title: Interactions of plasminogen and tissue plasminogen activator (t-PA) with amphoterin. Enhancement of t-PA-catalyzed plasminogen activation by amphoterin.
abstract: The heparin-binding p30 protein amphoterin is proposed to mediate adhesive interactions of the advancing plasma membrane in migrating and differentiating cells. Since the NH2-terminal part of amphoterin is exceptionally rich in lysine residues, we have studied its interactions with plasminogen and tissue plasminogen activator (t-PA). On immunostaining of N18 neuroblastoma cells, amphoterin and t-PA showed a close co-localization in the filopodia of the leading membrane and in the substrate-attached material. In purified systems, both t-PA and plasminogen bound to immobilized amphoterin, and their binding was inhibited by the lysine analogue epsilon-aminocaproic acid. Plasminogen bound to immobilized amphoterin was activated by t-PA, and this resulted in effective degradation of the immobilized amphoterin. Correspondingly, amphoterin-bound t-PA activated plasminogen. In solution amphoterin accelerated t-PA-catalyzed plasminogen activation maximally 46-fold. The results indicate that t-PA and plasminogen form through their lysine-binding sites a complex with amphoterin, which results in acceleration of plasminogen activation and effective degradation of amphoterin. We suggest that local acceleration of t-PA-catalyzed plasminogen activation by amphoterin at the leading membrane enhances the penetration of growing cytoplasmic processes through extracellular materials during cell migration, differentiation and regeneration. The amphoterin-mediated adhesion at the leading membrane may be transient in nature, because the protein also enhances its own breakdown by accelerating t-PA-catalyzed plasminogen activation.
authors.affiliation: Department of Medical Chemistry, University of Helsinki, Finland.
authors.forename: J
authors.initials: J
authors.lastname: Parkkinen
authors.forename: H
authors.initials: H
authors.lastname: Rauvala
mesh_terms: D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism*; D002384:Catalysis; D004797:Enzyme-Linked Immunosorbent Assay; D005455:Fluorescent Antibody Technique; D024243:HMGB1 Protein; D006493:Heparin / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008239:Lysine / Q000378:metabolism; D009447:Neuroblastoma; D010958:Plasminogen / Q000378:metabolism*; D010959:Tissue Plasminogen Activator / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D002352:Carrier Proteins; D024243:HMGB1 Protein; D010958:Plasminogen; D006493:Heparin; D010959:Tissue Plasminogen Activator; D008239:Lysine