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)

Thyropin binding to high affinity receptors on human and porcine membranes was studied at pH 7.4, 37 degrees C, in 10 mM Tris-HCl, 150 mM NaCl, 0.1% albumin. By preincubating the membranes in high salt concentration before binding studies, the number of high affinity receptors could be increased 4- to 8-fold. The salt-induced exposure of high affinity TSH receptors was pH- and temperature-dependent and was maximal at pH 5.0, 37 degrees C in the presence of 1 M (NH4)2SO4. Other salts tested, including NaCl, HN4Cl, and Na2SO4, were also able to increase high affinity THS binding. The receptors exposed by salt were indistinguishable from those present on the membranes before such treatment. They had an affinity constant of 0.5 to 1 X 10(10 M-1, and a high TSH specificity with no inhibition of 125I-TSH binding in the presence of a thousandfold excess of gamma-globulin, thyroglobulin, corticotropin, cholera toxin, and gangliosides. Thyrotropin binding to low affinity TSH binding sites (affinity constant 1 to 3 X 10(7) M-1) measured at pH 6.0, 4 degrees C in 10 mM Tris/acetate, 0.1% albumin was unaltered by pre-exposure of membranes to high salt concentrations. These receptors had low TSH specificity and binding was inhibited by gamma-globulin, thyroglobulin, cholera toxin, and gangliosides. The salt-induced selective exposure of high affinity receptors with unaltered number of low affinity sites is further support for the existence of two separate TSH binding sites on thyroid membranes.
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PMID:Salt-induced exposure of high affinity thyrotropin receptors on human and porcine thyroid membranes. 625 Oct 45

Cholera toxin catalyzed the ADP-ribosylation of the pituitary protein hormones thyrotropin (TSH), lutropin (LH), follitropin (FSH), human chorionic gonadotropin (hCG), and corticotropin (ACTH)1-24, and ADP-ribosylation of the basic proteins histone subfraction H1 and protamine. Casein and phosvitin, acidic nuclear proteins, did not act as acceptors for toxin-catalyzed ADP-ribosylation. The isolated TSH A and B subunits were tested for their ADP-ribose acceptor activity. The TSH A subunit showed fourfold greater ADP-ribose acceptor activity than the TSH B subunit. The ADP-ribose acceptor protein protamine was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis following incubation with cholera toxin under ADP-ribosylating conditions. [3H]ADP-ribose incorporated into protein from [3H]NAD migrated with the acceptor protein protamine. In the absence of added acceptor protein, the [3H]ADP-ribose incorporated into protein migrated with the A1 fragment of cholera toxin. Cholera toxin A and B subunits were isolated and tested for their ability to catalyze the transfer of ADP-ribose to protamine. The cholera toxin A subunit showed 50-fold greater ADP-ribosyltransferase activity than the B subunit. Our data indicate that a variety of adenohypophyseal hormones and regulatory proteins act as acceptors for toxin-catalyzed ADP-ribosylation. These studies may help in understanding the role of endogenous ADP-ribosyltransferases and the physiological effects of this modification of protein.
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PMID:Polypeptide hormones and chromatin-associated proteins act as acceptors for cholera toxin-catalyzed ADP-ribosylation. 625 55

Bovine thyroid membranes possess both ADP ribosyltransferase and NAD glycohydrolase activities with the same Km values for NAD and the same pH optima. In intact membranes, the ADP ribosyltransferase is limited in its extent by the amount of available membrane acceptor which can be ADP-ribosylated; in membranes solubilized with lithium diiodosalicylate, an artificial acceptor, L-arginine methyl ester, can be substituted to eliminate this limitation. The product of the ADP ribosyltransferase is a mono-ADP-ribosylated acceptor whether the intact or solubilized membrane provides the enzyme activity and whether membrane or exogenous acceptor, L-arginine methyl ester, is utilized. The intact membranes and the solubilized preparation also have an enzyme activity which can release AMP from the mono-ADP-ribosylated acceptor whether formed by the action of the membrane ADP ribosyltransferase or the A promoter of cholera toxin. The NAD glycohydrolase activity appears to represent the half-reaction of the ADP ribosyltransferase, i.e. an activity measurable substituting water for a membrane acceptor or L-arginine methyl ester. Membranes from functional rat thyroid cells in culture, i.e. cells chronically stimulated by thyrotropin and unresponsive to further additions of thyrotropin, have low ADP-ribosylation but high NAD glycohydrolase activities. In contrast, membranes from nonfunctional rat thyroid cells, i.e. cells unresponsive to thyrotropin, have high ADP-ribosylation and low NAD glycohydrolase activities. NAD hydrolysis by the NAD glycohydrolase activity cannot account for the low ADP-ribosylation activity in membranes from the functioning cells, and its low level of ADP-ribosylation can be eliminated by solubilizing the membranes and substituting an artificial acceptor, L-arginine methyl ester. The ADP ribosyltransferase activity of rat thyroid cell membrane preparations can be enhanced by thyrotropin in a dose-dependent manner but not by insulin, glucagon, hydrocortisone, adrenocorticotropin, or its glycoprotein hormone analog, human chorionic gonadotropin. It is thus suggested (i) that, in analogy to cholera toxin, thyrotropin-stimulated ADP-ribosylation may be important in the regulation of the adenylate cyclase response and (ii) that the level of membrane acceptor available for ADP-ribosylation may relate both to a stable "'activated" state of the adenylate cyclase system in cells chronically stimulated with thyrotropin and/or to a desensitized state with regard to a failure of more thyrotropin to elicit additional functional responses.
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PMID:Thyroid membrane ADP ribosyltransferase activity. Stimulation by thyrotropin and activity in functioning and nonfunctioning rat thyroid cells in culture. 627 80

Triphenylmethylphosphonium (TPMP+) partitions into the mitochondrial and cytosolic compartments in the rat white adipocyte in a potential-dependent fashion. The relationship between [3H]TPMP+ distribution, intracellular cAMP generation and lipolysis in response to hormones and cAMP-mimetic compounds was examined. Half-maximal [3H]TPMP+ efflux and glycerol release were produced by 15 and 9 nM adrenocorticotropin, 170 and 110 nM 1-epinephrine, 70 and 27 microM isobutylmethylxanthine and 800 and 750 microM dibutyryl cAMP, respectively. Hormone-stimulated cAMP generation was also correlated with [3H]TPMP+ efflux and lipolysis in terms of concentration dependency. In kinetic experiments, glycerol release and [3H]TPMP+ efflux in response to adrenocorticotropin or cholera toxin proceeded over a similar time course, whereas an earlier rise in cAMP generation was detected. The depolarizing effect of lipolytic compounds was localized to the mitochondrial compartment. When cells were incubated in elevated-[K+]0 buffer, the stimulatory effect of dibutyryl cAMP on [3H]TPMP+ efflux and lipolysis persisted, suggesting that maintenance of the plasma membrane potential is not critical for demonstration of these responses. When the extracellular concentration of serum albumin, which provides binding sites for free fatty acids, was increased from 1 to 3%, an increase in glycerol release and a decrease in [3H]TPMP+ efflux was observed. We suggest that intracellular free fatty acid accumulation in response to lipolytic agents causes dissipation of the mitochondrial membrane potential and efflux of [3H]TPMP+ from the organelle and cell.
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PMID:Triphenylmethylphosphonium cation distribution as a measure of hormone-induced alterations in white adipocyte membrane potential. 628 74

Forskolin, a unique diterpene which directly activates the adenylate cyclase, stimulated production of both cyclic AMP and corticosterone in isolated rat adrenal cells, in vitro. This agent also potentiated the action of adrenocorticotropin and/or cholera toxin on cyclic AMP production and steroidogenesis at lower concentrations. It augmented both an early (cyclic AMP production) and a late (steroidogenesis) action of the hormone in the adrenal gland.
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PMID:Forskolin potentiates adrenocorticotropin-induced cyclic AMP production and steroidogenesis in isolated rat adrenal cells. 628 44

The intermediate lobe of the rat pituitary gland is a homogeneous population of cells synthesizing and secreting various peptides related to ACTH and lipotropin derived from a common glycoprotein precursor, pro-opiocortin. The release mechanism of beta-endorphin from the pituitary gland has been reported by a few investigators, but the precise mechanism is still unknown. The receptors for a catecholamine present in the intact intermediate lobe of the rat pituitary gland remain functional on the enzymatically dispersed cells which secrete beta-endorphin-like immunoreactivity (beta-EPLI) and synthesize adenosine-3',5'-monophosphate (cAMP). Stimulation of beta-adrenoceptor with 1-isoproterenol enhances the synthesis of cAMP and accelerates the rate of beta-EPLI release. The ability of beta-adrenergic agonists to enhance the synthesis of cAMP appears to be causally related to the physiological response to beta-adrenergic agonists (i.e. enhanced beta-EPLI release). Phosphodiesterase inhibitors (theophylline, 3-isobutyl-1-methyl xanthine), cAMP analogs (dibutyryl-cAMP, 8-bromo-cAMP) and cholera toxin also increase beta-EPLI release. These findings suggest that cAMP may participate in this beta-EPLI release process. Furthermore, dopamine inhibits basal beta-EPLI release and also diminishes l-isoproterenol stimulated beta-EPLI release.
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PMID:[Mechanism of beta-endorphin release regulation--evaluation using dispersed cells of the pituitary intermediate lobe]. 631 22

Mouse B16 melanoma cells respond to melanocyte-stimulating hormone (MSH) or cholera toxin (CT) with an accumulation of cAMP. The kinetics and dose-response of MSH were examined in the B16 parent line and two cell clones derived from it that exhibited wheat germ agglutinin (WGA) resistance [1]. These WGA lectin-resistant cells, designated W4 and W5 showed a greater response to MSH and CT than the parent B16 cells. Exposure of the W4 and W5 cells to lotus lectin or ricin respectively, led to the previously described [2] selection of cell clones that were resistant to lotus lectin (W4L) and ricin (W5R). The W4L and W5R cells which were shown [2] to be as sensitive as the B16 parent to WGA (i.e., were phenotypically reverted to WGA sensitivity), were also found to respond to MSH in a manner similar to the B16 parent. Since lectin sensitivity has been directly correlated in these cell clones with the membrane's oligosaccharides and glycopeptide pattern, these data suggest that the cellular binding and/or biological response to hormones is influenced by the carbohydrate composition of the plasma membrane.
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PMID:Lectin-resistant B16 melanoma cells exhibit an altered response to MSH and cholera toxin. 631 64

To further elucidate the mechanisms by which ACTH (adrenocorticotropin) exerts its long-term action to maintain normal levels of adrenocortical cytochromes P-450 and related enzymes, the abilities of cholera toxin and prostaglandins E2 and F2 alpha to induce the synthesis of cytochromes P-450scc, P-45011 beta, and P-450C21 and adrenodoxin have been examined. These effectors stimulate the production of cyclic AMP and thus steroidogenesis in the adrenal cortex. Using bovine adrenocortical cells in primary monolayer culture, we have shown that treatment with cholera toxin results in increased synthesis of cytochromes P-450scc and P-45011 beta and adrenodoxin, similar to the effect observed upon ACTH treatment. Prostaglandins E2 and F2 alpha are less effective at inducing the synthesis of the mitochondrial cytochromes P-450, and do not seem to induce the synthesis of adrenodoxin. Furthermore, cholera toxin was found to be less effective at inducing the synthesis of microsomal cytochrome P-450C21 than ACTH, and no more effective than the prostaglandins. Thus, while it appears that elevation of cyclic AMP levels is a necessary step leading to increased synthesis of adrenocortical forms of cytochrome P-450, the detailed mechanism of this induction will be found to be different for each of the different enzymes.
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PMID:Induction of synthesis of bovine adrenocortical cytochromes P-450scc, P-45011 beta, P-450C21, and adrenodoxin by prostaglandins E2 and F2 alpha and cholera toxin. 632 96

Melanocyte cultures were established and maintained routinely in Ham's F-10 medium containing 12-O-tetradecanoyl-phorbol-13-acetate (TPA), isobutylmethylxanthine (IBMX), cholera toxin (CT) and fetal calf serum (FCS). Three serum substitutes (Ultroser-G, Nutridoma-Hu and Nutricyte-H) were tested in order to obtain a medium without FCS having a more constant composition. Melanocyte proliferation was examined in long-term culture experiments by in situ cell counts at different periods of time. Only with Ultroser-G (1-2%) was the proliferation of melanocytes maintained without both FCS and CT, whereas the addition of the other two serum substitutes resulted in stabilization of melanocyte densities in the cultures up to 28 days. In the medium containing 1% Ultroser-G and IBMX without TPA minimal or no increases in melanocyte density were found. Addition of basic fibroblast growth factor (bFGF, 1 ng/ml) to the medium without TPA resulted in a partial restimulation of growth in different experiments. In this system with 1% Ultroser-G and 1 ng/ml bFGF, IBMX could also be replaced by other factors (dbcAMP, LTC4 and a purified form of alpha-melanocyte stimulating hormone). The culture medium with 1% Ultroser-G containing TPA and IBMX is now used for routine melanocyte culture. In this medium TPA/IBMX can easily be replaced by bFGF/dbcAMP with optimal growth stimulation. The combination bFGF/alpha-MSH and other more physiological stimulators offers an alternative to study responses of melanocytes in culture with respect to proliferation, metabolism, and phenotype.
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PMID:Stimulation of cultured melanocytes in medium containing a serum substitute: Ultroser-G. 754 Jul 55

Human melanocytes, maintained on bovine corneal endothelium-derived extracellular matrix for at least 4 days in the absence of phorbol 12-myristate 13-acetate (PMA) and cholera toxin (CT), displayed increased tyrosinase activity when exposed to several pro-opiomelanocortin-derived (POMC) peptides. Melanocytes from 9 of 14 donors showed significantly increased tyrosinase activity after treatment with adrenocorticotropic hormone (ACTH; mean increase 320 +/- 107 (S.E.M.)% of control, P < 0.005), while melanocytes from 8 of 13 donors increased tyrosinase in the presence of diacetyl-melanocyte stimulating hormone (di-MSH; mean increase 223 +/- 31 (S.E.M.)% of control, P < 0.005). Maximal increases in tyrosinase were seen after treatment with 10(-10) M ACTH and with 10(-6) M di-MSH. In two cell cultures which showed tyrosinase stimulation, melanin synthesis was similarly increased in the presence of added POMC peptides. PMA but not CT increased tyrosinase activity in melanocytes cultured under these conditions. In the presence of staurosporine, an inhibitor of protein kinase C (PKC), the magnitude of the increase in tyrosinase due to PMA, ACTH and di-MSH was significantly reduced. These results indicate that tyrosinase activity in melanocytes from most human donors, under appropriate conditions, is susceptible to the stimulatory effects of POMC peptides, that ACTH is considerably more potent than di-MSH in this test system and that in human cells the PKC pathway may be important in modulating melanogenesis.
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PMID:Stimulation of tyrosinase in human melanocytes by pro-opiomelanocortin-derived peptides. 759 39


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