Cysteine-rich secretory protein 2 binds to mitogen-activated protein kinase kinase kinase 11 in mouse sperm

Mammalian cysteine-rich secretory proteins interact with plasma membrane Ca2+ exporter PMCA4b

BACKGROUND

Mammalian cysteine-rich secretory proteins (CRISPs) are predominantly expressed in the male reproductive tract. Knockout mice lacking two or more CRISPs show defects in sperm transport, sperm-egg interaction and Ca2+ homeostasis. CRISPs play redundant and specific roles via their binding partners. To understand this, a comprehensive analysis of CRISP interactome needs to be undertaken.

OBJECTIVES

This study aimed to analyse CRISP4 binding partners on the plasma membrane of rat caudal spermatozoa.

MATERIALS AND METHODS

Total proteins from rat caudal spermatozoa were subjected to immunoprecipitation using anti-CRISP4 antibody followed by liquid chromatography-mass spectrophotometry analysis. Plasma membrane localised proteins were shortlisted, and a key target was validated by co-immunoprecipitation and co-localisation. Co-transfection followed by co-immunoprecipitation was carried out for studying the interaction of full-length as well as deletion mutants of CRISPs with human plasma membrane calcium ATPase, isoform b (hPMCA4b). Calcium assays were performed using Fura-2-AM. The cholesterol binding ability of different CRISPs was evaluated in silico.

RESULTS

The membrane-specific interactome of rat CRISP4 (rCRISP4) from caudal spermatozoa revealed PMCA4b as a novel binding partner, and their interaction was validated in rat spermatozoa. Human CRISP1 (hCRISP1) and hCRISP3 also interacted with PMCA4b via the N-terminal domain. Interestingly, hCRISP1 and rCRISP4 delayed PMCA4b-mediated calcium extrusion but hCRISP3 did not. In silico analysis demonstrated that hCRISP1 and rCRISP4 have higher binding affinity towards cholesterol than hCRISP3. The secretion profile of different CRISPs also showed that the ratio of secreted to cell-associated proteins was highest for hCRISP3.

CONCLUSION

Our study identifies PMCA4b as a target of multiple mammalian CRISPs and unravels a new role of CRISPs in regulating calcium homeostasis. Differences in the interaction of different CRISPs with cholesterol may regulate their enrichment in the lipid rafts and redistribution in the membrane post-capacitation, thereby affecting their interaction with PMCA4b.

Non-transgenic, PAMAM co-delivery DNA of interactive proteins NbCRVP and NbCalB endows Nicotiana benthamiana with a stronger antiviral effect to RNA viruses

BACKGROUND

Viral diseases continue to pose a major threat to the world's commercial crops. The in-depth exploration and efficient utilization of resistance proteins have become crucial strategies for their control. However, current delivery methods for introducing foreign DNA suffer from host range limitations, low transformation efficiencies, tissue damage, or unavoidable DNA integration into the host genome. The nanocarriers provides a convenient channel for the DNA delivery and functional utilization of disease-resistant proteins.

RESULTS

In this research, we identified a cysteine-rich venom protein (NbCRVP) in Nicotiana benthamiana for the first time. Virus-induced gene silencing and transient overexpression clarified that NbCRVP could inhibit the infection of tobacco mosaic virus, potato virus Y, and cucumber mosaic virus, making it a broad-spectrum antiviral protein. Yeast two-hybrid assay, co-immunoprecipitation, and bimolecular fluorescence complementation revealed that calcium-dependent lipid-binding (CaLB domain) family protein (NbCalB) interacted with NbCRVP to assist NbCRVP playing a stronger antiviral effect. Here, we demonstrated for the first time the efficient co-delivery of DNA expressing NbCRVP and NbCalB into plants using poly(amidoamine) (PAMAM) nanocarriers, achieving stronger broad-spectrum antiviral effects.

CONCLUSIONS

Our work presents a tool for species-independent transfer of two interacting protein DNA into plant cells in a specific ratio for enhanced antiviral effect without transgenic integration, which further demonstrated new strategies for nanocarrier-mediated DNA delivery of disease-resistant proteins.

Characterization of acrosin and acrosin binding protein as novel CRISP2 interacting proteins in boar spermatozoa

BACKGROUND

Previously, we reported that cysteine-rich secretory protein 2 is involved in high molecular weight complexes in boar spermatozoa. These cysteine-rich secretory protein 2protein complexes are formed at the last phase of sperm formation in the testis and play a role in sperm shaping and functioning.

OBJECTIVES

This study aimed to identify cysteine-rich secretory protein 2 interacting partners. These binding partner interactions were investigated under different conditions, namely, non-capacitating conditions, after the induction of in vitro sperm capacitation and subsequently during an ionophore A23187-induced acrosome reaction.

MATERIALS AND METHODS

The incubated pig sperm samples were subjected to protein extraction. Extracted proteins were subjected to blue native gel electrophoresis and native immunoblots. Immunoreactive gel bands were excised and subjected to liquid chromatography-mass spectrometry (LC-MS) analysis for protein identification. Protein extracts were also subjected to CRISP2 immunoprecipitation and analyzed by LC-MS for protein identification. The most prominent cystein-rich secretory protein 2 interacting proteins that appeared in both independent LC-MS analyses were studied with a functional in situ proximity interaction assay to validate their property to interact with cystein-rich secretory protein 2 in pig sperm.

RESULTS

Blue native gel electrophoresis and native immunoblots revealed that cystein-rich secretory protein 2 was present within a ∼150 kDa protein complex under all three conditions. Interrogation of cystein-rich secretory-protein 2-immunoreactive bands from blue native gels as well as cystein-rich secretory protein 2 immunoprecipitated products using mass spectrometry consistently revealed that, beyond cystein-rich secretory protein 2, acrosin and acrosin binding protein were among the most abundant interacting proteins and did interact under all three conditions. Co-immunoprecipitation and immunoblotting indicated that cystein-rich secretory protein 2 interacted with pro-acrosin (∼53 kDa) and Aacrosin binding protein under all three conditions and additionally to acrosin (∼35 kDa) after capacitation and the acrosome reaction. The colocalization of these interacting proteins with cystein-rich secretory protein 2 was assessed via in situ proximity ligation assays. The colocalization signal of cystein-rich secretory protein 2 and acrosin in the acrosome seemed dispersed after capacitation but was consistently present in the sperm tail under all conditions. The fluorescent foci of cystein-rich secretory protein 2 and acrsin binding protein colocalization appeared to be redistributed within the sperm head from the anterior acrosome to the post-acrosomal sheath region upon capacitation.

DISCUSSION AND CONCLUSION

These results suggest that CRISP2 may act as a scaffold for protein complex formation and dissociation to ensure the correct positioning of proteins required for the acrosome reaction and zona pellucida penetration.

CRISP protein expression in semen of the endangered Malayan tapir (Tapirus indicus)

The Malayan tapir is a large endangered herbivore native to South-east Asia with fewer than 2500 animals remaining in the wild. Although a small number of animals (183 animals held by 60 institutions) are managed in zoos and breeding centres, there is limited information on the fundamental reproductive biology of this species. The purpose of this present study was to evaluate the associations of reproductive protein biomarkers (CRISP2 and CRISP3) in the seminal plasma and spermatozoa with reproductive characteristics in male Malayan tapirs. Ejaculates were collected from zoo-housed animals by electroejaculation and assessed for sperm motility and quality traits. Seminal plasma and sperm pellets were analysed for CRISP protein expression by immunoblotting. The reproductive tract of a single animal was also analysed for CRISP2 and CRISP3 protein expression and localization by immunohistochemistry. Our results showed that both CRISP2 and CRISP3 are expressed in the seminal plasma and spermatozoa derived from Malayan tapirs. CRISP expression was positively correlated with semen quality, especially ejaculate volume, number of motile sperm, and acrosomal integrity. In addition, CRISP2 and CRISP3 protein expression were slightly high in males that had recently sired an offspring. The results suggest that CRISP proteins may serve as biomarkers for ejaculate quality and fertility in male Malayan tapirs. These findings may have significant implications for planning future breeding and re-introduction efforts for this species.

Molecular perspective concerning fluoride and arsenic mediated disorders on epididymal maturation of spermatozoa: A concise review

Epididymis is a complex tubular structure of male reproductive system where spermatozoa undergo maturation and gain the fertilizing ability. Epididymal pseudostratified columnar epithelium with different cell types play imperative role by their secretory properties and enrich the luminal microenvironment necessary for achieving spermatozoal motility. During epididymal transit several secretory proteins like P26h, SPAG11, HSPD1 and many others are deposited on spermatozoal surface. At the same time spermatozoal proteins are also modified in this intraluminal milieu, which include cyritestin, fertilin, CE9 and others. Natural and anthropogenic activities disclose various environmental pollutants which affect different physiological systems of animals and human being. Likewise, reproductive system is also being affected. Fluoride causes structural alterations of caput and cauda segments of epididymis. Redox homeostasis and functional integrity are also altered due to diminished activities of SOD1, GR, Crisp2, Lrp2 and other important proteins. On the contrary arsenic affects mostly on cauda segment. Redox imbalance and functional amendment in epididymis have been observed with arsenic revelation as evidenced by altered genomic appearance of SOD, GST, catalase, Ddx3Y, VEGF and VEGFR2. This review is dealt with structure-function interplay in normal epididymal spermatozoal maturation along with subsequent complications developed under fluoride and arsenic toxicities.

Characterization and biological role of cysteine-rich venom protein belonging to CRISPs from turkey seminal plasma†

Turkey semen contains cysteine-rich secretory proteins (CRISPs) that belong to the dominant seminal plasma proteins. We aimed to isolate and characterize CRISP from turkey seminal plasma and evaluate its possible involvement in yellow semen syndrome (YSS). YSS, which is well characterized, causes reduced fertility and hatchability. The protein was purified using hydrophobic interaction, gel filtration, and reverse phase chromatography. It then was subjected to identification by mass spectrometry, analysis of physicochemical properties, and specific antibody production. The biological function of the isolated protein was tested and included its effects on sperm motility and migration and sperm-egg interactions. Sperm motility was measured with the CASA system using Hobson Sperm Tracker. The reproductive tract of turkey toms was analyzed for gene expression; immunohistochemistry was used for protein localization in the male reproductive tract, spermatozoa, and inner perivitelline layer. The isolated protein was identified as cysteine-rich venom protein-like isoform X2 (CRVP X2; XP_010706464.1) and contained feature motifs of CRISP family proteins. Turkey CRVP X2 was present in both spermatozoa and seminal plasma. The extensive secretion of CRVP X2 by the epithelial cells of the epididymis and ductus deferens suggests its involvement in post-testicular sperm maturation. The internally localized CRVP X2 in the proximal part of the sperm tail might be responsible for stimulation of sperm motility. CRVP X2 on the sperm head might be involved in several events prior to fusion and may also participate in gamete fusion itself. Although the mechanisms by which CRVP X2 mediates fertilization are still unknown, the involvement of complementary sites cannot be excluded. The disturbance of CRVP X2 expression can serve as an etiologic factor of YSS in the turkey. This study expands the understanding of the detailed mechanism of fertilization in birds by clarifying the specific role of CRVP X2.

The functions of CAP superfamily proteins in mammalian fertility and disease

BACKGROUND

Members of the cysteine-rich secretory proteins (CRISPS), antigen 5 (Ag5) and pathogenesis-related 1 (Pr-1) (CAP) superfamily of proteins are found across the bacterial, fungal, plant and animal kingdoms. Although many CAP superfamily proteins remain poorly characterized, over the past decade evidence has accumulated, which provides insights into the functional roles of these proteins in various processes, including fertilization, immune defence and subversion, pathogen virulence, venom toxicology and cancer biology.

OBJECTIVE AND RATIONALE

The aim of this article is to summarize the current state of knowledge on CAP superfamily proteins in mammalian fertility, organismal homeostasis and disease pathogenesis.

SEARCH METHODS

The scientific literature search was undertaken via PubMed database on all articles published prior to November 2019. Search terms were based on following keywords: 'CAP superfamily', 'CRISP', 'Cysteine-rich secretory proteins', 'Antigen 5', 'Pathogenesis-related 1', 'male fertility', 'CAP and CTL domain containing', 'CRISPLD1', 'CRISPLD2', 'bacterial SCP', 'ion channel regulator', 'CatSper', 'PI15', 'PI16', 'CLEC', 'PRY proteins', 'ASP proteins', 'spermatogenesis', 'epididymal maturation', 'capacitation' and 'snake CRISP'. In addition to that, reference lists of primary and review article were reviewed for additional relevant publications.

OUTCOMES

In this review, we discuss the breadth of knowledge on CAP superfamily proteins with regards to their protein structure, biological functions and emerging significance in reproduction, health and disease. We discuss the evolution of CAP superfamily proteins from their otherwise unembellished prokaryotic predecessors into the multi-domain and neofunctionalized members found in eukaryotic organisms today. At least in part because of the rapid evolution of these proteins, many inconsistencies in nomenclature exist within the literature. As such, and in part through the use of a maximum likelihood phylogenetic analysis of the vertebrate CRISP subfamily, we have attempted to clarify this confusion, thus allowing for a comparison of orthologous protein function between species. This framework also allows the prediction of functional relevance between species based on sequence and structural conservation.

WIDER IMPLICATIONS

This review generates a picture of critical roles for CAP proteins in ion channel regulation, sterol and lipid binding and protease inhibition, and as ligands involved in the induction of multiple cellular processes.

Sperm Differentiation: The Role of Trafficking of Proteins

Sperm differentiation encompasses a complex sequence of morphological changes that takes place in the seminiferous epithelium. In this process, haploid round spermatids undergo substantial structural and functional alterations, resulting in highly polarized sperm. Hallmark changes during the differentiation process include the formation of new organelles, chromatin condensation and nuclear shaping, elimination of residual cytoplasm, and assembly of the sperm flagella. To achieve these transformations, spermatids have unique mechanisms for protein trafficking that operate in a coordinated fashion. Microtubules and filaments of actin are the main tracks used to facilitate the transport mechanisms, assisted by motor and non-motor proteins, for delivery of vesicular and non-vesicular cargos to specific sites. This review integrates recent findings regarding the role of protein trafficking in sperm differentiation. Although a complete characterization of the interactome of proteins involved in these temporal and spatial processes is not yet known, we propose a model based on the current literature as a framework for future investigations.

Alterations in epididymal proteomics and antioxidant activity of mice exposed to fluoride

It is well known that high fluoride results in low fertility. Epididymis is the important place for spermatozoa maturation, which is essential for successful fertilization. In the previous studies, fluoride was reported to damage the epididymal structure of mouse and rabbit. However, the mechanism underlying sodium fluoride (NaF)-induced epididymal toxicity has not yet been well elucidated. The aim of this study is to explore the global protein alterations in epididymis of mice exposed to NaF using the iTRAQ technique. Results showed that 211 proteins were differentially expressed in both 25 and 100 mg/L NaF groups. Some of them have been proved to be important for reproduction, such as low-density lipoprotein receptor-related protein 2 (Lrp2), cytochrome c, testis-specific (Cyct), sorbitol dehydrogenase (Sord), glutathione S-transferases (GSTs), acrosin, beta-defensin 126, cysteine-rich secretory protein (Crisp) 1, and Crisp2. Gene ontology (GO) analysis suggested cellular process, organelle and catalytic activity account for high percent and number of differentially expressed proteins. 171 pathways were found after the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, among which the representative maps, such as ribosome, focal adhesion, and phagosome, were involved. Different functional categories post-translational modification, protein turnover, chaperones; translation, ribosomal structure and biogenesis; cytoskeleton; energy production and conversion are implicated in the Cluster of Orthologous Groups (COG) of proteins analysis. Subsequently, the effect of NaF on the antioxidant activity in epididymis, especially glutathione and glutathione-related enzymes, was evaluated. Results exhibited high fluoride caused low total antioxidant capacity (T-AOC), high methane dicarboxylic aldehyde (MDA), decreased reduced glutathione (GSH), and the glutathione-related enzymes [GSH peroxidase (GPx), GSH reductase (GR), and GSH S-transferase (GST)] changes in activity, protein, and mRNA expressions. In summary, NaF decreased the antioxidant activity of epididymis, especially glutathione and glutathione-related enzymes, as well as iTRAQ results, providing new explanations for the low sperm quality induced by fluoride.

Identification of CRISP2 from human sperm as PSP94-binding protein and generation of CRISP2-specific anti-peptide antibodies

Cysteine-rich secretory proteins (CRISPs) are mainly found in the mammalian male reproductive tract and reported to be involved at different stages of fertilization. CRISPs have been shown to interact with prostate secretory protein of 94 amino acids (PSP94) from diverse sources, and the binding of these evolutionarily conserved proteins across species is proposed to be of functional significance. Of the three mammalian CRISPs, PSP94-CRISP3 interaction is well characterized, and specific binding sites have been identified; whereas, CRISP2 has been shown to interact with PSP94 in vitro. Interestingly, human CRISP3 and CRISP2 proteins are closely related showing 71.4% identity. In this study, we identified CRISP2 as a potential binding protein of PSP94 from human sperm. Further, we generated antisera capable of specifically detecting CRISP2 and not CRISP3. In this direction, specific peptides corresponding to the least conserved ion channel regulatory region were synthesized, and polyclonal antibodies were generated against the peptide in rabbits. The binding characteristics of the anti-CRISP2 peptide antibody were evaluated using competitive ELISA. Immunoblotting experiments also confirmed that the peptide was able to generate antibodies capable of detecting the mature CRISP2 protein present in human sperm lysate. Furthermore, this anti-CRISP2 peptide antibody also detected the presence of native CRISP2 on sperm.Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.

Role of posttranslational protein modifications in epididymal sperm maturation and extracellular quality control

The epididymal lumen is a complex microenvironment in which spermatozoa acquire motility and fertility. Spermatozoa are synthetically inactive and therefore the maturation process requires their interaction with proteins that are synthesized and secreted in a highly regionalized manner by the epididymal epithelium. In addition to the integration of epididymal secretory proteins, posttranslational modifications of existing sperm proteins are important for sperm maturation and acquisition of fertilizing potential. Phosphorylation, glycosylation, and processing are several of the posttranslational modifications that sperm proteins undergo during epididymal transit resulting in changes in protein function and localization ultimately leading to mature spermatozoa. In addition to these well-characterized modifications, protein aggregation and cross-linking also occur within the epididymal lumen and may represent unique mechanisms for controlling protein function including that for maturation as well as for extracellular quality control.

Platyhelminth Venom Allergen-Like (VAL) proteins: revealing structural diversity, class-specific features and biological associations across the phylum

During platyhelminth infection, a cocktail of proteins is released by the parasite to aid invasion, initiate feeding, facilitate adaptation and mediate modulation of the host immune response. Included amongst these proteins is the Venom Allergen-Like (VAL) family, part of the larger sperm coating protein/Tpx-1/Ag5/PR-1/Sc7 (SCP/TAPS) superfamily. To explore the significance of this protein family during Platyhelminthes development and host interactions, we systematically summarize all published proteomic, genomic and immunological investigations of the VAL protein family to date. By conducting new genomic and transcriptomic interrogations to identify over 200 VAL proteins (228) from species in all 4 traditional taxonomic classes (Trematoda, Cestoda, Monogenea and Turbellaria), we further expand our knowledge related to platyhelminth VAL diversity across the phylum. Subsequent phylogenetic and tertiary structural analyses reveal several class-specific VAL features, which likely indicate a range of roles mediated by this protein family. Our comprehensive analysis of platyhelminth VALs represents a unifying synopsis for understanding diversity within this protein family and a firm context in which to initiate future functional characterization of these enigmatic members.

The buccal gland of Lampetra japonica is a source of diverse bioactive proteins

The parasitic phase lampreys (Lampetra japonica) are bloodsuckers in the marine, and their buccal gland secretion (lamphredin) contains various regulators such as anticoagulants, ion channel blockers, and immune suppressors like those from leeches, insects, ticks, vampire bats, and snakes. This review focuses on the functions and characteristics of the active proteins from the buccal gland of L. japonica for the first time, and provides new insights into the parasitic mechanisms of lampreys and the possibilities of developing drugs such as novel anticoagulants, thrombolytic agents, local anesthetics, and immunosuppressants.

Evolution of CRISPs associated with toxicoferan-reptilian venom and mammalian reproduction

Cysteine-rich secretory proteins (CRISPs) are glycoproteins found exclusively in vertebrates and have broad diversified functions. They are hypothesized to play important roles in mammalian reproduction and in reptilian venom, where they disrupt homeostasis of the prey through several mechanisms, including among others, blockage of cyclic nucleotide-gated and voltage-gated ion channels and inhibition of smooth muscle contraction. We evaluated the molecular evolution of CRISPs in toxicoferan reptiles at both nucleotide and protein levels relative to their nonvenomous mammalian homologs. We show that the evolution of CRISP gene in these reptiles is significantly influenced by positive selection and in snakes (ω = 3.84) more than in lizards (ω = 2.33), whereas mammalian CRISPs were under strong negative selection (CRISP1 = 0.55, CRISP2 = 0.40, and CRISP3 = 0.68). The use of ancestral sequence reconstruction, mapping of mutations on the three-dimensional structure, and detailed evaluation of selection pressures suggests that the toxicoferan CRISPs underwent accelerated evolution aided by strong positive selection and directional mutagenesis, whereas their mammalian homologs are constrained by negative selection. Gene and protein-level selection analyses identified 41 positively selected sites in snakes and 14 sites in lizards. Most of these sites are located on the molecular surface (nearly 76% in snakes and 79% in lizards), whereas the backbone of the protein retains a highly conserved structural scaffold. Nearly 46% of the positively selected sites occur in the cysteine-rich domain of the protein. This directional mutagenesis, where the hotspots of mutations are found on the molecular surface and functional domains of the protein, acts as a diversifying mechanism for the exquisite biological targeting of CRISPs in toxicoferan reptiles. Finally, our analyses suggest that the evolution of toxicoferan-CRISP venoms might have been influenced by the specific predatory mechanism employed by the organism. CRISPs in Elapidae, which mostly employ neurotoxins, have experienced less positive selection pressure (ω = 2.86) compared with the "nonvenomous" colubrids (ω = 4.10) that rely on grip and constriction to capture the prey, and the Viperidae, a lineage that mostly employs haemotoxins (ω = 4.19). Relatively lower omega estimates in Anguimorph lizards (ω = 2.33) than snakes (ω = 3.84) suggests that lizards probably depend more on pace and powerful jaws for predation than venom.

Allurin, an amphibian sperm chemoattractant having implications for mammalian sperm physiology

Eggs of many species are surrounded by extracellular coats that emit ligands to which conspecific sperm respond by undergoing chemotaxis and changes in metabolism, motility, and acrosomal status in preparation for fertilization. Here we review methods used to measure sperm chemotaxis and focus on recent studies of allurin, a 21-kDa protein belonging to the Cysteine-RIch Secretory Protein (CRISP) family that has chemoattraction activity for both amphibian and mammalian sperm. Allurin is unique in being the first extensively characterized Crisp protein found in the female reproductive tract and is the product of a newly discovered amphibian gene within a gene cluster that has been largely conserved in mammals. Study of its expression, function, and tertiary structure could lead to new insights in the role of Crisp proteins in sperm physiology.

Copy number changes of CRISP3 in oral squamous cell carcinoma

The aim of this study was to identify tumor suppressor genes (TSGs) in oral squamous cell carcinoma (OSCC) using whole-genome analysis of microarray technology and real-time quantitative polymerase chain reaction (QPCR). We applied whole-genome analysis of TSGs in the specimens from 3 patients of OSCC by microarray technology. A total of 11 genes, CRISP3, SCGB3A1, AGR2, PIP, C20orf114, TFF1, STATH, AZGP1, MUC7, DMBT1 and LOC389429, were found to be down-regulated, and 2, matrix metallopeptidase (MMP) 1 and MMP3, were found to be up-regulated in the 3 OSCC patients using microarray technology. In this study, we selected the CRISP3 gene. CRISP3 belongs to the cystein-rich secretary protein gene family in chromosome 6p12.3. CRISP3 has been found in the salivary gland, spleen and prostate gland and is a prominent biomarker in the gene expression of prostate cancer. Down-regulation of this gene was previously observed in OSCC. No studies examining the DNA copy number of CRISP3 in detail exist. We analyzed the DNA copy number of CRISP3 in 5 OSCC-derived cell lines (SAS, Ca9-22, KON, HSC2 and HSC4) and 60 OSCC tissues by real-time QPCR. The DNA copy number loss of CRISP3 was observed in 2 of the 5 OSCC-derived cell lines (SAS, HSC2) and in 24 of 60 patients (40.0%) using real-time QPCR. A significant statistical correlation between the copy number loss and gender and T classification was observed. These results indicate that the inactivation of CRISP3 is an early event in OSCC, since the T1/T2 classification is correlated with DNA copy number loss of CRISP3, whereas T3/T4 classification is not. We conclude that CRISP3 may be involved in the carcinogenesis of OSCC.

The role of cysteine-rich secretory proteins in male fertility

The cysteine-rich secretory proteins (CRISPs) are a subgroup of the CRISP, antigen 5 and Pr-1 (CAP) protein superfamily, and are found only in vertebrates. They show a strong expression bias to the mammalian male reproductive tract and the venom of poisonous reptiles. Within the male reproductive tract CRISPs have been implicated in many aspects of male germ cell biology spanning haploid germ cell development, epididymal maturation, capacitation, motility and the actual processes of fertilization. At a structural level, CRISPs are composed of two domains, a CAP domain, which has been implicated in cell-cell adhesion, and a CRISP domain, which has been shown to regulate several classes of ion channels across multiple species. Herein, we will review the current literature on the role of CRISPs in male fertility, and by inference to related non-mammalian protein, infer potential biochemical functions.

Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 5: intercellular junctions and contacts between germs cells and Sertoli cells and their regulatory interactions, testicular cholesterol, and genes/proteins associated with more than one germ cell generation

In the testis, cell adhesion and junctional molecules permit specific interactions and intracellular communication between germ and Sertoli cells and apposed Sertoli cells. Among the many adhesion family of proteins, NCAM, nectin and nectin-like, catenins, and cadherens will be discussed, along with gap junctions between germ and Sertoli cells and the many members of the connexin family. The blood-testis barrier separates the haploid spermatids from blood borne elements. In the barrier, the intercellular junctions consist of many proteins such as occludin, tricellulin, and claudins. Changes in the expression of cell adhesion molecules are also an essential part of the mechanism that allows germ cells to move from the basal compartment of the seminiferous tubule to the adluminal compartment thus crossing the blood-testis barrier and well-defined proteins have been shown to assist in this process. Several structural components show interactions between germ cells to Sertoli cells such as the ectoplasmic specialization which are more closely related to Sertoli cells and tubulobulbar complexes that are processes of elongating spermatids embedded into Sertoli cells. Germ cells also modify several Sertoli functions and this also appears to be the case for residual bodies. Cholesterol plays a significant role during spermatogenesis and is essential for germ cell development. Lastly, we list genes/proteins that are expressed not only in any one specific generation of germ cells but across more than one generation.

Glioma pathogenesis-related 1-like 1 is testis enriched, dynamically modified, and redistributed during male germ cell maturation and has a potential role in sperm-oocyte binding

The glioma pathogenesis-related 1 (GLIPR1) family consists of three genes [GLIPR1, GLIPR1-like 1 (GLIPR1L1), and GLIPR1-like 2 (GLIPR1L2)] and forms a distinct subgroup within the cysteine-rich secretory protein (CRISP), antigen 5, and pathogenesis-related 1 (CAP) superfamily. CAP superfamily proteins are found in phyla ranging from plants to humans and, based largely on expression and limited functional studies, are hypothesized to have roles in carcinogenesis, immunity, cell adhesion, and male fertility. Specifically data from a number of systems suggests that sequences within the C-terminal CAP domain of CAP proteins have the ability to promote cell-cell adhesion. Herein we cloned mouse Glipr1l1 and have shown it has a testis-enriched expression profile. GLIPR1L1 is posttranslationally modified by N-linked glycosylation during spermatogenesis and ultimately becomes localized to the connecting piece of elongated spermatids and sperm. After sperm capacitation, however, GLIPR1L1 is also localized to the anterior regions of the sperm head. Zona pellucida binding assays indicate that GLIPR1L1 has a role in the binding of sperm to the zona pellucida surrounding the oocyte. These data suggest that, along with other members of the CAP superfamily and several other proteins, GLIPR1L1 is involved in the binding of sperm to the oocyte complex. Collectively these data further strengthen the role of CAP domain-containing proteins in cellular adhesion and propose a mechanism whereby CAP proteins show overlapping functional significance during fertilization.

Human CRISP-3 binds serum alpha(1)B-glycoprotein across species

BACKGROUND

CRISP-3 was previously shown to be bound to alpha(1)B-glycoprotein (A1BG) in human serum/plasma. All mammalian sera are supposed to contain A1BG, although its presence in rodent sera is not well-documented. Since animal sera are often used to supplement buffers in experiments, in particular such that involve cell cultures, binding proteins present in sera might interfere in the experiments.

METHODS

We examined sera from five different animal species for CRISP-3 binding proteins using gel filtration and ligand blotting. We developed a rapid method for isolation of proteins that bind to human CRISP-3 and identified the isolated proteins by mass spectrometry and N-terminal sequencing.

RESULTS

We identified A1BG as a CRISP-3 binding protein in sera from cow, horse and rabbit. CRISP-3 bound kininogen 1 in mouse serum, whereas rat serum showed no CRISP-3 binding activity. In equine serum, we furthermore detected a possible CRISP, already bound to A1BG.

GENERAL SIGNIFICANCE

It seems to be a common mechanism that A1BGs bind CRISPs, also across species. Apart from the possible physiological implications hereof, complex binding of CRISPs by A1BG (and other proteins) may interfere with the detection and function of CRISPs, when these are studied in the presence of animal sera.

A novel protein, sperm head and tail associated protein (SHTAP), interacts with cysteine-rich secretory protein 2 (CRISP2) during spermatogenesis in the mouse

BACKGROUND INFORMATION

CRISP2 (cysteine-rich secretory protein 2) is a sperm acrosome and tail protein with the ability to regulate Ca2+ flow through ryanodine receptors. Based on these properties, CRISP2 has a potential role in fertilization through the regulation of ion signalling in the acrosome reaction and sperm motility. The purpose of the present study was to determine the expression, subcellular localization and the role in spermatogenesis of a novel CRISP2-binding partner, which we have designated SHTAP (sperm head and tail associated protein).

RESULTS

Using yeast two-hybrid screens of an adult testis expression library, we identified SHTAP as a novel mouse CRISP2-binding partner. Sequence analysis of all Shtap cDNA clones revealed that the mouse Shtap gene is embedded within a gene encoding the unrelated protein NSUN4 (NOL1/NOP2/Sun domain family member 4). Five orthologues of the Shtap gene have been annotated in public databases. SHTAP and its orthologues showed no significant sequence similarity to any known protein or functional motifs, including NSUN4. Using an SHTAP antiserum, multiple SHTAP isoforms (approximately 20-87 kDa) were detected in the testis, sperm, and various somatic tissues. Interestingly, only the approximately 26 kDa isoform of SHTAP was able to interact with CRISP2. Furthermore, yeast two-hybrid assays showed that both the CAP (CRISP/antigen 5/pathogenesis related-1) and CRISP domains of CRISP2 were required for maximal binding to SHTAP. SHTAP protein was localized to the peri-acrosomal region of round spermatids, and the head and tail of the elongated spermatids and sperm tail where it co-localized with CRISP2. During sperm capacitation, SHTAP and the SHTAP-CRISP2 complex appeared to be redistributed within the head.

CONCLUSIONS

The present study is the first report of the identification, annotation and expression analysis of the mouse Shtap gene. The redistribution observed during sperm capacitation raises the possibility that SHTAP and the SHTAP-CRISP2 complex play a role in the attainment of sperm functional competence.

Cysteine-rich secretory proteins are not exclusively expressed in the male reproductive tract

The Cysteine-RIch Secretory Proteins (CRISPs) are abundantly produced in the male reproductive tract of mammals and within the venom of reptiles and have been shown to regulate ion channel activity. CRISPs, along with the Antigen-5 proteins and the Pathogenesis related-1 (Pr-1) proteins, form the CAP superfamily of proteins. Analyses of EST expression databases are increasingly suggesting that mammalian CRISPs are expressed more widely than in the reproductive tract. We, therefore, conducted a reverse transcription PCR expression profile and immunohistochemical analyses of 16 mouse tissues to define the sites of production of each of the four murine CRISPs. These data showed that each of the CRISPs have distinct and sometimes overlapping expression profiles, typically associated with the male and female reproductive tract, the secretory epithelia of exocrine glands, and immune tissues including the spleen and thymus. These investigations raise the potential for a role for CRISPs in general mammalian physiology.

The CAP superfamily: cysteine-rich secretory proteins, antigen 5, and pathogenesis-related 1 proteins--roles in reproduction, cancer, and immune defense

The cysteine-rich secretory proteins, antigen 5, and pathogenesis-related 1 proteins (CAP) superfamily members are found in a remarkable range of organisms spanning each of the animal kingdoms. Within humans and mice, there are 31 and 33 individual family members, respectively, and although many are poorly characterized, the majority show a notable expression bias to the reproductive tract and immune tissues or are deregulated in cancers. CAP superfamily proteins are most often secreted and have an extracellular endocrine or paracrine function and are involved in processes including the regulation of extracellular matrix and branching morphogenesis, potentially as either proteases or protease inhibitors; in ion channel regulation in fertility; as tumor suppressor or prooncogenic genes in tissues including the prostate; and in cell-cell adhesion during fertilization. This review describes mammalian CAP superfamily gene expression profiles, phylogenetic relationships, protein structural properties, and biological functions, and it draws into focus their potential role in health and disease. The nine subfamilies of the mammalian CAP superfamily include: the human glioma pathogenesis-related 1 (GLIPR1), Golgi associated pathogenesis related-1 (GAPR1) proteins, peptidase inhibitor 15 (PI15), peptidase inhibitor 16 (PI16), cysteine-rich secretory proteins (CRISPs), CRISP LCCL domain containing 1 (CRISPLD1), CRISP LCCL domain containing 2 (CRISPLD2), mannose receptor like and the R3H domain containing like proteins. We conclude that overall protein structural conservation within the CAP superfamily results in fundamentally similar functions for the CAP domain in all members, yet the diversity outside of this core region dramatically alters target specificity and, therefore, the biological consequences.

Characterization of gametogenetin 1 (GGN1) and its potential role in male fertility through the interaction with the ion channel regulator, cysteine-rich secretory protein 2 (CRISP2) in the sperm tail

Cysteine-rich secretory protein 2 (CRISP2) is a testis-enriched protein localized to the sperm acrosome and tail. CRISP2 has been proposed to play a critical role in spermatogenesis and male fertility, although the precise function(s) of CRISP2 remains to be determined. Recent data have shown that the CRISP domain of the mouse CRISP2 has the ability to regulate Ca2+flow through ryanodine receptors (RyR) and to bind to MAP kinase kinase kinase 11 (MAP3K11). To further define the biochemical pathways within which CRISP2 is involved, we screened an adult mouse testis cDNA library using a yeast two-hybrid assay to identify CRISP2 interacting partners. One of the most frequently identified CRISP2-binding proteins was gametogenetin 1 (GGN1). Interactions occur between the ion channel regulatory region within the CRISP2 CRISP domain and the carboxyl-most 158 amino acids of GGN1. CRISP2 does not bind to the GGN2 or GGN3 isoforms. Furthermore, we showed thatGgn1is a testis-enriched mRNA and the protein first appeared in late pachytene spermatocytes and was up-regulated in round spermatids before being incorporated into the principal piece of the sperm tail where it co-localized with CRISP2. These data along with data on RyR and MAP3K11 binding define the CRISP2 CRISP domain as a protein interaction motif and suggest a role for the GGN1–CRISP2 complex in sperm tail development and/or motility.

Sox8 is a critical regulator of adult Sertoli cell function and male fertility

Sox8 encodes a high-mobility group transcription factor that is widely expressed during development. Sox8, -9 and -10 form group E of the Sox gene family which has been implicated in several human developmental disorders. In contrast to other SoxE genes, the role of Sox8 is unclear and Sox8 mouse mutants reportedly showed only idiopathic weight loss and reduced bone density. The careful analysis of our Sox8 null mice, however, revealed a progressive male infertility phenotype. Sox8 null males only sporadically produced litters of reduced size at young ages. We have shown that SOX8 protein is a product of adult Sertoli cells and its elimination results in an age-dependent deregulation of spermatogenesis, characterized by sloughing of spermatocytes and round spermatids, spermiation failure and a progressive disorganization of the spermatogenic cycle, which resulted in the inappropriate placement and juxtaposition of germ cell types within the epithelium. Those sperm that did enter the epididymides displayed abnormal motility. These data show that SOX8 is a critical regulator of adult Sertoli cell function and is required for both its cytoarchitectural and paracrine interactions with germ cells.