Ganglioside GM3 inhibition of EGF receptor mediated signal transduction

Ganglioside GM3 is a membrane component that has been describedto modulate cell growth through inhibition of EGF receptor associatedtyrosine kinase. In order to determine if the inhibition ofcell growth by this ganglioside is specifically mediated throughEGF receptor signaling, the effects of GM3 on key enzymes implicatedin EGF signaling were determined and compared to another inhibitorof the EGF receptor kinase. Treatment of A1S cells in cultureby GM3 or a tyrosine kinase inhibitor, leflunomide, led to theinhibition of MAP kinase and PI3 kinase activities. There wasno detectable effect on phosphotyrosine phosphatases. In a cellfree system, however, GM3 had no effect on the activity of thesesignaling intermediates. Leflunomide was able to directly inhibitMAP kinase activity. GM3 and leflunomide were also found toact differently on the expression of the early immediate genes.The expression of c-fos and c-jun was inhibited by both GM3and leflunomide. The expression of c-myc, however, was onlyinhibited by leflunomide. These findings suggest that the actionof GM3 on cell growth and signaling is specifically mediatedby EGF receptor and that this ganglioside does not act directlyon the intracellular intermediates of EGF receptor signaling.In addition, soluble small molecule tyrosine kinase inhibitorssuch as leflunomide can directly affect the activity of MAPkinases and possibly other signaling intermediates. The directeffects of leflunomide on signaling intermediates may explainthe differential effects of leflunomide and GM3 on gene expressionand cell growth. cell growth epidermal growth factor gangliosides GM3 signal transduction     

An Assembly Intermediate Structure of Rice Dwarf Virus Reveals a Hierarchical Outer Capsid Shell Assembly Mechanism

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Synuclein proteins of the pufferfish Fugu rubripes: sequences and functional characterization

In humans, three genes encode the related alpha-, beta-, and gamma-synucleins, which function as lipid-binding proteins in vitro. They are being widely studied, mainly because of the central involvement of alpha-synuclein in a number of neurodegenerative diseases, including Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy. In these diseases, the normally soluble alpha-synuclein assembles into abnormal filaments. Here, we have identified and characterized the synuclein gene family from the pufferfish Fugu rubripes. It consists of four genes, which encode alpha-, beta-, gamma1-, and gamma2-synucleins. They range from 113 to 127 amino acids in length and share many of the characteristics of human synucleins, including the presence of imperfect amino-terminal repeats of 11 amino acids, a hydrophobic middle region, and a negatively charged carboxy-terminus. All four synucleins are expressed in the Fugu brain. Recombinant Fugu synucleins exhibited differential liposome binding, which was strongest for alpha-synuclein, followed by beta-, gamma2-, and gamma1-synucleins. In assembly experiments, Fugu alpha-, gamma1-, and gamma2-synucleins formed filaments more readily than human alpha-synuclein. Fugu beta-synuclein, by contrast, failed to assemble in bulk. Filament assembly of synucleins was directly proportional to their degree of hydrophobicity and their tendency to form beta-sheet structure, and correlated inversely with their net charge.     

Acarbose, an alpha-glucosidase inhibitor, improves endothelial dysfunction in Goto-Kakizaki rats exhibiting repetitive blood glucose fluctuation

Several epidemiological studies have revealed that subjects with postprandial hyperglycemia are at increased risk of cardiovascular disease. However, the impact of postprandial hyperglycemia and its treatment on endothelial function has not been clarified yet. In this study, Goto-Kakizaki (GK) rats, a non-obese type 2 diabetes model, fed twice daily were used as a model of repetitive postprandial glucose spikes. We investigated the endothelial function in these rats treated or untreated with acarbose, an alpha-glucosidase inhibitor. Administration of acarbose for 12 weeks markedly improved postprandial hyperglycemia, postprandial insulin level, total cholesterol, triglyceride, and free fatty acid level in GK rats. Furthermore, acarbose efficiently reduced the number of monocytes adherent to aortic endothelial layer, improved acetylcholine-dependent vasodilatation, and reduced intimal thickening of the aorta. While it is generally regarded that repetitive postprandial hyperglycemia is associated with the onset of cardiovascular diseases, our data demonstrated that acarbose treatment efficiently ameliorated endothelial dysfunction and reduced intimal thickening, thus adding support to the protective effect of acarbose against the onset of cardiovascular disease.     

Sulfatide and its synthetic analogues recognition by Moraxella catarrhalis

Moraxella catarrhalis is one of the major pathogens of respiratory and middle ear infections. Attachment of this bacterium to the surface of human pharyngeal epithelial cells is the first step in the pathogenesis of infections. This study revealed that sulfatide might act as a binding molecule for the attachment of M. catarrhalis to human pharyngeal epithelial cells. Furthermore, six different synthetic sulfatides were found to inhibit the attachment of M. catarrhalis significantly at an optimum concentration of 10 microg/ml. Synthetic sulfatides may have the potential to be used as a therapy to prevent M. catarrhalis infections.     

Genetics of symbiosis in Lotus japonicus: recombinant inbred lines, comparative genetic maps, and map position of 35 symbiotic loci

Development of molecular tools for the analysis of the plant genetic contribution to rhizobial and mycorrhizal symbiosis has provided major advances in our understanding of plant-microbe interactions, and several key symbiotic genes have been identified and characterized. In order to increase the efficiency of genetic analysis in the model legume Lotus japonicus, we present here a selection of improved genetic tools. The two genetic linkage maps previously developed from an interspecific cross between L. japonicus Gifu and L. filicaulis, and an intraspecific cross between the two ecotypes L. japonicus Gifu and L. japonicus MG-20, were aligned through a set of anchor markers. Regions of linkage groups, where genetic resolution is obtained preferentially using one or the other parental combination, are highlighted. Additional genetic resolution and stabilized mapping populations were obtained in recombinant inbred lines derived by a single seed descent from the two populations. For faster mapping of new loci, a selection of reliable markers spread over the chromosome arms provides a common framework for more efficient identification of new alleles and new symbiotic loci among uncharacterized mutant lines. Combining resources from the Lotus community, map positions of a large collection of symbiotic loci are provided together with alleles and closely linked molecular markers. Altogether, this establishes a common genetic resource for Lotus spp. A web-based version will enable this resource to be curated and updated regularly.     

Transgenic tobacco plants producing caffeine: a potential new strategy for insect pest control

Caffeine (1,3,7–trimethylxanthine) is one of the most widely used plant secondary metabolites, primarily as a stimulant and an ingredient in drugs. In nature, caffeine is believed to function in chemical defense, acting as an antiherbivory and allelopathic agent, and therefore it might be employed to protect agriculturally important crop plants. In coffee plants, caffeine is synthesized from the precursor xanthosine in four steps, three N-methylations and removal of ribose. We had previously isolated genes encoding three distinct N-methyltransferases, and we demonstrated production of recombinant enzymes that yielded caffeine in in vitro reconstitution experiments. When these caffeine biosynthetic pathway genes were simultaneously expressed in tobacco plants (Nicotiana tabacum), caffeine was successfully produced up to 5 μg/g fresh weight in leaves. The leaves were unpalatable to tobacco cutworms (Spodoptera litura). This repellent action appeared to be more widely␣applicable to lepidopteran caterpillars as observed with small white (Pieris rapae) fed on Chinese cabbages that had been top-treated with caffeine. Our recent results suggest a novel approach to strengthen anti-herbivore traits by producing caffeine in crop plants.