BPCPPDYSOE21 – scientific programme

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BP: Fachverband Biologische Physik

BP 4: Cell Mechanics II

BP 4.3: Talk

Monday, March 22, 2021, 11:40–12:00, BPa

Stochastic model of T Cell repolarization during target elimination — •Ivan Hornak and Heiko Rieger — Saarland University, Dep. Theoretical Physics, Center for Biophysics

Cytotoxic T lymphocytes (T) and natural killer cells are the main cytotoxic killer cells of the human body to eliminate pathogen-infected or tumorigenic cells (target cells). Once a T or NK cell has identified a target cell, they form a tight contact zone, the immunological synapse (IS). One then observes a rotation of the microtubule (MT) cytoskeleton and a movement of the microtubule organizing center (MTOC) to the center of the IS. Since the mechanism of this relocation remains elusive, we devise a theoretical model for the molecular motor driven motion of the MT cytoskeleton. We analyze the cortical sliding and the capture-shrinkage mechanisms currently discussed in the literature and compare quantitative predictions about the spatio-temporal evolution of the MTOC position and spindle morphology with experiments. The model predicts the experimentally observed biphasic nature of the repositioning process. We confirm that the capture-shrinkage mechanism is dominant over the cortical sliding mechanism when MTOC and IS are initially diametrically opposed and inferior to the cortical sliding in other configurations. We find that the two mechanisms act synergistically reducing the resources necessary for repositioning. When two IS are present, the MTOC undergoes irregular transitions between the two IS and we determine the dependency of the dwell times and transition frequency on the dynein density for both mechanisms.