title: The vinculin binding sites of talin and alpha-actinin are sufficient to activate vinculin.
abstract: Vinculin regulates both cell-cell and cell-matrix junctions and anchors adhesion complexes to the actin cytoskeleton through its interactions with the vinculin binding sites of alpha-actinin or talin. Activation of vinculin requires a severing of the intramolecular interactions between its N- and C-terminal domains, which is necessary for vinculin to bind to F-actin; yet how this occurs in cells is not resolved. We tested the hypothesis that talin and alpha-actinin activate vinculin through their vinculin binding sites. Indeed, we show that these vinculin binding sites have a high affinity for full-length vinculin, are sufficient to sever the head-tail interactions of vinculin, and they induce conformational changes that allow vinculin to bind to F-actin. Finally, microinjection of these vinculin binding sites specifically targets vinculin in cells, disrupting its interactions with talin and alpha-actinin and disassembling focal adhesions. In their native (inactive) states the vinculin binding sites of talin and alpha-actinin are buried within helical bundles present in their central rod domains. Collectively, these results support a model where the engagement of adhesion receptors first activates talin or alpha-actinin, by provoking structural changes that allow their vinculin binding sites to swing out, which are then sufficient to bind to and activate vinculin.
authors.affiliation: Department of Biochemistry, St. Jude Children's Research Hospital, 332 North Lauderdale Street, Memphis, TN 38105, USA.
authors.forename: Philippe R J
authors.initials: PR
authors.lastname: Bois
authors.forename: Brendan P
authors.initials: BP
authors.lastname: O'Hara
authors.forename: Daniel
authors.initials: D
authors.lastname: Nietlispach
authors.forename: John
authors.initials: J
authors.lastname: Kirkpatrick
authors.forename: Tina
authors.initials: T
authors.lastname: Izard
mesh_terms: D000185:Actinin / Q000737:chemistry*; D000199:Actins / Q000737:chemistry; D000818:Animals; D001665:Binding Sites; D002448:Cell Adhesion; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D051379:Mice; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence; D018715:Microscopy, Video; D008954:Models, Biological; D008968:Molecular Conformation; D041681:NIH 3T3 Cells; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D020349:Surface Plasmon Resonance; D016608:Talin / Q000737:chemistry*; D013997:Time Factors; D016596:Vinculin / Q000737:chemistry*
chemical_list: D000199:Actins; D016608:Talin; D000185:Actinin; D016596:Vinculin