Interaction of human lactoferrin with cell adhesion molecules through RGD motif elucidated by lactoferrin-binding epitopes

Lactoferrin (LF) is an iron-binding secretory protein, which is distributed in the secondary granules of polynuclear lymphocytes as well as in the milk produced by female mammals. Although it has multiple functions, for example antimicrobial, immunomodulatory, antiviral, and anti-tumor metastasis activities, the receptors responsible for these activities are not fully understood. In this study, the binding epitopes for human LF were first isolated from a hexameric random peptide library displayed on T7 phage. Interestingly, two of the four isolated peptides had a representative cell adhesion motif, Arg-Gly-Asp (RGD), implying that human LF interacts with proteins with the RGD motif. We found that human LF bound to the RGD-containing human extracellular matrix proteins, fibronectin and vitronectin. Furthermore, human LF inhibited cell adhesion to these matrix proteins in a concentration-dependent manner but not to the RGD-independent cell adhesion molecule like laminin or collagen. These results indicate that a function of human LF is to block the various interactions between the cell surface and adhesion molecules. This may explain the multifunctionality of LF.     

Differential metabolomics reveals ophthalmic acid as an oxidative stress biomarker indicating hepatic glutathione consumption

Metabolomics is an emerging tool that can be used to gain insights into cellular and physiological responses. Here we present a metabolome differential display method based on capillary electrophoresis time-of-flight mass spectrometry to profile liver metabolites following acetaminophen-induced hepatotoxicity. We globally detected 1,859 peaks in mouse liver extracts and highlighted multiple changes in metabolite levels, including an activation of the ophthalmate biosynthesis pathway. We confirmed that ophthalmate was synthesized from 2-aminobutyrate through consecutive reactions with gamma-glutamylcysteine and glutathione synthetase. Changes in ophthalmate level in mouse serum and liver extracts were closely correlated and ophthalmate levels increased significantly in conjunction with glutathione consumption. Overall, our results provide a broad picture of hepatic metabolite changes following acetaminophen treatment. In addition, we specifically found that serum ophthalmate is a sensitive indicator of hepatic GSH depletion, and may be a new biomarker for oxidative stress. Our method can thus pinpoint specific metabolite changes and provide insights into the perturbation of metabolic pathways on a large scale and serve as a powerful new tool for discovering low molecular weight biomarkers.     

Regulation of the Drosophila melanogaster protein, enhancer of rudimentary, by casein kinase II

The Drosophila melanogaster gene enhancer of rudimentary, e(r), encodes a conserved protein, ER. Most ER homologs share two casein kinase II (CKII) target sites. In D. melanogaster, these sites are T18 and S24. A third CKII site, T63, has been seen only in drosophilids. The conservation of these CKII sites, particularly T18 and S24, suggests a role for these residues in the function of the protein. To test this hypothesis, these positions were mutated either to alanine as a nonphosphorylated mimic or to glutamic acid as a phosphorylated mimic. The mutations were tested individually or in double or triple combinations for their ability to rescue either a wing truncation characteristic of the genotype e(r)(p1) r(hd1-12) or the synthetic lethal interaction between e(r)(p2) and the Notch allele N(nd-p). All of the substitutions as single mutations rescued both mutant phenotypes, arguing that individually the phosphorylation of the three residues does not affect ER activity. The double mutants T18A-S24A and T18E-S24E and the triple mutants T18A-S24A-T63A and T18E-S24E-T63E failed to rescue. Together the data support the following model for the regulation of ER by CKII. ER that is unphosphorylated at both T18A and S24 is inactive. CKII activates ER by phosphorylating either T18 or S24. Further phosphorylation to produce the doubly phosphorylated protein inactivates ER.     

Brief communication: mitochondrial DNA variation suggests extensive gene flow from Polynesian ancestors to indigenous Melanesians in the northwestern Bismarck Archipelago

Archaeological, linguistic, and genetic studies show that Austronesian (AN)-speaking Polynesian ancestors came from Asia/Taiwan to the Bismarck Archipelago in Near Oceania more than 3,600 years ago, and then expanded into Remote Oceania. However, it remains unclear whether they extensively mixed with indigenous Melanesians who had populated the Bismarck Archipelago before their arrival. To examine the extent of admixture between Polynesian ancestors and indigenous Melanesians, mitochondrial DNA (mtDNA) variations in the D-loop region and the cytochrome oxidase and lysine transfer RNA (COII/tRNA(Lys)) intergenic 9-bp deletion were analyzed in the following three Oceanian populations: 1) Balopa Islanders as AN-speaking Melanesians living in the northwestern end of the Bismarck Archipelago, 2) Tongans as AN-speaking Polynesians, and 3) Gidra as non-Austronesian-speaking Melanesians in the southwestern lowlands of Papua New Guinea. Phylogenetic analysis of mtDNA sequences revealed that more than 60% of mtDNA sequences in the Balopa Islanders were very similar to those in Tongans, suggesting an extensive gene flow from Polynesian ancestors to indigenous Melanesians. Furthermore, analysis of pairwise difference distributions for the D-loop sequences with the 9-bp deletion and the Polynesian motif (i.e., T16217C, A16247G, and C16261T) suggested that the expansion of Polynesian ancestors possessing these variations occurred approximately 7,000 years ago.     

Surface plasmon resonance-based highly sensitive immunosensing for brain natriuretic peptide using nanobeads for signal amplification

Site-specific metal-catalyzed oxidation (MCO) was applied to characterize the metal-binding site (MBS) of recombinant human prolactin (hPRL), which belongs to the hematopoietic cytokine family. Copper and ascorbate of various concentrations were used to initiate the oxidation of hPRL, and the oxidation-sensitive motifs were characterized and quantitated by mass spectrometry. Based on the results obtained with 10 microM Cu(2+) and 0.3-2.0mM ascorbate, we propose that the MBS in hPRL is composed of His27, His30, and His173. This result shows the similarity of hPRL to human growth hormone (hGH), a member of the same family as hPRL, where the MBS is composed of His18, His21, and Glu174.     

The luminal domain participates in the endosomal trafficking of the cation-independent mannose 6-phosphate receptor

Although the role of the cytoplasmic tail of the cation-independent mannose 6-phosphate receptor (CIMPR) has been well established in the receptor trafficking, that of the luminal domain is still controversial. We noticed that the peripheral distribution of GFP, fused to the transmembrane and cytoplasmic domains of CIMPR (G-CIMPR-tail), was distinct from that of endogenous CIMPR or of GFP fused to the full-length CIMPR (G-CIMPR-full). By live-cell imaging, trans-Golgi-network (TGN)-derived transport carriers containing G-CIMPR-full more frequently stopped and overlapped with transferrin-containing endosomes in the peripheral region than those containing G-CIMPR-tail. G-CIMPR-full was recycled back to the perinuclear TGN more slowly than that for G-CIMPR-tail, evidenced by fluorescence recovery after photobleaching analysis. Moreover, endogenous CIMPR and G-CIMPR-full, but not GFP-CIMPR-tail, drastically altered the characteristic distribution after treatment with chloroquine. A mutant receptor, G-CIMPR-full R/A, that cannot recognize the mannose 6-phosphate (M6P)-signal, behaved similarly to G-CIMPR-full, indicating that these differences are not attributable to the M6P-ligands binding situation. Interestingly, we also found that U18666A treatment was able to discriminate the M6P-ligand binding-dependent trafficking of CIMPR. Based on these findings, we propose that the CIMPR luminal domain is required for tight interaction with endocytic compartments, and retention by them, and that there are additional transport steps, in which the binding to M6P-ligands is involved.     

Pelotomaculum terephthalicum sp. nov. and Pelotomaculum isophthalicum sp. nov.: two anaerobic bacteria that degrade phthalate isomers in syntrophic association with hydrogenotrophic methanogens

An anaerobic phthalate isomer-degrading strain (JT^T) that we previously isolated was characterized. In addition, a strictly anaerobic, mesophilic, syntrophic phthalate isomer-degrading bacterium, designated strain JI^T, was isolated and characterized in this study. Both were non-motile rods that formed spores. In both strains, the optimal growth was observed at temperatures around 37°C and neutral pH. In syntrophic co-culture with the hydrogenotrophic methanogen Methanospirillum hungatei, both strains could utilize two or three phthalate isomers for growth, and produce acetate and methane as end products. Strain JT^T was able to grow on isophthalate, terephthalate, and a number of low-molecular weight aromatic compounds, such as benzoate, hydroquinone, 2-hydroxybenzoate, 3-hydroxybenzoate, 2,5-dihydroxybenzoate, 3-phenylpropionate in co-culture with M. hungatei. It could also grow on crotonate, hydroquinone and 2,5-dihydroxybenzoate in pure culture. Strain JI^T utilized all of the three phthalate isomers as well as benzoate and 3-hydroxybenzoate for growth in co-culture with M. hungatei. No substrates were, however, found to support the axenic growth of strain JI^T. Neither strain JT^T nor strain JI^T could utilize sulfate, sulfite, thiosulfate, nitrate, fumarate, Fe (III) or 4-hydroxybenzoate as electron acceptor. Phylogenetically, strains JT^T and JI^T were relatively close to the members of the genera Pelotomaculum and Cryptanaerobacter in ‘Desulfotomaculum lineage I’. Physiological and chemotaxonomic characteristics indicated that the two isolates should be classified into the genus Pelotomaculum, creating two novel species for them. Here, we propose Pelotomaculum terephthalicum sp. nov. and Pelotomaculum isophthalicum sp. nov. for strain JT^T and strain JI^T, respectively. The type strains are strains JT^T (= DSM 16121^T = JCM 11824^T = NBRC 100523^T) and JI^T (= JCM 12282^T = BAA-1053^T) for P. terephthalicum and P. isophthalicum, respectively.Nucleotide sequence accession number: The GenBank/EMBL/DDBJ accession numbers of the 16S rRNA gene sequences of strains JT^T and JI^T are AB091323 and AB232785, respectively     

Mechanical stretch upregulates IGFBP-1 secretion from decidualized endometrial stromal cells

Decidualization is an essential process of endometrial differentiation for embryo implantation and maintenance of pregnancy. Recently, uterine movement-induced mechanical stress was noticed to have possible effects on endometrial functions. In this study, we addressed the possible effect of mechanical stress on the process of decidualization of endometrial stromal cells (ESC). ESC were cultured on flexible-bottomed culture plates. After decidualization was achieved with estradiol and progesterone for 12 days, cultures were continued for 24 h with or without cyclic stretch (25% elongation) in serum-free conditions at a rate of 2 cycles/min using a computer-operated cell tension system. Concentrations of insulin-like growth factor-binding protein-1 (IGFBP-1), a marker of decidualization, in the conditioned medium were measured by specific ELISA, and IGFBP-1 mRNA expression in the ESC was measured by RT-PCR. Cyclic stretch remarkably increased IGFBP-1 secretion from decidualized ESC. It also increased IGFBP-1 mRNA in decidualized ESC. The increase in IGFBP-1 secretion was inhibited by actinomycin D but not by indomethacin, PD-98059, or H-89. Conditioned medium of decidualized ESC cultured with cyclic stretch increased IGFBP-1 secretion from decidualized ESC cultured under stationary conditions. These findings imply that uterine movement modulates decidualization of the endometrium and has a regulatory effect on reproduction.