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Motilité sous flux et étalement de Dictyostelium discoideum

Abstract : DICTYOSTELIUM DISCOIDEUM IS AN UNICELLULAR ORGANISM, WICH FEEDS BY MICROORGANISMS PHAGOCYTOSIS OR FLUID PHASE ENDOCYTOSIS. IT IS ABLE TO MIGRATE ON A SOLID SUBSTRATE, BY PROTRUDING THE LEADING EDGE AND RETRACTING THE REAR EDGE. CELL MOTILITY AND CELL SPREADING ARE CLEARLY LINKED, BECAUSE THE CELL HAS TO ADHERE ON A SUBSTRATE TO SENSE AND EXERT FORCES. UNDER SHEAR FLOW INDUCED MOTILITY, DICTYOSTELIUM CELLS MOVE IN THE DIRECTION OF THE FLOW. WE STUDIED BIOCHEMICAL MECANISMS IN RESPONSE TO SHEAR STRESS AND CELL SPREADING. FOR THAT WE ANALYZED WILD TYPE AND MUTANT CELLS, FIRST AT THE CELL RANGE AND THEN AT THE CELL EDGE RANGE. WE SHOWED SEVERAL RESULTS. EXTRACELLULAR FREE CALCIUM RAISES CELL SPEED AND CELL SENSITIVITY TO SHEAR STRESS. THIS IS DUE TO LARGER PROTRUSIONS AND MORE EFFICIENT RETRACTIONS. THE CELL EDGES ARE OSCILLATING, AT DIFFERENT PROPER FREQUENCIES. THESE FREQUENCIES DON'T DEPEND ON CALCIUM CONCENTRATION OR CELLULAR TYPE. CALCIUM RAISES KINETICS AND REGULARITY OF CELL SPREADING, ACTING ON ACTIN POLYMERISATION. CELL SPREADING ONLY DEPENDS ON ACTIN POLYMERISATION AND EMISSION OF PROTRUSIONS, WHILE THE CELL NEEDS MYOSIN 2 TO MAKE RETRACTIONS. FINALLY, HETEROTRIMERIC G PROTEINS AND IP3 RECEPTORS ARE INVOLVED IN CALCIUM SIGNALING.
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https://tel.archives-ouvertes.fr/tel-00009558
Contributor : Sébastien Fache <>
Submitted on : Tuesday, June 21, 2005 - 5:26:05 PM
Last modification on : Friday, November 6, 2020 - 3:57:15 AM
Long-term archiving on: : Friday, September 14, 2012 - 1:25:17 PM

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  • HAL Id : tel-00009558, version 1

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Sébastien Fache. Motilité sous flux et étalement de Dictyostelium discoideum. Biophysique [physics.bio-ph]. Université Joseph-Fourier - Grenoble I, 2005. Français. ⟨tel-00009558⟩

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