La castration induit des changements de l’expression et de la distribution des récepteurs dans l’épididyme chez le rat. Implications dans la écrétion de la cathespine D

AGUILERA AC; CARVELLI L; BANNOUD N; MALOSSI AE; MIGUEL A. SOSA

Aguas de Sao Pedro

Conferencia; Fifth International Conference on the Epididymis; 2010

Introduction: It is well known that the epididymal epithelium (which is stimulated by steroid hormones) is involved in the process of sperm maturation through its secretory activity. High concentrations of some acid hydrolases have been found in the epididymal lumen, an intriguing fact considering that these enzymes should be confined to an intracellular compartment. Moreover, it was confirmed that some enzymes are secreted into the epididymal lumen in response to androgenic hormones. In other cells and tissues, acid hydrolases are selectively transported to lysosomes via mannose -6-phosphate receptor (MPRs), although alternative routes of transport have been described. Aims: In this work, we investigated whether the MPRs (or alternative pathways) regulate the transport and secretion of lysosomal enzymes in the rat epididymis, and whether these mechanisms are altered by changes in levels of steroid hormones. Methods: As a model of hormone deprivation, we used adult Sprague-Dawley rats, which were surgically castrated and sacrificed 48 hours later. The epididymal caput and cauda were finely chopped and left to stand for 30 min. The supernatant was collected, and the fluid was separated from sperm by centrifugation. The remaining tissue was used as a source for the study of MPRS, prosaposina and enzymes. Expression of proteins was studied by Western blot and distribution was observed by immunohistochemistry. Results and Discussion: In castrated animals, we observed that the expression of cation-dependent MPR (CD-MPR) increased in the caput and cauda of epididymis, with respect to controls. In addition, we observed CD-MPR that was redistributed to the apical region of the epithelium in castrated rats. Consistent with a possible involvement of the CD-MPR in lysosomal enzyme secretion, we observed an increase in procathepsin D in the epididymal fluid from castrated animals, accompanied by a redistribution of the enzyme to the apical region of epithelium. Because the transport and secretion of procathepsin D can follow an alternative route in other cell types, we intended to study the possible association of procathepsin D with the expression and transport of the lysosomal protein prosaposin and its receptor sortilin in the epididymal tissue of castrated rats compared with controls. We confirm, for the first time that procathepsin D and prosaposin are complexed in the epididymal fluid and that, in turn, these complexes increases in the castrated animals. As with the CD-MPR, there was a redistribution of prosaposin and sortilin to the apical region of the epithelium due to castration Furthermore, we observed a correlation between the expression of prosaposin and its receptor sortilin, and that both proteins are increased in caput but decreased in cauda of castrated animals. However, interestingly, castration induced an increase in the secretion of prosaposin in both regions of the epididymis. In conclusion, this study showed that the expression of CD-MPR and sortilin could be influenced by hormonal changes in the epididymal epithelium, and consequently induce an alteration in the normal transport of some lysosomal proteins. Finantial Support: this work was supported by a Grant (06/J280) from SECyT (UNCuyo-Mendoza). Key words: epididymis, lysosomal enzymes, receptors, hormones. Corresponding author: Dr. Miguel A. Sosa (PhD) – IHEM-CONICET, ICB (UNCuyo) 5500-Mendoza (Argentina) E-mail: msosa@fcm.uncu.edu.ar