Effects of the binding of a dextran derivative on fibroblast growth factor 2:: Secondary structure and receptor-binding studies

CMDB (carboxymethyldextran-benzylamide) are dextrans statistically substituted with carboxymethyl and benzylamide groups which can mimick some of the biological properties of heparin. It has previously been shown that CMDB inhibit autocrine growth of breast tumor cells (Bagheri-Yarmand et at., Biochem Biophys Res Commun 239: 424-428, 1997) and selectively displace fibroblast growth factor 2 (FGF 2) from its receptor. Here, we used circular dichroism and fluorescence anisotropy measurements to show that the conformation of FGF-2 was significantly altered upon its binding to CMDB and to short CMDB fragments prepared within this study. CMDB and fragments formed a stable 1:1 complex with FGF-2, with affinities being estimated as 20 +/- 10 nM from fluorescence anisotropy analysis. No such a complex was formed with insulin-like growth factor (IGF-1) or epidermal growth factor (EOF). CMDB competed with the FGF-2 receptor for binding to FGF-2 but did not disturb the binding of IGF-1 and EOF to their receptors. Thus, our results highlight the selectivity of CMDB and their fragments towards FGF 2. Heparin, however, competes with CMDB and their fragments for binding re, FGF 2. The carboxymethyl and benzylamide groups of these molecules likely interact directly with a heparin-binding region of FGF-2. The resulting change in conformation disturbs the binding of FGF-2 td its receptor and consecutively its mitogenic activity. (C) 1999 Elsevier Science Inc.