Glycosidases Interact Selectively With Mannose-6-Phosphate Receptors of Bull Spermatozoa

Glycosidases may play a role in sperm maturation during epididymal transit. In this work, we describe the interaction of these enzymes with bull spermatozoa. We found that -galactosidase associated to spermatozoa can be released under low ionic strength conditions, whereas the interaction of N-acetyl--D-glucosaminidase and -glucuronidase with spermatozoa appeared to be stronger. On the other hand, -mannosidase and -fucosidase cannot be removed from the gametes. In addition, part of N-acetyl--D-glucosaminidase, -galactosidase, and -glucuronidase can also be released by mannose-6-phosphate. Taking into account these data, we explored the presence of cation-independent- and cation-dependent-mannose-6-phosphate receptors in the spermatozoa and found that cation-independent mannose-6-phosphate receptor is highly expressed in bull spermatozoa and cation-dependent-mannose-6-phosphate receptor is expressed at a lesser extent. In addition, by immunofluorescence, we observed that cation-independent-mannose-6-phosphate receptor is mostly located at the acrosomal zone, whereas cation-dependent-mannose-6-phosphate receptor presents a different distribution pattern on spermatozoa during the epididymal transit. N-acetyl--D-glucosaminidase and -glucuronidase isolated from epididymal fluid interacted mostly with cation-independent-mannose-6-phosphate receptor, while -galactosidase was recognized by both receptors. We concluded that glycosidases might play different roles in bull spermatozoa and that mannos-6-phosphate receptors may act as recruiters of some enzymes. J. Cell. Biochem. 117: 2464-2472, 2016. (c) 2016 Wiley Periodicals, Inc.