Chimeric peptides of statherin and osteopontin that bind hydroxyapatite and mediate cell adhesion

Extracellular matrix proteins play hey roles in controlling the activities of osteoblasts and osteoclasts in bone remodeling. These bone-specific extr acellular matrix proteins contain amino acid sequences that mediate cell ad hesion, and many of the bone-specific matrix proteins also contain acidic d omains that interact with the mineral surface and may orient the signaling domains. Here we report a fusion peptide design that is based on this natur al approach for the display of signaling peptide sequences at biomineral su rfaces. Salivary statherin contains a 15-amino acid hydroxyapatite binding domain (N15) that is loosely helical in solution. To test whether N15 can s erve to orient active peptide sequences on hydroxyapatite, the RGD and flan king residues from osteopontin were fused to the C terminus. The fusion pep tides bound tightly to hydroxyapatite, and the N15-PGRGDS peptide mediated the dose-dependent adhesion of Mo alpha(V), melanoma cells when immobilized on the hydroxyapatite surface. Experiments with an integrin-sorted Mo alph a(V), subpopulation demonstrated that the alpha(V)beta(3), integrin was the primary receptor target for the fusion peptide. Solid state NMR experiment s showed that the RGD portion of the hydrated fusion peptide is highly dyna mic on the hydroxyapatite surface. This fusion peptide framework may thus p rovide a straightforward design for immobilizing bioactive sequences on hyd roxyapatite for biomaterials, tissue engineering, and vaccine applications.