Regensburg 2019 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 6: Poster I

BP 6.41: Poster

Montag, 1. April 2019, 17:30–19:30, Poster B2

Probing cellular resolution limits during phagocytosis — •Manuel Eisentraut, Adal Sabri, and Holger Kress — Biological Physics Group, Department of Physics, University of Bayreuth, Germany

Phagocytosis can be initiated by the binding of an immunoglobulin G (IgG)-opsonized particle to Fcγ-receptors in the cell membrane. While the molecular components of the underlying signaling cascades are well known, it is unclear how fast and how far the corresponding signals propagate in the cell. To address these issues, we investigate the spatial spreading of phagocytic signaling by measuring how well cells can resolve whether one or two particles are attached to the cell membrane. In our experiments, we attach pairs of polystyrene beads opsonized with IgG to single macrophages. The use of holographic optical tweezers allows us to precisely control the bead-to-bead distance during the attachment. The subsequent uptake into one joint or in two separate phagosomes is distinguished by analyzing the intracellular particle trajectories after the uptake.

For medium-sized phagosomes with a diameter of two micrometers, we found that the probability for joint uptake is very high for small distances and very low for large distances, with a transition between these regimes at distances of several hundreds of nanometers. Further studies with larger and smaller target beads will allow us to determine whether this resolution limit is constant or whether it scales with the target size, which will provide quantitative insights into the spatial spreading of signaling during phagocytosis.