Specific protein synthesis in isolated epithelium of guinea-pig seminal vesicle. General features

Identification of the major rabbit and guinea pig semen coagulum proteins and description of the diversity of the REST gene locus in the mammalian clade Glires

The seminal vesicle secretions of guinea pig and rabbit were analyzed for semen coagulum proteins. Using SDS-PAGE we discovered a previously not fully recognized semen coagulum protein, Svp5, in the guinea pig and a single predominant component, SVP200, in the rabbit. Potential genes of these proteins were identified in genome databases by their homology with human and murine genes. The structure of their fullength transcripts was determined using seminal vesicle cDNA and sequencing primers based on genomic sequences. Homology searching indicated that both Svp5 and SVP200 were synthesized from composite genes that were the result of merger between two genes showing homology with human SEMG2 and PI3. For a deeper understanding of the evolution of the genes, we retrieved and analyzed genome sequences from the REST gene loci, encompassing genes of semen coagulum proteins and related rapidly evolving seminal vesicle-transcribed genes, of 14 rodents and 2 lagomorphs. The analysis showed that rodents of the suborders myomorpha, hystricomorpha, and castorimorpha had unique sets of REST genes, whereas sciuromorpha seemed to be lacking such genes. It also indicated a closer relationship between myomorpha and castorimorpha than to rodents of the two other analyzed suborders. In the lagomorph species, the pika appeared to be devoid of REST genes, whereas the rabbit had a single expressed REST gene, SVP200, and two pseudogenes. The structural similarity of semen coagulum proteins in rabbit and hystricomph species suggests that they are closely related. This was also supported by other similarities at their REST gene loci, e.g. the finding of a PI3-like gene in the rabbit that also had features in common with caltrin2 of hystricomorph rodents. The homologies indicate that hystricomorpha may have separated from myomorpha and castorimorpha before the separation of hystricomorpha from lagomorpha.

Characterization of glycoconjugates of guinea pig seminal vesicle by lectin histochemistry

In the present study, the expression of glycoconjugates in the guinea pig seminal vesicle was localized and partially characterized by lectin histochemistry using a battery of 30 different lectins specific for different carbohydrate residues. The results indicate that the glandular epithelium of the guinea pig seminal vesicle exhibits complex glycoconjugates rich in Man, beta-GlcNAc, beta-Gal, alpha/beta-GalNAc, Fuc and complex NeuAc(alpha2,6)Gal/GalNAc residues, as shown by its positive reactions to most lectins used. The Golgi region of the luminal secretory epithelial cells expresses a complex glycoconjugate pattern, as shown by its strong reactions to Man-(PSA, GNA), beta-GlcNAc-(S-WGA, PWA, DSA, UDA), beta-Gal-(RCA-I and -II), alpha/beta-GalNAc-(SBA, Jac, VVA, BPA) and complex NeuAc-(SNA) specific lectins, indicating that the secretory epithelial cells are active in glycosylation and secretion process. It was also shown in the present study that the basal and luminal epithelial cells are different in their glycoconjugates. The basal epithelial cells are rich in NeuAc(alpha2,3)Gal residues as they are stained specifically by MAA. The fibroblasts in the epithelial-smooth muscle interface and the smooth muscle cells close to the glandular epithelium are shown to express more glycoconjugates as they are stained intensely by GS-I-B4, GS-II and SBA. However, their role in the epithelial-stromal interaction in the seminal vesicle remains to be elucidated. In summary, the present study reports for the first time on the lectin binding patterns of the guinea pig seminal vesicle, and the results show that the seminal vesicle epithelium elaborates and secretes glycoconjugates in a complex pattern. Some of the lectins might be useful as histochemical markers for the secretory activity and specific structural components in the guinea pig seminal vesicle.

The cloning of a rapidly evolving seminal-vesicle-transcribed gene encoding the major clot-forming protein of mouse semen

Approximately 30 kb of the mouse genome, containing the gene for a major seminal vesicle transcript, has been cloned. The gene was identified by the similarity to members of a family with rapidly evolving genes that includes the gene encoding the major clot protein in rat semen, SVS II, and the human semenogelin genes. The nucleotide sequence of 16.9 kb was determined; this sequence encompasses the gene of 2215 bp plus 9-kb and 5.6-kb regions flanking the 5' and 3' ends of the gene. The transcription unit is divided into three exons, of which the first encodes the signal peptide, the second the secreted protein, while the third exon contains 3'-nontranslated nucleotides only. The transcript encodes a protein of 375 amino acid residues, including a signal peptide of 22 residues. The secreted polypeptide is a protein of Mr 38442 and is similar in sequence but smaller than the major clot-forming protein of rat semen, SVS II. It is highly charged at pH 7 and it has an isoelectric point of 10.68. The central part of the protein consists of tandem repeats that might serve as a substrate for transglutaminase.

Constitutive protein secretion by guinea-pig seminal vesicle epithelial cells

1. Secretion of pulse-labelled protein by the isolated epithelium of guinea-pig seminal vesicle epithelium was rapid, unaffected by cholinergic and adrenergic drugs, cyclic nucleotides or changes in the sodium, potassium and calcium concentrations of the "chase" medium. 2. Low temperature, NH4Cl, hyper- and hypo-osmolarity and membrane-stabilizing agents inhibited secretion which was also dependent on aerobic metabolism. 3. Monensin reduced secretion of the six labelled, relatively low molecular weight proteins recovered from the medium in a concentration-dependent, apparently non-specific manner.

Electrophoretic pattern of rodent seminal vesicle proteins as revealed by silver staining

Electrophoresis of seminal vesicle secretions (SVS) from several rodents showed a very simple pattern composed of 3-5 main protein bands when an anionic dye (Coomassie brilliant blue) was used. However, use of a silver staining method showed a more complex protein spectrum, and several minor components of 12-90 kD, were clearly revealed. Western blotting using antibodies to SVS demonstrated that these minor protein components were not serum contaminants. Rat, mouse and hamster SVS shared antigenic determinants which were not related to rabbit SVS.

The major clotting protein from guinea pig seminal vesicle contains eight repeats of a 24-amino acid domain

The complete amino acid sequence of the major clotting protein from the guinea pig seminal vesicle (SVP-1) has been determined by nucleotide sequencing of cDNA clones corresponding to the 3' terminus of an mRNA that codes for a protein precursor to SVP-1. The first 40 amino acids of the derived protein sequence are identical to those determined by N-terminal sequencing of SVP-1 isolated from the lumen of the seminal vesicle. This finding confirms that SVP-1 is cleaved from the C terminus of a larger precursor protein. The portion of the nucleotide sequence that codes for SVP-1 contains eight highly homologous but imperfect repeats of a 72-nucleotide domain. This repeated structure is also evident at the amino acid level. The consensus 24-amino acid repeat unit contains two lysine and three glutamine residues. Since the clotting of SVP-1 is known to involve the formation of gamma-glutamyl-epsilon-lysine crosslinks, it is likely that the 24-amino acid repeating unit is the unit of function of SVP-1.

The effects of androgen on the transcription of specific genes in guinea pig seminal vesicle epithelium

Steroid hormones have been shown to have highly differential effects on the expression of abundant cell-specific protein genes in a multitude of model tissues. In rat seminal vesicle, for example, DNA clones representing two major secretory protein genes have been used to show that both of the genes are differentially regulated by androgen. In this paper, we have examined the effects of androgen on the transcription of two major secretory protein genes in guinea pig seminal vesicle epithelium. Nuclear run-off experiments were used to show that castration of the adult resulted in a 3-fold decrease in total transcription activity. Surprisingly, the decrease in total transcriptional activity was not reflected in a differential decrease in the transcriptional activity of the two major secretory protein genes. When the effects of castration on the transcriptional activity of the major secretory protein genes were compared to the effects on other genes, it was found that the transcriptional activity of each gene examined was decreased by the same magnitude as the major secretory protein genes. Similarly, the transcriptional activity of every gene examined increased by the same magnitude as the major secretory protein genes during hormone repletion of the castrated adult. Thus, in contrast to the differential effects of steroids on the transcription of abundant cell-specific proteins in many other steroid-dependent tissues, the transcription of major secretory proteins in guinea pig seminal vesicle epithelium appears to be regulated in parallel with many other genes. The generalized effects of androgen on transcriptional activity could account for the generalized effects of androgen on seminal vesicle epithelial cell structure and function.

Effects of estradiol on protein synthesis in the fibromuscular stroma from the guinea pig seminal vesicle

Estradiol treatment of intact and castrate adult male guinea pigs produced selective increases in the rate of [35S]methionine incorporation in vitro into 12,500 g soluble peptides of 58,000 and 97,000 Mr from the seminal vesicle fibromuscular stroma. Total incorporation into the 12,500 g soluble fraction was unchanged in estrogen-treated, intact animals. In castrate animals, the rate of total incorporation in the 12,500 g fraction was decreased by more than 50 per cent. Estrogen treatment of castrate animals restored the rate of total incorporation to that observed in untreated intact animals, indicating that estrogen was capable of maintaining normal levels of total incorporation into the 12,500 g soluble protein fraction. In castrate animals the administration of tamoxifen prevented the estrogen-induced maintenance of total [35S]methionine incorporation and inhibited the selective increase in incorporation into the 58,000 Mr peptide. From the results of this and other studies it may be suggested that estrogen modulates sex accessory stromal tissue function by altering the synthesis of specific proteins via an interaction with specific estrogen binding sites.

Androgen regulation of protein synthesis in the seminal vesicle fibromuscular stroma

The fibromuscular stroma (FMS) separated from the seminal vesicles of adult guinea pigs incorporated [35S]methionine into a 12 500 X g soluble fraction in vitro. Incorporation decreased 60% in tissues from 7-day castrates with no further change up to 21 days post-castration. Administration of 5 alpha-dihydrotestosterone prevented this decrease. Castration did not appear to increase the degradation of newly synthesized protein, or to alter the distribution between soluble and particulate subcellular fractions. Using SDS-PAGE and fluorography to quantitate [35S]methionine incorporation into specific proteins, three protein classes were identified which responded differentially to castration: (1) bands at 110 000 and 24 000 Mr decreased by 95%; (2) bands at 58 000 and 97 000 Mr were unchanged; (3) multiple bands decreased in proportion to total incorporation. Administration of 5 alpha-dihydrotestosterone could not fully maintain, at control levels, the synthesis of the 110 000 and 24 000 Mr bands. These results demonstrate that the FMS of the guinea pig seminal vesicle can serve as a useful model system for studying hormonally regulated functions of male sex accessory stromal tissue.

Transglutaminases and the clotting of mammalian seminal fluids

Rapid coagulation of seminal fluid in rats, guinea pigs, and several other mammalian species including certain non-human primates is responsible for the post-coital formation of copulatory plugs in the vagina. The clotting of rodent seminal plasma results from coagulation of certain proteins derived from the seminal vesicles by enzymes secreted mainly by the coagulating (anterior prostate) gland. Several lines of evidence indicate that the clotting enzymes of coagulating gland secretions are transglutaminases, and that the extreme insolubility of the seminal clot in rodents is due to transglutaminase-catalyzed formation of epsilon(gamma-glutamyl)lysine cross-links between polypeptide chains. Various features of the apparently unique forms of transglutaminases produced by rat coagulating gland and the actions of these enzymes on vesicular secretory and other proteins are discussed. The aliphatic polyamines spermidine and spermine are incorporated covalently into the proteins of the clot as the corresponding N-mono-epsilon-(gamma-glutamyl)- and N,N-bis(gamma-glutamyl)-adducts during the enzymatic coagulation process. At the greater than millimolar concentrations at which cross-spermidine and spermine are present in normal rat seminal plasma, these polyamines attenuate the formation of hard clots in reconstituted rat semen coagulation systems, seemingly by competing with lysyl residues in vesicular secretion proteins as transglutaminase amine donor substrates, and thus preventing formation of epsilon-(gamma-glutamyl)lysine cross-bridges. It is proposed that in those species such as the rat and man in which seminal plasma contains large amounts of spermidine and(or) spermine of prostatic origin, the seminal polyamines may serve to stop blockage of the urethra by preventing too explosive a rate of seminal clot formation during the ejaculatory process.

Isolation and culture of rat seminal vesicle epithelial cells. The use of the secretory protein SVS IV as a functional probe

A method for the isolation and culture of seminal vesicle epithelial cells obtained from control and androgen-primed sexually-immature, uncastrated rats is described. This method allows the establishment of monolayer cultures from aggregates of seminal vesicle epithelial cells isolated after trypsin and collagenase digestion. Phase contrast and transmission electron microscopic methods demonstrate that cell aggregates, after attaching to the substrate, establish within 48 h a colony-like, epithelial-like growth pattern. Immunofluorescent localization studies of SVS IV, an androgen-dependent secretory protein purified from rat seminal vesicle secretion, show that cultured seminal vesicle epithelial cells are immunoreactive. An electrophoretic analysis of [35S]methionine-labeled secretory proteins immunoprecipitated with rabbit anti-SVS IV serum demonstrate that, whereas SVS IV is newly-synthesized and accumulated in the medium of cultured seminal vesicle cells established from androgen primed rats, cultured cells from control rats appear to synthesize and accumulate SVS IV in a precursor form. Results of this work show that seminal vesicle epithelial cells in culture not only retain several structural features representative of the tissue but also serve as a potential system for the study of androgen action.

Developmental regulation of secretory protein synthesis in rat seminal vesicle

This paper reports a developmental study of one of the major secretory proteins (SVS IV) of the rat seminal vesicle. Measured by radioimmunoassay, SVS IV is detectable even in very young rats (5 days old) but does not begin to accumulate in massive amounts until animals reach about 35 days of age. We have compared SVS IV synthesis by minced tissue from rats undergoing sexual maturation (25-60 days of age) with levels of translatable SVS IV mRNA present. Between 25 and 60 days of age, the proportion of newly synthesized protein devoted to SVS IV by tissue minces increased from 0.8% to 20%. In contrast, the proportion of total RNA devoted to translatable SVS IV mRNA was already high in the immature glands and increased less than 4-fold during development. These results seem to indicate that factors other than the presence of potentially translatable message regulate the rate of net synthesis of SVS IV during seminal vesicle maturation.

Nuclear acceptor sites for androgen-receptor complexes in seminal-vesicle epithelium

An assay method in vitro was developed and applied to quantify acceptor binding of steroid-receptor complexes in nuclei from isolated epithelium of guinea-pig seminal vesicle. Steroid-receptor complex prepared from 1-day-castrated animals was incubated with purified nuclei from 1-28 day-castrated animals in a medium containing 0.15 M-KCl. Free and bound steroid-receptor complexes were measured and the data were submitted to Scatchard analysis. With nuclei from 1-day-castrated animals the Kd for binding of cytosolic [3H]dihydrotestosterone-receptor complexes was found to be 0.83 X 10(-10) M and the capacity for binding was 0.35 pmol/mg of nuclear DNA. Scatchard analysis consistently disclosed only a single line of constant slope and gave the same kinetic constants for nuclei obtained from animals castrated up to 28 days before assay. Administration of 2 mg of dihydrotestosterone, 3 alpha-androstanediol or androsterone or 100 microgram of oestradiol-17 beta 1 h before killing of the 1-day-castrated animals that provided the nuclei resulted in a significant decrease in nuclear acceptor binding of the steroid-receptor complex compared with untreated animals. Thus our assay method disclosed nuclear acceptor sites that may be involved in responses to androgens (and oestrogens) in vivo. We conclude that there is a class of nuclear accept or sites of high affinity and limited capacity that may be occupied by steroid-receptor complexes in vivo.