title: Identification of the maturation factor for dual oxidase. Evolution of an eukaryotic operon equivalent.
abstract: Dual oxidase 2 (DUOX2), an NADPH:O(2) oxidoreductase flavoprotein, is a component of the thyroid H(2)O(2) generator crucial for hormone synthesis at the apical membrane. Mutations in DUOX2 produce congenital hypothyroidism in humans. However, no functional DUOX-based NADPH oxidase has ever been reconstituted at the plasma membrane of transfected cells. It has been proposed that DUOX retention in the endoplasmatic reticulum (ER) of heterologous systems is due to the lack of an unidentified component required for functional maturation of the enzyme. By data mining of a massively parallel signature sequencing tissue expression data base, we identified an uncharacterized gene named DUOX maturation factor (DUOXA2) arranged head-to-head to and co-expressed with DUOX2. A paralog (DUOXA1) was similarly linked to DUOX1. The genomic rearrangement leading to linkage of ancient DUOX and DUOXA genes could be traced back before the divergence of echinoderms. We demonstrate that co-expression of DUOXA2, an ER-resident transmembrane protein, allows ER-to-Golgi transition, maturation, and translocation to the plasma membrane of functional DUOX2 in a heterologous system. The identification of DUOXA genes has important implications for studies of the molecular mechanisms controlling DUOX expression and the molecular genetics of congenital hypothyroidism.
authors.affiliation: Department of Medicine, University of Chicago, Illinois 60637, USA. hgrasber@uchicago.edu
authors.forename: Helmut
authors.initials: H
authors.lastname: Grasberger
authors.forename: Samuel
authors.initials: S
authors.lastname: Refetoff
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003409:Congenital Hypothyroidism / Q000235:genetics; D006224:Cricetinae; D030541:Databases, Genetic; D000074623:Dual Oxidases; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004789:Enzyme Activation / Q000235:genetics; D019143:Evolution, Molecular; D005420:Flavoproteins / Q000235:genetics* / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D020022:Genetic Predisposition to Disease; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D019255:NADPH Oxidases / Q000235:genetics* / Q000378:metabolism; D009876:Operon; D009928:Organ Specificity; D020539:Sequence Analysis, Protein
chemical_list: C513411:DUOXA2 protein, human; D005420:Flavoproteins; D008565:Membrane Proteins; D000074623:Dual Oxidases; D019255:NADPH Oxidases; C431515:DUOX2 protein, human