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)

We investigated changes during the estrous cycle in cellular levels of corticotropin-releasing hormone (CRH) mRNA in parvocellular neurons of the hypothalamic paraventricular nucleus, using in situ hybridization. Intact female rats with 4 day cycles were sacrificed at 11 different times during the cycle at 09.00 h and 16.00 h on each day, with additional collection times at 14.00 h, 18.00 h, and 20.00 h on the day of proestrus. Twelve microns coronal sections of fresh-frozen brains were made through the paraventricular nuclei (PVN) and placed on gelatin-coated slides. A 48 base oligodeoxynucleotide probe complementary to the coding region for rat CRH was used to measure CRH mRNA. There was a sharp increase (P less than 0.01) in CRH mRNA in the ventral PVN between 14.00 and 16.00 h on the day of proestrus, at the approximate time of the ovulatory surge. Following this rise, there was an even larger decline (P less than 0.01) between P 16.00 h and P 20.00 h. Levels of CRH mRNA did not change greatly on other days of the cycle, nor were there significant changes in the dorsal PVN. Given the known effects of CRH on GnRH secretion, these changes occur at a time when they could serve to modulate the midcycle luteinizing hormone (LH) surge.
Brain Res Mol Brain Res 1990 Aug
PMID:Corticotropin releasing hormone mRNA is elevated on the afternoon of proestrus in the parvocellular paraventricular nuclei of the female rat. 217 Aug 4

Previous studies have demonstrated that TRH is a potent stimulator of alpha-MSH secretion from frog pituitary melanotrophs. In order to determine the intracellular events responsible for TRH-evoked alpha-MSH release, we have investigated the effect of TRH on polyphosphoinositide breakdown in frog pars intermedia. Neurointermediate lobes were labelled to isotopic equilibrium with myo-[3H]inositol. TRH stimulated the rate of incorporation of [3H]inositol into the phospholipid fraction. The effect of TRH was concentration-dependent; half-maximal stimulation of alpha-MSH release and inositol incorporation occurred at 12 and 28 nmol TRH/l respectively. In prelabelled neurointermediate lobes, lithium (10 mmol/l) enhanced the radioactivity in inositol monophosphate, bisphosphate (IP2) and trisphosphate (IP3). LiCl (10 mmol/l) induced a 38% inhibition of alpha-MSH release from perifused neurointermediate lobes but did not impair TRH-induced alpha-MSH secretion. In the presence of LiCl, TRH (1 mumol/l) induced a transient increase of the radioactivity in IP3, which was evident by 30 s and maximal by 1 min (+100%). TRH treatment also increased the radioactivity in IP2, which reached a plateau after 5 min (+100%). The increase in radioactivity in IP3 induced by TRH was closely paralleled by a rapid loss of [3H]phosphatidylinositol bisphosphate (PIP2), which was maximal by 1 min (-70%). These results indicate that, in frog pars intermedia, TRH-evoked alpha-MSH secretion is coupled to breakdown of PIP2. The data suggest that, in amphibian melanotrophs, as previously shown in GH3 tumour cells and in rat pituitary mammotrophs, TRH causes rapid stimulation of polyphosphoinositide-hydrolysing phospholipase C.
J Mol Endocrinol 1990 Oct
PMID:Thyrotrophin-releasing hormone stimulates polyphosphoinositide metabolism in the frog neurointermediate lobe. 217 40

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.
Mol Endocrinol 1990 Nov
PMID:In vitro and in vivo analysis of the processing and fate of the peptide products of the short proopiomelanocortin mRNA. 217 42

Beta-endorphin was detected by immunocytochemistry in motoneurons from mouse embryo spinal cord enriched by differential sedimentation and plated onto cultures of embryonic astrocytes from appropriate (cord) and inappropriate (cerebral cortex) sources. Growth of motoneurons on astrocytes for 5 d in vitro improved cell differentiation and suppressed beta-endorphin immunoreactivity. Immunoreactivity was suppressed to a greater degree in motoneurons plated onto cortical rather than spinal cord astrocytes. Some small, dense spinal cord cells also exhibited beta-endorphin immunoreactivity, but staining was unaffected by cultivation on astrocytes. Cell contact and/or hormonal factors deriving from glia may contribute to the regulation of beta-endorphin, a trophic neuropeptide conditionally expressed in normal and pathologic motoneurons.
Mol Chem Neuropathol 1990 Jan
PMID:Immunocytochemical detection of beta-endorphin in mouse spinal motoneurons cocultured with astrocytes from spinal cord and forebrain. 227 4

Proteolytic processing of polyprotein precursors at pairs of basic amino acids is a prerequisite for the generation of bioactive peptide hormones. While the mammalian endoproteases responsible for these cleavages are yet to be identified, this function has been unequivocally assigned in yeast to the product of the KEX-2 gene. To study the molecular mechanisms involved in polyprotein processing, we have transfected the yeast KEX-2 gene into mouse NIH 3T3 fibroblasts and established a new cell line (called 2N-DK) where the KEX-2 endoprotease is permanently expressed. Immunofluorescence studies show that the KEX-2 enzyme is retained within the Golgi of the 2N-DK cells. The evidence for this cellular location is supported by measurement of intracellular and extracellular KEX-2 enzyme activity. In this permanently transfected cell line, KEX-2 activity is exclusively intracellular, in contrast to the situation previously described in transiently infected cell lines, where extracellular KEX-2 activity was detected. Furthermore, infection of 2N-DK cells with a recombinant retrovirus expressing a cDNA coding for porcine proopiomelanocortin (POMC) resulted in the synthesis of POMC and its efficient processing into beta-lipotropin and beta-endorphin, two of its physiologically authentic maturation products. These results suggest that in the fibroblast cell line 2N-DK, proteolytic processing of POMC by KEX-2 endoprotease occurs in the Golgi apparatus.
Mol Endocrinol 1990 Oct
PMID:The yeast KEX-2-processing endoprotease is active in the Golgi apparatus of transfected NIH 3T3 fibroblasts. 228 1

The role of protein phosphorylation in MSH-induced melanogenesis was investigated with an in vivo phosphorylation assay using intact cultured Cloudman S91 mouse melanoma cells preincubated with [32P]orthophosphate. Exposure of the cells to alpha-MSH increased the extent of labelling of two protein bands on SDS gel electrophoresis with estimated molecular weights of 43 and 34 kDa, respectively. The 32P incorporation was concentration-dependent and reached a maximal value at 10(-8) M alpha-MSH for the 43 kDa band (156% of controls) and at 10(-5) M alpha-MSH for the 34 kDa band (250% of controls). The corresponding ED50s were 5 X 10(-10) M (43 kDa) and 3 X 10(-8) M (34 kDa). The 32P incorporation into the 34 kDa band reached a maximum after a 5 min exposure to alpha-MSH whereas 43 kDa phosphorylation was maximal after a 30-60 min incubation with hormone. The effect was completely reversible after removal of the hormone and specific for melanotropic peptides. Dibutyryl cAMP (10(-3) M) and forskolin (10(-4) M) together with isobutylmethylxanthine (10(-4) M) mimicked the effect of alpha-MSH, pointing to an involvement of adenylate cyclase activation in the phosphorylation of both the 34 kDa and the 43 kDa protein. Preliminary observations showed that the 34 kDa protein is membrane-bound whereas the 43 kDa protein is of mitochondrial or melanosomal origin.
Mol Cell Endocrinol 1987 May
PMID:alpha-MSH-induced changes in protein phosphorylation of Cloudman S91 mouse melanoma cells. 243 92

Pro-opiomelanocortin (POMC) is the common precursor of several pituitary hormones including alpha-melanotropic hormone, adrenocorticotropic hormone, beta-lipotropin and beta-endorphin. The porcine POMC cDNA was inserted downstream from the late promoter of an SV40-derived expression vector and co-transfected in NIH 3T3 cells with a marker plasmid carrying the neomycin resistance gene. Colonies resistant to the neomycin analog G418 were selected and analyzed for the production of POMC-related peptides by radioimmunoassay. Three clones were found to produce from 350 to 1750 pg of POMC-related peptides per 10(6) cells in 16 h and selected for further analysis. The number of POMC cDNA copies integrated in the host cell genome was determined and the levels of transcription were compared. POMC-related material released in the culture medium by the best producing clone (NJP 4-4) was further analyzed by gel filtration and reversed-phase high-pressure liquid chromatography combined with radioimmunoassays. POMC was found to be synthesized and secreted without further processing or degradation. Negligible amounts of POMC-immunoreactive species were found in cellular extracts indicating that the prohormone is secreted from the NIH 3T3 cells without storage, presumably through a constitutive pathway. Our results suggest that NIH 3T3 fibroblasts do not contain the enzymatic machinery to process complex precursors such as POMC.
Mol Cell Endocrinol 1988 Jul
PMID:Expression of porcine pro-opiomelanocortin cDNA in an established fibroblastic cell line: constitutive secretion of the precursor without proteolytic processing. 246 90

Expression of the RNA coding for the ACTH-beta-lipotrophin precursor, pro-opiomelanocortin (POMC), has been demonstrated in five human small-cell lung cancer (SCLC) cell lines. Using Northern and slot-blot hybridization analysis of RNA and a bovine POMC cDNA as probe, the processed POMC RNA from SCLC cells was found to be approximately 1350 nucleotides in length, which is larger than that found in the normal human pituitary. Expression of the POMC gene was confirmed by measurement of ACTH precursors secreted by the cells, using a novel two-site immunoradiometric assay based on monoclonal antibodies, which directly quantifies both POMC and pro-ACTH but does not recognize ACTH. Levels of POMC in medium accumulated throughout the growth of the cells, in contrast to POMC RNA which showed a relatively constant level of expression. We conclude that human SCLC cell lines are valuable models for studying the aberrant expression and regulation of the human POMC gene.
J Mol Endocrinol 1989 Jul
PMID:Pro-opiomelanocortin gene expression and peptide secretion in human small-cell lung cancer cell lines. 247 13

Modulation of the activity of K+ channels by TRH and the possible involvement of this modulation in TRH-induced release of alpha-MSH were studied in cultured frog melanotrophs, using patch-clamp and perifusion techniques. Pars intermedia cells were enzymatically dispersed and cultured in Leibovitz medium. In order to test the viability of cultured cells, the amount of alpha-MSH released into the medium was measured by radioimmunoassay every day for 1 week of culture. The total amount of alpha-MSH released during the first 4 days of culture was 8.6 times higher than the intracellular content of alpha-MSH on day 1. Melanotrophs were identified by an indirect immunofluorescence technique using a specific antiserum to alpha-MSH. Recordings obtained in whole-cell, cell-attached and excised patch-clamp configurations showed that TRH induced a transient polarization concomitant with an increase in the probability of opening of Ca2+-activated K+ channels. This transient response was followed by a depolarization accompanied by an enhanced frequency of action potential discharge. TRH also induced a decrease in voltage-dependent K+ conductance. Application of tetraethylammonium, a K+ channel blocker, depolarized the cells and increased the basal secretory level without noticeable changes in TRH-evoked alpha-MSH release. These results demonstrate that the neuropeptide TRH both stimulates Ca2+-sensitive K+ channels and inhibits voltage-dependent K+ current in pituitary melanotrophs. Our data indicate that TRH-induced secretion of alpha-MSH is not a direct consequence of the lowering of K+ conductance. It thus appears that basal and TRH-induced alpha-MSH release occur through distinct pathways; the spontaneous release of alpha-MSH is probably linked to membrane potential, while modulation of the electrical activity is not directly involved in TRH-induced activation of the secretory process.
J Mol Endocrinol 1989 Nov
PMID:Dual effects of thyrotrophin-releasing hormone (TRH) on K+ conductance in frog pituitary melanotrophs. TRH-induced alpha-melanocyte-stimulating hormone release is not mediated through voltage-sensitive K+ channels. 251 51

We investigated regulation of the dynamic state of enkephalin and endorphin brain stores during morphine tolerance and dependence using cDNA hybridization and radioimmunoassay of the biologically active peptide(s) and their respective peptide precursors. Rats were made tolerant to morphine with the subcutaneous implantation of three morphine pellets (75 mg each) for a period of five days. Hypothalamic proopiomelanocortin (POMC) mRNA, POMC, and corticotropin-like intermediate lobe peptide content were decreased by 50% in morphine-dependent rats. However, beta-endorphin content remained unchanged. Enkephalin and proenkephalin mRNA content in various brain structures failed to change. A single injection of naltrexone (2 mg/kg) 1 hour before decapitation did not reverse the decrease in POMC mRNA and POMC content elicited by morphine. However, a slower, spontaneous withdrawal caused by removal of the pellets did reverse (after two days) the down-regulation of the hypothalamic POMC system. A single injection of morphine (10 mg/kg) failed to affect any parameter used to assess the dynamic state of opioid peptides.
J Mol Neurosci 1989
PMID:Down-regulation of proopiomelanocortin synthesis and beta-endorphin utilization in hypothalamus of morphine-tolerant rats. 253 67


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