Occurrence of specific glycoprotein factor(s) in goat epididymal plasma that prevent adhesion of spermatozoa to glass

Purification and partial characterization of a sperm motility-inhibitory protein of ram cauda epididymal plasma

Mammalian sperm remain quiescent but fertile for several weeks in cauda epididymis. Although several sperm quiescent factors of epididymal plasma have been identified in goat, pig and cattle; however, little is known in sheep. In the present study, purification and characterization of a novel sperm quiescent protein of ovine cauda epididymal plasma (CEP) was carried out. The sperm quiescent protein was partially purified by hydroxyapatite gel adsorption chromatography followed by DEAE-sepharose® anion exchange chromatography. In the latter, the sperm quiescent activity was eluted both in 0.05 and 0.2 M potassium phosphate buffer (pH 7.5) fractions having a predominant protein of about 80 and 70 kDa with 87% and 63% homogeneity, respectively. The proteins were designated as motility-inhibitory factor of sheep I and II (MIFS-I and II), respectively. Significant (about 60%) inhibition of sperm motility was observed following treatment of cauda epididymal sperm with 6 and 12 µg/mL of partially purified MIFS-I and II, respectively. Specific activities of the partially purified MIFS-I and II were 563 and 261 U/mg of protein, while the fold-purification of the activity were 5119 and 2373, respectively. Both the proteins were heat-labile and the activity was completely lost following incubation at 100°C for 5 min. Further, the partially purified MIFS-I (5 µg/mL) caused significant reduction in in vitro sperm capacitation and slight decline in tyrosine phosphorylated p72 and p52 proteins; however the protein was nontoxic to sperm. Mass spectrometric analysis of MIFS-I revealed significant identity with human semaphorin 3D. Both dot blot and western blot analysis demonstrated cross-reactivity of MIFS-I with polyclonal anti-human SEMA3D antibody. It was concluded that the MIFS-I of ovine CEP was putative ovine semaphorin 3D protein having potent sperm quiescent and decapacitating activities and it possibly acts through inhibition of protein tyrosine phosphorylation.

Production of bioactive recombinant ovine cysteine-rich secretory protein 1 in Escherichia coli

Ovine cysteine-rich secretory protein 1 (CRISP-1) is an acidic glycoprotein of epididymal origin under CRISP, antigen 5, pathogenesis-related protein 1 (CAP) super-family. The aim of the present study was the optimization of bacterial production and partial characterization of putative mature ovine CRISP-1 protein. The cDNA corresponding to T^{23 -} C²⁴² peptide fragment of ovine CRISP-1 protein was cloned into THE pET32b(+) expression vector using E. coli DH5α. Protein expression was carried out in E. coli BL21(DE3) by inducition with 1 mM IPTG at 37°C for 4 h. The recombinant protein was expressed as inclusion bodies and purified by Ni-NTA affinity chromatography using a pH gradient. Further purification of the protein was carried out by gel extraction following zinc sulfate negative staining. SDS-PAGE analysis of the purified recombinant CRISP-1 protein revealed a 43.8 kDa band. Bioactivity of the purified CRISP-1 protein was examined on sperm motility and capacitation. The recombinant ovine CRISP-1 protein at 5 µg/ml caused significant inhibition of sperm motility, and the activity was lost following heating the protein at 100°C for 5 min. The protein also demonstrated decapacitation activity, and at a concentration of 2 µg/ml, it caused a significant (P < 0.05) reduction in sperm capacitation. In conclusion, the thioredoxin-tagged ovine CRISP-1 protein was successfully produced in E. coli and purified in the soluble form by a combination of Ni-NTA affinity chromatography, gel purification, and dialysis. The recombinant protein exhibited both motility-inhibiting and decapacitating activities. Further study is needed to elucidate the mechanism of action and evaluate it's possible use in semen preservation.Abbreviations: CRISP-1: Cysteine-rich secretory protein-1; PCR: polymerase chain reaction; IPTG: isopropyl-β-D-thiogalactopyranoside; LB: Luria Bertani; SDS-PAGE: sodium dodecyl sulfate polyacrylamide gel electrophoresis; EDTA: ethylene diamine tetraacetic acid; Ni-NTA: Nickel nitrilotriacetic acid.

Epididymal protein ASF is a D-galactose-specific lectin with apoptotic effect on human breast cancer cell line MCF7

Isolated caprine epididymal plasma glycoprotein "anti sticking factor" (ASF) interacts with caudal sperm surface in a D-galactose dependent manner. ASF acts as a Ca(2+) dependent soluble lectin principally activated in acidic pH. As a D-galactose specific lectin, it has a specific affinity for fibronectin as well as fibronectin receptor, i.e. integrins α5β3 and α5β1. By virtue of this particular property, it hampers the in vitro adhesion of the adherent breast cancer cell MCF7 with fibronectin. The effective anti-adhesive concentration of ASF promotes p53 dependent apoptosis in MCF7, which was established by Hoechst 33342 staining, DNA fragmentation assay, FITC tagged Annexin-V flowcytometry and western blot analysis. We suggest that ASF inhibits fibronectin-integrin interactions by binding with them and induces adhesion dependent apoptosis on adherent MCF7.

In vitro initiated sperm forward motility in caput spermatozoa: weak and transient

Testicular spermatozoa during journey through epididymis acquire forward motility, which is essential for fertility. To understand the biochemistry of sperm motility initiation, various initiation media have been developed that permitted high level of motility induction (55-60%) in the immature caput-spermatozoa in presence of activating principles: theophylline, bicarbonate and epididymal plasma (EP) when analysed microscopically. Here, we show for the first time using caprine model that stability and quality of in vitro-induced motility in the caput spermatozoa is insignificant in contrast to naturally induced motility in mature cauda spermatozoa. In vitro-induced motility of the immature spermatozoa was lost completely upon the removal of these activators by centrifugation. Selective withdrawal of either EP or HCO(3) by dilution retains 50-60% of the in vitro-induced motility. Spectrophotometric analysis revealed that in vitro-induced vertical motility in immature spermatozoa is too little when compared to mature spermatozoa. In in vitro-initiated caput spermatozoa, cyclic adenosine monophosphate level becomes doubled but lesser than cauda spermatozoa. This revelation concludes that scientific knowledge generated over the years on the basis of in vitro initiation method is insignificant and needs improvisation to delineate biochemical regulation of sperm motility which in turn has remarkable potential in wide biological fields, especially in infertility treatment.

Purification and characterization of a sperm motility inhibiting factor from caprine epididymal plasma

Several studies have been reported on the occurrence of sperm motility inhibiting factors in the male reproductive fluids of different mammalian species, but these proteins have not been adequately purified and characterized. A novel sperm motility inhibiting factor (MIF-II) has been purified from caprine epididymal plasma (EP) by Hydroxylapatite gel adsorption chromatography, DEAE-Cellulose ion-exchange chromatography and chromatofocusing. The MIF-II has been purified to apparent homogeneity and the molecular weight estimated by Sephacryl S-300 gel filtration is 160 kDa. MIF-II is a dimeric protein, made up of two subunits each having a molecular mass of 80 kDa as shown by SDS-PAGE. The isoelectric point of MIF-II is 5.1 as determined by chromatofocusing and isoelectric focusing. It is a heat labile protein and maximal active at the pH 6.9 to 7.5. The sperm motility inhibiting protein factor at 2 µg/ml (12.5 nM) level showed maximal motility-inhibiting activity. The observation that the epididymal plasma factor lowered the intracellular cAMP level of spermatozoa in a concentration-dependent manner suggests that it may block the motility of caprine cauda spermatozoa by interfering the cAMP dependent motility function. The results revealed that the purified protein factor has the potential of sperm motility inhibition and may serve as a vaginal contraceptive. The antibody raised against the MIF-II has the potential for enhancement of forward motility of cauda-spermatozoa. This antibody may thus be useful for solving some of the problems of male infertility due to low sperm motility.

Purification and characterization of a motility initiating protein from caprine epididymal plasma

Numerous reports have appeared on the occurrence of undefined protein factors in male reproductive fluids that promote motility of mature sperm and initiate forward motility in the immature (immotile) caput-epididymal sperm. This study reports for the first time purification to apparent homogeneity of a motility initiating protein (MIP) from epididymal plasma and its characterization using the caprine sperm model. It is a 125 kDa (approximately) dimeric protein made up of two subunits: 70 and 54 kDa. MIP is an acidic protein with an isoelectric point of 4.75. The motility protein at 30 microg/ml (240 nM) level showed nearly maximal motility-promoting activity. MIP is heat stable and it is maximally active at pH 8. It is a glycoprotein that binds with high affinity to concanavalin A and it contains mannose, galactose, and N-acetyl glucosamine approximately in the ratios of 6:1:6. It is sensitive to the actions of alpha-mannosidase and beta-N-acetylglucoseaminidase thereby demonstrating that the sugar side chain of the glycoprotein is essential for its biological activity. Epididymal plasma is its richest source. It is also capable of enhancing forward motility of mature cauda-sperm. Its antibody markedly inhibits sperm motility. MIP antibody is highly immunospecific and it recognizes both the subunits. MIP causes significant increase of the intrasperm level of cyclic AMP. MIP: the physiological motility-activating protein has potential for use as a contraceptive vaccine and for solving some of the problems of human infertility and animal breeding.

Cell surface phosphorylation by a novel ecto-protein kinase: a key regulator of cellular functions in spermatozoa

Since 1976 many studies have been reported on the occurrence and functional significance of ecto-protein kinases in a variety of cell types although their precise biochemical identity is largely unknown. This study reports for the first time purification to apparent homogeneity of an ecto-protein kinase (ecto-CIK) and some of its characteristics using caprine sperm as the cell model. The ecto-CIK is a unique membrane-specific serine/threonine protein kinase. It is a strongly basic 115 kDa protein made up of two subunits: 63 and 55 kDa. The ecto-kinase undergoes a remarkable lateral movement on the outer cell surface culminating in capping on the sperm acrosomal tip. MPS, its major protein substrate is also located on the acrosomal tip. Both ecto CIK and MPS serve as potential regulators of flagellar motility. This novel enzyme appears to be major kinase responsible for the reported regulation of mammalian cellular functions by modulating phosphorylation of the membrane-bound proteins.

Identification and characterization of a sperm motility promoting glycoprotein from buffalo blood serum

Early investigators reported the occurrence of unidentified protein factors in biological fluids that may regulate sperm motility essential for fertility potential. This study reports for the first time purification of a forward motility stimulating protein (FMSF-I), to apparent homogeneity, from a biological fluid (buffalo blood serum) and its characterization. FMSF-I is the major motility protein of buffalo serum: a rich source of the factor. FMSF showed high protein specificity and affinity for activating forward motility of goat cauda epididymal spermatozoa. The motility promoter at 0.5 microM level showed maximal activity when nearly 60%-70% of spermatozoa expressed forward motility. It is a 66 kDa monomeric acidic protein rich in aspartate, glutamate, and leucine with isoelectric point of 3.7. FMSF: a Mg2+ -dependent protein binds to concanavalin A-agarose and the glycoprotein nature of FMSF has been confirmed by PAS staining. The factor lost activity completely when treated with alpha-mannosidase showing that the sugar part of the protein is essential for its biological activity. FMSF has no species specificity for its motility-activating potential. Sperm surface has specific receptors of FMSF, which is strongly immunogenic. The factor is present in testis and epididymis although liver is its richest source. Motility promoting efficacy of FMSF is markedly higher than the well-known non-protein motility activators: theophylline and bicarbonate or their combination. FMSF is a physiological activator of sperm motility and as a slaughterhouse byproduct it has potentiality for solving some of the problems of animal breeding, conservation of endangered species, and human infertility: a global social problem.

A potent sperm motility-inhibiting activity of bioflavonoids from an ethnomedicine of Onge, Alstonia macrophylla Wall ex A. DC, leaf extract

The methanol extract (ME) and the n-butanol fractions of methanolic extract of Alstonia macrophylla Wall ex A. DC leaves were investigated on the forward motility (FM) of mammalian (goat and human) spermatozoa. The ME at 600 microg mL-1 as well as fraction B at 100 microg mL-1 concentrations showed marked inhibition of sperm FM in both goat and human species when tested by microscopic and spectrophotometric methods. Approximately 60-80% of the goat spermatozoa lost their FM when treated with 600 microg mL-1 of ME and 100 microg mL-1 of fraction B. At 100 microg mL-1 concentration, fraction B showed 90% loss of FM in human spermatozoa, while fraction B at 400 microg mL-1 concentration showed complete inhibition of sperm FM at 0 min. The inhibitory activity of fraction B increases with increasing concentration in a dose-dependent manner. Phytochemical study of the extract revealed that the leaf contains tannins, flavonoids, sterols, triterpenes, alkaloids and reducing sugars. Further fractionation and purification of the bioactive n-butanol part of ME showed the presence of ursolic acid (fraction B), beta-sitosterol (fraction A), beta-sitosterol glucoside and a mixture of minor compounds (fraction C, detected on thin-layer chromatography). The results reveal that fraction B (ursolic acid), a pentacyclic triterpene, has the potential of sperm motility inhibition and can serve as a topical vaginal contraceptive.

Identification of goat sperm ecto-cyclic AMP independent protein kinase substrate localized on sperm outer surface

We have demonstrated the location of a cyclic AMP independent serine/threonine protein kinase (ecto-CIK) on the outer surface of mature goat spermatozoa. We purified and characterized the major physiological protein substrate (MPS) of ecto-CIK. 32P-labeled membrane proteins phosphorylated by endogenous ecto-CIK of intact cauda-epididymal spermatozoa was solubilized with 1% Triton X-100 and then fractionated by following several chromatographic techniques like Sephacryl S-300 molecular sieve chromatography, DEAE-cellulose ion-exchange chromatography and chromatofocussing. The MPS of ecto-CIK has been purified to apparent homogeneity and it was found to be a monomeric protein of 100 kDa. Three isoforms of MPS have been found with pI of 6.37, 6.05, and 5.14 and all these isoforms served as the specific substrate of ecto-CIK. The ecto-kinase has nearly 30 times greater affinity for MPS as compared to casein the most potent exogenous protein substrate. Addition of MPS (pI 5.14) antibody caused head-to-head sperm agglutination. The Fv/Fab fragment of anti-MPS caused significant inhibition of sperm motility. The data show that MPS is an ecto-protein localized on the sperm head. MPS may thus play an important role for the regulation of sperm-egg interaction.

In-vitro initiation of forward motility in testicular spermatozoa

Initiation of forward motility in vitro was investigated in goat and ram spermatozoa obtained from the rete testis. No forward motility was generated in the immotile testicular spermatozoa when they were incubated in a modified Ringer's solution containing theophylline (30 mM) and epididymal plasma (2 mg protein/ml). However, these reagents induced non-progressive flagellar movement in approximately 25% of spermatozoa. Bicarbonate (25 mM) induced forward motility in approximately 16% of the goat/ram testicular spermatozoa. Theophylline was essential for the bicarbonate-mediated activation of sperm motility, but epididymal plasma had no significant effect on this activation process. Theophylline activated progressive motility in testicular spermatozoa in a dose-dependent manner, the maximum effect occurring after incubation for 10 min with 30 mM theophylline. The initiation profile of in-vitro motility of goat/ram spermatozoa from the caput epididymis closely resembled that of testicular spermatozoa except that induction of motility in the caput spermatozoa was dependent both on bicarbonate and epididymal plasma. The data indicate that, unlike caput epididymal spermatozoa, initiation of motility in testicular spermatozoa is not dependent on motility-promoting protein(s) in epididymal plasma.

Cyclic AMP phosphodiesterase: a regulator of forward motility initiation during epididymal sperm maturation

The concentrations of cAMP, cAMP phosphodiesterase (PDE) activity, and the effect of theophylline in vitro on the forward motility (FM) of maturing goat epididymal sperm have been analyzed. cAMP levels increase slowly during transit of the cells from the caput to the proximal cauda, although they acquired a minimal degree of forward progression. The last phase of sperm transit (proximal to distal cauda) was associated with a concomitant sharp rise in the level of both cAMP as well as flagellar motility. PDE activity progressively decreased (approximately threefold) during epididymal maturation, being minimal in mature cauda sperm. Theophylline (30 mM), a specific inhibitor of PDE, markedly activated (10-fold or greater) motility of the sperm derived from proximal-corpus, mid-corpus, distal-corpus, and proximal-cauda epididymides. FM of the native mature caudal sperm was similar to that of the theophylline-treated proximal-cauda sperm. The terminal stage of sperm maturity (proximal to distal cauda) was associated with a markedly reduced level of theophylline-dependent motility activation (approximately 50%). The data are consistent with the view that PDE plays an important role in the initiation of motility during epididymal sperm maturation.

Characterization of anti-sticking factor-II from goat epididymal plasma

A previous study has characterized the major 47 kDa anti-sticking factor (ASF-I) from goat cauda-epididymal plasma (Roy, N., and Majumder, G.C., Biochim. Biophys. Acta, 991:114-122, 1989). This study reports the purification and characterization of ASF-II, another anti-sticking factor from the goat epididymal plasma. ASF-II was purified to apparent homogeneity by using concanavalin A-agarose affinity chromatography, DEAE-cellulose chromatography, alumina gel adsorption, and isoelectric focussing techniques. It showed a single protein band by both non-denaturing and SDS-polyacrylamide gel electrophoresis. ASF-II showed a molecular weight of 36,000 and a sedimentation constant of 2.4S. ASF-II is largely stable to heat treatment and it is a specific glycoprotein having high affinity and specificity for its anti-sticking action. At saturating concentration (1 nM) it inhibited adhesion of nearly 50% of spermatozoa to the glass surface of the haemocytometer counting chamber. Both the protein and sugar parts of the factor are essential for the anti-sticking activity since it lost its activity completely when treated with trypsin, L-fucosidase, or mannosidase. ASF-II does not coat the glass surface and it binds to spermatozoa. Data are consistent with the view that ASF-II has not been derived from the larger ASF-I molecule due to its enzymic modifications. Both ASF-I and -II had no effect on sperm forward motility as evidenced by spectrophotometric motility assays, indicating thereby the suitability of the factors to improve the existing sperm motility assays by eliminating the possibility of cell-sticking artifacts.

Antisticking protein factors in buffalo blood serum

Buffalo blood serum is a potent source of antisticking factor (ASF) that inhibits with high affinity adhesion of goat epididymal spermatozoa to the glass surface of hemocytometer counting chamber. The serum is also capable of inhibiting glass-sticking of spermatozoa of the buffalo, ram, and bull. The serum ASF activity is nondialyzable and stable to heat treatment at 100 degrees C for two minutes. The activity of the serum ASF was lost completely when treated with trypsin (50 micrograms/ml) at 37 degrees C for thirty minutes indicating the polypeptide nature of the ASF. Serum ASF activity consists of at least two factors (A and B) as shown by concanavalin A-agarose affinity chromatography. ASF-A and -B represent nearly 75% and 25% of the total serum ASF activity. ASF-B is a glycoprotein as it binds with high affinity to concanavalin A. The sera of species such as man, goat, and rat possess ASF activity.

Purification and characterization of an anti-sticking factor from goat epididymal plasma that inhibits sperm--glass and sperm--sperm adhesions

An anti-sticking factor (ASF-I) that showed high affinity for inhibiting adhesion of spermatozoa to glass was isolated from goat epididymal plasma and characterized. The factor was purified approx. 5600-fold and showed a single protein band when examined by non-denaturation and SDS-polyacrylamide gel electrophoresis. The molecular mass and S20w value of ASF-I were approx. 47 kDa and 4.25 S. ASF-I at a concentration of 1 nM showed nearly maximal anti-sticking activity when approx. 60% of the intact spermatozoa were prevented from adhesion to glass and it showed a high degree of protein specificity. Studies with trypsin and glycosidases demonstrated that both the sugar and protein parts of the molecule are essential for its anti-sticking activity. Evidence has been presented to support the view that the outer surface of sperm possesses specific ASF-I receptors that bind to 125I-labelled ASF and mediate cell adhesion to glass. ASF-I also showed high affinity for inhibiting agglutination of corpus-epididymal spermatozoa. The ASF activity was found to be distributed in all the tissues tested and its specific activity was markedly higher in blood plasma than in the tissues. The results suggest that ASF may play an important biological role by serving as a specific inhibitor of cell-substratum and cell-cell adhesions.