Effects of the binding of a dextran derivative on fibroblast growth factor2: Secondary structure and receptor-binding studies

CMDB (carboxymethyldextran-benzylamide) are dextrans statistically substitu ted with carboxymethyl and benzylamide groups which can mimick some of the biological properties of heparin. It has previously been shown that CMDB in hibit autocrine growth of breast tumor cells (Bagheri-Yarmand et at., Bioch em Biophys Res Commun 239: 424-428, 1997) and selectively displace fibrobla st growth factor 2 (FGF 2) from its receptor. Here, we used circular dichro ism and fluorescence anisotropy measurements to show that the conformation of FGF-2 was significantly altered upon its binding to CMDB and to short CM DB 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 fr om fluorescence anisotropy analysis. No such a complex was formed with insu lin-like growth factor (IGF-1) or epidermal growth factor (EOF). CMDB compe ted with the FGF-2 receptor for binding to FGF-2 but did not disturb the bi nding of IGF-1 and EOF to their receptors. Thus, our results highlight the selectivity of CMDB and their fragments towards FGF 2. Heparin, however, co mpetes with CMDB and their fragments for binding re, FGF 2. The carboxymeth yl and benzylamide groups of these molecules likely interact directly with a heparin-binding region of FGF-2. The resulting change in conformation dis turbs the binding of FGF-2 td its receptor and consecutively its mitogenic activity. (C) 1999 Elsevier Science Inc.