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Accueil du site > Recrutement > Stages M2 / Thèses au LPT > Biophysical exploration of nanoscale dynamics at the immunological synapse

Biophysical exploration of nanoscale dynamics at the immunological synapse

Ph.D. proposal at the interface biology/statistical mechanics

par Nicolas Destainville - 19 mars

Ph.D. 2019-2022 funded by the Université Fédérale de Toulouse

Centre de Physiopathologie de Toulouse-Purpan (CPTP, UMR 1043 Inserm/UPS/CNRS)
and Laboratoire de Physique Théorique (LPT-IRSAMC, UMR 5151 UPS/CNRS)

“NanoTCell” is an interdisciplinary project at the interface between quantitative biology and statistical biophysics aiming at elucidating how T lymphocytes (a.k.a. T cells) regulate their cytotoxic activity, a key parameter conditioning the capability of the immune system to eliminate infected or cancer cells. It depends on the assembly of the immunological synapse, a highly dynamic structure that stabilizes the interaction between the T cell and its target cell, leads to the T cell activation, allows the secretion of lytic granules and potentiates the pore-forming activity of perforin by applying mechanical forces on the target cell plasma membrane.

The synaptic cortical actin cytoskeleton is essential in this context as it has been proven to be a key-player of the synapse assembly and its integrity is essential for the cytotoxic activity. Exploring its organization, the molecular control of its remodeling and the ensuing physical forces will be crucial in order to understand how T cells convert molecular signals into a coordinated physical action. The NanoTCell project relies on the study of unique study models consisting in T cells from immunodeficient patients carrying mutations in genes encoding various actin cytoskeleton regulators (WASP, WIP, WRD1, Coronin-1A).

The main objectives of the thesis will be to :
-  Characterize by superresolution microscopy (SIM) and dynamical microscopy (TIRF) the synapse spatial organization in T cells from immunodeficient patients and healthy donors, with a focus on the correlation between cortical actin density and the localization of membrane proteins ;
-  Test the relevance of different physical models used to describe membrane protein organization in nanodomains (fence-and-picket model vs models based on protein-protein and/or protein-lipid interactions) ;
-  Measure the physical forces exerted by the T cell at the synapse in the cytotoxic activity context with the help of micro-pillar experiments [Basu2016] ;
-  Elaborate a quantitative numerical multiscale model of immunological synapse describing how actin cytoskeleton remodeling controls lytic granules release and cytotoxic activity.

The experimental work (microscopy) will be done under the supervision of Loic Dupré, an immunologist expert in the study of primary immunodeficiencies related to the actin cytoskeleton, at the CPTP (cell imaging facility, directed by Sophie Allart, Genotoul network) [Dupré2002, Calvez2011, Dupré2015, Pfajfer2017, Houmadi2018, Pfajfer2018]. The numerical modeling will be done under the supervision of Nicolas Destainville (LPT), a physicist expert in data analysis and modeling of biophysical mechanisms at play at the cell surface [Destainville2016, Gueguen2017, Destainville2018]. The student will share its time equally between both laboratories. The part of the work related to the measurement of physical forces will be done during a stay in Morgan Huse’s team at the Memorial Sloan-Kettering Cancer Center, New York, USA.

References

[Basu2016] R. Basu, ..., M. Huse, Cytotoxic T cells use mechanical force to potentiate target cell killing, Cell 165, 100 (2016).

[Calvez2011] R. Calvez, ..., L. Dupré, The Wiskott-Aldrich syndrome protein permits the assembly of a focused immunological synapse enabling sustained TCR signaling, Haematologica 96, 1415 (2011).

[Destainville2016] N. Destainville, T.H. Schmidt, T. Lang, Where biology meets physics – a converging view on membrane microdomain dynamics, Current Topics in Membranes 77, 27 (2016).

[Destainville2018] N. Destainville, M. Manghi, J. Cornet, A rationale for mesoscopic domain formation in biomembranes, Biomolecules 8, 104 (2018).

[Dupré2002] L. Dupré, et al., Wiskott-Aldrich syndrome protein regulates lipid raft dynamics during immunological synapse formation, Immunity 17, 157 (2002). [Dupré2015] L. Dupré, R. Houmadi, C. Tang, J. Rey-Barroso, T lymphocyte migration : an action movie starring the actin and associated actors, Front. Immunol. 6, 586 (2015).

[Gueguen2017] G. Gueguen, N. Destainville, M. Manghi, Fluctuation tension and shape transition of vesicles : renormalisation calculations and Monte Carlo simulations, Soft Matter 13, 6100 (2017).

[Houmadi2017] R. Houmadi, Organisation spatiale de LFA-1 à la synapse immunologique des lymphocytes T cytotoxiques : approches de microscopie de super-résolution, Thèse de doctorat, Université Toulouse III, 2017.

[Houmadi2018] R. Houmadi, D. Guipouy, ..., N. Destainville, S. Valitutti, S. Allart, L. Dupré, The Wiskott-Aldrich syndrome protein contributes to the assembly of the LFA-1 nanocluster belt at the lytic synapse, Cell Rep. 22, 979 (2018).

[Pfajfer2017] L. Pfajfer, ..., L. Dupré, WIP deficiency severely affects human lymphocyte architecture during migration and synapse assembly, Blood 17, 1949 (2017).

[Pfajfer2018] L. Pfajfer, ..., L. Dupré, K. Boztug, Mutations affecting the actin regulator WDR1 lead to aberrant lymphoid immunity, J. Allergy Clin. Immunol. 142, 1589 (2018).