INTERACTION OF HEPARAN-SULFATE FROM MAMMARY CELLS WITH ACIDIC FIBROBLAST GROWTH-FACTOR (FGF) AND BASIC FGF - REGULATION OF THE ACTIVITY OF BASIC FGF BY HIGH AND LOW-AFFINITY BINDING-SITES IN HEPARAN-SULFATE

We have determined the relationship between the binding sites for acid ic fibroblast growth factor (aFGF) and basic FGF (bFGF) in heparan sul fate (HS) prepared from a panel of mammary cell lines and the ability of the HS to activate aFGF and bFGF in DNA synthesis assays. The k(a) of the HS for aFGF fell into three groups, whereas the k(d) (0.0015-0. 016 s(-1)) and the K-d (0.4-8.6 mu M) formed a continuum. bFGF possess ed a high affinity binding site (K-d 22-30 nM) with a fast k(a) (320,0 00-550,000 M-1 s(-1)), termed ''fast/high,'' and a lower affinity site (K-d 47-320 nM) with a slower k(a) (35,000-150,000 M-1 s(-1)), termed ''slow/low.'' Most of the species of HS possessed the latter binding site, which was able to activate bFGF in HS-deficient fibroblasts. How ever, the HS from the culture medium of the mammary fibroblasts and th e myoepithelial-like cells possessed both a fast/high and a slow/low b inding site and could not activate bFGF, although it could potentiate the growth-stimulatory activity of aFGF. Treatment of the HS possessin g two binding sites for bFGF with heparitinase 1 released oligosacchar ides that were able to restore the activity of bFGF in HS-deficient fi broblasts.