Heparin and heparan sulphate protect basic fibroblast growth factor from non-enzymic glycosylation

Non-enzymic glycosylation of basic fibroblast growth factor (bFGF, FGF-2) h as recently been demonstrated to decrease the mitogenic activity of intrace llular bFGF. Loss of this bioactivity has been implicated in impaired wound healing and microangiopathies of diabetes mellitus. In addition to intrace llular localization, bFGF is also widely distributed in the extracellular m atrix, primarily bound to heparan sulphate proteoglycans (HSPGs). Nonethele ss, it is not clear if non-enzymic glycosylation similarly inactivates matr ix-bound bFGF. To investigate this, we measured the effect of non-enzymic g lycosylation on bFGF bound to heparin, heparan sulphate and related compoun ds. Incubation of bFGF with the glycosylating agents glyceraldehyde 3-phosp hate (G3P; 25 mM) or fructose (250 mM) resulted in loss of 90 % and 40 % of the mitogenic activity of bFGF respectively. Treatment with G3P and fructo se also decreased the binding of bFGF to a heparin column. If heparin was a dded to bFGF prior to non-enzymic glycosylation, the mitogenic activity and heparin affinity of bFGF were nearly completely preserved. A similar prote ctive effect was demonstrated by heparan sulphate, low-molecular-mass hepar in and the polysaccharide dextran sulphate, but not by chondroitin sulphate . Whereas non-enzymic glycosylation of bFGF with G3P impaired its ability t o stimulate c-myc mRNA expression in fibroblasts, no such impairment was no ticeable when bFGF was glycosylated in the presence of heparin. Taken toget her, these results suggest that HSPG-bound bFGF is resistant to non-enzymic glycosylation-induced loss of activity. Therefore, alteration of this pool probably does not contribute to impaired wound healing seen in diabetes me llitus.