Mannose-6-phosphate receptors in bull epididymis: their role in the distribution of lysosomal enzymes

AGUILERA AC; CARVELLI L; BOSCHINV; ZYLA L; SOSA MA

Ciudad Autonoma de Buenos Aires

Congreso; XLIX Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular; 2013

Sociedad Argentina de Investigación Bioquímica y Biología Molecular

One of the most striking features of the epididymis is the intense endocytic and secretory activity of the epithelium. In bulls, as in other mammals, hydrolytic enzymes might play a role in sperm remodelling in the epididymal fluid. In order to study the mechanism of enzyme secretion in bull epididymis, we have studied the expression and activity of cation-dependent (CD-MPR) and cation independent (CI-MPR) mannose-6-phosphate receptors, which are thought to be involved in proper delivery of lysosomal enzymes to lysosomes. We have found that the CD-MPR was highly expressed in the epididymis of sexually immature bulls (SI), decreasing significantly in adults (SM). Conversely, the expression of CI-MPR was higher in SM than in SI without regional differences being observed. On the other hand, the high activity of lysosomal enzymes in epididymis of SI and its increased tissular retention accounts for the existence of a developed and active lisosomal apparatus. By binding assays we estimated that a number of CD-MPR sites may be inactive in the SI. Moreover, some acid hydrolases found in the epididymal fluid were found to be ligands for MPRs and they were mostly recognized by CI-MPR in the SI, but not in the SM. We concluded that both MPRs could play different roles during sexual maturation of bulls, and that the CD-MPR might be involved in release of enzymes.