Functional Consequences of Dual Oxidase-Thyroperoxidase Interaction at the Plasma Membrane

摘要

Context: Thyroperoxidase (TPO) and dual oxidase (DUOX) are present at the apical membrane of thyrocytes, where TPO catalyzes thyroid hormone biosynthesis in the presence of H_(2)O_(2) 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.Design: The functional consequences of DUOX-TPO interaction were studied by measuring extracellular H_(2)O_(2) 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 H_(2)O_(2) decreases both TPO and DUOX activities. We show that TPO presents a catalase-like effect that protects DUOX from inhibition by H_(2)O_(2). 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.Conclusion: The DUOX-TPO association at the plasma membrane is relevant for normal enzyme properties. Normally, TPO consumes H_(2)O_(2) 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.