| Research Abstract |
Ryudocan, a heparan sulfate proteoglycan, was isolated from human endothelial-like EAhy926 cells by the combination of ion-exchange and immuno-affinity chromatographies. Purified human ryudocan had biochemical properties similar to those of rat ryudocan isolated from microvascular endothelial cells. Human ryudocan contained only heparan sulfate (HS) glycosaminoglycan chains along with a core protein having an apparent molecular mass of 30 kDa. We evaluated the interactions between purified human ryudocan and several extracellular ligands by using a solid-phase binding assay. It was found that basic fibroblast growth factor (bFGF), midkine (MK), and tissue factor pathway inhibitor (TFPI) exhibited significant ryudocan binding. Heparitinase, but not chondroitin ABC lyase treatment, destroyed the ability of ryudocan binding to bFGF,MK,and TFPI.Heparin and HS,but not chondroitin surfate, inhibited such ryudocan binding. Thus, the HS chains of ryudocan appear to be responsible for its binding to bFGF,MK,and TFPI.The apparent dissociation constants for purified ryudokan were bFGF,0.50 nM ; MK,0.30 nM ; and TFPI,0.74 nM.Immunohistochemical analysis revealed that ryudocan was expressed in peripheral nerve tissues, fibrous connective tissues, and placental trophoblasts. These findings suggest that ryudocan may possess multiple biologic functions, such as bFGF modulation, neurite growth promotin, and anticoagulation, via HS-binding effectors in the cellular microenvironment.
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