Mannose-6-Phosphate Receptors mediate the interaction of lysosomal enzymes with bovine epididymal spermatozoa

BOSCHÍN V; CARVELLI L; SOSA MA; AGUILERA AC

Mendoza

Congreso; XXXI Reunión Anual de la Sociedad de Biología de Cuyo; 2013

Sociedad de Biología de Cuyo

Mammalian epididymis is crucial for the sperm maturation, since it provides the conditions for the acquisition of their progressive motility and fertilizing ability. The presence of acid hydrolases in the epididymal fluid is striking. In most cell types, lysosomal enzymes are normally transported to lysosomes via two mannose-6-phosphate receptors (MPRs); the cation dependent- and the cation independent- MPR (CD-MPR and CI-MPR, respectively). This study was addressed to know whether these receptors are expressed in bovine spermatozoa (BS), and if they mediate interaction with epididymal enzymes. Epididymis from adult bulls (Aberdeen Angus) were carefully dissected into caput, corpus and cauda and processed separatelly. Epididymal spermatozoa and fluid were separated from each region and stored for MRP detection and to characterize the interaction enzyme-gamete. By immunoblot and IFI, using specific antibodies, we observed that both MPRs are detected in BS and the CD-MPR is redistributed along sperm surface during epididymal transit. Some acid hydrolases, such as b-galactosidase, b-N-acetyl-glucosaminidase, and b-glucosidase can be partially removed from the sperm surface with high ionic strenght or mannose-6-phosphate, indicating that they interact with MPRs. This interaction was corroborated by binding assays, showing a preference of the enzymes to CI-MPR. Other enzymes, such as a-mannosidase and a-fucosidase may be transported by an alternative mechanisms. We conclude that MPRs can be detected also in bovine spermatozoa and they could be transported to the female tract and participate in events as capacitation, acrosomal reaction and/or oocyte penetration.