Cysteine Transport in Melanosomes from Murine Melanocytes

The synthesis of pheomelanin requires the incorporation of thiol‐containing compound(s) during the process of mammalian melanogenesis. Since melanins are produced only in specialized, membrane‐bound organelles, known as melanosomes, such thiol donor(s) must cross the membrane barrier from the cytoso...

Full description

Saved in:
Bibliographic Details
Published in:Pigment cell research 1999-02, Vol.12 (1), p.4-12
Main Authors: POTTERF, S. BRIAN, VIRADOR, VICTORIA, WAKAMATSU, KAZUMASA, FURUMURA, MINAO, SANTIS, CHIE, ITO, SHOSUKE, HEARING, VINCENT J.
Format: Article
Language:English
Subjects:
Animals
Biological Transport
Carrier Proteins - metabolism
Cells, Cultured
Cysteine
Cysteine - metabolism
Glutathione - metabolism
Melanin
Melanins - metabolism
Melanocytes - metabolism
Melanosomes
Melanosomes - metabolism
Mice
Pigmentation
Sulfur Radioisotopes - pharmacokinetics
Transport
Tyrosine - metabolism
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The synthesis of pheomelanin requires the incorporation of thiol‐containing compound(s) during the process of mammalian melanogenesis. Since melanins are produced only in specialized, membrane‐bound organelles, known as melanosomes, such thiol donor(s) must cross the membrane barrier from the cytosol to the melanosome interior. Cysteine and/or glutathione (GSH) were proposed as suitable thiol donors, although uptake of these compounds into melanosomes was not previously characterized. In this study, we show that cysteine is transported, in a temperature‐ and concentration‐dependent manner, across membranes of melanosomes derived from murine melanocytes. Additional proof that cysteine uptake results from a carrier‐mediated process and is not due to simple diffusion or to a membrane channel, was obtained in counter‐transport experiments, in which melanosomes preloaded with cysteine methyl ester took up significantly more [35S]cysteine than did unloaded controls. In contrast, we were unable to detect any significant uptake of [35S]GSH over a wide concentration range, in the presence or in the absence of reducing agent. This study is the first demonstration of melanosomal membrane transport of cysteine, and it strongly suggests that free cysteine is the thiol source utilized for pheomelanin synthesis in mammalian melanocytes.
ISSN:0893-5785
1600-0749
DOI:10.1111/j.1600-0749.1999.tb00502.x