Berlin 2015 – scientific programme

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BP: Fachverband Biologische Physik

BP 16: Posters: Cell adhesion, mechanics and migration

BP 16.27: Poster

Monday, March 16, 2015, 17:30–19:30, Poster A

Cellular mechanics at the onset of phagocytosis — •Konrad Berghoff, Steve Keller, and Holger Kress — Department of Physics, University of Bayreuth, Universitätsstr. 30, 95447 Bayreuth

The phagocytic internalization and digestion of external objects by macrophages belongs to the most fundamental processes of the mammalian immune system. Phagocytosis can be induced by antibody recognition mediated by Fc receptors. Fc receptors give rise to intracellular signaling cascades which finally lead to particle uptake. The onset of particle uptake can be explained by a zipper-like mechanism consistent of a successive increase of receptor-ligand bonds at adjacent binding sites and subsequent membrane protrusion around the target object. The mechanics of this zipper-like interaction are not yet fully understood. We are therefore studying these mechanics on living cells. We hypothesize that the increasing number of ligand-receptor bonds during uptake leads to a temporally increasing rupture force necessary to break the bond between bead and cell. We also hypothesize that increasing local actin accumulation during the uptake results in local stiffening of the cellular uptake region. Using optical trapping in combination with high-speed image acquisition we test these hypotheses by inducing targeted single cell-particle binding between immunoglobulin-G coupled microbeads and J774 macrophages and by monitoring the cellular response when put under mechanical load. Our findings will give new insights on the mechanics of phagocytic uptake and will help to understand the role of zipper-like cell-membrane interactions and actin accumulation at the onset of phagocytosis.