Phosphomannosyl receptors on the surface of spermatozoa from the cauda epididymis of the rat.

BARBIERI A; SOSA MA; GRIMALT P; MAYORGA L; BERTINI F

INTERNATIONAL JOURNAL OF ANDROLOGY

WILEY-BLACKWELL PUBLISHING, INC

Año: 1995 vol. 18 p. 113 - 119

0105-6263

This study demonstrates that beta-glucuronidase from rat preputial glands binds with highaffinity to spermatozoa from the cauda epididymis. The binding was calcium-independent andwas inhibited by mannose-6-phosphate, but not by other phosphorylated or non-phosphorylatedsugars. Binding was also inhibited by alpha-mannosidase from Dictyostelium discoideum, anenzyme known to have mannose-6-phosphate as the ligand. From solubilized spermmembranes, a protein of > 200 kDa and one of 45 kDa, were absorbed to a column of D.discoideum enzyme and to a phosphomannan column respectively, and eluted with mannose-6-phosphate. According to histochemical observations at the light and the electron microscopiclevel, gold particles coated with the enzyme became bound to the external surface of theplasmalemma in the acrosomal region of caudal spermatozoa. Similar labelling was observedusing gold particles coated with antibodies against the rat 300 kDa phosphomannosyl receptor.The existence of phosphomannosyl receptors on the sperm plasma membrane, and ourprevious demonstration of the presence of affinity sites for epididymal beta-galactosidase onthese gametes which is inhibited by phosphofructosyl derivatives, suggest strongly thatmaturing spermatozoa could be a target for glycosidases secreted into the lumen of the caudaepididymis, which then become bound to these cells via different ligand-receptor systems.