Biophysical Society Thematic Meeting | Singapore

Mechanobiology of Disease

Tuesday Speaker Abstracts

Super-resolution Microscopy: a Window for Integrin Spatiotemporal and Mechanical Regulation Gregory Giannone . Interdisciplinary Institute for Neuroscience, University of Bordeaux, Bordeaux, France. Super-resolution fluorescence microscopy techniques revolutionized biomolecular imaging in cells by delivering optical images with spatial resolutions below the diffraction limit of light. The direct observation of biomolecules at the single molecule level enables their localization and tracking at the scale of a few tens of nanometers and opens new opportunities to study biological structures at the scale of proteins inside living cells. We are using super-resolution microscopy techniques and single protein tracking (SPT) to study adhesive and protrusive sub-cellular structures, including integrin-dependent adhesion sites and the lamellipodium. Integrin-mediated cell adhesion to the extracellular matrix and mechano-transduction are involved in critical cellular functions such as migration, proliferation and differentiation, and their deregulation contributes to pathologies such as cancer. Yet the molecular events controlling integrin biochemical and mechanical activation within adhesion sites (FAs) are still not understood. We unravel the key spatiotemporal molecular events leading to integrins activation by their main activators talin and kindlin in mature FAs. We performed SPT combined with PALM (sptPALM) and super-resolution microscopy to study integrins, talin and kindlin displacements and distributions outside versus inside mature FAs. We demonstrated that FAs are specialized platforms priming integrins immobilization and that talin and kindlin use different mechanisms to reach integrins. Using the same experimental strategy, in collaboration with the group of Valerie Weaver (UCSF, USA), we studied how bulky membrane glycoproteins regulate integrin diffusive behavior and activation. Our findings support a model where large glycoproteins act as physical "steric" barriers impeding integrins immobilization and thus funneling integrins clustering into adhesive contacts. Thus control of membrane nano-topology by the glycocalyx could mechanically enhanced integrin activation and could foster metastatic progression.

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