Dresden 2020 – scientific programme

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BP: Fachverband Biologische Physik

BP 25: Cell Mechanics II

BP 25.8: Talk

Wednesday, March 18, 2020, 17:00–17:15, HÜL 386

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 T-cell has identified a target cell, they form a tight contact zone, the immunological synapse (IS). One then observes a re-polarization of the cell involving the rotation of the microtubule (MT) half-spindle and a movement of the microtubule organizing center (MTOC) to the IS. Concomitantly a massive relocation of organelles attached to MTs is observed. Since the mechanism of this relocation remains elusive we devise a theoretical model for the molecular motor driven motion of the MT half-spindle confined between membrane and nucleus. We analyze different currently discussed scenarios, the cortical sliding and the capture-shrinkage mechanisms, and compare quantitative predictions about the spatio-temporal evolution of MTOC position and spindle morphology with experiments. Model predicts the experimentally observed biphasic nature of the repositioning and confirms the dominance of the capture-shrinkage over the cortical sliding mechanism when MTOC and IS are initially diametrically opposed. We find that the two mechanisms act synergetically reducing the resources necessary for repositioning. Localization of dyneins in the pSMAC facilitates their interaction with MTs. Model opens a way to infer details of the dynein distribution from the experimentally observed features of the MT half-spindle dynamics.