Possible secretory pathways of cathepsin D in rat epididymis

CARVELLI L; BANNOUD N; AGUILERA C; BARRERA P; MORALES CR; SOSA MA

Mar del Plata (Buenos Aires)

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2007

SAIB

Mammalian epididymis participates in sperm maturation, secreting factors to the lumen. The function of this organ is maintained by androgenic hormones. Several acid hydrolases are secreted by the epididymal epithelium (e.g.procathepsin D, pcD), although their function in the lumen is unclear. In most cells and tissues, lysosomal enzymes are transported to lysosomes via mannose-6-P receptors (MPRs). Two types of MPRs have been described; the cation-independent (CI-MPR) and the cation-dependent (CD-MPR) receptor. Alternative routes to lysosomes may be mediated by sortilin (Sor) (a receptor for prosaposin pSAP). The aims were to study the possible routes for cathepsin D secretion in epididymis and its regulation by steroid hormones. Sprague-Dawley rats and RCE-1 cell line were used, and the expression and distribution of epididymal proteins were analyzed by IPP, immunoblot and immunohystochemistry (IHC). Alternatively, metabolic labeling was carried out in RCE-1 cells. It was observed that expression of both MPRs and pcD was increased in epididymis of castrated rats. Secretion of pcD was also increased under these conditions, forming complexes with pSap. An apical redistribution of cathepsin and Sor was observed. In cell cultures these changes were observed by treatment with estradiol. We concluded that pcD may be secreted via pSap-Sor or CD-MPR and controlled by estrogenic hormones.