These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: The pinkeyed-dilution protein and the eumelanin/pheomelanin switch: in support of a unifying hypothesis.
    Author: Lamoreux ML, Zhou BK, Rosemblat S, Orlow SJ.
    Journal: Pigment Cell Res; 1995 Oct; 8(5):263-70. PubMed ID: 8789201.
    Abstract:
    The two major types of mammalian melanin are pheomelanin (yellow or red pigment) and eumelanin (black or brown). The agouti (A) and extension (E) loci determine whether follicular melanocytes will deposit pheomelanin or eumelanin within their melanosomes. Mutations at the murine pinkeyed-dilution (P) locus cause a striking reduction in deposition of eumelanic, but not pheomelanic, pigment. The mRNA encoded at the P locus is not expressed in skin that exclusively produces pheomelanic pigment as a result of mutation at the agouti locus. We have suggested, based upon both genetic and biochemical evidence, that three key melanogenic proteins--tyrosinase, tyrosinase-related-protein-1 (TRP-1), and TRP-2, encoded at the albino (C), brown (B), and slaty (Slt) loci, respectively--form a high-molecular-weight "melanogenic complex" within the melanosome. High-molecular-weight forms of tyrosinase, TRP-1 and TRP-2, are absent from eumelanic ocular tissues of p(un)/p(un) mice that fail to produce normal P-locus transcript, even though these mice are genetically normal at the loci that regulate production of the three melanogenic proteins. We have hypothesized that the presence of the p-locus protein is important for the integrity of the melanogenic complex and for the levels of members of the TRP family. We show here that the yellow skins of mice mutant at the agouti or extension loci, as well as the nonyellow skins of pinkeyed-unstable (p(un)/p(un)) mice, demonstrate greatly diminished levels of tyrosinase, TRP-1 and TRP-2, and an absence or markedly decreased proportion of high-molecular-weight forms of melanogenic proteins. We conclude that normal levels of wild-type P-locus protein are necessary for eumelanogenesis and that the absence of this protein may be necessary, but is not sufficient to cause the melanosome to switch to the production of pheomelanin. We discuss the implications of our results in relation to the interacting genetic controls regulating melanogenesis.
    [Abstract] [Full Text] [Related] [New Search]