Identification of rat prostatic steroid binding protein (PSBP) as an immunosuppressive factor

Prostatic steroid binding protein (PSBP) is the major protein produced ( approximately 20% of the total cytosolic protein) and secreted into the seminal fluid by the rat ventral prostate but its physiological function has not been elucidated yet. Since PSBP is secreted into the seminal fluid (which is itself a potent immunosuppressor) and has strong homology with uteroglobin (which possess an important anti-inflammatory function) our aim was to determine what effect, if any, PSBP would have on the immune system. With that purpose in mind we performed mononuclear cell cultures in the presence or absence of purified PSBP and analysed the effect of this protein on different functional parameters. PSBP inhibits the mitogen-induced proliferation of normal rat spleen mononuclear cells (MNC) specifically and in a dose-dependent manner. It reduces the production of IL-2 and the expression of its receptor (analysed by flow cytometry) which are important events for lymphocyte proliferation. Also, PSBP was able to inhibit OVA-specific proliferation of lymph node cells from previously primed animals. The immunosuppressive effect of PSBP is not due to an inherent toxic effect to the cells, since the cell viability was kept intact at the different times of culture studied. We also analysed the effect of rat PSBP on mitogen-induced proliferation of mouse spleen and human blood MNC. The proliferation was strongly abolished in a dose-dependent and non-species specific fashion. Moreover, PSBP strongly inhibits the human mixed lymphocyte reaction. Taken together, the present data support evidence for a new type of function for PSBP. We report that PSBP is a potent immunosuppressor factor and we describe its effect on the immune function in vitro. Here, we discuss the possible implications of these findings in the protection of sperm from immunologic damage in the feminine reproductive tract.

Isolation and characterization of mouse probasin: An androgen-regulated protein specifically expressed in the differentiated prostate

BACKGROUND

The development and growth of the prostate gland is regulated, in part, by a variety of steroid and polypeptide growth-factor hormones. As a consequence of hormone action, the prostate gland will produce a number of tissue-restricted gene products. Characterization of the regulation, expression, and function of genes encoding prostate-specific proteins is critical to our understanding of prostate biology. Probasin is a prostate-specific gene originally isolated from the rat and has been exploited as a marker of prostate differentiation and to elucidate androgen action. Furthermore, a number of transgenic mouse models of prostate cancer have been established based on the regulatory elements derived from the rat probasin gene. In this report, we describe the isolation and characterization of the mouse probasin ortholog to further facilitate studies related to hormone action in the prostate and the generation and characterization of novel autochthonous models of prostate cancer.

METHODS

Mouse probasin cDNA was isolated from a phage library, and the DNA sequence was determined. The predicted protein sequence was used to generate specific oligonucleotide primers and antibodies. Probasin protein and RNA expression were examined by immunobloting, immunohistochemistry, and RT-PCR, in normal mouse prostate tissue and tumor tissues derived from the autochthonous "transgenic adenocarcinoma of the mouse prostate" (TRAMP) model. Regulation of probasin expression in response to surgical castration and hormone supplementation was also characterized.

RESULTS

Several points of evolutionary sequence conservation were identified between mouse and rat probasin, especially in the 3' untranslated region. Specific polyclonal antibodies were generated to peptide fragments, and the temporal and spatial pattern of probasin expression was examined. The expression of probasin was primarily localized to the apical membrane of differentiated secretory epithelium. Probasin mRNA and protein were absent from the poorly differentiated tissue of TRAMP tumors. Probasin was found to be androgen-regulated. In contrast to data from studies on rat probasin, no postcastration rebound of mouse probasin mRNA was observed.

CONCLUSIONS

Probasin is a marker of differentiation and androgen action in the mouse prostate, and strong sequence conservation between mouse and rat probasin supports an essential role for this gene in the biology of the prostate gland. Isolation and characterization of mouse probasin will facilitate further development and analysis of autochthonous mouse models of prostate cancer.

Alterations in constituent urinary proteins in response to bladder outlet obstruction in rats

PURPOSE

Benign prostatic hyperplasia, resulting in bladder outflow obstruction, induces well recognized clinical symptoms and morphologic bladder changes. Despite these phenomenon, relatively little is known with regard to the precise molecular events occurring in the bladder as a consequence of obstruction. In an effort to screen for alterations in bladder gene expression induced by obstruction, and/or alterations in uroepithelial integrity, this study compared pre- and post-obstructive constituent urinary proteins in an animal model.

MATERIALS AND METHODS

Outlet obstruction was created using a previously established model system. Experimental animals were surgically obstructed for either 2 or 7 days, at which time the urine was aspirated and the bladders removed and weighed. Urinary proteins were separated using 2-D PAGE. Following comparison of sham versus experimental animals, microsequencing was performed on proteins that were down regulated.

RESULTS

Duplicate experiments confirmed the presence of outflow obstruction. Statistically significant increases (p <0.01) in bladder weights were seen at 2 and 7 days in the obstructed groups as compared with both sham and control groups. 2-D PAGE demonstrated a down regulation of three urinary proteins post-obstruction. Microsequencing identified these proteins as prostatic steroid-binding protein C3 precursor (pI=5.5, MW=15000), glandular kallikrein 9 (S3) precursor (pI=6.2, MW=19000), and glandular kallikrein 8 (P1) precursor (pI=6.2, MW=33000).

CONCLUSIONS

Bladder outflow obstruction alters constituent urinary protein composition in an animal model system. The precise etiology of these alterations remains to be defined.

Characterization and developmental expression patterns of testicular androgen-binding protein in the Djungarian hamster (Phodopus sungorus)

Studies were conducted to characterize Djungarian hamster androgen-binding protein and examine its expression during development. The cDNA encoding the full length testicular androgen-binding protein was cloned and, except for two suspected polymorphisms, shared a common primary sequence with hepatic sex hormone-binding globulin. A single androgen-binding protein/sex hormone-binding globulin gene was identified and a 1.7 kb mRNA encoding androgen-binding protein/sex hormone-binding globulin was present in both the testis and liver. Testicular homogenates contained specific 5 alpha-dihydrotestosterone-binding activity that was identified as androgen-binding protein. In the prepubertal testis, immunoreactive androgen-binding protein/sex hormone-binding globulin subunits ranged from 46 kDa to 60 kDa, with the majority of isoforms > 50 kDa. These subunits were distinct from the major 55 kDa and 51 kDa isoforms of sex hormone-binding globulin present in the serum of prepubertal hamsters. Deglycosylation studies demonstrated that size heterogeneities were the result of developmentally specific glycosylation patterns. Expression of androgen-binding protein by the testis was upregulated during puberty and coincided with a decline in serum sex hormone-binding globulin activity. The tissue- and age-dependent expression of specific androgen-binding protein and sex hormone-binding globulin variants suggests that these proteins play different roles in steroid-mediated sexual development.

Androgens transcriptionally regulate the expression of cystatin-related protein and the C3 component of prostatic binding protein in rat ventral prostate and lacrimal gland

In this report, it is demonstrated that the C3 component of prostatic binding protein (PBP) is also expressed and androgen regulated in the exorbital lacrimal gland, as shown previously for cystatin-related protein (CRP), another abundant secretory protein from the ventral prostate. The presence of C3 messenger RNA (mRNA) could be demonstrated by both Northern blot hybridization and PCR amplification and sequencing. The mRNAs encoding the C1 and C2 components of PBP, however, were undetectable. At the protein level, the C3 component in the lacrimal gland is glycosylated and linked by disulfide bridges to a new 10-kDa component not reacting with the PBP antiserum. As shown previously for CRP, the expression of C3 in the lacrimal gland requires the simultaneous presence of androgens and a functional androgen receptor. The effects of castration and androgen treatment on CRP and C3 mRNA concentrations were studied by Northern blot and dot blot hybridization; effects on transcription rates were determined by nuclear run-on assay. Two days after castration, the relative abundance of CRP mRNA had declined significantly (P < 0.01) to 10.5 +/- 1.5% (+/-SEM) of precastration levels in the prostate and to 14.5 +/- 8.0% in the lacrimal gland; the transcription rates declined to 14.3% and 10.0%, respectively. The C3 mRNA level and transcription rate in the prostate showed a more moderate decrease (P < 0.05) to 40.6 +/- 8.5% and 41.7%, but were hardly measurable in the lacrimal gland. Androgen administration resulted in a rapid increase in the transcription rates, which reached or exceeded control levels after 6-9 h of treatment and clearly preceded the increase in mRNA levels. It is concluded that the lacrimal gland, which can be studied conveniently in female and long term androgen-depleted animals offers a suitable model for the study of androgen-regulated gene expression.

Partial purification of a putative membrane bound androgen binding protein in the dog cauda epididymis

1. An androgen binding protein(s) has been partially purified from cell plasma membranes of dog epididymides. 2. The protein(s) has a pI of 5.3 and an association constant of (1.13 x 10(9) M-1). 3. Conclusive demonstration of androgen receptors in epididymal plasma membranes would be of significance in understanding epididymal physiology.

An anti-probasin monoclonal antibody recognizes a novel 40-kDa protein localized in rat liver and a specific region of kidney urinary tubule

Immunoblotting with a monoclonal antibody against probasin (rat prostatic secretory protein) showed that a 40-kDa protein antigenically related to probasin was localized in rat liver and kidney. The contents of probasin in these organs were negligible. Immunostaining revealed that the 40-kDa protein (probasin-related antigen: PRB-RA) was expressed in the liver parenchymal cells and the kidney urinary tubular epithelial cells in outer stripe. The content of PRB-RA in the kidney was low during 0 to 2 weeks of age, then rapidly increased about 10-fold from 2 to 8 weeks of age. The content in the liver increased about 2-fold during the period, reaching a value of 10-12 ng/micrograms protein, which was ten times higher than that in the kidney. PRB-RA was purified from rat liver by ion-exchange chromatography, gel filtration and fast protein liquid chromatography on a hydroxyapatite column. The purified protein formed insoluble aggregates in the absence of a detergent, and it had a blocked amino terminal. The amino acid sequence of a peptide generated by tryptic digestion of alkylated PRB-RA was determined. Computer analysis showed that there was no protein having a significant homology with the peptide. These results indicate that a novel 40-kDa protein with a structural similarity to probasin is localized in rat liver and kidney, and might bear a function specific to these organs.

The 56 kDa androgen binding protein is an aldehyde dehydrogenase

We have described a 56 kDa protein from genital skin fibroblasts that specifically binds androgen and that is generally not expressed in genital skin fibroblasts from patients with androgen insensitivity due to genetic defects of the androgen receptor. We have isolated a partial cDNA clone for the 56 kDa protein from an expression library of genital skin fibroblasts. In vitro translation of message selected with this clone faithfully produces the 56 kDa protein which can be immuneprecipitated with an anti-56 kDa antiserum. Northern blots probed with this clone show a 2.2 kb message, which parallels the expression of the 56 kDa protein. The sequence of this 998bp clone is identical to human liver aldehyde dehydrogenase 1, the cytoplasmic isoenzyme. On activity gels of genital skin fibroblast cytosol covalently labelled with androgen, aldehyde dehydrogenase activity comigrates with the single band labelled specifically with androgen. Thus, the 56 kDa androgen binding protein is an aldehyde dehydrogenase, which is prominently expressed in normal genital skin fibroblasts, but not in non-genital skin fibroblasts.

Partial purification of androgen binding protein from bull epididymis

An androgen binding protein (ABP), with an equilibrium dissociation constant of 4.2 nM and a molecular weight of about 100 kDa, has been purified from bull epididymal extracts using a four-step procedure. These preliminary results underline the main difficulties encountered in the purification of this protein present at a very low concentration (i.e. 50-fold less than in rat or rabbit epididymides). Ammonium sulfate precipitation is not a suitable step due to the formation, in presence of salt, of insoluble material leading to a loss of ABP. Lipids, particularly phospholipids, might be implicated in this phenomenon. Several steps, including anion exchange in batch followed by concentration, affinity chromatography and HPLC gel filtration allowed us to obtain a 7667-fold purified protein with a 9% yield.

Prostatein C3-mRNA: a sensitive marker of androgen-responsiveness in prostate explant cultures

Prostatein is an androgen-dependent protein which is secreted by the rat ventral prostate. To determine if prostatein or its mRNA were responsive to androgen in vitro, prostate explants were cultured in media containing 0 or 25 nM dihydrotestosterone (DHT), estradiol (E2), or cortisol (F). Prostatein concentrations in medium were measured by radioimmunoassay at 2 and 4 days and in homogenates at 4 days. They were not changed significantly by any of these steroids. The concentration of the mRNA for the C3-subunit of prostatein was determined by dot hybridization at 0, 2, 4, 6, and 8 days. It was decreased significantly by 2 days when compared with explants cultured in the presence of DHT and significant differences persisted through 8 days. In conclusion, quantitation of the mRNA for the C3-subunit of prostatein in short-term cultures of ventral prostate explants appears to be more sensitive to changes in androgen concentration than does measurement of prostatein, per se. Prostatein C3-mRNA may be a useful marker for in vitro studies of androgen agonists and antagonists.

The presence of a hitherto undefined high-capacity androgen binding macromolecule in human ovarian cancer tissue

Sex hormone binding globulin (SHBG) is known to interfere in the quantitation of androgen receptors (AR) if dihydrotestosterone (DHT) is used. We used a monoclonal antibody to remove SHBG from cytosol. In cytosol of benign prostatic hyperplastic (BPH) tissue low capacity binding for DHT, but not for R1881, was found after removal of SHBG. AR were detected in 18 of 20 ovarian cancer cytosols. In the two AR-negative cases, non-saturable binding for DHT, testosterone and R1881 was observed. Incubation with anti-SHBG did not change this. An hitherto undefined androgen binding macromolecule(s), with high-capacity binding for natural and synthetic androgens, but not for estrogen and progesterone, seems to be present in these ovarian cancer tissues. The functionality of these androgen binding macromolecules in ovarian cancer is yet to be demonstrated.

The androgen-dependent rat prostate protein, probasin, is a heparin-binding protein that co-purifies with heparin-binding growth factor-1

Rat prostate extracts contain an abundant 20-22 kilodalton heparin-binding protein with near identical chromatographic properties, but only 0.2-1% of the mitogenic activity, of bovine brain heparin-binding growth factor-1 (acidic fibroblast growth factor). Amino terminal amino acid sequence (met-met-thr-asp-lys-asn-leu-lys-lys-lys-ile-glu-gly-asn-trp-arg-thr-val -tyr- leu-ala-ala-ser-?-val-glu-lys-ile-asn-glu-gly-ser-pro) and immunochemical analysis revealed that the protein is identical to the androgen-dependent protein "probasin".

Characterisation and covalent labeling of the human placental methyltrienolone binding protein

Human placental cytosol contains an androgen binding protein which binds the synthetic androgen methyltrienolone (R 1881) with high affinity (Kd 8.7 nM) and with an average binding capacity of 518 fmol/mg cytosol protein. This study provides further evidence that this protein is distinguishable from classical androgen receptors on the basis of steroid specificity and sulphydryl group sensitivity. Covalent labeling studies have shown this protein, which we have called "the methyltrienolone binding protein", to have a mol. wt of 67,000 daltons.

Evidence for an androgen binding protein in the testis of a teleost fish (Salmo gairdneri R.): a potential marker of Sertoli cell function

A factor binding tritiated testosterone was detected using "steady-state" polyacrylamide-gel electrophoresis, in rainbow trout genital tract. It migrated with a Rf identical to that of rat ABP. This binding was thermolabile, and was competitively inhibited by unlabelled testosterone. The steroid binding protein was found in cytosols from trout testes which had been previously perfused to avoid blood contamination, trout seminal plasma and in testicular explants incubation media. Using a quantitative assay and a Scatchard analysis, 25-50 pmol binding sites per gram gonad were found in testis cytosol. Binding affinity constant for testosterone in the various samples was close to 4 x 10(8) M(-1). The dissociation of steroid-protein complex was rapid (t 1/2 approximately 1.5 min). Hormonal specificity was studied by the competition of 3H-T binding with several concentrations of unlabelled competitors and the following order for affinities was obtained: dihydrotestosterone approximately androstenedione greater than testosterone greater than oestradiol greater than 17 alpha, 20 beta DHP greater than 11KT greater than cyproterone acetate greater than cortisol. High testicular cytosol and seminal plasma concentrations and apparent in vitro production indicate that the testis may synthesize an ABP-like protein in the trout. Such a factor would provide a unique marker of Sertoli cell activity and regulation in various physiological or experimental situations.

Purification and immunochemical characterization of the cytoplasmic androgen-binding protein of rat liver

The cytoplasmic androgen-binding (CAB) protein of the male rat liver has been implicated to play a role in the androgen-dependent regulation of alpha 2u-globulin synthesis. The liver of the adult male rat contains about 50 fmol of specific high-affinity androgen-binding activity per milligram of total cytosolic protein. Photoaffinity labeling with [3H]R-1881 followed by SDS-polyacrylamide gel electrophoresis and autoradiography shows that the CAB is a 31-kilodalton protein. By means of DEAE-cellulose chromatography and preparative SDS-polyacrylamide gel electrophoresis, we have purified the CAB protein to electrophoretic homogeneity and have raised polyclonal rabbit antiserum that is monospecific to this protein. In the sucrose density gradient, the antiserum reacted with the androgen-binding component of the male liver cytosol prelabeled with tritiated dihydrotestosterone. Western blot analysis of the liver cytosol showed that the antiserum recognizes only the 31-kDa androgen-binding component. Such immunoblotting also showed that unlike the young adult, the androgen-insensitive states during prepuberty and senescence are associated with a marked reduction in the hepatic concentration of the immunoreactive CAB protein. No immuno-chemical cross-reactivity between CAB and another androgen-binding component of Mr 29K (which is associated with androgen insensitivity during prepuberty and senescence) was observed. The latter finding favors the possibility that 31- and 29-kDa androgen-binding components may have distinct sequence structure.

Crystallization of prostatic binding protein

Prostatic binding protein is a dimeric glycoprotein capable of binding a variety of steroids. This protein is a major component of rat prostate cytosol making it possible to purify milligram quantities. Hexagonal crystals of X-ray diffraction quality have been grown from phosphate buffered ammonium sulfate solution by vapor diffusion methods. These crystals which are reasonably stable to X-rays, show diffraction to 6.3 A and belong to space group P6(1) or P6(1)22 or the enantiomorphs. The unit cell has dimensions a = 88.7(5) A, c = 405(2) A, contains 24 molecules and has a specific volume of 2.8 A3/Dalton.

Monoclonal antibodies to rat androgen-binding protein recognize both of its subunits and cross-react with rabbit and human testosterone-binding globulin

A series of four monoclonal antibodies to rat androgen-binding protein (ABP) has been developed. These antibodies recognize both the heavy (48,400-dalton) and light (43,000-dalton) subunits of the native ABP molecule. In addition, they recognize the subunits from which Asn-linked oligosaccharides have been removed by treatment with N-glycanase, indicating that these moieties do not form the immunological determinants recognized by the antibodies. Two of these antibodies are capable of recognizing both nondenatured ABP, as assessed by dot blot analysis, and denatured ABP, as determined by Western blot analysis of ABP after electrophoresis under denaturing conditions. The immunoreactivity of denatured ABP is decreased with two of the antibodies, suggesting that they more readily recognize the antigenic epitopes when the protein is in its native configuration. The antibodies were capable of immunoprecipitating covalently labeled ABP from solution. All four monoclonal antibodies produced were determined to be immunoglobulins M by both enzyme-linked immunosorbent assay and Ouchterlony immunodiffusion even though the initial serum response of the immunized animals indicated the presence of immunoglobulins G. All of the monoclonal antibodies raised against rat ABP cross-reacted with rabbit and human testosterone-binding globulin (TeBG). They were able to detect two subunits when Western blots of intact rabbit [mol wt (Mr, 43,000 and 40,500] or human (Mr, 47,600 and 44,500) TeBG were probed, but only a single subunit (Mr, 39,300) when deglycosylated samples of rabbit TeBG were analyzed.

The apparent molecular weight of androgen-binding protein (ABP) in the blood of immature rats differs from that of ABP in the epididymis

When androgen-binding protein (ABP) in unfractionated immature (20-day old) male rat serum was covalently labeled with the site-specific photoaffinity ligand [3H]17 beta-hydroxy-4,6-androstadien-3-one and analyzed on 5.6% polyacrylamide tube gels containing SDS (SDS-PAGE), a protein of Mr 33,700 +/- 1200 was shown to be specifically labeled. Rat epididymal ABP from unfractionated cytosol analyzed under identical conditions exhibited two androgen-specific peaks of radioactivity, Mr 49,900 +/- 600 and Mr 44,100 +/- 800, which correspond to the previously described subunits of ABP. The apparent molecular weight differences between serum and epididymal ABP were further assessed on preparations of serum ABP that had been partially purified by chromatography on Affi-Gel blue (to remove albumin) and on Sephadex G-150 (to remove other proteins). When these preparations of ABP were photolabeled and analyzed by SDS-PAGE as above, two subunits of Mr 61,700 +/- 1300 and Mr 47,100 +/- 700 were resolved. Serum and epididymal ABP were further purified by androgen affinity chromatography. When these preparations were subjected to SDS-PAGE on slab gels containing 10% polyacrylamide and identified by fluorography of photolabeled ABP or by immunochemical localization following electrophoretic transfer to nitrocellulose, differences in the apparent molecular weight of ABP from the two sources persisted. Immunochemical localization studies on ABPs that had been desialylated with neuraminidase indicated that there was an increased mobility of the subunits, as one would anticipate from removal of carbohydrate. Differences in apparent molecular weight of ABPs from the two sources are likely due to differences in glycosylation.

Cytoplasmic androgen binding protein of rat liver: molecular characterization after photoaffinity labeling and functional correlation with the age-dependent synthesis of alpha 2u-globulin

The liver of the mature male rat contains a moderate affinity (Kd = 10(-8)M), low-capacity, cytoplasmic androgen binding protein (CAB) whose appearance during puberty and disappearance during senescence correlate with the androgen-dependent synthesis of alpha 2u-globulin. Molecular properties of CAB were examined by photoaffinity labeling with tritiated methyltrienolone (R-1881), a synthetic androgen, and by its localization within the hepatocytes which are competent to produce alpha 2u-globulin. Photoaffinity labeling of the liver cytosol derived from postpubertal male rats, followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography, showed a predominant androgen binding band corresponding to Mr 31,000. This 31-kilodalton (kDa) binding component was conspicuously absent in the liver of androgen-insensitive prepubertal and senescent male rats and in adult male rats treated with estradiol-17 beta. In addition, unlike the cytoplasmic extract, the nuclear lysate of the male rat hepatocytes did not contain the 31-kDa androgen binder. Disappearance of the 31-kDa androgen binding band from the cytosolic fraction of androgen-insensitive animals was associated with a concomitant appearance of a minor androgen binding component of apparent Mr 29,000. The livers of postpubertal male rats normally contain two subpopulations of hepatocytes, only one of which is highly active (competent) in alpha 2u-globulin synthesis. Separation of these two subpopulations through a fluorescence-activated cell sorter followed by whole cell labeling showed more than a 2-fold higher uptake of R-1881 by the competent cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Purification of androgen-binding protein from rat testis using high-performance liquid chromatography and physicochemical properties of the iodinated molecule

The androgen-binding protein (ABP) has been purified 87,500-fold from rat testis using 4 steps of HPLC, with a yield of 14%. The molecule was 99% pure with a specific activity estimated to 16,600 pmol/mg protein. The iodinated molecule was eluted in 2 peaks in Sephacryl S300 gel filtration with a molecular mass estimated to be 92,600 +/- 3300 and 50,300 +/- 4000 Da. The column isoelectrofocusing of 125I-ABP demonstrated 3 isoproteins isoelectric at pH 4.7, 4.9 and 5.3 and the sedimentation coefficient was estimated to be 4.7 S in sucrose gradient ultracentrifugation. The 125I-ABP had similar physiochemical properties to the non-labelled ABP of epididymis.

Production of an antibody to mouse salivary androgen binding protein (ABP) and its use in identifying a prostate protein produced by a gene distinct from Abp

We previously demonstrated polymorphism of a mouse salivary protein which, because of its ability to bind androgen, we designated androgen binding protein (ABP) and its structural gene, Androgen binding protein (Abp). This report describes the purification of salivary ABP and presents the amino acid composition of its subunits. Using an antibody raised against the purified protein, we demonstrated the presence of cross-reactive material (CRM) in mouse parotid, submaxillary, sublingual, and prostate glands by double immunodiffusion. Immunohistochemical detection of proteins on electroblots of polyacrylamide electrophoresis and isoelectric focusing gels, however shows that the prostate CRM is a protein with electrophoretic and isoelectric focusing behavior distinct from that of salivary ABP isoproteins. Because the DBA/2J strain has a variant of salivary ABP, that strain was analyzed to determine if a prostate ABP-CRM variant was present. The approach was hampered by an inability to detect CRM in the prostates of DBA/2J mice. Prostate CRM was detected, however, in some progeny from repeated backcrosses of DBA/2J X C3H/St hybrids to the C3H/St and DBA/2J parental strains. The prostate CRM detected in samples from animals heterozygous for salivary Abp appears to be identical to C3H/St prostate CRM, suggesting that the gene controlling prostate ABP-CRM is related to, but distinct from, Abp. The reason for reduced or absent CRM in the prostates of DBA/2J males is unknown but this finding suggests that there are strain-related differences in the expression of this prostate protein.

Purification and characterization of a steroid-binding sialoglycoprotein from rat ventral prostate

An androgen-dependent sialoglycoprotein was purified from the secretion of rat ventral prostate by chromatofocusing and DEAE-Sepharose column chromatography. It showed a native molecular weight of 47,000 and consisted of two dissimilar subunits with molecular weights of 20,000 and 18,000. However, each subunit contained a common peptide with molecular weight of 16,000. It also contained 442 +/- 62 micrograms sialic acids per milligram protein and bound pregnenolone with a binding affinity of 1.2 microM-1. Its amino acid composition was similar to those of other known prostatic steroid-binding proteins. Hence, we propose that it is the sialylated form of rat prostatic steroid-binding protein.

[Characterization and partial purification of androgen binding proteins from human prostate]

The prostate is one of the target organs of androgen. This fact is the foundation of the anti-androgen therapy for the treatment of prostatic of cancer as there are many prostatic cancers which show no response to hormone therapy. Since androgen acts via an androgen-androgen receptor complex in cytosol, trials to predict the effectiveness of the anti-androgen therapy for the treatment of prostatic cancers by means of the measurement of androgen receptor (AR) have been done. However some investigators emphasize that the response to hormone therapy and the contents of AR are not necessarily parallel. This discrepancy is probably due to the inaccurate measurement of AR. AR is measured by a radio-receptor-assay method, but it is possible that androgen binding proteins other than AR are also measured by the radioreceptor-assay method. In the human prostatic tissues, there are several androgen binding proteins other than AR. These are mainly testosterone-binding globulin (TeBG) and progesterone-binding protein (PBP). In this study, I attempted to separate and characterize androgen-binding proteins in human prostates. 500 g of benign prostatic hyperplasia (BPH) tissues obtained from patients undergoing retropublic or suprapubic prostatectomy were used. In order to separate these androgen-binding proteins, DEAE-cellulose ion exchange chromatography was used. Prostatic cytosol was applied on the DEAE-cellulose column. Two 3H-R1881 binding peaks were eluted: one was a flow-through fraction (peak I), and the other was an 0.1M KCl eluted fraction (peak II). When human serum was applied to the column, one 3H-DHT binding peak flowed through the column (peak III). It was thought that peak III contained TeBG. In order to ascertain whether AR was composed in peak I or peak II, an inhibition test by various non-radioactive steroids, R1881, DHT, testosterone, progesterone and estradiol was performed. 3H-R1881 binding of peak I was not inhibited by DHT or testosterone, while 3H-R1881 binding of peak II was inhibited by DHT and testosterone. The androgen-binding affinity of the peak I and peak II fraction was also measured using Scatchard's analysis. The dissociation constant of peak I was 6.25 nM, and that of peak II was 0.76 nM. Judging from these measurements the androgen-binding protein of peak II contained a specificity and high affinity to androgen. Consequently it was thought that AR was composed in peak II. Peak II fraction was applied on a Sephadex G200 gel chromatography column. A single androgen binding peak eluted in the void fraction.(ABSTRACT TRUNCATED AT 400 WORDS)

Characterization studies of a rat hepatic cytosolic androgen-binding protein

A rat hepatic cytosolic [3H]methyltrienolone (R1881) binding protein was studied under various conditions. This protein was also compared with the male-specific high capacity--low affinity estrogen-binding protein derived from the same cytosolic fraction. Analysis of the R1881 binding protein in adult (60-85 days old) male rat liver cytosol indicated the presence of a high affinity--low capacity binding site (Kd = 0.3 nM; Bmax = 5.9 fmol/mg) and a lower affinity--higher capacity component (Kd = 10.4 nM; Bmax = 131 fmol/mg). The latter component was eliminated by addition of triamcinolone or cortisol to the assay mixture. Steroid binding to the high affinity R1881 site was specific for testosterone, dihydrotestosterone, androstenedione, and mibolerone, with a moderate specificity to cyproterone acetate, flutamide hydroxide, and estradiol. Saturation studies indicated that these steroids were binding to the same or a similar high affinity component except for flutamide hydroxide which produced nonsaturable displacement. The high affinity site had no specificity for progesterone, diethylstilbestrol, or cortisol. Like the high capacity--low affinity protein, this protein was not present in the immature, adult, or 10-day ovariectomized adult female. However, unlike the high capacity--low affinity protein, it was present in low quantities in the immature male. In addition, castration of the adult for 18 h, 4 days, or 10 days or hypophysectomy for 10-17 days did not have a significant effect on the high affinity component compared with the controls. Testosterone administration to these animals did not alter this protein binding. These studies indicate that a specific, high affinity--low capacity androgen-binding protein exists in rat hepatic cytosol. Furthermore, this protein shows age and sex dependency, but its presence is not affected by altering gonadal or hypophyseal factors in the adult male.

Localization of prostatic basic protein ("probasin") in the rat prostates by use of monoclonal antibody

Isolated nuclei of the rat prostates contain a unique androgen-dependent basic protein, "probasin". Despite that it was hardly detectable in the cytosol centrifugally prepared from the prostates, immunofluorescent histological analysis of whole tissues using monoclonal antibody, which was raised against probasin purified from the nuclei, revealed that probasin was abundantly localized in the lumen and acinal regions of the epithelium, but hardly in the nuclei. Previous extraction of secretory fluid from the prostates caused about 60% decrease in the probasin content of isolated nuclei. These suggest that probasin was originally a secretory component in the prostates, being redistributed from the secretory fluid and granule into nuclei during fractionation of subcellular components.

Comparison of rabbit androgen binding protein with testosterone estradiol binding globulin—I. Physical and chemical properties

Rabbit epididymal androgen binding protein (rbABP) and serum testosterone estradiol binding globulin (rbTeBG) were purified and their physicochemical properties compared. Both proteins bound dihydrotestosterone (DHT) with high affinity. Both contained two components, Heavy (H) and Light (L), and their molecular weights and pI values were comparable. rbABP and rbTeBG were different with regard to their ConA-Sepharose binding property. rbABP was not bound by ConA-Sepharose while rbTeBG was found and retained by this lectin; thus, rbABP and rbTeBG differed in their carbohydrate structure. Peptide mapping on SDS-PAGE indicated that the H components of rbABP and rbTeBG were distinct even though they showed a high degree of homology. By contrast, the L components of these two proteins appeared to be identical. The structure of the steroid binding sites of these two proteins was analyzed by peptide mapping of [1,2(3)H]17 beta hydroxy-androsta-4,6-dien-3-one photoaffinity labeled protein. The size distribution of radioactive peptide fragments generated appeared to be identical for these two proteins. However, the distribution of labeled peptides was slightly different when examined by high pressure liquid chromatography (HPLC). The observations suggest that the differences between rbABP and rbTeBG might reside not only in carbohydrate moieties but also in their amino acid sequences.

Relative cellular distribution of particulate androgen binding between sertoli and germ cells in rat testis

An androgen binding activity with characteristics similar to ABP is present in a particulate fraction (105,000 g pellet) obtained by differential centrifugation of seminiferous tubules, impure Sertoli cells and impure germ cells homogenates. Purification of germ cells through albumin gradients, results in almost a complete loss of androgen binding activity in the purified germ cell suspensions. Furthermore, Sertoli cell enriched testes from 22-, 32- and 40-day old rats showed increases in particulate androgen binding, when compared to matched controls, parallel to increments in the activity of a Sertoli cell marker enzyme (beta-glucuronidase). These results suggest that particulate androgen binding activity is only present in Sertoli cells and this protein may play a role in the compartmentalization of androgens in the testis.

The heterogeneity of rat androgen-binding protein in serum differs from that in testis and epididymis

Fractionation of testicular, epididymal, and serum extracts containing rat androgen-binding protein (rABP) on a Concanavalin A-Sepharose (Con A) column resolved two peaks of immunoreactive protein. The first peak was present in the void volume, and the other was bound by the column and specifically eluted by alpha-methyl-D-glucoside. These two peaks of immunoreactive rABP have been designated form I and form II for the portions of rABP that do not and do bind, respectively, to Concanavalin A. In the course of studying this heterogeneity, we observed that the distribution of the two forms of rABP was the same in the blood and cytosols prepared from testis and epididymis of young rats before the formation of the blood-testis barrier; that is, the ratio of form I to form II ranged from 1:1 to 1:2. Similar heterogeneity was observed in extracts of the reproductive tract from mature animals. However, the blood of adult rats contained reduced amounts of form I relative to form II, so that their ratio was about 1:5. Subsequent studies of infertile rats heterozygous for the Hre gene (Hre/ +), in which total rABP secretion was decreased, and of their normal littermates, indicated that the reduced amount of form I ABP in the sera of mature rats is typical of adult animals regardless of strain or genetic abnormality. The reduced amount of form I relative to form II observed in the blood of adult rats could result from either reduced secretion or increased metabolic clearance of form I in the blood compartment. To distinguish between these possibilities, the blood clearance of the two forms was estimated after orchiectomy. The disappearance rate of form I was not significantly different from that of either form II or unfractionated serum. These results are consistent with reduced release into blood of form I relative to form II rABP rather than increased clearance of form I in adult animals.

The tissue source and cellular control of the apparent size of androgen binding protein (Abp), a mouse salivary protein whose electrophoretic mobility is under the control of sex-limited saliva pattern (Ssp)

Expression of the dominant allele, Ssps, at the Sex-limited saliva pattern locus in mice results in an alteration of the electrophoretic mobility of a mouse salivary protein from the F (fast) to the S (slow) type [Karn, R.C., et al. (1980). Genetics 94:s52; Karn, R.C., et al. (1982). Biochem. Genet. 20:493]. We now demonstrate that the protein affected binds androgen and has a basic heterodimeric structure with the subunits connected by disulfide bridging. It is produced in the submaxillary gland where the alteration takes place. The change in electrophoretic mobility from F to S appears to be primarily the result of an increase in the molecular weight of the larger subunit since the isoelectric point changes very little. We discuss the possible causes of the increase in molecular weight.

Isolation of two genomic sequences encoding the Mr = 14,000 subunit of rat prostatein

Complementary DNAs to rat ventral prostate poly(A) RNA were cloned into pBR322 by the "dG-dC tailing" procedure. Clones containing cDNAs to the mRNAs coding for each of the three subunits of a major secretory protein (prostatein) were identified by hybrid-arrested translation. A 457-nucleotide base pair cDNA (E45) and a portion of a 365-base pair cDNA (E85) were analyzed to determine the composite complete DNA coding sequence for the Mr = 14,000 (C3) subunit of prostatein. A sequence of 12-nucleotide bases (TTTGCTGCTATG) in the signal peptide of C3 was noted to be homologous to signal peptide nucleotide sequences reported in cDNAs coding for the other two prostatein subunits, Mr = 6,000 (C1) and 10,000 (C2). Complementary DNA coding for the C3 subunit was used as a hybridization probe to screen an EcoRI rat genomic DNA library. Two unique 12-kilobase genomic clones, each containing mRNA coding sequences within 2.5-3-kilobase fragments, were identified by restriction enzyme mapping and Southern blot analysis. Restriction enzyme sites within the coding regions of both genes were analogous to the cDNA. Differences in restriction enzyme sites in regions of intervening sequences and flanking DNA established the uniqueness of the two genes. It is suggested that both genes may be transcribed in vivo.

Purification and characterization of a membrane-associated testosterone-binding protein from Pseudomonas testosteroni

A steroid-binding protein, identified in the supernatant generated when membrane vesicles of Pseudomonas testosteroni are produced and harvested by centrifugation, has been purified 49-fold to homogeneity. It has a molecular weight of 30 000-35 000 and it specifically binds the C19 steroids dihydrotestosterone, testosterone, and androstenedione. It is a basic protein with an isoelectric point at pH 7.3. Binding of testosterone exhibited normal saturation kinetics with an affinity constant, Kd, of 3.9 X 10(-8) M. Binding was inhibited by divalent cations, but the sulfhydryl reagents dithiothreitol and mercaptoethanol did not affect activity. It is suggested that this and other membrane-associated steroid-binding proteins concentrate the steroid at the membrane surface before it is transported into the cytoplasm of P. testosteroni.

Assembly, glycosylation, and secretion of the oligomeric rat prostatic binding protein in Xenopus oocytes

Prostatic binding protein (PBP), a hormonally controlled oligomeric glycoprotein secreted by the rat ventral prostate, is composed of three different polypeptide chains, C1, C2, and C3. Microinjection of prostate mRNA into Xenopus laevis oocytes results in the synthesis, processing, and correct assembly of these three components, and also in the export of PBP into the medium. The glycosylation of component C3--the only glycopeptide of PBP--by the oocyte enzymes does not lead to the same result as in the native prostate tissue. The intracellular oocyte component contains an incompletely processed oligomannosyl core unit. Upon secretion this sugar core is further processed, probably at random because the carbohydrate chains attached to the exported C3 molecules are heterogeneous; they are also different from the oligosaccharide unit of authentic C3. However, tunicamycin experiments show that glycosylation is neither a prerequisite for secretion nor for the assembly of PBP, at least in oocytes.

Partial purification and characterization of a membrane-associated steroid-binding protein from Pseudomonas testosteroni

A steroid-binding protein obtained from the supernatant of the final wash from the preparation of membrane vesicles was purified severalfold to near homogeneity. The protein binds C18 and C19 steroids but has the highest affinity for androstenedione (Kd = 1.6 x 10(-10) M). The molecular weight is 51,000 - 58,000. Binding activity is slightly inhibited by Cu2+, Ca2+, and Mg2+ and completely inhibited by Zn2+. The protein has no detectable steroid degradative activity. Analysis of androstenedione binding revealed negative cooperativity of binding for this ligand and may indicate a regulatory function for this protein. It is postulated that this protein binds the steroid after testosterone is converted to androstenedione.

Study of a proline-rich polypeptide bound to the prostatic binding protein of rat ventral prostate

A proline-rich polypeptide is associated with prostatic binding protein, a major androgen-dependent protein described previously in the rat ventral prostate. This polypeptide has been purified. Its molecular weight estimated by gel filtration is about 8500, but a markedly lower value (3300) is obtained by sodium dodecyl sulfate-urea polyacrylamide gel electrophoresis. Isoelectric focusing on thin layer polyacrylamide gels yields two major forms with isoelectric points of, respectively, 7.75 and 7.05. The amino acid composition of proline-rich polypeptide is characterized by a high (19.5%) proline content and its NH2-terminal amino acid is glycine. Like prostatic binding protein, proline-rich polypeptide is a characteristic component of the rat ventral prostate and localized primarily in the intraluminal secretion of this gland. In intact adult male rats the cytosol of a whole gland contains 0.70 +/- 0.15 (S.D.) mg of the polypeptide, as measured by radial immunodiffusion or 2.6 +/- 0.5% of (S.D.) of the total protein. This amount decreases gradually after castration and becomes undetectable after 8 days. Androgen treatment, on the other hand, results in a rapid stimulation, while estradiol and progesterone are ineffective. Proline-rich polypeptide is markedly more androgen-dependent than prostatic binding protein, and promises to be an interesting end point for studies on the mechanism of action of androgens.

Purification and characterization of androgen binding protein from rabbit epididymis

A method for the purification of androgen binding protein (ABP) from the rabbit epididymis is presented. Epididymal extracts were submitted to sequential ammonium sulfate precipitation, androgen affinity chromatography, concanavalin A (Con A) affinity chromatography, and preparative polyacrylamide gel electrophoresis. Since the blood protein testosterone-estradiol binding globulin (TeBG) was a possible component of the epididymal extract, ABP was differentiated and separated from TeBG by affinity chromatography on Con A-Sepharose since the latter protein was shown to be completely absorbed by the lectin while the former was not. The final product was shown to be pure by polyacrylamide gel electrophoresis. Electrophoresis in the presence of sodium dodecyl sulfate revealed that ABP is comprised of subunits.

Sertoli cells of adult rats in vitro. III. Purification of androgen-binding protein from the culture medium

A method giving a high yield for the isolation and purification of the androgen-binding protein (ABP) from the nutritional medium of cultured cells from adult rats is described.

Structural studies on rat prostatic binding protein. The primary structure of component C1 from subunit F

The amino acid sequence of component C1, the polypeptide specific for subunit F of prostatic binding protein, the major secretory glycoprotein of the rat ventral prostate, has been determined. Its structure was established using the manual Edman degradation on the intact protein and on the most relevant fragments isolated from trypsin, chymotrypsin, thermolysin and Staphylococcus aureus protease digests of the 14C-labelled S-carboxamidomethylated component C1. Component C1 contains 88 amino acids corresponding to a molecular weight of 10246. It is an acidic polypeptide due to the presence of 17 acidic residues; its three cysteine residues are almost symmetrically distributed over the peptide chain. Highly polar regions are found in positions 17-27 and 37-47, while the C-terminal part of the molecule contains two hydrophobic segments.

Prostate alpha-protein. Isolation and characterization of the polypeptide components and cholesterol binding

alpha-Protein, a major glycoprotein in the cytosol fraction of rat ventral prostate, has a molecular weight of about 50,000 and can be dissociated, by sodium dodecyl sulfate, into two different subunits (A and B). alpha-Protein has three different polypeptide components with apparent molecular weights of 10,000 (I), 14,000 (II), and 15,000 (III). These components were purified to homogeneity and their amino acid compositions were determined. Subunit A is composed of Components I and III, whereas subunit B is composed of Components II and III. Carbohydrate was detectable only on Component III. Component III isolated from subunit A and Component III isolated from subunit B appear to be identical. The purified alpha-protein contains 0.7-1 mol of cholesterol/mol of protein. If cholesterol was removed by acetone, about 1 mol of 5 alpha-dihydrotestosterone or pregnenolone could bind to 1 mol of alpha-protein. In the presence of 2 mM ZnCl2, alpha-protein can form dimers and tetramers. In cell-free systems, alpha-protein can inhibit binding of the androgen-receptor complex to nuclear chromatin and also can promote the release of the complex already bound to chromatin. This effect is due to polypeptide Component I.

Prostate alpha-protein. Complete amino acid sequence of the component that inhibits nuclear retention of the androgen-receptor complex

The amino acid sequence of Component I of alpha-protein, a glutamic acid-rich protein, is presented. Component I is a single chain polypeptide which consists of 88 amino acid residues with a molecular weight of 10,191. Component I has the amino acid composition Lys6, His, Arg2, Cys3, Asp5, Asn2, Thr3, Ser4, Glu13, Gln3, Pro3, Gly2, Ala6, Val9, Met4, Ile4, Leu8, Tyr6, Phe3, Trp, with serine and asparagine as NH2(-) and COOH-terminal amino acids, respectively. Automated sequences analysis of the whole protein, as well as characterization of the peptides obtained from trypsin, chymotrypsin, and staphylococcal protease digestion and cyanogen bromide treatment, led to the elucidation of the complete primary structure of this protein.

Origin of the heavy and light protomers of androgen-binding protein from the rat testis

Androgen-binding protein (ABP) isolated from rat epididymides by androgen affinity chromatography is a dimer with a native molecular weight of 85,000. When fractionated on sodium dodecyl sulfate gels two components were identified which were present in a 3:1 ratio; these were designated heavy (H) and light (L) (Mr of 45,000 and 41,000), respectively. The fact that H and L both have steroid binding sites and that they can be cross-linked suggests that both are protomers of native ABP. NH2-terminal analysis, amino acid analysis, and peptide maps suggest an extensive homology between H and L. In addition, peptide maps of H and L photolabeled with delta 6-[3H]testosterone suggest that the binding sites on these protomers are identical. ABP was also purified 33,800-fold from testes. The H and L protomers from this preparation were identical with those from the epididymides as judged by peptide maps. In addition, [35S]methionine was incorporated into the H and L synthesized by Sertoli cells in the same 3:1 ratio as in highly purified ABP from testis and epididymis. These observations suggest that L is not derived from H following secretion. Selective incorporation of [3H] fucose into the H protomer suggests that differences in carbohydrate composition account for at least part of the difference between H and L. These results support the conclusion that native ABP is composed of two kinds of protomers which exist in a ratio of 3:1. These protomers are similar polypeptides that differ partly in carbohydrate composition.

Membrane-associated steroid-binding proteins of Pseudomonas testosteroni

Previous studies have established the presence of periplasmic steroid-binding proteins in induced Pseudomonas testosteroni. This study reports the presence of two additional steroid-binding proteins which can be released from the cytoplasmic membrane during preparation of membrane vesicles. These two proteins differ from each other and from the periplasmic protein in some of their characteristics and steroid specificity, and appear to be distinct from the two membrane-bound steroid dehydrogenases, 3 beta and 17 beta-hydroxysteroid dehydrogenase and 1-ene-dehydrogenase.

Seminal fluid androgen binding protein

The following study was undertaken to determine the presence of an androgen binding protein (ABP) in the ejaculate. Seminal fluid was obtained from ten fertile subjects. Sperm counts ranged from 20 x 106/cc to 80 x 106/cc. Each sample was preincubated with tritiated dihydrotestosterone (DHT) and examined by polyacrylamide gel electrophoresis (PAGE). Second, after preincubation of the samples with tritiated DHT, the samples were mixed with Concanavalin-A bound to sepharose-D (C-S) and the supernate separated and counted. Finally, saturation analysis of the samples using dextran-coated charcoal for separation and counted. Finally, saturation analysis of the samples using dextran-coated charcoal for separation was performed and Scatchard analysis was used to determine the concentration of ABP present. PAGE demonstrated ABP in seven of ten samples studied. The bound counts of DHT were removed by C-S. The concentrations of ABP ranged from 0.132 to 0.468 nanomoles ABP/dl semen. These data indicate there is an ABP in seminal fluid similar to that from the Sertoli cell.

Androgen-binding protein. Purification from rat epididymis, characterization, and immunocytochemical localization

Androgen-binding protein (ABP) was purified from caput epididymis of the rat by sequential chromatography on DEAE-Sepharose, hydroxylapatite, dihydrotestosterone-17 beta-hemisuccinyl-1,6-diaminohexane-Sepharose, and Sephadex G-150. The final product migrated as a single band corresponding to a peak of protein-bound [3H]dihydrotestosterone on polyacrylamide gel electrophoresis. A molecular weight of 100,000 was estimated by sedimentation equilibrium. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, subunits of Mr = 47,000 and 41,000 were observed. Amino acid analysis indicated ABP to be rich in leucine while nonpolar aminoacids totaled only 51%. Its carbohydrate content is 25%. Antibodies to purified ABP were raised in a rabbit and evaluated by immunodiffusion, immunoelectrophoresis, binding inhibition, radioimmunoassay, and immunocytochemistry. Immunoperoxidase staining localized ABP in the basal and adluminal regions of seminiferous tubules of rat testis and in secretory granules of cultured Sertoli cells. In principal cells of caput epididymis, ABP is concentrated in the supranuclear region known to contain morphological specializations for absorption. These immunocytochemical results confirm that ABP synthesized and secreted by Sertoli cells in the testis is transported to the epididymal duct via testicular fluid and is taken up by epithelial cells of the proximal segments.

Heterogeneity in end-terminal sugars of rabbit and rat androgen binding protein (ABP)

The interaction between rabbit and rat androgen binding protein (ABP) and rabbit serum testosterone binding globulin (TeBG) with concanavalin A (Con A) was studied using affinity chromatography on Con A-Sepharose 4 B columns. When partly purified rat ABP, equilibrated with [3H]5 alpha-dihydrotesterone [3H]DHT was applied to Con A-Sepharose columns, approximately 50% of the ABP was retained by the column, whereas the remaining was eluted with the break-through protein fraction. A similar picture was found using partly purified rabbit ABP, or crude rabbit rete testis fluid. These studies indicate that both rat and rabbit ABP are glycoproteins, showing heterogeneity in their end-terminal sugars. When partly purified rabbit TeBG was examined by Con A-Sepharose affinity chromatography, the TeBG was completely retained by the column. The different elution patterns between rabbit ABP and rabbit TeBG indicate that these proteins, although showing identical physico-chemical and immunological properties (Weddington et al. 1975a,b), possess differences in their carbohydrate content.

Biochemical homology between rat dorsal prostate and coagulating gland. Purification of a major androgen-induced protein

The anatomically distinct organs, rat dorsal prostate and coagulating gland, were found to display remarkable homology in protein composition, including two major androgen-dependent secretory proteins, referred to as dorsal proteins I and II. Dorsal protein I has been purified and found to be a dimer composed of two identical subunits with sedimentation coefficient 4.6 S, Stokes radium 32 A, and Mr = 71,000 (62,000 by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis). This dimer (6.8 S, 46 A, Mr = 150,000) dissociates at high ionic strength and can be partially reconstituted by removal of salt. Dorsal protein I is a basic protein (pI 9) with high lysine content and binds to phosphocellulose but not to DEAE-Sepharose. Schiff's staining shows that it contains carbohydrate. Quantitative rocket immunoelectrophoresis using a rabbit antiserum indicates dorsal protein I is produced only in dorsal prostate and coagulating gland. The protein constitutes approximately 25% of total cytosol protein in both organs, yet makes up on 5% of coagulating gland luminal fluid and ejaculated seminal fluid. It was not detected in the rat dorsal prostate tumor (Dunning R3327H). Dorsal protein II is a larger protein (Mr = 80,000 by SDS gel electrophoresis) with higher carbohydrate content. Under nondenaturing conditions, it has a Stokes radius of > 200 A, corresponding to Mr of > 300,000. Dorsal protein II represents a smaller proportion of total cytosol protein than does dorsal protein I, yet is the predominant protein of coagulating gland fluid. The proteins will be useful probes for studies on androgen regulation of specific gene expression and prostatic secretory mechanisms.

Purification and characterization of androgen binding protein from the rat epididymis

Androgen binding protein (ABP) was purified from rat epididymides by sequential ammonium sulfate precipitation, affinity chromatography, gel filtration, and DEAE ion exchange chromatography. The column matrix formed by coupling dihydrotestosterone-17 alpha-(hexanoic acidY to agarose via diisopropylamine was stable during the extensive washing required following application of crude tissue extracts to the affinity matrix. In addition, when used under the optimal conditions, the column produced a 1600-fold purified in a single step. Apparent homogeneity of the final product was shown by polyacrylamide gel electrophoresis, sedimentation equilibrium, and constant specific activity across the peak of the final chromatograph. The molecular weight determined by sedimentation equilibrium at pH 7.4 was 85 000. By contrast, the molecular weight determined by sedimentation equilibrium in guanidine.HCl and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis was approximately one-half that of the native protein, suggesting that suggesting that ABP is comprised of subunits.