Newt epidermal cell migration over collagen and fibronectin involves different mechanisms

Effects of the synthetic peptides, Arg-Gly-Asp-Ser (RGDS), the amino acid sequence representing the fibroblast attachment site in fibronectin, and Arg-Gly-Glu-Ser (RGES), on collagen- and fibronectin-mediated migration in newt epidermal cells were compared. When RGDS at 50 μg ml− 1 was included in the incubation medium of skin explants, migration in fibronectin-coated dishes was almost totally blocked. In type I collagencoated dishes, this concentration of RGDS also inhibited migration, but to a lesser degree than on fibronectin. With 250 μg ml− 1 of RGES in the medium, the reverse was true. Here, migration on collagen was practically non-existent, while migration on fibronectin was affected only moderately. Collagen-mediated migration was sensitive to RGDS even when the peptide was added after migration on the coated substratum was well underway. At a coating concentration of 10 μg ml−1 CB3, a cyanogen bromide fragment of the collagen alpha 1(1) chain, which contains no RGD sequences, was as good a migration substratum as intact collagen applied at the same coating concentation. At lower concentrations intact collagen was somewhat better than equivalent concentrations of CB3. The presence of RGDS in the medium throughout an experiment inhibited migration in CB3-coated dishes in a manner similar to its effect in dishes coated with collagen. On both substrata there appeared to be a peptidesensitive and a peptide-insensitive component to migration. The inhibitory effect of RGES on CBS-mediated migration was also similar to its effect in collagen-coated dishes. Monensin, an ionophore known to block secretion and endocytosis inhibited migration on fibronectin and collagen to a small, but statistically insignificant degree. A more pronounced, statistically significant effect was seen in CBScoated dishes. Electrophoretic analysis of the cell extract and the medium of cells migrating overnight on CB3 in the presence of [35S] methionine showed no evidence of fibronectin secretion by the migrating cells. These results indicate that newt epidermal cells use different mechanisms as they migrate over fibronectin and collagen. The data could be explained by the existence of two classes of extracellular matrix receptors on epidermal cells or one class of receptor that binds to the active site(s) in fibronectin and collagen with different affinities. Our inability to detect fibronectin secretion by cells migrating on CB3 and the collagen-like sensitivity of CB3-mediated migration to RGDS suggests that some epidermal receptors involved in migration are capable of recognizing more than just the RGD sequence. The effect of monensin in CB3-coated dishes may be an indication that receptor recycling occurs during migration over some substrata.