Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01189 (beta-endorphin)
 21,003 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The presence of a high-molecular weight complex with acid phosphatase activity in the cytosol of human mammary tumors is reported. This complex appeared in the cytosol after tissue homogenization in the presence of dithiotreitol, with or without Triton X-100 and at acidic or neutral pH. Upon gel electrophoresis, this fraction showed only one band of enzyme activity which did not enter the fine pore gel. Lubrol or n-butanol had no apparent effect on this complex, and 8 M urea or 2% sodium dodecyl sulfate did not disaggregate this large molecule. After purification by gel filtration, ammonium sulfate precipitation and ion-exchange chromatography an apparent molecular weight or 10(6) was measured. It hydrolyzed typical acid phosphatase substrates such as p-NPP and alpha-NP, but also ATP and PPi. Only 44% inhibition was observed with L-(+)tartrate and it was still 40% active after 1 hr incubation at 60 degrees C. Reduction in the presence of SDS yielded several polypeptide bands. It was also detected in some samples of normal mammary tissues, but not in normal human placenta or liver.
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PMID:A high-molecular weight complex with acid phosphatase activity in human breast cancer. 609 19

Using antibodies against peptides derived from different portions of the POMC molecule, immunocytochemical evidence suggests that this precursor and/or the peptides present within it are localized in testicular Leydig cells of at least five species. There is no evidence for the localization of these peptides or their precursor in any other cell type in this organ. Examination of testicular extracts by gel filtration, SDS-PAGE, and RP-HPLC indicate that the testis contains low concentrations of POMC-derived peptides relative to brain. Further analysis indicates that POMC is processed to alpha-MSH and beta-endorphin similar to its processing in intermediate pituitary lobe and brain. The relative mobilities of immunoreactive alpha-MSH and beta-endorphin on RP-HPLC columns indicate that they are in the unacetylated state as in brain and in contrast to the acetylated forms in the intermediate pituitary lobe. The potential for Leydig cells to synthesize POMC and its peptides was suggested by the demonstration of POMC-like mRNA in total testis and Leydig cell cultures. The size of the POMC-like mRNA is approximately 150 base pairs shorter than anterior or intermediate pituitary POMC mRNA. POMC-like mRNA activity has also been localized to Leydig cells in sections of testes using in situ hybridization. Immunostainable beta-endorphin and other POMC-derived peptides are present in testicular Leydig cells during fetal life and following puberty at times when testosterone secretion is maximal. The accumulation of immunostainable POMC-derived peptides in Leydig cells is dramatically increased by LH and hCG. A variety of observations suggests that testicular cells can respond to POMC-derived peptides. ACTH and the MSHs stimulate growth and cAMP accumulation in Sertoli cells. By contrast, studies using antagonists suggested that beta-endorphin and/or another testicular opioid inhibit Sertoli cell proliferation and ABP secretion. These observations are consistent with the postulate that different portions of the POMC molecule may have opposite effects on Sertoli cell function and suggest a mechanism by which Leydig cells could modulate Sertoli cell activity. Intratesticular administration of opiate antagonists inhibits testosterone secretion both in vivo and in vitro. These observations suggest that Leydig cell-derived beta-endorphin may facilitate testosterone secretion either directly or indirectly. The finding of POMC and its derivative peptides in testis, ovary, adrenal, and placenta suggests that all steroid hormone-secreting organs in mammals may utilize this peptidergic system.
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PMID:Identification and possible function of pro-opiomelanocortin-derived peptides in the testis. 610 19

Antibodies to the phosphoprotein B-50 of rat brain were used to trace cross-reacting brain proteins of vertebrates. With the SDS-gel-immunoperoxidase method, a cross-reacting protein (CP) of apparent Mr 53,000 was demonstrated in the homogenate and the synaptic plasma membrane fraction of bovine brain. Sequence 1-24 of adrenocorticotropin (ACTH1-24) (10(-5) M and 10(-4) M) inhibited endogenous phosphorylation of CP in synaptic plasma membranes. The protein was partially characterized and purified to homogeneity from bovine brain by procedures previously described for rat B-50. CP was enriched in ammonium sulfate precipitated protein (ASP) fractions and phosphorylated by an endogenous protein kinase. Two-dimensional gel analysis of bovine and rat ASP showed that the cross-reacting protein had an isoelectric point less acidic than B-50. Limited proteolysis by Staphylococcus aureus protease yielded a "peptide map" analogous to B-50. Two major fragments of Mr 30,000 and 17,000 were produced. In addition, CP exhibited other similarities to rat B-50: phosphorylation by rat brain protein kinase C, microheterogeneity observed after isoelectric focusing, and possibly degradation by endogenous proteolysis. Cross-reaction of proteins in brain homogenates of other mammalian species and of chicken was demonstrated: the Mr of the proteins ranged from 47,000 to 53,000. We conclude that (1) the cross-reacting bovine protein is a "B-50 protein," and (2) the Mr of the "B-50 protein" varies from species to species.
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PMID:Cross-reaction of anti-rat B-50: characterization and isolation of a "B-50 phosphoprotein" from bovine brain. 623 84

Previous studies in this and other laboratories have indicated that corticotropin (ACTH) administered to intact or hypophysectomized rats or mice increased the labelling of cerebral proteins by radioactive amino acids, presumably indicative of increased protein synthesis. This study was designed to reveal whether this increased labelling was specific for particular proteins by studying labelling patterns in SDS polyacrylamide gels using a double isotope procedure. Two strains of mice, two different amino acid precursors, leucine and lysine, and both peripheral and central administration of ACTH and amino acids were used. In no case were treatment dependent changes in labelling observed in any region of the gel. This included regions containing S-100 or NSP, two brain specific proteins whose content had been reported to be increased by treatment of rats with an ACTH analog.
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PMID:Corticotropin-induced changes in protein labelling: lack of molecular specificity. 625 68

A macromolecular aggregate of corticotropin-beta-lipotropin common precursor had been observed in ovine pituitary preparations as an excluded fraction of Sephadex G-200 gel filtration. This fraction could not penetrate a 10% gel during sodium dodecyl sulfate-polyacrylamide gel electrophoresis, when 2-mercaptoethanol or other disulfide-cleaving agents were not present in the buffer used to solubilize the protein preparation prior to the electrophoresis. On a 4.6% gel (acrylamide:bisacrylamide, 20:1), the material migrated as a diffuse band to a position between those of beta-galactosidase (Mr 130 000) and myosin (Mr 200 000). Both observations were consistent with an apparent Mr greatly in excess of that of the corticotropin-beta-lipotropin common precursor reported by many investigators. Neither 5% SDS nor 1% Triton X-100 could dissociate the macromolecular aggregate, but 2-mercaptoethanol and urea, either alone or in combination, were able to dissociate it to two main protein components, one of which was identified as corticotropin-beta-lipotropin with an apparent Mr of 34 000. The fact that urea alone could dissociate this macromolecular aggregate led us to believe that it might be a non-covalent aggregate and that 2-mercaptoethanol probably did not achieve the dissociation through the cleavage of an interchain disulfide bond but by bringing about conformational changes as a result of reduction of intrachain disulfide bonds so that aggregation became unfavorable. Moreover, the dissociation by urea or by 2-mercaptoethanol was found to be irreversible. The origin of the macromolecular aggregate of corticotropin-beta-lipotropin common precursor remains obscure.
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PMID:Characterization of a macromolecular aggregate of ovine pituitary corticotropin-beta-lipotropin common precursor. 626 48

Biosynthesis and processing of ACTH/beta-lipotropin was studied in Nelson's syndrome pituitary tumor tissue grown in monolayer culture. Radiolabeled peptides were immunoprecipitated and fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS/PAGE). Important findings include: 1) a virtual absence of 13K ACTH or 3.5K beta-endorphin production; 2) evidence indicating the presence of a 24-26K ACTH and beta-LPH containing intermediate (which implies a different order of processing from that reported in the mouse); 3) An extremely rapid rate of turnover and release of ACTH and beta-lipotropin (beta-LPH) similar to that of the mouse AtT20/D16v pituitary tumors. The latter finding is consistent with an intrinsic pituitary cell defect in the pathogenesis of this disorder.
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PMID:Corticotropin/beta-lipotropin biosynthesis, processing, and release in Nelson's syndrome. 627 Jan 78

gamma MSH, a putative hormone in the N-terminal region of the ACTH/beta-endorphin (beta-EP) precursor protein, was studied by RIA with an antiserum against gamma 3MSH in ACTH-producing mouse pituitary tumor cells, AtT-20/D16v. Serial dilution of the culture medium or the cell extract gave parallel lines to the standard curve in the RIA for gamma MSH. Rat median eminence extracts enhanced the release of gamma MSH-like immunoreactivity (gamma MSH-LI) concomitant with ACTH-like immunoreactivity (ACTH-LI) and beta-EP-like immunoreactivity (beta-EP-LI). Dexamethasone suppressed the release of gamma MSH-LI as well as ACTH-LI and beta-EP-LI. Gel exclusion chromatography of the culture medium and the cell extract has revealed that gamma MSH-LI consists of two peaks; one eluted near the elution position of beta-lipotropin and the other near the elution position of beta-EP. There was no peak corresponding to the elution position of synthetic gamma 3MSH. However, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) has demonstrated that gamma MSH-LI migrated at five positions with molecular weights of 31K, 21-23K, 16-17K, 13-14K, and 3.8K, respectively. The 31K gamma MSH coincided with the migration position of 31K ACTH of 31K beta-EP, and 21-23K gamma MSH coincided with the position of 21-23K ACTH on SDS-PAGE. The 16-17K gamma MSH coincided with the mouse 16K fragment (reported by Eipper and Mains) of ACTH-beta-lipotropin precursor protein in the migration in SDS-PAGE and in immunoreactivity to anti-gamma MSH antiserum. [3H]Glucosamine was incorporated into 16K, 13K, and 3.8K gamma MSH. These results suggest that AtT-20/D16v cells produce gamma MSH-LIs with molecular weights of 31K, 21-23K, 16-17K, 13-14K, and 3.8K, and they are secreted concomitantly with ACTH-LI and beta-EP-LI.
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PMID:Characterization of gamma-melanotropin-like immunoreactivity and its secretion in an adrenocorticotropin-producing mouse pituitary tumor cell line. 628 79

Ovine corticotropin-beta-lipotropin common precursor was purified to homogeneity from commercial frozen ovine pituitary glands. A crude preparation was obtained following a procedure published elsewhere (Lee, T.H. and Lee, M.S. (1977) Biochemistry 16, 2824-2829) and was purified by gel filtration on Sephadex G-200 in the presence of 0.5% SDS and 0.1% 2-mercaptoethanol, and under an atmosphere of nitrogen. The gel filtration was repeated once. The partially purified preparation obtained from the second Sephadex G-200 gel filtration was further fractionated by preparative SDS-acrylamide gel electrophoresis, using immunoprecipitated and electrophoretically purified [125I]corticotropin-beta-lipotropin common precursor as a marker. The preparation was judged homogeneous by the appearance of a single protein band in analytical SDS-acrylamide gel electrophoresis, which exhibited both corticotropin and beta-lipotropin immunoreactivities, and a single symmetrical peak in high-pressure liquid chromatography on a reverse phase C18 column. The isolated ovine corticotropin-beta-lipotropin common precursor possessed specific activities of 116 micrograms of immunoreactive corticotropin and 210 micrograms of immunoreactive beta-lipotropin per mg of protein, equivalent to 89 and 62% of theoretical values, respectively. The amino acid composition of the homogeneous preparation was determined.
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PMID:Isolation of corticotropin-beta-lipotropin common precursor from ovine pituitary glands. 674 90

Microvascular endothelial cells were isolated from the brains of C57 mice and cultured in selective growth media. The isolation and culture techniques employed in this study minimised the contamination by nonendothelial cells such as astrocytes, pericytes, and smooth muscle cells. Microvascular endothelial cells examined using phase contrast light microscopy grew as small colonies of spindle-shaped cells which merged together to form typical contact-inhibited monolayers. The endothelial origin of these cells was determined using several established characterisation techniques. Preliminary receptor binding studies at 4 degrees using [125I-Tyr2, Nle4, D-Phe7]alpha-melanocyte-stimulating hormone ([125I-Tyr2, Nle4, D-Phe7]alpha-MSH) suggested the possibility that melanocortin receptors were present on the surface of brain microvascular endothelial cells. Subsequent binding isotherms confirmed that a small population of high-affinity melanocortin receptors was expressed. The existence of a specific binding site for alpha-MSH was confirmed by photoaffinity labeling with the 4-(1-azi-2,2,2,-trifluoroethyl)benzoic acid (ATB) derivative, [125I-Tyr2, Nle4, D-Phe7, (ATB)-Lys11] alpha-MSH. SDS-PAGE analysis identified the presence of a specific band with a molecular mass of approximately 45 kDa, which was consistent with previous data on melanoma melanocortin receptors, and represented a ligand-receptor complex. This study suggests that a receptor for alpha-MSH is expressed on the extracellular surface of murine brain microvascular endothelial cells; however, the physiological role of this receptor is as yet unknown.
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PMID:Identification of a melanocortin receptor expressed by murine brain microvascular endothelial cells in culture. 747 77

Using a specific anti-rat transferrin (Tf) antiserum, Tf-like immunoreactivity (Tf-lir) was detected by immunostaining in intact rat pituitaries and in reaggregated pituitary cells cultured in serum-free medium. Tf-lir cells were present in the anterior pituitary (AP), and in the intermediate (IL) and neural lobes (NL). In the AP, Tf-lir cells were oval or polygonal. An unusual topographical distribution was found. Tf-lir cells mainly occurred as dense clusters in the lateral wings. In the central part of the AP, Tf-lir was found in flattened perisinusoidal cells. Double immunostaining for Tf and the different pituitary hormones showed that Tf-lir co-localized with some gonadotrophs and somatotrophs (7% and 3% of Tf-lir cells, respectively, in typical sections). No co-localization was seen with PRL, ACTH, TSH, or alpha-MSH. The distribution of Tf-lir cells and their cell shape completely differed from that of S-100-positive cells in the AP. In the IL, clusters of large stellate Tf-lir cells were found. Again, their distribution completely differed from S-100-positive cells. In the NL, diffuse staining was found. Double immunostaining of paraffin-embedded sections of reaggregate cell cultures of the AP did not reveal any co-localization of Tf-lir with ACTH, alpha-MSH, LH, FSH, TSH, GH, or PRL. In aggregates consisting of NL + IL cells, Tf-lir was located in clusters: no co-localization with ACTH or alpha-MSH could be demonstrated. Reaggregate cell cultures of AP and NL + IL secreted Tf-lir as measured by radioimmunoassay, at least during 21 days of culture. After metabolic labeling with [35S]-methionine and immunoprecipitation of [35S]-methionine-labeled material present in the culture medium of both AP and NL + IL aggregates with anti-Tf antiserum, a 35S-labeled substance was found, which on SDS-PAGE showed an apparent M(r) of approximately 78 KD, corresponding to the M(r) of rat Tf. The present data show that a specific population of cells of rat anterior pituitary is capable of synthesizing, storing, and secreting transferrin or a substance closely related to it. Cells different from melanotrophs and S-100 cells in the IL, as well as pituicytes in the NL, also appear to produce this material. We suggest that transferrin or a transferrin-like substance may have a local role in the transport of iron or other metals or may play a role as growth factor in the three lobes of the pituitary gland.
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PMID:Production of transferrin-like immunoreactivity by rat anterior pituitary and intermediate lobe. 760 20


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