Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P56851 (epididymal)
 11,273 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Clusterin is a heterodimeric glycoprotein synthesized and secreted by rat Sertoli cells and epididymal epithelium. The goal of this study was to determine the presence of clusterin in the luminal fluid of the cauda epididymides and its association with the membranes of developing spermatozoa in the presence and absence of androgen. We have previously demonstrated by two-dimensional (2-D) Western blot probing for clusterin that in epididymal fluid the amounts of clusterin were: caput greater than corpus greater than cauda. Luminal fluid from cauda epididymides was collected from control and orchiectomized rats (6 and 12 days) and orchiectomized animals that received testosterone implants. Equal volumes of fluid were analyzed by 2-D Western blot probing for clusterin. Following orchiectomy, there was an increase in clusterin in the luminal fluid after 6 days and maximal amount after 12 days compared with control cauda fluid. Orchiectomized animals which received testosterone treatment showed levels of clusterin comparable to that of controls. Serum clusterin was detected in fluid of orchiectomized animals with and without testosterone. Western blots of cauda sperm membrane extracts of control animals and orchiectomized animals treated with testosterone had a very low level of epididymal clusterin, whereas extracts collected from orchiectomized animals revealed high levels of clusterin. We suggest that, in the normal animal, clusterin is secreted into the lumen of the proximal epididymis where it binds to the sperm membrane. In the distal epididymis, clusterin dissociates from sperm and is processed (proteolysis/endocytosis). We hypothesize that, in the absence of androgen, the processing and regulation of clusterin is disrupted.
 ...
PMID:Clusterin (SGP-2) in epididymal luminal fluid and its association with epididymal spermatozoa in androgen-deprived rats. 151 50

Clusterin (sulfated glycoprotein-2) is a heterodimeric glycoprotein synthesized and secreted by rat Sertoli cells. An antigenically similar form is synthesized and secreted by the epididymis. The goal of this study was to define the epididymal regions in which clusterin is present and the regions in which clusterin is secreted and interacts with developing spermatozoa. Seminiferous tubule (STF), caput, corpus, and cauda fluids were collected by micropuncture and/or microperfusion and two-dimensional Western blot analysis was performed with a polyclonal antibody directed against Sertoli cell clusterin. Clusterin was found in both STF and epididymal fluid. STF contained predominantly the clusterin heavy chain (45 kd); however, a 70 Kd heterodimer was present under nonreducing conditions. Two subunits of clusterin with lower molecular weights (41 kd, heavy chain; 32 kd, light chain) and higher isoelectric points were present in the luminal fluid of all epididymal regions. The intraluminal levels of the heavy and light chains decreased from caput to cauda. Analysis by two-dimensional gel electrophoresis of proteins secreted directly into the epididymal luminal fluid revealed that clusterin was secreted by caput epithelium and not by the corpus and cauda epithelium. Western blots of membrane extracts from testicular, caput, and cauda spermatozoa revealed that testicular clusterin was associated with testicular sperm and epididymal clusterin with predominantly caput sperm. Our findings suggest that clusterin is secreted into the caput epididymal lumen, where it binds to sperm and then dissociates from sperm to be endocytosed by cells of the distal epididymal epithelium.
 ...
PMID:In vivo secretion and association of clusterin (SGP-2) in luminal fluid with spermatozoa in the rat testis and epididymis. 178 89

The localization of sulfated glycoprotein-2 (clusterin; SGP-2) was investigated in the rete testis, efferent ducts, and epididymis of the rat using light (LM) and electron (EM) microscope immunocytochemistry. At the LM level, the epithelial cells of the rete testis and efferent ducts demonstrated an intense immunoperoxidase reaction over their apical and supranuclear regions, and sperm in the lumen of the efferent ducts were unreactive. In the EM, gold particles were found exclusively over the endocytic apparatus of these cells. In the proximal area of the epididymal initial segment, an insignificant immunostaining of epithelial cells and sperm was observed. However, the distal area of the initial segment showed a moderate staining over the epithelial principal cells and sperm, while in the intermediate zone of the epididymis a stronger reaction was observed over these cells. The strongest immunoperoxidase reaction was noted in the caput epididymidis, where it formed a distinct mottled pattern. Thus, while some principal cells were intensely stained, others were moderately or weakly stained; a few were completely unreactive. In the corpus and cauda epididymidis, the staining pattern was similar but not as intense. In the EM, only the secretory apparatus of these cells was found to be immunolabeled with gold particles. Sperm in the lumen of these different regions were also labeled. The epithelial clear cells were unreactive throughout the epididymis. Northern blot analysis substantiated these results and showed the presence of highest levels of SGP-2 mRNA in the caput epididymidis, especially in its proximal area, whereas increasingly lower levels were found in the corpus and cauda epididymidis. In summary, these results suggest that testicular SGP-2 dissociates from the sperm during passage through the rete testis and efferent ducts, where it is endocytosed by the epithelial cells lining these regions. In the epididymis, it is replaced by an epididymal SGP-2 that is secreted by the epithelial principal cells of the epididymis. Furthermore, in the epididymis, the principal cells appear to be in different functional states with respect to the secretion of epididymal SGP-2 within a given region of the duct as well as along the epididymal duct.
 ...
PMID:Role of epithelial cells of the male excurrent duct system of the rat in the endocytosis or secretion of sulfated glycoprotein-2 (clusterin). 187 86

Nucleotide sequence analysis of the complimentary DNAs (cDNA) and N-terminal amino acid sequence analysis have shown that clusterin is equivalent to sulfated glycoprotein-2 (SGP-2), testosterone-repressed prostate protein-2 (TRPP-2), and androgen-repressed protein (ARP) in the rat, as well as serum/seminal plasma protein, SP-40,40, in the human. In view of its widespread presence in various species, a specific RIA was established to quantify the tissue distribution of this protein. Rat clusterin is present in almost all organ tissues examined, including testis, epididymis, serum, liver, prostate, seminal vesicles, and uterus. Displacement curves generated using cytosols prepared from these organs were parallel to those obtained using purified rat clusterin and crude Sertoli cell-enriched culture medium. Immunoreactive clusterin was also visualized in these organ extracts by immunoblots. Studies on the tissue distribution of immunoreactive clusterin using RIA revealed that the concentration of clusterin in the epididymis of adult rats was 6- and 10-fold higher than that in the serum and testis, respectively and is 50- to 100-fold higher in the liver, spleen, kidney, brain, ventral prostate, seminal vesicles, and uterus. A study of the distribution of clusterin in various compartments of the epididymis indicated its concentration in the caput epididymis was almost 3-fold higher than that in the corpus and cauda epididymis. After orchiectomy, the concentrations of clusterin in the ventral prostate and seminal vesicles increased as much as 100- and 10-fold and peaked at day 4 after surgery, respectively; daily injection of dihydrotestosterone (DHT) beginning at day 3 after orchiectomy reduced the concentrations of clusterin and restored them to a normal level. A different pattern was noted in the epididymis after orchiectomy; the concentration of clusterin in the caput epididymis decreased with time; however, daily injection of DHT beginning at day 3 increased the caput epididymal clusterin concentration and restored it to a normal level. The concentration of clusterin was not altered in the corpus or cauda epididymis after castration and/or DHT administration. Also, the serum and liver clusterin levels did not change with time after orchiectomy. These observations suggest that clusterin will be a valuable marker to monitor the diverse effects of androgen withdrawal in the male reproductive tract. We conclude that clusterin may be a multifunctional protein in view of its broad tissue distribution and association with numerous physiological and pathological conditions.
 ...
PMID:Diverse secretory patterns of clusterin by epididymis and prostate/seminal vesicles undergoing cell regression after orchiectomy. 235 Nov 5

Clusterin is a protein present in the rete testis fluid of the ram that elicits aggregation of erythrocytes and Sertoli cells in vitro. In view of its possible biologic function in relation to cell-cell interaction in the testis, we isolated this protein from ram rete testis fluid using sequential high-performance liquid chromatography columns and performed a detailed physicochemical characterization. This protein consists of two molecular variants designated form I and form II clusterin. Each form of clusterin consists of two subunits with an apparent molecular weight of 40,000. It is of note that the two subunits have no homology in their N-terminal amino acid sequences. However, the N-terminal amino acid pairs of the two subunits derived for the two forms of clusterin are identical. Using o-phthalaldehyde to block the Lys residue at the fourth amino acid pair from the N-terminus which leaves the Pro residue free for subsequent Edman degradation, we have deduced the N-terminal sequence of each of the two subunits for form I clusterin. Comparison of the NH2-terminal sequences of the two subunits of clusterin with the release 10.0 of the protein sequence data base of the Protein Identification Resource indicated no homology between either of the subunits of clusterin and any of the known proteins in the data base. A highly specific radioimmunoassay developed for clusterin was used to measure its concentrations in the fluids of the rete testis and cauda epididymis. Since a significant amount of immunoreactive clusterin was found in serum, the protein was partially purified from this source by immunoaffinity chromatography. Immunoreactive serum clusterin was smaller than the testicular clusterin (Mr 37,000 vs 40,000), but both proteins share common epitopes as demonstrated by radioimmunoassay and immunoblots. However, serum clusterin does not possess the biologic activity of the testicular clusterin in that it does not elicit cell aggregation in vitro. It is of note that deglycosylation of testicular clusterin can also eliminate this in vitro biologic activity, suggesting that the serum clusterin might be a deglycosylated form of the testicular protein and the carbohydrate core plays an important role in determining the cell aggregation activity. Studies on the distribution of this protein in the reproductive compartment indicate that it is highly concentrated in the rete testis and the cauda epididymal fluids. This suggests that this protein might have some important functions in the reproductive tract.
 ...
PMID:Structural analysis of clusterin and its subunits in ram rete testis fluid. 341 74

Clusterin, a glycoprotein that elicits cell aggregation, has previously been isolated from ram rete testis fluid, and has been partially characterized. In experiments reported, we have used monoclonal antibodies against clusterin in combination with indirect immunofluorescence microscopy to investigate the distribution of clusterin in the adult ram testis, rete testis, and excurrent ducts. Tissue blocks (5 mm3) were fixed in periodate/lysine/paraformaldehyde containing 0.1% glutaraldehyde and, after embedding, 5-microM sections were prepared for immunolocalization. In the testis, 2 basic patterns were observed: 1) strong to moderate staining for clusterin in the adluminal region with little staining in the basal region of the seminiferous epithelium and germinal cells; and 2) moderate staining throughout the seminiferous epithelium between germinal cells. In the rete testis, strong clusterin staining was localized intracellularly in the rete epithelial cells, most often associated with the luminal surface. In the epididymis, intracellular clusterin was localized in some principal cells of the caput epididymidis. The luminal surfaces and spermatozoa within the lumen were strongly positive. In the vas deferens, clusterin staining was associated with the luminal surface only. The presence of clusterin was clearly detected in unwashed isolated epididymal spermatozoa, but not in spermatozoa washed with phosphate-buffered saline containing 0.05% Tween 20.
 ...
PMID:Immunolocalization of clusterin in the ram testis, rete testis, and excurrent ducts. 390 51

The mammalian epididymis is the site where spermatozoa are matured and then stored. Though many studies have described epididymal functions and their regulation, little is known about how aging affects this tissue. The Brown Norway rat, which does not show the many age-related pathologies common to other rat strains, was used as a model to study aging of the epididymis. The present study was designed to determine the effect of aging on the mRNA levels for selected markers of epididymal function. Brown Norway rats ranging in age from 6 to 30 months were examined at 6-month intervals; epididymides were sectioned into caput-corpus and cauda regions. Relative mRNA concentrations were assessed using Northern blot analysis and specific cDNAs for the rat 5 alpha-reductase isozymes, types 1 and 2; proenkephalin; the androgen receptor; epididymal proteins B/C and D/E; and sulfated glycoprotein-2 (SGP-2, clusterin). Northern blots were quantitated by densitometric scanning. In the caput-corpus epididymidis, 5 alpha-reductase type 1 and type 2 mRNA levels decreased significantly by 43% and 33%, respectively, between 6 and 12 months and by 64% and 40%, respectively, between 6 and 30 months. No significant change, however, was found in the expression of the 5 alpha-reductase mRNAs in the cauda epididymidis. Interestingly, proenkephalin mRNA was only detected in the caput-corpus epididymidis of 6-month-old rats. In marked contrast to the 5 alpha-reductase isozymes and proenkephalin, no significant age-related changes were observed in the mRNA levels for the androgen receptor, protein B/C, or protein D/E. No age-related changes in mRNA expression for SGP-2 occurred in the caput-corpus epididymidis. However, in the cauda epididymidis, SGP-2 mRNA levels rose by twofold between 6 and 18 months and then decreased sharply by 75% between 18 and 30 months. We conclude that as the epididymis ages, the expression of genes for certain specific markers of epididymal function is affected in a region-specific manner. Further, the decrease in the concentrations of the mRNAs for the 5 alpha-reductase isozymes and proenkephalin in the epididymis between 6 and 12 months is thus far the earliest marker for aging in the male reproductive tract of the Brown Norway rat.
 ...
PMID:Gene expression in the aging brown Norway rat epididymis. 755 40

It is well established that the epididymis is the site where spermatozoa are matured and stored, but our understanding of the regulation of epididymal epithelium functions and their effects on spermatozoa is still fairly limited. The most active regulator of epididymal functions seems to be dihydrotestosterone, the 5 alpha-reduced metabolite of testosterone. Our laboratory has focused on the regulation of 5 alpha-reductase, with studies encompassing its messenger RNA, protein and enzyme activity. We have also investigated the hormonal regulation and distribution of other specific key proteins found in epididymal epithelial cells that play critical roles in the function of these cells. These proteins include clusterin or sulfated glycoprotein-2 and the glutathione S-transferases (GST). Using complementary experimental approaches, including orchidectomy and hormonal replacement, efferent duct ligation, and developmental studies, we have established that 5 alpha-reductase enzyme activity is present in both nuclear and microsomal fractions; the nuclear enzyme appears almost exclusively in the initial segment of the epididymis. In addition, 5 alpha-reductase activity and the mRNAs for both the type 1 and type 2 form of the enzyme are regulated differentially with respect to age and site within the epididymis. Immunolocalization of the protein has revealed that it is located in principal cells and that its subcellular location is dependent on the region of the epididymis. These results indicate that there is both transcriptional and post-transcriptional regulation of the expression of 5 alpha-reductase. Clusterin is a hydrophobic protein secreted by Sertoli cells and found in high concentration in the epididymis. This glycoprotein is expressed at its highest levels in the initial segment and caput epididymidis and at very low levels in the corpus and cauda epididymidis of the intact rat, and it exhibits a novel pattern of androgen regulation. In the areas of highest expression, there is no androgen dependence; however, orchidectomy causes a dramatic increase in the message for clusterin, which is suppressible by androgens in the segments where expression is normally lowest. The GSTs are a family of enzymes thought to play a key role in detoxification. Members of the GST family are expressed in a region-dependent manner along the rat epididymis. We have found that the localization of one member of this enzyme family, GST P, or subunit Yp, is selective for basal cells in the corpus and cauda epididymidis.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:Regulation of epididymal epithelial cell functions. 771 Nov 92

In vivo microperifusion and micropuncture were used to study tubule protein synthesis and proluminal secretion by the male reproductive tract in vivo. Seminiferous and caput and cauda epididymal tubules were perifused for 3 h. with [35S]-methionine. Perifused interstitial fluid (IF), lumen fluid (LF), and tubule extract (TE) were collected. Proteins were separated by SDS-PAGE, and autoradiograms were developed. Trichloroacetic acid precipitable proteins in each fluid were determined and a protein synthesis index (PSI) was calculated. PSI values demonstrated that the cauda epididymis synthesized less protein in vivo than did either seminiferous or caput tubules. Seminiferous tubules synthesized and secreted into the tubule lumen a relatively constant panel of proteins. Epididymal tubules synthesized and secreted proteins in a region-specific manner. In the caput epididymis the most prominent secreted bands were consistent with the heavy and light chains of epididymal clusterin. In the cauda epididymis, the most prominent synthesized and secreted protein was a 25 kDa protein consistent with the protein D. The above approach to studying protein synthesis and secretion will allow direct study of the physiological and pathophysiological effects on this important epithelial function in vivo.
 ...
PMID:Assessment of protein synthesis and secretion by rat seminiferous and epididymal tubules in vivo. 799 57

Clusterin, also known as sulphated glycoprotein-2 or testosterone-repressed prostate message-2, is a ubiquitous protein found in a variety of tissues and species. In the reproductive tract of the male rat, clusterin is regulated in a complex age-dependent and cell-specific manner. It is expressed at high levels in the epididymis and testis and at very low levels in the prostate under basal conditions. The expression of this gene in the prostate and seminal vesicles is associated with androgen withdrawal, while in the testis clusterin mRNA is repressed by cyclic AMP (cAMP). To understand the mechanisms that control the expression of the clusterin gene better, we isolated and characterized the gene encoding rat clusterin, and analysed its cytosine methylation pattern in various tissues. Several putative regulatory DNA elements were identified, including a consensus AP-1 site in the 5' flanking region. Two AP-1 sites and two transforming growth factor-beta inhibitory elements, one AP-2 site and eight half-sites for glucocorticoid/androgen response elements were found within the first intron, and one cAMP response element was found in the first exon. The cytosine methylation pattern indicated that testicular or epididymal DNA in the rat is hypomethylated in the region between positions -534 and -99 of the clusterin gene, when compared with tissues with lower levels of expression such as prostate as well as liver, lung, kidney and spleen.
 ...
PMID:Regulators for the rat clusterin gene: DNA methylation and cis-acting regulatory elements. 799 55


1 2 3 4 Next >>