Cyclic biphalin analogues with a novel linker lead to potent agonist activities at mu,delta, and kappa opioid receptors

In an effort to improve biphalin’s potency and efficacy at the µ-(MOR) and δ-opioid receptors (DOR), a series of cyclic biphalin analogues 1–5 with a cystamine or piperazine linker at the C-terminus were designed and synthesized by solution phase synthesis using Boc-chemistry. Interestingly, all of the analogues showed balanced opioid agonist activities at all opioid receptor subtypes due to enhanced κ-opioid receptor (KOR) activity. Our results indicate that C-terminal flexible linkers play an important role in KOR activity compared to that of the other cyclic biphalin analogues with a hydrazine linker. Among them, analogue 5 is a potent (Ki?=?0.27, 0.46, and 0.87?nM; EC₅₀?=?3.47, 1.45, and 13.5?nM at MOR, DOR, and KOR, respectively) opioid agonist with high efficacy. Based on the high potency and efficacy at the three opioid receptor subtypes, the ligand is expected to have a potential synergistic effect on relieving pain and further studies including in vivo tests are worthwhile.     

Generation of a cytotoxic T-lymphocyte response using a Salmonella antigen-delivery system

We have constructed a general-use vector for the cloning and stable expression of foreign genes in the chromosome of attenuated Salmonella typhimurium. Using this chromosomal expression vector (CEV), we expressed the circumsporozoite (CS) gene of the mouse malaria Plasmodium yoelii in an aroA S. typhimurium strain. Mice immunized with CS-expressing Salmonella recombinants mount a CS-specific cytotoxic T-lymphocyte (CTL) response. This is the first demonstration that attenuated Salmonella can elicit a specific CTL response to a foreign protein in mice. The ability to easily and stably express foreign genes from the Salmonella chromosome and the generation of specific CTL greatly expands the potential of Salmonella as an antigen-delivery system.     

Truncated light-harvesting chlorophyll antenna size in <Emphasis Type="Italic">Chlorella vulgaris</Emphasis> improves biomass productivity

Microalgae have been proposed as eco-friendly feedstocks for biodiesel production, because they accumulate large amounts of lipids and increase their biomass through photosynthesis. However, the photosynthetic efficiency of microalgae is too low for this strategy to be economically feasible. In an effort to overcome this issue, random mutants with reduced chlorophyll antenna size were generated by ethyl methanesulfonate (EMS)-mediated mutagenesis of Chlorella vulgaris. The antenna size mutant, herein designated E5, exhibited 56.5 and 75.8 % decreases in chlorophyll a and b contents, respectively, with significant reductions in the expression levels of peripheral light-harvesting antenna proteins in photosystem II. The saturated photosynthetic activity and electron transport rate of the E5 mutant were significantly higher and also showed reduced non-photochemical quenching (NPQ), compared to those of the wild type. Consequentially, the E5 mutant cultures achieved 44.5 % improvement in biomass productivity under high light (200 μmol photons m^?2 s^?1). These results suggest that improving the photosynthetic efficiency of microalgae could greatly enhance their biomass production, and such mutant strains can be applicable for large-scale outdoor cultivation which is typically exposed to high light intensity.     

Phosphorylation of SMC1 by ATR is required for desferrioxamine (DFO)-induced apoptosis

DNA damage signaling pathways are initiated in response to chemical reagents and radiation damage, as well as in response to hypoxia. It is implicated that structural maintenance of chromosomes 1 (SMC1) is not only a component of the cohesion complex but also facilitates the activation of DNA damage checkpoint proteins. Here, we studied the mechanism of DNA damage checkpoint activated by ATR–SMC1 pathway when cells are treated with desferrioxamine (DFO), a hypoxia-mimetic reagent. We show that DFO treatment induces phosphorylation of SMC1 at Ser966, NBS1 at Ser343, Chk1 at Ser317, Chk2 at Thr68, and p53 at Ser15. Among these sites, phosphorylation of SMC1, NBS1, and Chk1 by DFO are mediated by ATR as it is greatly reduced in both ATR-deficient human fibroblasts and HCT116 human colon cancer cells in which ATR is heterozygously mutated, whereas these proteins are phosphorylated in cells deficient for ATM and DNA-PKcs. DFO-induced apoptosis is decreased in ATR-mutant HCT116 cells, although p53 is normally activated in those cells. Expression of SMC1 S966A in which Ser966 is substituted to Ala attenuates apoptosis and phosphorylation of Chk1 at Ser317 after DFO treatment, although levels of HIF1α are not significantly changed. These results suggest that DFO induces apoptosis through the ATR–SMC1 arm of the pathway.     

Inhibition of Endoplasmic Reticulum Stress-induced Apoptosis by Silkworm Storage Protein 1

The endoplasmic reticulum (ER) plays essential roles indispensable for cellular activity and survival, including functions such as protein synthesis, secretory and membrane protein folding, and Ca²⁺ release in cells. The ER is sensitive to stresses that can lead to the aggregation and accumulation of misfolded proteins, which eventually triggers cellular dysfunction; severe or prolonged ER stress eventually induces apoptosis. ER stress-induced apoptosis causes several devastating diseases such as atherosclerosis, neurodegenerative diseases, and diabetes. In addition, the production of biopharmaceuticals such as monoclonal antibodies requires the maintenance of normal ER functions to achieve and maintain the production of high-quality products in good quantities. Therefore, it is necessary to develop methods to efficiently relieve ER stress and protect cells from ER stress-induced apoptosis. The silkworm storage protein 1 (SP1) has anti-apoptotic activities that inhibit the intrinsic mitochondrial apoptotic pathway. However, the role of SP1 in controlling ER stress and ER stress-induced apoptosis has not been investigated. In this paper, we demonstrate that SP1 can inhibit apoptosis induced by a well-known ER stress inducer, thapsigargin, by alleviating the decrease in cell viability and mitochondrial membrane potential. Interestingly, SP1 significantly blocked increases in CHOP and GRP78 expression as well as ER Ca2+ leakage into the cytosol following ER stress induction. This indicates that SP1 protects cells from ER stressinduced apoptosis by functioning as an upstream inhibitor of apoptosis. Therefore, studying SP1 function can offer new insights into protecting cells against ER stress-induced apoptosis for future applications in the biopharmaceutical and medicine industries.     

Constitutive production of human leptin by fed-batch culture of recombinant rpoS- Escherichia coli

High-level production of human leptin by fed-batch culture of recombinant Escherichia coli using constitutive promoter system was investigated. For the constitutive expression of the obese gene encoding human leptin, the strong constitutive HCE promoter cloned from the D-amino acid aminotransferase gene of Geobacillus toebii was used. To develop an optimal host-vector system, several different recombinant E. coli strains were compared for leptin production. In flask cultures, E. coli FMJ123, which is a rpoS mutant strain, showed the highest level of leptin production (41% of total proteins). By comparing the expression levels of leptin in several different rpoS- and rpoS+ strains, it could be concluded that rpoS mutation positively affected constitutive production of leptin. For the large-scale production of human leptin, fed-batch cultures of recombinant E. coli FMJ123 were carried out using three different feeding solutions--chemically defined, yeast extract-containing, and casamino acid-containing feeding solutions. Among these, the use of casamino acid-containing feeding solution allowed production of leptin up to 2.1 g/L, which was 2.1- and 1.8-fold higher than that obtained with chemically defined and yeast extract-contained feeding solutions, respectively. These results suggest that the HCE promoter can be used for the efficient production of leptin, and most likely other recombinant proteins, in a constitutive manner.     

Crystal structure of CelM2, a bifunctional glucanase-xylanase protein from a metagenome library

Degradation of polysaccharides by cellulases and xylanases plays an important role in the carbon cycle, but only occurs in plant cell walls, a few bacteria and some animals. This process is also critical in processes such as biomass degradation and fuel production in the conversion cycles of cellulosic biomass. The enzyme CelM2 is bifunctional, because it is able to effectively hydrolyze barley glucan and xylan. Here, we show the crystal structure of the bifunctional enzyme CelM2, isolated from a metagenome library, and describe the sequence information and structure of its two domains. We believe that CelM2 is attractive as an industrial enzyme and that the structural results presented herein provide insights that are relevant to the genetic engineering of multifunctional enzymes.     

Activation of Toll-like receptor 4 is associated with insulin resistance in adipocytes

Chronic inflammation is closely associated with metabolic disorders such as obesity and type 2 diabetes, however, the underlying mechanism is unclear. Toll-like receptors (TLRs) play a key role in innate immune response as well as inflammatory signals. Here, we observed that mRNA level of TLR4 was induced during adipocyte differentiation and remarkably enhanced in fat tissues of obese db/db mice. In addition, activation of TLR4 with either LPS or free fatty acids stimulated NFkappaB signaling and expression of inflammatory cytokine genes, such as TNFalpha and IL-6 in 3T3-L1 adipocytes. Furthermore, we discovered that TLR4 activation in 3T3-L1 adipocytes provoked insulin resistance. Taken together, these results suggest that activation of TLR4 in adipocyte might be implicated in the onset of insulin resistance in obesity and type 2 diabetes.