Deciphering the spatiotemporal and mechanical regulation of actin and integrin regulators at the nanoscale

Speaker Dr Grégory Giannone, CNRS, Interdisciplinary Institute for Neuroscience, University of Bordeaux, Bordeaux, France

Title Deciphering the spatiotemporal and mechanical regulation of actin and integrin regulators at the nanoscale

Host Matthias Krause

 

Abstract 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 to study adhesive and protrusive sub-cellular structures, including integrin-dependent adhesion sites, and the lamellipodium in migrating cells.

Actin filaments generate forces driving membrane movements during trafficking, endocytosis and cell migration. Reciprocally, adaptations of actin networks to mechanical forces regulate their assembly and architecture. Yet, a direct demonstration of forces acting on actin regulators at sites of actin assembly in cells is missing. The lamellipodium is an archetypal membrane protrusion generated by a branched actin network dependent on the Arp2/3 complex, itself activated by the WAVE complex. Using single protein tracking and optical tweezers, we showed that piconewton forces generated by actin filament elongation mechanically regulate WAVE complex dynamics and function in the lamellipodium during cell migration.

While considerable knowledge has been garnered on the 3D nanoscale organization of the integrin adhesion complex, mechano-sensing properties of integrin associated proteins and their molecular dynamics from cell models in vitro, our understanding of integrin adhesions is still limited in vivo, where the genetic regulation and biophysical properties of the extracellular environment is more complex. With super-resolution microscopy and single protein tracking, we use developing Drosophila embryonic muscle attachment site (MAS) as a model system to study how cells build stable force-bearing adhesion structures in a 3D environment.