title: Phorbol ester enhances integrin alpha IIb beta 3-dependent adhesion of human erythroleukemic cells to activation-dependent monoclonal antibodies.
abstract: Following platelet stimulation by agonists, integrin-alpha IIb beta 3 (or glycoprotein IIb-IIIa) is converted to an activated state that can bind soluble fibrinogen and mediate platelet aggregation. However, little is known about modulation of alpha IIb beta 3 in cell lines. In the present study, we show that agonist stimulation modulates alpha IIb beta 3-dependent adhesive properties of a human erythroleukemic (HEL) cell line. Brief treatment with phorbol 12-myristate 13-acetate (PMA) caused a significant increase in HEL cell adhesion to monoclonal antibodies (MoAbs) specific for activated alpha IIb beta 3 (PAC1 or pl-55). This adhesion was inhibited by blocking MoAbs or peptides specific for alpha IIb beta 3, but not by anti-Fc gamma receptor-specific MoAb. Similarly, PMA enhanced HEL cell adhesion to immobilized fibrinogen by 10-fold. However, the activation-dependent ligands in solution (ie, PAC1, pl-55, or fibrinogen) did not inhibit the enhanced HEL cell adhesion to immobilized MoAbs PAC1 or pl-55 after PMA treatment. Thus, PMA may increase alpha IIb beta 3-dependent adhesion to immobilized activation-dependent antibodies and fibrinogen by increasing the local concentration of alpha IIb beta 3 to participate in low-affinity interactions, resulting in an increased avidity, changing the affinity state of alpha IIb beta 3, or both.
authors.affiliation: Department of Pharmacology, University of North Carolina at Chapel Hill 27599-7365, USA.
authors.forename: C
authors.initials: C
authors.lastname: Boudignon-Proudhon
authors.forename: P M
authors.initials: PM
authors.lastname: Patel
authors.forename: L V
authors.initials: LV
authors.lastname: Parise
mesh_terms: D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000378:metabolism*; D000937:Antigen-Antibody Reactions; D002448:Cell Adhesion / Q000187:drug effects; D005340:Fibrinogen / Q000378:metabolism*; D006801:Humans; D004915:Leukemia, Erythroblastic, Acute / Q000473:pathology*; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000276:immunology / Q000378:metabolism*; D014411:Neoplastic Stem Cells / Q000187:drug effects* / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000276:immunology / Q000378:metabolism*; D011485:Protein Binding; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D009363:Neoplasm Proteins; D010446:Peptide Fragments; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D005340:Fibrinogen; D013755:Tetradecanoylphorbol Acetate