Molecular basis of the interaction between glycosaminoglycans, mimetics and proteins

Heparin (H) and heparan sulfate (HS) are polysaccharides belonging to the glycosaminoglycan (GAG) family. As a proteoglycan, HS is present either in the outer face of the cell membrane or in the extra cellular matrix (ECM). HS is involved in the modulation of the communication between cells and cell-ECM. Like polyanionic molecules, H/HS are involved in a great number of GAG-protein interactions and biological activities such as blood coagulation, lipid metabolism, cell adhesion and growth factor regulation (Ori, A., 2008; Capila, I., 2002). Recently, it has been shown an increasing in H/HS-protein complexes structural studies. This lead to an improved understanding of H/HS-protein interactions. Does H/HS interaction network represent the crossroad of the cell-ECM molecular net? The aim of the present study is oriented to clarify some H/HS network aspects, for instance the H/HS-fibroblast growth factor (FGF) family interactions, the H/HS-βamyloid (βA) and the H/HS-antithrombin III (AT) interactions. Different methods were applied to elucidate biochemical and structural data: Nuclear Magnetic Resonance (NMR), Dynamic Light Scattering (DLS) and Surface Plasmon Resonance (SPR). Literature results showed as oligosaccharides derived from H (H oligosaccharides) are able to mimic H/HS effects in H/HS-protein binding and biological activity (Linhardt, R. J., 1999; Yates, E. A., 2004; Guerrini M., 2002). According to H oligosaccharides properties, we decide to use H oligosaccharides having different sulfation pattern and derived by partial depolimerization of beef lung and pig mucosal heparin. NMR and DLS data confirm the great importance of βA folding for the chemo-physical environment as previously reported (Zagorski M. G., 1992; Mandal P. K., 2004; Valerio M., 2008). Preliminary NMR results of βAs (βA (1-40), βA (1-28) and βA (25-35))/H oligosaccharides in solution suggest a critical role in βAs stability. 1H-15N heteronuclear correlation spectroscopy (HSQC) spectra acquired before and after H tetrasaccharide and AGA*IA (see methods) addition show some interesting differences, showing the influence of sulfation and length of the chains in the aggregation phenomena. SPR results confirm the importance of sulfation pattern and monosaccharides sequence in FGF/H oligosaccharides interactions. Changing in sulfation pattern (6-O desulfation or 2-O desulfation) strongly affects FGF-1/H oligosaccharides-binding mechanisms.