title: Tissue plasminogen activator binding to the annexin II tail domain. Direct modulation by homocysteine.
abstract: Tissue plasminogen activator binds to endothelial cells via the calcium-regulated phospholipid-binding protein annexin II, an interaction that is inhibited by the prothrombotic amino acid homocysteine. We sought to identify the tissue plasminogen activator binding domain of annexin II and to determine the mechanism of its modulation by homocysteine. Tissue plasminogen activator binding to immobilized annexin II was inhibited by intact fluid phase annexin II but not by its "core" fragment (residues 25-339). Two overlapping "tail" peptides specifically blocked 65-75% of binding. Localization of the tissue plasminogen activator binding domain was confirmed upon specific inhibition by the hexapeptide LCKLSL (residues 7-12). Expressed C9G annexin II protein failed to support tissue plasminogen activator binding, while binding to C133G, C262G, and C335G was equivalent to that of wild type annexin II. Upon exposure to homocysteine, annexin II underwent a 135 +/- 4-Da increase in mass localizing specifically to Cys9 and a 60-66% loss in tissue plasminogen activator-binding capacity (I50 = 11 microM). Upon treatment of cultured endothelial cells with [35S]homocysteine, the dithiothreitol-sensitive label was recovered by immunoprecipitation with anti-annexin II IgG. These data provide a potential mechanism for the prothrombotic effect of homocysteine by demonstrating direct blockade of the tissue plasminogen activator binding domain of annexin II.
authors.affiliation: Department of Pediatrics, Cornell University Medical College, New York, New York 10021, USA. khajjar@cornell.mail.med.edu
authors.forename: K A
authors.initials: KA
authors.lastname: Hajjar
authors.forename: L
authors.initials: L
authors.lastname: Mauri
authors.forename: A T
authors.initials: AT
authors.lastname: Jacovina
authors.forename: F
authors.initials: F
authors.lastname: Zhong
authors.forename: U A
authors.initials: UA
authors.lastname: Mirza
authors.forename: J C
authors.initials: JC
authors.lastname: Padovan
authors.forename: B T
authors.initials: BT
authors.lastname: Chait
mesh_terms: D000595:Amino Acid Sequence; D017306:Annexin A2 / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D001665:Binding Sites; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D005260:Female; D006710:Homocysteine / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D010920:Placenta / Q000378:metabolism; D017354:Point Mutation; D011247:Pregnancy; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D018629:Spectrometry, Mass, Secondary Ion; D010959:Tissue Plasminogen Activator / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D014162:Transfection
chemical_list: D017306:Annexin A2; D010446:Peptide Fragments; D011994:Recombinant Proteins; D006710:Homocysteine; D010959:Tissue Plasminogen Activator