Binding of a 15 kDa glycoprotein from spermatozoa of boars to surface of zona pellucida and cumulus oophorus cells

Ligands and Receptors Involved in the Sperm-Zona Pellucida Interactions in Mammals

Sperm-zona pellucida (ZP) interaction, involving the binding of sperm surface ligands to complementary carbohydrates of ZP, is the first direct gamete contact event crucial for subsequent gamete fusion and successful fertilization in mammals. It is a complex process mediated by the coordinated engagement of multiple ZP receptors forming high-molecular-weight (HMW) protein complexes at the acrosomal region of the sperm surface. The present article aims to review the current understanding of sperm-ZP binding in the four most studied mammalian models, i.e., murine, porcine, bovine, and human, and summarizes the candidate ZP receptors with established ZP affinity, including their origins and the mechanisms of ZP binding. Further, it compares and contrasts the ZP structure and carbohydrate composition in the aforementioned model organisms. The comprehensive understanding of sperm-ZP interaction mechanisms is critical for the diagnosis of infertility and thus becomes an integral part of assisted reproductive therapies/technologies.

Porcine model for the study of sperm capacitation, fertilization and male fertility

Mammalian fertilization remains a poorly understood event with the vast majority of studies done in the mouse model. The purpose of this review is to revise the current knowledge about semen deposition, sperm transport, sperm capacitation, gamete interactions and early embryonic development with a focus on the porcine model as a relevant, alternative model organism to humans. The review provides a thorough overview of post-ejaculation events inside the sow's reproductive tract including comparisons with humans and implications for human fertilization and assisted reproductive therapy (ART). Porcine methodology for sperm handling, preservation, in vitro capacitation, oocyte in vitro maturation, in vitro fertilization and intra-cytoplasmic sperm injection that are routinely used in pig research laboratories can be successfully translated into ART to treat human infertility. Last, but not least, new knowledge about mitochondrial inheritance in the pig can provide an insight into human mitochondrial diseases and new knowledge on polyspermy defense mechanisms could contribute to the development of new male contraceptives.

Characterization of sperm surface protein patterns of ejaculated and capacitated boar sperm, with the detection of ZP binding candidates

Complementary molecules on the surface of both gametes are responsible for the interaction of sperm protein receptors with zona pellucida (ZP) saccharide structures, and many primary sperm receptors for ZP glycoproteins have been disclosed in various mammals. For our study, proteins were obtained from the surface of ejaculated and in vitro capacitated boar sperm. The isolated proteins were characterized by 1D- and 2D-electrophoretic protein profiles, and by glycoprotein staining. Our results show quantitative and qualitative differences in protein and glycoprotein patterns between ejaculated and capacitated sperm. Far-western blotting with ZP glycoproteins identified 17 interactions in the subproteome of the ejaculated sperm and 14 interactions in the subproteome of the capacitated sperm. High-molecular-mass proteins, coincident with binding to ZP, were sequence-identified. Angiotensin-converting enzyme (ACE), polycystic kidney disease receptor and egg jelly receptor (PKDREJ), and acrosin precursor were successfully identified. This is the first time PKDREJ has been identified on the surface of boar spermatozoa.

Study on the in vitro effect of zearalenone and alpha-zearalenol on boar sperm-zona pellucida interaction by hemizona assay application

The mycotoxin zearalenone (zen) impairs fertility in farm animals. The aim of the present study was to investigate the effect of zearalenone and its major metabolite (alpha-zearalenol) on boar semen binding capacity, under in vitro conditions. Extended boar semen was exposed to three different concentrations of zen and alpha-zen (40, 60 and 80 microg ml(-1) of semen) for 1 h. Afterwards, the semen was washed and incubated with homologous oocyte hemizona for 4 h. A significant decrease (P < 0.001) in the number of tightly attached spermatozoa on the hemizona was obtained at concentrations of 60 microg ml(-1) and 80 microg ml(-1) of zen and alpha-zen. In conclusion, zen and alpha-zen affected the sperm-zona interaction by reducing the ability of boar spermatozoa to bind to the zona pellucida.

Saccharide-mediated interactions of boar sperm surface proteins with components of the porcine oviduct

The role of boar seminal plasma proteins attached to the sperm plasma membrane during ejaculation has been studied in saccharide-mediated events in the female reproductive tract. Heparin-binding (Hep(+)) proteins (DQH sperm surface protein, and AQN and AWN spermadhesins) and their aggregated forms (fractions II and III) interacted more strongly with both oviductal epithelium cells and fluid than non-heparin-binding (Hep(-)) proteins (PSP I and PSP II spermadhesins) and their heterodimer (fraction IV), and interactions correlate with affinity of these proteins to yeast mannan. Indirect immunofluorescence (IMF) showed that the AQN 1 spermadhesin and fraction II bind to the apical glycocalyx of the ampulla, as well as the isthmic and uterine tubal junction regions of the oviductal sections. IMF demonstrated the recognition of AQN 1 and fraction II and mannosyl components of oviductal epithelium. We suggest that Hep(+) proteins (especially AQN 1, fraction II) on sperm could enable sperm binding to oviductal epithelium and thus participate in formation of the sperm oviductal reservoir. Interactions of Hep(+) proteins to oviductal epithelium were inhibited by mannan, hyaluronic acid and sialylated O-glycoproteins. No or slight inhibition was observed with sulphated polysaccharides (heparin, chondroitin sulphate) and simple monosaccharides. Besides that, attachment of boar seminal plasma proteins to oviductal epithelium cells was affected by oviductal fluid, the natural environment in the oviduct. Moreover, the ability of hyaluronic acid to inhibit the interaction of sperm surface proteins to the oviduct might play a role in sperm release from the oviductal reservoir and in the capacitation process.

Boar Seminal Plasma Proteins and Their Binding Properties. A Review

Binding properties of a group of proteins isolated from boar seminal plasma and their role in the fertilization process are discussed. Boar seminal plasma contains different types of proteins: spermadhesins of AQN and AWN family, DQH and PSP proteins belong to the most abundant. Some of these proteins are bound to the sperm surface during ejaculation and thus protein-coating layers are formed. Sperms coated with proteins participate in different types of interactions in the following steps of the fertilization process: formation of oviductal sperm reservoir, sperm capacitation, oocyte recognition and sperm binding. Saccharide-based interactions of boar seminal plasma proteins play role in the binding of sperm to oviductal epithelium, in sperm capacitation and primary binding of sperm to zona pellucida. An interaction with phospholipid components is responsible for the protein adsorption to sperm membrane. Interactions between proteins participate in the arrangement and remodelling of sperm-coating layers. Study of boar seminal plasma proteins, their characterization and elucidation of their interactions will contribute to understanding the fertilization process. A review with 82 references.

The effects of oocyte storage and cumulus cell presence on canine zona penetration by domestic dog spermatozoa

Zona penetration assays (ZPAs) have been developed in numerous species to evaluate sperm fertilizing potential. Preservation methods to stockpile oocytes would be beneficial because of the difficulty in obtaining sufficient numbers of fresh oocytes. Using a canine ZPA, the objectives of this study were to evaluate: (1) two methods of storing canine oocytes (salt storage and intrafollicular cooling) and (2) the effects of cumulus cells on oocyte penetration. In experiment 1. oocytes from fresh ovaries were assigned at random to 3 categories: fresh control (FRE), salt storage in solution 1 (1.5 M MgCl2.6H2O; SS1) and salt storage in solution 2 (0.5 M (NH4)2SO4, 0.75 M MgCl2.6H2O, 0.2 mM ZnCl2; SS2). Each category was subdivided into two treatments: cumulus cells intact (intact) and cumulus cells removed (denuded), resulting in a total of six treatments with n > 15 oocytes per treatment for each ejaculate. Fresh (FRE) intact oocytes demonstrated greater sperm-oocyte interaction than other treatments, including FRE denuded oocytes (11.7 +/- 0.6 versus <4.1 +/- 0.5 sperm-oocyte and 94.9 versus <55.6% penetration; P < 0.01). Poor sperm-oocyte interaction was demonstrated with all salt-stored oocytes (< or = 1.6 +/- 0.2 sperm-oocyte and < 51% penetration), but was further attenuated in the absence of cumulus cells. In experiment 2, oocytes obtained from fresh (FRESH) or cooled (24 h COOL, 48 h COOL) ovaries were used with cumulus cells intact for a total of three treatments with n > 15 oocytes per treatment for each ejaculate. No significant difference was observed in sperm interaction between oocytes from fresh, 24 and 48 h COOL ovaries ( 12.3 +/- 0.5 to 13.1 +/- 0.4 sperm-oocyte and 92.2-97.7% penetration; P > 0.01). These results indicate that salt storage may cause damage to canine oocytes, subsequently impairing sperm penetration, whereas short-term intrafollicular cooling does not affect the oocyte's penetrability. Furthermore, greater sperm interaction in oocytes with an intact cumulus suggests a possible role for cumulus cells in canine gamete interaction.

Characterization of boar spermadhesins by monoclonal and polyclonal antibodies and their role in binding to oocytes

PROBLEM

The role of Ala-Trp-Asn (AWN) and Ala-Gln-Asn (AQN) families of spermadhesive sperm proteins in fertilization.

METHOD OF STUDY

The preparation and characterization of polyclonal antibodies against AWN and AQN spermadhesins and one monoclonal antibody (MAb), designated Bo.5, against AWN spermadhesin. The use of biochemical and immunocytochemical methods for characterization of spermadhesins on the sperm membrane of boar spermatozoa and in the cryostat sections of boar reproductive organs.

RESULTS

Polyclonal anti-AWN and anti-AQN antibodies specifically reacted with AWN and AQN proteins, respectively. MAb Bo.5 detected the 17-, 16-, and 14-kDa protein members of AWN subfamily. The monoclonal, as well as the polyclonal, AWN antibodies remarkably decreased the sperm binding to the egg surface in an in vitro sperm zona pellucida binding assay.

CONCLUSIONS

Presented results demonstrate that polyclonal antibodies and MAb Bo.5 against spermadhesins specifically recognize the membrane-associated antigens and inhibit the binding of sperm to oocytes. Reduced binding of sperm to oocytes, due to the antibodies, indicates the role of these spermadhesins in sperm-egg primary binding.

Binding of boar spermatozoa to porcine oocytes: effect of low molecular weight 17-kDa protein

The effect of seminal plasma and low molecular weight ACR.3 (17 kDa) protein on boar spermatozoa-porcine oocyte binding was examined. Boar seminal plasma that contains the sperm-adhesive ACR.3 protein was added to spermatozoa prior to their coincubation with oocytes, and the binding capacity of the spermatozoa so treated was compared to that of untreated cells. Similarly, purified ACR.3 protein, that binds to the egg zona pellucida, was added to noncapacitated spermatozoa, and the binding capacity of treated and untreated cells was again evaluated. In the two cases, the treatment of spermatozoa reduced their capacity to bind to the zona pellucida. We propose that the reduction in binding is due to competition for the ACR.3 binding sites on the zona pellucida between the soluble ACR.3 protein and the ACR.3 protein attached to the sperm surface. Furthermore, sperm-ZP binding was examined in the presence of ACR.3 monoclonal antibody, which specifically reacts with ACR.3 protein. Preliminary results show that addition of ACR.3 monoclonal antibody to a suspension of boar spermatozoa prior to their coincubation with oocytes did not markedly change sperm-zona binding in comparison with the control untreated spermatozoa. Our results suggest that ACR.3 protein may mediate the primary sperm-egg zona pellucida binding, and that it is one of the likely candidates for the primary sperm-ZP binding protein.

Interaction of non-aggregated boar AWN-1 and AQN-3 with phospholipid matrices. A model for coating of spermadhesins to the sperm surface

Boar spermadhesins are 12-14 kDa lectins which coat the entire acrosomal cap sperm head surface. The large amount of spermadhesins AQN-1, AQN-2, AQN-3, and AWN-1 present on in vitro capacitated spermatozoa (approximately 7 x 10(6) molecules of each spermadhesin per cell) suggested that they may bind to major component(s) of the sperm surface. We have investigated both the aggregation state of spermadhesins in seminal plasma using gel filtration chromatography, and their ability to bind to the major phospholipids of the boar sperm plasma membrane, i.e. phosphorylcholine and phosphorylethanolamine. The bulk (90%) of spermadhesins AQN-3 and AWN-1 were eluted as aggregated proteins (Mr > 50,000) with the void volume of a Sephadex G-50 column; the remaining 10% of the total amount of seminal plasma AWN-1 and AQN-3 were recovered, together with the whole amount of AQN-1 and AQN-2, in a fraction containing low-molecular-mass proteins (Mr 16,000-30,000). None spermadhesin of either gel-filtration fraction bound to a phosphorylcholine affinity matrix. On the other hand, low-molecular-mass (monomeric or dimeric) AQN-3 and AWN-1 were the only spermadhesins retained in a phosphorylethanolamine affinity column. Both AQN-3 and AWN-1 purified from seminal plasma by reverse-phase HPLC retained their lipid-binding capability. In addition, immobilization of AQN-3 and AWN-1 onto a phosphorylethanolamine matrix did not interfere with the ability of the proteins to bind bovine glycoprotein PDC-109, indicating that the structural determinants for the binding lipid and carbohydrates lay on different structural domains.(ABSTRACT TRUNCATED AT 250 WORDS)