In previous studies, RGD-CAP (collagen-associated protein containing the RGD sequence) isolated from a collagen fiber-rich fraction of pig cartilage was found to be orthologous to human βig-h3, which is synthesized by lung adenocarcinoma cells in response to transforming growth factor-β. In the present study, we examined the effect of recombinant chick RGD-CAP on the spreading of chondrocytes and fibroblasts using RGD-CAP-coated dishes. When rabbit articular chondrocytes, chick embryonic sternal chondrocytes, rabbit peritoneal fibroblasts or human MRC5 fibroblasts were seeded on plastic dishes coated with RGD-CAP, cell spreading was enhanced compared with that on control dishes (bovine serum albumin- or β-galactosidase-coated dishes). The effect of RGD-CAP on the cell spreading required divalent cations (Mg2+ or Mn2+), and was reduced by EDTA. Monoclonal antibodies (mAbs) to the human integrin α1 or β1 subunit, but not to the α2, α3, α5 or β2 subunits, suppressed the RGD-CAP-induced spreading of human MRC5 fibroblasts. In a parallel experiment, the mAb to the α5 subunit, but not the mAb to the α1 subunit, suppressed fibronectin-induced spreading of these cells. These findings suggest that RGD-CAP is a novel ligand for integrin α1β1 that dose not bind to the RGD motif. Accordingly, an RGD-CAP fragment, which carries a deletion in the C-terminal region containing the RGD motif, was still capable of stimulating cell spreading. Copyright (C) 1999 Elsevier Science B.V.
Ohno, S., Noshiro, M., Makihira, S., Kawamoto, T., Shen, M., Yan, W., … Kato, Y. (1999). RGD-CAP (βig-h3) enhances the spreading of chondrocytes and fibroblasts via integrin α1β1. Biochimica et Biophysica Acta - Molecular Cell Research, 1451(1), 196–205. https://doi.org/10.1016/S0167-4889(99)00093-2