Cell-specific localization of the sulphydryl oxidase QSOX in rat peripheral tissues

Abstract

Rat quiescin/sulphydryl oxidase (rQSOX) introduces disulphide bridges into peptides and proteins with the reduction of molecular oxygen to hydrogen peroxide. Its occurrence has been previously highlighted in a wide range of organs by reverse transcription-polymerase chain reaction (RT-PCR) and Northern blot analyses, methods that have provided information concerning its expression in whole organs but that do not reveal the cell types expressing this enzyme. In this report, in addition to RT-PCR and Western blot experiments, the cell-specific localization of rQSOX has been investigated in a wide range of male and female adult rat tissues by using in situ hybridization and immunohistochemistry. Labelling was detected in most organs and systems including the immune, endocrine and reproductive systems, the respiratory, digestive and urinary tracts and the skin. No labelling was observed in the heart, blood vessel endothelium, liver or smooth and skeletal muscles. rQSOX expression was mainly localized in epithelial cells specialized in secretion, strengthening the hypothesis that QSOX enzymes play an important role in the mechanism of secretion, notably in the folding of secreted proteins. The intracellular patterns of immunolabelling indicate that the protein usually follows the secretory pathway, which is in accordance with its secreted nature and its presumed involvement in the elaboration of the extracellular matrix. In seminiferous tubules, where a high level of expression was noticed, QSOX might play an important physiological role in sperm function and serve as a marker for the diagnosis of male infertility.

Tissue distribution of quiescin Q6/sulfhydryl oxidase (QSOX) in developing mouse

“…Photomicrographs confirmed that the antibody strongly stained the apical surface of epithelial cells from this tissue (Fig. 1b), in agreement with the expected localization of QSOX in adult secretory tissues (Chang and Zirkin 1978;Benayoun et al 2001;Tury et al 2006). These results clearly demonstrate that this antibody is a specific reagent for QSOX studies.…”

“…QSOX distribution has already been intensively investigated in other environments, such as rat ) and guinea pig (Amiot et al 2004) central nervous system, rat peripheral tissues (Tury et al 2006) Fig. 2 Representative immunohistochemical localization of QSOX in E 13.5 mouse fetal tissues.…”

“…An increasing amount of catalysis data was provided by Thorpe's group for the avian QSOX (Hoober et al 1996(Hoober et al , 1999bHoober and Thorpe 1999;Raje and Thorpe 2003). In addition to egg white (Hoober et al 1996) and male reproductive tract (Chang and Zirkin 1978;Ostrowski et al 1979;Benayoun et al 2001), QSOX has already been found in diverse tissues, such as endometrium (Musard et al 2001), nervous system (Mairet-Coello et al 2002, epidermis (Matsuba et al 2002), neuroblastoma (Wittke et al 2003), fetal serum (Zanata et al 2005), and several other secreting and non-secreting tissues (Coppock and Thorpe 2006;Tury et al 2006). Two splice variants of the QSOX gene have been reported in human, mouse (Coppock and Thorpe 2006) and rat (Radom et al 2006) tissues, in addition to the neuroblastoma QSOXN gene (Wittke et al 2003).…”

Generating Disulfides in Multicellular Organisms: Emerging Roles for a New Flavoprotein Family

“…QSOX1 was initially identified as a protein secreted from quiescent human fibroblasts (20) and is present in chicken egg white (36), mammalian seminal fluid (26,34,37), Chinese hamster ovary epithelial cell supernatants (26), and blood serum (38). However, QSOXs have also been found in the ER, Golgi, and secretory granules and are located at the cell surface (27-29, 35, 39).…”

“…Another clue comes from the relative abundance of QSOX1 in cell types with a heavy secretory load or those that accumulate protein disulfides intracellularly as a result of terminal differentiation (27,28,34).…”