title: Neospora caninum: functional inhibition of protein disulfide isomerase by the broad-spectrum anti-parasitic drug nitazoxanide and other thiazolides.
abstract: Nitazoxanide (NTZ) and several NTZ-derivatives (thiazolides) have been shown to exhibit considerable anti-Neospora caninum tachyzoite activity in vitro. We coupled tizoxanide (TIZ), the deacetylated metabolite, to epoxy-agarose-resin and performed affinity chromatography with N. caninum tachyzoite extracts. Two main protein bands of 52 and 43kDa were isolated. The 52kDa protein was readily recognized by antibodies directed against NcPDI, and mass spectrometry confirmed its identity. Poly-histidine-tagged NcPDI-cDNA was expressed in Escherichia coli and recombinant NcPDI (recNcPDI) was purified by Co2+-affinity chromatography. By applying an enzyme assay based on the measurement of insulin crosslinking activity, recNcPDI exhibited properties reminiscent for PDIs, and its activity was impaired upon the addition of classical PDI inhibitors such as bacitracin (1-2mM), para-chloromercuribenzoic acid (0.1-1mM) and tocinoic acid (0.1-1mM). RecNcPDI-mediated insulin crosslinking was inhibited by NTZ (5-100 microM) in a dose-dependent manner. In addition, the enzymatic activity of recNcPDI was inhibited by those thiazolides that also affected parasite proliferation. Thus, thiazolides readily interfere with NcPDI, and possibly also with PDIs from other microorganisms susceptible to thiazolides.
authors.affiliation: Institute of Parasitology, University of Berne, Länggass-Strasse 122, CH-3012 Berne, Switzerland. joachim.mueller@ipa.unibe.ch
authors.forename: Joachim
authors.initials: J
authors.lastname: Müller
authors.forename: Arunasalam
authors.initials: A
authors.lastname: Naguleswaran
authors.forename: Norbert
authors.initials: N
authors.lastname: Müller
authors.forename: Andrew
authors.initials: A
authors.lastname: Hemphill
mesh_terms: D000818:Animals; D000977:Antiparasitic Agents / Q000494:pharmacology*; D002522:Chlorocebus aethiops; D002846:Chromatography, Affinity; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D015151:Immunoblotting; D018688:Neospora / Q000187:drug effects* / Q000201:enzymology; D009574:Nitro Compounds; D019704:Protein Disulfide-Isomerases / Q000037:antagonists & inhibitors* / Q000235:genetics; D051381:Rats; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013844:Thiazoles / Q000737:chemistry / Q000494:pharmacology*; D014709:Vero Cells
chemical_list: D000977:Antiparasitic Agents; D009574:Nitro Compounds; D011994:Recombinant Proteins; D013844:Thiazoles; D019704:Protein Disulfide-Isomerases; C041747:nitazoxanide