HEPARIN HEPARAN SULFATE (HP/HS) INTERACTING PROTEIN (HIP) SUPPORTS CELL ATTACHMENT AND SELECTIVE, HIGH-AFFINITY BINDING OF HP/HS/

Heparin/heparan sulfate (HP/HS), HS proteoglycans, and their binding p roteins play important roles in a variety of biological processes. Pre viously, we identified a novel cell surface HP/HS interacting protein (HIP) from human uterine epithelia and a variety of other human epithe lial and endothelial cells and cell lines (Liu, S., Smith, S. E., Juli an, J., Rohde, L. H., Karin, N. J., and Carson, D. D. (1996) J. Biol. Chem. 271, 11817-11823; Rohde, L. H., Julian, J., Babaknia, A., and Ca rson, D. D. (1996) J. Biol. Chem. 271, 11824-11830). In the current st udies, we have purified and characterized HIP from HEC cells, a human uterine epithelial cell line, as well as recombinant HIP from a bacter ial expression system. HIP supports attachment of the human trophoblas tic cell line, JAR, in a HS-dependent fashion. Predigestion of JAR cel ls with a mixture of heparitinases, but not chondroitinase AC, abolish ed cell attachment to HIP. In addition, JAR cell attachment to HIP is highly sensitive to HP inhibition and much more selective for HP/HS th an other glycosaminoglycans. Dermatan sulfate displays partial inhibit ory activity as well, consistent with the observation that chondroitin ase ABC digestion partially reduces JAR cell attachment to HIP. Solid- phase binding assays indicate HIP binds [H-3]HP with high affinity (ap parent K-D = 8 nM). Furthermore, HIP bound cell surface/extracellular matrix-associated HS, expressed by RL95 cells, a human uterine epithel ial cell line. Anti-HIP antibody generated against a synthetic peptide derived from a putative HP/HS-binding motif resident within HIP inhib ited about half of [H-3]HP binding to HIP, indicating that this domain is a functional HP-binding domain of HIP. Similarly, this same synthe tic peptide motif of HIP could block about 50% of [H-3]HP binding to H IP; however, this peptide almost completely inhibited cell attachment to HIP, suggesting a critical role, in this regard. Collectively, thes e results suggest that HIP can function as a HP/HS-binding cell-cell/c ell-matrix adhesion molecule.