Identification of a truncated dual oxidase 2 (DUOX2) messenger ribonucleic
acid (mRNA) in two rat thyroid cell lines. Insulin and forskolin regulation of
DUOX2 mRNA levels in FRTL-5 cells and porcine thyrocytes.
Morand S, Dos Santos OF, Ohayon R, Kaniewski J, Noel-Hudson MS, Virion A,
Dupuy C.
Unite 486, Institut National de la Sante et de la Recherche Medicale, Universite
Paris 11, Faculte de Pharmacie, 92296 Chatenay-Malabry Cedex, France.
The Duox2 flavoprotein is strongly expressed in the thyroid gland, where it
plays a critical role in the synthesis of thyroid hormones likely by providing
thyroperoxidase with H(2)O(2). A truncated DUOX2 mRNA was isolated from the rat
thyroid cell line FRTL-5. The cDNA sequence predicted an open reading frame of
1458 bp, encoding a polypeptide of 486 amino acids corresponding to the carboxyl
fragment of the Duox2 flavoprotein. The truncated form of DUOX2 mRNA, expressed
in another rat thyroid cell line, the PC Cl3 cell line, was absent from Fischer
rat thyroid glands. Although it was expressed in both cell lines to a greater
extent than normal mRNA, it failed to support protein synthesis in an in vitro
translation system. Insulin increased the levels of both normal and truncated
DUOX2 mRNA in FRTL-5 cells grown in TSH-free medium containing a low
concentration of serum. The stimulating effect of insulin on DUOX2 mRNA
expression was reproduced in pig thyroid follicles in primary culture. The
presence of insulin in the culture medium converted forskolin from a stimulator
to an inhibitor in FRTL-5 cells maintained in low serum conditions, but not in
porcine thyrocytes in primary culture.