HE2beta and HE2gamma, new members of an epididymis-specific family of androgen-regulated proteins in the human

Distinct actions of testicular endocrine and lumicrine signaling on the proximal epididymal transcriptome

The epididymal function and gene expression in mammals are under the control of the testis. Sex steroids are secreted from the testis and act on the epididymis in an endocrine manner. There is another, non-sex steroidal secreted signaling, named lumicrine signaling, in which testis-derived secreted proteins go through the male reproductive tract and act on the epididymis. The effects of such multiple regulations on the epididymis by the testis have been investigated for many genes. The recent development of high-throughput next-generation sequencing now enables us a further comparative survey of endocrine and lumicrine action-dependent gene expression. In the present study, testis-derived endocrine and lumicrine actions on epididymal gene expression were comparatively investigated by RNA-seq transcriptomic analyses. This investigation utilized experimental animal models in which testis-derived endocrine and/or lumicrine actions were interfered with, such as unilateral or bilateral orchidectomy. By bilateral orchidectomy, which interferes with both endocrine and lumicrine actions, 431 genes were downregulated. By unilateral orchidectomy, which also interferes with endocrine and lumicrine actions by the unilateral testis, but the endocrine action was compensated by the contralateral testis, 283 genes were downregulated. The content of such genes downregulated by unilateral orchidectomy was like those of lumicrine action-interfered efferent duct-ligation, W/Wv, and Nell2-/- mice. When genes affected by unilateral and bilateral orchidectomy were compared, 154 genes were commonly downregulated, whereas 217 genes were specifically downregulated only by bilateral orchidectomy, indicating the distinction between endocrine and lumicrine actions on the proximal epididymal transcriptome. Comparative transcriptome analyses also showed that the expressions of genes emerging since Amniota were notably impacted by bilateral orchidectomy, unilateral orchidectomy, and lumicrine action-interfering treatments; the degree of influence from these treatments varied based on the evolutionary stage beyond Amniota. These findings unveil an evolutional transition of regulated gene expression in the proximal epididymis by two different testis-derived signaling mechanisms.

Busulfan administration replicated the characteristics of the epididymal initial segment observed in mice lacking testis-epididymis lumicrine signaling

The physiological functions of the mammalian epididymis are typically regulated by the testes. In addition to sex steroids secreted by testicular Leydig cells, which act on the epididymis in an endocrine manner, there is a non-sex-steroidal signaling pathway known as the lumicrine pathway. This lumicrine signaling pathway involves ligand proteins secreted from germ cells within the testicular seminiferous tubules traversing the male reproductive tract, which induce epithelial differentiation in the epididymis. These findings prompted an inquiry into whether treatments influencing testis physiology can disrupt epididymal function by interfering with testis-epididymis communication. Busulfan, an alkylating agent commonly used to deplete testicular germ cells in reproductive biology, has not been sufficiently explored because of its effects on the epididymis. This study investigated the effects of busulfan administration on the proximal epididymis using histological and transcriptomic analyses. Notably, busulfan, as opposed to the vehicle dimethyl sulfoxide (DMSO), altered the morphology of the initial segment of the epididymis, leading to a reduction in the cell height of the luminal epithelium. RNA sequencing identified 185 significantly downregulated genes in the proximal epididymis of busulfan-administered mice compared to DMSO-administered mice. Comparative transcriptome analyses revealed similarities between the epididymal transcriptome of busulfan-administered mice and lumicrine-deficient mice, such as efferent-duct-ligated W/Wv and Nell2-/- mice. However, this differed from that of bilaterally orchidectomized mice, in which both the endocrine and lumicrine signaling pathways were simultaneously ablated. Collectively, these results suggested that the harmful effects of busulfan on the proximal epididymis are secondary consequences of the ablation of testis-epididymis lumicrine signaling.

Non-Invasive Diagnostics of Male Spermatogenesis from Seminal Plasma: Seminal Proteins

The compounds of seminal plasma have great potential as biomarkers of male fertility and can be used as a diagnostic tool for types of azoospermia. Azoospermia occurs in approximately 1% of the male population, and for an effective therapy of this form of male infertility, it is important to distinguish between obstructive and non-obstructive azoospermia. Proteins in seminal plasma can serve as biomarkers for diagnosing azoospermia. Considering the various types of obstructions, a combination of multiple proteins is advisable for diagnostic purposes. In this context, testicular and epididymal proteins are particularly significant, as they are specific to these tissues and typically absent in ejaculate during most obstructions. A combination of multiple biomarkers is more effective than the analysis of a single protein. This group of markers contains TEX101 and ECM1 proteins, combined detections of these two bring a diagnostic output with a high sensitivity and specificity. Similar results were observed for combined detection of TEX101 and SPAG1. The effective using of specific biomarkers from seminal plasma can significantly improve the existing approaches to diagnosis of the causes of male infertility.

Ablation of the sperm-associated antigen 11A (SPAG11A) protein by active immunization promotes epididymal oncogenesis in the rat

Incidence of cancer in the epididymis is very rare. It is proposed that proteins specific to this organ may contribute to this unique property. We previously demonstrated that siRNA-mediated knockdown of SPAG11A mRNA resulted in increased proliferation of epididymal epithelial cells, whereas overexpression of this gene caused reduced proliferation in immortalized cell lines. In this study, we evaluated the oncogenesis-related anatomical and transcriptome changes in the epididymis of SPAG11A-immunized rats challenged with a low dose of diethyl nitrosamine (DEN). DEN treatment or SPAG11A immunization alone did not cause any histopathological changes in the epididymis. Interestingly, indications of oncogenesis were observed in SPAG11A-immunized + DEN-treated rats. Using high throughput sequencing, we observed that 3549 transcripts that were differentially expressed in the caput epididymis of DEN only-treated rats displayed similar differential expression in the caput epididymis of SPAG11A-immunized rats, indicating that the microenvironment that contributes to oncogenesis sets in when SPAG11A protein is ablated. Differential expression of genes that are involved in 10 major cancer related pathways was also analyzed. Majority of the genes related to these pathways that were differentially expressed in the caput epididymis of DEN only-treated rats also showed similar pattern in the caput epididymis of SPAG11A-immunized rats. For the first time, results of our study demonstrate that ablation of SPAG11A by active immunization renders the epididymis susceptible to oncogenesis and that this protein may be one of the factors that contributes to the rarity of epididymal cancer.

Sperm acquire epididymis-derived proteins through epididymosomes

STUDY QUESTION

Are epididymosomes implicated in protein transfer from the epididymis to spermatozoa?

SUMMARY ANSWER

We characterized the contribution of epididymal secretions to the sperm proteome and demonstrated that sperm acquire epididymal proteins through epididymosomes.

WHAT IS KNOWN ALREADY

Testicular sperm are immature cells unable to fertilize an oocyte. After leaving the testis, sperm transit along the epididymis to acquire motility and fertilizing abilities. It is well known that marked changes in the sperm proteome profile occur during epididymal maturation. Since the sperm is a transcriptional and translational inert cell, previous studies have shown that sperm incorporate proteins, RNA and lipids from extracellular vesicles (EVs), released by epithelial cells lining the male reproductive tract.

STUDY DESIGN, SIZE, DURATION

We examined the contribution of the epididymis to the post-testicular maturation of spermatozoa, via the production of EVs named epididymosomes, released by epididymal epithelial cells. An integrative analysis using both human and mouse data was performed to identify sperm proteins with a potential epididymis-derived origin. Testes and epididymides from adult humans (n = 9) and adult mice (n = 3) were used to experimentally validate the tissue localization of four selected proteins using high-resolution confocal microscopy. Mouse epididymal sperm were co-incubated with carboxyfluorescein succinimidyl ester (CFSE)-labeled epididymosomes (n = 4 mice), and visualized using high-resolution confocal microscopy.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Adult (12-week-old) C57BL/CBAF1 wild-type male mice and adult humans were used for validation purposes. Testes and epididymides from both mice and humans were obtained and processed for immunofluorescence. Mouse epididymal sperm and mouse epididymosomes were obtained from the epididymal cauda segment. Fluorescent epididymosomes were obtained after labeling the epididymal vesicles with CFSE dye followed by epididymosome isolation using a density cushion. Immunofluorescence was performed following co-incubation of sperm with epididymosomes in vitro. High-resolution confocal microscopy and 3D image reconstruction were used to visualize protein localization and sperm-epididymosomes interactions.

MAIN RESULTS AND THE ROLE OF CHANCE

Through in silico analysis, we first identified 25 sperm proteins with a putative epididymal origin that were conserved in both human and mouse spermatozoa. From those, the epididymal origin of four sperm proteins (SLC27A2, EDDM3B, KRT19 and WFDC8) was validated by high-resolution confocal microscopy. SLC27A2, EDDM3B, KRT19 and WFDC8 were all detected in epithelial cells lining the human and mouse epididymis, and absent from human and mouse seminiferous tubules. We found region-specific expression patterns of these proteins throughout the mouse epididymides. In addition, while EDDM3B, KRT19 and WFDC8 were detected in both epididymal principal and clear cells (CCs), SLC27A2 was exclusively expressed in CCs. Finally, we showed that CFSE-fluorescently labeled epididymosomes interact with sperm in vitro and about 12-36% of the epididymosomes contain the targeted sperm proteins with an epididymal origin.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

The human and mouse sample size was limited and our results were descriptive. The analyses of epididymal sperm and epididymosomes were solely performed in the mouse model due to the difficulties in obtaining epididymal luminal fluid human samples. Alternatively, human ejaculated sperm and seminal EVs could not be used because ejaculated sperm have already contacted with the fluids secreted by the male accessory sex glands, and seminal EVs contain other EVs in addition to epididymosomes, such as the abundant prostate-derived EVs.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings indicate that epididymosomes are capable of providing spermatozoa with a new set of epididymis-derived proteins that could modulate the sperm proteome and, subsequently, participate in the post-testicular maturation of sperm cells. Additionally, our data provide further evidence of the novel role of epididymal CCs in epididymosome production. Identifying mechanisms by which sperm mature to acquire their fertilization potential would, ultimately, lead to a better understanding of male reproductive health and may help to identify potential therapeutic strategies to improve male infertility.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Spanish Ministry of Economy and Competitiveness (Ministerio de Economía y Competividad; fondos FEDER 'una manera de hacer Europa' PI13/00699 and PI16/00346 to R.O.; and Sara Borrell Postdoctoral Fellowship, Acción Estratégica en Salud, CD17/00109 to J.C.), by National Institutes of Health (grants HD040793 and HD069623 to S.B., grant HD104672-01 to M.A.B.), by the Spanish Ministry of Education, Culture and Sports (Ministerio de Educación, Cultura y Deporte para la Formación de Profesorado Universitario, FPU15/02306 to F.B.), by a Lalor Foundation Fellowship (to F.B. and M.A.B.), by the Government of Catalonia (Generalitat de Catalunya, pla estratègic de recerca i innovació en salut, PERIS 2016-2020, SLT002/16/00337 to M.J.), by Fundació Universitària Agustí Pedro i Pons (to F.B.), and by the American Society for Biochemistry and Molecular Biology (PROLAB Award from ASBMB/IUBMB/PABMB to F.B.). Confocal microscopy and transmission electron microscopy was performed in the Microscopy Core facility of the Massachusetts General Hospital (MGH) Center for Systems Biology/Program in Membrane Biology which receives support from Boston Area Diabetes and Endocrinology Research Center (BADERC) award DK57521 and Center for the Study of Inflammatory Bowel Disease grant DK43351. The Zeiss LSM800 microscope was acquired using an NIH Shared Instrumentation Grant S10-OD-021577-01. The authors have no conflicts of interest to declare.

Transgenesis and active immunization mediated reduction of sperm associated antigen 11A mRNA and protein levels affect fecundity in the rat

Spermatozoa acquire motility and fertilizing ability during their transit through the epididymis. A wide variety of proteins secreted into the epididymal lumen are added on to the sperm surface to allow morphological and molecular changes involved in sperm maturation. Proteins of the Sperm Associated Antigen 11 (SPAG11) family are known to be localized on the sperm surface. The rat SPAG11A protein was implicated in sperm maturation during epididymal transit in vitro. However, systematic analyses on the significance of SPAG11A in fertility and sperm function is not yet reported in vivo. In this study, using testicular electroporation, we generated transgenic rats that express shRNA to ablate endogenous Spag11a mRNA. Genotyping revealed the integration of the plasmid that expresses shRNA against Spag11a mRNA. Significant decrease in the mRNA levels of Spag11a and its encoded protein was observed in the caput epididymis of transgenic rats. We also generated an active immunization rat model to ablate endogenous SPAG11A protein by administering recombinant SPAG11A protein. Immunized rats had a high antibody titer in the serum and the tissue fluids of caput, cauda and testis. In both these model systems, the litter size and sperm count was significantly reduced. However, spermatozoa obtained from the transgenic or immunized rats underwent capacitation and acrosome reaction and the associated calcium release. Results of this study indicate the role of SPAG11A in fecundity and sperm production and not in sperm function, especially capacitation and acrosome reaction.

Male reproductive tract antimicrobial expression in the extremes of ages of rats

Alterations in the global gene expression profile are considered to contribute to the various physiological and pathological changes during the course of ageing. Genes that code for the molecular components of the innate system are alter markedly as ageing occurs; and this may define the susceptibility of very young and very old individuals to reproductive tract infections. The expression pattern of genes that code for beta-defensins (effectors of innate immune response) in male reproductive tract tissues of different stages of ageing is not yet reported. Further, the induction of beta-defensins during endotoxin challenge and whether epigenetic modulators can influence the expression of these genes in different stages of ageing are not reported. We analyzed the basal mRNA levels of beta-defensins and defensin-like proteins (Sperm Associated Antigen 11 (SPAG11) family members), their induction during endotoxin challenge and modulation by epigenetic modifiers (Trichostatin A and Azacytidine) in the caput, cauda, testis, prostate and seminal vesicle of rats that represent early stage to late stages of life (20 day to 730 day old). We observed differential basal gene expression pattern in the male reproductive tract tissues and the induction by LPS was not consistent neither among the age groups not the tissues analyzed. Trichostatin A and Azacytidine also influenced antimicrobial gene expression and the pattern was not consistent in different tissues obtained from different age groups. Results of this study demonstrate that antimicrobial gene expression varies to a great extent during ageing and is strongly influenced by endotoxins and epigenetic modulators.

Epididymal approaches to male contraception

Today, a vast arsenal of contraceptive methods interfering at different levels of the female reproductive axis is available. This is not the case for men for whom, until now, there is no reliable male reversible method and for whom vasectomy, condom and withdrawal are the only options available. Despite this limited supply, more than one third of all contraceptive methods used worldwide rely on the cooperation of the male partner. Besides developing hormonal approaches to stop sperm production, there may be attractive approaches that will interfere with sperm functions rather than production. Sperm functions are primarily established during post-testicular maturation, with the epididymis accounting for the majority. The purpose of this review is to present some of the promising and/or already abandoned leads that emerge from research efforts targeting the epididymis and its activities as potential means to achieve male post-meiotic contraception.

Novel androgen-induced activity of an antimicrobial β-defensin: Regulation of Wolffian duct morphogenesis

The Wolffian duct (WD) undergoes morphological changes induced by androgens to form the epididymis, which is an organ essential for sperm maturation. Androgen action in WD epithelium involves paracrine factors of mesenchymal origin that function by still poorly understood mechanisms. Here we studied the antimicrobial β-defensin SPAG11C as a new player in duct morphogenesis, localized prenatally in the WD mesenchyme. Organotypic culture of rat WDs and tissues from Androgen Receptor (AR) knockout mice (ARKO) were used. Our results show that androgen/AR signaling differentially regulated SPAG11C expression at mRNA and protein levels in the developing WD. WDs incubated with recombinant human SPAG11C were shorter and less coiled as a result of reduced epithelial cell proliferation, but not increased apoptosis. Our results suggested β-defensin SPAG11C as an androgen-target required for WD morphogenesis. This highlights the multifunctional repertoire of the β-defensin protein family and their potential contribution to the in utero environment that determines male reproductive success.

β-defensins and the epididymis: contrasting influences of prenatal, postnatal, and adult scenarios

β-defensins are components of host defense, with antimicrobial and pleiotropic immuno-modulatory properties. Research over the last 15 years has demonstrated abundant expression of a variety of β-defensins in the postnatal epididymis of different species. A gradient of region- and cell-specific expression of these proteins is observed in the epithelium of the postnatal epididymis. Their secretion into the luminal fluid and binding to spermatozoa as they travel along the epididymis has suggested their involvement in reproduction-specific tasks. Therefore, continuous attention has been given to various β-defensins for their role in sperm function and fertility. Although β-defensins are largely dependent on androgens, the underlying mechanisms regulating their expression and function in the epididymis are not well understood. Recent investigation has pointed out to a new and interesting scenario where β-defensins emerge with a different expression pattern in the Wolffian duct, the embryonic precursor of the epididymis, as opposed to the adult epididymis, thereby redefining the concept concerning the multifunctional roles of β-defensins in the developing epididymis. In this review, we summarize some current views of β-defensins in the epididymis highlighting our most recent data and speculations on their role in the developing epididymis during the prenatal-to-postnatal transition, bringing attention to the many unanswered questions in this research area that may contribute to a better understanding of epididymal biology and male fertility.

Targeted inactivation of the mouse epididymal beta-defensin 41 alters sperm flagellar beat pattern and zona pellucida binding

During epididymal maturation, sperm acquire the ability to swim progressively by interacting with proteins secreted by the epididymal epithelium. Beta-defensin proteins, expressed in the epididymis, continue to regulate sperm motility during capacitation and hyperactivation in the female reproductive tract. We characterized the mouse beta-defensin 41 (DEFB41), by generating a mouse model with iCre recombinase inserted into the first exon of the gene. The homozygous Defb41(iCre/iCre) knock-in mice lacked Defb41 expression and displayed iCre recombinase activity in the principal cells of the proximal epididymis. Heterozygous Defb41(iCre/+) mice can be used to generate epididymis specific conditional knock-out mouse models. Homozygous Defb41(iCre/iCre) sperm displayed a defect in sperm motility with the flagella primarily bending in the pro-hook conformation while capacitated wild-type sperm more often displayed the anti-hook conformation. This led to a reduced straight line motility of Defb41(iCre/iCre) sperm and weaker binding to the oocyte. Thus, DEFB41 is required for proper sperm maturation.

Potential Use of Antimicrobial Peptides as Vaginal Spermicides/Microbicides

The concurrent increases in global population and sexually transmitted infection (STI) demand a search for agents with dual spermicidal and microbicidal properties for topical vaginal application. Previous attempts to develop the surfactant spermicide, nonoxynol-9 (N-9), into a vaginal microbicide were unsuccessful largely due to its inefficiency to kill microbes. Furthermore, N-9 causes damage to the vaginal epithelium, thus accelerating microbes to enter the women's body. For this reason, antimicrobial peptides (AMPs), naturally secreted by all forms of life as part of innate immunity, deserve evaluation for their potential spermicidal effects. To date, twelve spermicidal AMPs have been described including LL-37, magainin 2 and nisin A. Human cathelicidin LL-37 is the most promising spermicidal AMP to be further developed for vaginal use for the following reasons. First, it is a human AMP naturally produced in the vagina after intercourse. Second, LL-37 exerts microbicidal effects to numerous microbes including those that cause STI. Third, its cytotoxicity is selective to sperm and not to the female reproductive tract. Furthermore, the spermicidal effects of LL-37 have been demonstrated in vivo in mice. Therefore, the availability of LL-37 as a vaginal spermicide/microbicide will empower women for self-protection against unwanted pregnancies and STI.

Dynamic changes in the spatio-temporal expression of the β-defensin SPAG11C in the developing rat epididymis and its regulation by androgens

Herein, we characterized the spatio-temporal expression, cellular distribution and regulation by androgens of the β-defensin SPAG11C, the rat ortholog of the human SPAG11B isoform C, in the developing epididymis by using RT-PCR, in situ hybridization and immunohistochemistry. We observed that Spag11c mRNA was ubiquitously expressed in rat fetuses, but preferentially detected in male reproductive tissues at adulthood. SPAG11C (mRNA and protein) was prenatally mainly detected in the mesenchyme of the Wolffian duct, switching gradually after birth to a predominant localization in the epididymis epithelium during postnatal development. In the adult epididymis, smooth muscle and interstitial cells were also identified as sources of SPAG11C. Furthermore, SPAG11C was differentially immunolocalized on spermatozoa surface during their transit from testis throughout caput and cauda epididymis. Developmental and surgical castration studies suggested that androgens contribute to the epididymal cell type- and region-specific modulation of SPAG11C mRNA levels and immunolocalization. Together our findings provide novel insights into the potential role of β-defensins in the epididymis.

Molecular modeling of the human sperm associated antigen 11 B (SPAG11B) proteins

Antimicrobial proteins and peptides are ubiquitous in nature with diverse structural and biological properties. Among them, the human beta-defensins are known to contribute to the innate immune response. Besides the defensins, a number of defensin-like proteins and peptides are expressed in many organ systems including the male reproductive system. Some of the protein isoforms encoded by the sperm associated antigen 11B (SPAG11) gene in humans are beta-defensin-like and exhibit structure dependent and salt tolerant antimicrobial activity, besides contributing to sperm maturation. Though some of the functional roles of these proteins are reported, the structural and molecular features that contribute to their antimicrobial activity is not yet reported. In this study, using in silico tools, we report the three dimensional structure of the human SPAG11B proteins and their C-terminal peptides. web-based hydropathy, amphipathicity, and topology (WHAT) analyses and grand average of hydropathy (GRAVY) indices show that these proteins and peptides are amphipathic and highly hydrophilic. Self-optimized prediction method with alignment (SOPMA) analyses and circular dichroism data suggest that the secondary structure of these proteins and peptides primarily contain beta-sheet and random coil structure and alpha-helix to a lesser extent. Ramachandran plots show that majority of the amino acids in these proteins and peptides fall in the permissible regions, thus indicating stable structures. The secondary structure of SPAG11B isoforms and their peptides were not perturbed with increasing NaCl concentration (0-300 mM) and at different pH (3, 7, and 10), thus reinforcing our previously reported observation that their antimicrobial activity is salt tolerant. To the best of our knowledge, for the first time, results of our study provide vital information on the structural features of SPAG11B protein isoforms and their contribution to antimicrobial activity.

Albumin is synthesized in epididymis and aggregates in a high molecular mass glycoprotein complex involved in sperm-egg fertilization

The epididymis has an important role in the maturation of sperm for fertilization, but little is known about the epididymal molecules involved in sperm modifications during this process. We have previously described the expression pattern for an antigen in epididymal epithelial cells that reacts with the monoclonal antibody (mAb) TRA 54. Immunohistochemical and immunoblotting analyses suggest that the epitope of the epididymal antigen probably involves a sugar moiety that is released into the epididymal lumen in an androgen-dependent manner and subsequently binds to luminal sperm. Using column chromatography, SDS-PAGE with insitu digestion and mass spectrometry, we have identified the protein recognized by mAb TRA 54 in mouse epididymal epithelial cells. The ∼65 kDa protein is part of a high molecular mass complex (∼260 kDa) that is also present in the sperm acrosomal vesicle and is completely released after the acrosomal reaction. The amino acid sequence of the protein corresponded to that of albumin. Immunoprecipitates with anti-albumin antibody contained the antigen recognized by mAb TRA 54, indicating that the epididymal molecule recognized by mAb TRA 54 is albumin. RT-PCR detected albumin mRNA in the epididymis and fertilization assays invitro showed that the glycoprotein complex containing albumin was involved in the ability of sperm to recognize and penetrate the egg zona pellucida. Together, these results indicate that epididymal-derived albumin participates in the formation of a high molecular mass glycoprotein complex that has an important role in egg fertilization.

Transcriptional regulation of the rat sperm-associated antigen 11e (Spag 11e) gene during endotoxin challenge

The lipopolysaccharide (LPS) inducible expression of antimicrobial proteins of the Sperm-Associated Antigen 11 (Spag11) family is dependent on nuclear factor-κB (NF-κB) activation and epigenetic factors. However, the regulatory mechanisms that govern their gene expression during endotoxin challenge are unknown. In this study, we demonstrate that the Spag11e gene upstream sequence contains binding sites for androgen receptor (AR), NF-κB, nuclear factor-1, E-twenty-six and activator protein 2. The role of these transcription factors in inducing Spag11e gene during LPS challenge was analysed by measuring luciferase activity in HEK cells transiently transfected with deletion constructs that lacked one or more of the binding sites. Deletion of AR-binding site resulted in loss of luciferase activity and no further decrease was observed when progressive deletions of the other transcription factor binding sites were made. Mutations in AR or NF-κB binding site resulted in loss of luciferase activity. Electrophoretic gel-mobility shift assays indicated that AR and NF-κB proteins bind to the synthesised radio-labelled oligomers used as probes and the mobility shifted when respective antibodies were added. Results of this study indicate the direct involvement of AR and NF-κB in LPS-induced Spag11e expression, thereby expanding our understanding of antimicrobial gene expression during endotoxin challenge.

Sperm-associated antigen 11A is expressed exclusively in the principal cells of the mouse caput epididymis in an androgen-dependent manner

BACKGROUND

Epididymal sperm maturation occurs via interactions between sperm and proteins secreted by the epididymal epithelium. Although this is an important process, the genes that encode the involved proteins remain largely uncharacterized. Previous studies have demonstrated that the genes involved in sperm maturation are regulated by androgen. Spag11a is an epididymal gene that is influenced by androgen. However, little is known about the putative role of this gene in the sperm maturation process. The objective of this study was to characterize Spag11a in the mouse epididymis.

METHODS

In silico analyses were performed to predict signal peptides and functional domains. Spag11a expression was measured by quantitative real-time RT-PCR. Western blots and immunocytochemistry were performed to determine protein expression.

RESULTS

SPAG11A is a member of the beta defensin protein family and constitutes a secretory protein. Spag11a was expressed exclusively in the epididymis. Moreover, it exhibited region-specific expression in the caput, which is typical for genes that are involved in creating a suitable microenvironment for sperm maturation. Mouse Spag11a was regulated by androgen. A significant decrease of Spag11a expression was observed at third day following a gonadectomy (P < 0.001). Interestingly, testosterone replacement therapy was able to maintain the expression almost at the normal level, indicating a dependency on androgen. Besides androgen, testicular factors influenced Spag11a expression in a different way. This was revealed by efferent duct ligation in which Spag11a was transiently up-regulated at the third day following the ligation before returning to the normal level at day 5. Spag11a regional expression was also observed at protein level detected by western immunoblotting which revealed a clear band in the caput but not in other regions. The prediction that SPAG11A is a secretory protein was confirmed by immunocytochemical analyses indicating cell-specific expression mainly in the caput principal cells and detection of the protein in epididymal luminal fluid and spermatozoa.

CONCLUSIONS

Based on the characteristics of Spag11a, it is likely that this gene has a specific role in epididymal sperm maturation. Further studies using functional assays are necessary to confirm this finding.

Les approches épididymaires de la contraception masculine

L’offre en matière de moyens contraceptifs masculins est limitée et, en particulier, à ce jour il n’existe pas de contraception hormonale masculine sur le marché. L’épididyme, dans lequel les spermatozoïdes acquièrent leurs capacités fécondantes et où ils sont stockés, s’avère être un site intéressant à cibler. Cette revue vise à présenter de façon synthétique les quelques pistes prometteuses qui ont émergé ces dernières années.

Genomic organization, tissue distribution and functional characterization of the rat Pate gene cluster

The cysteine rich prostate and testis expressed (Pate) proteins identified till date are thought to resemble the three fingered protein/urokinase-type plasminogen activator receptor proteins. In this study, for the first time, we report the identification, cloning and characterization of rat Pate gene cluster and also determine the expression pattern. The rat Pate genes are clustered on chromosome 8 and their predicted proteins retained the ten cysteine signature characteristic to TFP/Ly-6 protein family. PATE and PATE-F three dimensional protein structure was found to be similar to that of the toxin bucandin. Though Pate gene expression is thought to be prostate and testis specific, we observed that rat Pate genes are also expressed in seminal vesicle and epididymis and in tissues beyond the male reproductive tract. In the developing rats (20-60 day old), expression of Pate genes seem to be androgen dependent in the epididymis and testis. In the adult rat, androgen ablation resulted in down regulation of the majority of Pate genes in the epididymides. PATE and PATE-F proteins were found to be expressed abundantly in the male reproductive tract of rats and on the sperm. Recombinant PATE protein exhibited potent antibacterial activity, whereas PATE-F did not exhibit any antibacterial activity. Pate expression was induced in the epididymides when challenged with LPS. Based on our results, we conclude that rat PATE proteins may contribute to the reproductive and defense functions.

Characterization of a novel lysozyme-like 4 gene in the rat

Lysozyme-like proteins (LYZLs) belong to the class of c-type lysozymes and are not well characterized in many species including the rat. In this study, using in silico and molecular biology techniques, we report the identification, cloning and characterization of rat Lyzl4 gene and also determine the expression pattern of Lyzl1, Lyzl3 and Lyzl6. The rat Lyzl genes were found to be distributed on three chromosomes and all of them retained the characteristic eight cysteine signature of c-type lysozyme. Homology modeling of rat LYZL4 indicated that its structure is similar to that of the mouse SLLP1. In the male reproductive tract of rat, Lyzl gene expression was confined to the testis. Lyzl1 and Lyzl4 were found to be expressed in tissues beyond the male reproductive tract, whereas Lyzl3 and Lyzl6 were not. Lyzl expression in the developing (10-60 day old) rats was androgen dependent in the testis. Immunodetection using antibodies against rat LYZL4 revealed the presence of LYZL4 protein in the germinal layer of the testes and on the sperm tail. Recombinant LYZL4 did not exhibit antibacterial, muramidase and isopeptidase activities characteristic to c-type lysozyme. To the best of our knowledge, for the first time we report the characterization of Lyzl genes in the rat. Results of our study indicate that rat LYZL proteins may have an important role in male reproductive tract function.

Functional studies of eppin

Our laboratory has characterized EPPIN [epididymal protease inhibitor; SPINLW1] as a novel gene on human chromosome 20q12-13.2, which encodes a cysteine-rich protein of 133 amino acids with a calculated molecular mass of 15.283 kDa, containing both Kunitz-type and WAP (whey acidic protein)-type four-disulfide core consensus sequences. Eppin is secreted by Sertoli cells in the testis and epididymal epithelial cells; it is predominantly a dimer, although multimers often exist, and in its native form eppin is found on the human sperm surface complexed with LTF (lactotransferrin) and clusterin. During ejaculation SEMG (semenogelin) from the seminal vesicles binds to the eppin protein complex, initiating a series of events that define eppin's function. Eppin's functions include (i) modulating PSA (prostate-specific antigen) enzyme activity, (ii) providing antimicrobial protection and (iii) binding SEMG thereby inhibiting sperm motility. As PSA hydrolyses SEMG in the ejaculate coagulum, spermatozoa gain progressive motility. We have demonstrated that eppin is essential for fertility because immunization of male monkeys with recombinant eppin results in complete, but reversible, contraception. To exploit our understanding of eppin's function, we are developing compounds that inhibit eppin–SEMG interaction and mimic anti-eppin, inhibiting sperm motility. These compounds should have potential as a male contraceptive.

Antibacterial and antiviral roles of a fish β-defensin expressed both in pituitary and testis

Defensins are a group of cationic peptides that exhibit broad-spectrum antimicrobial activity. In this study, we cloned and characterized a β-defensin from pituitary cDNA library of a protogynous hermaphroditic orange-spotted grouper (Epinephelus coioides). Interestingly, the β-defensin was shown to be dominantly expressed in pituitary and testis by RT-PCR and Western blot analysis, and its transcript level is significantly upregulated in reproduction organs from intersexual gonad to testis during the natural and artificial sex reversal. Promoter sequence and the responsible activity region analyses revealed the pituitary-specific POU1F1a transcription binding site and testis-specific SRY responsible site, and demonstrated that the pituitary-specific POU1F1a transcription binding site that locates between −180 and −208 bp is the major responsible region of grouper β-defensin promoter activity. Immunofluorescence localization observed its pituicyte expression in pituitary and spermatogonic cell expression in testis. Moreover, both in vitro antibacterial activity assay of the recombinant β-defensin and in vivo embryo microinjection of the β-defensin mRNA were shown to be effective in killing Gram-negative bacteria. And, its antiviral role was also demonstrated in EPC cells transfected with the β-defensin construct. Additionally, the antibacterial activity was sensitive to concentrations of Na⁺, K⁺, Ca²⁺ and Mg²⁺. The above intriguing findings strongly suggest that the fish β-defensin might play significant roles in both innate immunity defense and reproduction endocrine regulation.

The human male reproductive tract antimicrobial peptides of the HE2 family exhibit potent synergy with standard antibiotics

Reproductive tract infections pose a serious threat to health and fertility. Due to the emergence of antibiotic resistant pathogens, antimicrobial proteins and peptides of the reproductive tract are extensively characterized in recent years toward developing newer strategies to treat genital tract infections. Pathogen growth inhibition using a combination of naturally occurring male reproductive tract antimicrobial peptides and commonly used antibiotics has not been reported. Checker board analyses were carried out to determine the nature of interaction (synergistic, additive and antagonistic) between HE2alpha and HE2beta2 peptides and the commonly used antibiotics. Using Escherichia coli as the target organism, the minimal inhibitory concentration and fractional inhibitory concentration indices were determined. We demonstrate for the first time that the human male reproductive tract antimicrobial peptides HE2alpha and HE2beta2 act synergistically with the commonly used antibiotics to inhibit E. coli growth. A combination of HE2alpha and HE2beta2 peptides resulted in an additive effect. Interestingly, the synergistic effects of HE2 peptides were highest with doxycycline and ciprofloxacin, antibiotics generally used to treat epididymitis. Results of this study demonstrate the potential of endogenous HE2 peptides to be pharmacologically important in designing novel strategies to treat reproductive tract infections.

Lipopolysaccharide-induced epididymitis disrupts epididymal beta-defensin expression and inhibits sperm motility in rats

Although more than 40 beta-defensins have been identified in rat epididymis, little is known about their regulation or their relation to male infertility caused by inflammation. Using a rat model of epididymitis induced by lipopolysaccharide (LPS), we examined expression of SPAG11E (also known as Bin1b), a caput epididymis-specific beta-defensin in rat. Unlike the expression of other beta-defensins in various epithelial cells with upregulated expression after LPS stimulation, expression of SPAG11E was significantly decreased by LPS at the mRNA and protein levels. LPS treatment also significantly decreased both sperm binding to SPAG11E and sperm motility, and supplementation of the spermatozoa with recombinant SPAG11E in vitro remarkably increased both SPAG11E binding and motility of sperm. To clarify whether decreased expression is a common pattern of epididymal beta-defensins after LPS stimulation, we examined the expression of another 12 epididymal beta-defensins expressed in the caput epididymis. For nine of these beta-defensins, expression was decreased, but for the other three, expression remained unaffected. These findings demonstrate that LPS-induced epididymitis can decrease the expression of epididymal beta-defensins and that disruption of SPAG11E expression is involved in the impairment of sperm motility.

Novel partners of SPAG11B isoform D in the human male reproductive tract

Human sperm-associated antigen 11 (SPAG11) is closely related to beta-defensins in structure, expression, and function. Like the beta-defensins, SPAG11 proteins are predominantly expressed in the male reproductive tract, where their best-known major roles are in innate host defense and reproduction. Although several hypotheses have emerged to describe the evolution of beta-defensin and SPAG11 multifunctionality, few describe these multiple functions in terms of defensin interactions with specific proteins. To gain insight into the protein interaction potentials of SPAG11 and the signaling pathways that SPAG11 may influence, we used a yeast two-hybrid screening of a human testis-epididymis library. The results reveal human SPAG11B isoform D (SPAG11B/D) interactions with tryptase alpha/beta 1 (TPSAB1), tetraspanin 7 (TSPAN7), and attractin (ATRN). These interactions were confirmed by coimmunoprecipitation and glutathione S-transferase affinity matrix binding. SPAG11B/D and the three interacting proteins are expressed in the proximal epididymis, and all function in immunity and fertility pathways. We analyzed the functional consequences of SPAG11B/D interaction with TPSAB1 and showed that SPAG11B/D is both a substrate and a potent inhibitor of TPSAB1 activity. Furthermore, we show that (like SPAG11B/D) TSPAN7 and ATRN are associated with spermatozoa.

Immunolocalization of alpha(1A)-adrenoceptors in rat and human epididymis

Immunohistochemistry was conducted to analyze the cellular localization of alpha(1A)-adrenoceptors along rat and human epididymis. ADR-A, a polyclonal antibody that recognizes the specific C-terminal region of alpha(1A)-adrenoceptors, immunostained this adrenoceptor subtype in smooth muscle cells surrounding the epididymal tubules and interstitial blood vessels and in subpopulations of epithelial cells from adult rat and human caput and cauda epididymidis. The same cell types from rat epididymidis were immunostained by ADR-1, a polyclonal antibody that recognizes a common region of the three alpha(1)-adrenoceptor subtypes, alpha(1A), alpha(1B), and alpha(1D). Immunostaining with both antibodies was also conducted in adult rat and human vas deferens and seminal vesicle used as positive controls because of the abundance of alpha(1A)-adrenoceptors in these tissues. ADR-A- and ADR-1-positive immunostaining was differentially distributed depending on the antibody, method of tissue fixation (Bouin-fixed and fresh frozen tissues), species (rat and human), tissue (caput and cauda epididymidis), and age (immature and adult rats) analyzed. This is the first report immunolocalizing alpha(1A)-adrenoceptor along rat and human epididymis. The presence of this adrenoceptor subtype in epididymal smooth muscle and epithelial cells indicates their contribution to smooth muscle contractile responses and a possible role in the absorptive and/or secretory activities of the epithelium lining the epididymal duct. Taken together, our results should contribute to a better understanding of the physiological role of alpha(1)-adrenoceptors in the epididymidis and the importance of the sympathetic nervous system for male (in)fertility.

Presence and subcellular localizations of surfactant proteins A and D in human spermatozoa

OBJECTIVE

To investigate the presence of surfactant protein-A (SP-A); molecular weight 34 kDa and surfactant protein-D (SP-D); and molecular weight 43 kDa in human spermatozoa.

DESIGN

Prospective, research study.

SETTING

Two universities in Turkey.

PATIENT(S)

Semen specimens (n = 10) were obtained from normozoospermic donors.

INTERVENTION(S)

Human sperm were exposed to an anti-human SP-A polyclonal antibody, and monoclonal antibody, to human SP-D protein.

MAIN OUTCOME MEASURE(S)

Presence of SP-A and SP-D proteins in human beings.

RESULT(S)

Indirect immunofluorescence assays of human sperm indicated the presence of SP-A in the mid piece, the tail, and sometimes at the equatorial region of spermatozoa. A brilliant green light detected SP-D in the tails and acrosome of some sperm. The anti-SP-A antibody detected a single band corresponding to the molecular weight values of 34 kDa in spermatozoa, whereas no band was observed in the negative control. The anti-SP-D antibody showed the expected band at 43 kDa in spermatozoa.

CONCLUSION(S)

This is the first report and a novel finding of the presence of surfactant glycoproteins on human spermatozoa.

Characterization and functions of beta defensins in the epididymis

The epididymal beta-defensins have evolved by repeated gene duplication and divergence to encode a family of proteins that provide direct protection against pathogens and also support the male reproductive tract in its primary function. Male tract defensins also facilitate recovery from pathogen attack. The beta-defensins possess ancient conserved sequence and structural features widespread in multi-cellular organisms, suggesting fundamental roles in species survival. Primate SPAG11, the functional fusion of two ancestrally independent beta-defensin genes, produces a large family of alternatively spliced transcripts that are expressed according to tissue-specific and species-specific constraints. The complexity of SPAG11 varies in different branches of mammalian evolution. Interactions of human SPAG11D with host proteins indicate involvement in multiple signaling pathways.

Novel aspects of the sperm-associated antigen 11 (SPAG11) gene organization and expression in cattle (Bos taurus)

Beta-defensins are small cationic peptides exhibiting broad spectrum antimicrobial properties. In humans, many beta-defensin genes are located within a cluster on chromosome 8p23. The sperm associated antigen 11 (SPAG11) gene is contained in this cluster and is unusual among the human beta-defensins due to its complex genomic structure and mRNA splicing pattern. Here we report the genomic organization of the Bos taurus SPAG11 gene located on chromosome 27q1.2, within a cluster of beta-defensin genes. The exon structures of the fused bovine SPAG11 gene and of the mosaic transcripts initiated at both A and B promoters were established, including identification of novel exons and transcripts not previously found in primate or rodent. Evolutionary analysis against primate, rodent, canine, and porcine orthologs was performed. In adult bulls SPAG11C, SPAG11E, and SPAG11U mRNAs were detected predominantly in the male reproductive tract, while SPAG11D transcript was detected in reproductive and nonreproductive tissues and SPAG11V and SPAG11W mRNAs were confined to testis. Differential expression of all six transcripts was observed in tissues from fetal and adult bulls, suggesting that similar mRNA splicing mechanisms govern SPAG11 gene expression during pre- and postnatal development. Immunolocalization of SPAG11C and SPAG11D/E was demonstrated in the epithelium of the epididymis and testis, and SPAG11D in association with epididymal spermatozoa. Recombinant full-length SPAG11D protein was strongly antibacterial, while the SPAG11E C-terminal peptide that contains the beta-defensin motif in its structure was somewhat less potent. Taken together, the results suggest that SPAG11 isoforms perform both immune and reproductive functions in cattle.

Synthesis and structure-activity relationship of beta-defensins, multi-functional peptides of the immune system

beta-defensins are a large family of multiple disulfide-bonded peptides occurring in mammals and birds. They play an important role in the innate immune system, directly killing microbial organisms. Recent research has demonstrated that beta-defensins are important for other biological functions beyond antimicrobial effects, including inhibition of viral infection, interaction with Toll-like receptors, chemotactic effects, and sperm function. The corresponding broad spectrum of activities makes this peptide class an important subject and tool in immunologic research. In this review, we summarize the current status of the routes to obtain synthetic beta-defensins, their major structural properties and structure-activity relationship.

Identification, cloning and functional characterization of novel sperm associated antigen 11 (SPAG11) isoforms in the rat

BACKGROUND

Sperm binding proteins and their C-terminal peptides of the Sperm Associated Antigen 11 (SPAG11) family were found to play an important role in epididymal innate immunity in addition to their role in sperm maturation. However, the expression of Spag11 transcripts in rodents is not well documented.

METHODS

Computational analysis was employed to identify novel Spag11 isoforms in the rat. RT-PCR analyses were carried out on RNAs isolated from the male reproductive tract tissues of rat using gene specific primers for Spag11c and Spag11t. The identities of PCR products were confirmed by sequencing. Tissue distribution, developmental expression and androgen regulation of Spag11t and Spag11c were studied using RT-PCR. The antimicrobial activities of recombinant Spag11t and Spag11c were tested against E coli in a colony forming unit assay.

RESULTS

In this study, we identified two novel Spag11 transcripts, namely, Spag11t and Spag11c derived from the long arm of chromosome 16 in the rat (Rattus norvegicus), using both in silico and molecular biology approaches. Spag11c is expressed in all three regions of the epididymis, in testis and in ovary but is absent from the seminal vesicle. Spag11t expression is confined to the caput and it is not expressed in the testis, seminal vesicle or ovary. Age dependent expression of Spag11t and Spag11c was observed in the epididymides of rats (10-60 day old). Their expression was found to be most abundant in the adult rat (60 day) suggesting roles in mature reproductive function. Further, both Spag11t and Spag11c expression was down regulated in castrated rat epididymides and the expression was maintained in the testosterone replaced castrated rats. SPAG11C is a potent antibacterial agent. SPAG11T also displayed bactericidal capacity although weaker than SPAG11C and SPAG11E.

CONCLUSION

The abundant expression of Spag11t and Spag11c in the male reproductive tract suggests an important role in male reproductive tract immunity. Their expression is developmentally regulated and androgen dependent. Characterization of novel SPAG11 isoforms will contribute to our understanding of the role of epididymal proteins in sperm maturation and innate immunity.

Cells positive for microtubule-associated protein 1B (MAP 1B) are present along rat and human efferent ductules and epididymis

Microtubule-associated protein 1B (MAP 1B) is a neuronal cytoskeleton marker with predominant expression in the developing nervous system. The present study provides evidence for the expression of this cytoskeleton protein in non-neuronal and neuronal cells along rat and human efferent ductules and epididymis (initial segment, caput, and cauda). Reverse transcription/polymerase chain reaction and Western blot analysis were used to confirm the presence of MAP 1B (mRNA and protein) in rat tissues. Immunohistochemical studies revealed MAP-1B-positive staining in columnar ciliated cells present in efferent ductules and in narrow cells located in the initial segment, in both rat and human. MAP-1B-positive basal cells, located underneath the columnar cells, were only identified in the initial segment and caput epididymidis of the rat. Qualitative analysis of tissues from 40-day-old and 120-day-old rats indicated that the number of MAP-1B-positive ciliated, narrow, and basal cells per tubule increased with sexual maturation. These immunoreactive cells did not stain for dopamine beta-hydroxylase or acetylcholinesterase, indicating that they were not adrenergic or cholinergic in nature. Immunohistochemical studies also revealed the presence of MAP-1B-positive staining in interstitial nerve fibers in caput and cauda epididymidis from both rat and human. Thus, the expression of MAP 1B is not confined to a specific cell type in rat and human efferent ductules and epididymis. The functional significance of this cytoskeleton protein in tissues from the male reproductive tract requires further investigation.

Identification, cloning and functional characterization of novel beta-defensins in the rat (Rattus norvegicus)

BACKGROUND

Beta-defensins are small cationic peptides that exhibit broad spectrum antimicrobial properties. The majority of beta-defensins identified in humans are predominantly expressed in the male reproductive tract and have roles in non-immunological processes such as sperm maturation and capacitation. Characterization of novel defensins in the male reproductive tract can lead to increased understanding of their dual roles in immunity and sperm maturation.

METHODS

In silico rat genomic analyses were used to identify novel beta-defensins related to human defensins 118-123. RNAs isolated from male reproductive tract tissues of rat were reverse transcribed and PCR amplified using gene specific primers for defensins. PCR products were sequenced to confirm their identity. RT-PCR analysis was performed to analyze the tissue distribution, developmental expression and androgen regulation of these defensins. Recombinant defensins were tested against E. coli in a colony forming unit assay to analyze their antimicrobial activities.

RESULTS

Novel beta-defensins, Defb21, Defb24, Defb27, Defb30 and Defb36 were identified in the rat male reproductive tract. Defb30 and Defb36 were the most restricted in expression, whereas the others were expressed in a variety of tissues including the female reproductive tract. Early onset of defensin expression was observed in the epididymides of 10-60 day old rats. Defb21-Defb36 expression in castrated rats was down regulated and maintained at normal levels in testosterone supplemented animals. DEFB24 and DEFB30 proteins showed potent dose and time dependent antibacterial activity.

CONCLUSION

Rat Defb21, Defb24, Defb27, Defb30 and Defb36 are abundantly expressed in the male reproductive tract where they most likely protect against microbial invasion. They are developmentally regulated and androgen is required for full expression in the adult epididymis.

Antimicrobial Actions of Human and Macaque Sperm Associated Antigen (SPAG) 11 Isoforms: influence of the N-terminal peptide

In addition to their role in sperm maturation, recent evidence has indicated that epididymal proteins have a role in male reproductive tract innate immunity. Herein we demonstrate that human and macaque epididymal protein isoforms in the SPAG (sperm associated antigen) 11 family, full length SPAG11C, K and L exhibit potent antibacterial activity against E. coli. Analysis of activities of the N- and C-terminal domains revealed that the human N-terminal peptide is bactericidal, while the C-terminal domains that contain the defensin-like 6 cysteine array in SPAG11C and partial arrays in SPAG11K and SPAG11L, lack antibacterial activity. The N-terminal peptide does not appear to contain all the determinants of activity since full-length human SPAG11C is more active than the isolated N-terminal peptide and since sulfhydryl reduction and alkylation, which would affect primarily the C-terminal peptides, completely abolished activities of the whole proteins. These results suggest that the structure conferred by the disulfide bonds in human SPAG11C contributes to the antibacterial activity of the whole molecule. The activities of the N-terminal peptide and of full length human SPAG11C were somewhat reduced in increasing NaCl concentrations. In contrast, the antibacterial activities of full length macaque SPAG11C, K and L were unaffected by the presence of NaCl suggesting a mechanism in the macaque that is less dependent upon electrostatic interactions. SPAG11C, K and L disrupted E. coli membranes but had no effect on erythrocyte membranes. Inhibition of E. coli RNA, DNA and protein synthesis by nonlethal concentrations of SPAG11 isoforms indicated an additional mechanism of bacterial killing.

Human antimicrobial peptides: defensins, cathelicidins and histatins

Antimicrobial peptides, which have been isolated from many bacteria, fungi, plants, invertebrates and vertebrates, are an important component of the natural defenses of most living organisms. The isolated peptides are very heterogeneous in length, sequence and structure, but most of them are small, cationic and amphipathic. These peptides exhibit broad-spectrum activity against Gram-positive and Gram-negative bacteria, yeasts, fungi and enveloped viruses. A wide variety of human proteins and peptides also have antimicrobial activity and play important roles in innate immunity. In this review we discuss three important groups of human antimicrobial peptides. The defensins are cationic non-glycosylated peptides containing six cysteine residues that form three intramolecular disulfide bridges, resulting in a triple-stranded beta-sheet structure. In humans, two classes of defensins can be found: alpha-defensins and beta-defensins. The defensin-related HE2 isoforms will also be discussed. The second group is the family of histatins, which are small, cationic, histidine-rich peptides present in human saliva. Histatins adopt a random coil conformation in aqueous solvents and form alpha-helices in non-aqueous solvents. The third group comprises only one antimicrobial peptide, the cathelicidin LL-37. This peptide is derived proteolytically from the C-terminal end of the human CAP18 protein. Just like the histatins, it adopts a largely random coil conformation in a hydrophilic environment, and forms an alpha-helical structure in a hydrophobic environment.

Molecular cloning and characterization of three beta-defensins from canine testes

Mammalian beta-defensins are small cationic peptides possessing broad antimicrobial and physiological activities. Because dogs are particularly resilient to sexually transmitted diseases, it has been proposed that their antimicrobial peptide repertoire might provide insight into novel antimicrobial therapeutics and treatment regimens. To investigate this proposal, we cloned the full-length cDNA of three canine beta-defensin isoforms (cBD-1, -2, and -3) from canine testicular tissues. Their predicted peptides share identical N-terminal 65-amino-acid residues, including the beta-defensin consensus six-cysteine motif. The two longer isoforms, cBD-2 and -3, possess 4 and 34 additional amino acids, respectively, at the C terminus. To evaluate the antimicrobial activity of cBD, a 34-amino-acid peptide derived from the shared mature peptide region was synthesized. Canine beta-defensin displayed broad antimicrobial activity against gram-positive bacteria (Listeria monocytogenes and Staphylococcus aureus; MICs of 6 and 100 mug/ml, respectively), gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae, and Neisseria gonorrhoeae; MICs of 20 to 50, 20, and 50 mug/ml, respectively), and yeast (Candida albicans; MIC of 5 to 50 mug/ml) and lower activity against Ureaplasma urealyticum and U. canigenitalium (MIC of 200 mug/ml). Antimicrobial potency was significantly reduced at salt concentrations higher than 140 mM. All three canine beta-defensins were highly expressed in testis. In situ hybridization indicated that cBD-1 was expressed primarily in Sertoli cells within the seminiferous tubules. In contrast, cBD-2 was located primarily within Leydig cells. The longest isoform, cBD-3, was detected in Sertoli cells and to a lesser extent in the interstitium. The tissue-specific expression and broad antimicrobial activity suggest that canine beta-defensins play an important role in host defense and other physiological functions of the male reproductive system.

Expression of an antimicrobial peptide identified in the male reproductive system of rats

Bin1b is a beta-defensins-like molecule originally isolated from the rat epididymis. Owing to its bactericidal activity, Bin1b may have therapeutic properties suitable for the treatment of sexually transmitted diseases. The amino terminus of the mature Bin1b peptide contains a conserved myristoylated Gly residue. We studied the requirement of the terminal myristoylated Gly residue in the bactericidal activity of Bin1b and found that the terminal myristoylated Gly residue is not essential for the bactericidal activity. In addition, we expressed the tandem repeats of Bin1b in Escherichia coli and found that two tandem repeats of Bin1b protein were successfully expressed. The bacterially expressed tandem Bin1b repeats may be used in a diverse array of biochemical and cell biological studies.

Differential Expression and Antibacterial Activity of Epididymis Protein 2 Isoforms in the Male Reproductive Tract of Human and Rhesus Monkey (Macaca mulatta)1

The epididymis protein 2 (EP2) gene, the fusion of two ancestral beta-defensin genes, is highly expressed in the epididymis and subject to species-specific regulation at the levels of promoter selection, transcription, and mRNA splicing. EP2 mRNA expression is also androgen dependent, and at least two of the secreted proteins bind spermatozoa. Alternative splicing produces more than 17 different EP2 mRNA variants. In this article, the expression of EP2 variants was profiled in different tissues from the human and rhesus monkey (Macaca mulatta) male reproductive tract using reverse transcriptase-polymerase chain reaction. Different EP2 mRNA variants were identified not only in human and rhesus testis and epididymis but also in the novel sites, seminal vesicle and prostate. Immunolocalization of EP2 protein in epithelial cells from rhesus and human seminal vesicle demonstrated that EP2 transcripts are translated in these tissues. In addition, two novel splicing variants, named EP2R and EP2S, were discovered. EP2C was the only splice variant expressed in all tissues tested from rhesus monkey. However, expression was not detected in human testis or seminal vesicle. For the first time, bactericidal function was demonstrated for EP2C, EP2K, and EP2L. Taken together, the results indicate that EP2 expression is more widespread in the male reproductive tract than realized previously. Whereas the activity of every EP2 variant tested thus far is antibacterial, further investigation may reveal additional physiological roles for EP2 peptides in the primate male reproductive tract.

Antimicrobial Activity of Human EPPIN, an Androgen-Regulated, Sperm-Bound Protein with a Whey Acidic Protein Motif1

The role of epididymal sperm-binding proteins in reproductive tract immunity is now well recognized in addition to their role in sperm maturation. Spermatozoa acquire forward motility and fertilizing ability during their passage through the epididymis, where they acquire a wide variety of proteins belonging to different classes. Previously, we demonstrated that EPPIN (epididymal protease inhibitor), an androgen-regulated, sperm-binding protein containing protease-inhibitory motifs, is expressed specifically in the testis and epididymis. In the present study, we investigated the antibacterial activity of EPPIN against Escherichia coli and the mechanism of antimicrobial action. EPPIN exhibited dose- and time-dependent antibacterial activity that was relatively insensitive to salt. However, EPPIN lost its antibacterial activity completely on reduction and alkylation of its cysteines, indicating the importance of disulfide bonds for its activity. EPPIN permeabilized the outer and inner membranes of E. coli, which is consistent with its ability to induce striking morphological alterations of E. coli membranes as shown by scanning electron microscopy. EPPIN did not cause disruption of eukaryotic membranes in the rat erythrocyte hemolytic assay. The present results indicate that EPPIN has a role in the innate immune system of human epididymis.

Antimicrobial actions of the human epididymis 2 (HE2) protein isoforms, HE2alpha, HE2beta1 and HE2beta2

BACKGROUND

The HE2 gene encodes a group of isoforms with similarities to the antimicrobial beta-defensins. We demonstrated earlier that the antimicrobial activity of HE2 proteins and peptides is salt resistant and structure dependent and involves permeabilization of bacterial membranes. In this study, we further characterize the antimicrobial properties of HE2 peptides in terms of the structural changes induced in E. coli and the inhibition of macromolecular synthesis.

METHODS

E. coli treated with 50 microg/ml of HE2alpha, HE2beta1 or HE2beta2 peptides for 30 and 60 min were visualized using transmission and scanning electron microscopy to investigate the impact of these peptides on bacterial internal and external structure. The effects of HE2alpha, HE2beta1 and HE2beta2 on E. coli macromolecular synthesis was assayed by incubating the bacteria with 2, 10 and 25 microg/ml of the individual peptides for 0-60 min and measuring the incorporation of the radioactive precursors [methyl-3H]thymidine, [5-3H]uridine and L-[4,5-3H(N)]leucine into DNA, RNA and protein. Statistical analyses using Student's t-test were performed using Sigma Plot software. Values shown are Mean +/- S.D.

RESULTS

E. coli treated with HE2alpha, HE2beta1 and HE2beta2 peptides as visualized by transmission electron microscopy showed extensive damage characterized by membrane blebbing, thickening of the membrane, highly granulated cytoplasm and appearance of vacuoles in contrast to the smooth and continuous membrane structure of the untreated bacteria. Similarly, bacteria observed by scanning electron microscopy after treating with HE2alpha, HE2beta1 or HE2beta2 peptides exhibited membrane blebbing and wrinkling, leakage of cellular contents, especially at the dividing septa, and external accumulation of fibrous materials. In addition, HE2alpha, HE2beta1 and HE2beta2 peptides inhibited E. coli DNA, RNA and protein synthesis.

CONCLUSIONS

The morphological changes observed in E. coli treated with epididymal HE2 peptides provide further evidence for their membrane dependent mechanism of antibacterial action. HE2 C-terminal peptides can inhibit E. coli macromolecular synthesis, suggesting an additional mechanism of bacterial killing supplementary to membrane permeabilization.

The androgen-regulated epididymal sperm-binding protein, human beta-defensin 118 (DEFB118) (formerly ESC42), is an antimicrobial beta-defensin

Spermatozoa bind a variety of proteins as they pass through the proximal regions of the epididymis, where they acquire forward motility and fertilizing ability. Recent evidence indicates that certain epididymis-specific secretory proteins that bind sperm have antibacterial activity and may function as part of the innate immune system. We reported earlier that ESC42, now designated human beta-defensin 118 (DEFB118), is a sperm-binding protein. In this study, we demonstrate that DEFB118 has potent antibacterial activity that is dose, time, and structure dependent. Incubation of Escherichia coli for 60 min with 10 microg/ml DEFB118 reduced bacterial survival to 20% of the control, and 25 microg/ml reduced survival to 5% of the control. DEFB118 concentrations of 50 and 100 microg/ml further reduced survival to less than 2 and 1%, respectively. A biphasic effect of salt concentration on the antibacterial activity of DEFB118 was observed. Reduction of disulfide bonds and alkylation of cysteines resulted in the complete loss of antibacterial activity. DEFB118 caused rapid permeabilization of both outer and inner membranes of E. coli and striking morphological alterations in the bacterial surfaces visible by scanning electron microscopy consistent with a membrane-disruptive mechanism of bacterial killing. In contrast, eukaryotic cell membranes were not permeabilized by DEFB118, as indicated by the rat erythrocyte hemolytic assay. Studies on DEFB118 inhibition of macromolecular synthesis and membrane permeability in E. coli were consistent with a primary effect at the cell membrane level. DEFB118 may contribute to epididymal innate immunity and protect the sperm against attack by microorganisms in the male and female reproductive tracts.

Complement C4b-binding protein as a novel murine epididymal secretory protein

Complement C4b-binding protein (C4BP) is a plasma protein synthesized in the liver and plays a regulatory role in the host defense complement system. We have previously reported that mRNAs of the C4BP alpha chain (C4BPalpha) are expressed at significant levels in the guinea pig and mouse epididymis in an androgen-dependent manner. Here, we analyze the murine C4bpa gene and show that epididymal and liver C4BPalpha mRNAs are generated from a single-copy gene and that the epididymal C4BPalpha mRNAs are transcribed from novel transcription start sites located approximately 100 base pairs downstream from those used in the liver. Furthermore, in an immunohistochemical study using rabbit anti-mouse C4BP antiserum, we demonstrated that C4BP is localized in the stereocilia and Golgi apparatus of the epididymal epithelial cells and the surfaces of spermatozoa in the lumen in the region from the distal caput to the cauda but not in the proximal caput region. Indirect immunofluorescence of the isolated spermatozoa demonstrated that C4BP is localized preferentially on the head region of the spermatozoa, and immunoelectron microscopy located C4BP on the plasma membrane and the outer acrosomal membrane. These results indicate that epididymal C4BP is synthesized in the epithelial cells and secreted into the lumen in a region-restricted manner and is taken up to the sperm membranes on passage through the epididymis. Many epididymal proteins are secreted from the epithelial cells in a region-specific and androgen-dependent manner and are considered to contribute to sperm maturation. Our findings suggest a novel function of C4BP as one such epididymal secretory protein.

LCN6, a novel human epididymal lipocalin

BACKGROUND

The lipocalin (LCN) family of structurally conserved hydrophobic ligand binding proteins is represented in all major taxonomic groups from prokaryotes to primates. The importance of lipocalins in reproduction and the similarity to known epididymal lipocalins prompted us to characterize the novel human epididymal LCN6.

METHODS AND RESULTS

LCN6 cDNA was identified by database analysis in a comprehensive human library sequencing program. Macaca mulatta (rhesus monkey) cDNA was obtained from an epididymis cDNA library and is 93% homologous to the human. The gene is located on chromosome 9q34 adjacent LCN8 and LCN5. LCN6 amino acid sequence is most closely related to LCN5, but the LCN6 beta-barrel structure is best modeled on mouse major urinary protein 1, a pheromone binding protein. Northern blot analysis of RNAs isolated from 25 human tissues revealed predominant expression of a 1.0 kb mRNA in the epididymis. No other transcript was detected except for weak expression of a larger hybridizing mRNA in urinary bladder. Northern hybridization analysis of LCN6 mRNA expression in sham-operated, castrated and testosterone replaced rhesus monkeys suggests mRNA levels are little affected 6 days after castration. Immunohistochemical staining revealed that LCN6 protein is abundant in the caput epithelium and lumen. Immunofluorescent staining of human spermatozoa shows LCN6 located on the head and tail of spermatozoa with the highest concentration of LCN6 on the post-acrosomal region of the head, where it appeared aggregated into large patches.

CONCLUSIONS

LCN6 is a novel lipocalin closely related to Lcn5 and Lcn8 and these three genes are likely products of gene duplication events that predate rodent-primate divergence. Predominant expression in the epididymis and location on sperm surface are consistent with a role for LCN6 in male fertility.

ESP13.2, a member of the beta-defensin family, is a macaque sperm surface-coating protein involved in the capacitation process

Female macaques produced isoantibodies to a limited number of sperm surface proteins following immunization with sperm components released by phosphatidylinositol-specific phospholipase C (PI-PLC). Washed, acrosome-intact, fixed sperm injected into rabbits elicited a major immune response to one of the same PI-PLC-released proteins, which was shown to be a sperm surface-coating protein. After purification and digestion of the glycoprotein, four peptides were analyzed for amino acid sequence, and all had 100% homology with an epididymal secretory protein, ESP13.2, reported previously to be a small, cationic-rich peptide and a member of the beta-defensin family. Antibodies to purified ESP13.2 recognized a number of protein bands on Western blots of nonreduced PI-PLC-released sperm components and nonreduced whole-sperm extracts. After chemical disulfide reduction, only a single, broad band from 31 to 35 kDa was recognized by anti-ESP13.2 antibodies. Indirect immunofluorescence showed ESP13.2 over the entire surface of ejaculated macaque sperm. Fluorescence was only slightly reduced after sperm were washed through 80% Percoll. A 24-h incubation in capacitating medium significantly reduced the amount of ESP13.2 over the head and midpiece, whereas exposure of the incubated sperm to dbcAMP and caffeine (capacitation activators) resulted in almost complete loss of ESP13.2 from the sperm surface. After activation, ESP13.2 was the primary component released into the medium as judged electrophoretically. Lignosulfonic acid, a potent inhibitor of macaque fertilization in vitro, completely blocked release of ESP13.2 from the sperm surface, even following treatment with activators. These findings suggest that the beta-defensin, ESP13.2, has a function in the capacitation of macaque spermatozoa and may modulate sperm surface-receptor presentation at the time of fertilization.

EP2 splicing variants in rhesus monkey (Macaca mulatta) epididymis

The expression pattern of EP2 variants was examined in the rhesus monkey (Macaca mulatta). Using reverse transcriptase-polymerase chain reaction and rapid amplification of complementary cDNA protocols, 11 message variants were identified in rhesus epididymis, only three of which (EP2B, EP2C, and EP2E) have previously been reported. The most abundant variant found in human, EP2A, was not found in rhesus. Seven of the eight new rhesus EP2 variants (EP2J-EP2Q) use previously unidentified 5'-splicing sites in exon 3, and four variants use three previously unidentified exons whose counterparts are present in the human EP2 gene. Overall, 3 of the 11 variants, EP2C, EP2E, and EP2Q, code for beta-defensin-like peptides whose probable physiological role is to protect the male reproductive tract against microbial invasions. Because of the complex splicing pattern that causes some downstream exons to be read in any of the three reading frames, the N-termini of the other eight EP2 peptide variants consist of a partial beta-defensin motif with three cysteines, followed by amino acid sequences that have no recognizable homology to known proteins.

Antibacterial properties of the sperm-binding proteins and peptides of human epididymis 2 (HE2) family; salt sensitivity, structural dependence and their interaction with outer and cytoplasmic membranes of Escherichia coli

During passage through the epididymis, sperm interact with secreted epididymal proteins that promote maturation, including the acquisition of motility and fertilization competence. Viewed previously as distinct from sperm maturation, host defence capabilities are now recognized functions of the human epididymis 2 (HE2) family of sperm-binding proteins. We analysed the potent dose and time-dependent bactericidal activity of recombinant HE2alpha, HE2beta1 and HE2beta2 and found that the full-length proteins (10 microg/ml or approximately 1 microM) caused more than a 50% decrease in Escherichia coli colony forming units within 15 min. By contrast, human beta-defensin-1, at a similar concentration, required more than 90 min to exhibit similar antibacterial activity. The epididymis-specific lipocalin, LCN6, failed to kill bacteria. Higher concentrations (25-100 microg/ml) of HE2 proteins and a longer duration of treatment resulted in near total inhibition of bacterial growth. The C-terminal peptides of HE2alpha, HEbeta1 and HEbeta2 proteins exhibited antibacterial activity similar to their full-length counterparts, indicating that the antibacterial activity of HE2 proteins resides in these C-terminal regions. Antibacterial activities of HE2 proteins and peptides were slightly inhibited by NaCl concentrations of up to 150 mM, while human beta-defensin-1 activity was nearly eliminated. Reduction and alkylation of disulphide bonds in HE2 proteins and their C-terminal peptides abolished their antibacterial activity. Consistent with the ability to kill bacteria, full-length HE2 proteins and C-terminal peptides caused rapid dose-dependent permeabilization of outer and cytoplasmic E. coli membranes. A much longer exposure time was required for human beta-defensin-1-mediated permeabilization of membranes, suggesting a possible difference in mode of action compared with the HE2 antibacterial peptides.