Purification of a basic fibroblast growth factor-binding proteoglycan from bovine cardiac plasma membrane

A heparan sulfate proteoglycan (HSPG) from bovine cardiac plasma membrane was purified to homogeneity using either isoelectric focusing or anion-exchange chromatography, followed by affinity chromatography on immobilized basic fibroblast growth factor (bFGF). Fractions were assayed for bFGF-binding activity using 125I-bFGF as a probe. Purified proteoglycan ran as a broad band on SDS-PAGE, spanning an apparent molecular mass range of 100-200 kDa, and could be incorporated into liposomes. Digestion of radioiodinated proteoglycan with heparitinase yielded a product of 73 kDa, while digestion with chondroitinase ABC did not change the apparent molecular mass. Monoclonal antibody directed against the ectodomain of another plasma membrane HSPG, syndecan, failed to recognize the purified cardiac proteoglycan on immunoblots. We conclude that adult bovine myocardium contains a membrane-associated bFGF-binding heparan sulfate proteoglycan containing little or no chondroitin sulfate and that this HSPG may be distinct from those of the syndecan family of heparan sulfate proteoglycans.