Albumin Is Synthesized in Epididymis and Aggregates in a High Molecular Mass Glycoprotein Complex Involved in Sperm-Egg Fertilization

Abstract

The epididymis has an important role in the maturation of sperm for fertilization, but little is known about the epididymal molecules involved in sperm modifications during this process. We have previously described the expression pattern for an antigen in epididymal epithelial cells that reacts with the monoclonal antibody (mAb) TRA 54. Immunohistochemical and immunoblotting analyses suggest that the epitope of the epididymal antigen probably involves a sugar moiety that is released into the epididymal lumen in an androgen-dependent manner and subsequently binds to luminal sperm. Using column chromatography, SDS-PAGE with in situ digestion and mass spectrometry, we have identified the protein recognized by mAb TRA 54 in mouse epididymal epithelial cells. The ∼65 kDa protein is part of a high molecular mass complex (∼260 kDa) that is also present in the sperm acrosomal vesicle and is completely released after the acrosomal reaction. The amino acid sequence of the protein corresponded to that of albumin. Immunoprecipitates with anti-albumin antibody contained the antigen recognized by mAb TRA 54, indicating that the epididymal molecule recognized by mAb TRA 54 is albumin. RT-PCR detected albumin mRNA in the epididymis and fertilization assays in vitro showed that the glycoprotein complex containing albumin was involved in the ability of sperm to recognize and penetrate the egg zona pellucida. Together, these results indicate that epididymal-derived albumin participates in the formation of a high molecular mass glycoprotein complex that has an important role in egg fertilization.

Proteome Profiling of Canine Epididymal Fluid: In Search of Protein Markers of Epididymal Sperm Motility

“…Albumins are low-molecular weight proteins (about 65 kDa) [71], which are secreted by the testes, epididymides, and prostate. Studies have shown that albumins are implicated in the fertilization-associated events, such as sperm capacitation [72] and the zona pellucida penetration [73]. In one of our previous studies, we have shown that the seminal plasma albumin (ALB) is highly correlated with the motility parameters of stallion spermatozoa [74].…”

Polish Journal of Veterinary Sciences

“…Additionally, albumin (ALB) was identified phosphoprotein band with molecular weight of 66 kDa. Albumin seems to be a part of a high molecular mass glycoprotein complex (~260 kDa) that is involved in sperm penetration of the zona pellucida (Arroteia et al 2014).…”

Polish Journal of Veterinary Sciences

“…Moreover, albumins increase the fluidity of the sperm cell membrane during capacitation, and they remove cholesterol and other sterols from the plasma membrane prior to fertilization (Macıas-Garcıa et al 2015). Arroteia et al (2014) found that the sperm membrane contains albumin, which is involved in the penetration of the zona pellucida of egg. The influence of exogenous (but not endogenous) albumin or bovine serum albumin (BSA) on sperm function has been more widely researched, and BSA has been used as a component of sperm capacitation medium.…”