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)

Some of the acute actions of insulin may be mediated by an enzyme-modulating inositol phosphate glycan, produced by the insulin-sensitive hydrolysis of a glycosyl phosphatidylinositol that is structurally similar to a membrane protein anchor. An inositol glycan fragment from the structurally characterized Trypanosoma brucei variant surface glycoprotein glycosyl phosphatidylinositol anchor inhibits isoproterenol-stimulated lipolysis in intact rat epididymal adipocytes in a manner mechanistically similar to that of insulin. To explore these effects in more detail, we evaluated the effects of this glycan on protein phosphorylation. Isoproterenol stimulates the phosphorylation of a 70-kilodalton (kDa) protein in these cells. Like insulin, the glycan fragment specifically attenuates the phosphorylation state of the phosphoprotein. In purified adipocyte cytosol, the glycan stimulates the dephosphorylation on serine residues of a 70-kDa protein in a time- and dose-dependent fashion. The glycan-dependent dephosphorylation of the 70-kDa phosphoprotein is unaffected by addition of trifluoroperazine, an inhibitor of serine/threonine phosphatase-2B, but is blocked by the addition of okadaic acid, an inhibitor of serine/threonine phosphatase-1 and -2A. The differential sensitivities of this dephosphorylation reaction to polycations, which activate phosphatase-2A, and phosphorylated inhibitor 1, which blocks phosphatase-1, suggest that dephosphorylation of the 70-kDa protein results from the specific activation of a type 1 serine/threonine phosphatase in adipocytes, providing a mechanistic basis for the insulin-mimetic effects of the inositol glycan.
 ...
PMID:An inositol phosphate glycan derived from a Trypanosoma brucei glycosyl phosphatidylinositol promotes protein dephosphorylation in rat epididymal adipocytes. 795 8

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

The binding of N-acetyl-beta-D-glucosaminidase from rat epididymal fluid to the surface of spermatozoa from the cauda epididymis was measured in the presence of sugars, its phosphorylated derivatives, or after treatment of the cells or the enzyme with agents that alter the integrity of proteins or carbohydrates. The binding was saturable, with a Kd in the nanomolar range, was inhibited with phosphorylated derivates of fructose, and did not depend on Ca2+, showing that it is different from the mannose 6-P-recognizing system existing in other tissues for this and other acid hydrolases. Treatment of the cells with sodium periodate or trypsin inhibited the binding, showing that a glycoprotein of the plasmalemma is involved in the affinity site. Fructose or phosphorylated derivates were not detected in the proteins of the epididymal fluid with HPLC. However, with the method used, the presence of these compounds cannot be ruled out, if among the proteins of the fluid there are only a small number of acid hydrolases containing this sugar.
 ...
PMID:Affinity sites for N-acetyl-beta-D-glucosaminidase on the surface of rat epididymal spermatozoa. 800 7

Recently, a new head-to-head sperm association was described in the rat during epididymal transit. This association was called a rosette and a filamentous and PAS-positive material was also described joining the sperm heads. The beginning of rosette formation in the epididymis and the linking material between heads have remained unclear. Epididymides of adult rats were fixed by vascular perfusion and thin sections of the principal regions were studied by transmission electron microscopy (TEM). The first evidence of rosette formation was observed in the distal corpus. Rosettes were isolated from the distal corpus and processed for immunogold and immunofluorescence microscopy to detect an epididymal glycoprotein called DE. This glycoprotein is secreted by the corpus epididymis and appears to be involved in sperm maturation. Colloidal gold marks and fluorescence were observed in the linking material between the sperm heads. The results presented here show that rosettes begin to appear following the sites of DE secretion and permit us to postulate that DE is involved in rosette formation and constitutes another example of gamete-epididymal interaction.
 ...
PMID:Epididymal glycoprotein involved in rat sperm association. 804 64

Sperm surface beta 1,4-galactosyltransferase (GalTase) mediates fertilization in mice by binding to specific O-linked oligosaccharide ligands on the egg coat glycoprotein ZP3. Before binding the egg, sperm GalTase is masked by epididymally derived glycosides that are shed from the sperm surface during capacitation. After binding the egg, sperm-bound oligosaccharides on ZP3 induce the acrosome reaction by receptor aggregation, presumably involving GalTase. In this study, we asked how increasing the levels of sperm surface GalTase would affect sperm-egg interactions using transgenic mice that overexpress GalTase under the control of a heterologous promoter. GalTase expression was elevated in many tissues in adult transgenic animals, including testis. Sperm from transgenic males had approximately six times the wild-type level of surface GalTase protein, which was localized appropriately on the sperm head as revealed by indirect immunofluorescence. As expected, sperm from transgenic mice bound more radiolabeled ZP3 than did wild-type sperm. However, sperm from transgenic animals were relatively unable to bind eggs, as compared to sperm from wild-type animals. The mechanistic basis for the reduced egg-binding ability of transgenic sperm was attributed to alterations in two GalTase-dependent events. First, transgenic sperm that overexpress surface GalTase bound more epididymal glycoside substrates than did sperm from wild-type mice, thus masking GalTase and preventing it from interacting with its zona pellucida ligand. Second, those sperm from transgenic mice that were able to bind the zona pellucida were hypersensitive to ZP3, such that they underwent precocious acrosome reactions and bound to eggs more tenuously than did wild-type sperm. These results demonstrate that sperm-egg binding requires an optimal, rather than maximal, level of surface GalTase expression, since increasing this level decreases sperm reproductive efficiency both before and after egg binding. Although sperm GalTase is required for fertilization by serving as a receptor for the egg zona pellucida, excess surface GalTase is counterproductive to successful sperm-egg binding.
 ...
PMID:Overexpressing sperm surface beta 1,4-galactosyltransferase in transgenic mice affects multiple aspects of sperm-egg interactions. 808 87

The principal galactose oxidase/NaB[3H]4-labeled membrane protein of rat caudal epididymal spermatozoa was isolated by hydrophobic interaction chromatography. The protein is released from the membrane by the action of phosphatidylinositol specific phospholipase C, and thereby its properties are transformed from those of a protein anchored to the hydrophobic membrane to those of a hydrophilic solution protein. Because it is the only membrane-associated protein released by the enzyme which did not absorb to a propylaspartate resin, a simple, single step purification procedure was devised. Although the amino terminus of the protein is blocked to Edman degradation, the majority of the protein structure was determined from a series of tryptic peptides and from limited acid hydrolysis. Approximately 65% of the protein mass is carbohydrate which is primarily attached through O-glycosidic bonds to the 18 threonines. The molecular weight of the glycoprotein was estimated to be 16,600, considerably smaller than the M(r) = 26,000 to 37,000 previously determined by gel electrophoresis. The anomalous electrophoretic behavior is undoubtedly due to the large percentage of carbohydrate. The distribution of carbohydrate on the protein side chains suggests the protein may form a positively charged, specialized scaffolding for the presentation of the carbohydrate moieties. Because the appearance of the ability to label the protein with galactose oxidase is correlated with sperm maturation in the epididymis, the glycoprotein structures may be an important component in the fertilization process. The combination of linkage by glycosylphosphatidylinositol and low molecular weight mucin-like structure indicates this may be a member of a new class of membrane proteins.
 ...
PMID:Characterization of a cell surface glycoprotein associated with maturation of rat spermatozoa. 812 26

Monoclonal antibody 4E9, which was raised against a partially purified detergent extract of rat caudal epididymal sperm, recognizes the tail of sperm from the cauda, but not from caput epididymidis, as well as epithelial cells in a restricted region of the distal caput/corpus epididymidis and proteins in epididymal fluid from corpus and cauda epididymidis. The antigen is apparently a glycoprotein, since it is retained on a Ricinus communis agglutinin I lectin column. Epididymal fluid antigens have apparent M(rs) of 38-26 kD, whereas the membrane-associated form of the molecule has an M(r) of 26 kD. Immunocytochemical data and Western immunoblot data suggest that the membrane antigen is derived from the fluid antigen, which, in turn, is secreted by the epididymal epithelium. Characterization of the membrane antigen indicates that it is tightly associated with the sperm surface, behaving as though it is an integral membrane protein. The antigen persists on ejaculated sperm.
 ...
PMID:Rat epididymis-specific sperm maturation antigens. I. Evidence that the 26 kD 4E9 antigen found on rat caudal epididymal sperm tail is derived from a protein secreted by the epididymis. 817 1

A 38-kDa protein, sp38, was purified from the detergent extract of porcine epididymal sperm. Sp38 showed zona pellucida-binding properties similar to those of proacrosin. These two proteins specifically bound to the 90-kDa glycoprotein form of the zona pellucida components in a calcium-dependent manner. The binding of sp38 to the zona pellucida glycoprotein was inhibited by proacrosin. These findings suggest that the two proteins competitively interact with the zona pellucida during the early stage of fertilization.
 ...
PMID:Purification and characterization of a 38-kDa protein, sp38, with zona pellucida-binding property from porcine epididymal sperm. 821 93

In previous studies, we reported that rat epididymal fluid acid beta-D-galactosidase, which optimally cleaves a synthetic substrate (PNP beta-D-galactoside) at pH 3.5, shows maximum activity at pH 6.8 when a glycoprotein is used as a substrate [Skudlarek MD, Tulsiani DRP, Orgebin-Crist M-C. Biochem J 1992; 286: 907-914]. We now describe a similar pH-dependent substrate preference for rat sperm beta-D-galactosidase. We found that only 10-14% of total beta-D-galactosidase (and other glycosidase) activity was associated with spermatozoa. The remaining enzyme activities were present in soluble form in the luminal fluid. When the glycosidase levels were expressed per 10(6) sperm, all enzymes showed a progressive increase in spermatozoa from the caput to the corpus or proximal cauda followed by a sharp decline in spermatozoa from the distal cauda epididymidis. The observed decrease in beta-D-galactosidase activity could not be explained by the loss of cytoplasmic droplets (which have a low enzyme activity relative to spermatozoa) or the presence of inhibitors/activators of the enzyme activity in spermatozoa from the proximal or distal epididymis. However, we found that the changes in beta-D-galactosidase activity during sperm maturation in the epididymis were accompanied by changes in the molecular form(s) of the enzyme. Western blot analysis using an antibody to beta-D-galactosidase showed a progressive processing of the 82-kDa immunoreactive band in caput spermatozoa to an 80-kDa diffuse band in cauda spermatozoa. The sperm-associated beta-D-galactosidase form(s) does not appear to be due to adsorption and/or binding of the luminal fluid beta-D-galactosidase, which contained a 97-kDa form in fluid from the caput and two forms, of 97 kDa and 84 kDa, in corpus and cauda fluids. The observed difference in the molecular forms of the sperm and luminal fluid was found to be due to differential glycosylation, since de-N-glycosylation of various forms of beta-D-galactosidase generated a single immunoreactive form of 70 kDa. Subcellular localization studies and assay for the beta-D-galactosidase activity in the enriched plasma membrane and acrosomal membrane fractions suggested the likelihood that the activity of beta-D-galactosidase and other glycosidases is present in the acrosome and is readily released during sperm disruption. The evidence suggests that sperm beta-D-galactosidase may be functional within the acidic environment of the acrosome during sperm maturation as well as in the neutral environment of the oviduct after the zona-induced acrosome reaction.
 ...
PMID:Beta-D-galactosidase of rat spermatozoa: subcellular distribution, substrate specificity, and molecular changes during epididymal maturation. 837 43

Acidic epididymal glycoprotein (AEG) is an androgen-dependent, epididymal secretory protein assumed to play a major role in sperm maturation. In the present study, we isolated cDNA clones encoding the human AEG-like molecule and determined their nucleotide sequences. The deduced human AEG-like molecule was made up of 230 amino acids, excluding a signal peptide, and contained one potential N-linked glycosylation site. All cysteinyl residues were conserved between the human AEG-like molecule and the AEG molecules of rats and mice. The human AEG-like molecule was equally similar to the AEG molecules of rats and mice and a related testis-specific protein known as TPX1 of human and mice (approximately 40% amino acid sequence similarity). Northern blot analysis showed that the human AEG-like gene is expressed specifically in the epididymis. To identify the product of the human AEG-like gene, polyclonal antibody was produced by immunizing rabbits with a recombinant human AEG-like protein expressed in E. coli. This antibody detected a major band of 30 kD and a minor band of 26 kD in the caput, corpus, and cauda regions of the epididymis, the ductus deferens, the sperm, and the seminal plasma. Immunohistochemical analysis showed that the human AEG-like molecule is located in the lumen and epithelium of distal ductus efferentes and epididymal ducts, and on the postacrosomal region of the sperm head.
 ...
PMID:[Analysis of the human acidic epididymal glycoprotein-like molecule: isolation of cDNA and tissue localization]. 854 80


<< Previous 1 2 3 4 5 6 7 8 9 10