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)

Polyamines are a ubiquitous group of amines that play diverse biological roles. In the anterior pituitary, intracellular polyamine levels are reported to show diurnal changes, although the biological significance remains to be elucidated. In this study, we examined the effects of polyamines on the transcriptional activity of the rat pro-opiomelanocortin (POMC) gene using AtT20PL, a clone of the AtT20 cell line in which an approximately 0.7 kb of the rat POMC 5' promoter-luciferase fusion gene was stably incorporated. The results showed that three representative polyamines (putrescine, spermidine and spermine) all stimulated POMC promoter activity in a time- and dose-related manner, spermine showing the most potent effect (maximum approximate three-fold increase). This effect was not observed under treatment with actinomycin D, suggesting the effect of polyamine at the transcriptional level. On the other hand, methylglyoxal bis (guanylhydrazone), an inhibitor of polyamine synthesis, showed the opposite effect, further supporting the positive role of intracellular polyamines. Taken together, our findings suggest that polyamines are involved in the regulation of POMC gene expression (especially in terms of diurnal changes) in corticotroph cells. The precise molecular mechanisms of polyamine effects await further research.
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PMID:Polyamine regulation of the rat pro-opiomelanocortin gene expression in AtT-20 cells. 1157 27

Heterozygous coding mutations in the melanocortin 4 receptor (MC4R) are implicated in 1 to 6% of early onset or severe adult obesity cases. To better address the problem of the genotype:phenotype relationship within this specific form of obesity, we systematically studied the functional characteristics of 50 different obesity-associated MC4R mutations. Structure modeling of MC4R indicates that obesity-associated MC4R mutations are not localized in a single domain of the protein. We developed a flow cytometry-based assay to compare cell membrane expression of obesity-associated MC4R mutants. Using this assay, we demonstrate that over 54% of the obesity-associated MC4R mutations impair the membrane expression of MC4R. All other mutations impair the basal constitutive activity and/or the EC(50) for the physiological agonist alpha-MSH as measured in a cAMP- dependent luciferase assay. The extent of the alterations in receptor activity ranges from a total suppression of MC4R activation in response to alpha-MSH to a mild alteration of the basal constitutive activity of the receptor. Since most patients are heterozygous for MC4R mutations, these data indicate that a small decrease in overall MC4R activity can cause obesity, strongly supporting the hypothesis that the MC4R is a critical component of the adipostat in humans.
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PMID:Molecular genetics of human obesity-associated MC4R mutations. 1285 Dec 97

Corticotropin-releasing hormone is a main regulator of mammalian stress response by stimulating pituitary proopiomelanocortin (POMC) gene expression, and thus adrenocorticotropic hormone (ACTH) secretion, which then causes glucocorticoid release from the adrenal. In a recent study in the pituitary corticotroph cell line AtT20, oxidative stress stimulated the activity of nuclear transcription factor B (NF-kappaB), whereas corticotropin-releasing hormone (CRH) inhibited both the constitutive and the oxidative stress-induced NF-kappaB DNA-binding activity. To further investigate the role of NF-kappaB on the CRH-induced pituitary POMC gene activation, AtT20 cells were transiently transfected with a POMC-luciferase construct mutated at an NF-kappaB binding site. After treatment with CRH, intracellular POMC-luciferase activity was significantly higher from the stimulation observed with transfection of the parental POMC-luciferase construct. In agreement with a previous report, CRH inhibited the constitutive NF-kappaB DNA-binding activity in AtT20 cells, as shown by electrophoretic mobility-shift assay, as soon as within 15 min of treatment. These effects of CRH were blocked by the CRH-R1 antagonist CP154,256. Our findings provide evidence that the regulation of corticotroph NF-kappaB activity by CRH is related to the activation of the pituitary POMC gene and, thus, may play an important role in stress response.
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PMID:NF-kappaB participates in the corticotropin-releasing, hormone-induced regulation of the pituitary proopiomelanocortin gene. 1471 17

Although corticotropin-releasing hormone (CRH) plays a pivotal role in the regulation of the hypothalamo-pituitary-adrenal axis, the mechanism of CRH gene expression in the neuronal cell is not completely understood. In this study, we examined the transcriptional regulation of human CRH gene 5'-promoter, using a human BE(2)C neuroblastoma cell line expressing intrinsic CRH. In particular, we focused on the involvement of calmodulin kinases (CaMKs), which are known to play an important role in excitation-induced gene expression through the rise in intracellular calcium in the central nervous system. RT-PCR analysis confirmed the expression of CaMK as well as CRH mRNA in BE(2)C cells. When we introduced approximately 1.1 kb of the 5'-promoter region of the human CRH fused with luciferase reporter gene into the cells, a substantial transcriptional activity was observed, and this was further increased by the activation of the cAMP/PKA pathway. We then examined the effect of activation of CaMKs by introducing the expression vectors of each kinase, revealing a potent stimulatory effect of CaMKIV, but no effect of CaMKII. Depolarization of the cells caused an increase in CRH promoter activity, which was completely abolished by the treatment with the CaMK antagonist K252a. Interestingly, KCREB, a dominant negative form of CREB, antagonized the effect of the CaMKIV-mediated effect. Altogether, we conclude that not only the cAMP/PKA but also the calcium/CaMKIV signaling pathway is involved in the regulation of CRH gene expression. Furthermore, CREB is thought to be involved in CaMK- as well as cAMP/PKA-mediated CRH gene expression. Since the CRH gene is expressed in the neuronal cells of the hypothalamus, the calcium/CaMKIV signaling pathway may play an important role in the excitation-mediated regulation of CRH synthesis.
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PMID:Calcium/calmodulin kinase IV pathway is involved in the transcriptional regulation of the corticotropin-releasing hormone gene promoter in neuronal cells. 1559 Oct 24

Cytochrome P450c17, encoded by the CYP17 gene, is a component of the 17alpha-hydroxylase/17,20-lyase enzyme complex essential for production of adrenal glucocorticoids and androgens as well as gonadal androgens. The expression of CYP17 in adrenocortical cells is stimulated by corticotropin (ACTH) via the signal transduction pathway involving cAMP and protein kinase A (PKA). Thus, in addition to glucocorticoids, ACTH stimulates formation of adrenal androgens, which are known to induce transforming growth factor beta (TGF-beta) secretion. TGF-b in turn inhibits steroid hormone output by attenuating both basal and ACTH-dependent expression of CYP17. The present study revealed that treatment of bovine and human H295R adrenocortical cells with androgens resulted in a decrease in the basal level of CYP17 transcript and cortisol secretion, without affecting forskolin-stimulated levels. We also demonstrated that in H295R cells TGF-beta inhibited both basal and forskolin-stimulated accumulation of CYP17 mRNA. Determination of promoter activity, directing luciferase reporter gene expression in H295R cells transfected with deletion fragments of bovine CYP17 promoter, indicated that the -483 to -433 bp fragment of the promoter was necessary for the inhibitory action of TGF-beta on CYP17 expression. It is concluded that in bovine and human adrenocortical cells, androgens inhibit basal CYP17 expression probably at the transcriptional level and independently of the effect of TGF-beta.
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PMID:Inhibition of CYP17 expression by adrenal androgens and transforming growth factor beta in adrenocortical cells. 1562 62

Sphingolipids are a diverse family of phospholipids and glycolipids that mediate cell-cell interactions, participate in signal transduction pathways and modulate the activity of various cellular proteins and receptors. The objective of the present studies was to characterize the role of the sphingolipid biosynthetic pathway in adrenocorticotropin (ACTH)-dependent steroidogenic gene expression and cortisol production. H295R human adrenocortical cells were treated with ACTH or dibutyryl cAMP (Bt2cAMP) for various time periods and the content of sphingolipids was quantified by mass spectrometry. Treatment of H295R cells with ACTH and Bt2cAMP activated sphingolipid metabolism within five minutes. Decreases were found in the cellular levels of several sphingolipids, including sphingomyelin (SM) and glucosylceramide. ACTH/cAMP rapidly decreased levels of the signaling molecules ceramide, sphingosine and sphingosine-1-phosphate (S1P). The effect of these bioactive sphingolipids on steroidogenic gene expression was also examined. Both sphingosine and S1P were found to increase endogenous CYP17 mRNA and activate the transcriptional activity of CYP17-luciferase reporter constructs. Further, sphingosine and S1P rapidly increase cortisol biosynthesis in H295R cells. In summary, our studies establish a link between ACTH/cAMP-dependent steroidogenesis and sphingolipid metabolism in the human adrenal cortex. Finally, these findings suggest that sphingolipids may serve as signaling mediators in ACTH-stimulated cortisol biosynthesis.
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PMID:ACTH regulates steroidogenic gene expression and cortisol biosynthesis in the human adrenal cortex via sphingolipid metabolism. 1566 26

alpha-MSH is an anti-inflammatory peptide which signals by binding to the melanocortin-1 receptor (MC1R) and elevating cyclic AMP in several different cells and tissues. The carboxyl terminal peptides of alpha-MSH (KPV/GKPV) are the smallest minimal sequences that prevent inflammation, but it is not known if they operate via MC1R or cyclic AMP. The aim of this study was to examine the intracellular signaling potential of the GKPV peptide sequence when immobilized to polystyrene beads via a polyethylene glycol moiety. Beads containing an immobilized GKPV peptide were investigated for their ability to inhibit proinflammatory tumor necrosis factor-alpha (TNF-alpha) stimulated activation of NF-kappaB in HBL cells stably transfected with an NF-kappaB-luciferase reporter construct. Peptide functionalized beads were compared with the ability of soluble peptide alone (alpha-MSH or GKPV) or non-functionalized beads to inhibit TNF-alpha stimulated activation of NF-kappaB. GKPV peptide functionalized beads significantly inhibited NF-kappaB-luciferase activity in comparison to beads containing no peptide moiety in one of two growths conditions investigated. Soluble alpha-MSH and GKPV peptides were also confirmed to inhibit NF-kappaB-luciferase. The present study suggests that the carboxyl terminal MSH peptide acts via a cell receptor-based mechanism and furthermore may support the potential use of such immobilized ligands for anti-inflammatory therapeutic use.
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PMID:Immobilized alpha-melanocyte stimulating hormone 10-13 (GKPV) inhibits tumor necrosis factor-alpha stimulated NF-kappaB activity. 1627 45

Urocortin (UCN) is a 40 amino acid peptide which is closely related to corticotropin-releasing hormone and binds with high affinity to both CRH type 1 and type 2 receptors. UCN is expressed in human reproductive tissues including endometrium, ovary, and placenta. This study was designed to investigate the cellular localization of UCN at the implantation site of the human blastocyst, as well as the regulation of the UCN promoter by two major intracellular signaling pathways, the cAMP/PKA and diacylglycerol/PKC pathways, in cells of placental origin. For this reason, immunohistochemistry was performed on tissue sections from paraffin-embedded human first trimester placentas and freshly isolated human invasive extravillous trophoblast cells (EVT) were analyzed for UCN expression using RT-PCR and immunofluorescence. Finally, UCN promoter activity was analyzed in the JEG3 human choriocarcinoma cell line. Immunohistochemistry revealed expression of UCN in the cytotrophoblast, the EVT and decidual cells. Both UCN mRNA and peptide were detectable in freshly isolated EVT. Finally, a human UCN promoter luciferase reporter construct transfected into JEG3 cells was significantly inducible by phorbol ester plus ionomycin, but not by phorbol ester alone or by forskolin. Collectively, the present study reports the expression of UCN in EVT and the activation of the UCN gene promoter by the diacylglycerol/PKC pathway. The functional significance of urocortin for the physiology of EVT requires further investigation.
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PMID:Expression of urocortin in the extravillous human trophoblast at the implantation site. 1669 78

Recently, studies in adult rheumatoid arthritis patients have shown an association with four single-nucleotide polymorphisms (SNPs) in the 3.7-kb regulatory region of human corticotropin-releasing hormone (hCRH) gene located at positions -3531, -3371, -2353, and -684 bp. Three of these novel polymorphisms are in absolute linkage disequilibrium, resulting in three combined alleles, named A1B1, A2B1, and A2B2. To study whether the described polymorphic nucleotide sequences in the 5' region of the hCRH gene interfere with binding of nuclear proteins, an electric mobility shift assay (EMSA) was performed. At position -2353 bp, a specific DNA protein complex was detected for the wild-type sequence only, possibly interfering with a binding site for the activating transcription factor 6 (ATF6). In contrast, no difference could be detected for the other SNPs. However, at position -684, a quantitative difference in protein binding due to cAMP incubation could be observed. To further investigate whether these SNPs in the CRH promoter are associated with an altered regulation of the CRH gene, we performed a luciferase reporter gene assay with transiently transfected rat pheochromocytoma cells PC12. Incubation with 8-Br-cAMP alone or in combination with cytokines enhanced significantly the promoter activity in PC12 cells. The promoter haplotypes studied exhibited a differential capacity to modulate CRH gene expression. In all our experiments, haplotype A1B1 showed the most pronounced influence on promoter activity. Taken together, our results demonstrate a differential binding capacity of nuclear proteins of the promoter polymorphisms resulting in a different gene regulation. Most probably the SNP at position -2,353 plays a major role in mediating these differences.
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PMID:Sequence variants of the CRH 5'-flanking region: effects on DNA-protein interactions studied by EMSA in PC12 cells. 1685 32

Although it is known that the expression of proopiomelanocortin, a precursor protein of adrenocorticotropic hormone, can be affected by a variety of drugs, the effects of calcium channel blockers have not been studied. This study examined the effect of calcium channel blockers on proopiomelanocortin gene expression. Mouse pituitary tumor cells stably transfected with approximately 0.7 kb of the rat proopiomelanocortin 5' promoter-luciferase fusion gene were stimulated by potassium chloride, corticotropin-releasing hormone (CRH) or forskolin, in the presence or absence of calcium channel blockers (nifedipine, verapamil and diltiazem). Assessments were made of proopiomelanocortin gene promoter activity and cyclic adenosine 3',5'-monophosphate (cyclic AMP) efflux. A dose-dependent enhancement of CRH- or forskolin-stimulated proopiomelanocortin promoter activity was observed with nifedipine and verapamil, but not diltiazem. Cyclic AMP efflux induced by CRH or forskolin was also enhanced by nifedipine and verapamil. In the presence of isobutylmethylxanthine, a phosphodiesterase inhibitor, enhancement of proopiomelanocortin promoter activity and cyclic AMP efflux by nifedipine and verapamil was not observed. It was concluded that the inhibition of phosphodiesterase is a probable mechanism for the effect of nifedipine and verapamil on CRH or forskolin induction of proopiomelanocortin gene expression.
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PMID:Potentiation of cyclic AMP-mediated proopiomelanocortin gene promoter activity by calcium channel blockers in a pituitary cell line. 1719 58


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