The role of Zn-alpha2 glycoprotein in sperm motility is mediated by changes in cyclic AMP

Effects of Cryptorchidism on the Semen Quality of Giant Pandas from the Perspective of Seminal Plasma Proteomics

Giant pandas are an endangered species with low reproductive rates. Cryptorchidism, which can negatively affect reproduction, is also often found in pandas. Seminal plasma plays a crucial role in sperm-environment interactions, and its properties are closely linked to conception potential in both natural and assisted reproduction. The research sought to identify seminal fluid protein content variations between normal and cryptorchid giant pandas. Methods: Using a label-free MS-based method, the semen proteomes of one panda with cryptorchidism and three normal pandas were studied, and the identified proteins were compared and functionally analyzed. Results: Mass spectrometry identified 2059 seminal plasma proteins, with 361 differentially expressed proteins (DEPs). Gene ontology (GO) analysis revealed that these DEPs are mainly involved in the phosphate-containing compound metabolic, hydrolase activity, and kinase activity areas (p ≤ 0.05). The KEGG functional enrichment analysis revealed that the top 20 pathways were notably concentrated in the adipocyte lipolysis and insulin metabolism pathway, with a significance level of p ≤ 0.05. Further analysis through a protein-protein interaction (PPI) network identified nine key proteins that may play crucial roles, including D2GXH8 (hexokinase Fragment), D2HSQ6 (protein tyrosine phosphatase), and G1LHZ6 (Calmodulin 2). Conclusions: We suspect that the high abundance of D2HSQ6 in cryptorchid individuals is associated with metabolic pathways, especially the insulin signal pathway, as a typical proteomic feature related to its pathological features. These findings offer insight into the ex situ breeding conditions of this threatened species.

Protein Identification of Seminal Plasma in Bali Bull (Bos javanicus)

The purpose of this study was to identify seminal plasma proteins in Bali bull and their potential as biomarkers of fertility. Semen was collected from 10 bulls aged 5-10 years using an artificial vagina. Fresh semen was then centrifuged (3000× g for 30 min). The supernatant was put into straws and stored in liquid nitrogen. The semen plasma protein concentration was determined using the Bradford method, and the protein was characterized using 1D-SDS-PAGE. Coomassie Brilliant Blue (CBB) was used to color the gel, and the molecular weight of the protein was determined using PM2700. A total of 94 proteins were identified in the seminal plasma of Bali bulls analyzed using LC-MS/MS (liquid chromatography-mass spectrometry). Proteins spermadhesin 1 (SPADH1), C-type natriuretic peptide (NPPC), clusterin (CLU), apoliprotein A-II (APOA2), inositol-3-phosphate synthase 1 (ISYNA1), and sulfhydryl oxidase 1 (QSOX1) were identified as important for fertility in Bos javanicus. These proteins may prove to be important biomarkers of fertility in Bali bulls. These proteins are important for reproductive function, which includes spermatozoa motility, capacitation, and acrosome reactions. This study provides new information about the protein content in seminal plasma in Bali bulls. The LC-MS/MS-based proteome approach that we applied in this study obtained 94 proteins. The identification of these seminal plasma proteins of Bali bulls and their potential as fertility biomarkers may have an impact on the success of future artificial insemination (AI).

What is the relevance of seminal plasma from a functional and preservation perspective?

When preserving sperm in the liquid or cryopreserved state, seminal plasma (SP) components within ejaculates can alter fertilizing capacity of these gametes. Depending on the species or how semen is collected, volume and concentration of SP components varies considerably. The SP contains substances essential for maintenance of sperm viability and fertility; however, these components can be deleterious depending on quantity, or duration of time before there is removal of SP from sperm in semen processing. Substances that impair (e.g., BSP - bull; HSP-1 - stallion; Major seminal plasma protein PSPI - boar) or improve (e.g., spermadhesin PSP-I - boar) spermatozoa fertilizing capacity have been identified. Depending on individual males, species, and semen collection procedures, SP removal may be beneficial before preservation in the liquid or cryopreserved state. In some cases, SP that is removed can be added back to thawing extender with there being positive effects in thawed sperm and for sperm viability in the female reproductive tract. In this review article, there is a focus on different effects of SP in samples of cooled and cryopreserved semen from four domestic species (pigs, horses, cattle, and sheep) with there being emphasis on how SP modulates the function and morphology of sperm cells before, during, and after preservation in the refrigerated or cryopreserved state. The present review is part of the Festschrift in honor of Dr. Duane Garner who made major contributions to the area of focus in this manuscript as evidenced by the many times his research is cited in this manuscript.

Taxifolin increased semen quality of Duroc boars by improving gut microbes and blood metabolites

Taxifolin (TAX), as a natural flavonoid, has been widely focused on due to its strong anti-oxidation, anti-inflammation, anti-virus, and even anti-tumor activity. However, the effect of TAX on semen quality was unknown. The purpose of this study was to analyze the beneficial influences of adding feed additive TAX to boar semen in terms of its quality and potential mechanisms. We discovered that TAX increased sperm motility significantly in Duroc boars by the elevation of the protein levels such as ZAG, PKA, CatSper, and p-ERK for sperm quality. TAX increased the blood concentration of testosterone derivatives, antioxidants such as melatonin and betaine, unsaturated fatty acids such as DHA, and beneficial amino acids such as proline. Conversely, TAX decreased 10 different kinds of bile acids in the plasma. Moreover, TAX increased "beneficial" microbes such as Intestinimonas, Coprococcus, Butyrivibrio, and Clostridium_XlVa at the Genus level. However, TAX reduced the "harmful" intestinal bacteria such as Prevotella, Howardella, Mogibacterium, and Enterococcus. There was a very close correlation between fecal microbes, plasma metabolites, and semen parameters by the spearman correlation analysis. Therefore, the data suggest that TAX increases the semen quality of Duroc boars by benefiting the gut microbes and blood metabolites. It is supposed that TAX could be used as a kind of feed additive to increase the semen quality of boars to enhance production performance.

A comparative proteomic study of high and low semen quality seminal plasma in drakes

Semen quality is the most important indicator in evaluating drake fecundity. At present, the low semen quality has become a major factor restricting the development of artificial insemination (AI) technology in ducks. Numerous studies have indicated that seminal plasma proteins play a crucial role in semen quality, but the mechanism of seminal plasma proteins regulating semen quality of drakes remains unclear. Thus, the objective of this study was to identify seminal plasma proteins associated with semen quality by comparing the seminal plasma proteomic profile of drakes with high-quality semen (HQS) and low-quality semen (LQS). Using a label-free MS-based method, a total of 745 seminal plasma proteins were identified. Of these, 55 differentially expressed proteins (DEPs) were identified (40 up-regulated and 15 down-regulated). Gene Ontology (GO) analysis showed that the DEPs were mainly enriched in transmembrane transport, extracellular matrix structural constituent, transferase activity, transferring acyl groups other than amino-acyl groups, transmembrane transporter activity, and integral component of membrane (P < 0.05). Kyoto Encyclopedia of Genes and Genomes (KEGG) functional enrichment analysis indicated that the DEPs were significantly enriched in apoptosis, tyrosine metabolism, glycerophospholipid metabolism, and sulfur metabolism pathways (P < 0.05). Moreover, through protein-protein interaction (PPI) network analysis, eight potential candidate proteins were identified, including P19140 (Alpha-enolase), R0KUV7 (Calreticulin), R0K3X3 (Solute carrier family 2, facilitated glucose transporter member 5), R0L6V0 (Proteasome subunit beta), R0JKW0 (Cytochrome c), R0JMC5 (Tubulin alpha chain), R0LCK1 (Cathepsin C), and R0JUP6 (Cathepsin D), which could play crucial roles in semen quality. Notably, further analysis demonstrated that key protein P19140 (Alpha-enolase) might can control the semen quality of drakes by regulating the expression of proteins related to apoptosis pathway. This study is the first systematically comparing the seminal plasma proteome of drakes exhibiting high and low semen quality. These results provide novel insights into the mechanisms regulating semen quality of drakes.

Hydroxytyrosol Benefits Boar Semen Quality via Improving Gut Microbiota and Blood Metabolome

Semen quality is one of the most important factors for the success of artificial insemination which has been widely applied in swine industry to take the advantages of the superior genetic background and higher fertility capability of boars. Hydroxytyrosol (HT), a polyphenol, has attracted broad interest due to its strong antioxidant, anti-inflammatory, and antibacterial activities. Sperm plasma membrane contains a large proportion of polyunsaturated fatty acids which is easily impaired by oxidative stress and thus to diminish semen quality. In current investigation, we aimed to explore the effects of dietary supplementation of HT on boar semen quality and the underlying mechanisms. Dietary supplementation of HT tended to increase sperm motility and semen volume/ejaculation. And the follow-up 2 months (without HT, just basal diet), the semen volume was significantly more while the abnormal sperm was less in HT group than that in control group. HT increased the “beneficial microbes” Bifidobacterium, Lactobacillus, Eubacterium, Intestinimonas, Coprococcus, and Butyricicoccus, however, decreased the relative abundance of “harmful microbes” Streptococcus, Oscillibacter, Clostridium_sensu_stricto, Escherichia, Phascolarctobacterium, and Barnesiella. Furthermore, HT increased plamsa steroid hormones such as testosterone and its derivatives, and antioxidant molecules while decreased bile acids and the derivatives. All the data suggest that HT improves gut microbiota to benefit plasma metabolites then to enhance spermatogenesis and semen quality. HT may be used as dietary additive to enhance boar semen quality in swine industry.

Identification of diverse lipid-binding modes in the groove of zinc α2 glycoprotein reveals its functional versatility

ZAG is a multifunctional glycoprotein with a class I MHC-like protein fold and an α1-α2 lipid-binding groove. The intrinsic ZAG ligand is unknown. Our previous studies showed that ZAG binds the dansylated C₁₁ fatty acid, DAUDA, differently to the boron dipyrromethane C₁₆ fatty acid, C₁₆ -BODIPY. Here, the molecular basis for this difference was elucidated. Multi-wavelength analytical ultracentrifugation confirmed that DAUDA and C₁₆ -BODIPY individually bind to ZAG and compete for the same binding site. Molecular docking of lipid-binding in the structurally related Cluster of differentiation 1 proteins predicted nine conserved ligand contact residues in ZAG. Twelve mutants were accordingly created by alanine scanning site directed mutagenesis for characterisation. Mutation of Y12 caused ZAG to misfold. Mutation of K147, R157 and A158 abrogated C₁₆ -BODIPY but not DAUDA binding. L69 and T169 increased the fluorescence emission intensity of C₁₆ -BODIPY but not of DAUDA compared to wild-type ZAG and showed that C₁₆ -BODIPY binds close to T169 and L69. Distance measurements of the crystal structure revealed K147 forms a salt bridge with D83. A range of bioactive bulky lipids including phospholipids and sphingolipids displaced DAUDA from the ZAG binding site but unexpectedly did not displace C₁₆ -BODIPY. We conclude that the ZAG α1-α2 groove contains separate but overlapping sites for DAUDA and C₁₆ -BODIPY and is involved in binding to a bulkier and wider repertoire of lipids than previously reported. This work suggested that the in vivo activity of ZAG may be dictated by its lipid ligand.

Role of Zinc (Zn) in Human Reproduction: A Journey from Initial Spermatogenesis to Childbirth

Zinc (Zn), the second-most necessary trace element, is abundant in the human body. The human body lacks the capacity to store Zn; hence, the dietary intake of Zn is essential for various functions and metabolism. The uptake of Zn during its transport through the body is important for proper development of the three major accessory sex glands: the testis, epididymis, and prostate. It plays key roles in the initial stages of germ cell development and spermatogenesis, sperm cell development and maturation, ejaculation, liquefaction, the binding of spermatozoa and prostasomes, capacitation, and fertilization. The prostate releases more Zn into the seminal plasma during ejaculation, and it plays a significant role in sperm release and motility. During the maternal, labor, perinatal, and neonatal periods, the part of Zn is vital. The average dietary intake of Zn is in the range of 8-12 mg/day in developing countries during the maternal period. Globally, the dietary intake of Zn varies for pregnant and lactating mothers, but the average Zn intake is in the range of 9.6-11.2 mg/day. The absence of Zn and the consequences of this have been discussed using critical evidence. The events and functions of Zn related to successful fertilization have been summarized in detail. Briefly, our current review emphasizes the role of Zn at each stage of human reproduction, from the spermatogenesis process to childbirth. The role of Zn and its supplementation in in vitro fertilization (IVF) opens opportunities for future studies on reproductive biology.

Seminal Plasma Proteome as an Indicator of Sperm Dysfunction and Low Sperm Motility in Chickens

Molecular mechanisms underlying sperm motility have not been fully explained, particularly in chickens. The objective was to identify seminal plasma proteins associated with chicken sperm motility by comparing the seminal plasma proteomic profile of roosters with low sperm motility (LSM, n = 4) and high sperm motility (HSM, n = 4). Using a label-free MS-based method, a total of 522 seminal plasma proteins were identified, including 386 (∼74%) previously reported and 136 novel ones. A total of 70 differentially abundant proteins were defined, including 48 more-abundant, 15 less-abundant, and seven proteins unique to the LSM group (specific proteins). Key secretory proteins like less-abundant adhesion G-protein coupled receptor G2 (ADGRG2) and more-abundant serine peptidase inhibitor Kazal-type 2 (SPINK2) in the LSM suggested that the corresponding secretory tissues played a crucial role in maintaining sperm motility. Majority (80%) of the more-abundant and five specific proteins were annotated to the cytoplasmic domain which might be a result of higher plasma membrane damage and acrosome dysfunction in LSM. Additionally, more-abundant mitochondrial proteins were detected in LSM seminal plasma associated with lower spermatozoa mitochondrial membrane potential (ΔΨm) and ATP concentrations. Further studies showed that the spermatozoa might be suffering from oxidative stress, as the amount of spermatozoa reactive oxygen species (ROS) were largely enhanced, seminal malondialdehyde (MDA) concentrations were increased, and the seminal plasma total antioxidant capacity (T-AOC) were decreased. Our study provides an additional catalogue of chicken seminal plasma proteome and supports the idea that seminal plasma could be as an indicator of spermatozoa physiology. More-abundant of acrosome, mitochondria and sperm cytoskeleton proteins in the seminal plasma could be a marker of sperm dysfunction and loss of motility. The degeneration of spermatozoa caused by the reduced seminal T-AOC and enhanced oxidative stress might be potential determinants of low sperm motility. These results could extend our understanding of sperm motility and sperm physiology regulation.

New insights into the zinc-α2-glycoprotein (ZAG) scaffold and its metal ions binding abilities using spectroscopic techniques

AIMS

Zinc-α2-glycoprotein (ZAG) is soluble lipid mobilizing protein and a noval adipokine associated with cancer cachexia. ZAG is an omnipresent protein and represent a fold of MHC class I proteins. Although ZAG's metal binding capacity has already been reported, no other metal has been mapped to date besides the complex formation with zinc.

MAIN METHODOLOGY

In this study, fluorescence emission spectroscopy and mass spectrometry (MALDI-TOF) were employed to define the putative interaction sites and their accessibility for the biologically important metals of Irving William Series.

KEY FINDINGS

Several hotspot residues in the ZAG scaffold involved in these interactions were mapped and their binding affinity score for each metal has been determined. Thebinding abilities of these sites and aggregation propensities of ZAG were monitored by fluorescence emission spectroscopy.

SIGNIFICANCE

The prediction of such binding affinity with metals on the active sites and its impact on the conformational states to accelerate aggregation was discussed as an important finding that may be involved in several other biochemical processes such as lipid binding, β-adrenergic receptors, cancer cachexia and association with plasma cholesterol and obesity.

Ram seminal plasma and its functional proteomic assessment

Ejaculation results in the confluence of epididymal spermatozoa with secretions of the accessory sex glands. This interaction is not a prerequisite for fertilisation success, but seminal factors do play a crucial role in prolonging the survival of spermatozoa both in vitro and in vivo by affording protection from handling induced stress and some selective mechanisms of the female reproductive tract. Reproductive biologists have long sought to identify specific factors in seminal plasma that influence sperm function and fertility in these contexts. Many seminal plasma proteins have been identified as diagnostic predictors of sperm function and have been isolated and applied in vitro to prevent sperm damage associated with the application of artificial reproductive technologies. Proteomic assessment of the spermatozoon, and its surroundings, has provided considerable advances towards these goals and allowed for greater understanding of their physiological function. In this review, the importance of seminal plasma will be examined through a proteomic lens to provide comprehensive analysis of the ram seminal proteome and detail the use of proteomic studies that correlate seminal plasma proteins with ram sperm function and preservation ability.

Zinc-α2-glycoprotein as an inhibitor of amine oxidase copper-containing 3

Zinc-α2-glycoprotein (ZAG) is a major plasma protein whose levels increase in chronic energy-demanding diseases and thus serves as an important clinical biomarker in the diagnosis and prognosis of the development of cachexia. Current knowledge suggests that ZAG mediates progressive weight loss through β-adrenergic signalling in adipocytes, resulting in the activation of lipolysis and fat mobilization. Here, through cross-linking experiments, amine oxidase copper-containing 3 (AOC3) is identified as a novel ZAG binding partner. AOC3-also known as vascular adhesion protein 1 (VAP-1) and semicarbazide sensitive amine oxidase (SSAO)-deaminates primary amines, thereby generating the corresponding aldehyde, H2O2 and NH3. It is an ectoenzyme largely expressed by adipocytes and induced in endothelial cells during inflammation. Extravasation of immune cells depends on amine oxidase activity and AOC3-derived H2O2 has an insulinogenic effect. The observations described here suggest that ZAG acts as an allosteric inhibitor of AOC3 and interferes with the associated pro-inflammatory and anti-lipolytic functions. Thus, inhibition of the deamination of lipolytic hormone octopamine by AOC3 represents a novel mechanism by which ZAG might stimulate lipolysis. Furthermore, experiments involving overexpression of recombinant ZAG reveal that its glycosylation is co-regulated by oxygen availability and that the pattern of glycosylation affects its inhibitory potential. The newly identified protein interaction between AOC3 and ZAG highlights a previously unknown functional relationship, which may be relevant to inflammation, energy metabolism and the development of cachexia.

From One Ejaculate to Another: Transference of Sperm Traits via Seminal Plasma Supplementation in the Ram

Males can adjust sperm motility instantaneously in response to the perceived risk of sperm competition. The speed of this response suggests that sperm motility is regulated by changes in seminal plasma rather than changes in the sperm cells themselves. Hence, here we test whether inter-ejaculate variation in seminal plasma can be used to alter sperm quality prior to use in assisted reproductive technologies. We supplemented fresh ejaculates of Merino rams with seminal plasma collected from previous 'donor' ejaculates to test whether changes in sperm kinetics were related to the relative quality of donor to focal ejaculates. We found a positive relationship between the change in sperm traits before and after supplementation, and the difference in sperm traits between the donor and focal ejaculate. Hence, sperm motility can be either increased or decreased through the addition of seminal plasma from a superior or inferior ejaculate, respectively. This positive relationship held true even when seminal plasma was added from a previous ejaculate of the same ram, although the slope of the relationship depended on the identity of both the donor and receiver ram. These findings indicate that seminal plasma plays a key role in the control and regulation of sperm kinetics, and that sperm kinetic traits can be transferred from one ejaculate to another through seminal plasma supplementation.

Relationship between concentrations of macro and trace elements in serum and follicular, oviductal, and uterine fluids of the dromedary camel (Camelus dromedarius)

This study aimed at investigating the relationship between concentrations of macro and trace elements in blood serum, and fluids from small and large follicles (SFF and LFF, respectively), oviduct (OF), and uterus (UF) of female dromedary camels. Fluids from small (2-6 mm) and large follicles (7-20 mm), oviduct and uterus, and blood samples were collected from 19 camels. The results indicated that the concentrations of serum Mg, Fe, and Mn were significantly higher than their follicular fluid, OF, and UF concentrations. Levels of Zn, Fe, Cu, Cr, and Mn were significantly higher in SFF than in LFF. Se and Mo concentrations were higher in LFF. Co concentration was lower in serum than in reproductive tract fluids. Cr concentration was higher in UF and OF than in the serum, SFF, and LFF. High Ca concentration was observed for serum and SFF, followed by LFF. The concentration of Na was about 1.18-fold higher in SFF than in serum, OF, and LFF, and approximately 4.1-fold higher in serum than in UF. K was present in higher concentration in SFF than in serum and LFF; however, its concentration was low in UF and OF. In conclusion, this study shows the concentrations of certain elements in small and large follicular, uterine, and oviductal fluids, which may be low or high depending on their function in the development and growth of follicles. This information can support the development of new media for in vitro oocyte maturation and fertilization of female camels.

Seminal plasma proteins as markers of sperm fertility

During ejaculation and deposition in the female genital tract, spermatozoa are exposed to seminal plasma, a mix of secretions primarily from the accessory sex glands. Proteins, which make up the largest contribution to seminal plasma by weight, have been the focus of much interest, in particular the identification of specific proteins both in the plasma and/or found bound to the sperm surface post ejaculation. Global proteomic studies of seminal plasma originating from a range of species over the last 15 years have revealed their hitherto unknown diversity and complexity. Seminal plasma is generally known to aid sperm survival and fertility in a range of species and studies have begun to reveal its link with sperm function and identification, as markers of fertility. This review summarises recent data on proteins found on the sperm surface that originate from seminal plasma and have subsequently been shown to correlate with fertility, with a focus on the pig.

Addition of chlorogenic acid and caffeine during the processing of cooled boar semen

ABSTRACT A study was conducted to evaluate the effect of chlorogenic acid (ChA) added pre-cooling and its combination with caffeine added during warming on cooled-stored boar semen parameters. Ten ejaculates were diluted in commercial extender with or without 4.5mg/ml ChA and stored at 15°C. After 0, 24 and 72 hours of storage, aliquots of these doses were taken and incubated at 37°C in the presence or absence of 8.0mM caffeine. Semen quality was evaluated after 10 and 120 minutes of incubation. The ChA increased (P <0.01) the sperm motility, viability, acrosomal integrity and the percentage of spermatozoa with high mitochondrial activity (PMHA), however, decreased (P <0.01) the malondialdehyde (MDA) concentration. Caffeine increased (P<0.05) the sperm motility, viability, PMHA and the MDA concentration and reduced (P <0.05) the acrosome integrity. When associated (ChA+caffeine), there was an increase (P <0.05) in sperm motility and viability, PMHA and acrosome integrity. The addition of ChA to the dilution medium improves the quality of the swine inseminating doses. The addition of caffeine during re-warming is only recommended when the semen is stored for prolonged periods (72h), and the inseminating dose should be used immediately after its addition.

Seminal plasma proteomes and sperm fertility

During ejaculation, the spermatozoa are transported by the seminal plasma, a fluid resulting from secretions originating mainly from the prostate and the seminal vesicles in mammals. The interaction of the seminal plasma with spermatozoa induces binding of seminal proteins onto the sperm surface and membrane remodeling potentially impacting the sperm transport, survival and fertilizing ability in the female genital tract. The seminal plasma also contains peptides and proteins involved in the inflammatory and immune response of the female tract. Therefore the seminal plasma proteome has been investigated in a large range of taxa, including mammals, birds, fishes and insect species. The association of the seminal plasma with semen preservation or fertility identified proteic markers of seminal plasma function in domestic species. This review summarizes the current knowledge in seminal plasma proteomes and proteic markers of sperm preservation in animal species.

Profiling of proteins secreted in the bovine oviduct reveals diverse functions of this luminal microenvironment

The oviductal microenvironment is a site for key events that involve gamete maturation, fertilization and early embryo development. Secretions into the oviductal lumen by either the lining epithelium or by transudation of plasma constituents are known to contain elements conducive for reproductive success. Although previous studies have identified some of these factors involved in reproduction, knowledge of secreted proteins in the oviductal fluid remains rudimentary with limited definition of function even in extensively studied species like cattle. In this study, we used a shotgun proteomics approach followed by bioinformatics sequence prediction to identify secreted proteins present in the bovine oviductal fluid (ex vivo) and secretions from the bovine oviductal epithelial cells (in vitro). From a total of 2087 proteins identified, 266 proteins could be classified as secreted, 109 (41%) of which were common for both in vivo and in vitro conditions. Pathway analysis indicated different classes of proteins that included growth factors, metabolic regulators, immune modulators, enzymes, and extracellular matrix components. Functional analysis revealed mechanisms in the oviductal lumen linked to immune homeostasis, gamete maturation, fertilization and early embryo development. These results point to several novel components that work together with known elements mediating functional homeostasis, and highlight the diversity of machinery associated with oviductal physiology and early events in cattle fertility.

Variation in seminal plasma alters the ability of ram spermatozoa to survive cryopreservation

Variation in the effect of seminal plasma on sperm function and fertility has been hypothesised to be due to differences between males and their seminal plasma composition. The freezing resilience of individual rams (n=17) was investigated to characterise inter-male variation. This was determined by measuring the degree of change in motility induced by cryopreservation (Experiment 1). Experiment 2 examined the effect of pooled seminal plasma from rams identified as having high or low resilience to freezing on the cryosurvival of washed spermatozoa from either high (n=3) or low (n=3) sperm freezing resilience rams. Immediately after thawing and throughout the incubation period (0-4h), spermatozoa from high-resilience rams frozen with high-resilience seminal plasma demonstrated superior motility to spermatozoa from high-resilience rams frozen with low-resilience seminal plasma (P<0.001). Similarly, spermatozoa from low-resilience rams frozen with high-resilience seminal plasma exhibited higher motility than spermatozoa from low-resilience rams frozen with low-resilience seminal plasma immediately after thawing (0h; P<0.001). The present study shows that variation in freezing resilience of ram spermatozoa is related to the source and composition of the seminal plasma.

Adipokine zinc-alpha-2-glycoprotein as a novel urinary biomarker presents earlier than microalbuminuria in diabetic nephropathy

OBJECTIVE

To investigate the role of zinc-alpha-2-glycoprotein (ZAG) in the early stage of diabetic nephropathy, in patients with type 2 diabetes mellitus (T2DM).

METHODS

This cross-sectional observational study recruited patients with longstanding T2DM and healthy control subjects. Patients with T2DM were further stratified based on their urine albumin-creatinine ratio (UACR) and estimated glomerular filtration rate (eGFR). Serum and urine concentrations of ZAG were determined using an enzyme-linked immunosorbent assay.

RESULTS

Eighty patients with T2DM and 20 healthy control subjects were enrolled in the study. Mean ± SD concentrations of ZAG in serum and urine were both significantly higher in patients with T2DM (serum: 38.29 ± 22.72 mg/l; urine: 53.64 ± 29.48 mg/g) compared with concentrations in healthy control subjects (serum: 21.61 ± 8.83 mg/l; urine: 28.17 ± 10.64 mg/g). Serum ZAG concentration was positively correlated with serum creatinine and eGFR. Urine ZAG concentration was positively correlated with UACR. Urine concentration of ZAG in the higher eGFR group was higher than that in the normal eGFR group (41.26 ± 13.67 versus 32.05 ± 8.55 mg/g, respectively).

CONCLUSION

These preliminary findings suggest that ZAG might be a potentially useful biomarker for early diagnosis of diabetic nephropathy in patients with T2DM.

High levels of Zinc-α-2-Glycoprotein among Omani AIDS patients on combined antiretroviral therapy

OBJECTIVE

To investigate the levels of zinc-α-2-glycoprotein (ZAG) among Omani AIDS patients receiving combined antiretroviral therapy (cART).

METHODS

A total of 80 Omani AIDS patients (45 males and 35 females), average age of 36 years, who were receiving cART at the Sultan Qaboos University Hospital (SQUH), Muscat, Oman, were tested for the levels of ZAG. In addition, 80 healthy blood donors (46 males and 34 females), average age of 26 years, attending the SQUH Blood Bank, were tested in parallel as a control group. Measurement of the ZAG levels was performed using a competitive enzyme-linked immunosorbent assay and in accordance with the manufacturer's instructions.

RESULTS

The ZAG levels were found to be significantly higher among AIDS patients compared to the healthy individuals (P=0.033). A total of 56 (70%) of the AIDS patients were found to have higher levels of ZAG and 16 (20%) AIDS patients were found to have high ZAG levels, which are significantly (P>0.031) associated with weight loss.

CONCLUSIONS

ZAG levels are high among Omani AIDS patients on cART and this necessitates the measurement of ZAG on routine basis, as it is associated with weight loss.

Investigation of galectin-3 function in the reproductive tract by identification of binding ligands in human seminal plasma

PROBLEM

Galectin-3 is a β-galactoside binding protein with immunomodulatory properties and exerts its extracellular functions via interactions with glycoconjugate ligands. Therefore, to elucidate the function of galectin-3, binding ligands in human seminal plasma were investigated.

METHOD OF STUDY

Galectin-3 binding proteins were isolated from seminal plasma by affinity chromatography, and candidate ligands were identified by MS/MS. Biochemical methods were used to characterize the ability of galectin-3 to bind its ligands.

RESULTS

Identified galectin-3 ligands included CD13, MUC6, PAP, PSA, and ZAG. 1D and 2D electrophoretic analysis of seminal plasma demonstrated that CD13, PAP, PSA, and ZAG immunoreactivity co-migrated with galectin-3-reactive protein bands and spots at expected molecular weights and pIs. Inhibition assays indicated that CD13, PSA, PAP, and ZAG interact with galectin-3 in a protein-carbohydrate manner.

CONCLUSION

The galectin-3 binding ligands identified in this study indicate multiple roles for galectin-3 in the reproductive and immunological functions of seminal plasma.

Palmitoyl-protein thioesterase 1 (PPT1): an obesity-induced rat testicular marker of reduced fertility

Male obesity may lead to declines in testosterone levels, reproductive hormonal profile, and semen quantity. To assess the effects of obesity on spermatogenesis, Sprague-Dawley rats fed a high-fat diet served as a model of induced obesity. The litter sizes for females mated to obese males were significantly lower as compared to females mated with normal-diet-fed controls. Their serum high-density lipoprotein, low-density lipoprotein, cholesterol, and estradiol levels increased in obese males, but testosterone and follicle-stimulating hormone levels decreased. Testicular morphology disruptions included Sertoli-cell atrophy, disrupted tight junctions, and mitochondrial degeneration in spermatogenic cells. To further investigate the molecular mechanisms leading to high-fat-diet-induced changes, we employed testicular proteomic analysis on rats fed both types of diet. Three spots were up-regulated in rats fed a high-fat diet whereas two others were downregulated. One of the upregulated spots was palmitoyl-protein thioesterase 1 (PPT1), a lipoprotein metabolizing related enzyme localized to Sertoli cells. In a Sertoli-cell line cultured in a high-fat supplemented medium, PPT1 abundance was accompanied by increases in the endocytic vesicle-associated protein, clathrin, and decreases in the tight junctional proteins, ZO-1 and occludin. In conclusion, declines in rat male fertility induced by a high-fat diet are associated with an altered testicular protein expression pattern as well as disruption of testicular Sertoli-cell and spermatogenic-cell morphology. PPT1 expression may provide a testicular marker of reduced fertility in obese males, as increases in its expression may be detrimental to Sertoli-cell function during spermatogenesis.

Proteomic identification of galectin-3 binding ligands and characterization of galectin-3 proteolytic cleavage in human prostasomes

Galectin-3 is a multifunctional carbohydrate-binding protein that was previously characterized as a proteolytic substrate for prostate-specific antigen (PSA) and was shown to be associated with prostasomes in human semen. Prostasomes are exosome-like vesicles that are secreted by the prostatic epithelium and have multiple proposed functions in normal reproduction and prostate cancer. In the current study, galectin-3 binding ligands in human prostasomes were identified and characterized with the goal to investigate galectin-3 function in prostasomes. Galectin-3 binding proteins were isolated by affinity column chromatography. Candidate ligands identified by MS/MS were PSA, prostatic acid phosphatase (PAP), zinc alpha-2-glycoprotein (ZAG), dipeptidyl peptidase-4 (CD26), aminopeptidase N (CD13), neprilysin, clusterin, antibacterial protein (FALL-39) and alpha-1-acid glycoprotein (ORM1). Biochemical methods were used to characterize the ability of galectin-3 to bind to selected ligands, and galectin-3 cleavage assays were utilized to investigate the protease(s) in prostasomes that cleaves galectin-3. CD26, CD13, PSA, PAP and ZAG immunoreactivity were detected in extracts of purified prostasomes. One-dimensional electroblot analysis of prostasomes demonstrated that CD26, PAP and CD13 immunoreactivity co-migrated with galectin-3-reactive protein bands. PSA and ZAG were found to be associated with the surface of prostasomes. Both intact and cleaved galectin-3 were detected in prostate and prostasome extracts. Cleavage and inhibition assays indicated that PSA in prostasomes proteolytically cleaves galectin-3. The identification of these glycoproteins as galectin-3 ligands lays the groundwork for future studies of galectin-3 and prostasome function in reproduction and prostate cancer.

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.

Interaction analysis identifies semenogelin I fragments as new binding partners of PIP in human seminal plasma

Identification of protein-protein interactions is vital for complete understanding of a biological process and for functional characterization of a protein in related biochemical pathways. In this study, we performed analysis of prolactin inducible protein (PIP) interactions in human seminal plasma. PIP and its interacting partners were co-immunoprecipitated, analyzed by SDS-PAGE and identified by MALDI-TOF mass spectrometry. Three major interacting partners were identified, viz. human serum albumin, zinc-α-2 glycoprotein and semenogelin I fragments. This is the first report of interaction between PIP and semenogelin I fragments in human seminal plasma or elsewhere with a suggestive role in reproductive physiology which might be helpful for spermatozoa to acquire their motility.

Human serum albumin as a new interacting partner of prolactin inducible protein in human seminal plasma

Prolactin inducible protein (PIP) is a 17 kDa glycoprotein. It binds to many proteins including fibrinogen, actin, keratin, myosin, immunoglobulin G, CD4, and human zinc-alpha-2 glycoprotein. Its ability to bind a large array of proteins indicates its multifaceted role in various biological processes, such as fertility, immunoregulation, antimicrobial activity, apoptosis, and tumor progression. Here, we present the first report of native human serum albumin (HSA)-PIP complex formation in seminal plasma. The complex was purified by chromatographic separation techniques, analyzed by gel electrophoresis, identified by MALDI-TOF mass spectrometry and validated by co-immunoprecipitation coupled with western blotting experiments. Moreover, the behavior of complex in solution was analyzed by dynamic light scattering and interacting residues were identified by in silico protein-protein docking. The purified protein complex shows two bands (67 kDa and 17 kDa) on SDS-PAGE gel and a single band (~85 kDa) on native PAGE gel. The predicted complex structure has 13 intermolecular hydrogen bonds, which may contribute to the overall stability of the complex. As HSA has been known to preserve the motility of sperm, native HSA-PIP complex formation may point towards an important role of PIP, which can directly be correlated with male fertility/infertility.

Con A-binding protein Zn-α2-glycoprotein on human sperm membrane is related to acrosome reaction and sperm fertility

Fertilization, the recognition and fusion between spermatozoa and oocyte, involves various molecules on the spermatozoa and oocyte membranes. Concanavalin A (ConA)-binding proteins may be one of the molecules involved in mammal spermatozoa fertilization; however, their structure and function remain largely unknown. Here, we initially identified a ConA-binding protein, Zn-α2-glycoprotein (ZAG), involved in regulating the acrosome reaction (AR) of human spermatozoa. ZAG is localized on the pre-equatorial region covering the acrosome, neck and tail (some parts of middle piece and principal piece respectively) regions of the acrosome intact human spermatozoa, and disappears in the acrosomal region of the acrosome-reacted spermatozoa. Polyclonal antibodies against human recombinant ZAG significantly reduced the AR and sperm capability binding to human zona pellucida or penetration into zona-free hamster oocytes. Furthermore, assessment of the signaling pathways regulated by ZAG revealed that ZAG affects sperm AR through both the cAMP/PKA and PKC pathways. These results indicate that ZAG, which is present on the human sperm membrane, plays a critical role in the AR and subsequently, may be involved in sperm fertility.

Purification and characterization of a native zinc-binding high molecular weight multiprotein complex from human seminal plasma

The seminal plasma comprises secretions from various accessory sex glands. During fertilization spermatozoa undergo complex sequences of precisely timed events that are regulated by the activation of different intracellular signaling pathways. The precision and efficacy of these pathways are often influenced by the assembly and interactions of multiprotein complexes, thereby directing the flow of regulatory information. Our knowledge about these protein complexes present in human seminal plasma (HuSP) is limited. Here we report the identification and characterization of a native high molecular weight zinc-binding multiprotein complex from HuSP by utilizing 2-DE followed by MS. Twenty-six proteins representing isoforms and/or fragments of 11 different proteins were found to be assembled in this complex. Prostate-specific antigen, zinc α2-glycoprotein, prostatic acid phosphatase, and prolactin inducible protein were the major proteins of this complex. Dynamic light scattering experiments revealed changes in aggregation pattern accompanied with deviation from physiological pH and in presence of SDS. However, no significant changes were observed in the presence of physiological ligands such as zinc and fructose. The present study will be useful and contribute to guide the future studies performed for elucidation of biological significance of this native complex in HuSP.

Endoplasmic reticulum protein 29 (ERp29), a protein related to sperm maturation is involved in sperm-oocyte fusion in mouse

BACKGROUND

Sperm-oocyte fusion is a critical step in fertilization, which requires a series of proteins from both spermatozoa and oocyte to mediate membrane adhesion and subsequent fusion. A rat spermatozoa membrane protein is endoplasmic reticulum protein 29 (ERp29), which significantly increases on the sperm surface as well as in the cytoplasm of epididymal epithelia from caput to cauda as the sperm undergo epididymal maturation. Moreover, ERp29 facilitates viral infection via mediating membrane penetration. We determined if in addition to promoting sperm maturation ERp29 may also play a role in facilitating gamete fusion during the fertilization process.

METHODS

Laser scanning confocal microscopy (LSCM) and Western blot analysis were employed to probe for ERp29 protein in BALB/c mouse epididymal and acrosome-reacted spermatozoa. We prepared rabbit polyclonal antibodies against mouse recombinant ERp29 (rERp29) to characterize: 1) fertilization rate (FR); 2) fertilization index (FI); 3) sperm motility and 4) acrosome reaction (AR).

RESULTS

Confocal microscopy indicated that ERp29 was partially localized at the sperm head of the epididymal caput as well as over the whole head and part of the principal piece of the tail region from the epididymal cauda. However, when the acrosome reacted, ERp29 remained in the equatorial and post-acrosomal regions of the sperm head, which is the initial site of sperm-oocyte membrane fusion. Such localization changes were confirmed based on the results of Western blot analysis. Furthermore, the antibodies against mouse rERp29 inhibited the spermatozoa from penetrating into the zona pellucida (ZP)-free oocytes. The functional blocking antibodies reduced both mouse sperm-oocyte FR and FI at concentrations of 100 and 200 micro g/ml compared with pre-immunized rabbit IgG or with anti-mouse recombinant bactericidal/permeability-increasing protein (BPI, a sperm surface protein unrelated to sperm-oocyte fusion) antibodies (100 micro g/ml), but they had no effect on sperm motility and AR.

CONCLUSION

This study demonstrates that ERp29 on mouse spermatozoa membrane changes during epididymal transit and AR. Accordingly, in mice this protein may be one of the important factors involved in sperm fertilization by facilitating sperm-oocyte membrane fusion.

The antibody against a nuclear autoantigenic sperm protein can result in reproductive failure

To study whether the antibody against the testis form of the nuclear autoantigenic sperm protein (tNASP) could result in reproductive failure, we successfully cloned and expressed a 339-bp cDNA fragment of mouse tNASP (mtNASP). Using mouse as a model, recombinant mtNASP (rmtNASP) and a synthetic peptide, human tNASP(393-408) (htNASP(393-408)), were investigated for their antifertility effect. Active immunization with rmtNASP or the synthesized peptide raised high antibody titers in the immunized mice. Sperm-egg binding and fusion assay were carried out in 8-10-week-old BALB/c mice. Sperm-egg binding and in vitro fertilization of mouse oocytes were inhibited by co-incubation of zona-free mouse oocytes with capacitated mouse spermatozoa in the presence of varying concentrations of the antisera against rmtNASP. There was a significant antifertility effect in animals immunized with rmtNASP or the synthesized peptide. The effect on fertility in the mice immunized with the synthesized peptide was reversible. Our data indicate that active immunization with rmtNASP antigen may induce a strong antibody response that causes an inhibition of fertility.

Crystal structure of the novel complex formed between zinc alpha2-glycoprotein (ZAG) and prolactin-inducible protein (PIP) from human seminal plasma

This is the first report on the formation of a complex between zinc alpha2-glycoprotein (ZAG) and prolactin-inducible protein (PIP). The complex was purified from human seminal plasma and crystallized using 20% polyethylene glycol 9000 and 5% hexaethylene glycol. The structure of the complex has been determined using X-ray crystallographic method and refined to an R(cryst) of 0.199 (R(free)=0.239). The structure of ZAG is broadly similar to the structure of serum ZAG. The scaffolding of PIP consists of seven beta-strands that are organized in the form of two antiparallel beta-pleated sheets, resulting in the formation of a sandwiched beta-sheet. The amino acid sequence of PIP contains one potential N-glycosylation site at Asn77, and the same is found glycosylated with four sugar residues. The structure of the complex shows that the beta-structure of PIP is ideally aligned with the beta-structure of domain alpha3 of ZAG to form a long interface between two proteins. The proximal beta-strands at the long interface are arranged in an antiparallel manner. There are 12 hydrogen bonds and three salt bridges between ZAG and PIP. At the two ends of vertical interface, two salt bridges are formed between pairs of Lys41-Asp233 and Lys68-Glu229. On the perpendicular interface involving alpha1-alpha2 domains of ZAG and a loop of PIP, another salt bridge is formed. The internal space at the corner of the L-shaped structure is filled with solvent molecules including a carbonate ion. The overall buried area in the complex is approximately 914 A(2), which is considerably higher than the 660 A(2) reported for the class I major histocompatibility complex structures.