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BP: Fachverband Biologische Physik
BP 33: Biological Machines \& Motor Proteins
BP 33.9: Vortrag
Freitag, 18. März 2011, 12:45–13:00, ZEU 250
The molecular basis of filopodial retraction analyzed with photonic force based microscopy — •Felix Kohler1,2 and Alexander Rohrbach1,2 — 1Bio and Nano-photonics, IMTEK, University of Freiburg, Germany — 2BIOSS Centre for Biological Signalling Studies, Freiburg, Germany
Filopodia are needle-like protrusions of the cell surface. These actin rich protrusions are highly dynamic structures that extend and retract over the timescale of a few seconds. Besides actin polymerization and depolymerization, coordinated transport of molecular motors seems to control filopodial mechanics. Apart from sensing the environment and anchorage of cells to a substratum filopodia are also involved in phagocytosis. We use photonic force microscopy to investigate the mechanical concepts of the filopodial retraction during phagocytosis. The motion of an optically trapped bead is attached to tip of a filopodium and tracked interferometrically in 3D with nanometer precision at a microsecond timescale. The measurement of e.g. the beads mean displacement allows determining the retraction forces of filopodia at various retraction speeds. We have measured F-actin dependent steps inside living cells during filopodial retraction likely belonging to actin-based molecular motors [1]. Steps remain clearly visible even at force regimes clearly beyond the stall force of a single myosin motor. This indicates a kind of inter-motor coupling, a phenomenon which will be presented in this talk and which we try to explain by a stochastic multi-state model.
[1] Kress, H. et al., pnas, 104, 2007, 11633-11638