title: Characterization of a plasminogen activator produced by Acanthamoeba castellanii.
abstract: Serine proteases play an important role in a diverse array of biological processes, including embryogenesis, metastasis, angiogenesis, thrombolysis and tissue invasion by certain parasites. The latter observation prompted us to explore the possibility that the tissue-invasive ocular parasite Acanthamoeba castellanii elaborates one or more serine proteases. Acanthamoeba sp. are pathogenic free-living amoebae that can produce an invasive, blinding inflammatory disease of the cornea, termed Acanthamoeba keratitis. The present study reports the preliminary purification and characterization of a novel plasminogen activator from an ocular isolate of A. castellanii. The parasite-derived enzyme has a molecular mass of approx. 40 kDa and produces a single band of lysis on fibrinogen-agarose zymographs. Activity of the enzyme is completely inhibited by treatment with diisopropylfluorophosphate, indicating that it is a serine protease. The parasite-derived serine protease is not inhibited by amiloride which is a strong inhibitor of urokinase-type plasminogen activator. Additionally, the enzyme is not inhibited by plasminogen activator inhibitor-1 which is the primary physiological inhibitor of both urokinase and tissue-type plasminogen activator. It does not cross-react with antibodies specific for human urokinase or tissue-type plasminogen activator. The parasite-derived enzyme activates plasminogen from several mammalian species, including human, cow and pig. Thus, it is possible that this parasite-derived serine protease contributes to the pathogenesis of Acanthamoeba keratitis.
authors.affiliation: Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas 75235-9057, USA.
authors.forename: M M
authors.initials: MM
authors.lastname: Mitra
authors.forename: H
authors.initials: H
authors.lastname: Alizadeh
authors.forename: R D
authors.initials: RD
authors.lastname: Gerard
authors.forename: J Y
authors.initials: JY
authors.lastname: Niederkorn
mesh_terms: D000048:Acanthamoeba / Q000201:enzymology* / Q000302:isolation & purification / Q000472:pathogenicity; D015823:Acanthamoeba Keratitis / Q000469:parasitology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D003429:Cross Reactions; D006801:Humans; D007531:Isoflurophate / Q000494:pharmacology; D008970:Molecular Weight; D017395:Plasminogen Activator Inhibitor 1 / Q000494:pharmacology; D010960:Plasminogen Activators / Q000276:immunology / Q000302:isolation & purification* / Q000378:metabolism; D015849:Plasminogen Inactivators / Q000494:pharmacology; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology
chemical_list: D017395:Plasminogen Activator Inhibitor 1; D015849:Plasminogen Inactivators; D015842:Serine Proteinase Inhibitors; D007531:Isoflurophate; D000584:Amiloride; D010960:Plasminogen Activators