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Query: UNIPROT:P01189 (beta-endorphin)
 21,003 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We undertook these studies to explore the intracellular signaling mechanisms activated by a newly described human brain melanocortin receptor (hMC3R). Hepa cells transfected with the hMC3R gene responded to stimulation with alpha-melanocyte stimulation hormone (alpha-MSH) and adrenocorticotropic hormone (ACTH) with dose-dependent increases in cellular content of cyclic 3',5'-adenosine monophosphate (cAMP) reaching a maximum of over 1500% of control cells at the 10(-8) M dose (EC50 = 10(-11) M). In contrast, the production of [3H]inositol phosphates in cells prelabeled with myo-[2-3H]inositol exhibited a biphasic dose-response curve with increases as high as 155% of basal at 10(-11) M alpha-MSH or ACTH, but beyond that a dose-dependent decrease was observed. The inhibitory component of the dose-response curve could be abolished by pretreatment of transfected cells with the cAMP antagonist (Rp)-adenosine 3',5'-monophosphorothioate (Rp-cAMP) or the protein kinase A inhibitor H-89. Increases in intracellular calcium induced in transfected cells by alpha-MSH in doses ranging from 10(-11) to 10(-7) M could not be observed unless the cells were pretreated with H-89. By replacing the third intracytoplasmic loop of the canine H2-histamine receptor with that of hMC3R the biphasic characteristic of agonist-induced production of [3H]inositol phosphates was conferred to the chimeric receptor. These data indicate that the hMC3R is coupled to both cAMP and inositol phospholipid/Ca(2+)-mediated post-receptor signaling systems and that the latter response is regulated by protein kinase A activity.
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PMID:Interaction of dual intracellular signaling pathways activated by the melanocortin-3 receptor. 817 43

Steroid 21-hydroxylase activity has been identified in many tissues, including liver. But it is possible that the enzyme found in the liver is different from adrenal 21-hydroxylase. In the adrenal cortex, steroid 21-hydroxylase activity is increased by corticotropin (ACTH); the effect of ACTH is mediated by cyclic AMP (cAMP), and presumably involves a cAMP-dependent protein kinase (PKA). It is not yet clear, however, how extra-adrenal steroid 21-hydroxylase activity is regulated. In the present study, we examined the effect of N6,2'-O-dibutyryl adenosine 3',5'-cyclic monophosphate (dbcAMP), forskolin, N-[2-(methylamino)ethyl]5-isoquinolinesulfonamide (H-8) and 12-O-tetradecanoylphorbol-13-acetate (TPA) on steroid 21-hydroxylase activity in primary cultures of rat hepatocytes to determine the nature of regulation of extra-adrenal steroid 21-hydroxylase activity. Steroid 21-hydroxylase activity in hepatocytes incubated with 10(-11) M dbcAMP for 24 h was 1.6 times higher than that in control hepatocytes untreated with dbcAMP. On the other hand, steroid 21-hydroxylase activity decreased by 20 and 50% when the cells were incubated with 10(-5) and 10(-3) M dbcAMP, respectively. The stimulatory effect of 10(-11) M dbcAMP was not blocked by 10(-5) M H-8 (PKA inhibitor), but the inhibitory effect of 10(-5) or 10(-3) M cAMP was. TPA did not alter the activity of steroid 21-hydroxylase. These findings indicate that the steroid 21-hydroxylase in rat liver is regulated by mechanisms different from those in the adrenal glands.
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PMID:Biphasic regulation by N6,2'-O-dibutyryl adenosine 3',5'-cyclic monophosphate (dbcAMP) of steroid 21-hydroxylase activity in rat hepatocytes. 818 Jan 19

The effect of the antidiarrheal drug loperamide, a mu-opiate agonist, on ACTH secretion and biosynthesis, cAMP generation and phosphoinositide turnover was studied in rat anterior pituitary cell cultures. The cAMP-dependent protein kinase A pathway was stimulated with both corticotropin-releasing hormone (CRH; 2-5 nM) and the membrane-permeable Bu(2)cAMP (0.5-2.5 mM). The protein kinase C pathway was stimulated with 1 microM arginine vasopressin (AVP) and 1-10 nM phorbol 12-myristate 13-acetate (PMA). After 3.5 h, loperamide (10 microM) had no effect on basal ACTH levels but significantly suppressed CRH-induced ACTH release, in a dose-dependent manner, to 60 +/- 4% of control (100%) (p < 0.0001). After 24 h, basal proopiomelanocortin mRNA was significantly decreased to 50% of control by loperamide (p < 0.05). The suppressive effect of loperamide on CRH-induced ACTH secretion was not reversible by naloxone (0.1-1,000 microM). Morphine (0.01-10 microM) had no effect on basal and CRH-induced ACTH secretion. Loperamide did not influence basal and CRH-induced adenylate cyclase activity in anterior pituitary cell membrane preparations, but it significantly blunted Bu(2)cAMP-induced ACTH secretion in cell culture from 100 +/- 4 to 77 +/- 4% (p < 0.05). In Ca(2+)-depleted medium (Ca2+ < 0.1 mM), loperamide had no suppressive effect on CRH-induced ACTH secretion. AVP-induced ACTH secretion was significantly suppressed by loperamide from 100 +/- 5 to 74 +/- 3% (p < 0.0001), while basal and AVP-induced inositol 1-phosphate generation and PMA-induced ACTH secretion were not affected by loperamide.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Loperamide inhibits corticotrophic cell function by a naloxone-insensitive mechanism in the rat in vitro. 823 60

We demonstrate that granular cerebellar neurons express functional corticotropin-releasing hormone (CRH) receptors. Activation of these receptors with CRH receptor agonists leads to a dose-dependent increase in cyclic AMP (cAMP) levels with an apparent EC50 close to 10(-9) M. Using the c-fos protooncogene as a system to evaluate genomic effects of CRH, we show that activation of CRH receptors regulates gene expression at the transcriptional level. CRH rapidly induced c-fos mRNA accumulation. Genetic studies, using chimera genes containing human c-fos promoter sequences coupled to a chloramphenicol acetyltransferase (CAT) reporter gene, confirmed and extended this observation. When protein kinase A (PKA) was specifically inactivated by gene transfer of a mutated regulatory subunit of PKA lacking cAMP binding sites, CRH-stimulated c-fos transcription was suppressed but the increase in cAMP level was not affected, indicating a key role of PKA in mediating CRH-stimulated transcription. As CRH clearly modulates gene expression via the cAMP pathway, we analyzed the genomic effect of this neurohormone on a deleted c-fos-CAT construct containing only the cAMP-responsive element (CRE) and on a heterologous promoter construct bearing the minimal palindromic consensus CRE (core sequence TGACGTCA). These minimal cAMP-responsive genes are induced by CRH. These inductions are dependent on functional PKA. Taken together, our results demonstrate the presence of functional CRH receptors in primary cerebellar cultures. Activation of these receptors stimulates gene expression via the cAMP/PKA pathway and the transacting factor CREB (cAMP-responsive element binding protein).
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PMID:Characterization and genetic analysis of functional corticotropin-releasing hormone receptors in primary cerebellar cultures. 838 Apr 41

Activation of protein kinase-C (PKC) has been reported to modify a variety of receptor-ligand interactions, including that of tumor necrosis factor alpha with immune cells. Thus, we studied the effect of phorbol esters on the binding of beta-endorphin to naloxone-resistant receptors on the promonocyte-like U937 cell line. After incubating intact U937 cells with phorbol 12-myristate 13-acetate (PMA, 100 nM) at 22 degrees C for 30 min, the specific binding of 125I-beta-endorphin was maximally reduced by approximately 40%. Only PMA (10-150 nM), and not the biologically inactive phorbol, 4 alpha-phorbol 12,13-didecanoate, caused this rapid, dose-dependent down-regulation. PMA did not interfere with the radioreceptor assay nor did it induce down-regulation when incubated with cell membrane. Scatchard analysis revealed that PMA significantly reduced both the number of receptors and Kd (10,640 receptors/cell and Kd = 2.9 +/- 0.1 nM for control vs. 4,868 receptors/cell and Kd = 1.5 +/- 0.7 nM for 150 nM PMA). The effect of PMA was abolished by preincubating cells with the inhibitors of PKC, N-(2-aminoethyl)-5 isoquinolinesulfonamide or 1-(5-isoquinolinyl-sulfonyl)-2-methylpiperazine. Down-regulation was reversible; removing 100 nM PMA from the media partially restored binding by 3 h and completely by 24 h. At 22 degrees C, internalization of 125I-beta-endorphin was not observed, and this was not altered by PMA.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Activation of protein kinase C rapidly down-regulates naloxone-resistant receptors for beta-endorphin on U937 cells. 838 Aug 63

Corticotropin-releasing factor (CRF) stimulates adrenocorticotropin (ACTH) release via the adenylate cyclase/cAMP-dependent protein kinase system. Because calcium is necessary for receptor-mediated release of ACTH, we have examined the effect of CRF on 45Ca2+ uptake in a corticotroph cell line model, AtT-20. Treatment of AtT-20 cells with CRF (10(-9)-10(-6) M) resulted in dose- and time-dependent increases in 45Ca2+ uptake, up to 2.2-fold above control values. The effect was statistically significant at 1 min and persisted for at least 10 min. Treatment with forskolin (1-30 microM), 8-Br-cAMP (0.5 mM), cholera toxin (CT, 100 ng/ml) and K+ (20 mM) also increased cell-associated 45Ca2+. The effect of K+ was completely blocked by nifedipine (100 microM), whereas the effects of CRF (10(-8) M) were only partially inhibited by this calcium channel antagonist. These data suggested a role of voltage-dependent calcium channels in 45Ca2+ uptake. Short term pretreatment (1-2 h) of AtT-20 cells with CRF (10(-8) M) significantly desensitized both CRF-stimulated cAMP accumulation and ACTH release, but did not attenuate CRF-stimulated 45Ca2+ uptake. Pretreatment with CRF (10(-8) M) for 4 h did not alter CT- or forskolin-stimulated cAMP accumulation and ACTH release. This suggests that the molecular mechanisms of desensitization are proximal to adenylate cyclase. Conversely, long term pretreatment (24 h) of AtT-20 cells with CRF (10(-8) M) induced significant desensitization of CRF-stimulated 45Ca2+ uptake. These results indicate that CRF stimulates calcium uptake in AtT-20 cells via cAMP-dependent and cAMP-independent mechanisms, and that the cellular mechanisms involved in desensitization of cAMP accumulation and ACTH release and those involved in desensitization of calcium uptake are qualitatively different.
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PMID:Corticotropin-releasing factor (CRF) stimulates 45Ca2+ uptake in the mouse corticotroph cell line AtT-20. 838 2

Besides acting as an important cofactor in the biosynthesis of catecholamine, ascorbic acid (AA) also modulates the activity of peptidyl-glycine alpha-amidating monooxygenase for the post-translational modification of neuropeptides such as alpha-MSH and TRH. We report here a novel action of AA in modulating the secretion and mRNA expression of atrial natriuretic factor (ANF) in rat hypothalamic neurons. Primary cultures of hypothalamic neurons from neonatal rats as previously described were employed in the present studies. Six days after plating, cultures were replenished with serum free media and incubated with vehicle or various doses of AA, alone or in the presence of forskolin. Treatment with AA alone significantly increased irANF secretion from the cultures in a time-related and a dose-dependent manner with an ED50 of approximately 3 microM and an Emax of 100 microM. At the concentration of 10 microM, AA augmented irANF release approximately 3 fold that of the controls (55 +/- 7 pg/well; mean +/- SE, n = 3; P < 0.01), but it failed to affect the abundance of pro-ANF mRNA in the cultures. However, 10 microM of AA markedly enhanced forskolin-induced irANF secretion and pro-ANF mRNA abundance of the cultured cells. This potentiating effect of AA on forskolin stimulation showed a good parallelism to the levels of cAMP produced in the hypothalamic cultures. We thus conclude that AA acts alone or in synergism with forskolin to stimulate the secretion and production of ANF in rat hypothalamic neurons; this latter effect may operate at the genomic level and is mediated, at least in part, through the protein kinase A dependent pathway.
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PMID:Ascorbic acid enhances forskolin-induced cyclic AMP production and pro-ANF mRNA expression of hypothalamic neurons in culture. 838 16

The melanocyte-stimulating hormone (alpha-MSH) used at 10(-6)-5 x 10(-8) M concentrations inhibited the growth of amelanotic cells of human malignant melanoma BRO and influenced cell morphology without any effect on melanization or tyrosinase activity. Inhibition of tumour cell growth was accompanied by marked elevation of intracellular cAMP levels but not that of cGMP. Dibutyryl-cAMP and the cAMP-dependent protein kinase A inhibitor also inhibited the cell growth. alpha-MSH increased mono-, di- and 1.4.5-myoinositol triphosphate concentrations and influenced the activities of phosphatidylinositol kinase and phosphatidylinositol-4-phosphate kinase determining phosphatidylinositol-4-phosphate kinase and phosphatidylinositol-4.5-diphosphate levels. Myoinositol phosphate concentrations changed on a second scale and levelled off by the 3rd-5th min, whereas that of cAMP increased drastically by the 30th min.
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PMID:[Melanocyte-stimulating hormone induces growth of human malignant melanoma amelanotic cells with a change in cAMP, phosphatidylinositols, and inositol phosphate concentration]. 838 47

We have previously purified a transcription factor, PO-B, whose DNA binding capacity is increased by dephosphorylation and which contributes significantly to the basal transcription of genes such as pro-opiomelanocortin (Wellstein A., et al., J. Biol. Chem., 266: 12234-12241, 1991). In the present study, we describe several new properties of PO-B which suggest that the function of this transcription factor is not confined to regulation of gene expression in the pituitary. Furthermore, we present the first evidence for a signal transduction pathway that modulates the interactions of PO-B with DNA. We detected PO-B DNA binding activity in a number of mammalian cell lines (HeLa, C127, and AtT-20). However, PO-B was undetectable in extracts from undifferentiated HL-60 (U-HL-60) and CV-1 cells. Further characterization of these PO-B-negative extracts, by mixing experiments with PO-B-positive extracts, revealed that the U-HL-60 extracts, but not CV-1, contained enzymatic activity capable of increasing the mobility of the PO-B-DNA complex on nondenaturing gels. Concomitantly, there was also a reduction in the overall amount of PO-B bound to its cognate element. Immunoprecipitation with an antiserum to the protein kinase ERK 1 removed the modulatory activity from the U-HL-60 extracts, as did incubation with an ERK substrate peptide. Whole cell extracts from HL-60 cells which had been treated for 96 h with the macrophage-differentiating phorbol ester 12-O-tetradecanoylphorbol-13-acetate contained no modulatory activity. Furthermore, PO-B could be detected in these extracts. We conclude that an ERK or ERK-regulated protein in U-HL-60 cellular extracts regulates PO-B DNA binding and that some portion of the increase in PO-B DNA binding during HL-60 differentiation may arise from alterations in this regulatory activity.
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PMID:DNA binding of the transcription factor PO-B is regulated during differentiation of HL-60 cells. 839 6

This review highlights contributions from my laboratory in which the sites and mechanisms of action of the adrenocorticotropic hormone (ACTH) in the adrenal cortex have been explored. Early studies showing that ACTH stimulates adrenal steroidogenesis by interacting with specific receptors at the cell surface are summarized. Next, the development of a strategy of genetic analysis to define the signalling events that follow ACTH interaction with its receptor is described. This strategy involved the isolation and characterization of mutant adrenal cell lines harboring specific defects in the ACTH-responsive steroidogenic pathway. I describe the isolation and characterization of several of these mutants and demonstrate how these mutants have helped to establish obligatory roles for adenylyl cyclase, cyclic AMP (cAMP), and cAMP-dependent protein kinase in the steroidogenic actions of ACTH. Finally, some of our studies on the regulated expression of the steroidogenic cytochrome P450 enzymes in Y1 adrenal cells are reviewed. These latter studies have led to the discovery of a novel promoter element and transcription factor (designated steroidogenic factor 1) that participates in the coordinate expression of these cytochrome P450 enzymes and that is required for their regulated expression by ACTH and cAMP.
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PMID:The 1994 Upjohn Award Lecture. Molecular and genetic approaches to the study of signal transduction in the adrenal cortex. 856 76


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