Novel indolylmaleimide acts as GSK-3β inhibitor in human neural progenitor cells

The Wnt pathway is involved in cellular processes linked to either proliferation or differentiation. Therefore small molecules offer an attractive opportunity to modulate this pathway, whereas the key enzyme GSK-3β is of special interest. In this study, non-symmetrically substituted indolylmaleimides have been synthesized and their ability to function as GSK-3β inhibitors has been investigated in a human neural progenitor cell line. Among the newly synthesized compounds, the substance IM-12 showed a significant activity in several biological tests which was comparable or even outplayed the effects of the known GSK-3β inhibitor SB-216763. Furthermore the treatment of human neural progenitor cells with IM-12 resulted in an increase of neuronal cells. Therefore we conclude that indolylmaleimides act via the canonical Wnt signalling pathway by inhibition of the key enzyme GSK-3β.     

Endolithic chlorophyll d-containing phototrophs

Cyanobacteria in the genus Acaryochloris are the only known oxyphototrophs that have exchanged chlorophyll a (Chl a) with Chl d as their primary photopigment, facilitating oxygenic photosynthesis with near infrared (NIR) light. Yet their ecology and natural habitats are largely unknown. We used hyperspectral and variable chlorophyll fluorescence imaging, scanning electron microscopy, photopigment analysis and DNA sequencing to show that Acaryochloris-like cyanobacteria thrive underneath crustose coralline algae in a widespread endolithic habitat on coral reefs. This finding suggests an important role of Chl d-containing cyanobacteria in a range of hitherto unexplored endolithic habitats, where NIR light-driven oxygenic photosynthesis may be significant.     

Biomass productivity and productivity of fatty acids and amino acids of microalgae strains as key characteristics of suitability for biodiesel production

Microalgae are discussed as an alternative source for the production of biofuels. The lipid content compared to cultivation time of used species is the main reason for any choice of a special strain. This paper reviews more analytical data of 38 screened microalgae strains. After the cultivation period, total content of lipids was analysed. The extracted fatty acids were quantified as fatty acid methyl esters by GC analysis. The amino acids were analysed by HPLC. Chlorella sp., Chlorella saccharophila, Chlorella minutissima and Chlorella vulgaris were identified as species with the highest productivity of fatty acids relevant to transesterification reactions. The components were mainly linoleic acid, palmitic acid and oleic acid. To increase productivity of highly saturated fatty acids, cultivation parameters light intensity and temperature were varied. In this manner, the ideal conditions for biodiesel production were defined in this publication.     

Localization of urokinase-type plasminogen activator receptor on U937 cells: Phorbol ester PMA induces heterogeneity

The binding of human urokinase-type plasminogen activator (u-PA) to the surface of the human monocytic cell line U937 was studied by immunological detection of bound u-PA or binding of biotinylated diisopropyl fluorophosphate-inactivated human u-PA visualized by light or electron microscopy. Untreated U937 cells showed a characteristic binding pattern, with the majority of the u-PA bound to the microvillar-containing protruding pole of the cells. After treatment with the phorbol ester PMA, the resulting adherent cell population was very heterogeneous with respect to both cellular morphology and u-PA binding. The bound u-PA was distributed on both the dorsal and the substrate side of the cells, and the patches of bound u-PA could not be correlated to any typical membrane conformations or cell-cell or cell-substratum contacts. When a monoclonal antibody directed against the amino-terminal fragment (ATF) of u-PA was used, the results were identical regardless of whether intact u-PA or ATF was used for binding to the cells. In contrast, when a monoclonal antibody recognizing the non-receptor-binding protease domain of u-PA was used, bound ATF showed no staining, while bound intact u-PA was stained as efficiently as above. The alteration of u-PA receptor distribution following treatment with PMA could be related to the changes in glycosylation and ligand affinity of the purified u-PA receptor previously described following PMA treatment of U937 cells.     

The ligand-binding domain of the cell surface receptor for urokinase-type plasminogen activator.

The purified urokinase plasminogen activator receptor (u-PAR) was cleaved into two fragments by mild chymotrypsin treatment. The smaller fragment (apparent Mr 16,000) possessed the ligand-binding capability, as shown by chemical cross-linking analysis. This fragment constituted the NH2-terminal part of the intact receptor, probably including the whole sequence 1-87, and contained N-linked carbohydrate. After detergent phase separation in the Triton X-114 system, the fragment was present in the water phase where its binding activity could be demonstrated in the absence of the rest of the protein. An analysis of internal homology in the amino acid sequence of u-PAR revealed the presence of three repeats of approximately 90 residues each. The ligand-binding fragment corresponds to the first repeat, supporting that this unit is a structurally autonomous domain. Domains homologous with the internal repeats of u-PAR constitute the extracellular part of Ly-6 antigens and of the squid glycoprotein Sgp-2. Like u-PAR, these proteins are attached to the membrane by a glycosyl-phosphatidylinositol anchor. The hydrophilic, ligand-binding u-PAR domain identified in the present study has potential applications in interfering with cell-surface plasmin-mediated proteolysis.     

Antibody-mediated targeting of the urokinase-type plasminogen activator proteolytic function neutralizes fibrinolysis in vivo

Urokinase-type plasminogen activator (uPA) plays a central role in tissue remodeling processes. Most of our understanding of the role of uPA in vivo is derived from studies using gene-targeted uPA-deficient mice. To enable in vivo studies on the specific interference with uPA functionality in mouse models, we have now developed murine monoclonal antibodies (mAbs) directed against murine uPA by immunization of uPA-deficient mice with the recombinant protein. Guided by enzyme-linked immunosorbent assay, Western blotting, surface plasmon resonance, and enzyme kinetic analyses, we have selected two highly potent and inhibitory anti-uPA mAbs (mU1 and mU3). Both mAbs recognize epitopes located on the B-chain of uPA that encompasses the catalytic site. In enzyme activity assays in vitro, mU1 blocked uPA-catalyzed plasminogen activation as well as plasmin-mediated pro-uPA activation, whereas mU3 only was directed against the first of these reactions. We additionally provide evidence that mU1, but not mU3, successfully targets uPA-dependent processes in vivo. Hence, systemic administration of mU1 (i) rescued mice treated with a uPA-activable anthrax protoxin and (ii) impaired uPA-mediated hepatic fibrinolysis in tissue-type plasminogen activator (tPA)-deficient mice, resulting in a phenotype mimicking that of uPA;tPA double deficient mice. Importantly, this is the first report demonstrating specific antagonist-directed targeting of mouse uPA at the enzyme activity level in a normal physiological process in vivo.     

Genome-wide scan on total serum IgE levels identifies FCER1A as novel susceptibility locus

High levels of serum IgE are considered markers of parasite and helminth exposure. In addition, they are associated with allergic disorders, play a key role in anti-tumoral defence, and are crucial mediators of autoimmune diseases. Total IgE is a strongly heritable trait. In a genome-wide association study (GWAS), we tested 353,569 SNPs for association with serum IgE levels in 1,530 individuals from the population-based KORA S3/F3 study. Replication was performed in four independent population-based study samples (total n = 9,769 individuals). Functional variants in the gene encoding the alpha chain of the high affinity receptor for IgE (FCER1A) on chromosome 1q23 (rs2251746 and rs2427837) were strongly associated with total IgE levels in all cohorts with P values of 1.85 x 10(-20) and 7.08 x 10(-19) in a combined analysis, and in a post-hoc analysis showed additional associations with allergic sensitization (P = 7.78 x 10(-4) and P = 1.95 x 10(-3)). The "top" SNP significantly influenced the cell surface expression of FCER1A on basophils, and genome-wide expression profiles indicated an interesting novel regulatory mechanism of FCER1A expression via GATA-2. Polymorphisms within the RAD50 gene on chromosome 5q31 were consistently associated with IgE levels (P values 6.28 x 10(-7)-4.46 x 10(-8)) and increased the risk for atopic eczema and asthma. Furthermore, STAT6 was confirmed as susceptibility locus modulating IgE levels. In this first GWAS on total IgE FCER1A was identified and replicated as new susceptibility locus at which common genetic variation influences serum IgE levels. In addition, variants within the RAD50 gene might represent additional factors within cytokine gene cluster on chromosome 5q31, emphasizing the need for further investigations in this intriguing region. Our data furthermore confirm association of STAT6 variation with serum IgE levels.     

The urokinase receptor (uPAR) and the uPAR-associated protein (uPARAP/Endo180): membrane proteins engaged in matrix turnover during tissue remodeling

The breakdown of the barriers formed by extracellular matrix proteins is a pre-requisite for all processes of tissue remodeling. Matrix degradation reactions take part in specific physiological events in the healthy organism but also represent a crucial step in cancer invasion. These degradation processes involve a highly organized interplay between proteases and their cellular binding sites as well as specific substrates and internalization receptors. This review article is focused on two components, the urokinase plasminogen activator receptor (uPAR) and the uPAR-associated protein (uPARAP, also designated Endo180), that are considered crucially engaged in matrix degradation. uPAR and uPARAP have highly diverse functions, but on certain cell types they interact with each other in a process that is still incompletely understood. uPAR is a glycosyl-phosphatidylinositol-anchored glycoprotein on the surface of various cell types that serves to bind the urokinase plasminogen activator and localize the activation reactions in the proteolytic cascade system of plasminogen activation. uPARAP is an integral membrane protein with a pronounced role in the internalization of collagen for intracellular degradation. Both receptors have additional functions that are currently being unraveled. The present discussion of uPAR and uPARAP is centered on their protein structure and molecular and cellular function.     

uPARAP/Endo180 is essential for cellular uptake of collagen and promotes fibroblast collagen adhesion

The uptake and lysosomal degradation of collagen by fibroblasts constitute a major pathway in the turnover of connective tissue. However, the molecular mechanisms governing this pathway are poorly understood. Here, we show that the urokinase plasminogen activator receptor-associated protein (uPARAP)/Endo180, a novel mesenchymally expressed member of the macrophage mannose receptor family of endocytic receptors, is a key player in this process. Fibroblasts from mice with a targeted deletion in the uPARAP/Endo180 gene displayed a near to complete abrogation of collagen endocytosis. Furthermore, these cells had diminished initial adhesion to a range of different collagens, as well as impaired migration on fibrillar collagen. These studies identify a central function of uPARAP/Endo180 in cellular collagen interactions.