Penetration into Cancer Cells via Clathrin-Dependent Mechanism Allows L-Asparaginase from Rhodospirillum rubrum to Inhibit Telomerase

The anticancer effect of L-asparaginases (L-ASNases) is attributable to their ability to hydrolyze L-asparagine in the bloodstream and cancer cell microenvironment. Rhodospirillum rubrum (RrA) has dual mechanism of action and plays a role in the suppression of telomerase activity. The aim of this work was to investigate the possible mechanism of RrA penetration into human cancer cells. Labeling of widely used L-ASNases by fluorescein isothiocyanate followed by flow cytometry and fluorescent microscopy demonstrated that only RrA can interact with cell membranes. The screening of inhibitors of receptor-mediated endocytosis demonstrated the involvement of clathrin receptors in RrA penetration into cells. Confocal microscopy confirmed the cytoplasmic and nuclear localization of RrA in human breast cancer SKBR3 cells. Two predicted nuclear localization motifs allow RrA to penetrate into the cell nucleus and inhibit telomerase. Chromatin relaxation promoted by different agents can increase the ability of RrA to suppress the expression of telomerase main catalytic subunit. Our study demonstrated for the first time the ability of RrA to penetrate into human cancer cells and the involvement of clathrin receptors in this process

Effect of Aluminum Ion Irradiation on Chemical and Phase Composition of Surface Layers of Rolled AISI 321 Stainless Steel

Commercial rolled AISI 321 stainless steel samples were irradiated with Al+ ions with an energy of 80 keV and fluence of 1017 ion/cm2. The effect of Al implantation on the chemical and phase composition of the steel surface layer was studied by X-ray electron spectroscopy and grazing beam mode of X-ray diffraction analysis. A thin surface layer down to a depth of 30 nm after Al+ ions implantation consists mainly of metal oxides. In the near-surface layers of 5 nm in depth, a noticeable depletion in chromium and nickel was observed. A surface layer (up to 0.5 µm) of non-irradiated steel, in addition to the f.c.c. austenite γ-phase, consists of up to 20 vol% of the b.c.c. α′-phase, which formed at rolling as a result of mechanical deformation. Al implantation results in the significant increase in the α′-phase amount in the surface layer at a depth up to 2 µm. It is indicated that the observed γ → α′ transformation at ion irradiation proceeds predominantly as a result of the effect of post-cascade shock waves, but not as a result of the surface layer chemical composition changes

Abstracts Of The Proceedings And The Posters From The Third Scientific Session Of The Medical College Of Varna

October 2-3, 201