Role of follicular dendritic cells in the early HIV-1 infection: in vitro model without specific antibody

About 90% of HIV-1 RNA in the lymph nodes is reported to localize in follicular dendritic cellsnetwork (FDC-NW) as early as several days after infection and as much as that in the late stage. But the mechanism remains to be fully understood. To elucidate the role of follicular dendritic cells (FDC) in the early stage of HIV-1 infection, FDC-like cell strains (FDCLC) were established and they were characterized in the co-culture system with T cells for their effect on HIV-1 trapping and replication in p24 immunoassay, immunohistochemistry as well as confocal and electronmicroscopy. Established FDCLC were positive for CNA-42, S-100alpha and intercellular desmosome-like junctions. L-SIGN and DC-SIGN were also detected in FDCLC. Alu-HIV-1 PCR analysis showed no HIV-1 integration in FDCLC. FDCLC trapped HIV-1 and transferred them to uninfected MOLT-4 T cells (MOLT-4) efficiently in the absence of specific antibody. FDCLC also accelerated HIV-1 replication in HIV-1-pre-exposed MOLT-4. These unique FDCLC effects were explained, at least partly, by the fact that FDCLC up-regulated CD4 expression in MOLT-4 and helped T cells escape from apoptosis in the co-culture. These data suggest that FDC/FDCLC engage not only in trapping but also in active expansion of HIV-1 in the absence of specific antibody.     

Target proteins of the cytosolic thioredoxins in Arabidopsis thaliana

Possible target proteins of cytosolic thioredoxin in higher plants have been investigated in the cell lysate of dark-grown Arabidopsis thaliana whole tissues. We immobilized a mutant of cytosolic thioredoxin, in which an internal cysteine at the active site was substituted with serine, on CNBr activated resin, and used the resin for the thioredoxin-affinity chromatography. By using this resin, the target proteins for thioredoxin in the higher plant cytosol were efficiently acquired. The obtained proteins were separated by two-dimensional gel electrophoresis and analyzed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Thus we have identified proteins of the anti-oxidative stress system proteins (ascorbate peroxidase, germin-like protein, and monomeric type II peroxiredoxin), proteins involved in protein biosynthesis (elongation factor-2 and eukaryotic translation initiation factor 4A), proteins involved in protein degradation (the regulatory subunit of 26S proteasome), and several metabolic enzymes (alcohol dehydrogenase, fructose 1,6-bis phosphate aldolase-like protein, cytosolic glyceraldehyde 3-phosphate dehydrogenase, cytosolic malate dehydrogenase, and vitamin B(12)-independent methionine synthase) together with some chloroplast proteins (chaperonin 60-alpha and 60-beta, heat shock protein 70, and glutamine synthase). The results in this study and recent proteomics studies on the target proteins of chloroplast thioredoxin indicate the versatility and the physiological significance of thioredoxin as reductant in plant cell.     

Simple RNAi vectors for stable and transient suppression of gene function in rice

Since the recent sequencing of the rice genome, the functional identification of rice genes has become increasingly important. Various tagged lines have been generated; however, the number of tagged genes available is not sufficient for extensive study of gene function. To help identify the functions of genes in rice, we developed a Gateway vector, pANDA, for RNA interference of rice genes. This vector can be used for Agrobacterium transformation of rice and allows easy and fast construction of efficient RNAi vectors. In the construct, hairpin RNA derived from a given gene is transcribed from a strong maize ubiquitin promoter, and an intron is placed 5' upstream of inverted repeats to enhance RNA expression. Analysis of rice genes using this vector showed that suppression of mRNA expression was observed in more than 90% of transgenic plants examined, and short interfering RNA indicative of RNA silencing was detected in each silenced plant. A similar vector, pANDA-mini, was also developed for direct transfer into leaf cells or protoplasts. This vector can be used for transient suppression of gene function in rice. These vectors should help identify the functions of rice genes whose tagged mutants are not available at present and complement existing methods for functional genomics of rice.     

Allelotypic characteristics of thorotrast-induced intrahepatic cholangiocarcinoma: comparison to liver cancers not associated with thorotrast

To elucidate the genetic alterations that are specific to Thorotrast-induced liver cancers and their possible roles in tumorigenesis, we analyzed loss of heterozygosity (LOH) at 37 loci. Our previous study of liver cancers that were not associated with Thorotrast found LOH at 9 of these loci to be characteristic of intrahepatic cholangiocarcinoma (ICC), at 19 to be characteristic of hepatocellular carcinoma (HCC), and at 9 to be common to both ICC and HCC. LOH analysis was also performed in tissues of cholangiolocellular carcinoma, which is thought to originate from a common stem cell progenitor of hepatocytes and bile duct epithelial cells. We found frequent LOH at D4S1538, D16S2624 and D17S1303 to be common to all the subtypes of liver cancers, independent of the specific carcinogenic agent. In contrast, LOH at D4S1652 generally was not observed in Thorotrast-induced ICC. LOH analysis revealed that Thorotrast-induced ICC shares some LOH features with both ICC and HCC that were not induced by Thorotrast; however, it is more similar to ICC than to HCC in terms of genetic changes. This study could narrow down the crucial chromosomal loci whose deletions are relevant to hepatobiliary carcinogenesis irrespective of the carcinogenic agent. The study of LOH at loci other the those crucial ones may help us understand how the phenotype of liver cancers is determined.     

Role of arginine in protein refolding, solubilization, and purification

Recombinant proteins are often expressed in the form of insoluble inclusion bodies in bacteria. To facilitate refolding of recombinant proteins obtained from inclusion bodies, 0.1 to 1 M arginine is customarily included in solvents used for refolding the proteins by dialysis or dilution. In addition, arginine at higher concentrations, e.g., 0.5-2 M, can be used to extract active, folded proteins from insoluble pellets obtained after lysing Escherichia coli cells. Moreover, arginine increases the yield of proteins secreted to the periplasm, enhances elution of antibodies from Protein-A columns, and stabilizes proteins during storage. All these arginine effects are apparently due to suppression of protein aggregation. Little is known, however, about the mechanism. Various effects of solvent additives on proteins have been attributed to their preferential interaction with the protein, effects on surface tension, or effects on amino acid solubility. The suppression of protein aggregation by arginine cannot be readily explained by either surface tension effects or preferential interactions. In this review we show that interactions between the guanidinium group of arginine and tryptophan side chains may be responsible for suppression of protein aggregation by arginine.     

Maturation-related variations in prostaglandin and fatty acid content of ovary in the kuruma prawn (Marsupenaeus japonicus)

Total lipid, fatty acids and prostaglandins (PGF(2 alpha) and PGE(2)) in the ovary of kuruma prawns (Marsupenaeus japonicus) were measured during ovarian development. The level of ovarian total lipid increased with an increase in the gonad-somatic index (GSI). No significant difference was found in fatty acid composition among different stages of ovarian development. However, the content of arachidonic acid (precursor of PG(2)), but not eicosapentanoic acid (precursor of PG(3)), was significantly lower at stages I and II than at stage V (P<0.01). When ovarian PGF(2 alpha) and PGE(2) levels were plotted against GSI, no correlation was found in either PG. However, in terms of ovarian developmental stages, the level of ovarian PGs was high (approx. 20 pg/mg) at stage I, followed by marked decreases at stages IV and V (PGF(2 alpha), P<0.01) and stage IV (PGE(2), P<0.01). These results suggest that ovarian PGs and arachidonic acid are deeply involved in ovarian maturation in kuruma prawns.     

Genetic variations estimated from PCR-RFLP analysis of two morphs of the freshwater goby <Emphasis Type="Italic">Rhinogobius</Emphasis> in the Lake Biwa water system

The freshwater goby Rhinogobius is the most abundant fish in the shore area of Lake Biwa, Japan. Recently, it has been reported that two morphs of Rhinogobius inhabit this lake. In this study, genetic variations in Rhinogobius sp. OR (Orange-type) and Rhinogobius sp. BW (Biwa-type) in the Lake Biwa water system have been investigated using polymerase chain reaction-based restriction fragment length polymorphism (PCR-RFLP) analysis of mitochondrial DNA, including the variable D-loop region. Samples of Rhinogobius sp. OR were collected from the middle sites of three rivers, two outlets, and two lakeshore sites, whereas samples of Rhinogobius sp. BW were taken from two lakeshore sites. Rhinogobius sp. OR and Rhinogobius sp. BW did not share any haplotypes, suggesting that PCR-RFLP analysis is effective for distinguishing between these species of goby. The haplotype diversity of Rhinogobius sp. OR (0.214–0.543) was lower than that of Rhinogobius sp. BW (0.543–0.682). There were no significant differences in haplotype frequencies between Rhinogobius sp. BW groups from the two localities. In addition, haplotype frequencies in Rhinogobius sp. OR did not differ significantly among samples from the middle sites of rivers, the outlets, and the shores. These results indicate that in Rhinogobius sp. OR there is frequent gene flow among fish inhabiting different sites, and that this species of goby consists of a single population throughout the Lake Biwa water system.     

Dual intracellular signaling by proteolytic cleavage of membrane-anchored heparin-binding EGF-like growth factor

Heparin-binding EGF-like growth factor (HB-EGF), a member of the EGF family, is synthesized as a membrane-anchored precursor (proHB-EGF) that is cleaved to release a soluble HB-EGF by specific metalloproteases. Proteolytic cleavage of proHB-EGF yields amino- and carboxy-terminal fragments (HB-EGF and HB-EGF-C). Recent studies indicate that the processing of proHB-EGF is strictly regulated and involved in a variety of biological processes and that not only HB-EGF but also HB-EGF-C functions as a signaling molecule. ProHB-EGF generates dual intracellular signaling molecules by its proteolytic cleavage.