Molecular Basis of the Ligand Binding Specificity of αvβ8 Integrin
Access this Article
Search this Article
This research was originally published in the Journal of Biological Chemistry. Akio Ozawa, Yuya Sato, Tsukasa Imabayashi, Toshihiko Uemura, Junichi Takagi and Kiyotoshi Sekiguchi. Molecular Basis of the Ligand Binding Specificity of αvβ8 Integrin. J. Biol. Chem. 2016; 291: 11551-11565 © the American Society for Biochemistry and Molecular Biologyαvβ8 is an integrin that recognizes an Arg-Gly-Asp (RGD) motif and interacts with fibronectin, vitronectin, and latent TGF-β1. We comprehensively determined the binding activity of the αvβ8 integrin toward 25 secreted proteins having an RGD motif. The αvβ8 integrin strongly bound to latent TGF-β1 but showed marginal activity for other RGD-containing proteins, including fibronectin and vitronectin. Site-directed mutagenesis of latent TGF-β1 demonstrated that the high affinity binding of αvβ8 integrin to latent TGF-β1 was defined by Leu-218 immediately following the RGD motif within the latency-associated peptide of TGF-β1. Consistent with the critical role of Leu-218 in latent TGF-β1 recognition by αvβ8 integrin, a 9-mer synthetic peptide containing an RGDL sequence strongly inhibited interactions of latent TGF-β1 with αvβ8 integrin, whereas a 9-mer peptide with an RGDA sequence was ∼60-fold less inhibitory. Because αvβ3 integrin did not exhibit strong binding to latent TGF-β1 or distinguish between RGDL- and RGDA-containing peptides, we explored the mechanism by which the integrin β8 subunit defines the high affinity binding of latent TGF-β1 by αvβ8 integrin. Production of a series of swap mutants of integrin β8 and β3 subunits indicated that the high affinity binding of αvβ8 integrin with latent TGF-β1 was ensured by interactions between the Leu-218 residue and the β8 I-like domain, with the former serving as an auxiliary recognition residue defining the restricted ligand specificity of αvβ8 integrin toward latent TGF-β1. In support of this conclusion, high affinity binding toward the αvβ8 integrin was conferred on fibronectin by substitution of its RGDS motif with an RGDL sequence.
- Journal of Biological Chemistry
Journal of Biological Chemistry 291(22), 11551-11565, 2016-03
American Society for Biochemistry and Molecular Biology