Distribution of CD-MPR and prosaposin in the epididymis of sortilin-knockout mice. Possible hormonal regulation

MALOSSI ELIAS; CARVELLI LORENA; AGUILERA CAROLINA; SOSA ESCUDERO MIGUEL

Mendoza

Congreso; XXVIII Reunión Científica Anual de la Sociedad de Biología de Cuyo; 2010

Sociedad de Biología de Cuyo

The epididymis is involved in sperm maturation through the secretion of factors into the lumen, and its integrity and functionality depend on steroid hormones. Epididymal secretion is enriched in acid hydrolases. In most cell types, these enzymes have a residue mannose-6-phosphate (M6P) to be transported to lysosomes via M6P receptors (CI-MPR or CD-MPR). Other lysosomal proteins (such as prosaposin, PSAP) are transported (complexed with procathepsin D, PCD) through the sortilin receptor. This study set out to determine whether PCD is transported and secreted through the CD-MPR, sortilin or both pathways in mouse epididymis, and if these mechanisms are altered by hormone deprivation. We used transgenic sortilin-knockout mice (SKO) and evaluated the effect of castration on the expression and distribution of proteins in epididymis. After 48 hours, the epididymides were removed, fixed and processed for immunohistochemistry. Besides morphological changes, castration induced changes in the expression and distribution of proteins in the epididymal epithelium. We observed increased immunoreactivity of CD-MPR and PSAP in SKO mice, indicating a likely compensatory mechanism to the absence of sortilin. Furthermore, immunoreactivity for CD-MPR and PSAP increased due to castration in both controls and SKO, and there was a redistribution of CD-MPR to apical areas in the epithelium. We conclude that CD-MPR and sortilin are alternative routes for some lysosomal proteins in the epididymis.