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 show that Cloudman melanoma cells undergo rapid arborization in response to [Nle4,D-Phe7]alpha-melanocyte-stimulating hormone, a potent analogue of alpha-melanocyte stimulating hormone (alpha-MSH). The arbors were established by extension of processes and resembled dendrites. We used this system to study the regulation of cell shape. alpha-MSH is known to induce increases in cAMP levels, and agents such as forskolin and isobutylmethylxanthine that led to increased cAMP also caused arborization. However, equally dramatic arbors were formed after incubation with the protein kinase C inhibitor H-7 [1-(5-isoquinolinesulfonyl)-alpha-methyl-piperazine]. Phorbol diesters that activate protein kinase C led to cell rounding and antagonized alpha-MSH. The actions of protein kinase C cannot be rationalized in terms of indirect effects on cAMP: neither H-7 nor phorbol diesters alone altered cAMP levels, nor did they affect the increase in cAMP induced by MSH. We show also that MSH produced longer-term effects that cannot be mimicked by cAMP. Specifically, even in the continued presence of alpha-MSH, arborization was followed by morphological reversal to the unstimulated flattened configuration within 2 hr. (This did not occur with other agents that increase cAMP or with H-7.) Most importantly, whereas MSH-induced arborization occurred in the presence of cycloheximide, actinomycin D, or in enucleated cells, the reversal of arborization did not. Thus, MSH induced a program of rapid shape change that was dependent on new protein synthesis and gene transcription.
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PMID:Regulation of cell shape in the Cloudman melanoma cell line. 303 40

Cell density is a factor that affects the capacity of Cloudman S91 melanoma cells to respond to melanotropins in monolayer culture. Continuous exposure of melanoma cells to alpha-melanotropin or its potent analog [Nle4, D-Phe7]-alpha-MSH, resulted in maximal stimulation of tyrosinase after 2 d of treatment, but the magnitude of stimulation decreased thereafter despite the continued presence of the melanotropins. However, when melanoma cells continually exposed to melanotropins were subcultured to an initial low cell density and maintained in contact with alpha-MSH or [Nle4, D-Phe7]-alpha-MSH (long-term culture), tyrosinase activity was rapidly restored and greatly enhanced. Also, when cells were seeded at initial densities ranging from 0.2 to 3.2 X 10(6) cells/flask, and exposed for 24 h to 10(-7) M alpha-MSH, only the cultures seeded at low densities (0.2 and 0.4 X 10(6) cells/flask) exhibited maximal tyrosinase activity during the 24 h exposure to the melanotropins. Therefore, tyrosinase activity was primarily affected by cell density rather than by the duration of time the cells were in culture or by continuous exposure to melanotropin. Other flasks of various cell densities were treated with 10(-7) M alpha-MSH or [Nle4, D-Phe7]-alpha-MSH for 24 h, followed by removal of the melanotropins from the culture medium. The magnitude and duration of the residual stimulation of melanoma tyrosinase activity by melanotropins were also found to be dependent on the initial cell density. These results reveal that there is a limited range of optimal cell densities at which melanoma cells can respond to melanotropins and express increased tyrosinase activity.
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PMID:Long-term and residual melanotropin-stimulated tyrosinase activity in S91 melanoma cells is density dependent. 308 84

Ac-[Nle4, D-Phe7]-alpha-MSH4-9-NH2 and Ac-[Nle4]-alpha-MSH4-9-NH2, fragment analogs of the tridecapeptide, alpha-melanocyte stimulating hormone (alpha-MSH, alpha-melanotropin), were synthesized. The potency and prolonged activity of the analogs were compared to alpha-MSH in several melanotropin bioassays. The D-Phe-containing hexapeptide was 10 times more active than alpha-MSH in stimulating melanoma tyrosinase activity. This analog was also 10-fold more potent than alpha-MSH in the lizard skin bioassay and about 10-fold less active in the frog skin bioassay. The melanotropic activity of Ac-[Nle4, D-Phe7]-alpha-MSH4-9-NH2 was considerably prolonged compared to alpha-MSH in each of the bioassays. These results demonstrate that the structural requirements for superpotency and prolonged activity of [Nle4, D-Phe7]-substituted analogs reside within this hexapeptide sequence.
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PMID:Potent and prolonged melanotropic activities of the alpha-MSH fragment analog, Ac-[Nle4,D-Phe7]-alpha-MSH4-9-NH2. 308 18

The structural gene for diphtheria toxin, tox, has been modified at its Sph I site by the introduction of an oligonucleotide linker encoding a unique Pst I restriction endonuclease site and a synthetic oligonucleotide encoding alpha-melanocyte-stimulating hormone (alpha-MSH). The resulting fusion gene directs the expression of a diphtheria toxin-related alpha-MSH hybrid protein in which the diphtheria toxin receptor-binding domain has been replaced with alpha-MSH sequences. The chimeric toxin has been partially purified from periplasmic extracts of recombinant Escherichia coli K-12 and has been found to be selectively toxic for alpha-MSH receptor-positive human malignant melanoma NEL-M1 cells in vitro.
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PMID:Genetic construction, expression, and melanoma-selective cytotoxicity of a diphtheria toxin-related alpha-melanocyte-stimulating hormone fusion protein. 309 31

The alpha-MSH (alpha-melanocyte-stimulating hormone) agonist, Ac-[Nle4, D-Phe7]alpha-MSH4-11NH2 (hereafter called ND4-11 alpha-MSH), is at least 10-fold more potent than alpha-MSH as a stimulus of tyrosinase activity in F1 variant cells of B16 melanoma. The binding to these cells during an incubation with 5 nM (3H)ND4-11 alpha-MSH at 37 degrees C is maximal at 0-30 min, 22 fmol/10(6) cells, but declines to 40% of this value at 4 hr. in the presence of 5 nM (3H)ND4-11 alpha-MSH at 37 degrees C, the acid soluble (cell surface) radioactivity decreased rapidly from 11.4 fmol/10(6) cells at 5 min to 4.6 fmol/10(6) cells at 4 hr. Chromatographic analysis of media and cellular samples revealed that there was no evidence of degradation of (3H)ND4-11 alpha-MSH in the medium but there was evidence of intracellular degradation of (3H)ND4-11 alpha-MSH. Ammonium chloride (10mM) resulted in an increase in acid resistant radioactivity (internalized hormone) at 4 hr. The binding to F1 variant cells during an incubation with 0.155 nM or 5 nM (3H)ND4-11 alpha-MSH at 4 degrees C was constant from 4 hr to 24 hr. Under these conditions, there was no time-dependent change in the acid soluble radioactivity from 4 to 24 hr. Scatchard analysis of (3H)ND4-11 alpha-MSH binding to F1 variant cells at 4 degrees C demonstrated that there were approximately 4500 receptors per cell and an association constant of 17.1 nM-1. These results are consistent with a process of (3H)ND4-11 alpha-MSH binding to its receptor followed by internalization of the receptor-hormone complex and then intracellular degradation of the hormone.
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PMID:Biological activity, binding, and metabolic fate of Ac-[Nle4, D-Phe7]alpha-MSH4-11NH2 with the F1 variant of B16 melanoma cells. 311 Jan 78

In this study a synthetic analog of the calmodulin-binding domain of myosin light chain kinase, a 17-amino-acid peptide (M5) was used to examine the possible role of calmodulin in melanotropin receptor function. Binding of beta-melanocyte-stimulating hormone to its membrane receptor and subsequent stimulation of adenylate cyclase (AC) were found to be specifically inhibited by M5 in a dose-dependent and noncompetitive manner, both in intact M2R melanoma cells and in a plasma membrane preparation derived thereof. Half-maximal inhibition of both hormone binding and melanotropin-sensitive AC activity was shown to occur at approximately 1 microM M5. In contrast, stimulation of AC by prostaglandin E1, guanosine 5'-O-(3-thio)triphosphate, forskolin, and unstimulated enzyme activity were unaffected by the presence of M5, under the same assay conditions. Furthermore, addition of a molar excess of calmodulin to the AC assay completely abolished the inhibitory effects of the peptide on melanotropin-stimulated AC activity. Other peptides of similar size, which bind to calmodulin with low affinity (e.g. glucagon, somatostatin, and vasoactive intestinal peptide), were shown to be totally ineffective in inhibiting melanotropin-sensitive AC. These findings, along with those shown previously for other antagonists of calmodulin, suggest a role for an M5-binding protein, as of yet unidentified, involved in the regulation of the melanotropin receptor function.
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PMID:A synthetic analog of the calmodulin-binding domain of myosin light chain kinase inhibits melanotropin receptor function and activation of adenylate cyclase. 336 68

In this study, two melanotropin binding proteins from M2R melanoma cells have been identified based on the photochemical cross-linking of [125I]iodinated porcine beta-MSH ([ 125I]iodo-beta-MSH) to melanoma cell membranes, using N-hydroxysuccinimidyl-azidobenzoate. Autoradiography of photoaffinity-labeled M2R membrane protein, after sodium dodecyl sulfate-polyacrylamide gel electrophoresis, revealed the specific labeling of two separate bands with an apparent molecular mass of 43 and 46 kilodaltons, respectively. Photoaffinity labeling of both bands was of near-equal intensity and could be inhibited, in a dose-dependent manner, by the addition of unlabeled beta-MSH before photolysis. In addition, agents known to inhibit the binding of beta-MSH to its cellular receptor, such as EGTA, GTP, guanosine 5'-O-(3-thio)triphosphate, and a synthetic analog of the calmodulin-binding domain of myosin light chain kinase-M5, were all found to specifically inhibit the labeling of these two protein bands by the azido derivative of [125I]iodo-beta-MSH. In contrast, addition of a nonrelated peptide, vasoactive intestinal peptide, had no effect upon the labeling of these melanotropin-binding proteins. On the basis of these results we suggest that the two proteins may function as the binding domain(s) of the cellular receptor for melanotropins, or may represent entire receptor moieties themselves.
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PMID:Identification and characterization of melanotropin binding proteins from M2R melanoma cells by covalent photoaffinity labeling. 341 15

A synthetic nonapeptide fragment of thrombin inhibits the cellular motility in culture of a human melanoma subclone that possesses a high metastatic potential in mice. Concomitant with the loss of ability to translocate in culture, these cells exhibit increases in the average length of actin cables and cellular surface area in contact with the substratum. The spreading activity is observed at a nonapeptide concentration of 1 nM within 1 hr of exposure at 37 degrees C. Pretreatment of cells with this nonapeptide does not block signal transduction through plasma membrane receptors for the following growth or differentiation factors: alpha-melanotropin (alpha-melanocyte-stimulating hormone), nerve growth factor, and transforming growth factor type beta. Results of the present study suggest an approach to cancer chemotherapy in which naturally occurring peptides from two functionally orthogonal classes may be used to perform two complementary functions: inhibition of metastasis and induction of differentiation.
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PMID:Identification of a synthetic nonapeptide sequence that inhibits motility in culture of a melanoma subclone that possesses a high metastatic potential. 348 May 26

UV-irradiation at 365 nm of cultured Cloudman S91 mouse melanoma cells in the presence of photoreactive alpha-MSH analogues induced longlasting receptor stimulation as revealed by the ensuring activation of tyrosinase. Receptor labelling was more efficient with 4-diazirinophenyl and 2-nitro-4-azidophenyl photolabels than with 4-azidophenyl, and was further increased when superpotent [Nle4,D-Phe7]-alpha-MSH was used as ligand. Incubation of B16 melanoma cell membranes with mono-iodinated [Nle4,D-Phe7,Trp-(Naps)9]-alpha-MSH followed by UV-irradiation at 310-550 nm labelled a single band on SDS-PAGE with a molecular mass approximately or equal to 45 kDa. The displacement curve obtained in a competitive photolabelling experiment paralleled that of the binding assay, demonstrating that the labelling was specific.
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PMID:Photoaffinity labelling of melanoma cell MSH receptors. 369 12

D-alpha tocopheryl succinate (vitamin E succinate), which is known to induce differentiation and growth inhibition in murine B-16 melanoma cells, reduced basal and melanocyte-stimulating hormone (MSH)-stimulated adenylate cyclase (AC) activity in vitro. Vitamin E succinate treatment also reduced sodium fluoride- and forskoline-stimulated AC activity of melanoma cells in vitro. Treatment of cells with vitamin E succinate (6 micrograms/ml] for a period of 24 hours was sufficient to reduce MSH-stimulated AC activity. Other forms of vitamin E, such as d1-alpha tocopheryl nicotinate, d1-alpha tocopheryl acetate, and d1-alpha tocopherol, which did not affect growth or morphology of melanoma cells, were relatively less effective in altering basal and MSH-stimulated AC activity. Retinoic acid, which inhibited the growth of B-16 melanoma cells, also reduced basal and MSH-, NaF-, and forskolin-stimulated AC activity in vitro. Prostaglandin A2, which inhibited growth and altered morphology, did not change basal or MSH-stimulated AC activity. These results show that one of the mechanisms of action of vitamin E succinate and retinoic acid on melanoma cells may involve reduction of basal and MSH-sensitive AC activity, and this vitamin effect is not necessarily related to growth inhibition.
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PMID:Alpha tocopheryl succinate inhibits melanocyte-stimulating hormone (MSH)-sensitive adenylate cyclase activity in melanoma cells. 369 13


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