Bacterial Distribution and Phylogenetic Diversity in the Changjiang Estuary before the Construction of the Three Gorges Dam

The bacterial community structure in the Changjiang estuary was studied for comparison with future changes, related to the construction of the Three Gorges Dam. Population densities of bacteria in the surface water at station C1 estimated by CFU on marine agar plates and by DAPI direct count, were 2.8 x 10(4) ml(-1) and 4.2 x 10(5) ml(-1), respectively. Physicochemical properties of water, such as temperature and salinity, suggested that station C1 was affected by freshwater from the Changjiang River. Cluster analysis of the PCR-RFLP patterns obtained from 9 samples showed that the bacterial community structure at station C1 was different from the structure at the other stations. Bacterial diversity in the surface water at station C1 was studied based on the genotypes of the 250 clones of 16S rRNA, and on the phenotypes generated on Biolog GN plates for 70 isolates. Sequences of bacteria from two common marine groups, alpha- and gamma-Proteobacteria, were frequently observed. Some other divisions, including the beta-Proteobacteria, C/F/B group, low G+C gram positive, high G+C gram positive, chloroplasts, and relatives of Verrucomicrobia were also observed. The putative dominant species based on both genotype and phenotype analyses were close relatives of Alteromonas macleodii or Roseobacter spp. These results reflected the nutrient-rich environment at station C1.     

The levels of mature glycosylated nicastrin are regulated and correlate with gamma-secretase processing of amyloid beta-precursor protein

Nicastrin, a type-I transmembrane glycoprotein, is a necessary component of the high molecular weight presenilin (PS) complexes that mediate intramembranous cleavage of beta-amyloid precursor protein (betaAPP) and Notch. Nicastrin undergoes trafficking-dependent glycosylation maturation, and PS1 interacts preferentially with these maturely glycosylated forms of nicastrin. We investigated the effects of differing levels of the immature and mature endoglycosidase-H-resistant forms of nicastrin on Abeta40- and Abeta42-peptide secretion in several cell lines stably expressing a mutant nicastrin (D336A/Y337A) that increases Abeta secretion. There was no correlation between Abeta secretion and the level of over-expression of the immature forms of nicastrin. The total level of mature nicastrin remained constant, but mutant nicastrin replaced endogenous mature nicastrin in varying degrees. Differences in the levels of mature mutant nicastrin positively correlated with Abeta secretion, but did not influence either betaAPP trafficking or processing by alpha- and beta-secretases. Proper trafficking and terminal maturation of nicastrin is therefore a necessary event for the regulated intramembranous proteolysis of betaAPP.     

Identification of genes expressed preferentially in the honeybee mushroom bodies by combination of differential display and cDNA microarray

To clarify the molecular basis underlying the neural function of the honeybee mushroom bodies (MBs), we identified three genes preferentially expressed in MB using cDNA microarrays containing 480 differential display-positive candidate cDNAs expressed locally or differentially, dependent on caste/aggressive behavior in the honeybee brain. One of the cDNAs encodes a putative type I inositol 1,4,5-trisphosphate (IP(3)) 5-phosphatase and was expressed preferentially in one of two types of intrinsic MB neurons, the large-type Kenyon cells, suggesting that IP(3)-mediated Ca(2+) signaling is enhanced in these neurons.     

Localization of group IB phospholipase A(2) isoform in the gills of the red sea bream,Pagrus (Chrysophrys) major

We previously reported that PLA(2) activity in the gills is higher than that in other tissues in red sea bream and purified PLA(2) from the gills belongs to the group IB PLA(2) as well as other red sea bream PLA(2)s. In this study, we reconfirmed that the level of PLA(2) activity is extremely high in the gills compared with other tissues, and gill PLA(2) was detected only in the gills by immunoblotting and inhibition test using anti-gill PLA(2) monoclonal antibody. The level of PLA(2) activity and protein expression in the gills are well correlated. Fish can be roughly divided into high and low groups based on the level of PLA(2) activity. Gill PLA(2) was detected in the gills of the high group, but not the low group by immunoblotting. In the gills of the high group, gill PLA(2) was detected in the mucous cells and pavement cells located on the surface of gill epithelia by immunohistochemistry. On the other hand, positive signals were observed only in the mucous cells by in situ hybridization. We also isolated inactive proPLA(2), having AR propeptide, preceding the mature enzyme from the gill extract. These results suggest that gill PLA(2) is synthesized as an inactive proPLA(2) in the mucous cells and is secreted to the surface of gill epithelia.     

Thermodynamic characterization of variants of mesophilic cytochrome c and its thermophilic counterpart

Thermal stability was measured for variants of cytochrome c-551 (PA c-551) from a mesophile, Pseudomonas aeruginosa, and a thermophilic counterpart, Hydrogenobacter thermophilus cytochrome c-552 (HT c-552), by differential scanning calorimetry (DSC) at pH 3.6. The mutated residues in PA c-551, selected with reference to the corresponding residues in HT c-552, were located in three spatially separated regions: region I, Phe7 to Ala/Val13 to Met; region II, Glu34 to Tyr/Phe43 to Tyr; and region III, Val78 to Ile. The thermodynamic parameters determined indicated that the mutations in regions I and III caused enhanced stability through not only enthalpic but also entropic contributions, which reflected improved packing of the side chains. Meanwhile, the mutated region II made enthalpic contributions to the stability through electrostatic interactions. The obtained differences in the Gibbs free energy changes of unfolding [Delta(DeltaG)] showed that the three regions contributed to the overall stability in an additive manner. HT c-552 had the smallest heat capacity change (DeltaC(P)), resulting in higher DeltaG values over a wide temperature range (0-100 degrees C), compared to the PA c-551 variants; this contributed to the highest stability of HT c-552. Our DSC measurement results, in conjunction with mutagenesis and structural studies on the homologous mesophilic and thermophilic cytochromes c, provided an extended thermodynamic view of protein stabilization.     

Characterization and imprinting status of OBPH1/Obph1 gene: implications for an extended imprinting domain in human and mouse

Human 11p15.5, as well as its orthologous mouse 7F4/F5, is known as the imprinting domain extending from IPL/Ipl to H19. OBPH1 and Obph1 are located beyond the presumed imprinting boundary on the IPL/Ipl side. We determined full-length cDNAs and complete genomic structures of both orthologues. We also investigated their precise imprinting and methylation status. The orthologues resembled each other in genomic structure and in the position of the 5' CpG island and were expressed ubiquitously. OBPH1 and Obph1 were predominantly expressed from the maternal allele only in placenta, with hypo- and not differentially methylated 5' CpG islands in both species. These results suggested that the imprinting domain would extend beyond the presumed imprinting boundary and that methylation of the 5' CpG island was not associated with the imprinting status in either species. It remains to be elucidated whether the gene is under the control of the KIP2/LIT1 subdomain or is regulated by a specific mechanism. Analysis of the precise genomic sequence around the region should help resolve this question.     

4-hydroxynonenal induces glutamate cysteine ligase through JNK in HBE1 cells

Glutathione is the most abundant non-protein thiol in the cell, with roles in cell cycle regulation, detoxification of xenobiotics, and maintaining the redox tone of the cell. The glutathione content is controlled at several levels, the most important being the rate of de novo synthesis, which is mediated by two enzymes, glutamate cysteine ligase (GCL), and glutathione synthetase (GS), with GCL being rate-limiting generally. The GCL holoenzyme consists of a catalytic (GCLC) and a modulatory (GCLM) subunit, which are encoded by separate genes. In the present study, the signaling mechanisms leading to de novo synthesis of GSH in response to physiologically relevant concentrations of 4-hydroxy-2-nonenal (4HNE), an endproduct of lipid peroxidation, were investigated. We demonstrated that exposure to 4HNE resulted in increased content of both Gcl mRNAs, both GCL subunits, phosphorylated JNK1 and c-Jun proteins, as well as Gcl TRE sequence-specific AP-1 binding activity. These increases were attenuated by pretreating the cells with a novel membrane-permeable JNK pathway inhibitor, while chemical inhibitors of the p38 or ERK pathways were ineffective. These data reveal that de novo GSH biosynthesis in response to 4HNE signals through the JNK pathway and suggests a major role for AP-1 driven expression of both Gcl genes in HBE1 cells.     

Dominant-negative mutant of BIG2, an ARF-guanine nucleotide exchange factor,specifically affects membrane trafficking from the trans-Golgi network through inhibiting membrane association of AP-1 and GGA coat proteins

BIG2 is one of the guanine nucleotide exchange factors (GEFs) for the ADP-ribosylation factor (ARF) family of small GTPases, which regulate membrane association of COPI and AP-1 coat protein complexes and GGA proteins. Brefeldin A (BFA), an ARF-GEF inhibitor, causes redistribution of the coat proteins from membranes to the cytoplasm and membrane tubulation of the Golgi complex and the trans-Golgi network (TGN). We have recently shown that BIG2 overexpression blocks BFA-induced redistribution of the AP-1 complex but not TGN membrane tubulation. In the present study, we constructed a dominant-negative BIG2 mutant and found that when expressed in cells it induced redistribution of AP-1 and GGA1 and membrane tubulation of the TGN. By contrast, the mutant did not induce COPI redistribution or Golgi membrane tubulation. These observations indicate that BIG2 is involved in trafficking from the TGN by regulating membrane association of AP-1 and GGA through activating ARF.