Maturation-dependent glycoproteins containing both N- and O-linked oligosaccharides in epididymal sperm plasma membrane of rhesus monkeys (Macaca mulatta)

Glycosylation is one of the important post-translational modifications of sperm plasma membrane proteins during the maturation of epididymal spermatozoa that results in the development of motility and fertilizing capability. The aim of the present study was to identify and characterize the maturation-dependent asparagine-linked (N-linked) and serine- and threonine-linked (O-linked) glycoproteins of the epididymal spermatozoa of rhesus monkeys. The presence of N- and O-linked glycoproteins was confirmed by treatment of sperm membranes with N-glycosidase F and O-glycosidase. The major maturation-dependent sperm membrane glycoproteins identified on blots of SDS-PAGE-fractionated proteins of purified sperm plasma membranes from five segments of epididymis, probed with biotinylated lectins and Vectastain-ABC reagent included O-linked 170, 150, 86 and 60/58 kDa glycoproteins; N-linked 68, 56, 48 and 38 kDa glycoproteins and N- and O-linked 116 kDa glycoprotein, all of which exhibited marked differences in the degree of glycosylation between immature and mature sperm surfaces. These glycoproteins can be used as markers of sperm maturation in the epididymis of rhesus monkeys, during the screening of antifertility agents acting at the epididymis, or may be developed as potential sperm antigens. The 100% inhibition of fertility in female rats and rabbits immunized with major maturation-dependent 116 kDa glycoprotein showed the significance of glycosylation changes in the maturation status of epididymal spermatozoa. This 116 kDa protein can be used as a marker parameter of sperm maturation in the rhesus monkey, which is often the preferred animal model for preclinical studies. These results will contribute to the identification of an appropriate animal model for the development of male contraceptives in humans.