title: Characterization of calcineurin from Hymenolepis microstoma and H. diminuta and its interaction with cyclosporin A.
abstract: The drug cyclosporin A (CsA) exerts its immunosuppressive action by binding to the cytosolic protein, cyclophilin (CyP) and, as a complex, binding to and inhibiting the calcium/calmodulin-dependent serine threonine phosphatase, calcineurin. It is unknown whether a similar mode of action occurs during the drug's antiparasite activity. Calmodulin-binding proteins from the helminth parasites Hymenolepis microstoma and H. diminuta were purified by affinity chromatography, yielding single polypeptide bands of 60000 M(r), according to SDS-PAGE. These proteins were tested for calcineurin activity by the dephosphorylation of the RII peptide (part of the catalytic subunit of cAMP-dependent protein kinase). Both proteins were calcium- and calmodulin-dependent and were inhibited by mammalian cyclophilin complexed with cyclosporin A (IC50 values of 0.75 microgram CyP for H. microstoma and 0.90 microgram CyP for H. diminuta). However, neither of the parasite calcineurins was inhibited by H. microstoma cyclophilin/CsA. These data suggest the anthelmintic mode of action of CsA in these helminth models does not involve the inhibition of a signal transduction pathway requiring interaction with calcineurin.
authors.affiliation: Department of Zoology, University of Aberdeen, Scotland. h.roberts@abdn.ac.uk
authors.forename: H C
authors.initials: HC
authors.lastname: Roberts
authors.forename: J M
authors.initials: JM
authors.lastname: Sternberg
authors.forename: L H
authors.initials: LH
authors.lastname: Chappell
mesh_terms: D000591:Amino Acid Isomerases / Q000378:metabolism / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D000871:Anthelmintics / Q000378:metabolism* / Q000494:pharmacology; D019703:Calcineurin; D002148:Calmodulin-Binding Proteins / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D016572:Cyclosporine / Q000378:metabolism* / Q000494:pharmacology; D006926:Hymenolepis / Q000737:chemistry* / Q000187:drug effects; D051379:Mice; D008969:Molecular Sequence Data; D010455:Peptides / Q000378:metabolism; D019696:Peptidylprolyl Isomerase; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D000871:Anthelmintics; D002148:Calmodulin-Binding Proteins; D002352:Carrier Proteins; D010455:Peptides; D016572:Cyclosporine; D017868:Cyclic AMP-Dependent Protein Kinases; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases; D000591:Amino Acid Isomerases; D019696:Peptidylprolyl Isomerase