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

Previous studies using L6 myotubes have suggested that glycogen synthase kinase-3 (GSK-3) is phosphorylated and inactivated in response to insulin by protein kinase B (PKB, also known as Akt or RAC) (Cross, D. A. E., Alessi, D. R., Cohen, P., Andjelkovic, M., and Hemmings, B. A. (1995) Nature 378, 785-789). In the present study, marked increases in the activity of PKB have been shown to occur in insulin-treated rat epididymal fat cells with a time course compatible with the observed decrease in GSK-3 activity. Isoproterenol, acting primarily through beta3-adrenoreceptors, was found to decrease GSK-3 activity to a similar extent (approximately 50%) to insulin. However, unlike the effect of insulin, the inhibition of GSK by isoproterenol was not found to be sensitive to inhibition by the phosphatidylinositol 3'-kinase inhibitors, wortmannin or LY 294002. The change in GSK-3 activity brought about by isoproterenol could not be mimicked by the addition of permeant cyclic AMP analogues or forskolin to the cells, although at the concentrations used, these agents were able to stimulate lipolysis. Isoproterenol, but again not the cyclic AMP analogues, was found to increase the activity of PKB, although to a lesser extent than insulin. While wortmannin abolished the stimulation of PKB activity by insulin, it was without effect on the activation seen in response to isoproterenol. The activation of PKB by isoproterenol was not accompanied by any detectable change in the electrophoretic mobility of the protein on SDS-polyacrylamide gel electrophoresis. It would therefore appear that distinct mechanisms exist for the stimulation of PKB by insulin and isoproterenol in rat fat cells.
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PMID:Regulation of protein kinase B and glycogen synthase kinase-3 by insulin and beta-adrenergic agonists in rat epididymal fat cells. Activation of protein kinase B by wortmannin-sensitive and -insensitive mechanisms. 906 30

The guinea pig sperm acrosomal matrix is the dense core of the acrosome and is likely to be important in acrosome biogenesis and fertilization. Isolated acrosomal matrices are composed of a limited number of major bands when analyzed by SDS-polyacrylamide gel electrophoresis, among which is a Mr 67,000 protein that we have termed AM67. Indirect immunofluorescence demonstrated that AM67 is localized to the apical segment of the cauda epididymal sperm acrosome. Immunoelectron microscopy further refined the localization of AM67 to the M1 (dorsal bulge) domain within the acrosome. Using a polymerase chain reaction product based upon tryptic peptide sequences from AM67, a lambdagt11 guinea pig testis cDNA library was screened to yield two cDNA clones that encode the AM67 peptides. Northern analysis revealed that AM67 is transcribed as a 1. 9-kilobase testis-specific mRNA. The complete AM67 sequence encodes a prepropolypeptide of 533 amino acids with a calculated Mr of 59, 768. Following cleavage of a probable signal sequence, the polypeptide was predicted to have a Mr of 56,851 and seven consensus sites for asparagine-linked glycosylation. The deduced amino acid sequence of AM67 is most similar to those of the mouse sperm protein sp56 and the alpha-subunits of complement component 4-binding proteins from various mammalian species. Although mouse sp56 has been reported to be a cell-surface receptor for the murine zona pellucida glycoprotein ZP3, standard immunoelectron microscopy using the anti-sp56 monoclonal antibody 7C5 detected sp56 within the mouse sperm acrosome, but failed to detect sp56 on the surface of acrosome-intact mouse sperm. Furthermore, acrosomal labeling was detected in mouse sperm prepared for immunofluorescence using paraformaldehyde fixation, but was not observed with live unfixed sperm. Thus, the finding that sp56 is present within the acrosome provides further support that sp56 and AM67 are orthologues and suggests that sp56 may function in acrosomal matrix-zona pellucida interactions during and immediately following the acrosome reaction in the mouse.
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PMID:AM67, a secretory component of the guinea pig sperm acrosomal matrix, is related to mouse sperm protein sp56 and the complement component 4-binding proteins. 913 29

The purpose of the present study is to purify, kinetically characterize and measure the amount of soluble acid beta-D-galactosidase (EC 3.2.1.23) in different anatomical regions (caput, corpus, and cauda) of the adult rat epididymis. Based upon SDS-PAGE analysis, the subunit molecular mass of the caput and cauda enzyme is approximately 85,000 daltons while the corpus enzyme is approximately 50,000 daltons. The apparent Km and Vmax values are 67, 24, and 59 microM and 5.0, 1.88 and 6.3 microM/min./-mg protein for the enzyme purified from the caput, corpus, and cauda regions of the epididymis, respectively. However, no regional differences in the amount of soluble enzyme protein are observed. These data demonstrates regional differences in the activity of epididymal acid beta-D-galactosidase and suggest that the observed regional differences in enzyme activity may be due to posttranslational modifications.
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PMID:Purification, characterization, and expression of rat epididymal beta-D-galactosidase. 924 2

The structural organization of the chromatin of cauda epididymal spermatozoa of the red veld rat Aethomys chrysophilus type B was investigated by fluorescence microscopy after staining with DNA specific dyes and by transmission electron microscopy after incubation with Triton X100, dithiothreitol, and SDS. Staining with DNA dyes showed variation in intensity of fluorescence of the sperm chromatin, with an anterior spherical region staining far more intensely than the surrounding chromatin. Transmission electron microscopy of these spermatozoa indicated that this region was composed of cords and fibres. This chromatin region dispersed more readily than the surrounding chromatin when spermatozoa were incubated with the detergents, and it is suggested that, unlike the rest of the sperm chromatin, it may be a histone-rich region, with protamine(s) being either scarce or absent.
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PMID:Unusual chromatin structural organization in the sperm head of a murid rodent from southern Africa: the red veld rat, Aethomys chrysophilus type B. 946 89

Megalin (gp330) is a large glycoprotein receptor found mainly on a group of absorptive epithelial cells, including renal proximal tubule, epididymal and thyroid cells. Megalin has been shown to bind multiple, unrelated ligands, mainly in vitro, and to mediate endocytosis of ligandsin cultured cells. However, physiologic ligands of megalin are largely unknown. In the present study we have demonstrated that purified rat megalin binds rat thyroglobulin (Tg) in solid phase assays, with anestimated Kd of 9.2+/-0.6 nM. Binding was calcium dependent and was almost completely inhibited by excess Tg, by three megalin ligands - lactoferrin, lipoprotein lipase and apolipoprotein J- and by the receptor associated protein (RAP), which inhibits binding of all megalin ligands. Three anti-megalin antibodies partially inhibited Tg binding to megalin. 125I labeled Tg bound to megalin was released by EDTA and heparin; the released product was shown by SDS-PAGE and autoradiography to be 660 kD (dimeric) Tg. However, an immunoblotting experiment showed binding of megalin both to monomeric (330 kD) and dimeric Tg. We propose that megalin, which is known to mediate ligand endocytosis and is found on the apical surface of thyrocytes, may participate in the endocytosis of Tg from the colloid, a process that is required for hormone release from Tg.
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PMID:Megalin (gp330): a putative endocytic receptor for thyroglobulin (Tg). 949 85

The objective of this study was to characterize a 26-kDa seminal plasma protein previously shown to be prevalent in bulls of high fertility. Spots of this protein, excised and electroeluted from two-dimensional SDS-PAGE gels, were used for N-terminal amino acid sequencing and for preparation of antiserum in rabbits. The N-terminal amino acid sequence (ALQPNFEEDKFLGRWFTSGL) was 75% identical and 100% homologous to lipocalin-type prostaglandin (PG) D synthase isolated from human cerebrospinal fluid (CSF). Western blots of purified 26-kDa protein cross-reacted with polyclonal antibodies against lipocalin-type PGD synthase isolated from rat brain and human CSF. Immunoreactive bands at 26 kDa appeared in Western blots of seminal plasma and cauda epididymal fluid (CEF). A 29-kDa band appeared in blots of rete testis fluid (RTF). PGD synthase activity was detected in seminal plasma, CEF, and RTF. The cDNA for bovine lipocalin-type PGD synthase, isolated by reverse transcription-polymerase chain reaction, contained a coding region of 573 base pairs corresponding to 191 amino acids. The amino acid sequence was 63-80% identical to that of the enzyme of other mammals. These results establish that the 26-kDa fertility-associated protein in bull seminal plasma is lipocalin-type PGD synthase. Although we do not yet know the role of lipocalin-type PGD synthase in the male genital tract, we speculate that this protein may play an important role in both the development and the maturation of sperm.
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PMID:Identification of a fertility-associated protein in bull seminal plasma as lipocalin-type prostaglandin D synthase. 951 Sep 73

The sperm plasma membrane is segregated into functionally, biochemically, and structurally distinct domains yet the protein sorting pathways and assembly mechanisms that assemble these domains during spermiogenesis are incompletely understood. We previously characterized two structurally related size-variant, integral membrane proteins of 52 kDa (PM52) and 35 kDa localized to the periacrosomal plasma membrane of guinea pig cauda epididymal spermatozoa (Westbrook-Case et al., 1994). In this study we used light and electron microscopic immunocytochemistry to define the expression pattern and sorting pathway that establishes the domain-specific distribution of PM52 during spermiogenesis. The PM52 is first expressed in acrosome-phase spermatids and it localizes exclusively to the cytoplasmic lobe. Immunoelectron microscopy revealed that both cytoplasmic vesicles and the plasma membrane of the cytoplasmic lobe labeled with anti-PM52. During early stages of expression, PM52 appeared to be absent from the head region, but significant PM52 accumulation over the spermatid head was noted in late acrosomal phase spermatids. Throughout spermiogenesis PM52 extended posteriorly to the annulus, which represents a barrier preventing PM52 diffusion into the posterior tail. Following the migration of the annulus to the midpiece-principal piece junction, PM52 began to disappear from the flagellar region and at the completion of spermiogenesis most of the PM52 was restricted to the acrosomal segment. Spermatids and epididymal sperm PM52 exhibited identical sizes by SDS-PAGE and immunoblotting, indicating that they are not proteolytically modified during epididymal maturation. The PM52 antibodies were also used to screen a guinea pig testis cDNA library, and sequence determination of full-length PM52 clones demonstrated identity of a sperm membrane protein recently termed "sperad" (Quill and Garbers, 1996). Membrane barriers and potential mechanisms establishing the domain-specific residence of PM52 are discussed.
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PMID:Targeting of the domain-specific integral membrane protein PM52 to the periacrosomal plasma membrane during guinea pig spermiogenesis. 954 16

SDS-PAGE (12.5%) analysis and neutral alpha-glucosidase, fructose, and zinc level assessment were carried out in seminal plasma of 20 patients with highly viscous ejaculates and of 20 control subjects, with the aim to investigate the relations between high consistency of semen and epididymal, vesicular, and prostatic secretions. Very low sperm motility was observed in all the patients' ejaculates, both normo- and oligozoospermics. Protein patterns obtained in control and highly viscous semina showed similar protein bands, in the range of 10-100 kD. Furthermore, unaltered seminal neutral alpha-glucosidase, zinc, and fructose level were measured in the same specimens. These results indicated no impairment of epididymal, vesicular, and prostatic function in patients with hyperviscous semina, while their normal electrophoretic seminal protein profile suggested unaltered genital fluid interactions during the semen coagulation-liquefaction process.
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PMID:Unaltered protein pattern/genital tract secretion marker levels in seminal plasma of highly viscous human ejaculates. 964 58

Acrosin is an acrosomal protease believed to play a major role in fertilization. It is synthesized as an inactive precursor, proacrosin, which is processed via (auto)proteolysis into active form(s). In this paper, comparative studies on the characteristics of acrosin from mouse, boar and human are reported. The mouse proacrosin/acrosin was especially investigated to clarify whether or not the enzyme undergoes modifications during epididymal maturation. Acrosomal extracts from mature and immature mouse spermatozoa, as well as from ejaculated boar and human spermatozoa, were analysed by means of SDS-electrophoresis, Western blot and activity measurements. The studies showed that epididymal maturation produced a shift in the molecular weight of proacrosin. It was also observed that the activation kinetics differ strongly between the three species studied. Human proacrosin showed a constant substrate turnover, acrosin from boar showed sigmoidal activation kinetics and mouse acrosin, either from the caput or the cauda epididymides, showed a rapid decay in activity, suggesting the presence of an endogenous specific inhibitor.
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PMID:Characterization of mouse epididymal acrosin: comparative studies with acrosin from boar and human ejaculated spermatozoa. 967 18

We identified SH2-Balpha as an insulin-receptor-binding protein based on interaction screening in yeast hybrid systems and co-precipitation in cells. SH2-Balpha contains pleckstrin-homology ('PH') and Src homology 2 (SH2) domains and is closely related to APS (adapter protein with a PH domain and an SH2 domain) and lnk, adapter proteins first identified in lymphocytes. SH2-Balpha is ubiquitously expressed and is present in rat epididymal adipose tissue, liver and skeletal muscle, physiological sites of insulin action. On SDS/PAGE, SH2-Balpha migrates at a molecular mass of 98 kDa, although the predicted size of SH2-Balpha is 79.6 kDa. Insulin causes an electrophoretic mobility shift. SH2-Balpha can be immunoprecipitated using anti-(insulin receptor) antibody from insulin-stimulated cells. Anti-phosphotyrosine antibody or the growth factor receptor-binding protein 2 (Grb2) SH2 domain precipitate SH2-Balpha after insulin stimulation, suggesting that SH2-Balpha is tyrosine-phosphorylated and may be a substrate for the insulin receptor. The SH2-Balpha SH2 domain did not interact with insulin-receptor substrate (IRS) proteins or epidermal-growth-factor receptor. Mutation of the juxtamembrane and C-terminus of the insulin receptor did not abolish the interaction with the SH2 domain. This was further confirmed using a panel of activation-loop single point mutants where mutation of Tyr1158, Tyr1162 and Tyr1163 abolished interaction. Thus SH2-Balpha is a likely component in the insulin-signalling pathway and may function as an alternative signalling protein by interacting with the activation loop of the insulin-receptor cytoplasmic domain.
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PMID:SH2-Balpha is an insulin-receptor adapter protein and substrate that interacts with the activation loop of the insulin-receptor kinase. 974 18


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