Primate epididymis-specific proteins: characterization of ESC42, a novel protein containing a trefoil-like motif in monkey and human

β-defensin 118 attenuates inflammation and injury of intestinal epithelial cells upon enterotoxigenic Escherichia coli challenge

Background

Antimicrobial peptides including various defensins have been attracting considerable research interest worldwide, as they have potential to substitute for antibiotics. Moreover, AMPs also have immunomodulatory activity. In this study, we explored the role and its potential mechanisms of β-defensin 118 (DEFB118) in alleviating inflammation and injury of IPEC-J2 cells (porcine jejunum epithelial cell line) upon the enterotoxigenic Escherichia coli (ETEC) challenge.

Results

The porcine jejunum epithelial cell line (IPEC-J2) pretreated with or without DEFB118 (25 μg/mL) were challenged by ETEC (1×10⁶ CFU) or culture medium. We showed that DEFB118 pretreatment significantly increased the cell viability (P<0.05) and decreased the expressions of inflammatory cytokines such as the interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in IPEC-J2 cells exposure to ETEC (P<0.05). Interestingly, DEFB118 pretreatment significantly elevated the abundance of the major tight-junction protein zonula occludens-1 (ZO-1), but decreased the number of apoptotic cells upon ETEC challenge (P<0.05). The expression of caspase 3, caspase 8, and caspase 9 were downregulated by DEFB118 in the IPEC-J2 cells exposure to ETEC (P<0.05). Importantly, DEFB118 suppressed two critical inflammation-associated signaling proteins, nuclear factor-kappa-B inhibitor alpha (IκB-α) and nuclear factor-kappaB (NF-κB) in the ETEC-challenged IPEC-J2 cells.

Conclusions

DEFB118 can alleviate ETEC-induced inflammation in IPEC-J2 cells through inhibition of the NF-κB signaling pathway, resulting in reduced secretion of inflammatory cytokines and decreased cell apoptosis. Therefore, DEFB118 can act as a novel anti-inflammatory agent.

Study of microRNA Expression Profile in Different Regions of Ram Epididymis

The regional expression of epididymal genes provides a guarantee for sperm maturation. As a class of endogenous non-coding small RNAs, microRNAs (miRNAs) play an important role in spermatogenesis, maturation and fertilization. Currently, the regulatory role of miRNA in the epididymis is poorly understood. Here, transcriptome sequencing was used to analyse miRNA expression profiles in three regions of the epididymis of rams, including caput, corpus and cauda. The results showed that there were 13 known miRNAs between the caput and corpus controls, 29 between the caput and cauda and 22 differences between the corpus and cauda. Based on the analysis of miRNA target genes by GO and KEGG, a negative regulation network of miRNA-mRNA was constructed in which let-7, miR-541-5p, miR-133b and miR-150 may play an important regulatory role in the maturation regulation of ram epididymal sperm. This research provides a reference for studying the regulation mechanism of sperm maturation in male epididymis and improving semen quality and male reproductive performance.

The truncated human beta-defensin 118 can modulate lipopolysaccharide mediated inflammatory response in RAW264.7 macrophages

The family of human β-defensins consists of small cysteine-rich peptides, which are receiving significant attention due to their antimicrobial activity. The N-terminal cysteine motif of β-defensin is considered to contribute to its biological activity. Human β-defensin 118 (DEFB 118) is a particular anion β-defensin expressed predominantly in the male reproductive tract, but its physiological activity has not yet been revealed. In order to verify the potential role of the N-terminal domain of DEFB118 peptide in the regulation of infection, the truncated β-defensin core region of DEFB118 peptide was expressed with IMPACT-pTWIN1 system in Escherichia coli. Herein, the purified homogeneous DEFB118 peptide was identified by mass spectrometry and circular dichroism spectroscopy. The in vitro experiments revealed that DEFB118 peptide exhibited prominent LPS-binding potency (K_D: 2.94 nM). Moreover, the DEFB118 core peptide significantly inhibited the mRNA level of LPS-induced inflammatory cytokines including IL-α, IL-1β, IL-6 and TNF-α in RAW264.7 cells, and correspondingly decreased secretion of IL-6 and TNF-α. We concluded that strong binding of DEFB118 to LPS might prevent LPS from binding to its receptor, and hence inhibited cytokines secretion. The results of this study may be a benefit to elucidate the immune protection of DEFB118 in the male reproductive tract.

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.

Proteome profiling of the sperm maturation milieu in the rhesus monkey (Macaca mulatta) epididymis

The mammalian spermatozoon acquires its fertilising potential during transit through the epididymis, where it interacts with epididymal luminal fluid proteins (the sperm maturation milieu). In order to highlight the epididymal-specific function of the rhesus monkey (Macaca mulatta) in sperm maturation, two-dimensional gel electrophoresis of epididymal luminal fluid proteins was followed by identification by Matrix-Assisted Laser Desorption/ Ionization Time of Flight Mass Spectrometry (MALDI-TOF/MS) or MALDI-TOF/TOF and revealed over five hundred spots, comprising 198 non-redundant proteins. Some mass spectrometric data were confirmed by western blotting identification. Some common epididymal fluid proteins were identified, such as clusterin, α-1-antitrypsin, malate dehydrogenase, L-lactate dehydrogenase B, α-1-acid glycoprotein 1 and α-mannosidase. More than 7% of all proteins were anti-oxidative, which might control oxidative stress within the male tract. When compared with bull and human epididymal luminal fluid proteins, those in the rhesus monkey had more overlap with the human, which provides evidence of a close evolutionary relationship between the rhesus monkey and man. This study provides new proteomic information on possible rhesus monkey epididymal functions and novel potential biomarkers for the noninvasive assessment of male fertility.

Sperm Proteome Maturation in the Mouse Epididymis

In mammals, transit through the epididymis, which involves the acquisition, loss and modification of proteins, is required to confer motility and fertilization competency to sperm. The overall dynamics of maturation is poorly understood, and a systems level understanding of the complex maturation process will provide valuable new information about changes occurring during epididymal transport. We report the proteomes of sperm collected from the caput, corpus and cauda segments of the mouse epididymis, identifying 1536, 1720 and 1234 proteins respectively. This study identified 765 proteins that are present in sperm obtained from all three segments. We identified 1766 proteins that are potentially added (732) or removed (1034) from sperm during epididymal transit. Phenotypic analyses of the caput, corpus and cauda sperm proteomes identified 60 proteins that have known sperm phenotypes when mutated, or absent from sperm. Our analysis indicates that as much as one-third of proteins with known sperm phenotypes are added to sperm during epididymal transit. GO analyses revealed that cauda sperm are enriched for specific functions including sperm-egg recognition and motility, consistent with the observation that sperm acquire motility and fertilization competency during transit through the epididymis. In addition, GO analyses revealed that the immunity protein profile of sperm changes during sperm maturation. Finally, we identified components of the 26S proteasome, the immunoproteasome, and a proteasome activator in mature sperm.

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.

Spink13, an epididymis-specific gene of the Kazal-type serine protease inhibitor (SPINK) family, is essential for the acrosomal integrity and male fertility

Sperm maturation involves numerous surface modifications by a variety of secreted proteins from epididymal epithelia. The sperm surface architecture depends on correct localization of its components and highlights the importance of the sequence of the proteolytic processing of the sperm surface in the epididymal duct. The presence of several protease inhibitors from different families is consistent with the hypothesis that correctly timed epididymal protein processing is essential for proper sperm maturation. Here we show that the rat (Rattus norvegicus) epididymis-specific gene Spink13, an androgen-responsive serine protease inhibitor, could bind to the sperm acrosome region. Furthermore, knockdown of Spink13 in vivo dramatically enhanced the acrosomal exocytosis during the process of capacitation and thus led to a significant reduction in male fertility, indicating that Spink13 was essential for sperm maturation. We conclude that blockade of SPINK13 may provide a new putative target for post-testicular male contraceptives.

Cloning and primary characterizations of rLcn9, a new member of epididymal lipocalins in rat

Lipocalins are a structurally conserved and diversely functional family of proteins that are of potential importance in epididymis functions. The rat Lcn9 gene was cloned by in silico methods and genome walking based on homology to the rhesus monkey epididymal ESC513 and its polyclonal antisera were prepared. The rat Lcn9 gene is located on chromosome 3p13 spanning 7 exons, contains 2.3 kb and encodes 179 amino acids with a 17-amino acid signal peptide. Northern blot, western blot, and immunohistochemical staining analysis revealed that rat Lcn9 was a novel epididymis-specific gene, expressed selectively in the proximal caput region, influenced by luminal fluid testicular factors. Moreover, Lcn9 protein was modified by N-glycosylation and bound on the postacrosomal domain of caput sperm. In conclusion, the rat Lcn9 exhibited tissue-, region-, and temporal-specific expression patterns and its expression was regulated by luminal testicular factors. Its potential roles in sperm maturation are discussed.

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.

Effect of Rabbit Epididymal Antimicrobial Peptide, REHbβP, on LPS-Induced Proinflammatory Cytokine Responses in Human Vaginal Cells In Vitro

Antimicrobial peptides (AMP's) protect epithelial surfaces including epididymis against pathogens and play a key role in orchestrating various defensive responses. Recently, we have identified one such AMP, rabbit epididymal hemoglobin-β subuit (REHbβP) from the epididymal fluid of rabbit, Oryctologus cuniculus. The demonstration of a protective role of REHbβP in epididymal epithelial cells (EPEC's) led us to investigate: (1) the identification of LPS interactive domain in REHbβP, and (2) whether the REHbβP of rabbit origin mediates vaginal cellular immune responses of another species (human). HeLa-S3, human vaginal epithelial cells (hVECs) were exposed to LPS or the LPS-stimulated cells treated with REHbβP or neutral peptide, nREHbβP. Effect of LPS and cytokines (IL-6 and IL-1α) and chemokines (IL-8, MCP-1) levels was determined in the culture supernatants. In response to the LPS, hVECs synthesized these mediators and the levels were significantly higher than controls. This enhancing effect was ameliorated when the LPS-induced hVECs were treated with REHbβP. Similar results were obtained on NF-κB protein and hBD-1 mRNA expression. Confocal microscopy studies revealed that REHbβP attenuated the LPS-induced internalization of E. coli by macrophages. The chemotaxis studies performed using Boyden chamber Transwell assay, which showed elevated migration of U937 cells when the supernatants of LPS-induced hVECs were used, and the effect was inhibited by REHbβP. REHbβP was found to be localized on the acrosome of rabbit spermatozoa, suggesting its role in sperm protection beside sperm function. In conclusion, REHbβP may have the potential to develop as a therapeutic agent for reproductive tract infections (RTI's).

Literature and patent analysis of the cloning and identification of human functional genes in China

The Human Genome Project was launched at the end of the 1980s. Since then, the cloning and identification of functional genes has been a major focus of research across the world. In China too, the potentially profound impact of such studies on the life sciences and on human health was realized, and relevant studies were initiated in the 1990s. To advance China's involvement in the Human Genome Project, in the mid-1990s, Committee of Experts in Biology from National High Technology Research and Development Program of China (863 Program) proposed the "two 1%" goal. This goal envisaged China contributing 1% of the total sequencing work, and cloning and identifying 1% of the total human functional genes. Over the past 20 years, tremendous achievement has been accomplished by Chinese scientists. It is well known that scientists in China finished the 1% of sequencing work of the Human Genome Project, whereas, there is no comprehensive report about "whether China had finished cloning and identifying 1% of human functional genes". In the present study, the GenBank database at the National Center of Biotechnology Information, the PubMed search tool, and the patent database of the State Intellectual Property Office, China, were used to retrieve entries based on two screening standards: (i) Were the newly cloned and identified genes first reported by Chinese scientists? (ii) Were the Chinese scientists awarded the gene sequence patent? Entries were retrieved from the databases up to the cut-off date of 30 June 2011 and the obtained data were analyzed further. The results showed that 589 new human functional genes were first reported by Chinese scientists and 159 gene sequences were patented (http://gene.fudan.sh.cn/introduction/database/chinagene/chinagene.html). This study systematically summarizes China's contributions to human functional genomics research and answers the question "has China finished cloning and identifying 1% of human functional genes?" in the affirmative.

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.

The epididymis-specific antimicrobial peptide β-defensin 15 is required for sperm motility and male fertility in the rat (Rattus norvegicus)

Spermatozoa acquire forward motility and fertilizing capacity during their transit through the epididymis. The maturation process involves modifications of the sperm surface by different proteins that are secreted by a series of specialized regions in the epididymal epithelium. Here we show that the rat epididymis-specific β-defensin 15 (Defb15) exhibits an androgen-dependent expression pattern, and it can bind to the acrosomal region of caput sperm. Coculture of caput spermatozoa with Defb15 antibody in vitro resulted in a significant decline in sperm motility. Moreover, the total and progressive motility of the spermatozoa dramatically decreased in rats when Defb15 was downregulated by lentivirus-mediated RNAi in vivo. Remarkably, knock down of Defb15 led to a reduction in fertility and embryonic development failure. In addition, the recombinant Defb15 showed antimicrobial activity in a dose-dependent fashion. These results suggest that Defb15 plays a dual role in both sperm maturation and pathogen defense in rat epididymis.

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.

Human ribonuclease 9, a member of ribonuclease A superfamily, specifically expressed in epididymis, is a novel sperm-binding protein

To explore the functions of human ribonuclease 9 (RNase 9), we constructed a mammalian fusion expression vector pcDNA-hRNase9, prepared recombinant human RNase 9-His fusion protein from HEK293T cells and determined its N-terminal amino acid sequences. According to the determined mature protein, recombinant human RNase 9 was prepared in E. coli. Ribonucleolytic activity and antibacterial activity of recombinant human RNase 9 were detected, and the distribution of human RNase 9 on tissues and ejaculated spermatozoa and in vitro capacitated spermatozoa were analyzed via indirect immunofluorescence assay. The results showed that recombinant human RNase 9 did not exhibit detectable ribonucleolytic activity against yeast tRNA, but exhibited antibacterial activity, in a concentration/time dependent manner, against E. coli. Immunofluorescent analyses showed that the predicted human RNase 9 was present throughout the epididymis, but not present in other tissues examined, and human RNase 9 was also present on the entire head and neck regions of human ejaculated spermatozoa and in vitro capacitated spermatozoa. These results suggest that human RNase 9 may play roles in host defense of male reproductive tract.

Beta-defensin 22 is a major component of the mouse sperm glycocalyx

Surface components of sperm isolated from the cauda epididymides were stabilized by whole sperm fixation for immunization of rabbits. The resulting immunoglobulins (Igs) recognized a single protein of 130 kDa (non-reduced) or 54-57 kDa (reduced) on western blots of cauda sperm. Igs recognized the same 54-57 kDa protein band on whole tissue blots of the corpus and cauda epididymidis and vas deferens. No immunoreactive bands were detected on blots of the prostate, seminal vesicles, testes, caput epididymis, or any of various non-reproductive tissues. Removal of sperm from the vas deferens prior to blotting eliminated the detection of the sperm antigen. Antibodies raised to synthetic peptides, identical in amino acid sequence to two unique spans of DEFB22, recognized the same 130/54-57 kDa antigen on western blots of both caudal sperm and the purified antigen isolated with the anti-sperm Ig. From indirect immunofluorescence, both the anti-sperm and anti-peptide Igs appeared to localize to the entire sperm surface, a pattern confirmed at the ultrastructural level. Real-time PCR identified the corpus epididymides as the major site of expression of DEFB22, with negligible expression in the testes, caput epididymides, and vas deferens. Immunostaining of epididymal sections showed DEFB22 being released into the lumen at the distal caput/proximal corpus, with sperm becoming intensely coated with DEFB22 as they reached the distal corpus. Most uterine sperm recovered from mice 4 h following copulation exhibited DEFB22 coating the entire sperm surface. By contrast, some sperm recovered from the oviduct and cumulus extracellular matrix showed loss of DEFB22 from the sperm head.

Transcriptome analysis of a cDNA library from adult human epididymis

Mammalian Gene Collection (MGC) verified over 9000 human full-ORF genes and FLJ Program reported 21 243 cDNAs of which 14 409 were unique ones and 5416 seemed to be protein-coding. The pity is that epididymis cDNA library was missing in their sequencing target list. Epididymis is a very important male accessory sex organ for sperm maturation and storage. Fully differentiated spermatozoa left from testis acquire their motility and capacity for fertilization via interactions with the epididymal epithelium duct lumen during passage through this convoluted duct. Here, we report that 20 000 clones from a healthy male epididymis cDNA library have been sequenced. The sequencing data provided 8234 known sequences and 650 unknown cDNA fragments. Hundred and six of 650 unknown cDNA clone inserts were randomly selected for fully sequencing. There were 25 unknown unique sequences and 19 released but unreported sequences came out. By northern blot analysis, four sequences randomly selected from the 19 released sequences with no known function showed positive mRNA signals in epididymis and testis. The signals for three of six from those unknown group showed as epididymis abundant in a region-specific manner but not in the testis and other tissues tested. All the sequencing data will be available on the website www.sdscli.com.

Comparative genomic analysis of a mammalian beta-defensin gene cluster

Comparative genomic analyses have yielded valuable insights into conserved and divergent aspects of gene function, regulation, and evolution. Herein, we describe the characterization of a mouse beta-defensin gene cluster locus on chromosome 2F6. In addition, we present the evolutionary analysis of this cluster and its human, rhesus, and rat orthologs. Expression analysis in mouse revealed the occurrence of defensin cluster transcripts in multiple tissues, with the highest abundance in the urogenital tract. Molecular evolutionary analysis suggests that this cluster originated by a series of duplication events, and by positive selection occurring even after the rodent-primate split. In addition, the constraints analysis showed higher positive selection in rodents than in primates, especially distal to the six-cysteine array. Positive selection in the evolution of these defensins may relate not only to the evolving enhancement of ancestral host defense but also to functional innovations in reproduction. The multiplicity of defensins and their preferential overexpression in the urogenital tract indicate that defensins function in the protection and maintenance of fertility.

Enigmas of mammalian gamete form and function

The gametes of man and some other Eutheria have been manipulated successfully for practical reasons, but many gaps remain in our basic understanding of the way that they function. This situation stems not least from a failure to recognize the extent to which eutherian spermatozoa and eggs, and elements related to their operation, have come to differ from those of other groups. Novel features in the male that reflect this include a radical design of the sperm head with the acrosome seeming to function primarily in egg-coat binding rather than its lysis, a multifaceted post-testicular sperm maturation and an androgen/low-temperature-regulated system of sperm storage--both tied to the epididymis, a variable male accessory sex gland complex, and descent of the testis and epididymis to a scrotum. In the female, such novelties are represented in a need for sperm capacitation, in an unusual regulation of sperm transport within the oviduct, in the cumulus oophorus and character of the zona pellucida around the small egg, and in a unique configuration of gamete fusion. The collective evidence now suggests that many of these features reflect a new fertilisation strategy or its consequences, with most being causally linked. One initial 'domino' in this regard appears to be the small yolkless state of the egg and its intolerance for polyspermy, as determinants of the unusual mode of oviductal sperm transport and possibly the existence and form of the cumulus oophorus. However, a particularly influential first 'domino' appears to be the physical character of the eutherian zona pellucida. This differs from the egg coats of other animal groups by virtue of a resilient elasticity and thickness. These qualities allow this primary and often only coat to stretch and so persist during later expansion of the blastocyst, usually until close to implantation. At the same time, the dimensions, physical character, and particularly the relative protease-insensitivity of the zona appear to have had profound effects on sperm form and function and, more indirectly, on sperm-related events in the male and the female tract. Marsupials display some similarities and also some strikingly different features, against which the enigmas of the eutherian situation can be evaluated.

RNase9, an Androgen-Dependent Member of the RNase A Family, Is Specifically Expressed in the Rat Epididymis1

Members of the RNase superfamily participate in a diverse array of biological processes, including RNA degradation, antipathogen activities, angiogenesis, and digestion. In the present study, we cloned the rat RNase9 gene by in silico methods and genome walking based on homology to the Macaca mulatta (rhesus monkey) epididymal RNase9. The gene is located on chromosome 15p14, spanning two exons, and is clustered with other members of the RNase A superfamily. It contains 1279 bp and encodes 182 amino acids, including a 24-amino acid signal peptide, and it has unique features known from other RNases. Unlike those other members, the rat RNase9 mRNA was specifically expressed in the epididymis, especially in the caput and corpus, and exhibited an androgen-dependent expression pattern but was downregulated in an epididymitis animal model. The RNASE9 was expressed in a principal cell-specific pattern. Interestingly, most of the principal cells in the caput expressed the RNASE9; however, in the distal caput, the principal cells showed a checkerboard-like pattern of immunoreactivity. We also observed that the RNASE9 was bound on the acrosomal domain of sperm. Its potential roles in sperm maturation are discussed.

Identification and characterization of novel and unknown mouse epididymis-specific genes by complementary DNA microarray technology

To examine epididymal function, we attempted to identify highly expressed genes in mouse epididymis using a cDNA microarray containing PCR products amplified from a mouse epididymal cDNA library. We isolated one novel and four known genes-lymphocyte cytosolic protein 1 (Lcp1), complement subcomponents C1r/C1s, Uegf protein, and bone morphogenetic protein and zona pellucida-like domains 1 (Cuzd1), transmembrane epididymal protein 1 (Teddm1), and whey acidic protein 4-disulfide core domain 16 (Wfdc16)-with unknown functions in the epididymis. The novel gene, designated Serpina1f (serine peptidase inhibitor [SERPIN], clade A, member 1f), harbors an open reading frame of 1 233 bp encoding a putative protein of 411 amino acids, including a SERPIN domain. These five genes were predominantly expressed in the epididymis as compared to other organs. In situ hybridization analysis revealed their epididymal region-specific expression patterns. Real-time RT-PCR analysis revealed a significant increase in mRNA expression of these genes around puberty. Castration decreased their expression, except forLcp1. Testosterone (T) restored these reduced expressions, except forTeddm1; however, this restoration was not observed with 17 beta-estradiol (E2). Administration of T and E2 combination recovered the Serpina1f mRNA concentration; this recovery was also observed with T alone. However, the recovery of Cuzd1and Wfdc16mRNA concentrations was inadequate. Neonatal diethylstilbestrol treatment suppressed the Cuzd1, Wfdc16, and Serpina1f mRNA expression in the epididymis of 8-week-old mice; this was not observed with E2. These results suggest that our microarray system can provide a novel insight into the epididymal function on a molecular basis, and the five genes might play important roles in the epididymis.

Cross-species analysis of the mammalian β-defensin gene family: presence of syntenic gene clusters and preferential expression in the male reproductive tract

Mammalian β-defensins are an important family of innate host defense peptides with pleiotropic activities. As a first step to study the evolutionary relationship and biological role of the β-defensin family, we identified their complete repertoires in the human, chimpanzee, mouse, rat, and dog following systemic, genome-wide computational searches. Although most β-defensin genes are composed of two exons separated by an intron of variable length, some contain an additional one or two exons encoding an internal pro-sequence, a segment of carboxy-terminal mature sequences or untranslated regions. Alternatively, spliced isoforms have also been found with several β-defensins. Furthermore, all β-defensin genes are densely clustered in four to five syntenic chromosomal regions, with each cluster spanning <1.2 Mb across the five species. Phylogenetic analysis indicated that, although the majority of β-defensins are evolutionarily conserved across species, subgroups of gene lineages exist that are specific in certain species, implying that some β-defensins originated after divergence of these mammals from each other, while most others arose before the last common ancestor of mammals. Surprisingly, RT-PCR revealed that all but one rat β-defensin transcript are preferentially expressed in the male reproductive tract, particularly in epididymis and testis, except that Defb4, a human β-defensin-2 ortholog, is more restricted to the respiratory and upper gastrointestinal tracts. Moreover, most β-defensins expressed in the reproductive tract are developmentally regulated, with enhanced expression during sexual maturation. Existence of such a vast array of β-defensins in the male reproductive tract suggests that these genes may play a dual role in both fertility and host defense.

Identification, characterization, and evolution of a primate beta-defensin gene cluster

Defensins are members of a large diverse family of cationic antimicrobial peptides that share a signature pattern consisting of six conserved cysteine residues. Defensins have a wide variety of functions and their disruption has been implicated in various human diseases. Here we report the characterization of DEFB119-DEFB123, five genes in the human beta-defensin cluster locus on chromosome 20q11.1. The genomic structures of DEFB121 and DEFB122 were determined in silico. Sequences of the five macaque orthologs were obtained and expression patterns of the genes were analyzed in humans and macaque by semiquantitative reverse transcription polymerase chain reaction. Expression was restricted to the male reproductive tract. The genes in this cluster are differentially regulated by androgens. Evolutionary analyses suggest that this cluster originated by a series of duplication events and by positive selection. The evolutionary forces driving the proliferation and diversification of these defensins may be related to reproductive specialization and/or the host-parasite coevolutionary process.

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.

Multiple roles of antimicrobial defensins, cathelicidins, and eosinophil-derived neurotoxin in host defense

Mammals generate a diverse array of antimicrobial proteins, largely represented by defensins or cathelicidins. The direct in vitro microbicidal activity of antimicrobial proteins has long been considered an important innate immune defense, although the in vivo relevance has only very recently been established for certain defensins and cathelicidins. Mammalian defensins and cathelicidins have also been shown to have multiple receptor-mediated effects on immune cells. Beta-defensins interact with CCR6; murine beta-defensin-2 in addition activates TLR4. Cathelicidins act on FPRL1-expressing cells. Furthermore, several defensins have considerable immunoenhancing activity. Thus, it appears that mammalian antimicrobial proteins contribute to both innate and adaptive antimicrobial immunity.

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.

Secreted epididymal glycoprotein 2D6 that binds to the sperm's plasma membrane is a member of the beta-defensin superfamily of pore-forming glycopeptides

The plasma membrane of spermatozoa undergoes substantial remodeling during passage through the epididymal duct, principally because of changes in phospholipid composition, exchange of glycoproteins with epididymal fluid, and processing of existing membrane proteins. Here, we describe the interaction of an epididymal glycoprotein recognized by monoclonal antibody 2D6 with the plasma membrane of rat spermatozoa. Our goals have been to understand more about the mechanism of secretion of epididymal glycoproteins, how they interact with the sperm's plasma membrane, and their disposition within it. Reactivity to 2D6 monoclonal antibody was first detectable in principal cells in the distal caput epididymidis and as a soluble high-molecular-weight complex in the secreted fluid. It was not associated with membranous vesicles in the duct lumen. On cauda spermatozoa 2D6 monoclonal antibody recognized a 24-kDa glycoprotein (the subunit of a disulfide cross-linked homodimer of 48 kDa) that was present on the plasma membrane overlying the sperm tail. Binding of 2D6 to immature spermatozoa in vitro was cell-type specific but not species specific, and the antigen could only be extracted from cauda spermatozoa with detergents. Sequencing studies revealed that the 24-kDa glycoprotein was a member of the beta-defensin superfamily of small pore-forming glycopeptides of which several others (ESP13.2, Bin1b, E-2, EP2, HE2) are found in the epididymis. This evidence suggests that some epididymal glycoproteins are secreted into the luminal fluid in a soluble form and bind to specific regions of the sperm's surface via hydrophobic interactions. Given the antimicrobial function of beta-defensins, they have a putative role in protecting spermatozoa and the epididymis from bacterial infections.

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.

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.

Cloning and characterization of a novel sperm-associated isoantigen (E-3) with defensin- and lectin-like motifs expressed in rat epididymis

In the present study we report the identification of a novel epididymis-specific secretory glycoprotein, E-3, which is a sperm-associated isoantigen containing defensin- and lectin-like motifs. E-3 was detected in rat epididymal fluid and in sperm extracts by two-dimensional (2-D) Western blotting using rat hyperimmune sera raised against rat sperm. The immunoreactive spot of approximately 28 kDa with an isoelectric point (pI) of 3.5 was cored from silver-stained gels. Microsequencing by tandem mass spectrometry and database searches revealed several peptides to be novel sequences. Degenerate deoxyinosine-containing primers corresponding to the novel peptides were used in rapid amplification of cDNA ends and polymerase chain reaction to clone E-3 from a rat epididymal cDNA library. A 449-base pair nucleotide sequence was subsequently obtained consisting of a complete open reading frame (ORF) of 111 amino acids, which showed similarity to the defensin and lectin families. The first 21 amino acids constituted a putative signal peptide, suggesting that E-3 is a secretory protein. Mature E-3 protein corresponding to amino acids 22-111 was expressed in E. coli, and chickens were immunized with recombinant E-3 (rE-3). The resulting anti-rE-3 antisera recognized the recombinant immunogen as well as a "native" protein of 28 kDa, pI 2.5-3.5 in both epididymal fluid and in sperm extracts on 2-D Western blots. Northern hybridization indicated that E-3 mRNA was present in the epididymis but not in testis or other tissues, and that E-3 mRNA was predominantly expressed in the corpus and cauda of the epididymis, but not in the initial segment or caput. Similarly, Western blots detected the E-3 protein only in the epididymal fluid and sperm from the corpus and caudal regions. Finally, indirect immunofluorescence localized E-3 on the entire tail, and with less intensity on the head of the sperm. These observations indicate that E-3 is a secreted epididymal protein that becomes associated with the sperm as it transits through the corpus and cauda. The presence of a defensin-like motif suggests that E-3 may play a role in protecting the sperm from microbial infections in the epididymis and in the female reproductive tract.

Identification and characterization of a new member of serpin family- HongrES1 in rat epididymis

A full length cDNA named HongrES1 was isolated and cloned by screening rat epididymis cDNA library using a mouse EST as a probe and 5'RACE followed. It contained 1590bp nucleotides and its predicted protein had 415 amino acid residues including a serpin (serine protease inhibitor) conserved domain. Tissue distribution pattern showed it was specifically expressed in adult rat epididymis; moreover, in situ hybridyzation indicated this gene was expressed in a limited region of the cauda epididymis near vas deference. Such kind of expression pattern sugested that HongrES1 had potential function in male reproduction.

Cystatin 11: a new member of the cystatin type 2 family

Cystatin (CST)11, a novel member of the CST type 2 family of cysteine protease inhibitors, was identified in Macaca mulatta epididymis by subtractive hybridization cloning. The human CST11 gene on chromosome 20p11.2 is located near three other CST genes expressed predominantly in the male reproductive tract. The CST11 gene spans three exons, a structure similar to that of other CST family 2 genes. An exon 2-deleted alternative transcript (CST11Delta2) was also identified. CST11 mRNA is expressed only in the epididymis as judged by Northern blot hybridization and is androgen regulated. The protein is most abundant in the initial segment, but is detected throughout the epididymis and on ejaculated human sperm. The calculated tertiary structure of CST11 reveals that the three regions corresponding to the protease inhibitory wedge of CST3 are similarly juxtaposed in CST11, consistent with protease inhibitor function. Intact and exon 2-deleted CST11 recombinant proteins were tested for antibacterial activity. After a 2-h incubation of Escherichia coli with 50 microg/ml recombinant CST11 or CST11Delta2, bacterial colony-forming units were reduced to 30% of control, indicating that both forms have antimicrobial activity.