Molecular mechanisms of integrin activation by kindlin during cell adhesion
Defended on November 29, 2017
Interdisciplinary Institute for NeuroScience (IINS), UMR 5297 CNRS/Université de Bordeaux, Team: Spatio-temporal and mechanical control of motile structures.
Supervisor: Olivier ROSSIER CR INSERM, IINS, Bordeaux,
Integrin-mediated cell adhesion to the extracellular matrix is involved in critical cellular functions such as migration, proliferation and differentiation, and its deregulation contributes to pathologies such as cancer. The increase of integrin affinity to the extracellular ligand, called integrin activation, is crucial to these functions. There is a complex orchestration between multiple proteins binding to α and β integrin cytoplasmic tails to regulate integrin activation and connection to F-actin. For instance, talins and kindlins play complementary and synergistic role during integrin activation, but the mechanisms underlying this relationship are unknown. Using single protein tracking and superresolution microscopy on kindlins carrying point mutations/deletion combined with functional rescue experiments in genetically engineered cells, we could directly link the molecular behavior of kindlin with its function in integrin adhesion sites (IAS). We found that kindlin-2 displayed lateral free diffusion along the plasma membrane outside and inside IAS, whereas talin-1 is mostly localized inside IAS, where it is immobile, and that the the PH domain of kindlin-2 is crucial for its recruitment and free-diffusion at the plasma membrane. Using kindlin-1/kindlin-2 double KO cells, we demonstrated that kindlin-2 membrane recruitment and diffusion are crucial for cell spreading and favor adhesion formation. This suggests that kindlin uses a different route than talin to reach integrins and trigger their activation, providing a possible molecular basis for their complementarity during integrin activation.
Using single protein tracking to study cell migration. Thomas Orré*, Amine Mehidi*, Sophie Massou, Olivier Rossier, Grégory Giannone. *co-first authors. Submitted to Methods in Molecular Biology.
Kindlin membrane recruitment and diffusion are essential for integrin activation. T. Orré, B. Kastberger, M. Theodosiou, Z. Karatas, J.B. Sibarita, R. Fässler, B. WehrleHaller, O. Rossier and G. Giannone (in preparation)