GPX5 orthologs of the mouse epididymis-restricted and sperm-bound selenium-independent glutathione peroxidase are not expressed with the same quantitative and spatial characteristics in large domestic animals

We report here on the cloning of cDNAs coding bovine and equine orthologs of mouse epididymis-restricted and sperm-bound glutathione peroxidase 5 (GPX5), a selenium-independent member of the multigenic GPX family in mammals. The complete sequence of bovine GPX5 as well as a partial sequence of the equine GPX5 were characterized, conceptually translated and aligned with other known mammalian GPX5 proteins. Using Northern blotting assays, we show that the level of expression of GPX5 is high in bovine but low in equine and that in both species the regionalization of GPX5 expression in epididymis is not totally identical to what was reported for rodent mouse GPX5. An antibody was produced against GPX5 and used in Western blot assays as well as in immunohistochemistry assays on bovine epididymis sections. It shows that the protein is essentially present in the cytoplasmic compartment of the caput segment 2 epithelium of the bovine epididymis. Unlike in the mouse model, bovine GPX5 seems to be poorly secreted and does not seem to be present on cauda epididymal spermatozoa.