title: Characterization of 14-3-3-ζ Interactions with integrin tails.
abstract: Integrins are a family of heterodimeric (α+β) adhesion receptors that play key roles in many cellular processes. Integrins are unusual in that their functions can be modulated from both outside and inside the cell. Inside-out signaling is mediated by binding adaptor proteins to the flexible cytoplasmic tails of the α- and β-integrin subunits. Talin is one well-known intracellular activator, but various other adaptors bind to integrin tails, including 14-3-3-ζ, a member of the 14-3-3 family of dimeric proteins that have a preference for binding phosphorylated sequence motifs. Phosphorylation of a threonine in the β2 integrin tail has been shown to modulate β2/14-3-3-ζ interactions, and recently, the α4 integrin tail was reported to bind to 14-3-3-ζ and associate with paxillin in a ternary complex that is regulated by serine phosphorylation. Here, we use a range of biophysical techniques to characterize interactions between 14-3-3-ζ and the cytoplasmic tails of α4, β1, β2 and β3 integrins. The X-ray structure of the 14-3-3-ζ/α4 complex indicates a canonical binding mode for the α4 phospho-peptide, but unexpected features are also observed: residues outside the consensus 14-3-3-ζ binding motif are shown to be essential for an efficient interaction; in contrast, a short β2 phospho-peptide is sufficient for high-affinity binding to 14-3-3-ζ. In addition, we report novel 14-3-3-ζ/integrin tail interactions that are independent of phosphorylation. Of the integrin tails studied, the strongest interaction with 14-3-3-ζ is observed for the β1A variant. In summary, new insights about 14-3-3-ζ/integrin tail interactions that have implications for the role of these molecular associations in cells are described.
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom. roman.bonet@iqac.csic.es
authors.forename: Roman
authors.initials: R
authors.lastname: Bonet
authors.forename: Ioannis
authors.initials: I
authors.lastname: Vakonakis
authors.forename: Iain D
authors.initials: ID
authors.lastname: Campbell
mesh_terms: D048948:14-3-3 Proteins / Q000737:chemistry* / Q000378:metabolism*; D018360:Crystallography, X-Ray; D003593:Cytoplasm / Q000378:metabolism; D039441:Integrin alpha4 / Q000737:chemistry* / Q000378:metabolism*; D039641:Integrin beta Chains / Q000737:chemistry* / Q000378:metabolism*; D051419:Paxillin / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D016608:Talin / Q000737:chemistry / Q000378:metabolism
chemical_list: D048948:14-3-3 Proteins; D039641:Integrin beta Chains; D051419:Paxillin; D016608:Talin; D039441:Integrin alpha4
keywords: HSQC; ITC; NMR; X-ray crystallography; heteronuclear single quantum coherence; integrin cytoplasmic domains; isothermal titration calorimetry; nuclear magnetic resonance; protein–protein interactions; wild type; wt