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Melanocyte-stimulating hormone promotes activation of pre-existing tyrosinase molecules in Cloudman S91 melanoma cells

Naturevolume 255pages644646 (1975) | Download Citation



TYROSINASE activity is greatly enhanced in cultured Cloudman S91 melanoma cells following addition of melanocyte-stimulating hormone (MSH) to the culture medium1. The increased activity occurs in the G2 phase of the cell cycle2 because membrane receptors for MSH are available only in this phase3. The response to MSH is mediated through cyclic AMP (refs 1–4). It is well documented that many peptide hormones function by activating membrane-bound adenyl cyclase molecules, causing net increases in intracellular cyclic AMP concentrations. These increases in turn have profound effects on cell division, morphology, and the expression of differentiated functions in a wide variety of cells and tissues. Little is known, however, about the levels at which genetic expression is regulated or the molecular intermediates involved in the regulation. For example, it is generally assumed that cyclic AMP-dependent protein kinases are involved in many of the responses because most tissues contain such enzymes5. The regulation of glycogenolysis is the best known example supporting this assumption6–7. But it cannot be taken as fact that in eukaryotes all cyclic AMP-mediated processes are post-translational in nature.

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    Pawelek, J., Wong, G., Sansone, M., and Morowitz, J., Yale J. Biol. Med., 46, 430–433 (1973).

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    Wong, G., Pawelek, J., Sansone, M., and Morowitz, J., Nature, 248, 351–354 (1974).

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    Varga, J. M., DiPasquale, A., Pawelek, J., McGuire, J. S., and Lerner, A. B., Proc. natn. Acad. Sci. U.S.A., 71, 1590–1593 (1974).

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    Bitensky, M. W., and Demopoulos, H. B., J. Invest. Dermat., 54, 83 (1970).

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    Kuo, J. F., and Greengard, P., Proc. natn. Acad. Sci. U.S.A., 64, 1349–1355 (1969).

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    Rall, T. W., and Sutherland, E. W., Cold Spring Harb. Symp. quant. Biol., 26, 347–354 (1961).

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    Krebs, E. G., Graves, D. J., and Fischer, E. H., J. Biol. Chem., 234, 378–384 (1960).

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    Pomerantz, S., Science, 164, 838–840 (1969).

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    Axen, R., Porath, J., and Ernback, S., Nature, 214, 1302–1304 (1967).

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  1. Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut, 06510

  2. Departments of Dermatology and Anatomy, Yale University School of Medicine, New Haven, Connecticut, 06510



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