title: Localization and functional analysis of the cytosolic and extracellular CuZn superoxide dismutases in the human parasitic nematode Onchocerca volvulus.
abstract: This study describes the histological localization of two CuZn superoxide dismutases (SOD1 and SOD2) in the parasitic nematode Onchocerca volvulus, and a functional characterization of the 'extracellular' form of this enzyme (SOD2) which provides evidence that it is involved in the defense against environmental superoxide anion radicals. These essential enzymes are detected in larval and adult stages of the parasite, determined at the mRNA and protein levels by in situ hybridization and immunolocalization studies. These proteins are distributed throughout the worm, at various concentrations with particularly high levels produced in the hypodermis. In vitro maintenance of parasites indicated that SOD2 was secreted outside the parasite into the medium. Baculovirus constructs designed to test the ability of the SOD2 hydrophobic N-terminal region to function in processing and secretion confirmed the ability of this polypeptide sequence to direct the secretion of a marker protein, as well as of the mature SOD2 enzyme. Analyses of the native, mature SOD2 enzyme molecular mass, and the primary and quaternary structure, indicate that unlike other extracellular SODs, the SOD2 is active as a non-glycosylated dimer, rather than as a tetrameric glycoprotein. The detection of SOD2 outside of the parasite maintained in vitro, and the confirmation that the SOD2 is a secreted enzyme, indicate that this enzyme plays a role in the interactive biology of parasitic nematodes with their hosts.
authors.affiliation: Department of Biochemistry, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Henkle-Dührsen
authors.forename: R S
authors.initials: RS
authors.lastname: Tuan
authors.forename: G
authors.initials: G
authors.lastname: Wildenburg
authors.forename: M L
authors.initials: ML
authors.lastname: Eschbach
authors.forename: W
authors.initials: W
authors.lastname: Tawe
authors.forename: P
authors.initials: P
authors.lastname: Zipfel
authors.forename: R D
authors.initials: RD
authors.lastname: Walter
mesh_terms: D000818:Animals; D003600:Cytosol / Q000201:enzymology; D004926:Escherichia coli / Q000235:genetics; D005110:Extracellular Space / Q000201:enzymology; D005260:Female; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008297:Male; D017181:Onchocerca volvulus / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D018510:RNA, Helminth / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*
chemical_list: D007527:Isoenzymes; D018510:RNA, Helminth; D012333:RNA, Messenger; D011994:Recombinant Proteins; D013482:Superoxide Dismutase