Functional consequences of dual oxidase-thyroperoxidase interaction at the plasma membrane.
BACKGROUND
Thyroperoxidase (TPO) and dual oxidase (DUOX) are present at the apical membrane of thyrocytes, where TPO catalyzes thyroid hormone biosynthesis in the presence of H2O2 produced by DUOX. Both enzymes are colocalized and associated, but the consequences of this interaction remain obscure.


OBJECTIVE
The objective of this study was to evaluate the functional consequences of TPO-DUOX interaction at the plasma membrane.


METHODS
The functional consequences of DUOX-TPO interaction were studied by measuring extracellular H2O2 concentration and TPO activity in a heterologous system. For this purpose, HEK293 cells were transiently transfected with a combination of human TPO with human DUOX1 or DUOX2 in the presence of their respective maturation factors, DUOXA1 or DUOXA2. The effect of human DUOX2 mutants in which cysteine residues in the N-terminal domain were replaced by glycines was also analyzed.


RESULTS
We observed that production of H2O2 decreases both TPO and DUOX activities. We show that TPO presents a catalase-like effect that protects DUOX from inhibition by H2O2. This catalase-like effect depends on the association between both enzymes, which probably occurs through the DUOX peroxidase-like domain because this effect was not observed with human DUOX2 mutants.


CONCLUSIONS
The DUOX-TPO association at the plasma membrane is relevant for normal enzyme properties. Normally, TPO consumes H2O2 produced by DUOX, decreasing the availability of this substance at the apical membrane of thyrocytes and, in turn, probably decreasing the oxidative damage of macromolecules.
Fortunato
Rodrigo Soares
RS
Instituto de Biofisica Carlos Chagas Filho, CCS-Bloc G-Cidade Universitaria, Rio de Janeiro, Brazil.
Lima de Souza
Elaine Cristina
EC
Ameziane-el Hassani
Rabii
R
Boufraqech
Myriem
M
Weyemi
Urbain
U
Talbot
Monique
M
Lagente-Chevallier
Odile
O
de Carvalho
Denise Pires
DP
Bidart
Jean-Michel
JM
Schlumberger
Martin
M
Dupuy
Corinne
C
D001324:Autoantigens / Q000235:genetics / Q000378:metabolism*; D002374:Catalase / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology*; D000074623:Dual Oxidases; D005434:Flow Cytometry; D015971:Gene Expression Regulation, Enzymologic; D057809:HEK293 Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D007453:Iodide Peroxidase / Q000235:genetics / Q000378:metabolism*; D033862:Iron-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D007668:Kidney / Q000201:enzymology; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism*; D016376:Oligonucleotides, Antisense; D010088:Oxidoreductases / Q000378:metabolism*; D014162:Transfection
D001324:Autoantigens; D033862:Iron-Binding Proteins; D016376:Oligonucleotides, Antisense; D006861:Hydrogen Peroxide; D010088:Oxidoreductases; D000074623:Dual Oxidases; D002374:Catalase; C056658:TPO protein, human; D007453:Iodide Peroxidase; D019255:NADPH Oxidases; C431515:DUOX2 protein, human