"Spatiotemporal and mechanical control of cell motility and cell shape"
Le 12 juin 2014
Cell spreading and migration are motile processes regulated by the coordination of specialized dynamic structures, adhesion sites to the extracellular matrix (ECM) and membrane protrusions such as filopodia and lamellipodia. Formation of these structures is controlled by the dynamics of the actin cytoskeleton. Actin polymerization and movements generate the pushing and pulling forces triggering membrane protrusions and the formation of adhesion sites. During adhesion sites formation, integrins initiate molecular complexes thus creating a link between the ECM components and cytoskeletal proteins. Coupling of integrins to the actin cytoskeleton through scaffolding proteins enables the generation of traction forces on adhesion molecules. Reciprocally, connection of the actin cytoskeleton to immobilized adhesion proteins allows pushing forces arising from actin polymerization to drive forward membrane protrusions. The generation of these forces triggers translocation of the cell body. However, the disassembly of mature adhesion sites at the cell rear is required for translocation of the cell body and allows the recycling of the all the molecular components to the migration front.
Cell migration involves local signals both soluble and immobilized, intra-and extracellular. These signals induce the local assembly or disassembly of macromolecular complexes composed of structural and signaling proteins that regulate the formation and disruption of adhesives and protrusive structures. The work I have done during my PhD and during my post-doctoral studies is an analysis of some local phenomena during different stages of the cell migration cycle.
During my PhD I established how intracellular calcium oscillations drive motility at the sub-cellular level. I demonstrated that local increases in calcium trigger the disassembly of adhesion sites. During my first years of post-doc in M. Sheetz laboratory I demonstrated that the force-sensing mechanism of integrin is built on talin and triggers adhesion site initiation. Talin is a critical linker of integrin to actin, we performed pioneer single protein force measurements in cells and demonstrated the existence of a slipping bound between talin and actin. Then, from the observation that repetitive rows of adhesion sites form during cell motility, I demonstrated that cell edge protrusion is cyclic. The current dogma was that cell edge protrusion driven by actin polymerization was continuous. Later, I demonstrated that this periodicity results from the spatial, temporal and mechanical coordination of lamellipodial actin, myosin motors and adhesion site formation.
To step towards more spatial and temporal resolution, from the micron-scale coordination of sub-cellular structures to the nanometer-scale coordination of proteins, I decided to join the group of Daniel Choquet in France (CR2 CNRS, recruitment 2005). His team had made important contributions to understand synaptic plasticity, notably using high resolution tracking of receptor movements by single molecule imaging. Not only, I gained a strong experimental and theoretical knowledge of single molecule tracking, but also I developed a new method of super-resolution imaging allowing to study the dynamics of endogenous proteins at ultra-high density. Using single protein tracking to study synaptogenic adhesion proteins in neurons, we demonstrated that, like integrins, Neuroligin-1 is a ligand-activated adhesion molecule and that a phosphotyrosine switch controls the competitive binding of scaffolds to its intracellular tail.
Since, January 2011, I am co-leading an autonomous team with Olivier Thoumine (Biophysics of Adhesion and Cytoskeleton, IINS, Bordeaux). In a precept study, my group unraveled the key spatiotemporal molecular events leading to integrins activation by talin in mature adhesion sites. In this study, we combined super-resolution imaging and innovative single protein tracking methods to decipher the nanoscale dynamics of integrins and talin within adhesion sites. This is the pioneering study using super-resolution imaging and single protein tracking to tackle in-depth the dynamic of adhesion sites. Using the same experimental strategy, we demonstrated, in collaboration with the group of Valerie Weaver (Cancer cell biologist, UCSF, USA), that integrin activation is mechanically controlled by large membrane glycoproteins of the glycocalyx. This study showed that a bulky glycocalyx, which is a feature of tumor cells, fosters metastatic progression by mechanically-enhancing cell surface integrin function.
Rossier O., Octeau V., Sibarita J.B., Leduc C., Tessier B., Nair D., Gatterdam V., Destaing O., Albiges-Rizo C., Tampé R., Cognet L, Choquet D., Lounis B., and Giannone G. (2012).Integrins β1 and β3 display distinct dynamic nanoscale organizations inside focal adhesions. Nature Cell Biology, 14, 1231-1231.
Matthew J. Paszek M.J., Dufort C.C., Rossier O., Bainer R., Mouw J.K., Godula K., Hudak J.E., Lakins J.N., Wijekoon A., Cassereau L., Rubashkin M.G., Magbanua M.J., Thorn K.S., Davidson M.W., Rugo H.S., Park J.W., Hammer D.A, Giannone G., Bertozzi C.R, Weaver V.M. The cancer cell glycocalyx mechanically primes integrin-dependent growth and survival. Nature, in press
Giannone G., Mondin M., Grillo-Bosch D., Tessier B., Saint-Michel E., Czöndör K., Sainlos M., Choquet D., Thoumine O.(2013). Neurexin-1β binding to neuroligin-1 triggers the preferential recruitment of PSD-95 versus gephyrin through tyrosine phosphorylation of neuroligin-1. Cell Reports, 3, 1996-2007.
Giannone, G., Hosy, E., Levet, F., Constals, A., Schulze, K., Sobolevsky, A. I., Rosconi, M. P., Gouaux, E., Tampé, R., Choquet, D. and Cognet, L. (2010).Dynamic super-resolution imaging of endogenous proteins on living cells at ultra-high density. Biophys J 99, 1303-1310.
Giannone, G., Dubin-Thaler, B. J., Rossier, O., Cai, Y., Chaga, O., Jiang, G., Beaver, W., Dobereiner, H. G., Freund, Y., Borisy, G., and Sheetz, M. P. (2007) Lamellipodial Actin Mechanically Links Myosin Activity with Adhesion-Site Formation. Cell 128, 561-575.
- Violaine Moreau
Rapporteur, CR1 INSERM, Univ. de Bordeaux
- Bernhard Wehrle-Haller
Rapporteur, Professeur, Univ. de Genève, Switzerland
- Laurent Blanchoin
Rapporteur, DR1 CNRS, Univ. Joseph Fourier, CEA
- Maxime Dahan
Examinateur, DR1 CNRS, Univ. Pierre et Marie Curie, Institut Curie
- Brahim Lounis
Examinateur, professeur, Univ. de Bordeaux, Institut d’Optique
Dernière mise à jour le 02.06.2014