Expression and Function of Allergin-1 on Human Primary Mast Cells

Mast cells (MC) play an important role in allergic and non-allergic immune responses. Activation of human MC is modulated by several cell surface inhibitory receptors, including recently identified Allergin-1 expressed on both human and mouse MC. Although Allergin-1 suppresses IgE-mediated, mast cell–dependent anaphylaxis in mice, the expression profile and function of Allergin-1 on human primary MC remains undetermined. Here, we established a seven-color flow cytometry method for assessing expression and function of a very small number of human primary MC. We show that Allergin-1S1, a splicing isoform of Allergin-1, is predominantly expressed on human primary MC in both bronchoalveolar lavage (BAL) fluid and nasal scratching specimens. Moreover, Allergin-1S1 inhibits IgE-mediated activation from human primary MC in BAL fluid. These results indicate that Allergin-1 on human primary MC exhibits similar characteristics as mouse Allergin-1 in the expression profile and function.     

Biochemical Features of a Catalytic Antibody Light Chain, 22F6, Prepared from Human Lymphocytes

Human antibody light chains belonging to subgroup II of germ line genes were amplified by a seminested PCR technique using B-lymphocytes taken from a human adult infected with influenza virus. Each gene of the human light chains was transferred into the Escherichia coli system. The recovered light chain was highly purified using a two-step purification system. Light chain 22F6 showed interesting catalytic features. The light chain cleaved a peptide bond of synthetic peptidyl-4-methyl-coumaryl-7-amide (MCA) substrates, such as QAR-MCA and EAR-MCA, indicating amidase activity. It also hydrolyzed a phosphodiester bond of both DNA and RNA. From the analysis of amino acid sequences and molecular modeling, the 22F6 light chain possesses two kinds of active sites as amidase and nuclease in close distances. The 22F6 catalytic light chain could suppress the infection of influenza virus type A (H1N1) of Madin-Darby canine kidney cells in an in vitro assay. In addition, the catalytic light chain clearly inhibited the infection of the influenza virus of BALB/c mice via nasal administration in an in vivo assay. In the experiment, the titer in the serum of the mice coinfected with the 22F6 light chain and H1N1 virus became considerably lowered compared with that of 22F6-non-coinfected mice. Note that the catalytic light chain was prepared from human peripheral lymphocyte and plays an important role in preventing infection by influenza virus. Considering the fact that the human light chain did not show any acute toxicity for mice, our procedure developed in this study must be unique and noteworthy for developing new drugs.     

Inhibitory effects of LPA1 on cell motile activities stimulated by hydrogen peroxide and 2,3-dimethoxy-1,4-naphthoquinone in fibroblast 3T3 cells

Reactive oxygen species (ROS) are known to mediate a variety of biological responses, including cell motility. Recently, we indicated that lysophosphatidic acid (LPA) receptor-3 (LPA₃) increased cell motile activity stimulated by hydrogen peroxide. In the present study, we assessed the role of LPA₁ in the cell motile activity mediated by ROS in mouse fibroblast 3T3 cells. 3T3 cells were treated with hydrogen peroxide and 2,3-dimethoxy-1,4-naphthoquinone (DMNQ) at concentrations of 0.1 and 1 μM for 48 h. In cell motility assays with Cell Culture Inserts, the cell motile activities of 3T3 cells treated with hydrogen peroxide and DMNQ were significantly higher than those of untreated cells. 3T3 cells treated with hydrogen peroxide and DMNQ showed elevated expression levels of the Lpar3 gene, but not the Lpar1 and Lpar2 genes. To investigate the effects of LPA₁ on the cell motile activity induced by hydrogen peroxide and DMNQ, Lpar1-overexpressing (3T3-a1) cells were generated from 3T3 cells and treated with hydrogen peroxide and DMNQ. The cell motile activities stimulated by hydrogen peroxide and DMNQ were markedly suppressed in 3T3-a1 cells. These results suggest that LPA signaling via LPA₁ inhibits the cell motile activities stimulated by hydrogen peroxide and DMNQ in 3T3 cells.     

Extracellular lipid metabolism influences the survival of ovarian cancer cells

Lysophosphatidic acid (LPA) is an extracellular lipid mediator consisting of a fatty acid and a phosphate group linked to the glycerol backbone. Here, we show that 1-oleoyl- and 1-palmitoyl-LPA, but not 1-stearoyl- or alkyl-LPA, enhance HNOA ovarian cancer cell survival. Other lysophospholipids with oleic or lauric acid, but not stearic acid, also induce the survival effects. HNOA cells have the lipase activities that cleave LPA to generate fatty acid. Oleic acid stimulates HNOA cell survival via increased glucose utilization. Our findings suggest that extracellular lysolipid metabolism might play an important role in HNOA cell growth.     

AMP‐activated protein kinase counteracts brain‐derived neurotrophic factor‐induced mammalian target of rapamycin complex 1 signaling in neurons

Growth factors and nutrients, such as amino acids and glucose, regulate mammalian target of rapamycin complex 1 (mTORC1) signaling and subsequent translational control in a coordinated manner. Brain‐derived neurotrophic factor (BDNF), the most prominent neurotrophic factor in the brain, activates mTORC1 and induces phosphorylation of its target, p70S6 kinase (p70S6K), at Thr389 in neurons. BDNF also increases mammalian target of rapamycin‐dependent novel protein synthesis in neurons. Here, we report that BDNF‐induced p70S6K activation is dependent on glucose, but not amino acids, sufficiency in cultured cortical neurons. AMP‐activated protein kinase (AMPK) is the molecular background to this specific nutrient dependency. Activation of AMPK, which is induced by glucose deprivation, treatment with pharmacological agents such as 2‐Deoxy‐d ‐glucose, metformin, and 5‐aminoimidazole‐4‐carboxamide ribonucleoside or forced expression of a constitutively active AMPKα subunit, counteracts BDNF‐induced phosphorylation of p70S6K and enhanced protein synthesis in cortical neurons. These results indicate that AMPK inhibits the effects of BDNF on mTORC1‐mediated translation in neurons.

     

Autocrine galectin-1 promotes collective cell migration of squamous cell carcinoma cells through up-regulation of distinct integrins

We found that high galectin-1 (Gal-1) mRNA levels were associated with invasive squamous cell carcinoma (SCC) cells that expressed Snail, an epithelial-to-mesenchymal transition (EMT) regulator. Both Gal-1 overexpression and soluble Gal-1 treatment accelerated invasion and collective cell migration, along with activation of cdc42 and Rac. Soluble Gal-1 activated c-Jun N-terminal kinase to increase expression levels of integrins α2 and β5, which were essential for Gal-1 dependent collective cell migration and invasiveness. Soluble Gal-1 also increased the incidence of EMT in Snail-expressing SCC cells; these were a minor population with an EMT phenotype under growing conditions. Our findings indicate that soluble Gal-1 promotes invasiveness through enhancing collective cell migration and increasing the incidence of EMT.     

Dephosphorylation of endogenous GABAB receptor R2 subunit and AMPK α subunits which were measured by in vitro method using transfer membrane

Protein phosphorylation can be regulated by changes in kinase activity, phosphatase activity, or both. GABA_B receptor R2 subunit (GABA_BR2) is phosphorylated at S783 by 5′-AMP-activated-protein kinase (AMPK), and this phosphorylation modulates GABA_B receptor desensitization. Since the GABA_B receptor is an integral membrane protein, solubilizing GABA_BR2 is difficult. To circumvent this problem and to identify specific phosphatases that dephosphorylate S783, we employed an in vitro assay based on dephosphorylation of proteins on PVDF membranes by purified phosphatases. Our method allowed us to demonstrate that S783 in GABA_BR2 is directly dephosphorylated by PP2A (but not by PP1, PP2B nor PP2C) in a dose-dependent and okadaic acid-sensitive manner. We also show that the level of phosphorylation of the catalytic subunit of AMPK at T172 is reduced by PP1, PP2A and PP2C. Our data indicate that PP2A dephosphorylates GABA_BR2(S783) less efficiently than AMPK(T172), and that additional phosphatases might be involved in S783 dephosphorylation.     

Extracellular Superoxide Dismutase Induced by Dopamine in Cultured Astrocytes

Under some pathological conditions in brain, a large amount of superoxide anion (O₂ ^?) is produced, causing various cellular damages. Among three isozymes of superoxide dismutase (SOD), extracellular (EC)-SOD should play a role to detoxify O₂ ^? in extracellular space; however, a little is known about EC-SOD in brain. Although dopamine (DA) stored in the synaptic vesicle is stable, the excess leaked DA is spontaneously oxidized to yield O₂ ^? and reactive DA quinones, causing damages of dopaminergic neurons. In the present study, we examined the effects of DA on SOD expression in cultured rat cortical astrocytes. By means of RT-PCR, all mRNA of three isozymes of SOD could be detected; however, only EC-SOD was increased by DA exposure for 24 h, dose-dependently. The expression of EC-SOD protein and the cell-surface SOD activity in astrocytes also increased with 100 μM DA exposure. The increase of EC-SOD mRNA by DA was inhibited by a DA transporter inhibitor, GBR12909, whereas it was not changed by DA receptor antagonists, SKF-83566 (D1) and haloperidol (D2). Furthermore, a monoamine oxidase inhibitor, pargyline, and antioxidants, N-acetyl-l-cysteine and glutathione, also did not affect the DA-induced expression of EC-SOD mRNA. On the other hand, an inhibitor of nuclear factor kappaB (NF-κB), ammonium pyrrolidine-1-carbodithioate, suppressed the DA-induced expression of EC-SOD mRNA. These results suggest that DA incorporated into the cells caused the induction of EC-SOD mRNA followed by the enhancements of EC-SOD protein level and the enzyme activity, and that NF-κB activation is involved in the mechanisms of the EC-SOD induction. The regulation of EC-SOD in astrocytes surrounding dopaminergic neurons may contribute to the defensive mechanism against oxidative stress in brain.     

On the diet of the Pharaoh Eagle Owl,Bubo ascalaphus (Savigny, 1809), in Qatar,with an overview of its feeding habits

The diet of Bubo ascalaphus in Qatar was assessed based on pellets collected from the first known nesting site of the species in the country. The pellets contained a total of 68 prey items, representing 9 different species: 4 mammals, 1 bird, 1 reptile, and at least 3 scorpions. Mammals clearly comprised the major food source (89.7% and 97.7% in frequency and biomass respectively). Our data suggest that Pharaoh Eagle Owls are opportunistic predators that feed on a variety of prey depending on their temporal/spatial availability, which is consistent with previous studies. A literature review clearly suggests that Eagle Owls in arid to semi-arid environments are opportunistic predators with small mammals being their main prey. Predation on migrating Blue-cheeked Bee-eaters Merops persicus supports this hypothesis.