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    Melanosomal pH controls rate of melanogenesis, eumelanin/phaeomelanin ratio and melanosome maturation in melanocytes and melanoma cells.

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    Publication date
    2001
    Author
    Ancans, Janis
    Tobin, Desmond J.
    Hoogduijn, Martin J.
    Smit, N.P.
    Wakamatsu, K.
    Thody, Anthony J.
    Keyword
    Melanocyte
    Melanosome;
    Eumelanin/phaeomelanin
    Skin pigmentation
    Melanogenesis
    Peer-Reviewed
    Yes
    
    Metadata
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    Abstract
    The skin pigment melanin is produced in melanocytes in highly specialized organelles known as melanosomes. Melanosomes are related to the organelles of the endosomal/lysosomal pathway and can have a low internal pH. In the present study we have shown that melanin synthesis in human pigment cell lysates is maximal at pH 6.8. We therefore investigated the role of intramelanosomal pH as a possible control mechanism for melanogenesis. To do this we examined the effect of neutralizing melanosomal pH on tyrosinase activity and melanogenesis in 11 human melanocyte cultures and in 3 melanoma lines. All melanocyte cultures (9 of 9) from Caucasian skin as well as two melanomacell lines with comparable melanogenic activity showed rapid (within 24 h) increases in melanogenesis in response to neutralization of melanosomal pH. Chemical analysis of total melanin indicated a preferential increase in eumelanin production. Electron microscopy revealed an accumulation of melanin and increased maturation of melanosomes in response to pH neutralization. In summary, our findings show that: (i) near neutral melanosomal pH is optimal for human tyrosinase activity and melanogenesis; (ii) melanin production in Caucasian melanocytes is suppressed by low melanosomal pH; (iii) the ratio of eumelanin/phaeomelanin production and maturation rate of melanosomes can be regulated by melanosomal pH. We conclude that melanosomal pH is an essential factor which regulates multiple stages of melanin production. Furthermore, since we have recently identified that pink locus product (P protein) mediates neutralization of melanosomal pH, we propose that P protein is a key control point for skin pigmentation. We would further propose that the wide variations in both constitutive and facultative skin pigmentation seen in the human population could be associated with the high degree of P-locus polymorphism.
    URI
    http://hdl.handle.net/10454/3681
    Version
    No full-text available in the repository
    Citation
    Ancans, J., Tobin, D.J., Hoogduijn, M. and Thody, A.J. et al. (2001). Melanosomal pH controls rate of melanogenesis, eumelanin/phaeomelanin ratio and melanosome maturation in melanocytes and melanoma cells. Experimental Cell Research. Vol. 268, No. 1, pp. 26-35.
    Link to publisher’s version
    http://dx.doi.org/10.1006/excr.2001.5251
    Type
    Article
    Collections
    Life Sciences Publications

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