Identification of the inorganic pyrophosphate metabolizing, ATP substituting pathway in mammalian spermatozoa

Synergistic effect of extracellular adenosine triphosphate and quercetin on post-thaw quality and fertilization potential of Lohi ram sperm

This study determined the individual and combined effects of extracellular adenosine triphosphate (ATP) and quercetin (QUE) on the quality of post-thawed sperm and the fertilization potential of Lohi rams. In experiment 1, semen samples from four Lohi rams were pooled and extended with different concentrations of ATP or QUE (control; no ATP or QUE, 1 or 2 mM ATP and 10 or 20 μM QUE). In experiment 2, pooled semen samples were extended with various combinations of ATP and QUE (control; no ATP and QUE, 1 mM ATP + 10 μM QUE, 1 mM ATP + 20 μM QUE, 2 mM ATP + 10 μM QUE and 2 mM ATP + 20 μM QUE). All samples in both experiments were cryopreserved and analyzed for post-thawed sperm quality. In experiment 3, the best combination of ATP and QUE from experiment 2 was to extend semen, which was then used for laparoscopic insemination in estrus-synchronized ewes (n = 83). The results of experiment 1 showed that 1 mM ATP and 20 μM QUE treatments resulted in higher total motility, progressive motility, viability, plasma membrane intactness (PMI), and motion kinetics (VCL, VSL, VAP, LIN, and STR) compared to other treatments (p < 0.05). In experiment 2, the 1 mM ATP +10 μM QUE-treated group exhibited significantly higher total and progressive motility, PMI, and motion kinetics (VSL, VCL, VAP, STR, and BCF) compared to the control group (p < 0.05). In experiment 3, the fertilizing potential of sperms treated with 1 mM ATP +10 μM QUE was greater than that of untreated controls (58.1% vs. 27.5%, respectively, p-value = 0.012). In conclusion, the quality of post-thawed ram semen is enhanced when the extender is supplemented with extracellular 1 mM ATP and 20 μM QUE, whether used separately or in combination with 1 mM ATP and 10 μM QUE. Furthermore, the inclusion of 1 mM ATP and 10 μM QUE together in the extender significantly improves in vivo fertility in Lohi ram.

The Ubiquitin-Proteasome System Participates in Sperm Surface Subproteome Remodeling during Boar Sperm Capacitation

Sperm capacitation is a complex process endowing biological and biochemical changes to a spermatozoon for a successful encounter with an oocyte. The present study focused on the role of the ubiquitin-proteasome system (UPS) in the remodeling of the sperm surface subproteome. The sperm surface subproteome from non-capacitated and in vitro capacitated (IVC) porcine spermatozoa, with and without proteasomal inhibition, was selectively isolated. The purified sperm surface subproteome was analyzed using high-resolution, quantitative liquid chromatography-mass spectrometry (LC-MS) in four replicates. We identified 1680 HUGO annotated proteins, out of which we found 91 to be at least 1.5× less abundant (p < 0.05) and 141 to be at least 1.5× more abundant (p < 0.05) on the surface of IVC spermatozoa. These proteins were associated with sperm capacitation, hyperactivation, metabolism, acrosomal exocytosis, and fertilization. Abundances of 14 proteins were found to be significantly different (p < 0.05), exceeding a 1.5-fold abundance between the proteasomally inhibited (100 µM MG132) and vehicle control (0.2% ethanol) groups. The proteins NIF3L1, CSE1L, NDUFB7, PGLS, PPP4C, STK39, and TPRG1L were found to be more abundant; while BPHL, GSN, GSPT1, PFDN4, STYXL1, TIMM10, and UBXN4 were found to be less abundant in proteasomally inhibited IVC spermatozoa. Despite the UPS having a narrow range of targets, it modulated sperm metabolism and binding by regulating susceptible surface proteins. Changes in CSE1L, PFDN4, and STK39 during in vitro capacitation were confirmed using immunocytochemistry, image-based flow cytometry, and Western blotting. The results confirmed the active participation of the UPS in the extensive sperm surface proteome remodeling that occurs during boar sperm capacitation. This work will help us to identify new pharmacological mechanisms to positively or negatively modulate sperm fertilizing ability in food animals and humans.

Quantitative proteomic analysis uncovers protein-expression profiles during gonadotropin-dependent folliculogenesis in mice†

Ovarian follicle is the basic functional unit of female reproduction, and is composed of oocyte and surrounding granulosa cells. In mammals, folliculogenesis strictly rely on gonadotropin regulations to determine the ovulation and the quality of eggs. However, the dynamic changes of protein-expressing profiles in follicles at different developmental stages remain largely unknown. By performing mass-spectrometry-based quantitative proteomic analysis of mouse follicles, we provide a proteomic database (~3000 proteins) that covers three key stages of gonadotropin-dependent folliculogenesis. By combining bioinformatics analysis with in situ expression validation, we showed that our proteomic data well reflected physiological changes during folliculogenesis, which provided potential to predict unknown regulators of folliculogenesis. Additionally, by using the oocyte structural protein zona pellucida protein 2 as the internal control, we showed the possibility of our database to predict the expression dynamics of oocyte-expressing proteins during folliculogenesis. Taken together, we provide a high-coverage proteomic database to study protein-expression dynamics during gonadotropin-dependent folliculogenesis in mammals.

Mammalian Cell-Free System Recapitulates the Early Events of Post-Fertilization Sperm Mitophagy

Propagation of paternal sperm-contributed mitochondrial genes, resulting in heteroplasmy, is seldom observed in mammals due to post-fertilization degradation of sperm mitochondria, referred to as sperm mitophagy. Whole organelle sperm mitochondrion degradation is thought to be mediated by the interplay between the ubiquitin-proteasome system (UPS) and the autophagic pathway (Song et al., Proc. Natl. Acad. Sci. USA, 2016). Both porcine and primate post-fertilization sperm mitophagy rely on the ubiquitin-binding autophagy receptor, sequestosome 1 (SQSTM1), and the proteasome-interacting ubiquitinated protein dislocase, valosin-containing protein (VCP). Consequently, we anticipated that sperm mitophagy could be reconstituted in a cell-free system consisting of permeabilized mammalian spermatozoa co-incubated with porcine oocyte extracts. We found that SQSTM1 was detected in the midpiece/mitochondrial sheath of the sperm tail after, but not before, co-incubation with oocyte extracts. VCP was prominent in the sperm mitochondrial sheath both before and after the extract co-incubation and was also detected in the acrosome and postacrosomal sheath and the subacrosomal layer of the spermatozoa co-incubated with extraction buffer as control. Such patterns are consistent with our previous observation of SQSTM1 and VCP associating with sperm mitochondria inside the porcine zygote. In addition, it was observed that sperm head expansion mimicked the early stages of paternal pronucleus development in a zygote during prolonged sperm-oocyte extract co-incubation. Treatment with anti-SQSTM1 antibody during extract co-incubation prevented ooplasmic SQSTM1 binding to sperm mitochondria. Even in an interspecific cellular environment encompassing bull spermatozoa and porcine oocyte extract, ooplasmic SQSTM1 was recruited to heterospecific sperm mitochondria. Complementary with the binding of SQSTM1 and VCP to sperm mitochondria, two sperm-borne pro-mitophagy proteins, parkin co-regulated gene product (PACRG) and spermatogenesis associated 18 (SPATA18), underwent localization changes after extract coincubation, which were consistent with their degradation observed inside fertilized porcine oocytes. These results demonstrate that the early developmental events of post-fertilization sperm mitophagy observed in porcine zygote can be reconstituted in a cell-free system, which could become a useful tool for identifying additional molecules that regulate mitochondrial inheritance in mammals.

Crystal Structure of Inorganic Pyrophosphatase From Schistosoma japonicum Reveals the Mechanism of Chemicals and Substrate Inhibition

Soluble inorganic pyrophosphatases (PPases) are essential for facilitating the growth and development of organisms, making them attractive functional proteins. To provide insight into the molecular basis of PPases in Schistosoma japonicum (SjPPase), we expressed the recombinant SjPPase, analyzed the hydrolysis mechanism of inorganic pyrophosphate (PPi), and measured its activity. Moreover, we solved the crystal structure of SjPPase in complex with orthophosphate (Pi) and performed PPi and methylene diphosphonic acid (MDP) docking into the active site. Our results suggest that the SjPPase possesses PPi hydrolysis activity, and the activity declines with increased MDP or NaF concentration. However, the enzyme shows unexpected substrate inhibition properties. Through PPi metabolic pathway analysis, the physiological action of substrate inhibition might be energy saving, adaptably cytoprotective, and biosynthetic rate regulating. Furthermore, the structure of apo-SjPPase and SjPPase with Pi has been solved at 2.6 and 2.3 Å, respectively. The docking of PPi into the active site of the SjPPase-Pi complex revealed that substrate inhibition might result from blocking Pi exit due to excess PPi in the SjPPase-Pi complex of the catalytic cycle. Our results revealed the structural features of apo-SjPPase and the SjPPase-Pi complex by X-ray crystallography, providing novel insights into the physiological functions of PPase in S. japonicum without the PPi transporter and the mechanism of its substrate inhibition.

Sperm Functional Genome Associated With Bull Fertility

Bull fertility is an important economic trait in sustainable cattle production, as infertile or subfertile bulls give rise to large economic losses. Current methods to assess bull fertility are tedious and not totally accurate. The massive collection of functional data analyses, including genomics, proteomics, metabolomics, transcriptomics, and epigenomics, helps researchers generate extensive knowledge to better understand the unraveling physiological mechanisms underlying subpar male fertility. This review focuses on the sperm phenomes of the functional genome and epigenome that are associated with bull fertility. Findings from multiple sources were integrated to generate new knowledge that is transferable to applied andrology. Diverse methods encompassing analyses of molecular and cellular dynamics in the fertility-associated molecules and conventional sperm parameters can be considered an effective approach to determine bull fertility for efficient and sustainable cattle production. In addition to gene expression information, we also provide methodological information, which is important for the rigor and reliability of the studies. Fertility is a complex trait influenced by several factors and has low heritability, although heritability of scrotal circumference is high and that it is a known fertility maker. There is a need for new knowledge on the expression levels and functions of sperm RNA, proteins, and metabolites. The new knowledge can shed light on additional fertility markers that can be used in combination with scrotal circumference to predict the fertility of breeding bulls. This review provides a comprehensive review of sperm functional characteristics or phenotypes associated with bull fertility.

Beyond mitochondria: Alternative energy-producing pathways from all strata of life

It is well-established that mitochondria are the powerhouses of the cell, producing adenosine triphosphate (ATP), the universal energy currency. However, the most significant strengths of the electron transport chain (ETC), its intricacy and efficiency, are also its greatest downfalls. A reliance on metal complexes (FeS clusters, hemes), lipid moities such as cardiolipin, and cofactors including alpha-lipoic acid and quinones render oxidative phosphorylation vulnerable to environmental toxins, intracellular reactive oxygen species (ROS) and fluctuations in diet. To that effect, it is of interest to note that temporal disruptions in ETC activity in most organisms are rarely fatal, and often a redundant number of failsafes are in place to permit continued ATP production when needed. Here, we highlight the metabolic reconfigurations discovered in organisms ranging from parasitic Entamoeba to bacteria such as pseudomonads and then complex eukaryotic systems that allow these species to adapt to and occasionally thrive in harsh environments. The overarching aim of this review is to demonstrate the plasticity of metabolic networks and recognize that in times of duress, life finds a way.

A new 7-diethylamino-4-hydroxycoumarin based reversible colorimetric/fluorometric probe for sequential detection of Al3+/PPi and its potential use in biodetection and bioimaging applications

A new 7-diethylamino-4-hydroxycoumarin appended acylhydrazone probe was prepared and utilized for the sequential detection of Al³⁺/PPi in a reversible off–on–off emissive manner. The various practical applications of the probe were established.

Cryo-EM Structure of an Extended SARS-CoV-2 Replication and Transcription Complex Reveals an Intermediate State in Cap Synthesis

Transcription of SARS-CoV-2 mRNA requires sequential reactions facilitated by the replication and transcription complex (RTC). Here, we present a structural snapshot of SARS-CoV-2 RTC as it transitions toward cap structure synthesis. We determine the atomic cryo-EM structure of an extended RTC assembled by nsp7-nsp8₂-nsp12-nsp13₂-RNA and a single RNA-binding protein, nsp9. Nsp9 binds tightly to nsp12 (RdRp) NiRAN, allowing nsp9 N terminus inserting into the catalytic center of nsp12 NiRAN, which then inhibits activity. We also show that nsp12 NiRAN possesses guanylyltransferase activity, catalyzing the formation of cap core structure (GpppA). The orientation of nsp13 that anchors the 5′ extension of template RNA shows a remarkable conformational shift, resulting in zinc finger 3 of its ZBD inserting into a minor groove of paired template-primer RNA. These results reason an intermediate state of RTC toward mRNA synthesis, pave a way to understand the RTC architecture, and provide a target for antiviral development.

Phenological, morpho-physiological and proteomic responses of Triticum boeoticum to drought stress

Drought is the most important abiotic stress limiting wheat production worldwide. Triticum boeoticum, as wild wheat, is a rich gene pool for breeding for drought stress tolerance. In this study, to identify the most drought-tolerant and susceptible genotypes, ten T. boeoticum accessions were evaluated under non-stress and drought-stress conditions for two years. Among the studied traits, water-use efficiency (WUE) was suggested as the most important trait to identify drought-tolerant genotypes. According to the desirable and undesirable areas of the bi-plot, Tb5 and Tb6 genotypes were less and more affected by drought stress, respectively. Therefore, their flag-leaves proteins were used for two-dimensional gel electrophoresis. While, Tb5 contained a high amount of yield, yield components, and WUE, Tb6 had higher levels of water use, phenological related traits, and root related characters. Of the 235 spots found in the studied accessions, 14 spots (11 and 3 spots of Tb5 and Tb6, respectively) were selected for sequencing. Of these 14 spots, 9 and 5 spots were upregulated and downregulated, respectively. The identified proteins were grouped into six functional protein clusters, which were mainly involved in photosynthesis (36%), carbohydrate metabolism (29%), chaperone (7%), oxidation and reduction (7%), lipid metabolism and biological properties of the membrane (7%) and unknown function (14%). We report for the first time that MICP, in the group of lipid metabolism proteins, was significantly changed into wild wheat in response to drought stress. Maybe, the present-identified proteins could play an important role to understand the molecular pathways of wheat drought tolerance. We believe comparing and evaluating the similarity-identified proteins of T. boeoticum with the previously identified proteins of Aegilops tauschii, can provide a new direction to improve wheat tolerance to drought stress.

Uncovering sperm metabolome to discover biomarkers for bull fertility

Background

Subfertility decreases the efficiency of the cattle industry because artificial insemination employs spermatozoa from a single bull to inseminate thousands of cows. Variation in bull fertility has been demonstrated even among those animals exhibiting normal sperm numbers, motility, and morphology. Despite advances in research, molecular and cellular mechanisms underlying the causes of low fertility in some bulls have not been fully elucidated. In this study, we investigated the metabolic profile of bull spermatozoa using non-targeted metabolomics. Statistical analysis and bioinformatic tools were employed to evaluate the metabolic profiles high and low fertility groups. Metabolic pathways associated with the sperm metabolome were also reported.

Results

A total of 22 distinct metabolites were detected in spermatozoa from bulls with high fertility (HF) or low fertility (LF) phenotype. The major metabolite classes of bovine sperm were organic acids/derivatives and fatty acids/conjugates. We demonstrated that the abundance ratios of five sperm metabolites were statistically different between HF and LF groups including gamma-aminobutyric acid (GABA), carbamate, benzoic acid, lactic acid, and palmitic acid. Metabolites with different abundances in HF and LF bulls had also VIP scores of greater than 1.5 and AUC- ROC curves of more than 80%. In addition, four metabolic pathways associated with differential metabolites namely alanine, aspartate and glutamate metabolism, β-alanine metabolism, glycolysis or gluconeogenesis, and pyruvate metabolism were also explored.

Conclusions

This is the first study aimed at ascertaining the metabolome of spermatozoa from bulls with different fertility phenotype using gas chromatography-mass spectrometry. We identified five metabolites in the two groups of sires and such molecules can be used, in the future, as key indicators of bull fertility.

Boar semen improvement through sperm capacitation management, with emphasis on zinc ion homeostasis

Critical to fertilization success, sperm capacitation within the female oviductal sperm reservoir endows mammalian spermatozoa with hyperactivated motility and capacity to fertilize. An elaborate cascade of signaling events during capacitation guides the redistribution of sperm plasma membrane seminolipid and cholesterol, Ca-influx and increases tyrosine phosphorylation to promote hyperactivated motility. Such events result in the remodeling of the sperm acrosome, increased fluidity and fusability of the plasma membrane, shedding of surface-adsorbed seminal plasma proteins that glue sperm heads to the oviductal epithelium and ultimately the release of hyperactivated spermatozoa from the oviductal sperm reservoir. Discovered recently, the capacitation-induced sperm zinc ion efflux and resultant zinc signatures are reflective of sperm capacitation status and fertilizing ability, inspiring the retrospection of zinc ion functions in the physiology and fertility of boar sperm and that of other species. This review also highlights the merit of the domestic boar as a biomedical model for spermatology and fertilization research. Relevant to the quest for better fertility management in the livestock industries, the benefits of zinc ion supplementation through nutrition and direct addition to extended semen are discussed in the context of artificial insemination (AI). Ideas are shared on future technologies for zinc management in AI doses and research on the sperm zinc-interacting proteome.

RNA-seq coupled to proteomic analysis reveals high sperm proteome variation between two closely related marine mussel species

Speciation mechanisms in marine organisms have attracted great interest because of the apparent lack of substantial barriers to genetic exchange in marine ecosystems. Marine mussels of the Mytilus edulis species complex provide a good model to study mechanisms underlying species formation. They hybridise extensively at many localities and both pre- and postzygotic isolating mechanisms may be operating. Mussels have external fertilisation and sperm cells should show specific adaptations for survival and successful fertilisation. Sperm thus represent key targets in investigations of the molecular mechanisms underlying reproductive isolation. We undertook a deep transcriptome sequencing (RNA-seq) of mature male gonads and a 2DE/MS-based proteome analysis of sperm from Mytilus edulis and M. galloprovincialis raised in a common environment. We provide evidence of extensive expression differences between the two mussel species, and general agreement between the transcriptomic and proteomic results in the direction of expression differences between species. Differential expression is marked for mitochondrial genes and for those involved in spermatogenesis, sperm motility, sperm-egg interactions, the acrosome reaction, sperm capacitation, ATP reserves and ROS production. Proteins and their corresponding genes might thus be good targets in further genomic analysis of reproductive barriers between these closely related species. SIGNIFICANCE: Model systems for the study of fertilization include marine invertebrates with external fertilisation, such as abalones, sea urchins and mussels, because of the ease with which large quantities of gametes released into seawater can be collected after induced spawning. Unlike abalones and sea urchins, hybridisation has been reported between mussels of different Mytilus spp., which thus makes them very appealing for the study of reproductive isolation at both pre- and postzygotic levels. There is a lack of empirical proteomic studies on sperm samples comparing different Mytilus species, which could help to advance this study. A comparative analysis of sperm proteomes across different taxa may provide important insights into the fundamental molecular processes and mechanisms involved in reproductive isolation. It might also contribute to a better understanding of sperm function and of the adaptive evolution of sperm proteins in different taxa. There is now growing evidence from genomics studies that multiple protein complexes and many individual proteins might have important functions in sperm biology and the fertilisation process. From an applied perspective, the identification of sperm-specific proteins could also contribute to the improved understanding of fertility problems and as targets for fertility control.

Genetic dissection of bull fertility in US Jersey dairy cattle

The service sire has been recognized as an important factor affecting herd fertility in dairy cattle. Recent studies suggest that genetic factors explain part of the difference in fertility among Holstein sires. The main objective of this study was to dissect the genetic architecture of sire fertility in US Jersey cattle. The dataset included 1.5 K Jersey bulls with sire conception rate (SCR) records and 96 K single nucleotide polymorphism (SNP) markers spanning the whole genome. The analysis included whole‐genome scans for both additive and non‐additive effects and subsequent functional enrichment analyses using KEGG Pathway, Gene Ontology (GO) and Medical Subject Headings (MeSH) databases. Ten genomic regions located on eight different chromosomes explained more than 0.5% of the additive genetic variance for SCR. These regions harbor genes, such as PKDREJ,EPB41L2,PDGFD,STX2,SLC25A20 and IP6K1, that are directly implicated in testis development and spermatogenesis, sperm motility and the acrosome reaction. In addition, the genomic scan for non‐additive effects identified two regions on BTA11 and BTA25 with marked recessive effects. These regions harbor three genes—FER1L5,CNNM4 and DNAH3—with known roles in sperm biology. Moreover, the gene‐set analysis revealed terms associated with calcium regulation and signaling, membrane fusion, sperm cell energy metabolism, GTPase activity and MAPK signaling. These gene sets are directly implicated in sperm physiology and male fertility. Overall, this integrative genomic study unravels genetic variants and pathways affecting Jersey bull fertility. These findings may contribute to the development of novel genomic strategies for improving sire fertility in Jersey cattle.

Metabolomic markers of fertility in bull seminal plasma

Metabolites play essential roles in biological systems, but detailed identities and significance of the seminal plasma metabolome related to bull fertility are still unknown. The objectives of this study were to determine the comprehensive metabolome of seminal plasma from Holstein bulls and to ascertain the potential of metabolites as biomarkers of bull fertility. The seminal plasma metabolome from 16 Holstein bulls with two fertility rates were determined by gas chromatography-mass spectrometry (GC-MS). Multivariate and univariate analyses of the data were performed, and the pathways associated with the seminal plasma metabolome were identified using bioinformatics approaches. Sixty-three metabolites were identified in the seminal plasma of all bulls. Fructose was the most abundant metabolite in the seminal fluid, followed for citric acid, lactic acid, urea and phosphoric acid. Androstenedione, 4-ketoglucose, D-xylofuranose, 2-oxoglutaric acid and erythronic acid represented the least predominant metabolites. Partial-Least Squares Discriminant Analysis (PLSDA) revealed a distinct separation between high and low fertility bulls. The metabolites with the greatest Variable Importance in Projection score (VIP > 2) were 2-oxoglutaric acid and fructose. Heat-map analysis, based on VIP score, and univariate analysis indicated that 2-oxoglutaric acid was less (P = 0.02); whereas fructose was greater (P = 0.02) in high fertility than in low fertility bulls. The current study is the first to describe the metabolome of bull seminal plasma using GC-MS and presented metabolites such as 2-oxoglutaric acid and fructose as potential biomarkers of bull fertility.

ATP-degrading ENPP1 is required for survival (or persistence) of long-lived plasma cells

Survival of antibody-secreting plasma cells (PCs) is vital for sustained antibody production. However, it remains poorly understood how long-lived PCs (LLPCs) are generated and maintained. Here we report that ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) is preferentially upregulated in bone marrow LLPCs compared with their splenic short-lived counterparts (SLPCs). We studied ENPP1-deficient mice (Enpp1^−/−) to determine how the enzyme affects PC biology. Although Enpp1^−/− mice generated normal levels of germinal center B cells and plasmablasts in periphery, they produced significantly reduced numbers of LLPCs following immunization with T-dependent antigens or infection with plasmodium C. chabaudi. Bone marrow chimeric mice showed B cell intrinsic effect of ENPP1 selectively on generation of bone marrow as well as splenic LLPCs. Moreover, Enpp1^−/− PCs took up less glucose and had lower levels of glycolysis than those of wild-type controls. Thus, ENPP1 deficiency confers an energetic disadvantage to PCs for long-term survival and antibody production.

Clinical significance and functional validation of inorganic pyrophosphatase in diffuse large B cell lymphoma in humans

Diffuse large B-cell lymphoma (DLBCL), the most common type of non-Hodgkin's lymphoma, displays marked heterogeneity. Although it is usually curable, 30-40% of patients die within 1-2 years due to refractory treatment or cancer relapse. In different types of cancer in humans, inorganic pyrophosphatase (PPA1) is deregulated, thereby contributing to tumorigenesis by supplying the tumor with an enormous energy source. However, the role of PPA1 in DLBCL is still unclear. Here, we analized PPA1 in 65 patients with DLBCL and 20 patients with reactive hyperplasia of the lymph nodes (control). The PPA1 level was significantly higher in patients with DLBCL than in control subjects (p < 0.05), and it is closely associated with B symptoms (i.e., fever, night sweats, and weight loss) and the IPI score (p < 0.05). Furthermore, PPA1 mRNA and protein levels were higher in most DLBCL cell lines than in the control HMy2.CIR cell line. Lastly, we investigated the effects of PPA1 knockdown on the proliferation and survival of the DLBCL cell line. We found that p53 and p21 expression decreased in PPA1-silenced DLBCL cells. In addition, cell proliferation decreased and cell apoptosis increased. In conclusion, PPA1 is a novel molecule that may be useful in the development and prognosis of DLBCL in the future.

Expression of Inorganic Pyrophosphatase (PPA1) Correlates with Poor Prognosis of Epithelial Ovarian Cancer

Ovarian serous carcinoma (OSC) is the most common epithelial ovarian cancer. Inorganic pyrophosphatase (PPA1) catalyzes the hydrolysis of pyrophosphate to inorganic phosphate, thereby providing extra energy for metabolism. The significance of PPA1 in the prognosis of OSC has not been investigated. Our study aimed to explore the expression and predictive role of PPA1 in OSC progression. We screened the expression of PPA1 protein in OSC tissues from 139 patients by immunohistochemistry, and evaluated its correlation with clinicopathological characteristics. PPA1 was categorized as high expression in 58 OSC cases (41.7%), which was correlated with poor differentiation, positive lymph node (LN) metastasis and advanced FIGO (The International Federation of Gynecology and Obstetrics) stages. Univariate and multivariate analyses identified PPA1 as a novel independent prognostic biomarker in OSC patients; meanwhile, conventional factors such as LN status and FIGO stages also showed statistical significance. Moreover, the expression levels of PPA1 protein were higher in A2780 and OVCAR3 human ovarian cancer cell lines than those in normal ovarian surface epithelial cells. Using these ovarian cancer cell lines, we showed that PPA1 overexpression caused the decrease in the expression level of p53, the tumor suppressor, with the increase in β-catenin level, as determined by Western blot analysis. Conversely, knockdown of PPAI expression was associated with the increase of p53 level and the decreased of β-catenin level. Consistently, the proliferation and invasion capacities of ovarian cancer cells were enhanced upon PPA1 overexpression. In conclusion, PPA1 serves as a potential prognostic biomarker for patients with OSC.

A novel mechanism of functional cooperativity regulation by thiol redox status in a dimeric inorganic pyrophosphatase

BACKGROUND

Inorganic PPases are essential metal-dependent enzymes that convert pyrophosphate into orthophosphate. This reaction is quite exergonic and provides a thermodynamic advantage for many ATP-driven biosynthetic reactions. We have previously demonstrated that cytosolic PPase from R. microplus embryos is an atypical Family I PPase. Here, we explored the functional role of the cysteine residues located at the homodimer interface, its redox sensitivity, as well as structural and kinetic parameters related to thiol redox status.

METHODS

In this work, we used prokaryotic expression system for recombinant protein overexpression, biochemical approaches to assess kinetic parameters, ticks embryos and computational approaches to analyze and predict critical amino acids as well as physicochemical properties at the homodimer interface.

RESULTS

Cysteine 339, located at the homodimer interface, was found to play an important role in stabilizing a functional cooperativity between the two catalytic sites, as indicated by kinetics and Hill coefficient analyses of the WT-rBmPPase. WT-rBmPPase activity was up-regulated by physiological antioxidant molecules such as reduced glutathione and ascorbic acid. On the other hand, hydrogen peroxide at physiological concentrations decreased the affinity of WT-rBmPPase for its substrate (PP_i), probably by inducing disulfide bridge formation.

CONCLUSIONS

Our results provide a new angle in understanding redox control by disulfide bonds formation in enzymes from hematophagous arthropods. The reversibility of the down-regulation is dependent on hydrophobic interactions at the dimer interface.

GENERAL SIGNIFICANCE

This study is the first report on a soluble PPase where dimeric cooperativity is regulated by a redox mechanism, according to cysteine redox status.

New Approaches to Boar Semen Evaluation, Processing and Improvement

The improvement of boar reproductive performance may be the next frontier in reproductive management of swine herd in Unites States, facilitated by better understanding of boar sperm function and by the introduction of new advanced instrumentation in the andrology field. Objective single ejaculate evaluation and individual boar fertility prediction may be possible by introducing automated flow cytometric semen analysis with vital stains (e.g. acrosomal integrity and mito-potential), DNA fragmentation analysis and biomarkers (ubiquitin, PAWP, ALOX15, aggresome) associated with normal or defective sperm phenotypes. Measurement of sperm-produced reactive oxygen species (ROS) is a helpful indicator of normal semen sample. Semen ROS levels could be managed by the addition of ROS-scavenging antioxidants. Alternative energy regeneration substrates and sperm stimulants such as inorganic pyrophosphate and caffeine could increase sperm lifespan in extended semen and within the female reproductive system. Such technology could be combined with timed sperm release in the female reproductive system after artificial insemination. Sperm phenotype analysis by the image-based flow cytometry will go hand in hand with the advancement of swine genomics, linking aberrant sperm phenotype to the fertility influencing gene polymorphisms. Finally, poor-quality ejaculates could be rescued and acceptable ejaculates improved by semen purification methods such as the nanoparticle-based semen purification and magnetic-activated sperm sorting. Altogether, these scientific and technological advances could benefit swine industry, provided that the challenges of new technology adoption, dissemination and cost reduction are met.

Regulation of Sperm Capacitation by the 26S Proteasome: An Emerging New Paradigm in Spermatology

The ubiquitin proteasome system (UPS) participates in many biological processes ranging from cell cycle and antigen processing to cellular defense and signaling. Work of the last decade has made it evident that the UPS is involved in many sperm-related processes leading up to and as part of fertilization. The current knowledge of UPS involvement and changes during sperm capacitation are reviewed together with a list of known proteasome-associated sperm proteins and a discussion of the relationships between these proteins and the proteasome. Proteasomal inhibitors such as MG-132 and epoxomicin significantly alter capacitation and prevent acrosome reaction. The 26S proteasome degrades AKAP3, an A-kinase anchoring protein, partially regulating the release of protein-kinase A (PKA), a vital component necessary for the steps leading up to capacitation. Further, changes occur in 20S core subunit localization and abundance throughout capacitation. Proteasome-interacting valosine-containing protein (VCP) undergoes tyrosine phosphorylation; however, its physiological roles in capacitation and fertilization remain unknown. The E1-type ubiquitin-activating enzyme (UBA1) inhibitor PYR-41 also alters acrosomal membrane remodeling during capacitation. Furthermore, after capacitation, the acrosomal proteasomes facilitate the degradation of zona pellucida glycoproteins leading up to fertilization. Methods to modulate the sperm proteasome activity during sperm storage and capacitation may translate to increased reproductive efficiency in livestock animals. Human male infertility diagnostics may benefit from incorporation of research outcomes built upon relationships between UPS and capacitation. Altogether, the studies reviewed here support the involvement of UPS in sperm capacitation and present opportunities for new discoveries.

Effect of extracellular adenosine 5'-triphosphate on cryopreserved epididymal cat sperm intracellular ATP concentration, sperm quality, and in vitro fertilizing ability

Intracellular adenosine 5'-triphosphate (ATP) is essential for supporting sperm function in the fertilization process. During cryopreservation, damage of sperm mitochondrial membrane usually leads to compromised production of intracellular ATP. Recently, extracellular ATP (ATPe) was introduced as a potent activator of sperm motility and fertilizing ability. This study aimed to evaluate (1) levels of intracellular ATP in frozen-thawed epididymal cat sperm after incubation with ATPe and (2) effects of ATPe on epididymal cat sperm parameters after freezing and thawing. Eighteen male cats were included. For each replicate, epididymal sperm from two cats were pooled to one sample (N = 9). Each pooled sample was cryopreserved with the Tris-egg yolk extender into three straws. After thawing, the first and second straws were incubated with 0-, 1.0-, or 2.5-mM ATPe for 10 minutes and evaluated for sperm quality at 10 minutes, 1, 3, and 6 hours after thawing and fertilizing ability. The third straw was evaluated for intracellular ATP concentration in control and with 2.5-mM ATPe treatment. Higher concentration of intracellular sperm ATP was observed in the samples treated with 2.5-mM ATPe compared to the controls (0.339 ± 0.06 μg/2 × 10(6) sperm vs. 0.002 ± 0.003 μg/2 × 10(6) sperm, P ≤ 0.05). In addition, incubation with 2.5-mM ATPe for 10 minutes promoted sperm motility (56.7 ± 5.0 vs. 53.3 ± 4.4%, P ≤ 0.05) and progressive motility (3.1 ± 0.2 vs. 2.8 ± 0.4, P ≤ 0.05), mitochondrial membrane potential (36.4 ± 5.5 vs. 28.7 ± 4.8%, P ≤ 0.05), and blastocyst rate (36.1 ± 7.0 and 28.8 ± 7.4%, P ≤ 0.05) compared with the controls. In contrast, ATPe remarkably interfered acrosome integrity after 6 hours of postthawed incubation. In sum, the present finding that optimal incubation time of postthaw epididymal cat sperm under proper ATPe condition might constitute a rationale for the studies on other endangered wild felids regarding sperm quality and embryo development.

Alkaline phosphatase in boar sperm function

Alkaline phosphatase (AP) catalyses the detachment of phosphate residues from different substrates. Its activity has been demonstrated in seminal plasma and spermatozoa from porcine and other mammalian species; anyway, the role of AP in male reproduction has not been clarified yet and the aim of this study was to determine AP function in boar sperm capacitation and in vitro fertilization (IVF). AP activity was assayed in seminal plasma and in uncapacitated and in vitro capacitated (IVC) spermatozoa; in addition, capacitation was studied in presence of different doses of AP (1.2 and 2.5 IU/mL). The effect of different doses of AP (1.2 and 2.5 IU/mL) on several sperm parameters after IVC (viability, acrosome integrity with FITC-PSA, capacitation status with CTC staining, tyrosine phosphorylation) and on fertilizing ability during IVF were also evaluated. High AP activity was detected in seminal plasma, in particular in sperm-rich fraction; a lower activity was detected in uncapacitated spermatozoa while a significant decrease was evidenced after IVC. Viability was not changed by AP supplementation of the capacitating medium, whereas acrosome integrity and capacitation status were significantly affected by 1.2 and 2.5 doses, with a dose-dependent decrease in acrosome-reacted cells as well as in CTC B pattern displaying cells. As for sperm head protein phosphorylation, a decrease in relative fluorescence was detected in AP 2.5 group, if compared with capacitated one. After IVF, a dose-dependent decrease in penetrated oocytes was recorded, with an increase in monospermic zygote rate. In conclusion, we demonstrated that AP activity decreases under capacitating condition and that addition of AP to spermatozoa during capacitation results in a depression of the capacitating process and IVF. We can infer that AP plays a role in keeping spermatozoa quiescent until they are ejaculated and in modulating the acquisition of the fertilizing ability.

Metabolic determinants of electrical failure in ex-vivo canine model of cardiac arrest: evidence for the protective role of inorganic pyrophosphate

RATIONALE

Deterioration of ventricular fibrillation (VF) into asystole or severe bradycardia (electrical failure) heralds a fatal outcome of cardiac arrest. The role of metabolism in the timing of electrical failure remains unknown.

OBJECTIVE

To determine metabolic factors of early electrical failure in an ex-vivo canine model of cardiac arrest (VF+global ischemia).

METHODS AND RESULTS

Metabolomic screening was performed in left ventricular biopsies collected before and after 0.3, 2, 5, 10 and 20 min of VF and global ischemia. Electrical activity was monitored via plunge needle electrodes and pseudo-ECG. Four out of nine hearts exhibited electrical failure at 10.1±0.9 min (early-asys), while 5/9 hearts maintained VF for at least 19.7 min (late-asys). As compared to late-asys, early-asys hearts had more ADP, less phosphocreatine, and higher levels of lactate at some time points during VF/ischemia (all comparisons p<0.05). Pre-ischemic samples from late-asys hearts contained ∼25 times more inorganic pyrophosphate (PPi) than early-asys hearts. A mechanistic role of PPi in cardioprotection was then tested by monitoring mitochondrial membrane potential (ΔΨ) during 20 min of simulated-demand ischemia using potentiometric probe TMRM in rabbit adult ventricular myocytes incubated with PPi versus control group. Untreated myocytes experienced significant loss of ΔΨ while in the PPi-treated myocytes ΔΨ was relatively maintained throughout 20 min of simulated-demand ischemia as compared to control (p<0.05).

CONCLUSIONS

High tissue level of PPi may prevent ΔΨm loss and electrical failure at the early phase of ischemic stress. The link between the two protective effects may involve decreased rates of mitochondrial ATP hydrolysis and lactate accumulation.