title: Analyses of cellular multimerin 1 receptors: in vitro evidence of binding mediated by alphaIIbbeta3 and alphavbeta3.
abstract: Multimerin 1 (MMRN1) is a large, soluble, polymeric, factor V binding protein and member of the EMILIN protein family. In vivo, MMRN1 is found in platelets, megakaryocytes, endothelium and extracellular matrix fibers, but not in plasma. To address the mechanism of MMRN1 binding to activated platelets and endothelial cells, we investigated the identity of the major MMRN1 receptors on these cells using wild-type and RGE-forms of recombinant MMRN1. Ligand capture, cell adhesion, ELISA and flow cytometry analyses of platelet-MMRN1 binding, indicated that MMRN1 binds to integrins alphaIIbbeta3 and alphavbeta3. Endothelial cell binding to MMRN1 was predominantly mediated by alphavbeta3 and did not require the MMRN1 RGD site or cellular activation. Like many other alphavbeta3 ligands, MMRN1 had the ability to support adhesion of additional cell types, including stimulated neutrophils. Expression studies, using a cell line capable of endothelial-like MMRN1 processing, indicated that MMRN1 adhesion to cellular receptors enhanced its extracellular matrix fiber assembly. These studies implicate integrin-mediated binding in MMRN1 attachment to cells and indicate that MMRN1 is a ligand for alphaIIbbeta3 and alphavbeta3.
authors.affiliation: Departments of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Frédérick
authors.initials: F
authors.lastname: Adam
authors.forename: Shilun
authors.initials: S
authors.lastname: Zheng
authors.forename: Nilesh
authors.initials: N
authors.lastname: Joshi
authors.forename: David S
authors.initials: DS
authors.lastname: Kelton
authors.forename: Amin
authors.initials: A
authors.lastname: Sandhu
authors.forename: Youko
authors.initials: Y
authors.lastname: Suehiro
authors.forename: Samira B
authors.initials: SB
authors.lastname: Jeimy
authors.forename: Aurelio V
authors.initials: AV
authors.lastname: Santos
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Massé
authors.forename: John G
authors.initials: JG
authors.lastname: Kelton
authors.forename: Elisabeth M
authors.initials: EM
authors.lastname: Cramer
authors.forename: Catherine P M
authors.initials: CP
authors.lastname: Hayward
mesh_terms: D001792:Blood Platelets / Q000378:metabolism*; D001798:Blood Proteins / Q000378:metabolism*; D002460:Cell Line; D042783:Endothelial Cells / Q000378:metabolism / Q000648:ultrastructure; D005109:Extracellular Matrix / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D066298:In Vitro Techniques; D039302:Integrin alphaVbeta3 / Q000378:metabolism*; D007668:Kidney / Q000166:cytology; D008024:Ligands; D008533:Megakaryocytes / Q000378:metabolism; D016253:Microscopy, Immunoelectron; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism*
chemical_list: D001798:Blood Proteins; D039302:Integrin alphaVbeta3; D008024:Ligands; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; C069282:multimerin