Seminal plasma proteins of adult boars and correlations with sperm parameters

Abstract

The present study was conducted to identify the major seminal plasma protein profile of boars and its associations with semen criteria. Semen samples were collected from 12 adult boars and subjected to evaluation of sperm parameters (motility, morphology, vitality, and percent of cells with intact acrosome). Seminal plasma was obtained by centrifugation, analyzed by two-dimensional SDS-PAGE, and proteins identified by mass spectrometry (electrospray ionization quadrupole time-of-flight). We tested regression models using spot intensities related to the same proteins as independent variables and semen parameters as dependent variables (P ≤ 0.05). One hundred twelve spots were identified in the boar seminal plasma gels, equivalent to 39 different proteins. Spermadhesin porcine seminal protein (PSP)-I and PSP-II, as well as spermadhesins AQN-1, AQN-3 and AWN-1 represented 45.2 ± 8% of the total intensity of all spots. Other proteins expressed in the boar seminal plasma included albumin, complement proteins (complement factor H precursor, complement C3 precursor and adipsin/complement factor D), immunoglobulins (IgG heavy chain precursor, IgG delta heavy chain membrane bound form, IgG gamma-chain, Ig lambda chain V-C region PLC3, and CH4 and secreted domains of swine IgM), IgG-binding proteins, epididymal-specific lipocalin 5, epididymal secretory protein E1 precursor, epididymal secretory glutathione peroxidase precursor, transferrin, lactotransferrin and fibronectin type 1 (FN1). On the basis of the regression analysis, the percentage of sperm with midpiece defects was related to the amount of CH4 and secreted domains of swine IgM and FN1 (r² = 0.58, P = 0.006), IgG-binding protein (r² = 0.41, P = 0.024), complement factor H precursor (r² = 0.61, P = 0.014) and lactadherin (r² = 0.45, P = 0.033). The percentage of sperm with tail defects was also related to CH4 and secreted domains of swine IgM and FN1 (r² = 0.40, P = 0.034), IgG-binding protein (r² = 0.35, P = 0.043) and lactadherin (r² = 0.74, P = 0.001). Sperm motility, in turn, had association with the intensities of spots identified as lactadherin (r² = 0.48, P = 0.027). In conclusion, we presently describe the major proteome of boar seminal plasma and significant associations between specific seminal plasma proteins and semen parameters. Such relationships will serve as the basis for determination of molecular markers of sperm function in the swine species.

Characterization of the porcine seminal plasma proteome comparing ejaculate portions

“…The boar SP samples evaluated by Druart et al [15] and Gonzalez-Cadavid et al [16] seem to come from SRF as they were collected using glove-hand method, while SP-samples evaluated in the present study come from the entire ejaculate, including SRF and post-SRF. In this context, it is well known that the total protein composition differs among boar ejaculate fractions [43].…”

“…A full decrypting of the boar SP-proteome is challenging since most total protein mass is taken up by a few number of low molecular weight proteins, the so-called most abundant proteins. Previous proteomic studies in boar SP using gel electrophoresis allowed identifying simultaneously a limited number of proteins [15,16]. It is well known that the gel-based techniques presents a limited resolution and most abundant proteins typically mask the identification of less abundant ones [24].…”

“…However, identified SP-proteins have proven antioxidant activity. For instance, Albumin, a common SPprotein encoded as binding activity, which has proved capacity in protecting sperm against oxidative stress caused by lipid peroxidation [16]. Likewise, some identified SPproteins encoded in GO as metabolic function show oxidoreductase activity, for instance Epididymal secretory glutathione peroxidase and Superoxide dismutase.…”

“…Unfortunately, the boar SP-proteome is still far from being completely decoded, requiring further research [5,15]. Despite the economic relevance, porcine is currently the livestock species with the fewer SP-proteins identified, less than 100 [15,16], which contrasts with other livestock species, such as poultry or ovine with more than 600 SP-proteins identified. This shortage in porcine is surprising, considering boar ejaculates yield a large SP-volume, usually above 150 mL.…”

Roles of the reproductive tract in modifications of the sperm membrane surface

“…Several seminal plasma-specific proteins have been identified, and their importance in sperm physiology has also been addressed [26]. For example, seminal plasma protein profiles have been correlated with sperm and semen quality in adult boars [38], and post-thawing application or pre-freezing exposure of spermatozoa to the seminal plasma improves sperm quality, motility, and cryo-survival, eventually improving the fertilization ability of the sperm cells [39]. It is therefore clear at this point, that epididymal maturation is essential for successful fertilization, and that components from the male genital tract can serve as indicators for the evaluation of male fertility and can modify the protein profiles of the sperm membrane surface, which provides an alternative opportunity to regulate the function and fertilizing ability of the sperm.…”