Structural basis of Focal Adhesion Kinase activation on lipid membranes

Focal adhesion kinase (FAK) is a key component of the membrane proximal signaling layer in focal adhesion complexes, regulating important cellular processes, including cell migration, proliferation, and survival. In the cytosol,FAKadopts an autoinhibited state but is activated upon recruitment into focal adhesions, yet how this occurs or what induces structural changes is unknown. Here, we employ cryo-electron microscopy to reveal howFAKassociates with lipid membranes and how membrane interactions unlockFAKautoinhibition to promote activation. Intriguingly, initial binding ofFAKto the membrane causes steric clashes that release the kinase domain from autoinhibition, allowing it to undergo a large conformational change and interact itself with the membrane in an orientation that places the active site toward the membrane. In this conformation, the autophosphorylation site is exposed and multiple interfaces align to promoteFAKoligomerization on the membrane. We show that interfaces responsible for initial dimerization and membrane attachment are essential forFAKautophosphorylation and resulting cellular activity including cancer cell invasion, while stableFAKoligomerization appears to be needed for optimal cancer cell proliferation in an anchorage-independent manner. Together, our data provide structural details of a key membrane bound state ofFAKthat is primed for efficient autophosphorylation and activation, hence revealing the critical event in integrin mediatedFAKactivation and signaling at focal adhesions.