title: Sphingosine-1-phosphate decreases melanin synthesis via microphthalmia-associated transcription factor phosphorylation through the S1P3 receptor subtype.
abstract: OBJECTIVE
  Previously, we reported that sphingosine-1-phosphate (S1P) reduced melanin synthesis. In this study we have investigated S1P receptor-mediated extracellular signal-regulated protein kinase (ERK) activation and microphthalmia-associated transcription factor (MITF) phosphorylation.
  
  
  METHODS
  To examine S1P-induced signalling pathways, electron and confocal microscopic studies, reverse transcription-polymerase chain reaction and Western blot analysis were performed.
  
  
  RESULTS
  S1P phosphorylated MITF at Ser73, which may have resulted in a MITF mobility shift. Furthermore, 90 kDa ribosomal S6 kinase-1 (RSK-1) phosphorylation was observed after S1P treatment. In addition, PD98059 abrogated the S1P-induced MITF mobility shift and RSK-1 activation. In experiments with MITF mutants, it was shown that dual phosphorylation at Ser73 and Ser409 was indispensable for MITF degradation. We investigated further the actions of S1P on its specific receptors. The results showed that pertussis toxin completely abolished the hypopigmentary effects and ERK pathway activation by S1P, suggesting that S1P regulated melanogenesis via its receptor. The use of specific receptor antagonists indicated that the S1P(3) receptor was dominantly involved in S1P-induced ERK activation and hypopigmentation.
  
  
  CONCLUSIONS
  The results suggested that S1P reduced melanin synthesis via S1P(3) receptor-mediated ERK and RSK-1 activation, and subsequent MITF dual phosphorylation and degradation.
authors.affiliation: Department of Biochemistry, College of Medicine, Chung-Ang University, Heukseok-Dong Dongjak-Gu, Seoul, Korea.
authors.forename: Dong-Seok
authors.initials: DS
authors.lastname: Kim
authors.forename: Seo-Hyoung
authors.initials: SH
authors.lastname: Park
authors.forename: Yun-Mi
authors.initials: YM
authors.lastname: Jeong
authors.forename: Sun-Bang
authors.initials: SB
authors.lastname: Kwon
authors.forename: Arlo J
authors.initials: AJ
authors.lastname: Miller
authors.forename: David E
authors.initials: DE
authors.lastname: Fisher
authors.forename: Kyoung-Chan
authors.initials: KC
authors.lastname: Park
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D008246:Lysophospholipids / Q000494:pharmacology*; D008543:Melanins / Q000096:biosynthesis*; D008544:Melanocytes / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D051379:Mice; D051739:Microphthalmia-Associated Transcription Factor / Q000378:metabolism*; D018613:Microscopy, Confocal; D010766:Phosphorylation / Q000187:drug effects; D049349:Receptors, Lysosphingolipid / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D014162:Transfection
chemical_list: D008246:Lysophospholipids; D008543:Melanins; D051739:Microphthalmia-Associated Transcription Factor; D049349:Receptors, Lysosphingolipid; C060506:sphingosine 1-phosphate; D048049:Extracellular Signal-Regulated MAP Kinases; D013110:Sphingosine