HEPARAN-SULFATE PRIMED ON BETA-D-XYLOSIDES RESTORES BINDING OF BASIC FIBROBLAST GROWTH-FACTOR

Heparan sulfate proteoglycans (HSPG) are obligatory for receptor bindi ng and mitogenic activity of basic fibroblast growth factor (bFGF). Mu tant Chinese hamster ovary cells (pgsA-745) deficient in xylosyltransf erase are unable to initiate glycosaminoglycan synthesis and hence can not bind bFGF to low- and high-affinity cell surface receptors. Expos ure of pgsA-745 cells to beta-D-xylopyranosides containing hydrophobic aglycones resulted in restoration of bFGF binding in a manner similar to that induced by soluble heparin or by heparan sulfate (HS) normall y associated with cell surfaces. Restoration of bFGF binding correlate d with the ability of the beta-D-xylosides to prime the synthesis of h eparan sulfate. Thus, both heparan sulfate synthesis and bFGF receptor binding were induced by low concentrations (10-30 mu M) of estradiol- beta-D-xyloside and naphthyl-beta-D-xyloside, but not by cis/trans-dec ahydro-2-naphthyl-beta-D-xyloside, which at low concentration primes m ainly chondroitin sulfate. The obligatory involvement of xyloside-prim ed heparan sulfate in restoration of bFGF-receptor binding was also de monstrated by its sensitivity to heparinase treatment and by the lack of restoration activity in CHO cell mutants that lack enzymatic activi ties required to form the repeating disaccharide unit characteristic o f heparan sulfate. Xyloside-primed heparan sulfate binds to the cell s urface. Restoration of bFGF receptor binding was induced by both solub le and cell bound xyloside-primed heparan sulfate and was abolished in cells that were exposed to 0.5-1.0 M NaCl prior to the bFGF binding r eaction. These results indicate that heparan sulfate chains produced o n xyloside primers behave like heparan sulfate chains attached to cell ular core proteins in terms of affinity for bFGF and ability to functi on as low-affinity sites in a dual receptor mechanism characteristic o f bFGF and other heparin-binding growth promoting factors. (C) 1995 Wi ley-Liss, Inc.