title: Structural basis of the migfilin-filamin interaction and competition with integrin beta tails.
abstract: A link between sites of cell adhesion and the cytoskeleton is essential for regulation of cell shape, motility, and signaling. Migfilin is a recently identified adaptor protein that localizes at cell-cell and cell-extracellular matrix adhesion sites, where it is thought to provide a link to the cytoskeleton by interacting with the actin cross-linking protein filamin. Here we have used x-ray crystallography, NMR spectroscopy, and protein-protein interaction studies to investigate the molecular basis of migfilin binding to filamin. We report that the N-terminal portion of migfilin can bind all three human filamins (FLNa, -b, or -c) and that there are multiple migfilin-binding sites in FLNa. Human filamins are composed of an N-terminal actin-binding domain followed by 24 immunoglobulin-like (IgFLN) domains and we find that migfilin binds preferentially to IgFLNa21 and more weakly to IgFLNa19 and -22. The filamin-binding site in migfilin is localized between Pro(5) and Pro(19) and binds to the CD face of the IgFLNa21 beta-sandwich. This interaction is similar to the previously characterized beta 7 integrin-IgFLNa21 interaction and migfilin and integrin beta tails can compete with one another for binding to IgFLNa21. This suggests that competition between filamin ligands for common binding sites on IgFLN domains may provide a general means of modulating filamin interactions and signaling. In this specific case, displacement of integrin tails from filamin by migfilin may provide a mechanism for switching between different integrin-cytoskeleton linkages.
authors.affiliation: Department of Pharmacology and Interdepartmental Program in Vascular Biology and Transplantation, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
authors.forename: Yatish
authors.initials: Y
authors.lastname: Lad
authors.forename: Pengju
authors.initials: P
authors.lastname: Jiang
authors.forename: Salla
authors.initials: S
authors.lastname: Ruskamo
authors.forename: David S
authors.initials: DS
authors.lastname: Harburger
authors.forename: Jari
authors.initials: J
authors.lastname: Ylänne
authors.forename: Iain D
authors.initials: ID
authors.lastname: Campbell
authors.forename: David A
authors.initials: DA
authors.lastname: Calderwood
mesh_terms: D000818:Animals; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D003285:Contractile Proteins / Q000737:chemistry* / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D064448:Filamins; D006801:Humans; D039641:Integrin beta Chains / Q000378:metabolism*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D051379:Mice; D008840:Microfilament Proteins / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D008968:Molecular Conformation; D041681:NIH 3T3 Cells; D011485:Protein Binding
chemical_list: D015815:Cell Adhesion Molecules; D003285:Contractile Proteins; D003598:Cytoskeletal Proteins; C473794:FBLIM1 protein, human; D064448:Filamins; D039641:Integrin beta Chains; D008024:Ligands; D008840:Microfilament Proteins; C091368:integrin beta7