Surface Localization of P34H, an Epididymal Protein, during Maturation, Capacitation, and Acrosome Reaction of Human Spermatozoa1

Abstract

During epididymal transit, spermatozoa acquire new surface antigens that are involved in the acquisition of their fertilizing ability. We have previously described a 34-kDa (P34H) human epididymal sperm protein that shows antigenic and functional homologies with the hamster P26h. P34H is localized on the acrosomal cap of human spermatozoa and has been proposed to be involved in the interaction with the zona pellucida. The aim of this study was to document the expression of P34H on the sperm surface during transit along the male and female genital tracts. Immunohistochemical techniques were performed on human testes and epididymides by means of an antiserum specific for P34H. No labelling was detected on those spermatozoa found within the seminiferous tubules or in the vasa efferentia. P34H first appeared in the caput epididymidis and was restricted to the acrosomal cap. Signal intensity then increased considerably from the proximal corpus to the cauda region of the epididymis. After ejaculation, the same pattern of P34H distribution was observed, but the intensity was much lower than that characterizing the cauda epididymal spermatozoa. Strong labeling was restored after incubation in B2 medium and was maximal after 5 h of capacitation. After acrosomal exocytosis induced by a Ca2+ ionophore, the percentage of P34H-labeled spermatozoa decreased proportionally to the number of acrosome-reacted spermatozoa as determined by Pisum sativum-fluorescein isothiocyanate (FITC) labeling. P34H appeared to be strongly anchored to the sperm plasma membrane during epididymal transit as indicated by the requirement for detergent to extract this surface antigen from ejaculated spermatozoa. This confirms the importance of P34H binding to the sperm plasma membrane during epididymal maturation. We have previously proposed that P34H is involved in sperm-zone pellucida interaction. The appearance and accumulation of P34H on the sperm plasma membrane during epididymal maturation, followed by its inaccessibility associated with ejaculation, its unmasking during capacitation, and finally its elimination after the acrosome reaction, are in agreement with te proposed function of this sperm antigen.

Novelty of the Pyruvate Metabolic Enzyme Dihydrolipoamide Dehydrogenasein Spermatozoa

“…4C), indicating the release of E3 during acrosomal exocytosis. The same figure also shows the release of P26h whose homologue, P34H, has been previously shown to be released during acrosome reaction in human spermatozoa (55). Thus the results indicate that E3 is released during complete acrosome reaction and not localized in the inner acrosomal membrane, which is the part of the acrosome exposed after acrosome reaction.…”

Distribution of Glycoproteins on Feline Testicular Sperm, Epididymal Sperm and Ejaculated Sperm

“…Spermatozoa are sent from the testis to the efferent duct in an immature state [1,3,4,6,7]. The spermatozoa mature functionally during their transit through the epididymis, and they undergo capacitation and are stored in the cauda epididymis [2,3,5]. GPs that coat the surface of spermatozoa are acquired or lost and the characteristics of the GPs on the surface of the plasma membrane are changed during their transit through the epididymis [1-3].…”

“…The spermatozoa mature functionally during their transit through the epididymis, and they undergo capacitation and are stored in the cauda epididymis [2,3,5]. GPs that coat the surface of spermatozoa are acquired or lost and the characteristics of the GPs on the surface of the plasma membrane are changed during their transit through the epididymis [1][2][3]. There have been many reports on the relationships between sperm maturation, sperm capacitation, and decapacitation factors (DFs), and these have been investigated in many mammalian species [2,4,6,[9][10][11].…”

“…GPs that coat the surface of spermatozoa are acquired or lost and the characteristics of the GPs on the surface of the plasma membrane are changed during their transit through the epididymis [1][2][3]. There have been many reports on the relationships between sperm maturation, sperm capacitation, and decapacitation factors (DFs), and these have been investigated in many mammalian species [2,4,6,[9][10][11]. Kawakami et al [6] used FITC-lectins to investigate GP adhesion to the surface of canine caudal epididymal sperm and ejaculated spermatozoa, and the results showed that PHA-E-lectin did not bind to caudal epididymal sperm, but did bind to ejaculated sperm.…”

Optimization of microelectrophoresis to select highly negatively charged sperm

“…In humans, binding of the epididymal secretions to the sperm membrane is functionally important for zona binding [69], oocyte fusion [70], and fertilization [71]. Defects in the uptake of epididymal secretions onto the sperm membrane have been reported in patients with abnormal sperm parameters [72].…”