Deletion and alanine mutation analyses for the formation of active homo- or hetero-dimer complexes of mouse choline kinase-alpha and -beta

Choline kinase (CK) is the first-step regulatory enzyme for the biosynthesis of phosphatidylcholine in all mammalian cells. It exists as at least three isoforms (alpha1, alpha2 and beta) that are encoded by two separate genes termed ck-alpha and ck-beta. The active enzyme has been proposed to consist of either their homo- or hetero-dimeric forms. Here, we report on the identification of several essential domains and amino acid residues involved in their active dimer formation. Full-length cDNAs or their truncated or alanine-mutated versions for mouse CK-alpha1 and CK-beta tagged with either HA or Myc at their N-termini were expressed in COS-7 cells. Each dimer formation was analyzed by immuno-precipitation followed by Western blotting. Kinetic analysis for CK reaction was performed with different expression products. Both the N-terminal domain-1 and C-terminal portions (E424-K430 for CK-alpha1 and Q379-K385 for CK-beta) were shown to be critical for the formation of active homo- or hetero-dimer complex. Interestingly, D320 in the CK-motif of CK-alpha1 was found to be essential for alpha1/alpha1 homo-dimerization but not for alpha1/beta hetero-dimerization. A mutation of the corresponding D276 of CK-beta to A276 did not show any effect on either its homo- or hetero-dimerization but it caused a strong inhibition of CK activity in either case.     

Stability of protease in organic solvent: structural identification by solid-state NMR of lyophilized papain before and after 1-propanol treatment and the corresponding enzymatic activities

Lyophilized enzyme powder is often used in organic solvents. However, the enzymatic activity decreases during the reaction process. In the present study, the relation between structural stability and enzymatic activity in an organic solvent was investigated. 13C cross-polarization magic angle spinning NMR spectroscopy was used to determine the secondary structure of lyophilized papain in the solid-state. Deconvolution of the peaks of the backbone carbonyl carbons suggested that the proportion of beta-sheet conformation increased after lyophilization from a phosphate buffer solution. The esterification of N-benzyloxycarbonyl phenylalanylalanine amide was attempted using the lyophilized papain as a catalyst in anhydrous 1-propanol. The yield of ester was 46.1% after 48 h at 50 degrees C, but this reaction slowed remarkably after 48 h. When the lyophilized papain was suspended in anhydrous 1-propanol for 7 days without the substrate, the proportion of beta-sheet conformation was further increased and the suspended papain had no activity. These results suggest that the increase in beta-sheet conformation caused inactivation of papain. The increase in beta-sheet conformation caused by both lyophilization and suspension in propanol was found, which was related to a decrease in enzymatic activity.     

Normal specification of the extraembryonic lineage after somatic nuclear transfer

To examine the establishment and maintenance of trophectoderm (TE) lineage in somatic cloned blastocysts, the expression of Cdx2, a key molecule for specification of TE fate, was immunohistochemically examined simultaneously with Oct4 expression. Cloned mouse embryos were made by nuclear transfer using cumulus cells, tail-tip fibroblasts, and embryonic stem cells. After 96 h of culture, the rates of Oct4-expressing blastocysts were as low as 50% and 60% for cumulus and fibroblast clones, respectively. However, regardless of Oct4 expression, the majority of those cloned blastocysts (> 90%) normally expressed Cdx2. Thus, even though somatic cloned embryos have reduced potential to produce the inner cell mass lineage, the TE lineage can be established and maintained.     

Chorioallantoic placenta defects in cloned mice

Somatic cell nuclear transfer technology has been applied to produce live clones successfully in several mammalian species, but the success rates are very low. In mice, about half of the nuclear transfer embryos undergo implantation, but very few survive to term. We undertook detailed histological analyses of placentas from cloned mouse embryos generated from cumulus cells at 10.5 dpc of pregnancy, by which stage most clones have terminated their development. At 10.5 dpc, the extraembryonic tissues displayed several defined histological patterns, each reflecting their stage of developmental arrest. The most notable abnormality was the poor development of the spongiotrophoblast layer of diploid cells. This is in contrast to the placental hyperplasia frequently observed in somatic clones at 12.5 dpc or later stages. A variety of structural abnormalities were also observed in the embryos. Both placental and embryonic defects likely contribute to the low success rate of the mouse clones.     

Brain insulin resistance accelerates Aβ fibrillogenesis by inducing GM1 ganglioside clustering in the presynaptic membranes

Type 2 diabetes mellitus is thought to be a significant risk factor for Alzheimer's disease. Insulin resistance also affects the central nervous system by regulating key processes, such as neuronal survival and longevity, learning and memory. However, the mechanisms underlying these effects remain uncertain. To investigate whether insulin resistance is associated with the assembly of amyloid β-protein (Aβ) at the cell surface of neurons, we inhibited insulin-signalling pathways of primary neurons. The treatments of insulin receptor (IR)-knockdown and a phosphatidylinositol 3-kinase inhibitor (LY294002), but not an extracellular signal-regulated kinase inhibitor, induced an increase in GM1 ganglioside (GM1) levels in detergent-resistant membrane microdomains of the neurons. The aged db/db mouse brain exhibited reduction in IR expression and phosphorylation of Akt, which later induced an increase in the high-density GM1-clusters on synaptosomes. Neurons treated with IR knockdown or LY294002, and synaptosomes of the aged db/db mouse brains markedly accelerated an assembly of Aβs. These results suggest that ageing and peripheral insulin resistance induce brain insulin resistance, which accelerates the assembly of Aβs by increasing and clustering of GM1 in detergent-resistant membrane microdomains of neuronal membranes.     

Efficient expression of recombinant soluble human FcγRI in mammalian cells and its characterization

The extracellular domain of human FcγRI which interacts with a human IgG was expressed as recombinant soluble human FcγRI (rshFcγRI) by Chinese hamster ovary (CHO) cell. Stable CHO cell clones with efficient expression of rshFcγRI were established based on a dihydrofolate reductase (DHFR)/methotrexate (MTX) gene-amplification system. The CHO clones efficiently produced rshFcγRI under high-density continuous culture in a bioreactor. After 53 days of culture, the number of cells had reached approximately 4 × 10? cells/mL in the bioreactor and the average production of rshFcγRI had reached 7.4 mg L-medium?1 day?1. Secreted rshFcγRI was purified to a homogeneous state using cation exchange and affinity chromatographies. The binding affinities of rshFcγRI to human IgG subclasses were determined using surface plasmon resonance analysis. The binding affinities of rshFcγRI to human IgG1/κ and IgG3/κ were high (1.59 × 10?1? and 2.81 × 10?1? M, respectively), whereas that of rshFcγRI to human IgG4/κ was lower binding affinity (1.41 × 10?? M). Binding to IgG2/κ was not detectable. Examination of circular dichroism spectra indicated that rshFcγRI was rich in β-structures and loop or turn structures, but there were few α-helices. These results may be valuable for further studies of the structure and function of human FcγRI.     

Genome-wide analysis of abnormal H3K9 acetylation in cloned mice

Somatic nuclear transfer is a cloning technique that shows great promise in the application to regenerative medicine. Although cloned animals are genetically identical to their donor counterparts, abnormalities in phenotype and gene expression are frequently observed. One hypothesis is that the cause of these abnormalities is due to epigenetic aberration. In this report, we focused our analysis on the acetylation of histone H3 at lysine9 (H3K9Ac). Through the use of whole genome tiling arrays and quantitative PCR, we examined this epigenetic event and directly compared and assessed the differences between a cloned mouse (C1) and its parental nuclear donor (D1) counterpart. We identified 4720 regions of chromosomal DNA that showed notable differences in H3K9Ac and report here many genes identified in these hyper- and hypo-acetylated regions. Analysis of a second clone (C2) and its parental donor counterpart (D2) for H3K9Ac showed a high degree of similarity to the C1/D1 pair. This conservation of aberrant acetylation is suggestive of a reproducible epigenetic phenomenon that may lead to the frequent abnormalities observed in cloned mice, such as obesity. Furthermore, we demonstrated Crp which was identified as a hyper-acetylated gene in this study is related to the body mass, suggesting that Crp is a possible candidate of a cause for the abnormal obesity in cloned mice. In this, one of the first reports describing genome-wide epigenetic aberration between parental and nuclear transfer-cloned mammals, we propose that aberrant acetylation of histones (H3K9Ac) flanking promoter regions highly correlates with gene-expression and may itself be an epigenetic change that accounts for variable expression patterns observed in cloned animals.     

Temperature regulates tuber-inducing lipoxygenase-derived metabolites in potato (Solanum tuberosum)

Temperature is one of the major environmental factors affecting potato tuberization. It has been suggested that lipoxygenase (LOX) mediates between temperature and tuber induction. In this study, the contents of the LOX-derived metabolites hydroperoxylinolenic acid (HPOT), jasmonic acid (JA), tuberonic acid (TA) and tuberonic acid glucoside (TAG) were analyzed in leaves of potatoes growing at different temperatures. At low, tuber-inducing temperature, endogenous levels of JA, TA and TAG rise, indicating their crucial role in tuber induction. The concentration of 13(S)-HPOT seems not to be directly affected by temperature. Instead, the molecule has only a short half-life in leaves and is readily metabolized.