molecular docking study on the potency of glycosaminoglycans (gags) as co-activators of fibroblasts proliferation and differentiation

Fibroblast growth factors (FGF) are heparin-binding polypeptides that control differentiation, growth and migration of many cell types. The signaling in the FGF pathway implies the dimerization of their corresponding cell surface receptors and consequently their activation through autophosphorylation of their cytoplasmatic domains. This process is modulated by heparan-sulfates (HS) or heparan-sufate-proteoglycans (HSPG) present in great abundance on cell surfaces. Different aspects of this modulation were a matter of debate in the last years in the field literature and some of them still remains unclear. The present study is trying to give some answers to a part of these problems by using quantitatively physical theoretical models of the molecules involved in these processes. We aimed to explain, through the aid of molecular docking techniques, the experimental findings about the activation of FGF receptors by small saccharides (di- and tetrasaccharides) and as a result we propose a model for this process. Also, the findings resulted from docking experiments of longer oligosaccharides (hexa- and octasaccharides) offer insights about the stoichiometry of the receptorial complex, supporting a (2:2:2)FGF:FGFR:HS ratio scheme rather than a (2:2:1)FGF:FGFR:HS one, in accordance with recent experiments on the subject published in the literature.