title: Protease nexin-2/Amyloid beta-protein precursor regulates factor VIIa and the factor VIIa-tissue factor complex.
abstract: Protease nexin-2/amyloid beta-protein precursor (PN-2/AbetaPP) and its Kunitz protease inhibitory (KPI) domain were characterized as inhibitors of factor VIIa (FVIIa) and factor VIIa-tissue factor complex (FVIIa-TF). PN-2/AbetaPP and KPI domain inhibited FVIIa with an apparent K(i) of 1.1+/-0.2x 10(-7) M and 1.5+/-0.1x10(-7) M, respectively. When soluble tissue factor (TF(1-219)) was present, there was increased FVIIa inhibition by PN-2/AbetaPP or KPI domain (K(i)=7.8+/-0.3x10(-8) M and 6.8+/-0.6x10(-8) M, respectively). When relipidated tissue factor (TF(1-243)) was present, the K(i) of FVIIa inhibition by PN-2/AbetaPP increased 4.7-fold further. PN-2/AbetaPP complexed with FVIIa, as shown on gel filtration and solid phase binding assay. The apparent second-order rate constant of inhibition of FVIIa by PN-2/AbetaPP in the absence of TF(1-219) was less than that of the FVIIa-TF(1-219) complex. Antithrombin in the absence of TF(1-219) also had a lower apparent second-order rate constant of inhibition than in its presence. In a mixture that included FVIIa, relipidated TF(1-243) and factor X, PN-2/AbetaPP or KPI domain had an IC(50) at 65 and 250 nM, respectively; antithrombin and heparin (1 U/mL) had an IC(50) of 12.8 nM. These data indicate that tissue factor promoted the inhibition of FVIIa by PN-2/AbetaPP or KPI domain, but antithrombin was a better inhibitor of soluble FVIIa-TF in extrinsic tenase.
authors.affiliation: Department of Internal Medicine, Division of Hematology and Oncology, University of Michigan, Ann Arbor, MI 48109-0724, USA.
authors.forename: F
authors.initials: F
authors.lastname: Mahdi
authors.forename: A
authors.initials: A
authors.lastname: Rehemtulla
authors.forename: W E
authors.initials: WE
authors.lastname: Van Nostrand
authors.forename: S P
authors.initials: SP
authors.lastname: Bajaj
authors.forename: A H
authors.initials: AH
authors.lastname: Schmaier
mesh_terms: D016564:Amyloid beta-Protein Precursor / Q000494:pharmacology*; D000925:Anticoagulants / Q000494:pharmacology; D000990:Antithrombin III / Q000494:pharmacology; D002352:Carrier Proteins / Q000494:pharmacology*; D002850:Chromatography, Gel; D015942:Factor VIIa / Q000037:antagonists & inhibitors* / Q000378:metabolism; D005170:Factor X / Q000378:metabolism; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D046911:Macromolecular Substances; D058255:Protease Nexins; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface; D012995:Solubility; D013329:Structure-Activity Relationship; D013925:Thromboplastin / Q000378:metabolism*
chemical_list: C545487:APP protein, human; D016564:Amyloid beta-Protein Precursor; D000925:Anticoagulants; D002352:Carrier Proteins; D046911:Macromolecular Substances; D058255:Protease Nexins; D011956:Receptors, Cell Surface; D000990:Antithrombin III; D005170:Factor X; D006493:Heparin; D013925:Thromboplastin; D015942:Factor VIIa