title: Interaction Analyses of the Integrin β2 Cytoplasmic Tail with the F3 FERM Domain of Talin and 14-3-3ζ Reveal a Ternary Complex with Phosphorylated Tail.
abstract: Integrins, which are heterodimeric (α and β subunits) signal-transducer proteins, are essential for cell adhesion and migration. β cytosolic tails (β-CTs) of integrins interact with a number of cytosolic proteins including talin, Dok1, and 14-3-3ζ. The formation of multiprotein complexes with β-CTs is involved in the activation and regulation of integrins. The leukocyte-specific β2 integrins are essential for leukocyte trafficking, phagocytosis, antigen presentation, and proliferation. In this study, we examined the binding interactions between integrin β2-CT and T758-phosphorylated β2-CT with positive regulators talin and 14-3-3ζ and negative regulator Dok1. Residues of the F3 domain of talin belonging to the C-terminal helix, β-strand 5, and the adjacent loop were found to be involved in the binding interactions with β2-CT. The binding affinity between talin F3 and β2-CT was reduced when β2 T758 was phosphorylated, but this modification promoted 14-3-3ζ binding. However, we were able to detect stable ternary complex formation of T758-phosphorylated β2-CT, talin F3, and 14-3-3ζ that involved the repositioning of talin F3 on β2-CT. We showed that Dok1 binding to β2-CT was reduced in the presence of 14-3-3ζ and when β2 T758 was phosphorylated. Based on these data, we propose a sequential model of β2 integrin activation involving these molecules. Our study provides for the first time insights toward β2 integrin activation that involves a multiprotein complex.
authors.affiliation: School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.
authors.forename: Deepak
authors.initials: D
authors.lastname: Chatterjee
authors.affiliation: School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.
authors.forename: Lewis Lu
authors.initials: LL
authors.lastname: Zhiping
authors.affiliation: School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore. Electronic address: smtan@ntu.edu.sg.
authors.forename: Suet-Mien
authors.initials: SM
authors.lastname: Tan
authors.affiliation: School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore. Electronic address: surajit@ntu.edu.sg.
authors.forename: Surajit
authors.initials: S
authors.lastname: Bhattacharjya
mesh_terms: D048948:14-3-3 Proteins / Q000378:metabolism*; D018821:CD18 Antigens / Q000378:metabolism*; D008954:Models, Biological; D010766:Phosphorylation; D011485:Protein Binding; D055503:Protein Multimerization; D011499:Protein Processing, Post-Translational; D016608:Talin / Q000378:metabolism*
chemical_list: D048948:14-3-3 Proteins; D018821:CD18 Antigens; D016608:Talin
keywords: 14-3-3; NMR; protein–protein interaction; talin; β2 integrins