FcεRI-induced mast cell cytokine production critically involves an aspartic acid residue (D234) in the C-terminal intracellular domain of the FcεRIβ chain

The high affinity IgE Fc receptor (FcεRI) β chain is well implicated as a signal amplifier through the immunoreceptor tyrosine-based activation motif (ITAM) in its C-terminal intracellular region. Our previous study, however, demonstrated that mutation in all of the three tyrosine residues within the FcεRIβ ITAM did not impair FcεRI-induced cytokine production, suggesting a possible functional region other than the ITAM. To investigate the ITAM-independent mechanism by which FcεRIβ regulates FcεRI-induced cytokine production, mouse mast cells expressing various FcεRIβ mutants were generated. We observed that truncation of the FcεRIβ C-terminus downstream of the ITAM resulted in a considerable decrease in FcεRI-induced IL-6 production but not degranulation. Furthermore, mutagenesis of a single C-terminal aspartic acid (D234) to alanine (β-D234A) also significantly impaired IL-6 production. In addition, the similarity between the circular dichroism (CD) spectra of the wild type and β-D234A suggests that the secondary structure of the FcεRIβ C-terminus was not affected by the D234A mutation. Consistently, we did not observe any effect of this mutation on FcεRI-induced tyrosine phosphorylation of FcεRIβ. These observations strongly suggest a novel signaling pathway mediated by the cytoplasmic tail downstream of the FcεRIβ ITAM.     

A gain-of-function screen identifies wdb and lkb1 as lifespan-extending genes in Drosophila

The insulin/insulin-like growth factor (IGF) and the target of rapamycin (TOR) signaling pathways are known to regulate lifespan in diverse organisms. However, only a limited number of genes involved in these pathways have been examined regarding their effects on lifespan. Through a gain-of-function screen in Drosophila, we found that overexpression of the wdb gene encoding a regulatory subunit of PP2A, and overexpression of the lkb1 gene encoding a serine/threonine kinase, reduced organ size and extended lifespan. Overexpression of wdb also reduced the level of phosphorylated AKT, while overexpression of lkb1 increased the level of phosphorylated AMPK and decreased the level of phosphorylated S6K. Taken together, our results suggest that wdb- and lkb1-dependent lifespan extension is mediated by downregulation of S6K, a downstream component of the insulin/IGF and TOR signaling pathways.     

Binding of glyceraldehyde-3-phosphate dehydrogenase to the cis-acting element of structure-anchored repression in ccn2 mRNA

Studies increasingly indicate that inflammation induced by β-amyloid (Aβ) contributes to the progression of Alzheimer’s disease (AD). How to inhibit the enhanced production of proinflammatory cytokines stimulated by Aβ is an important research subject for the treatment of AD. In this study, we investigated the inhibitory effect and the molecular mechanism of the lipoxin A₄ (LXA₄) on the production of interleukin-1β (IL-1β) and tumor necrosis factorα (TNFα) induced by β-amyloid in the cortex and hippocampus of mice, and in Aβ-stimulated BV2 cells, a mouse microglial cell line. LXA₄ down-regulated the protein expression of IL-1β and TNFα, attenuated the gene expressions of IL-1β and TNFα, inhibited the degradation of IκBα, inhibited translocation of NF-κB p65 subunit into the nucleus induced by β-amyloid in the cortex and hippocampus of mice, and in Aβ-stimulated BV2 cells, and the inhibitory effects were dose dependently elevated. Our findings suggest that LXA₄ inhibits the production of IL-1β and TNFα induced by β-amyloid in the cortex and hippocampus of mice, and in BV2 microglial cells via the NF-κB signal pathway.     

Application of a water jet system to the pretreatment of cellulose

Plant cellulose is the most abundant organic compound on earth. Technologies for producing cellulose fiber or improving the enzymatic saccharification of cellulose hold the key to biomass applications. A technology for atomizing biomass without strong acid catalysis remains to be developed. The water jet is a well-known device used in machines (e.g., washing machines, cutters, and mills) that use high-pressure water. In this study, we examined whether a water jet system could be used to atomize crystalline cellulose, which comprises approximately 50% of plant biomass. The Star Burst System manufactured by Sugino Machine Limited (Sugino Machine; Toyama, Japan) is a unique atomization machine that uses a water jet to atomize materials and thereby places lower stress on the environment. After treatment with this system, the crystalline cellulose was converted into a gel-like form. High-angular annular dark-field scanning transmission electron microscopy showed that the cellulose fibers had been converted from a solid crystalline into a matrix of cellulose nanofibers. In addition, our results show that this system can improve the saccharification efficiency of cellulases by more than three-fold. Hence, the Star Burst System provides a new and mild pretreatment system for processing biomass materials.     

Functional analysis of C-type lysozyme in penaeid shrimp

Lysozyme is an enzyme that cleaves the β-1,4-glycosidic linkages between N-acetylmuramic acid and N-acetylglucosamine in peptidoglycan, leading to bacterial lysis. Recently, lysozyme has been found to have anti-HIV and anti-cancer properties in mammals. However, most functional analyses were done in vitro using purified or recombinant lysozyme protein. Here, we used RNA interference to silence c-type lysozyme expression in penaeid shrimp, Marsupenaeus japonicus, to analyze the function of lysozyme in vivo. Silencing of lysozyme expression by dsRNA lysozyme (dsLYZ) led to 100% mortality without any artificial bacterial infection in 5 days. Lysozyme deficiency caused the number of hemocytes in hemolymph to decrease from 1.3 × 10(7) to 2.3 × 10(6) cells/ml and caused the number of bacteria to increase from 78 to 764 colony-forming units/ml. Suppression of bacterial growth using oxytetracycline and kanamycin showed improvement in mortality, suggesting that shrimp mortality post- dsLYZ injection can be attributed to bacterial growth in the shrimp hemolymph. The majority of the bacteria, identified by 16 S rRNA analysis, were Gram-negative species such as Vibrio and Pseudomonas. Furthermore, PKH26 staining showed that the dsLYZ-injected shrimp were unable to eliminate non pathogenic Escherichia coli or Staphylococcus aureus in 24 h. These data suggest that c-type lysozyme in shrimp serves to regulate the growth of bacterial communities, particularly Gram-negative bacteria, in the hemolymph.     

EPR study of 1Asp-3Cys ligated 4Fe-4S iron-sulfur cluster in NB-protein (BchN-BchB) of a dark-operative protochlorophyllide reductase complex

Dark-operative protochlorophyllide oxidoreductase, a nitrogenase-like enzyme, contains two [4Fe–4S] clusters, one in the L-protein ((BchL)₂) and the other in the NB-protein ((BchN–BchB)₂). The reduced NB-cluster in the NB-protein, which is ligated by 1Asp/3Cys residues, showed a broad S = 3/2 electron paramagnetic resonance signal that is rather rare in [4Fe–4S] clusters. A 4Cys-ligated NB-cluster in the mutated variant BchB–D36C protein, in which the Asp36 was replaced by a Cys, gave a rhombic normal S = 1/2 signal and lost the catalytic activity. The results suggest that Asp36 contributes to the low redox potential necessary to reduce protochlorophyllide.     

A defect of peroxisomal membrane protein 38 causes enlargement of peroxisomes

Peroxisome proliferation occurs through enlargement, elongation and division of pre-existing peroxisomes. In the Arabidopsis apem mutant, apem3, peroxisomes are dramatically enlarged and reduced in number, revealing a defect in peroxisome proliferation. The APEM3 gene was found to encode peroxisomal membrane protein 38 (PMP38). To examine the relative role of PMP38 during proliferation, a double mutant was constructed consisting of apem3 and the peroxisome division mutant, apem1, in which a defect in dynamin-related protein 3A (DRP3A) results in elongation of peroxisomes. In the double mutant, almost all peroxisomes were predominantly enlarged but not elongated. DRP3A is still able to localize at the peroxisomal membrane on enlarged peroxisomes in the apem3 mutants. PMP38 is revealed to be capable of interacting with itself, but not with DRP3A. These results indicate that PMP38 has a role at a different step that requires APEM1/DRP3A. PMP38 is expressed in various tissues throughout the plant, indicating that PMP38 may participate in multiple unidentified functions in these tissues. PMP38 belongs to a mitochondrial carrier family (MCF) protein. However, unlike Arabidopsis nucleotide carrier protein 1 (AtPNC1) and AtPNC2, two other peroxisome-resident MCF proteins that function as adenine nucleotide transporters, PMP38 has no ATP or ADP transport activity. In addition, unlike AtPNC1 and AtPNC2 knock-down plants, apem3 mutants do not exhibit any gross morphological abnormalities. These results demonstrate that APEM3/PMP38 plays a role distinct from that of AtPNC1 and AtPNC2. We discuss possible mechanism of enlargement of peroxisomes in the apem3 mutants.