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Impact d'une perturbation mécanique ou photo-chimique sur le trafic intracellulaire

Abstract : The cell cytoplasm is crowded with membrane-delimited compartments, permanently communicating with each other. Such communication is permitted by active transport, also called intracellular trafficking, of vesicles along the cytoskeleton (actin filaments, microtubules), and mediated by molecular motors. In order to perturbate this intracellular trafficking, two different ways to apply controlled physical stresses have been performed. The first perturbation is a mechanical one : we used magnetic endosomes to probe and stress the cell body. To obtain them we internalized magnetic nanoparticles into mesenchymal stem cells (MSC) through the natural endocytosis pathway. These endosomes align into chains in the presence of a magnetic field. The mechanical perturbation then consists in applying a rotational magnetic field on these chains. When comparing the activity before and after a shear stress, we observed a decrease in the intracellular activity. The second perturbation has a photochemical origin, through the excitation of an internalized photosensitizer molecule (m-THPC or TPCS2a). By combining measurements of local cytoplasmic viscosity and intracellular activity, we found that photo-activation induced only a slight increase in viscosity while a massive slowing down of trafficking was observed. These effects are correlated with depolymerization of the microtubule network. The experiments demonstrate that these two photochemical agents have different intracellular impacts. Eventually, we studied a second effect of the photochemical perturbation which is the massive and rapid emission of extracellular vesicles.
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Kelly Aubertin. Impact d'une perturbation mécanique ou photo-chimique sur le trafic intracellulaire. Biophysique [physics.bio-ph]. Université paris Diderot, 2014. Français. ⟨tel-01611470⟩

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