Spermadhesins: a new protein family. Facts, hypotheses and perspectives

Protein-Carbohydrate Interaction between Sperm and the Egg-Coating Envelope and Its Regulation by Dicalcin, a Xenopus laevis Zona Pellucida Protein-Associated Protein

Protein-carbohydrate interaction regulates multiple important processes during fertilization, an essential biological event where individual gametes undergo intercellular recognition to fuse and generate a zygote. In the mammalian female reproductive tract, sperm temporarily adhere to the oviductal epithelium via the complementary interaction between carbohydrate-binding proteins on the sperm membrane and carbohydrates on the oviductal cells. After detachment from the oviductal epithelium at the appropriate time point following ovulation, sperm migrate and occasionally bind to the extracellular matrix, called the zona pellucida (ZP), which surrounds the egg, thereafter undergoing the exocytotic acrosomal reaction to penetrate the envelope and to reach the egg plasma membrane. This sperm-ZP interaction also involves the direct interaction between sperm carbohydrate-binding proteins and carbohydrates within the ZP, most of which have been conserved across divergent species from mammals to amphibians and echinoderms. This review focuses on the carbohydrate-mediated interaction of sperm with the female reproductive tract, mainly the interaction between sperm and the ZP, and introduces the fertilization-suppressive action of dicalcin, a Xenopus laevis ZP protein-associated protein. The action of dicalcin correlates significantly with a dicalcin-dependent change in the lectin-staining pattern within the ZP, suggesting a unique role of dicalcin as an inherent protein that is capable of regulating the affinity between the lectin and oligosaccharides attached on its target glycoprotein.

Growth, testis size, spermatogenesis, semen parameters and seminal plasma and sperm membrane protein profile during the reproductive development of male goats supplemented with de-oiled castor cake

The present study was conducted to evaluate the effect of de-oiled castor cake on reproductive traits of crossbreed goats. Fourteen males were grouped into two lots (n = 7/group), as described: group without de-oiled castor cake (WCC) and group fed with de-oiled castor cake (CC). Goats received two diets containing a mixture of Bermudagrass hay and concentrates with the same energy (73% total digestive nutrients) and protein content (15% crude protein) during 150 days, corresponding to ages from 40 (puberty) to 60 weeks. Blood plasma concentrations of urea, albumin, lactate dehydrogenase, creatinine, alanine aminotransferase and testosterone were determined. We also evaluated scrotal circumference, sperm parameters, quantitative aspects of spermatogenesis and daily sperm production (DSP), as well as the proteome of seminal plasma and sperm membrane. Seminal fluid and sperm proteins were analyzed by 2D SDS-PAGE and mass spectrometry. After 150 days of castor cake feeding, animals had no changes in the biochemical composition of blood plasma, suggesting the absence of intoxication by ingestion of ricin. There were no alterations in dry mater intake, weight gain, testis size, peripheral concentrations of testosterone, sperm concentration, motility and morphology. Sertoli and germ cell populations in the testis and DSP were not affected either. However, there were significant variations in the expression of five seminal plasma proteins and four sperm membrane proteins. In conclusion, the replacement of soybean meal by castor cake (with ricin concentrations of 50mg/kg) did not interfere with the growth and core reproductive development of male goats. However, the diet with ricin altered the expression of certain seminal plasma and sperm membrane proteins, which play roles in sperm function and fertilization. Lower expression of these proteins may impair the ricin-fed animals to perform as high-fertility sires.

Boar sperm tyrosine phosphorylation patterns in the presence of oviductal epithelial cells: in vitro, ex vivo, and in vivo models

Spermatozoa transport through the oviduct is a controlled process that regulates sperm capacitation. A crucial event involved in capacitation is protein tyrosine phosphorylation (TP). This study was undertaken to determine whether similarities exist in protein TP distribution between spermatozoa bound or unbound to oviductal epithelial cells (OEC) in three different conditions: i)in vitro, spermatozoa coincubated with OEC cultures; ii)ex vivo, spermatozoa deposited in porcine oviductal explants from slaughtered animals; iii)in vivo, in which sows were inseminated and the oviduct was recovered. The localization of phosphotyrosine protein was determined using indirect immunofluorescence. The distribution of protein TP was significantly (P<0.05) different between bound and unbound cell populations in all experiments. In sows inseminated close to ovulation, spermatozoa were found mainly in the utero–tubal junction, where spermatozoa exhibited higher proportion of flagellum phosphorylation. Spermatozoa not bound to OEC exhibited high levels of protein phosphorylation (phosphorylated equatorial subsegment and acrosome and/or phosphorylated flagellum) in theex vivoandin vivoexperiments (P<0.05). However, unbound spermatozoa coincubated with OEC inin vitroconditions tended to show intermediate levels of TP (equatorial subsegment with or without phosphorylated flagellum). In spermatozoa bound to OEC, protein TP was located in the equatorial subsegment or presented no phosphorylation (P<0.05). Although sperm capacitation conditionsin vivowere not reproduciblein vitroin our experimental conditions, sperm and OEC binding seemed to be a mechanism for selecting spermatozoa with a low level of TP inin vivo,ex vivo, andin vitroexperiments.

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.

Proteomic characterization and cross species comparison of mammalian seminal plasma

Seminal plasma contains a large protein component which has been implicated in the function, transit and survival of spermatozoa within the female reproductive tract. However, the identity of the majority of these proteins remains unknown and a direct comparison between the major domestic mammalian species has yet to be made. As such, the present study characterized and compared the seminal plasma proteomes of cattle, horse, sheep, pig, goat, camel and alpaca. GeLC-MS/MS and shotgun proteomic analysis by 2D-LC-MS/MS identified a total of 302 proteins in the seminal plasma of the chosen mammalian species. Nucleobindin 1 and RSVP14, a member of the BSP (binder of sperm protein) family, were identified in all species. Beta nerve growth factor (bNGF), previously identified as an ovulation inducing factor in alpacas and llamas, was identified in this study in alpaca and camel (induced ovulators), cattle, sheep and horse (spontaneous ovulators) seminal plasma. These findings indicate that while the mammalian species studied have common ancestry as ungulates, their seminal plasma is divergent in protein composition, which may explain variation in reproductive capacity and function. The identification of major specific proteins within seminal plasma facilitates future investigation of the role of each protein in mammalian reproduction.

BIOLOGICAL SIGNIFICANCE

This proteomic study is the first study to compare the protein composition of seminal plasma from seven mammalian species including two camelid species. Beta nerve growth factor, previously described as the ovulation inducing factor in camelids is shown to be the major protein in alpaca and camel seminal plasma and also present in small amounts in bull, ram, and horse seminal plasma.

CUZD1 and anti-CUZD1 antibodies as markers of cancer and inflammatory bowel diseases

CUZD1, the CUB, and zona pellucida-like domains-containing protein 1, is a newly identified antigen of pancreatic autoantibodies (PAB) giving a reticulogranular pattern in patients with inflammatory bowel diseases, and in particular Crohn's disease. The exact mechanisms by which this pancreatic antigen becomes the target of IBD-specific pancreatic autoantibodies are unclear. At the same time, evolving data strongly support a role for CUZD1 in carcinogenesis. Human CUZD1 is mapped at chromosome 10q26.13 and the loss of this region is a frequent event in various malignant tumours. mRNA overexpression of CUZD1 has been noted in ovarian cancer and serum levels of CUZD1 are elevated in women with ovarian cancer and patients suffering from pancreatic cancer. CUZD1 appears to be one of the relatively few biomarkers that serve as both cancer biomarker and autoantigen of autoantibodies in an autoimmune disease unrelated to cancerous organs. This review discusses the role of CUZD1 in cancer and autoimmunity. We anticipate that a better understanding of the function of CUZD1 will help us to understand how it becomes the focus of an autoimmune attack specifically targeting the intestine and its enigmatic role in carcinogenesis.

Does Seminal Plasma PSP-I/PSP-II Spermadhesin Modulate the Ability of Boar Spermatozoa to Penetrate Homologous Oocytes In Vitro?

Low concentration (0.15 mg per million of spermatozoa) of seminal plasma-derived PSP-I/PSP-II spermadhesin heterodimer is able to preserve the viability of highly extended boar spermatozoa. Whether spermatozoa also keep their fertilizing capacity is not yet known. The present study evaluated the effect of exposing freshly extended and frozen-thawed boar spermatozoa (10 million/mL) to PSP-I/PSP-II (1.5 mg/mL) for 30 or 120 minutes on sperm characteristics and the outcome of in vitro penetration of immature (IM) and in vitro matured (IVM) homologous oocytes, aiming to identify this spermadhesin as a suitable modulator for sperm-handling protocols. Although exposure to the heterodimer improved sperm viability and motility without increasing the levels of sperm acrosome exocytosis in both freshly extended and frozen-thawed spermatozoa, this pretreatment did not affect sperm penetration rates or sperm numbers per oocyte when pretreated fresh spermatozoa were coincubated with IM or IVM oocytes compared with controls. When cryopreserved spermatozoa were tested, however, on IVM oocytes, already a 30-minute preincubation exposure to PSP-I/PSP-II showed a significant blocking effect on penetration rate (from 90% to 32%, P < .05) and on mean sperm numbers per oocyte (2.9 to 1.6, P < .05). To disclose the nature of this paradox, frozen-thawed spermatozoa were cleansed (by centrifugation in saline bovine serum albumin or through Percoll density gradient separation) and the procedure repeated. Oocyte penetration (but not number of spermatozoa per oocyte) increased (P < .05) when spermatozoa were cleansed with Percoll compared with either washed or unwashed controls (53% vs 13% vs 31%, respectively). In addition, the percentages of polyspermic oocytes remained lower than control (38.5% vs 68.7%, respectively; P < .05). In conclusion, the results confirm that exposure of fresh or frozen-thawed boar spermatozoa to a low dose of seminal PSP-I/PSP-II spermadhesin preserves sperm viability and motility in vitro. Although there was no obvious influence of the heterodimer on the capability of freshly extended boar spermatozoa to penetrate homologous oocytes (either IM or IVM), PSP-I/PSP-II exerted a deleterious effect when frozen-thawed spermatozoa were used to penetrate IVM oocytes. Such an effect of cryopreservation seems to a certain extent reversible, since cleansing of the sperm surface decreased, at least partially, this blocking effect, increasing both penetration and the monospermic rates.

Seminal plasma proteins as modulators of the sperm function and their application in sperm biotechnologies

Seminal plasma (SP) is known to play an important role in mammalian fertilization. However, the variability found in its composition among species, males and even fractions of the same ejaculate has made difficult to completely understand its effect in sperm function. Proteins are one of the major SP components that modulate sperm functionality. During the last years, intensive work has been performed to characterize the role of these proteins. They have been found to influence sperm capacitation, formation of the oviductal sperm reservoir and sperm-oocyte interaction. Sperm biotechnologies, such as sperm cryopreservation and flow cytometric sex-sorting, that involve a substantial dilution of the SP are detrimental to sperm quality. Attempts to improve the outcome of these biotechnologies include the restoration of SP, which has produced contradictory results. To overcome this variability, different research groups have proposed the application of isolated SP proteins. Herein, we will review the current knowledge in the role of the major SP proteins as modulators of sperm functionality. Furthermore, we will discuss the possible applications of the SP proteins in sperm cryopreservation and flow cytometric sex-sorting.

Biological markers of boar fertility

The semen evaluation techniques used in most commercial artificial insemination centers, which includes sperm motility and morphology measurements, provides a very conservative estimate of the relative fertility of individual boars. As well, differences in relative boar fertility are masked by the widespread use of pooled semen for commercial artificial insemination (AI) in many countries. Furthermore, the relatively high sperm numbers used in commercial AI practice usually compensate for reduced fertility, as can be seen in some boars when lower numbers of sperm are used for AI. The increased efficiency of pork production should involve enhanced use of boars with strong reproductive efficiency and the highest genetic merit for important production traits. Given that the current measures of semen quality are not always indicative of fertility and reproductive performance in boars, accurate and predictive genetic and protein markers are still needed. Recently, significant efforts have been made to identify reliable markers that allow for the identification and exclusion of sires with reduced reproductive efficiency. This paper reviews the current status of proteomic and genomic markers of fertility in boars in relation to other livestock species.

Expression, purification and structural analysis of recombinant rBdh-2His6, a spermadhesin from buck (Capra hircus) seminal plasma

Spermadhesins, a family of secretory proteins from the male genital tract of ungulate species, belong to the group of animal lectins. Spermadhesins have a prominent role in different aspects of fertilisation, such as spermatozoid capacitation, acrosomal stabilisation, sperm–oviduct interaction and during sperm–oocyte fusion. Proteins (spermadhesins) in buck seminal plasma were described. In the present study, bodhesin Bdh-2 cDNA present in buck seminal plasma was subcloned with the expression plasmid pTrcHis TOPO used to transform Escherichia coli Top10 One shot cells. The recombinant clones were selected by growth in 50 µg mL–1 ampicillin-containing LB broth and polymerase chain reaction amplification. Recombinant rBdh-2His6 synthesis was monitored by sodium dodecyl sulfate–polyacrylamide gel electrophoresis and followed by immunoblotting using monoclonal anti-His antibody. Production of rBdh-2 using low temperatures was not satisfactory. Greater production of rBdh-2 occurred with 1.5 mM isopropyl β-d-thiogalactoside after 2 h of induction. The method used to purify rBdh-2 was affinity chromatography on a His-Trap column following ion-exchange chromatography on a DEAE-Sephacel column. The secondary structure of the rBdh-2His6 was evaluated by spectral profile circular dichroism (CD). The prevalence of secondary structures like β-sheets, with fewer unfolded structures and α-helices, was confirmed. The structure of rBdh-2His6 remained stable up to 35°C. However, significant structural changes were observed at temperatures higher than 40°C related to a distortion of the CD spectrum.

Seminal plasma proteins: what role do they play?

PROBLEM

Semen is a heterogeneous and complex cell suspension in a protein-rich fluid with different functions, some of them well known, others still obscure.

METHOD OF STUDY

This paper reviews, comparatively, our current knowledge on the growing field of proteomics of the SP and its relevance in relation to the in vivo situation, for the sake of reproductive biology, diagnostics and treatment.

RESULTS

Ejaculated spermatozoa, primarily bathing in cauda epididymal fluid, are (in vitro) bulky, exposed to most, if not all, secretions from the accessory sexual glands. In vivo, however, not all spermatozoa are necessarily exposed to all secretions from these glands, because sperm cohorts are delivered in differential order and bathe in seminal plasma (SP) with different concentrations of constituents, including peptides and proteins. Proteins are relevant for sperm function and relate to sperm interactions with the various environments along the female genital tract towards the oocyte vestments. Specific peptides and proteins act as signals for the female immune system to modulate sperm rejection or tolerance, perhaps even influencing the relative intrinsic fertility of the male and/or couple by attaining a status of maternal tolerance towards embryo and placental development.

CONCLUSIONS

Proteins of the seminal plasma have an ample panorama of action, and some appear responsible for establishing fertility.

WITHDRAWN: Major proteins from the seminal plasma of adult Santa Ines rams

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Spatial and temporal expression of spermadhesin genes in reproductive tracts of male and female pigs and ejaculated sperm

Spermadhesins, a novel protein family identified in the reproductive tract of ungulates, have important roles in reproduction. In this study, the expression of pig (Sus domesticus) spermadhesion genes in seminal vesicles, prostate, and bulbourethral glands from birth to sexual maturity and the spatial expression in adult male and female genital tracts and ejaculated sperm of Meishan pigs were evaluated by reverse transcription-polymerase chain reaction (RT-PCR). In general, all spermadhesin genes increased from Days 1 to 150 in the seminal vesicle and bulbourethral gland. However, their expression in the prostate was variable; it increased from Days 1 to 60 and then declined until Day 150. In adult boars, all genes had a very high level of expression in the seminal vesicle and somewhat lower (but still relatively high) in the prostate, caput and caudal epididymides, and bulbourethral gland. Expression of AQN1 and AQN3 was not detectable in the corpus epididymis. In the testis, AQN3 gene expression was not detectable, and gene expressions were weak for AQN1, PSP-I, and PSP-II, but strong for AWN. In female pigs, most spermadhesins had low expression in the cervix, uterine horn, oviduct, and ovary. Expression of AQN1 and AQN3 was very weak in the cervix and uterine horn. Signals for AQN1 in oviduct and ovary and AQN3 in ovary were not detectable, whereas AWN had high expression in the cervix and uterine horn. In ejaculated sperm, a strong mRNA signal of spermadhesins was detected. We concluded that transcripts of spermadhesins were not only distributed extensively in male and female reproductive tissues but also in ejaculated sperm. Furthermore, their dynamic changes of expression paralleled reproductive development. Seminal vesicles were the main source of spermadhesins; when the boar reached puberty, expression of spermadhesins reached very high levels.

Seminal plasma proteins inhibit in vitro- and cooling-induced capacitation in boar spermatozoa

Dilute boar seminal plasma (SP) has been shown to inhibit in vitro capacitation and cooling-induced capacitation-like changes in boar spermatozoa, as assessed by the ability of the spermatozoa to undergo an ionophore-induced acrosome reaction. We hypothesised that the protein component of SP is responsible for this effect. To test this hypothesis, varying concentrations of total SP protein or SP proteins fractionated by heparin binding were assayed for their ability to inhibit in vitro capacitation, as well as cooling- and cryopreservation-induced capacitation-like changes. In vitro capacitation and cooling-induced capacitation-like changes were prevented by 10% whole SP, as well as by total proteins extracted from SP at concentrations greater than 500 μg mL−1. No amount of SP protein was able to prevent cryopreservation-induced capacitation-like changes. Total SP proteins were fractionated based on their heparin-binding properties and the heparin-binding fraction was shown to possess capacitation inhibitory activity at concentrations as low as 250 µg mL−1. The proteins in the heparin-binding fraction were subjected to mass spectrometry and identified. The predominant proteins were three members of the spermadhesin families, namely AQN-3, AQN-1 and AWN, and SP protein pB1. We conclude that one or more of these heparin-binding SP proteins is able to inhibit in vitro capacitation and cooling-induced capacitation-like changes, but not cryopreservation-induced capacitation-like changes, in boar spermatozoa.

Sperm-zona pellucida interaction: molecular mechanisms and the potential for contraceptive intervention

At the moment of insemination, millions of mammalian sperm cells are released into the female reproductive tract with the single goal of finding the oocyte. The spermatozoa subsequently ignore the thousands of cells they make contact with during their journey to the site of fertilization, until they reach the surface of the oocyte. At this point, they bind tenaciously to the acellular coat, known as the zona pellucida, which surrounds the oocyte and orchestrate a cascade of cellular interactions that culminate in fertilization. These exquisitely cell- and species- specific recognition events are among the most strategically important cellular interactions in biology. Understanding the cellular and molecular mechanisms that underpin them has implications for the etiology of human infertility and the development of novel targets for fertility regulation. Herein we describe our current understanding of the molecular basis of successful sperm-zona pellucida binding.

Identifying useable semen

The "predictors of useable semen" used in most commercial AI centers provide a very conservative estimate of the relative fertility of individual boars. Furthermore, the relatively high sperm numbers used in commercial AI practice (usually >3 x10(9) total sperm per dose of extended semen) usually compensate for reduced fertility, as can be demonstrated in some boars when lower numbers of sperm are used for AI. Differences in relative boar fertility are also masked by the widespread use of pooled semen for commercial AI in many countries. However, the need to continually improve the efficiency of pork production, suggests that commercial AI practice should involve increased use of boars with the highest genetic merit for important production traits. Necessarily, this must be linked to the use of fewer sperm per AI dose, fewer inseminations per sow bred, and hence more sows bred by these superior sires. In turn, this requires improved techniques for evaluating semen characteristics directly related to the fertilization process, such as IVM-IVF assays, analysis of seminal plasma protein markers, more discriminatory tests of sperm motility and morphology, with the goal of identifying high-index boars whose fertility is sustained when low numbers of sperm are used for AI. This paper reviews the current status of laboratory-based boar semen evaluation techniques that meet these criteria.

Localization and expression of spermadhesin PSP-I/PSP-II subunits in the reproductive organs of the boar

The epithelial localization and expression of the spermadhesin PSP-I and PSP-II subunits were determined in the testis, ductus epididymes (caput, corpus and cauda), seminal vesicles and bulbourethral glands of mature boars, using immunohistochemical, western blotting and RT-PCR methods. Immunohistochemistry showed positive labelling for PSP-I and PSP-II antibodies in the epithelium of seminal vesicles in all males tested. Positive immunolabelling, but with variable intensity, was also present in the epididymal epithelium (caput, corpus and cauda), although varying largely among segments and boars. Immunoreactivity was nearly or completely absent in the seminiferous epithelium and the bulbourethral gland, although SDS-PAGE and western blotting revealed the presence of PSP-I and PSP-II immunoreactive bands in all the tissue extracts, including the testis and the bulbourethral gland. mRNA amplification by RT-PCR using primers specific for PSP-I and PSP-II showed a trend similar to that observed for western blotting, i.e. intensity variation between tissues (even between segments of the same epididymis) and among boars. Our results indicate that the seminal vesicles are the main source of PSP-I and PSP-II spermadhesins, although epididymal segments, testis and the bulbourethral gland also participate in the expression of both proteins.

Macaque sperm coating protein DEFB126 facilitates sperm penetration of cervical mucus

BACKGROUND

Sperm coating protein beta-defensin 126 (DEFB126) is adsorbed onto the entire surface of macaque sperm in the caudal epididymis and is retained on viable sperm collected from the cervix and the uterine lumen of mated female macaques. We investigated the role of sperm coating protein DEFB126 in cervical mucus penetration (CMP).

METHODS

Cervical mucus (CM) was collected from peri-ovulatory female macaques and loaded into CMP chambers. Sperm were introduced to CMP chambers following treatment with either polyclonal antibodies raised to DEFB126 or seminal plasma proteins (SPPs), 1 mM caffeine+1 mM dibutyryl cyclic adenosine monophosphate (dbcAMP) (induces release of DEFB126 from sperm surface), neuraminidase (NMase) or poly-L-lysine (PLP). Following removal of DEFB126 or SPPs from the sperm surface, sperm were treated with concentrated DEFB126 or concentrated SPPs prior to being introduced to CMP chambers. The numbers of sperm that penetrated and traversed CM were scored over 6 min.

RESULTS

Treatment of sperm with anti-DEFB126 antibodies, 1 mM caffeine+1 mM dbcAMP, NMase, and PLP resulted in similar and significant levels of inhibition of sperm CMP, whereas addition of anti-SPPs antibodies had no effect. In experiments where DEFB126 and SPPs were removed, CMP capability of sperm was restored by addition of DEFB126 back to the sperm surface, whereas treatment of sperm with concentrated SPPs slightly inhibited sperm penetration.

CONCLUSIONS

DEFB126 and its high negative charge appears to be critical for the movement of sperm through CM in the macaque, while SPPs adhered to the sperm surface offer no advantage in CMP.

beta-Microseminoprotein in human spermatozoa and its potential role in male fertility

beta-Microseminoprotein (MSMB) is one of the most abundant proteins in human seminal plasma. The objectives of this study were: (1) to purify MSMB from seminal plasma (SP) and generate antibodies against the pure protein; (2) to investigate the interaction of MSMB with ejaculated spermatozoa and its possible effect on the spontaneous acrosome reaction (AR); and (3) to quantify MSMB content in SP and examine its relationship with the clinical sperm parameters. MSMB was purified from SP and its presence on the sperm surface was examined by indirect immunofluorescence using a specific polyclonal antibody. The effect of MSMB on the AR was evaluated using guinea pig epididymal spermatozoa as a model. MSMB quantification assay was performed with a two-site binding ELISA using two polyclonal antibodies against MSMB. MSMB was assessed in semen samples from fertile donors (controls) and subfertile patients according to World Health Organization criteria. MSMB was detected on the sperm surface and mainly localized to the acrosomal region of the head and neck. A significant spontaneous AR inhibition was observed when guinea pig epididymal spermatozoa were preincubated with MSMB. Finally, MSMB was significantly increased in subfertile patients when compared with fertile controls (P<0.02). The association of MSMB to the sperm surface, the inhibitor effect on the spontaneous AR and the increased MSMB levels found in SP in subfertile men suggests a relationship between this protein and semen quality and a possible role in the process of fertilization.

Evolution of polydom-like molecules: identification and characterization of cnidarian polydom (Cnpolydom) in the basal metazoan Hydractinia

End sequencing of random BAC clones from a Hydractinia symbiolongicarpus (Cnidaria: Hydrozoa) genomic library revealed a gene across a approximately 37.5kb region of the H. symbiolongicarpus genome sharing highest sequence identity and domain architecture to mammalian polydom that we in turn named cnidarian polydom (CnPolydom). Sharing all eight domain types characteristic of polydom and organized in a similar 5'-3' manner, CnPolydom was predicted to contain three additional domain types: PAN, FA58C, and CUB that are characteristic of CnPolydom. Expression analysis of CnPolydom from H. symbiolongicarpus (Hysy-CnPolydom) showed upregulation in response to bacterial and primarily fungal challenges, with transcripts produced specifically by a subset of interstitial stem cells (i-cells) and/or neural cells throughout the ectodermal tissue layer of feeding polyps (gastrozooids). This is the first description of a polydom-like molecule outside of Mammalia and provides evolutionary perspective on the ancestral structure and role of this pentraxin family clade.

PSP-I/PSP-II spermadhesin exert a decapacitation effect on highly extended boar spermatozoa

PSP-I/PSP-II heterodimer is a major protein of boar seminal plasma that is able to preserve, in vitro, the viability, motility and mitochondrial activity of highly-extended boar spermatozoa. However, a relationship between the protective effects of the heterodimer and sperm capacitation is still unclear. The present study investigated the effect of the PSP-I/PSP-II (1.5 mg/mL) on membrane stability, intracellular calcium concentration ([Ca(2+)](I)) and plasma membrane and acrosome integrity of highly extended boar spermatozoa. Boar spermatozoa were diluted to 1 x 10(6) spermatozoa/mL and incubated at 38 degrees C in Phosphate-buffered saline (PBS) for 10, 30, 60, 120 and 300 min or in modified Tris-buffered medium (mTBM) for 10, 20, 30, 60 and 120 min. After each incubation time, the membrane stability (using Merocyanine-540/Yo-Pro-1), elevation of [Ca(2+)](I) (using Fluo-3-AM/PI) and the sperm plasma membrane and acrosome integrity (using SYBR-14/PI/PE-PNA) were evaluated by flow cytometry. As expected, exposure of the spermatozoa to the PSP-I/PSP-II preserved the plasma membrane and acrosome integrity compared to non-exposed spermatozoa in both media PBS and mTBM (p < .01). The evaluation of membrane stability showed no differences in the percentages of viable sperm with instable plasma membrane in the presence of the PSP-I/PSP-II compared to controls irrespective of the dilution media. The evaluation of the [Ca(2+)](I) levels showed that while spermatozoa incubated in mTBM and exposed to PSP-I/PSP-II had lower [Ca(2+)](I) than controls (39.08% vs. 47.97%, respectively; p < .05), no differences were observed in those samples incubated in PBS. However, a temporal evaluation of the samples showed that a similar proportion of live spermatozoa were able to achieve high levels of [Ca(2+)](I) and membrane instability independent of the presence of PSP-I/PSP-II. In conclusion, PSP-I/PSP-II exert a non-permanent decapacitation effect on highly extended boar spermatozoa that is related with a delay in the increase of [Ca(2+)](I) levels.

Seminal plasma non-heparin binding proteins (NHBP) reduce the cryoinjury to buffalo cauda epididymal spermatozoa induced by heparin binding proteins (HBP)

Previous cryopreservation studies with buffalo cauda epididymal spermatozoa have reported a deleterious effect of seminal plasma heparin binding protein (HBP). The amount of HBP used in these studies was meager compared to the normal level of HBP in the buffalo ejaculate, still the damage induced upon the spermatozoa was substantial when compared to that incurred to the spermatozoa during routine freezing of ejaculated semen. Thus there might be some factor(s) in the seminal plasma, which reduce the deleterious effect of HBP on spermatozoa during cryopreservation of ejaculated semen. This study was conducted to investigate for the presence of any such factor in buffalo seminal plasma. Seminal plasma proteins were separated on their heparin binding properties as heparin binding (HBP) and non-heparin binding (NHBP). The separated proteins were added to the extender of buffalo cauda epididymal semen for cryopreservation either alone or in combination. The spermatozoa were assessed for progressive motility, viability, acrosomal integrity and response to hypo-osmotic solution test (HOST) at prefreeze and post-thaw stages of cryopreservation. NHBP was found to provide some degree of protection to buffalo spermatozoa against cryopreservation stress as well as the deleterious effect of HBP during cryopreservation.

Current concepts of molecular events during bovine and porcine spermatozoa capacitation

Spermatozoa are required to undergo the processes of capacitation before they obtain fertilizing ability. The molecular changes of capacitation are still not fully understood. However, it is accepted that capacitation is a sequential process involving numerous physiological changes including destabilization of the plasma membrane, alterations of intracellular ion concentrations and membrane potential, and protein phosphorylation. There are no known morphological changes that occur to the spermatozoon during capacitation. The purpose of this review is to summarize current evidence on the molecular aspects of capacitation both in vivo and in vitro in bovine and porcine spermatozoa. For the purpose of this review, the process of sperm capacitation will encompass maturational events that occur following ejaculation up to binding to the zona pellucida, that triggers acrosomal exocytosis and initiates fertilization.

Multiple proteins present in purified porcine sperm apical plasma membranes interact with the zona pellucida of the oocyte

An important step in fertilization is the recognition and primary binding of the sperm cell to the zona pellucida (ZP). Primary ZP binding proteins are located at the apical plasma membrane of the sperm head. In order to exclusively study primary zona binding proteins, plasma membranes of sperm heads were isolated, highly purified and subsequently solubilized with a mild or a strong solubilization procedure. Native, highly purified ZP ghosts were used as the binding substrate for solubilized sperm plasma membrane proteins, and a proteomic approach was employed to identify ZP binding proteins. Two-dimensional gel electrophoresis of ZP fragments with bound sperm proteins showed very reproducibly 24 sperm protein spots to be associated to the zona ghosts after mild plasma membrane solubilization whereas only three protein spots were detected after strong plasma membrane solubilization. This indicates the involvement of multiple sperm proteins in ZP binding. The three persistently bound proteins were identified by a tandem mass spectrometry as isoforms of AQN-3 and probably represent the main sperm protein involved in ZP binding. P47, fertilin beta and peroxiredoxin 5 were also conclusively identified. None of the identified proteins has a known acrosomal origin, which further indicated that there was no sample contamination with secondary ZP binding proteins from the acrosomal matrix. In this study, we showed and identified multiple zona binding proteins involved in primary sperm-zona binding. Although we were not able to identify all of the proteins involved, this is a first step in understanding the event of primary sperm-zona interactions and the relevance of this for fertilization is discussed.

Insights into how CUB domains can exert specific functions while sharing a common fold: conserved and specific features of the CUB1 domain contribute to the molecular basis of procollagen C-proteinase enhancer-1 activity

Procollagen C-proteinase enhancers (PCPE-1 and -2) are extracellular glycoproteins that can stimulate the C-terminal processing of fibrillar procollagens by tolloid proteinases such as bone morphogenetic protein-1. They consist of two CUB domains (CUB1 and -2) that alone account for PCPE-enhancing activity and one C-terminal NTR domain. CUB domains are found in several extracellular and plasma membrane-associated proteins, many of which are proteases. We have modeled the structure of the CUB1 domain of PCPE-1 based on known three-dimensional structures of CUB-containing proteins. Sequence alignment shows conserved amino acids, notably two acidic residues (Asp-68 and Asp-109) involved in a putative surface-located calcium binding site, as well as a conserved tyrosine residue (Tyr-67). In addition, three residues (Glu-26, Thr-89, and Phe-90) are found only in PCPE CUB1 domains, in putative surface-exposed loops. Among the conserved residues, it was found that mutations of Asp-68 and Asp-109 to alanine almost completely abolished PCPE-1 stimulating activity, whereas mutation of Tyr-67 led to a smaller reduction of activity. Among residues specific to PCPEs, mutation of Glu-26 and Thr-89 had little effect, whereas mutation of Phe-90 dramatically decreased the activity. Changes in activity were paralleled by changes in binding of different PCPE-1 mutants to a mini-procollagen III substrate, as shown by surface plasmon resonance. We conclude that PCPE-stimulating activity requires a calcium binding motif in the CUB1 domain that is highly conserved among CUB-containing proteins but also that PCPEs contain specific sites that could become targets for the development of novel anti-fibrotic therapies.

Origin, localization and binding abilities of boar DQH sperm surface protein tested by specific monoclonal antibodies

Seminal plasma proteins bind the sperm surface at ejaculation and may modulate several aspects of sperm activity during reproduction. DQH sperm surface protein, present in boar seminal plasma, shows affinity to phoshorylcholine, acidic polysaccharides, oviductal epithelium and zona pellucida glycoproteins. Monoclonal antibodies (MAbs) against DQH protein were prepared and used for determination of the DQH protein origin in boar reproductive organs, its localization on boar spermatozoa, and for investigation of its binding abilities in the porcine oviduct and to the zona pellucida of the oocyte. The mRNA transcript of DQH protein was found in seminal vesicles and not in the testis, epididymis and prostate. Its translated products were immunodetected by MAbs in seminal vesicle extract and fluid, in seminal vesicle tissue sections and on the membrane-associated acrosomal part of ejaculated spermatozoa. These results confirm the ability of DQH protein to bind the sperm surface at ejaculation and to participate in formation of the sperm reservoir in the porcine oviduct. Moreover, monoclonal antibodies reduced binding of sperm to oocytes and proved the role of DQH protein in the sperm-zona pellucida primary binding.

Buck (Capra hircus) genes encode new members of the spermadhesin family

Spermadhesins are the major proteins of boar seminal plasma and form a group of polypeptides probably involved in reproduction. In previous work, a member of the spermadhesin family from buck seminal plasma, called BSFP, was characterized by mass spectrometry and N-terminal sequencing. The present study aimed to clone and characterize the BSFP gene and investigate its expression along the genital tract using real-time polymerase chain reaction (PCR). The cDNAs of the seminal vesicle, testis, epididymis, bulbourethral gland, and ductus deferens were prepared from a buck. Following 3'- and 5'-end amplifications using seminal vesicle cDNA, we cloned and sequenced four highly similar (97-98%) nucleotide sequences encoding spermadhesins, which were named Bodhesin-1(Bdh-1), Bdh-2, Bdh-3, and Bdh-4. All deduced amino acid sequences contained the CUB domain signature and were 49-52% similar to boar AWN. Among the four Bdh amino acid sequences, Bdh-2 was the most similar to the BSFP N-terminal fragment. By using real-time PCR, it was verified specific amplifications for all Bdh in the seminal vesicle, testis, epididymis, and bulbourethral gland, with the exception of Bdh-2 in epididymis. The amplicons had a melting temperature and size of approximately 78 degrees C and 130 bp, respectively. Bdh expression was higher in the seminal vesicle when compared to the other tissues. The present work confirms that goat is the fifth mammalian species, after pig, cattle, horse, and sheep, in which spermadhesin molecules are found. To the best of our knowledge, this is the first report on buck spermadhesin genes using molecular cloning and expression profile.

Rendezvin: An essential gene encoding independent, differentially secreted egg proteins that organize the fertilization envelope proteome after self-association

Preventing polyspermy during animal fertilization relies on modifications to the egg's extracellular matrix. On fertilization in sea urchins, the contents of cortical granules are secreted and rapidly assemble into the egg's extracellular vitelline layer, forming the fertilization envelope, a proteinaceous structure that protects the zygote from subsequent sperm. Here, we document rendezvin, a gene whose transcript is differentially spliced to yield proteins destined for either cortical granules or the vitelline layer. These distinctly trafficked variants reunite after cortical granule secretion at fertilization. Together, they help coordinate assembly of the functional fertilization envelope, whose proteome is now defined in full.

An assay for bacterial and eukaryotic chondroitinases using a chondroitin sulfate-binding protein

A simple, rapid, and reproducible microtiter-based chondroitinase (CSase) assay is reported here, based on the competition of chondroitin sulfate (CS) with immobilized hyaluronan (HA) for the binding of TSG-6 protein, the product of TNF-inducible gene 6. Although the catabolic reaction of bacterial and other prokaryotic CSase enzymes, often referred to as the chondroitin lyases, can be followed by tracking the generation of unsaturated bonds by the spectrophotometrical determination of the absorbance at 232 nm, no rapid, sensitive, and simple assay has been devised to date for measuring the activity of the vertebrate enzymes that cleave their substrate exclusively by hydrolysis. We provide data demonstrating that the CSase assay described here is suitable for the determination of the activities of both classes of enzymes. For the bacterial enzyme CSase ABC, both the determination of the absorbance at 232 nm and the assay based on TSG-6 binding are suitable using the same range of enzyme activities. However, for testicular hyaluronidase, considerably higher enzyme activities were needed to cleave CS than to cleave HA. Using the HA-binding domain of aggrecan for a comparison, we determined that the interaction between TSG-6 and chondroitin sulfate is uniquely suited for this CSase assay.

Analysis of the stability of the spermadhesin PSP-I/PSP-II heterodimer. Effects of Zn2+ and acidic pH

Spermadhesins are a family of 12-16 kDa proteins with a single CUB domain. PSP-I and PSP-II, the most abundant boar spermadhesins, are present in seminal plasma as a noncovalent heterodimer. Dimerization markedly affects the binding ability of the subunits. Notably, heparin and mannose 6-phosphate binding abilities of PSP-II are abolished, indicating that the corresponding binding sites may be located at (or near) the dimer interface. Pursuing the hypothesis that cryptic binding sites in PSP-I/PSP-II may be exposed in specific physiological environments, we examined the influence of Zn2+ and acidic pH on the heterodimer stability. According to near-UV CD spectra, the core native fold is preserved in the presence of physiological concentrations of Zn2+, a cation unusually abundant in boar seminal plasma. However, the thermostability of the heterodimer decreases significantly, as observed by CD and differential scanning calorimetry. The effect is Zn2+-specific and is reversed by EDTA. Destabilization is also observed at acidic pH. Gel filtration analysis using radioiodinated PSP-I/PSP-II reveals that dissociation of the heterodimer at low (nanomolar) protein concentrations is promoted by both Zn2+ and acidic pH. Although the integrity of the heterodimer in seminal plasma seems to be guaranteed by its high concentration, dissociation may be facilitated in the female genital tract because of dilution of the protein in the intraluminal fluids of the cervix and the uterus, and the acidic fluid of the uterotubal junction. Such a mechanism may be relevant in the regulation of uterine immune reactions.

The role of stallion seminal proteins in fertilisation

Seminal plasma proteins are secretory proteins originating mainly from the epididymis and the accessory sex glands. They are involved in the remodelling of the sperm surface which occurs during sperm transit through the male genital tract and continues later at ejaculation. During this process, collectively called post-testicular sperm maturation, the spermatozoa acquire the ability to fertilise an egg. Seminal plasma proteins have been shown to contribute to early and central steps of the fertilisation sequence, e.g. the establishment of the oviductal sperm reservoir, modulation of capacitation and gamete interaction. The major equine seminal plasma proteins belong to three protein classes, which contain widely occurring protein modules. Fn-2 type proteins are characterised by two or four tandemly arranged Fn-2 modules and have been implicated in the modulation of sperm capacitation. Multiple members of the cysteine-rich secretory proteins (CRISP) have been identified in the male genital tract of a number of species. CRISP proteins have been shown to be involved in various functions related to sperm-oocyte fusion, innate host defense function and ion channel blockage. Spermadhesins occur only in ungulate species. Their carbohydrate- and zona pellucida-binding properties would suggest a role of these proteins in gamete recognition. The major proteins of equine seminal plasma have been isolated and characterised regarding their expression along the male genital tract, protein structure and their functions.

The role of molecular chaperones in mouse sperm-egg interactions

Fertilization is a unique and exquisitely choreographed cellular interaction between the male and female gamete that results in the creation of a genetically unique individual. Despite the fundamental importance of fertilization, there remains a dearth of information about the basic biochemical mechanisms that underpin this process. One of the key issues that remain unresolved is the molecular basis of sperm-egg recognition. From the female perspective, it is well established that the sperm recognition sites reside in the zona pellucida (ZP), an acellular coat that surrounds the oocyte. In contrast, numerous studies into the cognate zona receptors residing on the sperm surface have failed to shed significant light on the biochemical identity of these molecules. Such difficulties may, in part, have arisen because investigations have traditionally been based on the precept that the zona receptor represents a single molecular entity that is constitutively expressed on the sperm surface. While such a view holds obvious appeal, it fails to account for growing evidence that gamete interaction is not mediated by a simple lock-and-key mechanism. In this review, we present a novel hypothesis in which the zona recognition site is portrayed as a multimeric molecular structure that is assembled into a functional complex during a maturation process known as 'capacitation'. Furthermore, we consider the possibility that this previously cryptic complex is assembled and delivered to the outer surface of the sperm plasma membrane through the concerted action of several members of the molecular chaperone family of proteins.