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Mechanobiology of Disease
Tuesday Speaker Abstracts
12
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.