alpha-Tocopherol transfer protein expression in rat liver exposed to hyperoxia

-Tochopherol transfer protein ( TTP), a 32 kDa protein exclusively expressed in liver cytosol, has a high binding affinity for -tochopherol. The factors that regulate the expression of hepatic TTP are not clearly understood. In this study, we investigated whether or not exposure to hyperoxia (95% O 2 for 48 h) could alter the expression of hepatic TTP. We also examined the association between the expression of antioxidant enzymes (hepatic glutathione peroxidase (GPX) and Mn-superoxide dismutase (Mn-SOD)) and the expression of hepatic TTP. The levels of thiobarbituric acid-reactive substances (TBARS) in both plasma and liver were significantly higher after rats were exposed to hyperoxia for 48 h when compared with the levels in control rats. Northern blotting showed a decrease in the expression of TTP messenger RNA (mRNA) after hyperoxia, although the TTP protein level remained constant. Expression of Mn-SOD mRNA and protein, as well as the expression of GPX mRNA, were stable after hyperoxia. These findings indicate that mRNA for hepatic TTP, rather than Mn-SOD or GPX, may be highly responsive to oxidative stress.     

Crystal structure of human L-isoaspartyl-O-methyl-transferase with S-adenosyl homocysteine at 1.6-A resolution and modeling of an isoaspartyl-containing peptide at the active site

Spontaneous formation of isoaspartyl residues (isoAsp) disrupts the structure and function of many normal proteins. Protein isoaspartyl methyltransferase (PIMT) reverts many isoAsp residues to aspartate as a protein repair process. We have determined the crystal structure of human protein isoaspartyl methyltransferase (HPIMT) complexed with adenosyl homocysteine (AdoHcy) to 1.6-A resolution. The core structure has a nucleotide binding domain motif, which is structurally homologous with the N-terminal domain of the bacterial Thermotoga maritima PIMT. Highly conserved residues in PIMTs among different phyla are placed at positions critical to AdoHcy binding and orienting the isoAsp residue substrate for methylation. The AdoHcy is completely enclosed within the HPIMT and a conformational change must occur to allow exchange with adenosyl methionine (AdoMet). An ordered sequential enzyme mechanism is supported because C-terminal residues involved with AdoHcy binding also form the isoAsp peptide binding site, and a change of conformation to allow AdoHcy to escape would preclude peptide binding. Modeling experiments indicated isoAsp groups observed in some known protein crystal structures could bind to the HPIMT active site.     

Relationship between gastric ulcer and Helicobacter pylori VacA detected in gastric juice using bead-ELISA method

Background. VacA is an important pathogenetic factor produced by Helicobacter pylori. VacA has often been detected in supernatants of liquid cultures or lysates of whole bacterial cells. However, no studies have ever tried to assay VacA produced in the human stomach. We applied a very sensitive and simple method, bead‐ELISA, to detect VacA in gastric juice. Materials and Methods. Forty‐eight H. pylori‐positive patients (16 nonulcer dyspepsia, 16 gastric ulcer, and 16 duodenal ulcer) and four H. pylori‐negative nonulcer dyspepsia patients had endoscopy performed and gastric juice were aspirated. Polystyrene beads coated with the antibody to VacA, were used in this bead‐ELISA method. The nucleotide sequences of vacA in the signal and middle regions were investigated. Results. Of the 48 samples that were positive for H. pylori, 21 [43.8%] were found to be VacA positive in gastric juice. The average and maximum concentrations of detected VacA in gastric juice were 143.2 ± 216.5 and 840 pg/ml, respectively. The average density of VacA from gastric ulcer patients (227.5 ± 276.7 pg/ml) was higher than that found in nonulcer dyspepsia (51.8 ± 39.8 pg/ml) and duodenal ulcer (49.2 ± 21.5 pg/ml) patients. There was no relationship between VacA in gastric juice and vacA genotype. Conclusions. VacA in gastric juice could be directly detected by bead‐ELISA. In this study, the diversity of disease outcome was associated with not the quality but the quantity of VacA. Therefore, not only the quality but also the quantity of VacA is important etiological factors in the pathogenesis of mucosal damage.     

Proinflammatory cytokine IL-1 beta promotes tumor growth of Lewis lung carcinoma by induction of angiogenic factors: in vivo analysis of tumor-stromal interaction

Inflammatory conditions are associated with tumor development. IL-1beta is a multifunctional and proinflammatory cytokine that affects nearly all types of cells. To investigate the role of IL-1beta in tumor growth in vivo, we transduced the retroviral vector coding human IL-1beta gene into mouse Lewis lung carcinoma (LLC) cells and subsequently inoculated the transformant (LLC/IL-1beta) to syngeneic C57BL/6 mice. Tumors derived from LLC/IL-1beta grew faster (240%, day 18, vs null-vector control LLC/neo; p < 0.01) and showed more abundant vasculature (250%, vs LLC/neo; p < 0.05), whereas LLC/IL-1beta cells, LLC/neo cells, and wild-type LLC cells did not show any significant difference in the growth rate in vitro. As compared with LLC/neo cells, LLC/IL-1beta cells secreted 2-fold the amount of vascular endothelial growth factor and >10-fold the amount of macrophage-inflammatory protein-2 (CXCL2), one of whose main functions is angiogenesis. Although LLC/IL-1beta itself did not secrete hepatocyte growth factor (HGF), the tumor derived from LLC/IL-1beta cells also contained a >4-fold higher concentration of HGF, another angiogenic factor. In situ hybridization of HGF mRNA in LLC/IL-1beta tumor sections demonstrated that stromal fibroblasts and infiltrating cells overexpressed HGF mRNA. Moreover, when cultured in the presence of HGF in vitro, LLC/IL-1beta cells secreted even larger amounts of vascular endothelial growth factor and macrophage-inflammatory protein-2. The antiangiogenic agent TNP-470 and anti-CXCR2 Ab inhibited the tumor growth of LLC/IL-1beta cells in vivo. These results indicated that secreting IL-1beta into the tumor milieu induces several angiogenic factors from tumor and stromal cells and thus promotes tumor growth through hyperneovascularization.     

Essential role of NF-kappa B-inducing kinase in T cell activation through the TCR/CD3 pathway

NF-kappa B-inducing kinase (NIK) is involved in lymphoid organogenesis in mice through lymphotoxin-beta receptor signaling. To clarify the roles of NIK in T cell activation through TCR/CD3 and costimulation pathways, we have studied the function of T cells from aly mice, a strain with mutant NIK. NIK mutant T cells showed impaired proliferation and IL-2 production in response to anti-CD3 stimulation, and these effects were caused by impaired NF-kappa B activity in both mature and immature T cells; the impaired NF-kappa B activity in mature T cells was also associated with the failure of maintenance of activated NF-kappa B. In contrast, responses to costimulatory signals were largely retained in aly mice, suggesting that NIK is not uniquely coupled to the costimulatory pathways. When NIK mutant T cells were stimulated in the presence of a protein kinase C (PKC) inhibitor, proliferative responses were abrogated more severely than in control mice, suggesting that both NIK and PKC control T cell activation in a cooperative manner. We also demonstrated that NIK and PKC are involved in distinct NF-kappa B activation pathways downstream of TCR/CD3. These results suggest critical roles for NIK in setting the threshold for T cell activation, and partly account for the immunodeficiency in aly mice.     

The complete purification and characterization of three forms of ferredoxin-NADP(+) oxidoreductase from a thermophilic cyanobacterium Synechococcus elongatus

The petH gene, encoding ferredoxin-NADP(+) oxidoreductase (FNR), was isolated from a thermophilic cyanobacterium, Synechococcus elongatus (the same strain as Thermosynechococcus elongatus). The petH gene of S. elongatus was a single copy gene, and the N-terminal region of PetH showed a sequence similarity to the CpcD-phycobilisome linker polypeptide. The amino acid sequence of the catalytic domains of PetH was markedly similar to those from mesophilic cyanobacterial PetH and higher plant FNR. The enzymatically active FNR protein was purified to homogeneity from S. elongatus as three forms corresponding to the 45-kDa form retaining the CpcD-like domain, the 34-kDa form lacking the CpcD-like domain, and the 78-kDa complex with phycocyanin. The FNR in the 78-kDa complex was tolerant to proteolytic cleavage. However, the dissociation of phycocyanin from the 78-kDa complex induced to specific proteolysis between the CpcD-like domain and the FAD-binding domain to give rise to the 34-kDa form of FNR. The enzymatic activity of the 45-kDa form was thermotolerant, but the 45-kDa form readily aggregated under the storage at -30 degrees C. These results suggest that the association with phycocyanin via CpcD-like domain gives remarkable stability to S. elongatus FNR.     

Cytogenetic analysis of radiation-induced leukemia in Trp53-deficient C3H/He mice

C3H/He mice develop acute myeloid leukemia (AML) after whole-body irradiation, but the strain becomes highly susceptible to stem cell leukemia (SCL) when a null mutation is introduced into the Trp53 gene. To examine the etiology of SCL and the influence of chromosomal instability on leukemogenesis, 12 SCLs and two AMLs arising from Trp53-deficient C3H/He mice were investigated cytogenetically. Each SCL demonstrated cell-to-cell variation in the number and structural integrity of their chromosomes, indicating chromosomal instability. Typical deletion of chromosome 2 was observed in the two AML cases, while most SCL cells did not display this aberration. Deletions and rearrangements of chromosome 11 were noticeable in SCLs from Trp53 heterozygotes but not in AMLs. Analysis of loss of heterozygosity revealed that aberrations involving chromosome 11 in SCLs resulted in loss of the wild-type Trp53 allele. These results suggest that loss of Trp53 function triggers the tumorigenic process leading toward SCL through the induction of chromosomal instability, and that SCL and AML are distinct varieties of leukemia.     

Calnexin Delta 185-520 partially reverses the misprocessing of the Delta F508 cystic fibrosis transmembrane conductance regulator

We analyzed the interrelation between the efficiency of a gene expression and the nucleotide composition of all protein-coding sequences in 38 unicellular organisms whose complete genomic sequences are known. These organisms comprise 37 prokaryotic (29 eubacteria and eight archaebacteria) and one eukaryotic (yeast) species. We demonstrated that frequency analysis of gene codon composition fails to reflect adequately the gene expression efficiency of all these organisms. We constructed a measure, the elongation efficiency index, that considers simultaneously the information on codon frequencies and the degree of mRNA local self-complementarity. This measure recognizes the ribosome-coding genes as highly expressed in all the unicellular organisms studied. According to our analysis, these species fall into five groups differentiated by the process that makes the key contribution to the elongation rate.     

Synthesis,aggregation, neurotoxicity,and secondary structure of various A beta 1-42 mutants of familial Alzheimer's disease at positions 21-23

Cerebral amyloid angiopathy (CAA) due to amyloid beta (A beta) deposition is a key pathological feature of Alzheimer's disease (AD), especially in some form of familial Alzheimer's disease (FAD) including hereditary cerebral hemorrhage with amyloidosis-Dutch type. A beta mainly consists of 40- and 42-mer peptides (Abeta 1-40 and A beta 1-42), which accumulate in senile plaques of AD brains and show neurotoxicity for cultured nerve cells. We synthesized all variant forms of A beta 1-42 associated with reported FAD, such as A21G (Flemish), E22Q (Dutch), E22K (Italian), E22G (Arctic), and D23N (Iowa) along with three potential mutants by one point missense mutation (E22A, E22D, and E22V) in a highly pure form, and examined their ability to aggregate and their neurotoxicity in PC12 cells. The mutants at positions 22 and 23 showed potent aggregative ability and neurotoxicity whereas the potential mutants did not, indicating that A beta 1-42 mutants at positions 22 and 23 play a critical role in FAD of Dutch-, Italian-, Arctic-, and Iowa-types. However, Flemish-type FAD needs alternative explanation except the aggregation and neurotoxicity of the corresponding A beta 1-42 mutant.