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Results for “Pro-Opiomelanocortin”

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PubMed1986

Regulation of proopiomelanocortin (POMC) mRNA levels in primary pituitary cultures.

The effect of a variety of neurotransmitters and of corticotropin releasing factor (CRF) upon levels of mRNA coding for proopiomelanocortin (POMC) was studied in primary cultures of rat pituitary. Total nucleic acid was extracted from cells, fixed on nitrocellulose and hybridized to a single-stranded alpha 32P-labeled DNA complementary to 150 bases of mouse POMC mRNA. After two days incubation with CRF (10(-8) M), the levels of POMC mRNA in both the anterior (AL) and the intermediate lobe (IL) cells increased by about 100%. A similar increase in the IL cells was seen after incubation with the beta-adrenergic agonist isoprenalin (10(-6) M). In contrast, dopamine (10(-6) M) and GABA (10(-6) M) decreased POMC mRNA levels in the IL cells to about 50% of control levels without affecting POMC mRNA levels in the AL cells. In both pituitary lobes, POMC mRNA was decreased by the Ca2+-channel blocker D600 (10(-5) M) and increased by forskolin (10(-6) M). This indicates that both cAMP and Ca2+ ions play an important role as intracellular messengers for the control of POMC gene expression in normal melanotrope and corticotrope cells.

Animals↗
PubMed1988

Proopiomelanocortin producing cells of spleen: increase after transplantation with opioid-peptide producing Ehrlich ascites tumor cells.

Proopiomelanocortin (POMC) peptides are produced by many cell systems, including a population of macrophage-like cells in mouse spleen. After transplantation of mice with Ehrlich ascites tumor cells, the number of POMC producing spleen cells increase up to 10-fold by 5 to 6 days. The POMC peptides produced by these cells increase even more, as evidenced by radioimmunoassay. Thus, these data indicate both proliferation of splenic POMC cells and increased production of POMC peptides per cell after tumor challenge. Characterization of the peptides by sequence-specific radioimmunoassays and high performance liquid chromatography documents the presence of both ACTH(1-39) and of ACTH(1-14) in these cells. These peptides have multifacetted effects on immune parameters and may exhibit a general antiinflammatory action, partly mediated through inhibition of interleukin 1-stimulated events. The tumor cells themselves do not produce POMC peptides, but display met- and leu-enkephalin immunoreactivity. Also cultured tumor cells display such immunoreactivity, indicating endogenous production of opioid peptides. The opioid peptides of the tumor cells may both affect host immune defenses and play intratumoral autocrine or paracrine roles.

Animals↗
PubMed1987

[Expression in Escherichia coli cells of the nucleotide sequence of DNA coding for the bovine lipotropic hormone].

A cDNA fragment of bovine proopiomelanocortin coding for beta-lipotropic hormone was joined with a promoter and ribosome binding site of B. amyloliquefaciens and cloned in E. coli in pBR 327 plasmid. The level of beta-lipotropin synthesis in bacterial cells transformed by the obtained plasmid was estimated immunochemically. The level of beta-lipotropin production was shown to be 5 mg per liter of bacterial culture.

Amino Acid Sequence↗
PubMed1987

[Cloning of DNA complementary to mRNA for proopiomelanocortin from the bovine, rat and human hypophysis. Hormonal regulation of proopiomelanocortin mRNA in the rat hypophysis].

Cloning of DNA and complementary mRNA of bovine, rat and human proopiomelanocortin (POMC) was carried out. A structural analysis of the cloned cDNA of POMC was performed. Using restriction fragments of bovine, rat and human POMC cloned cDNA, probes for molecular hybridization based on one-chain bacteriophage M13 were made. Using the dot-hybridization technique with labeled [32P] POMC cDNA, the effect of 17 beta-estradiol and adrenalectomy on the POMC mRNA level in rat hypophysis was studied. The hormone was shown to significantly decrease the POMC mRNA content at a concentration of 4 and 8 micrograms per 100 g of body weight 4 hours after injection. Adrenalectomy caused a 2-3-fold increase in the POMC mRNA level in rat hypophysis after a period of 5-7 days. The possibility of polyhormonal control of POMC genome transcription is discussed.

Adrenalectomy↗
PubMed1986

Amidation of joining peptide, a major pro-ACTH/endorphin-derived product peptide.

Based on sequence data, rat and mouse pro-adrenocorticotropin (ACTH)/endorphin could give rise to joining peptide, a short acidic peptide that could terminate with a glutamic acid alpha-amide. Rat and mouse pituitary cells were found to cleave the pro-ACTH/endorphin precursor at an -Arg-Arg- site to produce primarily joining peptide-sized material. The amounts of joining peptide were approximately equimolar to the other major pro-ACTH/endorphin-derived products. Using antisera specific for the COOH-terminal modifications of joining peptide and three analytical approaches which separate amidated from glycine-extended forms of joining peptide, it was found that most of the joining peptide in murine anterior and intermediate pituitary was amidated. Identification of the amidated and glycine-extended forms of joining peptide was confirmed by amino acid analysis of the purified molecules. When anterior pituitary corticotrope tumor cells were grown in culture medium lacking ascorbate, there was no detectable ascorbate in the cells; nevertheless, a significant fraction of the joining peptide produced was alpha-amidated, indicating that production of alpha-amidated product was not totally dependent on ascorbate. The amidation state of the joining peptide produced by mouse corticotrope tumor cells was responsive to added ascorbate. Cells grown in medium containing ascorbic acid at the levels found in plasma concentrated the ascorbate to the levels normally found in pituitary tissue, and nearly all of the joining peptide produced was alpha-amidated. The amidation state of secreted joining peptide mirrored the amidation state of the joining peptide in the cells.

Amides↗
PubMed1986

Characterization of proopiomelanocortin mRNA detected by in situ hybridization.

In situ hybridization is a method for detecting specific nucleotide sequences by using a labeled complementary nucleic acid probe. We have characterized in situ hybridization in rat pituitary using a cDNA probe directed against a portion of proopiomelanocortin (POMC) mRNA to show its specificity in tissue sections. This characterization includes the size of the target mRNA from tissue processed for in situ hybridization, the dissociation pattern of the cDNA:mRNA hybrid, and quantitation of changes in POMC mRNA levels in the rat pituitary intermediate lobe detected both by in situ hybridization and "dot blot" techniques.

Animals↗