PROMOTION OF FIBROBLAST ADHESION BY TRIPLE-HELICAL PEPTIDE MODELS OF TYPE-I COLLAGEN-DERIVED SEQUENCES

The dissection of the activities mediated by type I collagen requires an approach by which the influence of triple-helical conformation can be evaluated. The alpha(1) beta(1) and alpha(2) beta(1) integrin bindi ng sites within type I collagen are dependent upon triple-helical conf ormation and contained within residues 124-822 from alpha 1(I). Seven alpha 1(I)-derived triple-helical peptides (THPs) were synthesized bas ed on charge clustering (alpha 1(I)256-270, alpha 1(I)385-396, alpha 1 (I)406-417, alpha 1(I)415-423, alpha 1(I)448-456, alpha 1(I)496-507, a nd alpha 1(I)526-537). Three additional THPs were synthesized (alpha 1 (I)85-96, alpha 1(I)433-441, and alpha 1(I)772-786) based on previousl y described or proposed activities (Kleinman, H. K., McGoodwin, E. B., Martin, G. R., Klebe, R. J., Fietzek, P. P., and Wooley, D. E. (1978) J. Biol. Chem. 253, 5642-5646; Staatz, W. D., Fok, K. F., Zutter, M. M., Adams, S. P., Rodriguez, B. A., and Santoro, S. A. (1991) J. Biol. Chem. 266, 7363-7367; San Antonio, J. D., Lander, A. D., Karnovsky, M . J., and Slayter, H. S. (1994) J. Cell Biol. 125, 1179-1188). Of the ten THPs, alpha 1(I)772-786 THP had the greatest activity, with half-m aximal normal dermal fibroblast adhesion occurring at a peptide concen tration of 1.6 mu M. Triple-helicity was essential for activity of thi s sequence, as the non-triple-helical peptide analog (alpha 1(I)772-78 6 SSP) exhibited considerably lower levels of cell adhesion promotion even at peptide concentrations as high as 100 mu M. Within the sequenc e itself, residues 784-786 (Gly-Leu-Hyp) were important for cellular r ecognition, as the alpha 1(I)772-783 THP had greatly reduced cell adhe sion activity compared with alpha 1(I)772-786 THP. Preliminary studies indicate that the beta(1) integrin subunit mediates fibroblast adhesi on to alpha 1(I)772-786 THP. The identification of fibroblast integrin binding sites within type I collagen may have important implications for understanding collagen metabolism.