Description

Focal Adhesion Kinase (FAK) is a key component of the membrane bound signalling layer in the focal adhesions (FA) complex. FAK is activated in FAs as attached stress fibres apply forces to the complex and its signalling coordinates the maturation and turnover of FAs, required for directional cell migration. Using cryo-EM in combination with biochemical and cell biology experiments we showed that FAK adopts an oligomeric and primed assembly as it binds to PI(4,5)P2 lipids in the membrane at FAs (Figure). In this conformation the kinase active site is occluded by the membrane, thereby preventing high turn-over activity. This suggests that forces applied to FAs can lift the kinase domain from the membrane, exposing its active site and enabling phosphorylation of the nearby activation loop by the associated Src kinase, leading to full catalytic FAK activity. We currently study how FAK interacts with structural components in FAs and how these interactions link force transduction in FAs to the biochemical activation of FAK. We further use our mechanistic insights to design strategies to prevent FA signalling. Resulting agents could prevent cancer invasion and metastasis of advanced tumours. To this end, we collaborated on the discovery of an inhibitor that traps Src in an inactive conformation, thereby preventing its interaction and activation of FAK. This inhibitor is currently tested in clinical trials.

 

a) Fibroblast-like cell with Focal Adhesions in green and actin in red. (b) Schematic of the layered architecture in the Focal Adhesion complex. (c) Cryo-EM maps and fitted structure of oligomeric FAK bound to a PI(4,5)P2 membrane. (d) Atomic model of an oligomeric and primed FAK assembly (yellow/cyan) on the membrane (purple), which is shown to promote FAK autophosphorylation, but not turnover activity. Modelled is a state where the autophosphorylation site (red glow) is bound to the active site of the neighbouring FAK kinase.
(a) Fibroblast-like cell with Focal Adhesions in green and actin in red. (b) Schematic of the layered architecture in the Focal Adhesion complex. (c) Cryo-EM maps and fitted structure of oligomeric FAK bound to a PI(4,5)P2 membrane. (d) Atomic model of an oligomeric and primed FAK assembly (yellow/cyan) on the membrane (purple), which is shown to promote FAK autophosphorylation, but not turnover activity. Modelled is a state where the autophosphorylation site (red glow) is bound to the active site of the neighbouring FAK kinase.