Identification of membrane antigens of goat epididymal spermatozoa

Deglycosylation effect of the mammalian sperm maturation antigen (SMA2) on serological reaction and acrosome reaction

Spermatozoal membrane proteins are considered to possess several immunological unique characteristics as the cell is formed behind the blood-testes barriers. Major goat sperm maturation antigen (SMA2) contains one hexosamine along with mannose, galactose and glucose. In the present study, effects of deglycosylation of SMA2 antigen on immuno-reactivity and the serological activity was investigated. SMA2 glycoantigen showed positive immunoreactivity after treatment with sodium borohydride (NaBH(4)) and moreover this generated a 44 kDa protein band which was negative for periodic acid Schiff reagent. Trifluoromethanesulfonic acid (TFMS) caused aggregation and restricted the free mobility of the treated antigen on SDS-PAGE and the protein band generated by TFMS treatment also showed positive immuno-reactivity. The results supported the views that the protein portion retains its immuno-reactivity even after oxidation of the vicinal hydroxyl group of saccharide component of SMA2 antigen. These data suggest that immunodominent epitopes exist on the core protein by which the SMA2 antigen retains its immuno-reactivity even after disruption of the saccharide portion. Additional experiments demonstrate that protein epitopes have a role in capacitation and the acrosome reaction (AR) in presence of antibody which is raised against this protein part of SMA2 using the negative staining of FITC-PSA (fluorescein isothiocyanate-labeled Pisum sativum agglutinin) probe. Altogether these findings indicate that the protein portion of SMA2 might fulfill the serological activity of the antigen as well as the protein epitope affects the acrosome reaction. In view of this property, we propose that the protein portion of SMA2 antigen might be considered as a potential antigenic target for an immune response.

Development of a simple sperm cryopreservation model using a chemically defined medium and goat cauda epididymal spermatozoa

This investigation was carried out to develop a simple sperm cryopreservation model using a chemically defined synthetic medium (modified Ringer's solution) and mature goat cauda epididymal sperm as the model system. Rates of cooling, freezing, and maximum freezing temperature were manipulated with the help of a computer-controlled programmable biofreezer. Highly motile goat cauda sperm dispersed in a modified Ringer's solution was subjected to the freezing protocol: cooling 0.25 degrees C min(-1) to 5 degrees C, 5 degrees C min (-1) to -20 degrees C, 20 degrees C min(-1) to -100 degrees C, prior to plunging into liquid nitrogen. In the absence of any cryoprotective agent, all of the spermatozoa lost their motility. Addition of glycerol (0.22 to 0.87 M) caused a dose-dependent increase of sperm motility recovery. The highest recovery of forward and total motility was (32 and 35%, respectively) at 0.87 M. Further increase of the glycerol concentration caused a marked decrease in motility. Changes in the cooling rate particularly before and during freezing had a notable effect on the sperm motility recovery. There was no or low recovery (0-18%) of sperm motility when the cells were transferred directly to liquid nitrogen from the initial two cooling stages. The data demonstrate the importance of all of the cooling stages in the cryopreservation of the cells. Like glycerol, dimethyl sulfoxide (Me(2)SO) and ethylene glycol also showed a dose-dependent increase in motility recovery as well as a biphasic curve of cryoprotection. At optimal concentrations, dimethyl sulfoxide (1.00 M) and ethylene glycol (1.29 M) were effective in recovering sperm motility to the extent of 20 and 13%, respectively. Thus these reagents have markedly lower cryoprotection potential than glycerol.

Major goat sperm 105 kDa maturation antigen: purification, characterization, and effect of its antiserum on acrosin activity

A ConA binding membrane glycoantigen of 105 kDa molecular mass was purified from mature goat sperm by ion exchange and gel filtration chromatography. Of the detergents examined, the anionic deoxycholate was found to be highly effective in maximum solubilization of this sperm membrane antigen (SMA2). The analysis of the saccharide components by gas liquid chromatography revealed that the 105 kDa antigen (SMA2) contained the highest amount of mannose, followed by galactose and glucose in a ratio of 4:3:1. One amino sugar, N-acetylglucosamine, was also found to be present in the polysaccharide branching of the SMA2 antigen. The internal sulfydryl linkage is essential for the maintenance of the protein backbone of 105 kDa antigen. The antigen selectively resides on the anterior head of goat sperm. The binding of anti-SMA2 antibody to the integrated mature goat spermatozoa inhibited the release of acrosin after the induction of spermatozoa with Ca-ionophore.

Distribution of 105-kDa sperm unique antigen on goat epididymal mature spermatozoa

The sperm surface antigens are organized into topographic domains, specifically formed into the membrane during the sperm maturation in the epididymis. The present study was directed to determine the distribution of 105 KD sperm membrane antigen (SMA2) into the cell by affinity purified antibody, generated by 105 KD sperm antigen. The cytoimmunofluorescence study of the integrated sperm cell reveal that the antigen is localized in the anterior head overlying the acrosome. On immunoblotting of isolated head and flagellum polypeptides it has been demonstrated that this antigen is selectively present in the head membrane and absent in the flagellum. Because of its selective presence in the anterior head membrane overlying the region of acrosome on mature spermatozoa, the 105 KD sperm unique glyco-antigen may have a role in events leading to sperm-egg recognition. It is a first report of a high molecular mass membrane antigen being localized in the anterior head membrane of goat mature epididymal spermatozoa.

Goat sperm membrane: lectin-binding sites of sperm surface and lectin affinity chromatography of the mature sperm membrane antigens

The cell surface glycoproteins of goat epididymal maturing spermatozoa have been investigated using lectins as surface probes that interact with specific sugars with high affinity. Concanavalin A (ConA) and wheat-germ agglutinin (WGA) showed high affinity for mature cauda epididymal sperm agglutination, whereas RCA2, kidney beans lectin and peanut agglutinin caused much lower or little agglutination of the cells. The mature sperm exhibited markedly higher efficacy than the immature caput epididymal sperm for binding both ConA and WGA, as evidenced by sperm agglutination and the binding of the fluorescence isothiocyanate (FITC)-labelled lectins. FITC-ConA binds uniformly to the entire mature sperm surface whereas FITC-WGA binds to the acrosomal cap region of the head. The FITC-RCA2 mainly labelled the posterior head of mature cauda sperm. However, no WGA-specific glycoprotein receptors could be detected in sperm plasma membrane (PM) by WGA-Sepharose affinity chromatography. The data implied that the epididymal sperm maturation is associated with a marked increase in the ConA/WGA receptors and that WGA receptors may be glycolipids rather than glycoproteins. Analysis of the ConA receptors of cauda sperm PM identified by ConA-Sepharose affinity chromatography and subsequent resolution in SDS-PAGE demonstrated the presence of five glycopolypeptides of different concentrations (98, 96, 43, 27 and 17 kDa) of goat sperm membrane. The immunoblot of these ConA-specific glycopeptides with anti-sperm membrane antiserum showed that 98- and 96-kDa receptors are immunoresponsive.

Lipid changes of goat sperm plasma membrane during epididymal maturation

Highly purified plasma membranes of maturing goat caput-, corpus- and cauda-epididymal spermatozoa were isolated by aqueous two-phase polymer methods and their lipid constituents were analysed. Phospholipid (approx. 75% w/w), neutral lipid (approx. 15% w/w) and glycolipid (approx. 10% w/w) were the major sperm membrane lipids. There was a significant decrease in the total lipids (approx. 25% w/w), phospholipid (approx. 30% w/w) and glycolipid (approx. 80% w/w) contents of sperm membrane during epididymal maturation. On the contrary, the mature cauda-sperm membrane showed greater (approx. 50% w/w) neutral lipid content than that of the immature caput sperm. Phosphatidylcholine (PC), phosphatidylethanolamine (PE) and sphingomyelin were the phospholipids of the sperm membrane, the former two being the major lipids. Both PC and PE fractions consisted of three species--diacyl, alkylacyl and alkenylacyl forms, the last one being the dominant species in both PC and PE. Of all the phospholipids, diacyl PE decreased most strikingly (approx. 65% w/w) during sperm maturation. The neutral lipid fraction contained sterols, wax esters, 1-O-alkyl-2,3-diacylglycerol, triacylglycerol and fatty acids. Sterols represented nearly 75% w/w of the neutral lipids and cholesterol was the major component (approx. 95% w/w) of the sterol fraction. The sperm maturity was associated with marked increase of sterol (approx. 60% w/w) and steryl ester (approx. 200% w/w) and decrease (approx. 50-65% w/w) of the other membrane-bound neutral lipids. The glycolipid was identified as monogalactosyldiacylglycerol. The fatty acid profile of the various membrane lipids underwent marked alteration during the epididymal transit of the male gametes. Cholesterol/phospholipid and saturated/unsaturated fatty acid ratios increased greatly in the maturing sperm membrane. The altered lipid profile of the mature sperm membrane leads to changes in its fluidity that play an important role in determining the structure and functions of the biomembrane.