ABSTRACT: This work reports on the role of the synergy peptide PHSRN in mediating the adhesion of
cells. The attachment of baby hamster kidney cells and 3T3 Swiss fibroblasts to model substrates presenting
either GRGDS or PHSRN was evaluated using self-assembled monolayers of alkanethiolates on gold
presenting the peptide ligands mixed with tri(ethylene glycol) groups. These substrates permit rigorous
control over the structures and densities of peptide ligands and at the same time prevent nonspecific
interactions with adherent cells. Both cell types attached efficiently to monolayers presenting either the
RGD or the PHSRN peptide but not to monolayers presenting scrambled peptide GRDGS or HRPSN.
Cell attachment was comparable on substrates presenting either peptide ligand but less efficient than on
substrates presenting the protein fibronectin. The degree of cell spreading, however, was substantially
higher on substrates presenting RGD relative to PHSRN. Staining of 3T3 fibroblasts with anti-vinculin
and phalloidin revealed clear cytoskeletal filaments and focal adhesions for cells attached by way of
either RGD or PHSRN. Inhibition experiments showed that the attachment of 3T3 fibroblasts to monolayers
presenting RGD could be inhibited completely by a soluble RGD peptide and partially by a soluble PHSRN
peptide. IMR 90 fibroblast attachment to monolayers presenting PHSRN could be inhibited with antiintegrin
R5 or anti-integrin !1 antibody. This work demonstrates unambiguously that PHSRN alone can
support the attachment of cells and that the RGD and PHSRN bind competitively to the integrin receptors.