Regensburg 2019 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 14: Cell mechanics I

BP 14.2: Vortrag

Mittwoch, 3. April 2019, 09:45–10:00, H10

Repetitive failures and success in particle retraction of macrophage filopodia — •Rebecca Michiels and Alexander Rohrbach — Lab for Bio- and Nano-Photonics, University of Freiburg, Georges-Koehler-Allee 102, 79110 Freiburg, Germany

Macrophages take up pathogens like viruses and bacteria in a process called phagocytosis. On their surface, macrophages express abundant filopodia, thin, needle-like protrusions, which they use to catch and retract pathogens, which are later engulfed. We investigate the adaptive mechanics of filopodia and analyze the biophysical principles governing the attachment and retraction of particles. To this end, we use a Photonic Force Microscope in which we combine DIC microscopy, fluorescence microscopy, optical tweezers and interferometric particle tracking. Filopodia retractions are induced by presenting optically trapped polystyrene beads to macrophage cells. The information gained from interferometric particle tracking is used to analyze the stiffness of the bond between cell and bead, the viscosity of the surroundings, the velocity of the retraction and the force-dependence of all these parameters. It can be shown that the strength of the attachment between cell and bead evolves dynamically during pulling. The experiments are complemented by fluorescence microscopy with live cells with labeled actin cytoskeleton. The characteristics of the movement of the bead are compared with the dynamics of the underlying actin retrograde flow. The results indicate that the bead retraction is mediated by a force-dependent coupling to the actin cytoskeleton.