Triple-helical ligands selectively targeting the closed αI domain of integrin α2β1
Abstract
Integrins α1β1, α2β1, α10β1, and α11β1 serve as primary collagen receptors, recognizing the GxxGEx motif of the collagen triple helix via their αI domains. The Glu residue of the motif coordinates with a divalent metal cation at the metal ion-dependent adhesion site of the αI domain. Owing to this conserved recognition mechanism, previously identified binding sequences show low subtype selectivity. In this study, we identified triple-helical peptide ligands capable of selectively binding to the α2I domain in a manner independent of both Glu and a divalent metal cation. By employing yeast-two hybrid screening using a randomized triple-helical peptide library, we identified sequences in which canonical Glu was substituted by aliphatic residues such as Met. X-ray crystallographic analysis of the complex formed by the α2I domain and a triple-helical peptide containing GFOGMR (O: 4-hydroxyproline)—a Met-substituted variant of the canonical integrin-binding sequence GFOGER—revealed a novel binding mode. In this mode, the peptide was recognized by the closed form of the α2I domain in a metal cation-independent manner. Furthermore, this interaction mode enabled Met-containing peptides to specifically bind to the integrin α2I domain. These findings deepen our understanding of collagen recognition by collagen-binding integrins and provide insight for the discovery of ligands capable of selectively targeting collagen receptor-type integrins.
Significance
Previously identified integrin-binding sequences derived from native collagens exhibit limited selectivity for integrin subtypes, restricting their use for developing therapeutics targeting individual integrins. We identified novel peptide sequences capable of selectively binding to the integrin α2I domain through two-hybrid screening using combinatorial libraries of random triple-helical peptides expressed in yeast cells. In these sequences, the Glu residue typically required for canonical ligand engagement is substituted with aliphatic amino acids such as Met, enabling specific recognition of the closed (i.e., inactive) conformation of the α2I domain. This interaction mode appears cryptic and is likely not utilized by native ligands. The closed conformation of the integrin αI domain may be a promising target for the development of subtype-specific ligands targeting collagen-binding integrins.
Related articles
Related articles are currently not available for this article.