Focal Adhesion Kinase (FAK) is the key component of the signalling layer in focal adhesions localised on the plasma membrane and is responsible for signals emanating from the focal adhesion complex. We previously discovered that FAK interacts with PIP2 lipids in focal adhesions and this triggers its activation by inducing FAK oligomerisation, conformational changes that facilitate autophosphorylation, Src recruitment and FAK phosphorylation by Src. Currently, we are studying the atomic architecture of FAK oligomers bound to PIP2 membranes by electron microscopy (EM). Via 2D crystals of FAK on a PIP2 lipid membrane we obtained a 5.9 Å EM map which reveals the mode of oligomerisation and large membrane induced rearrangements of the regulatory FERM and kinase domains in FAK (Figure). The observed conformation suggests that FAK adopts a ‘preactivated’ primed state when bound to the membrane. We further investigate how force, induced at focal adhesion sites by actomyosin contraction, can induce changes to these structures to fully activate focal adhesion signalling. We utilize these mechanistic insights to discover highly specific allosteric FAK inhibitors. We employ a fragment based approach to identify allosteric ligands and then use structure based drug design to develop these fragments into inhibitory lead compounds.
(a) FAK 2D crystals (with Fourier transforms) formed on PIP2 membranes imaged by negative stain (upper) or cryo-EM (lower). (b) EM maps at 5.9 Å fitted with FAK domains. Each colour represents one FAK molecule containing a FERM and kinase domain. (c) EM structure of oligomeric FAK on a lipid membrane.