title: High molecular weight kininogen regulates platelet-leukocyte interactions by bridging Mac-1 and glycoprotein Ib.
abstract: Leukocyte-platelet interaction is important in mediating leukocyte adhesion to a thrombus and leukocyte recruitment to a site of vascular injury. This interaction is mediated at least in part by the beta2-integrin Mac-1 (CD11b/CD18) and its counter-receptor on platelets, glycoprotein Ibalpha (GPIbalpha). High molecular weight kininogen (HK) was previously shown to interact with both GPIbalpha and Mac-1 through its domains 3 and 5, respectively. In this study we investigated the ability of HK to interfere with the leukocyte-platelet interaction. In a purified system, HK binding to GPIbalpha was inhibited by HK domain 3 and the monoclonal antibody (mAb) SZ2, directed against the epitope 269-282 of GPIbalpha, whereas mAb AP1, directed to the region 201-268 of GPIbalpha had no effect. In contrast, mAb AP1 inhibited the Mac-1-GPIbalpha interaction. Binding of GPIbalpha to Mac-1 was enhanced 2-fold by HK. This effect of HK was abrogated in the presence of HK domains 3 or 5 or peptides from the 475-497 region of the carboxyl terminus of domain 5 as well as in the presence of mAb SZ2 but not mAb AP1. Whereas no difference in the affinity of the Mac-1-GPIbalpha interaction was observed in the absence or presence of HK, maximal binding of GPIbalpha to Mac-1 doubled in the presence of HK. Moreover, HK/HKa increased the Mac-1-dependent adhesion of myelomonocytic U937 cells and K562 cells transfected with Mac-1 to immobilized GPIbalpha or to GPIbalpha-transfected Chinese hamster ovary cells. Finally, Mac-1-dependent adhesion of neutrophils to surface-adherent platelets was enhanced by HK. Thus, HK can bridge leukocytes with platelets by interacting via its domain 3 with GPIbalpha and via its domain 5 with Mac-1 thereby augmenting the Mac-1-GPIbalpha interaction. These distinct molecular interactions of HK with leukocytes and platelets contribute to the regulation of the adhesive behavior of vascular cells and provide novel molecular targets for reducing atherothrombotic pathologies.
authors.affiliation: Department of Internal Medicine I, University Heidelberg, D-69115 Heidelberg, Germany. triantafyllos.chavakis@med.uni-heidelberg.de
authors.forename: Triantafyllos
authors.initials: T
authors.lastname: Chavakis
authors.forename: Sentot
authors.initials: S
authors.lastname: Santoso
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Clemetson
authors.forename: Ulrich J H
authors.initials: UJ
authors.lastname: Sachs
authors.forename: Irma
authors.initials: I
authors.lastname: Isordia-Salas
authors.forename: Robin A
authors.initials: RA
authors.lastname: Pixley
authors.forename: Peter P
authors.initials: PP
authors.lastname: Nawroth
authors.forename: Robert W
authors.initials: RW
authors.lastname: Colman
authors.forename: Klaus T
authors.initials: KT
authors.lastname: Preissner
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D001665:Binding Sites; D001792:Blood Platelets / Q000378:metabolism*; D016466:CHO Cells; D002448:Cell Adhesion; D002450:Cell Communication; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes; D005434:Flow Cytometry; D006801:Humans; D020014:K562 Cells; D019679:Kininogen, High-Molecular-Weight / Q000378:metabolism* / Q000502:physiology*; D007962:Leukocytes / Q000378:metabolism*; D016177:Macrophage-1 Antigen / Q000378:metabolism*; D009504:Neutrophils / Q000378:metabolism; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D014162:Transfection; D020298:U937 Cells
chemical_list: D000911:Antibodies, Monoclonal; D000939:Epitopes; D019679:Kininogen, High-Molecular-Weight; D016177:Macrophage-1 Antigen; D019038:Platelet Glycoprotein GPIb-IX Complex; C023592:glycocalicin