title: CD226 mediates platelet and megakaryocytic cell adhesion to vascular endothelial cells.
abstract: Platelet adhesion to vascular endothelial cells is a pathophysiologically relevant cell-to-cell interaction. However, the mechanisms underlying this cellular interaction are incompletely understood. In search of the ligand for CD226 adhesion molecule expressed on platelets, we found that human umbilical vein endothelial cells (HUVEC) express significant amount of putative CD226 ligand. We demonstrated that thrombin-activated, but not resting, platelets bind to intact HUVEC. Anti-CD226 monoclonal antibody specifically inhibited the binding, indicating that CD226 mediates the intercellular binding between thrombin-activated platelets and HUVEC. We also demonstrated that platelet activation with thrombin induces tyrosine phosphorylation of CD226 as well as CD226-mediated platelet adhesion. Moreover, experiments using mutant transfectants suggested that the tyrosine at residue 322 of CD226 plays an important role for its adhesive function. CD226 was also expressed on primary megakaryocytes and megakaryocytic cell lines. Anti-CD226 monoclonal antibody inhibited binding of megakaryocytic cell lines to HUVEC. Taken together, these results reveal a novel mechanism for adhesion of platelets and megakaryocytic cells to vascular endothelial cells.
authors.affiliation: Division of Hematology, Institute of Clinical Medicine and Department of Immunology, Institute of Basic Medical Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan. hkojima@md.tsukuba.ac.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kojima
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Kanada
authors.forename: Seiichi
authors.initials: S
authors.lastname: Shimizu
authors.forename: Emi
authors.initials: E
authors.lastname: Kasama
authors.forename: Kazuko
authors.initials: K
authors.lastname: Shibuya
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Nakauchi
authors.forename: Toshiro
authors.initials: T
authors.lastname: Nagasawa
authors.forename: Akira
authors.initials: A
authors.lastname: Shibuya
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000378:metabolism; D000945:Antigens, Differentiation, T-Lymphocyte / Q000096:biosynthesis* / Q000737:chemistry*; D001792:Blood Platelets / Q000378:metabolism*; D019556:COS Cells; D002448:Cell Adhesion; D002460:Cell Line; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology*; D005434:Flow Cytometry; D005452:Fluoresceins / Q000378:metabolism; D006801:Humans; D008024:Ligands; D008533:Megakaryocytes / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D009154:Mutation; D010766:Phosphorylation; D013917:Thrombin / Q000737:chemistry; D014162:Transfection; D014443:Tyrosine / Q000737:chemistry / Q000378:metabolism; D014471:Umbilical Veins / Q000166:cytology; D000098862:T Lineage-Specific Activation Antigen 1
chemical_list: D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D000098862:T Lineage-Specific Activation Antigen 1; D005452:Fluoresceins; D008024:Ligands; D014443:Tyrosine; D013917:Thrombin; C007740:fluorexon