Regensburg 2016 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 37: Cell Mechanics and Migration

BP 37.4: Vortrag

Mittwoch, 9. März 2016, 10:30–10:45, H44

Using photonic force microscopy to investigate filopodia mediated phagocytosis — •Rebecca Michiels and Alexander Rohrbach — Lab for Bio- and Nano-Photonics, University of Freiburg, Georges-Koehler-Allee 102, 79110 Freiburg, Germany

Macrophage cells are immune cells which internalize and digest foreign matter, cell debris and bacteria in the body. This process is called phagocytosis and is often initiated by filopodia which pull particles to the cell body where they are taken up by reorganization of the membrane. Filopodia contain tight bundles of filamentous actin that protrude from the actin cortex and are connected with the cell membrane via linker molecules. Retraction towards the cell body is driven by molecular motors which work in ensembles. The underlying physical principles that allow macrophages to tune their actions during phagocytosis are only little understood. We use a Photonic Force Microscope in which we combine DIC microscopy with optical tweezers and interferometric particle tracking. Polystyrene beads are held in an optical trap to enable controlled placement in the vicinity of the cells. The motion of the bead in the trap can be tracked in 3D with nanometer precision at a microsecond timescale using back focal plane interferometry. By changing the optical forces spatially or temporally, we investigate how the cell reacts to external forces and which mechanisms determine success or failure when attempting to bind and digest particles. We present novel experiments, which reveal binding, pulling and unbinding events of macrophage filopodia on a molecular scale.