Nucleation of actin filaments by the Arp2/3 complex: new surprises from an old friend

Speaker Dr Guillaume Romet-Lemonne, CNRS Researcher, Institut Jacques Monod, Paris

Title Nucleation of actin filaments by the Arp2/3 complex: new surprises from an old friend

Host Matthias Krause

 

Abstract In cells, several key actin filament networks are nucleated by the Arp2/3 complex. Depending on how it is activated, the Arp2/3 complex can generate new actin filaments either as branches that grow off the sides of pre-existing ‘mother’ filaments, or as new linear filaments. While these activation mechanisms are now well understood, much less is known about the stability and turnover of Arp2/3-nucleated actin filaments. I will present recent work from our lab, where we use microfluidics and optical microscopy to manipulate and monitor individual Arp2/3-nucleated actin filaments in vitro. In particular, I will show how the stability of branched and linear filaments is affected by biochemical and mechanical factors – sometimes unexpectedly. Further, we found physiological conditions where, upon branch dissociation, the Arp2/3 complex remains bound to the mother filament and is reactivated to nucleate a new branch. I will discuss how these observations shed new light on the different active conformations of the Arp2/3 complex, and on the means by which the turnover of the resulting filaments may be controlled in cells.