A peptide sequence of heparin/heparan sulfate (HP/HS)-interacting protein supports selective, high affinity binding of HP/HS and cell attachment.

We previously have identified a novel cell surface heparan sulfate/heparin (HS/HP)-interacting protein (HIP) found in human uterine epithelia and a variety of other human epithelial and endothelial cells and cell lines (Liu, S., Smith, S. E., Julian, 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 Carson, D. D. (1996) J. Biol. Chem. 271, 11824-11830). The amino acid sequence predicted for HIP revealed a potential HS/HP-binding motif. In the present studies, a synthetic peptide corresponding to this putative HS/HP-binding motif, HIP peptide, was synthesized and examined with regard to its HS/HP binding and cell attachment promoting activity. Results using solid phase binding assays demonstrate that HIP peptide binds HS/HP with high selectivity and has high affinity for bulk HP (50% saturation congruent with 300 nM) and even higher affinity for a subset of polysaccharides found in commercial [3H]HP (half-saturation congruent with 10 nM). Moreover, HIP peptide binds subsets of cell and extracellular matrix-associated HS and dermatan sulfate expressed by RL95 cells, a human uterine adenocarcinoma cell line. HIP peptide also binds a similar fraction of HS as well as dermatan sulfate expressed by JAR cells, a human choriocarcinoma cell line. In contrast to binding of cell- or extracellular matrix-associated HS, HIP peptide does not bind secreted or released forms of HS or DS from either RL95 or JAR cells to a significant extent. HS species that bind to HIP peptide are generally larger, have a higher negative charge density, and have a larger proportion of di- and trisulfated disaccharide units than HS species that do not bind to HIP peptide, demonstrating structural differences among these polysaccharides. This same peptide supports HS-dependent JAR cell attachment. Collectively, these data demonstrate that a linear peptide sequence found within HIP can account, at least in part, for the HS/HP binding and cell adhesion promoting activities of this protein.