Binder Of Sperm Proteins Research Articles

Regional abundances of binder of sperm (BSP) proteins are negatively associated with the quality of frozen-thawed bovine spermatozoa.

The localization and abundance of the sperm BSP proteins correlate with in vitro fertility in domestic bulls used in artificial insemination service. Binder of sperm (BSP) proteins, secreted mainly by the accessory sex glands, are the major protein family present in bovine seminal plasma and on the sperm surface after ejaculation. In vivo, BSP proteins facilitate sperm capacitation and sperm reservoir formation; however, their impact on sperm function within the in vitro systems is less clear. Therefore, this biomarker-based study aimed to characterize the localization and abundance of BSP proteins from in vitro processed frozen-thawed bovine spermatozoa. Using image-based flow cytometry and Western blotting, BSP protein localization, abundance, membrane and acrosomal integrity were investigated in the supernatant (nonmotile) and pellet (motile) fractions of gradient-separated bull spermatozoa. Spermatozoa from the supernatant fraction had high enrichment of all BSP proteins investigated (BSP1, BSP3, BSP5; P < 0.05) when compared to the pellet fraction. In the pellet fraction, BSP1 and BSP3 bound predominately to the acrosomal region, whereas BSP5 had a high affinity for the midpiece. However, in the supernatant fraction, BSP proteins predominately coated the entire sperm surface resulting in the loss of regional specificity. High BSP protein abundance in the spermatozoa also correlated with acrosome and membrane damage. Whereas a high abundance of BSP5 correlated with low embryo cleavage rates, high abundance of BSP1 on the sperm head coincided with a high blastocyst rate. Therefore, changes in the quantity and localization of specific BSP proteins could act as potential biomarkers of sperm quality and fertility.

Seminal Plasma Proteins Associated with The Fertility of Brahman Bulls in The Colombian Low Tropics.

The sperm interacts with seminal plasma proteins during its transport through the female reproductive tract to reach the oocyte. Seminal plasma proteins have been associated as biomarkers of fertility in bovine males, while two-dimensional electrophoresis in polyacrylamide gels under denaturing conditions (2D-PAGE) is a useful technique for their separation, allowing their subsequent analysis with the aid of specialised software. Brahman bulls are known for their tolerance to tropical conditions such as low-quality pastures, high temperatures, and relative humidity as well as moderate resistance to infestations by parasites and insects. The present study describes the two-dimensional electrophoretic profiles of the seminal plasma proteins in the rainy and dry seasons, associating them with the fertility of Brahman bulls in the Colombian Orinoquía in a 90-days breeding season and a single-sire mating system (1 bull per 50 Brahman cows) with 60 consecutive days of rest. The fertility-related seminal plasma protein spots increased in the dry season. Likewise, a meaningful relationship was found between the protein spots that possibly coincide with the Binder of Sperm Proteins. It was also found that bulls with the highest percentages of pregnancy also had similarities in their 2D seminal plasma maps. We conclude that the seminal plasma protein profile of Brahman bulls raised in the Colombian low tropic changes between rainy and dry seasons, and such changes may influence the reproductive performance of those animals.

Functional attributes of seminal proteins in bull fertility: a systematic review.

Proteomic approaches have been widely used in reproductive studies to uncover protein biomarkers of bull fertility. Seminal plasma is one of the most relevant sources of these proteins that may influence sperm physiology. Nonetheless, there are still gaps in existing knowledge in the functional attributes of seminal proteins. Thus, we reviewed the relationships between seminal plasma proteins and bull fertility by conducting a systematic review with data obtained from 71 studies. This review showed that the associations related to fertility improvement with the use of total seminal plasma proteins are still controversial. None of the studies explored the sperm fertilizing ability following these interactions. By contrast, the exposure to a single protein, such as osteopontin, binder of sperm proteins, and heparin binding proteins, can increment sperm motility, capacitation, and fertilizing ability by modulating intracellular calcium concentrations, removing lipids from sperm membranes, and regulating the acrosome reaction. Variations in protein analyses and the protein contents and their abundances between animals contributed to the difficulty of establishing protein biomarkers of fertilizing potential of the bull sperm. Indeed, the heterogenicity of methodologies was a limitation of this review. Standardized methods of seminal protein analyses, as well as sperm endpoints, may minimize such discrepancies. In conclusion, potential biomarkers of sperm parameters are still to be established. Future studies should evaluate protein isoforms and how they interact with sperm to ascertain their biological functions.

Novel affinity chromatography method for the efficient purification of recombinant Binder of SPerm homolog proteins.

In mammalian species, a family of proteins named the Binder of SPerm proteins, which are expressed in the male reproductive tract, have been shown to play a role in epididymal sperm maturation and sperm capacitation. Recently, one homolog from human and two homologs from mouse were characterized. In order to further investigate the biochemical activity of these proteins, efficient purification procedures are required to isolate the proteins. Since these proteins are produced in very minute quantities, we exploited the high capacity of Escherichia coli to produce larger quantities of recombinant proteins that were subsequently purified using affinity chromatography on a diethylaminoethyl-Sephadex A-25 column. Binder of SPerm proteins have been shown to interact with pseudo-choline groups such as diethylaminoethyl through affinity rather than ionic interactions. The aim of the current study was to develop a novel method for purifying these recombinant proteins, produced in Escherichia coli cells. Diethylaminoethyl is positively charged and is a weak anion exchanger, but binder of sperm proteins interacts with affinity to this resin. This study presents a new, rapid, and cost-effective purification method that provides with an exceptional purity level, which can be used to study their roles in mammalian fertilization.

Progesterone induces sperm release from oviductal epithelial cells by modifying sperm proteomics, lipidomics and membrane fluidity

The sperm reservoir is formed after insemination in mammals, allowing sperm storage in the oviduct until their release. We previously showed that physiological concentrations of progesterone (P4) trigger in vitro the sperm release from bovine oviductal epithelial cells (BOECs), selecting a subpopulation of spermatozoa with a higher fertilizing competence. Here, by using Western-Blot, confocal microscopy and Intact Cell MALDI-TOF-Mass Spectrometry strategies, we elucidated the changes derived by the P4-induced release on sperm cells (BOEC-P4 spz). Our findings show that, compared to controls, BOEC-P4 spz presented a decrease in the abundance of Binder of Sperm Proteins (BSP) −3 and −5, suggesting one mechanism by which spermatozoa may detach from BOECs, and thus triggering the membrane remodeling with an increase of the sperm membrane fluidity. Furthermore, an interesting number of membrane lipids and proteins were differentially abundant in BOEC-P4 spz compared with controls.

Sperm and seminal plasma proteomics of high- versus low-fertility Holstein bulls

Sperm are highly specialized compartmentalized cells, with unique compositional, morphological and functional properties, including a plasma membrane that undergoes dynamic protein remodeling and surface modifications. Seminal plasma is a highly complex biological fluid containing proteins, amino acids, enzymes, fructose and other carbohydrates, lipids, major minerals and trace elements. Seminal plasma proteins are involved in regulation of osmotic pressure and pH of seminal plasma, transport of ions, lipid and hormones. The objective was to compare sperm and seminal plasma proteomes of bulls with differing fertility and to relate differences to biological processes. Semen was collected from bulls with high or low fertility (4 bulls in each category). Sperm and seminal plasma proteins were isolated, purified, subjected to 2-D gel electrophoresis, protein identification and ontology. In sperm and seminal plasma, binder of sperm proteins (BSP)-1, −3 and −5, and spermadhesin-1, ALB, TIMP, AKI and PEBP1 were higher for high-versus low-fertility bulls (P < 0.05), whereas proteins CLU, CCT5 and 8, ELSPbP1, and PSMA6 were more abundant in sperm and seminal plasma of low- versus high-fertility bulls (P < 0.05). Further, HSP90, ZFP34, IFNRF4, BCL62, NADHD, TUBB3 and Histone H1 were in greater abundance in sperm of high- compared with low-fertility bulls. The two key biological processes of proteins differentially expressed in high- and low-fertility bulls were metabolic processes and biological regulation. The most prominent molecular functions for proteins that differed are binding, catalytic and receptor activities. The main cellular components for proteins that differed are cellular, extracellular, and plasma membrane. Since protein content differed in high- versus low-fertility bulls, we inferred that the efficiency of associated sperm functions that are necessary for fertility may also differ between high- and low-fertility semen. In conclusion, differences between high- and low-fertility bulls regarding abundance of sperm and seminal plasma proteins likely contributed to differences in fertility.

Low Density Lipoproteins at 2% Concentration Can Replace Whole Egg Yolk in TES-Tris-Milk Extender for Freezing Buffalo Sperm Cells

Background: Over the years, the most commonly used extenders for semen cryopreservation contain egg yolk as cryoprotectant. However, more recent studies have used the low density lipoproteins, extract of hen egg yolk which is responsible for the cryoprotective effect. Nevertheless, little was known about its required minimum concentration as well as its interaction with other extra cellular cryoprotectants, like skimmed milk. The present study aimed at investigating the effect of replacing whole egg yolk by adding low density lipoproteins at low concentrations, in TES-Tris-skim milk based extender, on the post-thaw quality of buffalo bull sperm.Materials, Methods &amp; Results: Eighteen ejaculates were collected from six buffalo bulls and diluted with TES-Tris-skim milk based extender containing LDL, extracted from hen egg yolks, at the concentrations of 2%, 4%, 8% and 14%, against a control extender containing 20% fresh egg yolk. After semen collection, analyses of subjective motility, vigor, force tourbillon, sperm concentration (Neubauer chamber) and sperm morphology (phase contrast microscopy) were performed. The diluted semen was packaged in 0.25 mL straws, and cooling was performed on computerized machine (TK 4000®), using a cooling rate of -0.25°C/min to 5°C. Semen was kept in balance at 5°C for 4 h. The straws were frozen in an ice chest, kept at 5 cm from the surface of liquid nitrogen for 20 min and then immersed in liquid nitrogen. The samples were kept in cryogenic container until thawing. Post-thaw kinetic parameters during incubation at 37°C (CASA), sperm membrane integrity (SYBR-14/PI), membrane functionality (hypo-osmotic swelling test) and DNA fragmentation (%DFI - SCSA) were evaluated after thawing. Immediately post-thaw, total motility was higher in the control (56.53 ± 9.73) than in the tested extenders; however, after 30 min the difference was no longer detected. All other kinetic parameters presented significantly better results in extenders containing 2%, 4% and 8% LDL, compared with the control. There was no difference between treatments regarding the integrity of membranes or fragmentation of the DNA after freezing/thawing procedures.Discussion: The molecules of low density lipoproteins of egg yolk have the known action of sequestering BSP ( binder of sperm proteins) protein, due to the chemical affinity of their main components, phosphatidylcholine and phosphatidylethanolamine. The BSP are responsible for removing cholesterol from the plasma membrane of the sperm, preparing it for the sperm capacitation phase. Low density lipoproteins by inhibiting the action of the BSP increase the stability of the plasma membrane during the freeze-thaw process. The milk caseins micelles have a similar ability to bind the BSP, but with lower affinity. The present study has shown that the use of purified low density lipoproteins has an advantage over the use of whole egg yolk, especially with regard to the kinetic parameters of the spermatozoa after thawing. Furthermore, it was observed that low concentrations of low density lipoproteins, such as 2%, in extenders containing skim milk, could preserve the sperm cell during the freeze-thawing process like that higher LDL concentrations and whole egg yolk. Further studies are needed to determine if the cryoprotectant action found in this study was a result of the synergistic action of skim milk with lipoproteins or even at low concentrations like 2% the lipoproteins can provide protection to the buffalo spermatozoa during freezing, as it has been reproduced in other domestic species. In conclusion, our results indicated that the extender TES-Tris-skim milk containing 2% LDL extracted from egg yolk could be used successfully in the cryopreservation of buffalo sperm cells.

Binder of Sperm Proteins protect ram spermatozoa from freeze-thaw damage

Cryopreservation causes sub-lethal damage which limits the fertility of frozen thawed spermatozoa. Seminal plasma has been investigated as a cryoprotectant, but has yielded inconsistent results due to considerable variation in its constituents. Individual seminal plasma proteins offer an ideal alternative to whole seminal plasma, and several have been correlated with freezing success. Binder of Sperm Proteins (BSPs) are abundant ram seminal plasma proteins which have been suggested to have significant protective effects on ram spermatozoa during cold shock. This is in direct opposition to bull spermatozoa, where BSPs cause sperm deterioration during in vitro handling. We investigated the potential of BSP1 and BSP5 to prevent freezing associated damage to important functional parameters of ram spermatozoa. BSPs purified by size exclusion chromatography improved post thaw motility and penetration through artificial mucus. Highly purified BSP1 and BSP5, isolated by gelatin affinity and RP-HPLC, improved motility and membrane integrity, and reduced post thaw protein tyrosine phosphorylation. Exposure to BSP5 before freezing increased the amount of phosphatidylethanolamine on the sperm surface after thawing. Neither BSP1 nor BSP5 prevented freezing associated changes in membrane lipid disorder. These results suggest that BSPs may significantly improve freezing outcomes of ram spermatozoa.

Binder of Sperm Proteins 1 and 5 have contrasting effects on the capacitation of ram spermatozoa.

Binder of Sperm Proteins (BSPs) are the most abundant seminal plasma protein family in the ram and bull. They have been extensively studied in the bull but less is known about their function in ovine seminal plasma and current knowledge suggests that BSPs may have different effects in these two species. In the bull, they facilitate capacitation and destabilize the sperm membrane during in vitro handling, whereas in the ram, they appear to stabilize the sperm membrane and prevent cryopreservation-induced capacitation-like changes. Further investigation into the effects of BSPs on ram spermatozoa under capacitating conditions is required to further clarify their physiological roles in the ram. We investigated the effects of Binder of Sperm Proteins 1 and 5 on epididymal ram spermatozoa in conditions of low, moderate, and high cAMP. BSPs had minimal effects on sperm function in low-cAMP conditions, but caused significant changes under cAMP upregulation. BSP1 stabilized the membrane and qualitatively reduced protein tyrosine phosphorylation, but significantly increased cholesterol efflux and induced spontaneous acrosome reactions. BSP5 slightly increased spontaneous acrosome reactions and caused sperm necrosis. However, BSP5 had minimal effects on membrane lipid order and cholesterol efflux and did not inhibit protein tyrosine phosphorylation. These findings demonstrate that under maximal cAMP upregulation, BSP1 affected ram spermatozoa in a manner comparable to bull spermatozoa, while BSP5 did not.

Administration of intravenous iron preparations induces complement activation in anemic patients

Binder of SPerm (BSP) proteins, the main proteins from bovine seminal plasma, are known to partially intercalate into the outer leaflet of the spermatozoa membrane and bind to choline-containing lipids being present therein. This insertion generates a negative effect on semen quality after cryopreservation by inducing an early-stage capacitation of spermatozoa. The assumption of surface properties exhibited by BSP proteins was checked by tensiometry measurements: BSP proteins are highly surface active. This suggests that BSP proteins can reach the interface covered by phospholipids not only by interactions between one and each other but also due to their own surface activity. The insertion of BSP proteins into the lipid domains outer leaflet of spermatozoa was reproduced on a biomimetic system such as Langmuir monolayers. The insertion of BSP proteins can be performed in the compressible fluid domains which contain choline-bearing lipids. Monolayer films were used as well to study the complexation of BSP proteins by two phospholipid assemblies: low density lipoprotein (LDLs) from egg yolk or liposomes produced from egg phospholipids. Irrespective of the phospholipid structure (lipoprotein or liposome), BSP was hindered to alter the structure of the membrane. Only the overall ratio BSP proteins:phosphatidylcholine was important. The difference between the two sequestering agents lies on their surface properties: LDL have a strong tendency to merge with the outer layer whereas liposomes mainly remain in the bulk on the same time scale.

Milk proteins interact with goat Binder of SPerm (BSP) proteins and decrease their binding to sperm.

Seminal plasma Binder of SPerm (BSP) proteins bind to sperm at ejaculation and promote capacitation. When in excess, however, BSP proteins damage the sperm membrane. It has been suggested that milk components of semen extenders associate with BSP proteins, potentially protecting sperm. Thus, this study was conducted to investigate if milk proteins interact with BSP proteins and reduce BSP binding to goat sperm. Using gel filtration chromatography, milk was incubated with goat seminal plasma proteins and loaded onto columns with and without calcium. Milk was also fractionated into parts containing mostly whey proteins or mostly caseins, incubated with seminal plasma proteins and subjected to gel filtration. Eluted fractions were evaluated by immunoblot using anti-goat BSP antibodies, confirming milk protein-BSP protein interactions. As determined by ELISA, milk proteins coated on polystyrene wells bound to increasing of goat BSP proteins. Far-western dot blots confirmed that BSP proteins bound to caseins and β-lactoglobulin in a concentration-dependent manner. Then, cauda epididymal sperm from five goats was incubated with seminal plasma; seminal plasma followed by milk; and milk followed by seminal plasma. Sperm membrane proteins were extracted and evaluated by immunoblotting. The pattern of BSP binding to sperm membrane proteins was reduced by 59.3% when epididymal sperm were incubated with seminal plasma and then with skimmed milk (p < 0.05). When epididymal sperm were treated with milk followed by seminal plasma, coating of sperm with BSP proteins was not significantly reduced (57.6%; p > 0.05). In conclusion, goat BSP proteins have an affinity for caseins and whey proteins. Milk reduces BSP binding to goat sperm, depending whether or not sperm had been previously exposed to seminal plasma. Such events may explain the protective effect of milk during goat sperm preservation.

255 SEMINAL PLASMA PROTEINS: FUNCTIONAL ATTRIBUTES AND POTENTIAL MARKERS OF FERTILITY

Mammalian seminal plasma is a complex milieu containing, mostly, secretions of the epididymides and accessory sex glands. After ejaculation, proteins of the seminal fluid interact with sperm and participate in several events, including sperm motility, protection against immune reactions, oxidative processes and microorganisms, interaction with the oviduct epithelium, capacitation, acrosome reaction, and fertilization. Given these aspects, the present talk is focused on seminal plasma proteins and cross-species comparisons of their functional attributes. Experiments that will be presented used gel-based and shotgun proteomics. Binder of sperm proteins are major components of ruminant seminal plasma, while spermadhesins are predominant in the boar and deer (Mazama gouazoubira; Mazama nemorivag) seminal fluid. Annexins (rabbits), clusterin (peccaries: Pecari tajacu), and arginine esterase (coatis: Nasua nasua; dogs) are the most abundant proteins in seminal fluid of other species. Such diversity may reflect differences in how paternal factors modulate fertility. Studies have also reported empirical associations between seminal proteins, sperm freezability, and fertility indexes in ruminants and other domestic species. As evidenced by experiments using IVF, mainly in the bovine, specific seminal proteins influence the fertilizing capacity of both epididymal and ejaculated sperm, as well as early embryo development. In summary, fundamental knowledge gathered by studies of seminal plasma proteome can be used to identify molecular markers of fertility. Availability of such markers will potentially improve the outcome of artificial reproductive technologies. Diversity of seminal plasma composition, however, represents challenges for discovery of fertility markers in unique species. Seminal plasma proteins may also be related to new phenotypes, such as bull differences in sperm survival after sexation. This research was funded in part by the Brazilian Research Councils (CAPES and CNPq) and Ceara State Foundation for Scientific and Technological Development (FUNCAP).

Sequestration of bovine seminal plasma proteins by different assemblies of phosphatidylcholine: A new technical approach

Binder of SPerm (BSP) proteins, the main proteins from bovine seminal plasma, are known to partially intercalate into the outer leaflet of the spermatozoa membrane and bind to choline-containing lipids being present therein. This insertion generates a negative effect on semen quality after cryopreservation by inducing an early-stage capacitation of spermatozoa. The assumption of surface properties exhibited by BSP proteins was checked by tensiometry measurements: BSP proteins are highly surface active. This suggests that BSP proteins can reach the interface covered by phospholipids not only by interactions between one and each other but also due to their own surface activity. The insertion of BSP proteins into the lipid domains outer leaflet of spermatozoa was reproduced on a biomimetic system such as Langmuir monolayers. The insertion of BSP proteins can be performed in the compressible fluid domains which contain choline-bearing lipids. Monolayer films were used as well to study the complexation of BSP proteins by two phospholipid assemblies: low density lipoprotein (LDLs) from egg yolk or liposomes produced from egg phospholipids. Irrespective of the phospholipid structure (lipoprotein or liposome), BSP was hindered to alter the structure of the membrane. Only the overall ratio BSP proteins:phosphatidylcholine was important. The difference between the two sequestering agents lies on their surface properties: LDL have a strong tendency to merge with the outer layer whereas liposomes mainly remain in the bulk on the same time scale.

Evolution and function of mammalian binder of sperm proteins.

Binder of sperm (BSP) proteins are ubiquitous among mammals and have been extensively investigated over the last three decades. They were first characterized in bull seminal plasma and have now been identified in more than 15 different mammalian species where they represent a superfamily. In addition to sharing a common structure, BSP proteins share many characteristics. They are expressed by seminal vesicles and epididymides, interact with similar ligands and bind to the outer leaflet of sperm membranes via an interaction with choline phospholipids. In addition to playing a major role in sperm capacitation, they are implicated as molecular chaperones in sperm motility and viability, in the formation of the oviductal sperm reservoir, in the regulation of cell volume and possibly in the interaction between sperm and oocytes, making them crucial multifunctional proteins. Furthermore, BSP proteins can bind to egg yolk low-density lipoproteins and milk components, an interaction important for the protection of sperm during semen preservation in liquid or frozen state. Our current knowledge of BSP proteins strongly emphasizes their fundamental importance in male fertility and in the optimization of semen preservation techniques. Much work is still ahead in order to fully understand all the mysteries of BSP proteins.

New Insights into the Phylogeny and Gene Context Analysis of Binder of Sperm Proteins (BSPs).

Seminal plasma (SP) proteins support the survival of spermatozoa acting not only at the plasma membrane but also by inhibition of capacitation, resulting in higher fertilizing ability. Among SP proteins, BSP (binder of sperm) proteins are the most studied, since they may be useful for the improvement of semen diluents, storage and subsequent fertilization results. However, an updated and detailed phylogenetic analysis of the BSP protein superfamily has not been carried out with all the sequences described in the main databases. The update view shows for the first time an equally distributed number of sequences between the three families: BSP, and their homologs 1 (BSPH1) and 2 (BSPH2). The BSP family is divided in four subfamilies, BSP1 subfamily being the predominant, followed by subfamilies BSP3, BSP5 and BSP2. BSPH proteins were found among placental mammals (Eutheria) belonging to the orders Proboscidea, Primates, Lagomorpha, Rodentia, Chiroptera, Perissodactyla and Cetartiodactyla. However, BSPH2 proteins were also found in the Scandentia order and Metatheria clade. This phylogenetic analysis, when combined with a gene context analysis, showed a completely new evolutionary scenario for the BSP superfamily of proteins with three defined different gene patterns, one for BSPs, one for BSPH1/BSPH2/ELSPBP1 and another one for BSPH1/BSPH2 without ELSPBP1. In addition, the study has permitted to define concise conserved blocks for each family (BSP, BSPH1 and BSPH2), which could be used for a more reliable assignment for the incoming sequences, for data curation of current databases, and for cloning new BSPs, as the one described in this paper, ram seminal vesicle 20 kDa protein (RSVP20, Ovis aries BSP5b).

Altered Expression Pattern of Major Seminal Plasma Protein Genes in Seminal Vesicles of Water Buffalo (Bubalus bubalis)

The binder of sperm proteins (BSP) are secretary products of seminal vesicles. Secretions from the seminal vesicles contribute more to seminal plasma which determine the quality of the semen. The concentration of BSPs in seminal plasma has been negatively correlated with cryopreservation. An analysis of expression profile of seminal plasma proteins could be critical for better freezability of semen. Present study was carried out to assess the expression levels of major seminal plasma protein genes viz., BSP1, BSP3 and BSP5 from seminal vesicles of water buffalo using Real Time PCR. The study consisted of identification of a suitable reference gene in seminal vesicles followed by the expression analysis of major bovine seminal plasma protein (BSP) genes. The most stable reference gene among the three (glyceraldehyde 3-phosphate dehydrogenase, ribosomal protein S15a (RPS15a) and beta-actin), was found to be RPS15a and therefore, was used for normalization of target gene expression. Data analysis of major BSPs showed highest relative expression of BSP3 followed by BSP1 and BSP5. The ratio of relative expression of BSP1:BSP3:BSP5 was 10:18:1. The results from the study also showed an altered expression pattern of major BSP genes in buffalo seminal vesicles. Thus, it can be concluded that the altered expression of these genes at mRNA level would also be reflected at protein level in the seminal plasma. This could be one of the probable reasons for poor freezability of buffalo semen as compared to cattle and the finding helps in designing better cryopreservation strategies for buffalo semen.

Interaction of milk proteins and Binder of Sperm (BSP) proteins from boar, stallion and ram semen

BackgroundMammalian semen contains a family of closely related proteins known as Binder of SPerm (BSP proteins) that are added to sperm at ejaculation. BSP proteins extract lipids from the sperm membrane thereby extensively modifying its composition. These changes can ultimately be detrimental to sperm storage. We have demonstrated that bovine BSP proteins interact with major milk proteins and proposed that this interaction could be the basis of sperm protection by milk extenders. In the present study, we investigated if homologous BSP proteins present in boar, stallion and ram seminal plasma display a similar affinity for the milk proteins in order to assess whether the mechanism of sperm protection by milk for these species could be general.MethodsSkim milk was incubated with seminal plasma proteins (boar, stallion and ram), chromatographed on a Sepharose CL-4B column and protein fractions were analyzed by immunoblotting.ResultsBoar, stallion and ram BSP proteins displayed affinity for a milk protein fraction (F1) mainly composed of α-lactalbumin, β-lactoglobulin, and κ-casein. They also had affinity for another milk protein fraction (F2) composed mostly of casein micelles. However, stallion BSP showed higher affinity for the fraction (F1).ConclusionsThese results further extend our view that the association of BSP proteins with milk proteins could be a general feature of the mechanism of mammalian sperm protection by milk to prevent detrimental effect of prolonged exposure of sperm to seminal plasma.

Epididymal Binder of SPerm genes and proteins: what do we know a decade later?

Binder of SPerm (BSP) proteins from ungulates (more specifically bull, bison, buffalo, stallion, boar, goat, and ram) have been extensively studied in the past 30years. These proteins secreted by seminal vesicles constitute between 1 and 60% of total seminal plasma proteins depending on the species. In addition to sharing many biochemical characteristics such as the ability to bind to gelatin, glycosaminoglycans, choline phospholipids, and lipoproteins, they also share a main function: promoting sperm capacitation. Over the last 10years, new members of the BSP superfamily have been discovered. These proteins found in bulls, humans, mice, and rabbits are expressed in the epididymides rather than in seminal vesicles and constitute only a minute percentage of the seminal plasma proteins. However, they share many characteristics with BSPs expressed by accessory glands including their structure, their ability to bind to the aforementioned BSP ligands, as well as their ability to promote sperm capacitation. More investigations need to be done on epididymal BSP proteins, but studies described in this review constitute a solid foundation toward deciphering the significance of epididymal BSP proteins in male fertility.

Murine binder of sperm protein homolog 1: a new player in HDL-induced capacitation.

Binder of sperm (BSP) proteins are ubiquitous among mammals and are exclusively expressed in male genital tract. The main function associated with BSP proteins is their ability to promote sperm capacitation. In mice, two proteins (BSP protein homolog 1 (BSPH1) and BSPH2) have been studied. Using recombinant strategies, BSPH1 was found to bind to epididymal sperm membranes and promote sperm capacitation in vitro. The goal of this study was to evaluate the role of native murine BSPH1 protein in sperm capacitation induced by BSA and HDLs. The effect of antibodies, antigen-binding fragments (Fabs), and F(ab')2 specific for murine BSPH1 on BSA- and HDL-induced capacitation was tested. Results indicate that BSPH1 has no direct role in BSA-induced capacitation. However, antibodies, Fabs, and F(ab')(2) could block capacitation induced by HDLs and could inhibit the HDL-induced increase in tyrosine phosphorylation, suggesting a specific interaction between HDLs and BSPH1. Results indicate that murine BSPH1 proteins in mice could be a new important piece of the puzzle in sperm capacitation induced by HDLs. As murine BSPH1 is orthologous to human BSPH1, this study could also lead to new insights into the functions and the importance of the human protein in male fertility.

Increased conception rates in beef cattle inseminated with nanopurified bull semen.

Aberrant sperm phenotypes coincide with the expression of unique sperm surface determinants that can be probed by objective, biomarker-based semen analysis and targeted as ligands for semen purification. This study evaluated a nanoparticle-based magnetic purification method that removes defective spermatozoa (∼30% of sample) from bull semen and improves sperm sample viability and fertilizing ability in vitro and in vivo. Two types of nanoparticles were developed: a particle coated with antibody against ubiquitin, which is present on the surface of defective spermatozoa, and a particle coated with the lectin peanut agglutinin, which binds to glycans exposed by acrosomal damage. In a 2 yr artificial insemination field trial with 798 cows, a conception rate of 64.5% ± 3.7% was achieved with a 10 × 10(6) sperm dose of peanut agglutinin-nanopurified spermatozoa, comparable to a control nonpurified full dose of 20 × 10(6) spermatozoa per dose (63.3% ± 3.2%) and significantly higher than a 10 × 10(6) sperm dose of nonpurified control semen (53.7% ± 3.2%; P < 0.05). A total of 466 healthy calves were delivered, and no negative side effects were observed in the inseminated animals or offspring. Because the method is inexpensive and can be fully integrated in current protocols for semen cryopreservation, it is feasible for use in the artificial insemination industry to improve fertility with reduced sperm dosage inseminations. Spermatology will benefit from nanopurification methodology by gaining new tools for the identification of candidate biomarkers of sperm quality such as binder of sperm protein 5 (BSP5), described in the present study.