Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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 same isoenzyme of nonspecific alkaline phosphatase (APase), assayed with p-nitrophenylphosphate (p-NPP), was shown be present in different calcifying tissues, bone, calcifying cartilage, odontoblasts and enamel organ. Indications were also found that the enzymatic degradation of inorganic pyrophosphate (PPi) in calcifying tissues is mediated by APase. By using specific APase inhibitors, it was shown that two enzymes capable of degrading ATP exist. These were characterized in dentinogenically active odontoblasts, and it was concluded that one is the classical APase, the other is a Ca2+ and Mg2+ activated ATPase, named Ca2+-ATPase. The two phosphatases were solubilized from odontoblasts and separated. The localization of APase and Ca2+-ATPase in odontoblasts was investigated by subcellular fractionation and EM histochemistry. Routine methods for fixation were found to almost completely inactivate the enzymes. By using a mild fixation technique that preserved 80% of the enzyme activity, the main localization for both APase and Ca2+-ATPase was found to be in the membranes of intercellular vesicles located in the cell body and odontoblasts process. No activity was found in the cell membranes. It is concluded that there are at least two enzymes able to degrade phosphate compounds at alkaline pH in hard tissue forming cells. One is the nonspecific alkaline phosphatase (APase; EC 3. 1. 3. 1), which is active against p-NPP, PPi, glycerophosphates and ATP among other substrates. The other is a more specific Ca2+-ATPase (EC 3. 6. 1. 3). There seems to be an intimate relation between these two enzymes in the tissue. The function of APase in biological calcification is still obscure. In contrast, the finding of an ATP dependent, intravesicularly directed, transmembranous Ca2+-transport in vesicles derived from the microsomal fraction of odontoblasts may explain the role of Ca2+-ATPase.
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PMID:Odontoblast alkaline phosphatases and Ca2+ transport. 15 9

Human peripheral lymphocytes were broken in a Dounce homogenizer and subcellular fractions enriched in plasma membranes or microsomal particles and mitochondria were isolated by centrifugation through a discontinuous sucrose gradient. Various agents that promote cyclic AMP accumulation in intact lymphocytes were compared in their ability to stimulate adenylate cyclase activity in the individual fractions. Plasma-membrane-rich fractions that were essentially free of other subcellular particles as judged by electron microscopy and marker enzyme measurements responded to fluoride, but weakly or not at all to prostaglandin E1 and other prostaglandins. Microsomal and mitochondrial-rich fractions responded markedly to both prostaglandin E1 and fluoride. In some, but not all, experiments phytohaemagglutinin produced a modest increase in enzyme activity in plasma-membrane-rich fractions. Catecholamines, histamine, parathyrin, glucagon and corticotropin produced little or no response. In the absence of theophylline, adenosine (1-10 micronM) stimulated basal enzyme activity, although at higher concentrations the responses to prostaglandin E1 and fluoride were inhibited. GTP (1-100 micronM) and GMP(5-1000 micronM) respectively inhibited or stimulated the response to fluoride, whereas the converse was true with prostaglandin E1.
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PMID:Adenylate cyclase activity in lymphocyte subcellular fractions. Characterization of non-nuclear adenylate cyclase. 19 77

The effects of morphine, beta-endorphin and naloxone on the initial incorporation of 32Pi and [3H]glycerol into TPI, DPI and PI were measured in discrete subcellular fractions of the rat midbrain. Morphine and beta-endorphin significantly increased microsomal 32PI incorporation into TPI and PI but not DPI. Although neither morphine nor beta-endorphin significantly affected the levels of [3H]TPI or [3H]DPI, both agents significantly increased [3H]PI levels. All of the significant effects induced by morphine were blocked by naloxone treatment and were decreased after chronic morphine administration. However, naloxone treatment alone also mimicked all the effects of morphine except the increased incorporation of [3H]glycerol into PI. It was also found that chronic morphine treatment significantly increased the incorporation of 32Pi into synaptic TPI and DPI. This effect, however, did not show regional specificity being found in both cortical and subcortical synaptic membranes. Overall, the results suggest that the mechanisms of opioid action are closely associated with changes in the turnover of the brain phosphoinositides.
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PMID:Influence of morphine, beta-endorphin and naloxone on the synthesis of phosphoinositides in the rat midbrain. 22 11

Spironolactone administration (50 mg/kg/day for 3 days) to make guinea pigs decreased cortisol production by adrenal slices in vitro. Adrenal microsomal and mitochondrial cytochrome P-450 levels were also decreased after treatment with spironolactone. The decline in adrenal cytochrome P-450 content was accompanied by decreases in microsomal 21-hydroxylase and mitochondrial cholesterol side-chain cleavage and 11beta-hydroxylase activities. Activities of other adrenal enzymes, such as delta4-hydrogenase and NADPH-cytochrome c reductase, were unaffected by spironolactone treatment. Cortisone administration to guinea pigs failed to mimic the effects of spironolactone on adrenal function, which indicates specificity of spironolactone action and excludes inhibition of adrenocorticotropin secretion as a mode of action. Addition of spironolactone to isolated adrenal mitochondria or microsomes produced type I spectral changes with spectral dissociation constants similar to those for endogenous steroid substrates. Spironolactone, in vitro, inhibited 11beta- but not 21-hydroxylase activity. The results indicate that spironolactone administration diminishes the activity of adrenal mitochondrial as well as microsomal cytochrome P-450-containing enzymes, resulting in a fall in corticosteroid output.
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PMID:Mechanism of action of spironolactone on adrenocortical function in guinea pigs. 97 70

It has been shown that alpha-MSH inhibits the growth of amelanotic cells of human malignant melanoma (BRO) without their melanization or the expression of tyrosinase activity. alpha-MSH changed the activity of cytosol and microsomal forms of phosphatidyl inositol kinase and phosphatidyl inositol-4-phosphate kinase determining the concentration of phosphatidyl inositol-4-phosphate and phosphatidyl inositol-4,5-bisphosphate. It also induced an "outburst" in the levels of myo-inositol phosphates (mono-, bis- and 1,4,5-trisphosphates). Changes in the levels of myo-inositol phosphates occurred within seconds, and are suggested to play a certain part in the hormonal regulation of melanoma cell growth.
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PMID:Melanocyte-stimulating hormone (alpha-MSH) inhibits the growth of human malignant melanoma cells with the induction of phosphatidyl inositol and myo-inositol phosphate levels. 166 68

Lyso-platelet-activating factor (lyso-PAF): acetyl-CoA acetyltransferase (EC 2.3.1.67) enzyme activity was characterized for the first time in bovine adrenocortical tissue. It was found to be associated with the microsomal membrane fraction, in which it exhibited a specific activity of 0.4 nmol/min per mg of protein and catalytic properties similar to those described in other cell types. The adrenocortical acetyltransferase activity was increased by 2-3-fold on incubation of the preparation with purified protein kinase C (PKC) under phosphorylating condition. This activation was optimal after 5 min of incubation and paralleled an increase in PKC-catalysed 32P incorporation into microsomal proteins. Both acetyltransferase activation and protein phosphorylation were dependent on the presence of Ca2+ and phospholipids, and were blocked in the presence of the potent PKC inhibitor H-7. In the intact adrenocortical cell, angiotensin II and a potent phorbol ester (phorbol 12-myristate 13-acetate) were able to rapidly induce an increase in the biosynthesis of PAF, which was mostly released into the extracellular medium. These data suggest that bovine adrenocortical lyso-PAF acetyltransferase may be regulated by a PKC-dependent activation pathway, whereas no evidence for an additional adrenocorticotropin/cyclic AMP-dependent stimulation process was obtained in this cell type. Bovine adrenocortical cell membrane preparations were shown to possess high-affinity PAF-binding sites (Kd approximately 0.5 nM). Altogether, these observations suggest that PAF production and release may play a role in the autocrine or paracrine control of adrenocortical cell activation.
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PMID:Production of platelet-activating factor is a component of the angiotensin II-protein kinase C activation pathway in bovine adrenocortical cells. 188 37

The sexually differentiated microsomal enzyme steroid 5 alpha-reductase (NADPH: delta 4-3-oxosteroid 5 alpha-oxido-reductase, EC 1.3.99.5) catalyzes the NADPH-dependent conversion of testosterone to 5 alpha-dihydrotestosterone, a more potent androgen. In rat liver, this enzyme is expressed at a 10-fold higher level in adult females as compared to adult males. The pituitary regulation of this enzyme and its mRNA was studied in untreated and hypophysectomized rats and in rats rendered hypothyroid by treatment with the antithyroid drug methimazole. Hepatic 5 alpha-reductase activity was elevated 8-fold, to 85% of adult female levels, in adult male rats given growth hormone by continuous infusion. This same treatment was only partially effective in restoring 5 alpha-reductase in rats depleted of endogenous growth hormone by hypophysectomy, indicating that other pituitary-dependent factors contribute to the elevation observed in the inact animals. Further analysis revealed that thyroxine, but not adrenocorticotropic hormone (ACTH) or chorionic gonadotropin, could elevate 5 alpha-reductase activity and mRNA when given to the hypophysectomized rats and that this effect was enhanced by the presence of growth hormone. This thyroid hormone dependence was confirmed by the decrease in hepatic 5 alpha-reductase expression in hypothyroid rats and by its substantial restoration following thyroxine replacement. Thyroxine also stimulated expression of another female-predominant hepatic mRNA, encoding the steroid 16 alpha-hydroxylase cytochrome P-450f (IIC7), in a manner that was independent of the stimulatory effect of growth hormone on this transcript. In contrast, thyroid hormone did not significantly affect protein or mRNA levels of the growth hormone-stimulated, female-specific steroid sulfate 15 beta-hydroxylase P-450 2d (IIC12). These findings establish that thyroid hormones act at a pretranslational level to modulate the expression of some, but not all, growth hormone-stimulated hepatic mRNAs and demonstrate that both thyroxine and growth hormone can independently contribute to the sex-dependent expression of hepatic enzymes of steroid metabolism.
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PMID:Pretranslational control by thyroid hormone of rat liver steroid 5 alpha-reductase and comparison to the thyroid dependence of two growth hormone-regulated CYP2C mRNAs. 217 47

Many peripheral tissues express the proopiomelanocortin (POMC) gene as an 800-base mRNA that lacks the 5' end of the 1200-base pituitary transcript. The missing region encodes the peptide signal sequence, and thus, it is unlikely that any translation product would be secreted. We have found that a RNA transcript equivalent to this short message, generated by transcription in vitro from a T7 polymerase promoter, is translatable in a rabbit reticulocyte lysate, generating peptides of 27.5, 22.5, and 15.5 kD. None of these peptides appears to be processed or protected from proteinase-K digestion by a microsomal membrane fraction. In vivo studies were undertaken by transfecting into GH3 cells one of two expression vectors containing sequences that would produce either a full-length mRNA or a short (800-base) mRNA. The neomycin resistance gene was cotransfected with these plasmids, and 30 permanent cell lines were produced after selection in G418. Cell lines containing the full-length RNA secreted large quantities of ACTH and beta-endorphin immunoreactivity, whereas those expressing the short transcript secreted neither of these peptides. However extractable peptide was present in this latter type of cell line, thereby suggesting that the 800-base mRNA was translated, and that no peptide reached the secretory vesicle. These findings raise important questions about the role of peripheral POMC gene expression.
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PMID:In vitro and in vivo analysis of the processing and fate of the peptide products of the short proopiomelanocortin mRNA. 217 42

Insulin-like growth factor II (IGF-II) receptors were detected, localized, and structurally characterized in rat pituitary tissue sections and cultures of dispersed pituitary cells by immunohistochemistry, and affinity labeling with gel electrophoresis. Using highly specific antisera against IGF-II receptors (type 2 IGF receptors) and somatotropin (GH), intense type 2 receptor immunoreactivity was detected in both anterior and intermediate pituitary lobes. In anterior pituitary sections and cultures, type 2 receptor immunoreactivity colocalized to most GH-immunoreactive cells (somatotropes), as well as cells which did not contain GH. Intermediate lobe immunoreactivity was uniformly distributed throughout the parenchyma. In both anterior and intermediate pituitary lobes, type 2 receptor immunoreactivity was predominately localized to the plasma membrane of labeled cells, with little or no cytoplasmic labeling. GH immunoreactivity, on the other hand, was intracellular. Affinity labeling of microsomal membranes from anterior and neurointermediate pituitary tissues with 125I-IGF-II disclosed classical 230k type 2 receptors. The magnitude of affinity cross-linking from both lobes was similar to that of rat liver, indicating pituitary tissues, like liver tissue, are rich sources of type 2 receptors. These results suggest possible roles for IGF-II and the type 2 receptor in the regulation of synthesis or secretion of pituitary trophic hormones, including GH and pro-opiomelanocortin gene products.
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PMID:Structural characterization and immunohistochemical localization of receptors for insulin-like growth factor II in the rat pituitary gland. 254 57

Luteinizing hormone is the major regulator of Leydig cell differentiation and steroidogenic function. A number of hormones produced by the Leydig cell (e.g. estrogen, angiotensin, CRF, vasopressin) and the tubular compartment (inhibin, TGF beta), can influence both acute and long-term actions of LH. Conversely, hormones produced in the Leydig cells modulate tubular function (e.g. androgen, beta-endorphin, oxytocin). The LH stimulatory event can be negatively influenced by the action of angiotensin II through the guanyl nucleotide inhibitory unit of adenylate cyclase. We have recently discovered an action of corticotrophin releasing hormone through specific high-affinity low-capacity receptors in the Leydig cells which involves a pertussis toxin insensitive guanyl nucleotide regulatory unit with interaction between signalling pathways and resulting inhibition of LH induced cAMP generation and consequently of steroidogenesis. In contrast to other tissues the CRF receptor in the Leydig cells did not couple to Gs. CRF action is exerted through direct or indirect action of protein kinase C, at the level of the catalytic subunit of adenylate cyclase. Physiological increases in endogenous LH cause positive regulation of membrane receptors and steroidogenesis, while major elevations in circulating gonadotropin can induce down-regulation of LH receptors and desensitization of steroid responses in the adult cell. Gonadotropin-induced desensitization in adult rat tests include an estrogen mediated steroidogenic lesion of the microsomal enzymes 17 alpha-hydroxylase/17,20-desmolase. For further understanding of the regulation of this key enzyme of the androgen pathway the rat P450(17) alpha cDNA was cloned and sequenced. This cDNA expressed in COS-1 cells 17 alpha-hydroxylase/17,20-desmolase activities. From the deduced amino acid sequence, two transmembrane regions were identified, a signal peptide for insertion in the ER, and a 2nd transmembrane region separated from the first by 122 amino acids. The carboxy terminal non-transmembrane region possesses 4 hydrophobic clefts, of which cleft II would contain the putative steroid binding site for both hydroxylase and lyase activities. The rat cDNA was employed to evaluate the hormonal regulation of mRNA levels in adult and fetal Leydig cells. Low dose hCG treatment caused an early increase in mRNA levels followed by a return to control values at later times, while with higher desensitizing doses the initial increase in mRNA was followed by a marked reduction in mRNA at 24 h and a small recovery at 48 h. Fetal rat Leydig cells treated with E2 showed a 70% decrease in P450 mRNA levels, and testosterone production closely followed the changes in mRNA.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:LH action in the Leydig cell: modulation by angiotensin II and corticotropin releasing hormone, and regulation of P450(17) alpha mRNA. 269 45


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