Differential Binding of Transforming Growth Factor-β1, -β2, and -β3 by Fibroblasts and Epithelial Cells Measured by Affinity Cross-Linking of Cell Surface Receptors

A murine fibroblast cell line (AKR-2B clone 84A) and an epithelial cell line (BALB/MK) were compared for their ability to bind different transforming growth factor-β (TGFβ) species. The results of competitive binding assays indicated that the epithelial cells had a higher affinity for TGFβ than the fibroblasts. This difference may be the basis for the sensitivity of epithelial cells to much lower concentrations of TGF/S than fibroblasts. Affinity cross-linking studies showed that both cell types express the three cell surface TGFβ-binding molecules that have been previously described for a variety of cell types. The complexity of these cell surface binding proteins was further evaluated using all possible combinations of radiolabeled ligands in competition with each of the three unlabeled TGFβ species. Differences in the ability of specific TGFβ types to compete with radiolabeled TGFβ2 for binding to the type I and II receptors were observed, with TGFβ1 being more potent for epithelial cells, and TGFβ2 be...