Recombinant N-terminal Fragment of Human Vitronectin Promotes Osteoblast Adhesive Responses via αvβ3 and αvβ5 Integrins.

Abstract

Vitronectin is a key extracellular matrix glycoprotein, but the functional contribution of specific residues within its N-terminal region to osteoblast activity remains poorly defined. We engineered a recombinant N-terminal fragment of human vitronectin (rVn-FI; residues 20-149) and performed a comprehensive mapping study using 16 overlapping 12-mer peptides to pinpoint the exact bioactive motifs. rVn-FI significantly promoted adhesion, spreading, and migration in HOS and MG-63 osteoblast-like cells, mediated primarily by αvβ3 and αvβ5 integrins. Peptide mapping revealed that two RGD-containing motifs-Vn-FI-P6 (AECKPQVTRGDV) and Vn-FI-P7 (PQVTRGDVFTMP)-were the sole drivers of this activity. Notably, Vn-FI-P7 exhibited a significantly higher inhibitory potency against cell adhesion to vitronectin than Vn-FI-P6, suggesting that the flanking sequences in Vn-FI-P7 provide a superior conformational context for integrin binding. None of the other 14 peptides showed biological activity, confirming the absence of non-RGD-dependent binding sites within the N-terminal fragment (residues 20-149). These results define the precise functional boundaries of the vitronectin N-terminus for osteoblast interaction. Our findings highlight that the flanking sequences in Vn-FI-P7 provide a superior conformational context for RGD-integrin binding, offering specific peptide targets for enhancing the bioactivity of bone tissue engineering scaffolds.