Shalini+Chudasama

Platelet factor 4-heparin complexes trigger immune responses independently of the MyD88 pathway May 13, 2009

This article was regarding Heparin-induced thromobocytopenia and the immune response involved. This immune response results in antibodies attaching to complexes of platelet factor-4 (pf4) and heparin. A lab at Duke was investigating the cause of the initiation of the immune response. It was known from previous research that mice injected with a combination of murine pf4(mpf4) and heparin, but not either alone, were able to develop antibodies to the complex with properties similar to that of human antibodies. By looking at Toll-like receptors (TLRs), a group of cell-surface pattern recognition receptors that recognize particular structures on foreign cells, the scientists were able to study the mechanisms in which antigen-presenting cells recognize properties of mpf4/heparin complexes. The TLRs are different on different types of cells, and activate intracellular signaling cascades via an adaptor protein MyD88. Mice without this protein have problems with both innate and adaptive immune responses; therefore the researchers were trying to determine if mpf4/heparin complexes trigger immune activation through TLRs in mice without the MyD88 protein. Using wild type MyD88 and heterozygous mice as controls, and MyD88 mice as the experimental group, the scientists injected the mice with antigen solution comprised of mpf4 and heparin, or control solutions with albumin. It was observed that the wild type mice generated significant amounts of antibodies, but mice lacking in MyD88 and heterozygotes could also generate antibodies in amounts less than, but still comparable to the wild types. The data recorded shows that TLR signaling through MyD88 is not necessary for HIT antibody formation. Future questions that may arise from this research include the exact role of mpf4 and heparin in immune activation, and the extent to which structural determinates are recognized by antigen-specific receptors or other pattern recognition receptors.

Suvarna, Shayela et al. “Wiley InterScience :: Article :: HTML Full Text.” //Wiley InterScience// 28 May 2008. 12 May 2009 .

Silk Worm Article Summary May 8, 2009

This article was written by Chinese scientists investigating the nutritional value of silkworms and the silk they produce as feasible sources of proteins for humans in space. Dietary components of astronauts have been investigated by various researchers across the globe. NASA has been working with space growth systems of plants such as wheat, soybeans, and potatoes to serve as sources of edible starch, protein, and vitamins. Fish and amphibians have also been investigated as sources of protein; however, they are very sensitive to the conditions of their aquatic environment. Poultry is not a feasible source of protein due to their high maintenance involving a large space, large amounts of feed necessary, and the amount of metabolic waste they produce and the methods necessary to treat it. Silkworms present such problems and are a potential solution to a sustained protein source in space. Their pupae contain 18 amino acids, 8 of which are essential for humans, and they have twice the amount of these amino acids as pork. A culture takes 25 days to grow, but only silkworms in their fifth instar stage can be processed into powder. The silk itself is also used as a major source of protein; the cocoons are boiled, hydrolyzed, filtered, purified, and then ground into powder. Not only is this powder an excellent source of protein, it is also able to lower blood-glucose, without causing glycopenia over long-term consumption. In terms of practicality of silkworms in space, the waste products produced by silkworms (and humans) in space, they can be used to fertilize the plants. The influence of radiation and microgravity on silkworms hasn’t been investigated yet, but there is a method of incubation for cultures that was developed in Germany. Future directions for this include incorporating the silkworm based powder into food consumed by astronauts.

Yang, Yunan et al. “Silkworms culture as a source of protein for humans in space.” //Advances in Space Research// 43.8 (2009): 1236-1242.(Yang et al.)

Article Summary on N-glycosylation

Scientists in Australia were trying to better understand the role of N-glycosylation (NG) by removing individual N-glycans, as compared to removing putative NG sites. Glycosylation is the process of linking sugar chains to proteins or lipids, usually on the surface of the cell. NG is a post-translational protein modification involving N-linked glycans, and is involved in many cellular processes such as protein folding, secretion, and cell communication. However, glycosylation is very complex because of the different forms N-glycans can take, and their ability to occupy the same glycosylation site. Generally NG occurs at a particular asparagine sequence. In general, N-linked glycans confer stability and steric protection from proteases for proteins and non-specific interactions, and help maintain quaternary structure.

Deglycosylation is usually achieved by converting the asparagine in the particular amino acid sequence to glutamine or alanine. It can also be done by using inhibitors of glycoprotein-processing enzymes, and this simply blocks the first step in glycoprotein synthesis. These methods usually remove most NG sites, which results in significantly reduced secretion of the active enzyme. However, targeting individual sites leads to varied effects. In one case, when three of 8 potential glycosylation sites were individually removed, the mutants had reduced half lives. When they removed a certain two, there was little effect, but removal of the third produced an inactive enzyme. In most cases, removing one or more N-glycans results in reduced catalytic activity. However, there are rare occasions when the enzyme activity is increased with removal of a single NG site.

Implications of this include targeting (de)glycosylation as a new way of treating disease. There is evidence of NG's role in regulating immune function, development/progression of cancer, inflammation, muscular dystrophy and many more diseases. Natural mutations of protein NG sites have a significant phenotypic effect, thus making defective enzyme glycosylation an important marker for disease. Skropeta, Danielle. “The effect of individual N-glycans on enzyme activity.” //Bioorganic & Medicinal Chemistry// 17.7 (2009): 2645-2653.(Skropeta)

Inhibiting Acid Ceramidase

Scientists at the University of South Carolina were developing molecules to inhibit the activity of the lysosomal enzyme acid ceramidase (ACDase). The enzyme is responsible for converting ceramide, a cell growth modulator, to sphingosine 1-phosphate (S1P), an anti-apoptotic tumor protective agent**.** These scientists were trying to design/synthesize inhibitors of ACDase so as to induce apoptosis in cancerous cells. It was known that B13 molecules had a high inhibitory effect on ACDase in vitro, but not in vivo. These scientists then synthesized an aromatic analog of B13 which they called LCL204. LCL204 inhibited ACDase, but also induced lysosomal destabilization and proteolytic degradation of the lysosome. From the two extremes of B13 and LCL204, the scientists hybridized the two molecules in various ways, and measured the efficacy of the newly synthesized molecules. They determined LCL464 to be the most effective, because it inhibited ACDase in vitro and in vivo, but did not cause lysosomal dysfunction, nor degradation of ACDase. The implications of LCL464 are its use in chemotherapeutic drugs for site-specific ACDase inhibition.

Bai, Aiping et al. “Synthesis and bioevaluation of ω-//N//-amino analogs of B13.” __Bioorganic and Medicinal Chemistry.__ 17(2009): 1840-1848.

People across the world drink tea for its antioxidants and other health-promoting properties. However, it is possible that the quality of tea is affected by pollutants, which brings about the question of how significant the effects are. A group of researchers in China investigated the effect of a type of polycyclic aromatic hydrocarbon, phenanthrene, on the chemical composition and enzyme activity in fresh tea leaves. The researchers set up two groups, one to serve as the control, and the other to serve as the experimental group which would receive phenanthrene every day for seven days. The researchers already knew, from their own previous research, that only 5% of the phenanthrene taken in by the roots is translocated to the tea leaves; however, this small percentage was still enough to show an obvious aging process in the leaves of the experimental group (they were yellow and crisp). The scientists used these leaves and performed activity reaction systems, spectrophotometry, and HPLC to measure the amounts of enzymes which serve as free-radical scavengers (anti oxidants). The specific enzymes the researchers were monitoring were superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT ); all of which are free-radical scavengers. Analysis of the data showed a notable decrease overall in the amount of these three enzymes, as well as a decrease in the amount of caffeine, sugar, and protein. It is interesting to note that phenanthrene caused levels of amino acids and caffeine to peak on the third day, but at the end of the seven days, these levels dropped below their initial value. This raises several areas for future researching, including development of a substance to treat tea leaves with so that they are immune to phenanthrene’s effects, methods of eradicating phenanthrene, or methods of supplementing tea leaves with antioxidants to make up for the loss due to phenanthrene.

Mei, Xin et al. “Effects of phenanthrene on chemical composition and enzyme activity in fresh tea leaves.” __Food Chemistry__. 115(2009): 569-573.

Scientists at the University of South Carolina were developing molecules to inhibit the activity of the lysosomal enzyme acid ceramidase (ACDase). The enzyme is responsible for converting ceramide, a cell growth modulator, to sphingosine 1-phosphate (S1P), an anti-apoptotic tumor protective agent**.** These scientists were trying to design/synthesize inhibitors of ACDase so as to induce apoptosis in cancerous cells. It was known that B13 molecules had a high inhibitory effect on ACDase in vitro, but not in vivo. These scientists then synthesized an aromatic analog of B13 which they called LCL204. LCL204 inhibited ACDase, but also induced lysosomal destabilization and proteolytic degradation of the lysosome. From the two extremes of B13 and LCL204, the scientists hybridized the two molecules in various ways, and measured the efficacy of the newly synthesized molecules. They determined LCL464 to be the most effective, because it inhibited ACDase in vitro and in vivo, but did not cause lysosomal dysfunction, nor degradation of ACDase. The implications of LCL464 are its use in chemotherapeutic drugs for site-specific ACDase inhibition.

Bai, Aiping et al. “Synthesis and bioevaluation of ω-//N//-amino analogs of B13.” __Bioorganic and Medicinal Chemistry.__ 17(2009): 1840-1848.