrin as an additive. Under the optimal conditions, the linear range was from 2 to 200microg/ml for bases (R= 0,991-0,9977 ) and the detection limits were from 0.8 to 1.8microg/ml (S/N = 2). The detection limit of 0.05microg/ml ( S/N=2 ) for uracil was obtained by stacking injection mode. The assay was used to determine the deamination of cytosine to uracil by heating in the presence of sodium hydroxide. Our primarily results show that capillary electrophoresis is a very useful tool for determination of purine and pyrimidine bases and study on nucleic acids.

Cyclodextrins↗
PubMed2004

Proprotein convertase furin interacts with and cleaves pro-ADAMTS4 (Aggrecanase-1) in the trans-Golgi network.

A member of the A disintegrin and metalloproteinase domain with thrombospondin type-1 motifs (ADAMTS-4) protease family can efficiently cleave aggrecan at several sites detected in joints of osteoarthritic patients. Although recent studies have shown that removal of the prodomain of ADAMTS4 is critical for its ability to degrade aggrecan, the cellular mechanisms for its processing and trafficking remain unclear. In this study, by using both furin-specific inhibitor and RNA interference technique, we demonstrate that furin plays an important role in the intracellular removal of ADAMTS4 prodomain. Further, we demonstrate that proADAMTS4 can be processed by means of multiple furin recognition sites: (206)RPRR(209), (209)RAKR(212), or (211)KR(212). The processing of proADAMTS4 was completely blocked by brefeldin A treatment, suggesting that processing occurs in the trans-Golgi network. Indeed, ADAMTS4 is co-localized with furin in trans-Golgi network. Interestingly, the pro form of ADAMTS4, not its mature one, co-precipitates with furin, suggesting that furin physically interacts with the prodomain of ADAMTS-4. In addition, our evidence suggests that a furin-independent pathway may also contribute to the activation of ADAMTS4. These results indicate that the activation mechanism for ADAMTS4 can be targeted for therapeutical intervention against this enzyme.

ADAM Proteins↗
PubMed2004

The relationship of HLA antigens to doxycycline induced apoptosis in immortalized B cells.

Previous studies have shown two subsets of Lyme disease (LD) patients: a seropositive group with a high frequency of the HLA class II antigen, HLA-DR7 (DR7+), and a seronegative group with a low frequency of HLA-DR7 (DR7-). The present study examined the hypothesis that the absence or presence of this antigen may play a role in the mode of B cell death induced by doxycycline. B cells, obtained from one HLA-DR7- (AL7N) and one HLA-DR7+ (MM7P) normal volunteers, were immortalized using Epstein-Barr Virus (EBV). Doxycycline resulted in a dose-dependent decrease in cell viability which was not different between the two cell lines. DNA from the MM7P showed a strong internucleosomal fragmentation pattern consistent with apoptosis, while the AL7N showed a weaker pattern, when treated with doxycycline, 20 ug/ml, for 16 hours, a result confirmed with the TUNEL assay. In the MM7P, the level of inducible p53 peaked at 8 hours while no changes were observed in the AL7N. A much higher level of HLA class II and HLA-DR was observed in the AL7N cell line which was not affected by doxycycline. These results support the conclusion that doxycycline induces p53-dependent apoptosis in MM7P. Although doxycycline induces death in AL7N, the mode and mechanism require further study.

Anti-Bacterial Agents↗
PubMed2004

Cortical depth-dependent gradient-echo and spin-echo BOLD fMRI at 9.4T.

To examine cortical depth-related spatial specificity and signal changes in gradient-echo (GE) and spin-echo (SE) blood oxygenation level-dependent (BOLD) fMRI signals, a well-established cat visual stimulation model was used at 9.4T. The GE BOLD signal percent change is the highest at the surface of the cortex containing pial vessels, and decreases as cortical depth increases. In contrast, the SE BOLD signal is more specific to parenchyma, showing the highest signal change in the middle cortical areas. The stimulation-induced DeltaR2* to DeltaR2 ratio is dependent on the vessel size, which is related to basal susceptibility effects. The averaged ratio of DeltaR2* to DeltaR2 in all active regions, including large vessels, is 3.3 +/- 0.5 (N = 6). The averaged ratio of DeltaR2* to DeltaR2 is 8.8 +/- 1.7 (N = 4) on the surface of the cortex with large pial draining vessels, and decreases to 1.9 +/- 0.1 on the middle cortical areas with parenchymal microvessels. DeltaR2*/DeltaR2 is closely related to basal susceptibility effects and can be used to differentiate tissue from vessel regions.

Animals↗
PubMed2004

A Sch9 protein kinase homologue controlling virulence independently of the cAMP pathway in Cryptococcus neoformans.

The polysaccharide capsule is one of the established virulence factors in Cryptococcus neoformans that provides a barrier against the host-mediated immune response. Mutation of the gene encoding the Saccharomyces cerevisiae Sch9 protein kinase homologue resulted in cells with enlarged capsules in C. neoformans. Capsule production was abrogated in sch9 pka1 double mutants, indicating that protein kinase A (PKA) signaling is still necessary for capsule formation in sch9 mutants. The sch9 mutant also exhibited increased thermal tolerance, a phenotype similar to sch9 mutant strains of S. cerevisiae. In addition, the sch9 mutant was attenuated in mating and the highly encapsulated cells were attenuated in virulence, in contrast to the pkr1 mutant, lacking the regulatory subunit of protein kinase A, that produced similarly enlarged capsules yet was increased in virulence. Interestingly, the virulence for the sch9 mutant strain could be restored by introduction of a pkr1 mutation; and the sch9 pkr1 mutant strain was dramatically increased in size and capsule thickness, suggesting that Sch9 and PKA function via different targets involved in virulence. Our findings support a model in which Sch9 modulates capsule formation and contributes to the virulence of C. neoformans both independently of and in conjunction with the cAMP-PKA pathway.

Animals↗
PubMed2004

Identification of two new peritrophic membrane proteins from larval Trichoplusia ni: structural characteristics and their functions in the protease rich insect gut.

Peritrophic membrane (PM) proteins are important determinants for the structural formation and function of the PM. We identified two new chitin binding proteins, named CBP1 and CBP2, from the PM of Trichoplusia ni larvae by cDNA cloning. The proteins contain 12 and 10 tandem chitin binding domains in CBP1 and CBP2, respectively. Chitin binding studies demonstrated the chitin binding activity of CBP1 and CBP2, and confirmed the chitin binding domain sequence predicted by sequence analysis. Both CBP1 and CBP2 were not mucin-like glycoproteins, however, they were highly resistant to proteolytic degradation by trypsin. We found that in CBP1 and CBP2, potential trypsin and chymotrypsin cleavage sites reside primarily within the chitin binding domain sequences, limiting exposure of the potential cleavage sites to the digestive proteinases. This finding suggests a proteinase-resistance mechanism for non-mucin PM proteins to function in the proteinase rich gut environment. Immunohistochemical analysis showed that CBP1 and CBP2 are specifically localized in the PM. However, intact CBP1 and CBP2 proteins were not present in the PM, indicating that their partially degraded fragments were assembled into the PM. This observation suggests that the presence of a large number of chitin binding domains in PM proteins allows the proteins to tolerate limited proteolytic degradation in the midgut without loss of their chitin binding activity with multiple chitin binding domains. Alignment of the chitin binding sequences suggested that CBP1 and CBP2 evolved by gene duplication and the tandem chitin binding domains in the proteins arose from domain duplications.

Amino Acid Sequence↗
PubMed2004

Characterization and cDNA cloning of midgut carboxypeptidases from Trichoplusia ni.

Carboxypeptidase A and carboxypeptidase B activities from the midgut of Trichoplusia ni larvae were characterized. In the T. ni larval midgut, the primary digestive carboxypeptidase activity was attributed to carboxypeptidase A, which was eight times more active than carboxypeptidase B. Both the midgut carboxypeptidase A and carboxypeptidase B exhibited maximal activities at pH 8.0-8.5 and were similarly susceptible to inhibition by potato carboxypeptidase inhibitor and phenanthroline. The midgut carboxypeptidase activities were analyzed in T. ni larvae fed on various diet sources and the results indicated that midgut carboxypeptidase activities per milligram of gut were similar regardless of the amount of dietary proteins or amino acids. However, midgut carboxypeptidase A activity was significantly higher in larvae exposed to soybean trypsin inhibitor and was significantly lower in larvae fed on broccoli foliage. From the T. ni larval midgut, five putative carboxypeptidase cDNAs were cloned, demonstrating that midgut carboxypeptidase activities are composed of multiple carboxypeptidase types. Sequence analysis indicated that the midgut carboxypeptidases were produced as secreted proenzymes which could be activated after removal of an N-terminal activation fragment by a trypsin. Two cloned cDNAs are predicted to code for carboxypeptidase A and one cDNA is predicted to code for a putative carboxypeptidase B. The other two cDNAs are highly similar to carboxypeptidase A and carboxypeptidase B in sequences, but their activity was not predictable.

Amino Acid Sequence↗
PubMed2004

Intramolecular condensation reactions in protonated dipeptides: carbon monoxide, water, and ammonia losses in competition.

The elimination of carbon monoxide and water from a series of protonated dipeptides, [XxxYyy + H](+), is investigated by tandem mass spectrometry experiments and density functional theory. The combined results show that CO loss occurs on the a(1)-y(1) pathway, which begins by rearrangement of the added proton to the amide N-atom and creates the proton-bound dimer of an amino acid (Yyy) and an imine (that from Xxx residue). The loss of H(2)O is initiated from a tautomer in which the added proton has migrated to the hydroxyl group of the C-terminus, thereby promoting the formation of an ion with protonated oxazolone structure (a nominal b(2) ion). The highest yields of [XxxYyy + H - CO](+) and [XxxYyy + H - H(2)O](+) are observed at threshold energies. As the internal energy of the protonated dipeptides increases, these primary products are depleted by consecutive dissociations yielding mostly backbone fragments. Specifically, [XxxYyy + H - CO](+) decomposes to y(1) (protonated Yyy) and a(1) (immonium ion of Xxx residue), while [XxxYyy + H - H(2)O](+) produces a(2) and the immonium ions of residues Xxx (a(1)) and Yyy ("internal" immonium ion). Water loss takes place more efficiently when the more basic residue is at the C-terminal position. Increasing the basicity of the N-terminal residue enhances the extent of CO versus H(2)O loss and introduces the competitive elimination of NH(3). The dissociations leading to eliminations of small neutrals (CO, H(2)O, etc.) generally proceed over transition states that lie higher in energy than the corresponding dissociation products. The excess energy is disposed of either in translational or rovibrational modes of the products, depending on the stability of the incipient noncovalent assemblies emerging during the cleavage of the small neutrals.

Ammonia↗
PubMed2004

A complex prescription for vitiligo activates mitochondrial ATP synthase-6 expression in B-16 murine melanoma cells.

A complex prescription (CP) used traditionally for the treatment of vitiligo was prepared from water extract of eight plant materials. To study the mechanism of this preparation its effect on gene expression of B-16 murine melanoma cells was estimated using differential display method (DDRT-PCR). The results showed that the complex prescription was effective in activating the mitochondrial ATP synthase-6 (ATPase-6) gene expression in B-16 murine melanoma cells. This activity may play an important role in its treatment of vitiligo.

Animals↗
PubMed2004

Nonarteritic anterior ischemic optic neuropathy: associations with homozygosity for the C677T methylenetetrahydrofolate reductase mutation.

The association between nonarteritic anterior ischemic optic neuropathy (NAION) and coagulation disorders was prospectively assessed at least 3 months after the occurrence of ocular vascular events in 12 white patients in an outpatient clinical research center. Two community-based ophthalmologists evaluated the 12 NAION patients in the consecutive order of their referral. Polymerase chain reaction-complementary DNA assays of gene mutations associated with coagulation disorders and serologic coagulation measurements in study patients were compared with those in 36 healthy, normal race-, sex-, and age-matched controls, with 3 controls matched for each case. Of the 12 patients, 4 men and 8 women (mean age 62 +/- 15 years, 3 of them 55 years or older), 8 had unilateral NAION (bilateral in 4). The 12 patients with NAION were more likely than controls to demonstrate homozygosity for the methylenetetrahydrofolate reductase (MTHFR) C677T mutation (50% vs 11 %; Fisher's P =.009, with the likelihood of a type I error quite small, 0.9%). Our sample size had a power of 80% to detect this case-control difference in C677T MTHFR homozygosity at an alpha value of.05. Of the 12 NAION patients, 7 (58%) had at least 1 gene mutation in the C677T MTHFR, G1691A V Leiden, or G20210A prothrombin gene, compared with 5 of 36 controls (14%) (chi(2) = 9.48, P =. 002, with the likelihood of a type I error quite small, 0.2%). Our sample size had a power of 85% to detect this case-control difference at alpha =. 05. Of the 8 women with NAION, 5 (63%) first experienced the condition while taking hormone replacement therapy (n = 4) or during pregnancy (n = 1), with superposition of estrogen-induced thrombophilia on heritable thrombophilia and hypofibrinolysis. Confirmation of a causal relationship between coagulation disorders and NAION should facilitate its prevention and treatment and help protect against thrombi in other vascular beds.

Aged↗
PubMed2004

Population-specific alleles: the polymorphism (K121Q) of the human glycoprotein PC-1 gene is strongly associated with race but not with insulin resistance in black and white children.

The K121Q polymorphism of the glycoprotein PC-1 gene was recently reported to associate with insulin resistance (IR) in an all-Caucasian, Sicilian population. Given black-white differences in plasma insulin and IR, we compared the prevalence of the KK, KQ, and QQ genotypes and their associations with insulin and IR in 2 large, biracial pediatric samples: 1 hospital-based (n = 301, 137 blacks and 164 whites) and 1 school-based (n = 639, 344 blacks and 295 whites). The Q allele frequencies in the hospital-based and school-based cohorts in black children were 0.80 and 0.77 and in the white children, 0.15 and 0.13. The K allele frequencies in the hospital-based and school-based cohorts in black children were 0.20 and 0.23 and in the white children, 0.85 and 0.87. Differences in allelic frequencies were highly significant (chi square test, P <.0001) for both the hospital-based cohort and the school-based cohort. Both cohorts were in Hardy-Weinberg equilibrium. Within race, after covariance adjusting for age and body mass index (BMI), there were no significant differences (P >/=.10) among the 3 PC-1 genotypes for insulin, glucose, or homeostasis model assessment (HOMA) IR. After covariance adjusting for age and BMI, black girls had higher insulin (P =.0007) and higher HOMA IR (P =.0002) than white girls. The K121Q polymorphism was not associated with insulin, glucose, or HOMA IR measures in black or white children. However, the QQ genotype was population-specific, encompassing most black children versus 1% to 3% of white children. As such, K121Q genotyping should be useful in epidemiology, population genetics, and forensic anthropology.

Adolescent↗