title: The S100 family heterodimer, MRP-8/14, binds with high affinity to heparin and heparan sulfate glycosaminoglycans on endothelial cells.
abstract: The S100 family proteins MRP-8 (S100A8) and MRP-14 (S100A9) form a heterodimer that is abundantly expressed in neutrophils, monocytes, and some secretory epithelia. In inflamed tissues, the MRP-8/14 complex is deposited onto the endothelium of venules associated with extravasating leukocytes. To explore the receptor interactions of MRP-8/14, we use a model system in which the purified MRP-8/14 complex binds to the cell surface of an endothelial cell line, HMEC-1. This interaction is mediated by the MRP-14 subunit and is mirrored by recombinant MRP-14 alone. The cell surface binding of MRP-14 was blocked by heparin, heparan sulfate, and chondroitin sulfate B, and the binding sites were sensitive to heparinase I and trypsin treatment but not to chondroitinase ABC. Furthermore MRP-8/14 and MRP-14 did not bind to a glycosaminoglycan-minus cell line. MRP-14 has a high affinity for heparin (K(d) = 6.1 +/- 3.4 nm), and this interaction mimicked that with the endothelial cells. We therefore conclude that the MRP-8/14 complex binds to endothelial cells via the MRP-14 subunit interacting chiefly with heparan sulfate proteoglycans. CD36 and RAGE, two other putative receptors for MRP-8/14, were not expressed by HMEC-1 cells. This binding activity may explain the immobilization of the MRP-8/14 complex on endothelium that is observed in vivo.
authors.affiliation: Leukocyte Adhesion Laboratory, Imperial Cancer Research Fund and the in Situ Hybridization Service and Histopathology Unit, 44 Lincoln's Inn Fields, London WC2A 3PX, United Kingdom.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Robinson
authors.forename: Philippe
authors.initials: P
authors.lastname: Tessier
authors.forename: Richard
authors.initials: R
authors.lastname: Poulsom
authors.forename: Nancy
authors.initials: N
authors.lastname: Hogg
mesh_terms: D000818:Animals; D000943:Antigens, Differentiation / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D016466:CHO Cells; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D040501:Calgranulin A; D040502:Calgranulin B; D002413:Cations, Divalent / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D006224:Cricetinae; D016264:Dextran Sulfate / Q000494:pharmacology; D003911:Dextrans / Q000494:pharmacology; D019281:Dimerization; D004730:Endothelium, Vascular / Q000378:metabolism*; D006493:Heparin / Q000378:metabolism*; D006497:Heparan Sulfate / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D007700:Kinetics; D009504:Neutrophils / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D009418:S100 Proteins / Q000737:chemistry / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology; D014162:Transfection
chemical_list: D000943:Antigens, Differentiation; D002135:Calcium-Binding Proteins; D040501:Calgranulin A; D040502:Calgranulin B; D002413:Cations, Divalent; D016264:Dextran Sulfate; D003911:Dextrans; D006493:Heparin; D006497:Heparan Sulfate; D011994:Recombinant Proteins; D009418:S100 Proteins; D012965:Sodium Chloride