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)

Tyrosinase activity was increased in hair follicular melanocytes of C3H-HeAvy mice during the hair cycle and reached higher levels on days 6-8 after plucking than on day 12. Similarly, the rate of incorporation of [35S]methionine into tyrosinase was greater on days 6-8 than on day 12, but the relative difference was much less. alpha-MSH had no effect on tyrosinase activity or the rate of [35S]methionine incorporation on day 12 and, while it increased both on days 6 and 8, it had a greater effect upon the latter. Pulse-chase experiments showed that the half-life of tyrosinase was 3.5 h and that this was unaffected by alpha-MSH. The results indicate that the increases in tyrosinase activity which occur during the hair cycle involve changes in both the synthesis and activation of the enzyme and that the predominant effect of alpha-MSH is on the former of these two processes.
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PMID:Regulation of tyrosinase synthesis by alpha-melanocyte-stimulating hormone in hair follicular melanocytes of the mouse. 282 5

A radioreceptor assay for alpha-MSH is described which is based on cultured mouse B16 melanoma cells and bioactive monoiodinated [Nle4]-alpha-MSH tracer. The assay was used (1) to study the binding characteristics of alpha-MSH to B16 cells, (2) to determine the relative binding activity of MSH peptides, and (3) to measure MSH in tissue extracts. The association of alpha-MSH to B16 cells reached a stable plateau after 3 h at 15 degrees C. At 25 degrees or 37 degrees C, the binding was transient and at 0-1 degree C, the association was very slow. The hormone-receptor complex was relatively stable between 0 degrees and 15 degrees C whereas a 50% dissociation was reached after 90 min at 25 degrees C and after 35 min at 37 degrees C. The mean KD for alpha-MSH of four saturation experiments was 1.3 nM and the number of receptors 9570 per cell. 1,10-Phenanthroline had a stabilizing effect in the binding assay when used at a 0.3 mM concentration. From the MSH peptides tested in the binding assay, some showed similar potencies in three bioassays (tyrosinase, melanin and Anolis skin), whereas others displayed considerably lower bioassay values than expected from the binding data. This shows that binding and bioactivity can be dissociated in some of the MSH peptides. The biological activity of MSH from the neurointermediate lobe of the rat pituitary as measured by its binding to B16 cells corresponds fairly well with RIA results; in the anterior lobe, alpha-MSH values are overestimated because of the large amount of ACTH present.
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PMID:Radioreceptor assay for alpha-MSH using mouse B16 melanoma cells+. 283 20

In an attempt to clarify the mechanisms underlying the lack of melanin formation in hair bulb melanocytes of chinchilla mice (genotype a/a, cch/cch, strain PW), we studied the effect of exogenous melanogenic stimulants such as theophylline (Tp), dibutyryl cyclic AMP (db-cAMP), and alpha-melanocyte-stimulating hormone (alpha-MSH) on the induction of melanization. Skin explants excised from the dorsa of chinchilla or lethal yellow C57BL/6J, Ay/a) mice at 7 to 9 days of age were cultured in the presence of Tp (2 mM), db-cAMP (2 mM), or alpha-MSH (1.0 microgram/ml). After 2 to 5 days, melanin formation was induced in hair bulb melanocytes of chinchilla mutant in response to both Tp and db-cAMP, but alpha-MSH did not produce new melanin formation. In contrast, yellow mutant increased the melanin formation in response to all stimulants. Electron microscopic studies demonstrated that while non-treated hair bulb melanocytes of chinchilla mutant contain a large number of stage II-III melanosomes without melanin deposition, a hair bulb treated with Tp exhibits the new formation of melanin within melanosomes that appears both as typical eumelanosomes with striated longitudinal matrices and as pheomelanosomes with vacuolar melanization. Quantitative analysis of melanin has revealed that in chinchilla mutant, Tp and db-cAMP induce a severalfold increase in the formation of both eumelanin [pyrrole-2,3,5-tricarboxylic acid (PTCA)] and pheomelanin (aminohydroxyphenylalanine), whereas alpha-MSH does not stimulate production of either melanin. In yellow mutant, db-cAMP induced a remarkable increase in eumelanin (PTCA), in contrast to the fewfold increase induced by alpha-MSH and Tp. All stimulants induced a slight increase in pheomelanin to a similar extent. These different reactions to melanogenic stimulation suggest a possible defect in the tyrosinase activation system within hair bulb melanocytes in chinchilla mutants.
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PMID:Induction of melanization within hair bulb melanocytes in chinchilla mutant by melanogenic stimulants. 284 Apr 69

The melanocytotoxic effects of 4-hydroxyanisole (4-OHA) are thought to depend upon its conversion to toxic oxidation products by the enzyme tyrosinase. In this study, the cytotoxicity of 4-OHA was examined in different B16 melanoma cell lines that show varying levels of tyrosinase and after stimulation by melanocyte-stimulating hormone (MSH) and all-trans-retinoic acid (RA). 4-OHA decreased cell survival of three melanotic and one amelanotic cell line in culture, but the effect was unrelated to their tyrosinase activity or the subcellular localization of the enzyme. Although stimulation of tyrosinase activity with RA enhanced the cytotoxicity of 4-OHA, no similar enhancement occurred with alpha-MSH. It appears that there is no relationship between the cytotoxic effects of 4-OHA and intracellular tyrosinase and the enhancement of its cytotoxicity by RA may well be related to the antiproliferative effects of the retinoid.
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PMID:Cytotoxicity of 4-hydroxyanisole and tyrosinase activity in variant cell lines of B16 melanoma. 285 44

In this study, the effect of alpha-MSH on tyrosinase activity was compared in epidermal and hair follicular melanocytes of mice. It had no effect on epidermal tyrosinase activity in dorsal skin from neonatal non-agouti black mice (C57BL/6J) in both in-vivo and in-vitro experiments. Theophylline and 8-bromocyclic (c)AMP were similarly without effect in in-vitro experiments. In-vivo administration of alpha-MSH and theophylline for 7 days was also without effect on epidermal tyrosinase activity in ear skin of adult non-agouti mice, and the same was true for alpha-MSH in wild-type agouti mice. Activation of the epidermal melanocytes in the non-agouti and wild-type agouti mice with ultraviolet radiation also failed to bring about a response to alpha-MSH and to theophylline in the case of the former. No tyrosinase activity was detected in the epidermis of viable yellow mice (C3H-HeAvy), but, as shown previously, tyrosinase activity was present in the hair follicle when the hair was actively growing and was increased in those mice given either alpha-MSH or theophylline. alpha-MSH and theophylline had no such effects on hair follicular tyrosinase activity in the non-agouti mice. The present results suggest that alpha-MSH- and cAMP-dependent mechanisms have little or no importance in the regulation of tyrosinase expression in mouse epidermal melanocytes. alpha-MSH may, however, regulate tyrosinase expression in hair follicular melanocytes, but even in these melanocytes its action may be restricted to mice that express the agouti gene.
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PMID:Effect of alpha-melanocyte-stimulating hormone on tyrosinase activity in hair follicular and epidermal melanocytes of the mouse. 285 41

The fluorescein-labeled melanotropin [N alpha-chlorotriazinylaminofluorescein-Ser1,Nle4,D-Phe 7]-alpha-MSH, was prepared by solid-phase techniques of peptide synthesis. The biological actions of this analogue were determined in several melanocyte bioassays and were compared with the parent peptide [Nle4,D-Phe7]-alpha-MSH and the native hormone alpha-MSH. The fluorescein compound was a superpotent agonist with approximately 10 times more activity than alpha-MSH in both the frog and the lizard skin bioassays. Murine S91 melanoma cells assayed in vitro (tyrosinase bioassay) were as responsive to the fluorescein analogue as to alpha-MSH. The analogue exhibited ultraprolonged biological activity and the biological activities were unaffected by treatment of the analogue with alpha-chymotrypsin. The fluorescein-labeled melanotropin should prove useful for melanotropin receptor characterization.
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PMID:Synthesis and biological evaluation of the superagonist [N alpha-chlorotriazinylaminofluorescein-Ser1,Nle4,D-Phe7]-al pha-MSH. 298 82

alpha-Melanotropin (alpha-melanocyte stimulating hormone, alpha-MSH) stimulates tyrosinase activity in Cloudman S91 murine melanoma cells. Three [Nle4, D-Phe7]-substituted alpha-melanotropin analogues, [Nle4, D-Phe7]-alpha-MSH, Ac-[Nle4, D-Phe7]-alpha-MSH4-11-NH2, and Ac-[Nle4, D-Phe7]-alpha-MSH4-10-NH2, are at least 100-fold more effective than alpha-MSH in stimulating melanoma tyrosinase, the rate-limiting enzyme in melanin biosynthesis. These [Nle4, D-Phe7]-substituted melanotropin analogues induce tyrosinase activity in melanoma cells with shorter contact times than required by the native hormone, alpha-MSH. [Nle4, D-Phe7]-substituted melanotropins also induce a prolonged (residual) stimulation of melanoma tyrosinase. Following incubation of melanoma cells in the presence of [Nle4, D-Phe7]-alpha-MSH for 24 h, tyrosinase activity is maintained for up to 6 days in the absence of the melanotropin. The shorter 4-10 and 4-11 fragment analogues also exhibit residual melanotropic activity. The prolonged stimulation of tyrosinase in the absence of the analogues is maintained even though melanoma cells continue to divide about every 24 h. These results suggest that melanoma cells possess spare melanotropin receptors and that [Nle4, D-Phe7]-substituted analogues bind almost irreversibly to these receptors or to some other component of the adenylate cyclase enzyme complex responsible for enhancing tyrosinase activity and melanin production.
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PMID:Prolonged stimulation of S91 melanoma tyrosinase by [Nle4, D-Phe7]-substituted alpha-melanotropins. 299 67

Melanotropins induce melanogenesis in mouse Cloudman S91 melanoma cells by stimulating the activity of tyrosinase. In monolayer culture, alpha-melanocyte-stimulating hormone and the superpotent analogue 4-norleucine, 7-D-phenylalanine-alpha-melanocyte, which had prolonged effects on tyrosinase activity, did not inhibit the proliferation of melanoma cells even at concentrations that elicited maximal tyrosinase stimulation. In soft agar the melanotropins stimulated the formation of melanized colonies and increased the cloning and proliferative potentials of melanoma cells. Both melanotropins increased the number of small (42-104 microns in diameter) colonies at initial plating densities ranging from 625 to 7,500 cells/dish. The number of larger (greater than 104 microns in diameter) colonies was also increased except at densities 5,000 cells or more/dish, wherein the proliferative capacity was inhibited; yet the cloning efficiency was still increased. Therefore, in bilayer soft agar cultures, melanotropins stimulate the growth of the clonogenic S91 melanoma cell population under conditions that allow for optimal expression of the cloning and proliferative potentials of these cells.
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PMID:Actions of melanotropins on mouse melanoma cell growth in vitro. 300 49

The biological activity and a possible modulatory role of the N-terminal tetrapeptide Ser-Tyr-Ser-Met from alpha-MSH/ACTH was tested in the Anolis melanophore assay, the Xenopus melanophore assay, tyrosinase stimulation in mouse melanoma cells and in excessive grooming in the rat. ACTH1-4 did not exhibit biological activity in any of these four assays nor did it have modulatory properties in the Xenopus and the melanoma cell assay. However, in the Anolis assay ACTH1-4 potentiated pigment dispersion induced by alpha-MSH, alpha-MSH5-13 and ACTH1-24 by a factor of about 2. In the grooming assay ACTH1-4 potentiated the effects of alpha-MSH, alpha-MSH5-13, ACTH1-16 and ACTH5-16, but not those of ACTH1-24. Oxidized ACTH1-4 was without biological activity and potentiating properties in all four assays. This study shows that small fragments of the pro-opiomelanocortin precursor, which are devoid of biological activity, can modulate peripheral and central actions of alpha-MSH/ACTH.
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PMID:ACTH1-4 potentiates alpha-MSH-induced melanophore dispersion and excessive grooming. 301 87

Des-, mono-, and diacetylated melanotropin (des-, mono-, and di-Ac MSH, respectively) were compared for their dose-related effects on content of adenosine 3':5'-monophosphate (cAMP) and tyrosinase activity in the Cloudman S91 mouse melanoma tumor. Des-Ac MSH was more potent than the acetylated forms of MSH at increasing cellular levels of cAMP; mono- and di-Ac MSHs, however, were more potent than des-Ac MSH at elevating the activity of the enzyme, tyrosinase. Lysine-gamma1 MSH, a melanotropin from the amino terminus of pro-opiomelanocortin, exhibited slight stimulatory effects on tyrosinase and these actions were less than additive to those of mono-Ac MSH. Unlike their actions on amphibian skin-darkening or in mammalian behavior, neither beta-endorphin1-31 nor its derivatives, N-Ac-beta-endorphin1-27 or beta-endorphin30-31 (glycylglutamine), exhibited any influence on tyrosinase activity evoked by mono-Ac MSH in the tumor cells.
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PMID:The effects of pro-opiomelanocortin peptides on cyclic AMP and tyrosinase in melanoma cells. 302 51


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