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
Lu, Lewis Zhiping
Date of Issue2016
School of Biological Sciences
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.
Journal of Molecular Biology
© 2016 Elsevier Ltd. This is the author created version of a work that has been peer reviewed and accepted for publication by Journal of Molecular Biology, Elsevier. It incorporates referee’s comments but changes resulting from the publishing process, such as copyediting, structural formatting, may not be reflected in this document. The published version is available at: [http://dx.doi.org/10.1016/j.jmb.2016.08.014].