Molecular & Cellular Toxicology

The Korean Society of Toxicogenomics and Toxicoproteomics (대한독성유전 단백체학회)
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Activation of Akt/PKB at Serine 473 by N-acetylphytosphingosine (NAPS) and $C_{2}-ceramide$ Reduces Melanin Synthesis in B16F10 Mouse Melanoma Cells

  • Yi, Seh-Yoon (Department of Chemistry, Suwon University) ;
  • Han, Seon-Kyu (Bioanalysis and Biotransformation Research Center, Korea Institute of Science and Technology) ;
  • Park, Mee-Kyung (Bioanalysis and Biotransformation Research Center, Korea Institute of Science and Technology) ;
  • Yoo, Young-Sook (Bioanalysis and Biotransformation Research Center, Korea Institute of Science and Technology)
  • Published : 2006.06.30
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Abstract

Sphingolipid metabolites regulate many aspects of cell proliferation, differentiation, and apoptosis. In the present study, we have assessed the effects of the novel phytosphingosine derivative, N-acetylphytospingosine (NAPS), on the depigmentation of murine B16F10 melanoma cells, and have also attempted to identify the possible signaling pathway involved, in comparison with $C_{2}-ceramide$. NAPS and $C_{2}-ceramide$ both inhibited the growth of the B16F10 cells in a dose-dependent manner. Melanin content and tyrosinase activity were significantly reduced in response to treatment with NAPS and $C_{2}-ceramide$ at concentrations in a range between $1-5\;{\mu}M$. However, the levels of tyrosinase mRNA, as well as the levels of tyrosinase related protein-1 (TRP-1) and tyrosinase related protein-2 (TRP-2) genes and the level of tyrosinase protein remained unaffected by treatment with either NAPS or $C_{2}-ceramide$. We also attempted to determine the signaling pathway exploited by NAPS and $C_{2}-ceramide$. Interestingly, the phosphorylation of Akt/PKB at serine 473 by NAPS was reduced at the 5 minute mark, whereas $C_{2}-ceramide$ induced the phosphorylation of Akt/PKB at serine 473. Finally, Akt/PKB activity in the NAPS-treated cells was elevated in comparison with the untreated cells. LY294002, a specific PI3-K inhibitor which is located upstream of Akt/PKB, inhibited the phosphorylation of Akt/PKB, but induced an increase in melanin synthesis. These results suggest that the activation of Akt/PKB at serine 473 is related with the suppression of melanin production in the B16F10 mouse melanoma cells. Therefore, the mechanisms exploited by NAPS and $C_{2}-ceramide$ responsible for the depigmentation of B16F10 cells were concluded to involve the inhibition of melanosomal tyrosinase activity.

Keywords

References

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