Identification of cell surface binding sites for PC-cell-derived growth factor, PCDGF, (epithelin/guanulin precursor) on epithelial cells and fibroblasts

PC cell derived growth factor (PCDGF) is an 88-kDa glycoprotein purified from the culture medium of the highly tumorigenic mouse teratoma-derived cell line PC. PCDGF was shown to stimulate the proliferation of 3T3 fibroblasts and PC cells. Amino acid sequencing of PCDGF indicated its identity to the precursor for the 6-kDa polypeptides epithelins and granulins, In this paper, we investigated the binding of PCDGF to the mink lung epithelial cell line CCL64. Scatchard analysis indicates that I-125-PCDGF binding to CCL64 cells is curvilinear, corresponding to the existence of two classes of binding sites: high affinity binding sites (560+/-170 sites/cell) with a K-d1 of 43+/-15 pM and low affinity binding sites (16,350+/-5900 sites/cell) with a K-d2 of 3.9+/-1.9 nM. I-125-PCDGF was chemically crosslinked to cell surface receptors on CCL64 cells with disuccinimidyl suberate, A major crosslinked band of about 190 kDa with radiolabeled PCDGF was detected after SDS-PAGE, suggesting the presence of PCDGF binding sites with molecular weight of about 120 kDa, I-125-PCDGF crosslinking studies indicate the presence of PCDGF binding sites with a molecular weight similar to those of binding sites on CCL64 cells on the surface of two other PCDGF-responsive cell lines, 3T3 fibroblasts and PC cells. These data suggest that the receptors for PCDGF are widely distributed on cells of distinct embryonic origin. (C) 1998 Academic Press.