Interaction of lysosomal enzymes with spermatozoa from bovine epididymis. Possible implications of MPRs.

AGUILERA AC; BOSCHIN V; CARVELLI L; SOSA MA

Congreso; L Reunión Anual de la Sociedad Argentina de Investigación Bioquímica (SAIB).; 2014

Mammalian epididymis participates in sperm maturation through its endocytic and secretory activity. In bulls, as in other mammals, many lysosomal enzymes (LE) are secreted to the epididymal fluid. Here, we proposed to study the interaction LE secreted by the epididymal epithelium with spermatozoa, in order to evaluate the participation of mannose-6-phosphate receptors (MPRs). We observed that b-galactosidase (b-Gal), b-glucuronidase (b-Glu), and N-acetyl-b-D-glucosaminidase (b-NAG) associated to sperm membrane are released easily with increasing ionic strength or M6P, meanwhile a-mannosidase (a-MAN) and a-Fucosidase (a-Fuc) mostly remained associated to the gametes after treatments. The values of KD and Bmax for MPRs were estimated from curves of binding assays using an exogenous enzyme, and showed a higher number of active CI-MPR sites and with more affinity to phosphomannosyl ligands. We also observed that both MPRs distribute differently on the sperm surface and that CD-MPR is redistributed during epididymal transit. Instead, the CIMPR is mostly concentrated at the acrosomal region along the epididymal duct. We concluded that both MPRs are present in bull spermatozoa and they interact differently with LE in the epididymal lumen. Thus, MPRs may interact with LE for transport to the female reproductive tract, suggesting new roles for these receptors.