title: Structural Insights How PIP2 Imposes Preferred Binding Orientations of FAK at Lipid Membranes.
abstract: Focal adhesion kinase (FAK) is a multidomain protein (FERM-kinase-FAT) with important signaling functions in the regulation of cell-substrate adhesions. Its inactive, autoinhibited form is recruited from the cytoplasm to the plasma membrane, where it becomes activated at PIP2 enriched regions. To elucidate the molecular basis of activation, we performed a systematic screening of binding orientations of FAK's autoinhibited FERM-kinase complex, as well as of the dissociated FERM and kinase domains alone, on model plasma membranes using coarse-grained scFix MARTINI simulations, partially corroborated by atomistic MD simulations. The proteins adopted many more different orientations than previously thought. The presence of PIP2 tuned and narrowed the complex map of competing interfacial orientations. The dissociated FERM domain most frequently interacted with the membrane through its autoinhibitory interface rather than with the "basic patch" residues. These findings suggest a PIP2-dependent activation mechanism in which membrane binding of the dissociated FERM domain competes with the rebinding of the kinase domain. This competition could promote FAK autophosphorylation on Y397 and subsequent Src binding. The orientation of peripheral proteins at membranes is crucial to understand cell adhesion processes and is furthermore required to exploit steered molecular dynamics to predict how tensile forces might switch their active states.
authors.affiliation: Laboratory of Applied Mechanobiology, Department of Health Sciences and Technology, ETH Zürich , 8093 Zürich, Switzerland.
authors.forename: Florian A
authors.identifier: 0000-0002-6628-4451
authors.initials: FA
authors.lastname: Herzog
authors.affiliation: Laboratory of Applied Mechanobiology, Department of Health Sciences and Technology, ETH Zürich , 8093 Zürich, Switzerland.
authors.forename: Lukas
authors.initials: L
authors.lastname: Braun
authors.affiliation: Laboratory of Applied Mechanobiology, Department of Health Sciences and Technology, ETH Zürich , 8093 Zürich, Switzerland.
authors.forename: Ingmar
authors.initials: I
authors.lastname: Schoen
authors.affiliation: Laboratory of Applied Mechanobiology, Department of Health Sciences and Technology, ETH Zürich , 8093 Zürich, Switzerland.
authors.forename: Viola
authors.initials: V
authors.lastname: Vogel
mesh_terms: D001665:Binding Sites; D051417:Focal Adhesion Kinase 1 / Q000737:chemistry*; D006801:Humans; D008051:Lipid Bilayers / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D011487:Protein Conformation
chemical_list: D008051:Lipid Bilayers; D051417:Focal Adhesion Kinase 1; C496050:PTK2 protein, human