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/hep arin (HS/HP)-interacting protein (HIP) found in human uterine epitheli a and a variety of other human epithelial and endothelial cells and ce ll 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 peptid e, was synthesized and examined with regard to its HS/HP binding and c ell attachment promoting activity. Results using solid phase binding a ssays demonstrate that HIP peptide binds HS/HP with high selectivity a nd has high affinity for bulk HP (50% saturation congruent to 300 nm) and even higher affinity for a subset of polysaccharides found in comm ercial [H-3]HP (half-saturation congruent to 10 nM). Moreover, HIP pep tide binds subsets of cell and extracellular matrix-associated HS and dermatan sulfate expressed by RL95 cells, a human uterine adenocarcino ma cell line. HIP peptide also binds a similar fraction of HS as well as dermatan sulfate expressed by JAR cells, a human choriocarcinoma ce ll line. In contrast to binding of cell-or extracellular matrix-associ ated 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 dis accharide units than HS species that do not bind to HIP peptide, demon strating structural differences among these polysaccharides. This same peptide supports MS-dependent JAR cell attachment. Collectively, thes e data demonstrate that a linear peptide sequence-found within HIP can account, at least in part, for the HS/HP binding and cell adhesion pr omoting activities of this protein.