E-Cadherin regulates neural stem cell self-renewal

E-Cadherin, a cell adhesion protein, has been shown to take part in the compartmentalization, proliferation, survival, and differentiation of cells. E-Cadherin is expressed in the adult and embryonic forebrain germinal zones in vivo, and in clonal colonies of cells derived from these regions and grown in vitro. Mice carrying E-Cadherin floxed genes crossed to mice expressing Cre under the Nestin promoter demonstrate defects in the self-renewal of neural stem cells both in vivo and in vitro. The functional role of E-Cadherin is further demonstrated using adhesion-blocking antibodies in vitro, which specifically target cadherin extracellular adhesive domains. Adult neural stem cell colonies decrease in the presence of E-Cadherin antibodies in a dosage-dependent manner, in contrast to P-Cadherin antibody. On overexpression of normal E-Cadherin and a mutated E-Cadherin, containing no intracellular binding domain, an increased number of clonal adult neural stem cell colonies are observed. These data suggest it is specifically E-Cadherin adhesion that is responsible for these self-renewal effects. These data show the importance of E-Cadherin in the neural stem cell niche and suggest E-Cadherin regulates the number of these cells

Structural features of apramycin bound at the bacterial ribosome a site as detected by NMR and CD spectroscopy

The interaction of apramycin with an RNA fragment mimicking the bacterial ribosomal A site was investigated by NMR spectroscopy, mainly by using the transferred NOE technique. The fact that only the RNA-bound antibiotic shows nonzero NOE effects, allowed us to gain structural details of bound apramycin despite the fast exchange conditions between the free and RNA-bound forms. The dissociation constant of the apramycin–RNA complex was evaluated by CD spectroscopy

Effect of Cu(II) on the complex between kanamycin A and the bacterial ribosomal A site.

The solution structure of kanamycin A interacting with a ribosomal A-site fragment was solved by transferred-NOE techniques and found to agree with the structure of the complex observed in the crystal. Despite the fast exchange conditions found for the interaction, the bound form was identified by NOESY spectroscopy. At 600 MHz, NOE effects are only observed for the RNA-associated antibiotic. Dissociation constants were measured by NMR spectroscopy for two sites of interaction (K-d1 = 150 +/- 40 mu M; K-d2 = 360 +/- 50 mu M). Furthermore, the effects of the Cu-II ion on the antibiotic, on the RNA fragment that mimics the bacterial ribosomal A site, and on the complex formed between these two entities were analyzed. The study led to the proposal of a model that localizes the copper ion within the kanamycin-RNA complex

IQGAP1 protein specifies amplifying cancer cells in glioblastoma multiforme.

International audienceThe accurate identification and thorough characterization of tumorigenic cells in glioblastomas are essential to enhance our understanding of their malignant behavior and for the design of strategies that target this important cell population. We report here that, in rat brain, the scaffolding protein IQGAP1 is a marker of brain nestin+ amplifying neural progenitor cells. In a rat model of glioma, IQGAP1 also characterizes a subpopulation of nestin+ amplifying tumor cells in glioblastoma-like tumors but not in tumors with oligodendroglioma features. We next confirmed that IQGAP1 represents a new marker that may help to discriminate human glioblastoma from oligodendrogliomas. In human glioblastoma exclusively, IQGAP1 specifies a subpopulation of amplifying nestin+ cancer cells. Neoplastic IQGAP1+ cells from glioblastoma can be expanded in culture and possess all the characteristics of cancer stem-like progenitors. The similarities between amplifying neural progenitors and glioblastoma amplifying cancer cells may have significant implications for understanding the biology of glioblastoma

Coordination pattern, solution structure and DNA damage studies of the copper(II) complex with the unusual aminoglycoside antibiotic hygromycin B

The aminoglycosidic antibiotic hygromycin B presents a peculiar chemical structure, characterized by two sugar rings joined via a spiro connection. The Cu(II) complex of hygromycin B in water solution was characterized by 1H-NMR, UV-Vis, EPR and CD spectroscopy, combined with potentiometric measurements. The spin–lattice relaxation enhancements were interpreted by the Solomon-Bloembergen-Morgan theory, allowing us to calculate copper-proton distances that were used to build a model of the complex by molecular mechanics and dynamics calculations. The fidelity of the proposed molecular model was checked by ROESY maps. Moreover DNA damage by the Cu(II)-hygromycin B system was also investigated, showing single and double strand scissions exerted by the complex at concentrations in the range 1–5 mM. Addition of either hydrogen peroxide or ascorbic acid to each sample resulted in the shift of the cleavage potency towards lower concentrations of the complex

Structural features and oxydative stress towards plasmid DNA of apramycin copper complex

The interaction of apramycin with copper at different pH values was investigated by potentiometric titrations and EPR, UV-vis and CD spectroscopic techniques. The Cu(II)-apramycin complex prevailing at pH 6.5 was further characterized by NMR spectroscopy. Metal-proton distances derived from paramagnetic relaxation enhancements were used as restraints in a conformational search procedure in order to define the structure of the complex. Longitudinal relaxation rates were measured with the IR-COSY pulse sequence, thus solving the problems due to signal overlap. At pH 6.5 apramycin binds copper(II) with a 2 : 1 stoichiometry, through the vicinal hydroxyl and deprotonated amino groups of ring III. Plasmid DNA electrophoresis showed that the Cu(II)-apramycin complex is more active than free Cu(II) in generating strand breakages. Interestingly, this complex in the presence of ascorbic acid damages DNA with a higher yield than in the presence of H2O2