Modulation of murine melanocyte function in vitro by agouti signal protein.
Molecular and biochemical mechanisms that switch melanocytes between the production of eumelanin or pheomelanin involve the opposing action of two intercellular signaling molecules, alpha-melanocyte-stimulating hormone (MSH) and agouti signal protein (ASP). In this study, we have characterized the physiological effects of ASP on eumelanogenic melanocytes in culture. Following exposure of black melan-a murine melanocytes to purified recombinant ASP in vitro, pigmentation was markedly inhibited and the production of eumelanosomes was decreased significantly. Melanosomes that were produced became pheomelanosome-like in structure, and chemical analysis showed that eumelanin production was significantly decreased. Melanocytes treated with ASP also exhibited time- and dose-dependent decreases in melanogenic gene expression, including those encoding tyrosinase and tyrosinase-related proteins 1 and 2. Conversely, melanocytes exposed to MSH exhibited an increase in tyrosinase gene expression and function. Simultaneous addition of ASP and MSH at approximately equimolar concentrations produced responses similar to those elicited by the hormone alone. These results demonstrate that eumelanogenic melanocytes can be induced in culture by ASP to exhibit features characteristic of pheomelanogenesis in vivo. Our data are consistent with the hypothesis that the effects of ASP on melanocytes are not mediated solely by inhibition of MSH binding to its receptor, and provide a cell culture model to identify novel factors whose presence is required for pheomelanogenesis.
Sakai
C
C
Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Ollmann
M
M
Kobayashi
T
T
Abdel-Malek
Z
Z
Muller
J
J
Vieira
W D
WD
Imokawa
G
G
Barsh
G S
GS
Hearing
V J
VJ
D054366:Agouti Signaling Protein; D000818:Animals; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D019746:Intramolecular Oxidoreductases; D007535:Isomerases / Q000235:genetics / Q000378:metabolism; D008543:Melanins / Q000096:biosynthesis / Q000235:genetics; D009074:Melanocyte-Stimulating Hormones / Q000494:pharmacology; D008544:Melanocytes / Q000166:cytology / Q000502:physiology*; D008562:Membrane Glycoproteins; D051379:Mice; D008810:Mice, Inbred C57BL; D014442:Monophenol Monooxygenase / Q000235:genetics / Q000378:metabolism; D010088:Oxidoreductases; D011506:Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D011979:Receptors, Pituitary Hormone / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000494:pharmacology
D054366:Agouti Signaling Protein; D036341:Intercellular Signaling Peptides and Proteins; D008543:Melanins; D008562:Membrane Glycoproteins; D011506:Proteins; D012333:RNA, Messenger; D011979:Receptors, Pituitary Hormone; D011993:Recombinant Fusion Proteins; C018362:pheomelanin; C041877:eumelanin; C029446:MSH receptor; D009074:Melanocyte-Stimulating Hormones; D000242:Cyclic AMP; D010088:Oxidoreductases; C489799:TYRP1 protein, human; C079621:Tyrp1 protein, mouse; C064056:tyrosinase-related protein-1; D014442:Monophenol Monooxygenase; D007535:Isomerases; D019746:Intramolecular Oxidoreductases; C042501:dopachrome isomerase