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)

In homogenate of rat olfactory bulb, the opioid receptor agonists beta-endorphin, Leu-enkephalin, and dynorphin A stimulated adenylate cyclase activity in a concentration-dependent manner, with half-maximal effects displayed at 22, 63, and 176 nM, respectively. The maximal stimulation of the enzyme activity corresponded to about a 40% increase of basal activity for all three peptides. Naloxone antagonized the stimulation of beta-endorphin, Leu-enkephalin, and dynorphin A, with pA2 values of 8.0, 7.7, and 8.1, respectively. Kinetic analysis performed with Leu-enkephalin showed that the opioid peptide increased the Vmax of the enzyme, without changing the Km for the substrate Mg-ATP. Moreover, the opioid stimulation was associated with a significant increase of the affinity of the enzyme for Mg2+ activation and occurred in membranes incubated in a Ca2(+)-free medium. Addition of exogenous GTP at micromolar concentrations was absolutely necessary for the detection of the opioid effect. Treatment of olfactory bulbs with cholera toxin did not alter the stimulation of adenylate cyclase by Leu-enkephalin. However, the opioid stimulation disappeared in membranes obtained from bulbs injected with pertussis toxin. These results demonstrate the presence in the brain of a new functional class of opiate receptors coupled to stimulation of adenylate cyclase via a transduction mechanism that is Ca2+ independent and seems to involve a pertussis toxin-sensitive GTP-binding protein.
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PMID:Naturally occurring opioid receptor agonists stimulate adenylate cyclase activity in rat olfactory bulb. 167 23

Some of the functional effects of beta-endorphin on immune cells are resistant to inhibition by naloxone. To further characterize the beta-[125I]endorphin-binding site mediating these effects and its response to cations and GTP, the human monocyte-like cell line U937 was used. Incubation of intact cells and beta-[125I]endorphin for 60 min at 4 C demonstrated a saturable, high affinity binding site [Kd = 1.2 +/- 0.5 X 10(-8) M (mean +/- SE; n = 4] competed by equimolar beta-endorphin and N-acetyl (Ac)-beta-endorphin but not by naloxone, morphine, or selective opiate receptor agonists. Competition studies showed that beta-endorphin-(6-31) and beta-endorphin-(28-31) were approximately 5- and 100-fold less potent, respectively, whereas beta-endorphin-(1-16) or -(1-27) was ineffective. Covalent cross-linking of beta-[125I]endorphin to intact cells and resolution by gel electrophoresis showed dominant bands at 59K and 44K and a minor band at 66K. The bands at 44K and 66K were completely displaced by increasing equivalent concentrations of beta-endorphin and N-Ac-beta-endorphin. Increasing concentrations of mono (Na+, K+)- and divalent (Ca2+, Mg2+, Mn2+) cations reduced the binding of beta-[125I]endorphin to U937 membrane; beta-[125I]endorphin binding to rat brain membrane showed similar cation sensitivity. GTP gamma-sulfate (GTP gamma S; 10(-4) M) alone reduced binding to U937 membrane by 25%. In the presence of Na+ (100 or 150 mM) or Mg2+ (10 mM), GTP gamma S reduced binding by an additional 50%. Moreover, GTP gamma S (10(-8)-10(-4) M) in the presence of Na+ (100 mM) reduced binding in a dose-dependent manner, whereas GMP was ineffective. In conclusion, beta-endorphin binds to sites on human U937 cells similar to those observed on normal murine splenocytes. Although naloxone insensitive, these sites exhibit properties, such as size, salt sensitivity, and coupling to a GTP-binding protein, that are similar to those observed for agonist binding to brain opiate receptors.
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PMID:Beta-endorphin binding to naloxone-insensitive sites on a human mononuclear cell line (U937): effects of cations and guanosine triphosphate. 216 44

Delta-opiate receptors have been solubilized with the non-ionic bile salt detergent digitonin from NG108-15 cell membranes and reconstituted into lipid vesicles. Specific opiate binding was restored to soluble receptor preparations after supplementation with a brain lipid extract, and dilution below the effective detergent concentration. Saturable and specific opiate binding was measured for both membrane and vesicle preparations; dissociation constants (Kd) obtained from saturation isotherms of [3H]bremazocine binding were 1.3 and 4.2 nM, respectively. Relative affinity (IC50) values of ligand binding measured for subtype-selective agonists confirmed that a delta-opiate binding site interaction was recovered in vesicle preparations. Changes in agonist binding affinity noted for these experiments were explained by dissociation of the GTP-binding protein Gi from the receptor in detergent. The recovery of solubilized opiate receptors was nearly quantitative, and strictly dependent upon the total brain lipid preparation used in the reconstitution. Ligand binding was incompletely recovered after substituting pure, vesicle-forming phospholipid preparations. [3H]Bremazocine binding was also reconstituted after lectin affinity chromatography of solubilized receptor preparations, using conditions which likely effect the removal of endogenous lipid cofactors. A photoaffinity cross-linking methodology was employed to verify recovery of the delta-opiate receptor after its solubilization from membranes and reconstitution. Two membrane-associated proteins (50 and 70 kDa) were covalently tagged with an azido analog of beta-endorphin(Leu5) in cell membranes and subsequently identified by immunoblotting with antisera directed against this opioid. Labeling of the 50-kDa polypeptide was prevented by coincubating assay samples with a relative excess of (D-Pen2,5)enkephalin. This opioid binding polypeptide was also present in solubilized/reconstituted receptor preparations.
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PMID:Reconstitution of solubilized delta-opiate receptor binding sites in lipid vesicles. 216 3

Somatostatin activates an inwardly rectifying potassium conductance in AtT-20 clonal corticotrophs, a cell line derived from the mouse pituitary gland. The action of somatostatin is blocked by pertussis toxin indicating that a GTP-binding protein couples the somatostatin receptor to the potassium channel. The potassium conductance is depressed by cesium. Cesium also attenuates the suppression of adrenocorticotropin hormone secretion by somatostatin suggesting that the increase in potassium conductance plays a role in this action of somatostatin.
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PMID:A potassium conductance contributes to the action of somatostatin-14 to suppress ACTH secretion. 289 64

The non-hydrolyzable GTP analogue, guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) and cyclic AMP potentiated the Ca2+-evoked secretion of alpha-melanocyte-stimulating hormone (alpha-MSH) from permeabilized neurointermediate lobe (IL) cells of rat pituitary gland. The enhancement by Mg-GTP gamma S (100 microM) and cyclic AMP (1 microM) depended on the intracellular Ca2+ concentration (EC50 = 4.8 +/- 1.8 and 4.6 +/- 1.7 microM; mean +/- SE, with and without Mg-GTP gamma S and cyclic AMP, respectively). A similar effect was observed with guanine nucleotide triphosphate (GTP and GppNHp). Mg was absolutely required for this event. Neither Mg-GTP gamma S nor cyclic AMP alone was effective in potentiating alpha-MSH secretion. GDP beta S blocked the Mg-GTP gamma S (100 microM) and cyclic AMP augmented secretion of alpha-MSH. Neither neomycin (which affects the process of inositol 1,4,5-triphosphate-mediated Ca2+ mobilization) or colchicine (which influences microtubule assembly) had an effect on the cyclic AMP and Mg-GTP gamma S potentiation of alpha-MSH secretion. These data suggest that the GTP-binding protein may be involved in the regulation of alpha-MSH secretion after Ca2+ entry into the cells, since the intracellular environment is controlled in the permeabilized cells.
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PMID:Alpha-melanocyte-stimulating hormone secretion from permeabilized intermediate lobe cells of rat pituitary gland. The role of guanine nucleotides. 360 97

Incubation of bovine hippocampal membranes with [alpha-32P]GTP and exposure to ultraviolet light resulted in the labelling of seven species with apparent molecular masses of 200, 74, 55, 53, 50, 43 and 40 kDa. Labelling of the 55 kDa species was greatly enhanced in the presence of carboxyl terminal fragments [neuropeptide Y-(18-36)] of neuropeptide Y. Labelling occurred with [alpha-32P]GTP but not [alpha-32P]ATP. A group of putative direct G protein activating peptides including mastoparan, melittin, substance P and adrenocorticotropic hormone (ACTH)-(1-24), were also able to stimulate the labelling of this protein. Labelling of the 55 kDa protein could be demonstrated in bovine brain but not peripheral tissues. Western blot analysis using an antibody against the common alpha subunit of G proteins recognized a protein co-migrating with the 55 kDa GTP-binding protein. These findings demonstrate the existence of a previously uncharacterized neuronal protein, with an apparent molecular mass of 55 kDa, that binds GTP in response to neuropeptide Y and other peptides.
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PMID:Neuropeptide Y promotes GTP photo-incorporation into a 55 kDa protein. 780 55

The mechanism of the adrenal corticotropin hormone (ACTH)-stimulated increase in cytosolic free Ca2+ concentration ([Ca2+]i) was investigated in rat white adipocytes. ACTH at concentrations > 10 mU/ml caused a rapid and transient increase in [Ca2+]i followed by a small but sustained elevation of [Ca2+]i. A similar phenomenon was also induced by alpha-adrenergic or synthetic ACTH stimulation. The effect of norepinephrine (NE) plus ACTH on [Ca2+]i was nearly additive. Pertussis toxin completely blocked the ability of ACTH or NE to increase [Ca2+]i. NE but not ACTH caused a significant increase in inositol 1,4,5-trisphosphate levels. ACTH caused a rapid and transient accumulation of [3H]arachidonic acid (AA) and a marked loss of [3H]AA from phosphatidylinositol (PI) and phosphatidylcholine (PC) 10 s after stimulation. Neither a lipoxygenase inhibitor nor a dual inhibitor of cyclooxygenase and lipoxygenase blocked the increases in [Ca2+]i and the accumulation of [3H]AA in response to ACTH. On the other hand, either pertussis toxin or phospholipase A2 inhibitor drastically blocked both parameters in response to ACTH. These results indicate that ACTH stimulates AA release from PC and PI via the activation of phospholipase A2 coupled with pertussis toxin-sensitive GTP-binding protein(s), which leads to an increase in [Ca2+]i in rat white adipocytes.
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PMID:Increase in cytosolic free Ca2+ in corticotropin-stimulated white adipocytes. 816 62

We reported previously that in homogenates of rat olfactory bulb muscarinic and opioid receptor agonists stimulate adenylyl cyclase activity. In the present study we show that carbachol (CCh) and Leu-Enkephalin act synergistically with vasoactive intestinal peptide (VIP) and corticotropin-releasing hormone (CRH), but not with l-isoproterenol, in increasing cyclic AMP formation. The synergistic interaction consists of an increase in the maximal adenylyl cyclase activation without a significant change in the potency of each agonist. CCh also fails to affect 125I-CRH binding to olfactory bulb membranes. The synergism requires micromolar concentrations of GTP. Substitution of the stable GTP analog guanosine 5'-O-(3'-thiotriphosphate) for GTP allows the CRH stimulation, but abolishes the CCh enhancement of both basal and CRH-stimulated enzyme activities. Moreover, in vivo treatment of olfactory bulbs with pertussis toxin completely prevents the muscarinic and opioid effects. Thus, the synergistic interaction appears to result from opioid- and muscarinic-induced activation of a pertussis toxin-sensitive GTP-binding protein which may potentiate the adenylyl cyclase stimulation by the stimulatory GTP-binding protein activated by either VIP or CRH receptors.
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PMID:Synergistic interaction of muscarinic and opioid receptors with GS-linked neurotransmitter receptors to stimulate adenylyl cyclase activity of rat olfactory bulb. 824 71

We investigated non-genomic mechanisms of glucocorticoid negative feedback regulation on pituitary corticotroph cells using the AtT20 mouse corticotroph tumor cell line. A synthetic glucocorticoid dexamethasone (100 nM) potently suppressed forskolin-induced cAMP generation, adrenocorticotropin (ACTH) secretion, and proopiomelanocortin gene expression. When de novo gene expression was inhibited by actinomycin D (1 microM), dexamethasone still suppressed cAMP efflux and ACTH release, although less potently. Interestingly, under the same conditions, pretreatment of the cells with pertussis toxin (50 ng/ml) completely abolished the suppressive effect of dexamethasone on both parameters. These results suggest that non-genomic and genomic mechanisms are involved in the glucocorticoid negative regulation of ACTH expression, and a pertussis toxin-sensitive GTP-binding protein might, at least partly, participate in the non-genomic effect.
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PMID:Non-genomic mechanisms of glucocorticoid inhibition of adrenocorticotropin secretion: possible involvement of GTP-binding protein. 919 85