Sphingosylphosphorylcholine inhibits melanin synthesis via pertussis toxin-sensitive MITF degradation.
OBJECTIVE
Sphingolipids act as structural components in cell membranes, and form lipid intermediates that have functional roles as signalling molecules in various cellular processes. Our previous findings have suggested that sphingolipid metabolites are deeply involved in the regulation of melanogenic processes. In this study we aimed to examine sphingosylphosphorylcholine-mediated signalling pathways related to melanogenesis.


METHODS
We determined the hypopigmenting effects and the related signalling pathways of sphingosylphosphorylcholine in Mel-Ab cells. In particular, we analysed the involvement of the G-protein-coupled receptor in sphingosylphosphorylcholine-induced MITF degradation.


RESULTS
Western blotting revealed that sphingosylphosphorylcholine induced the activation of extracellular signal-regulated kinase (ERK), as well as Akt. Moreover, the specific Akt pathway inhibitor LY294002 blocked the hypopigmenting effect of sphingosylphosphorylcholine and abrogated the sphingosylphosphorylcholine-mediated down-regulation of microphthalmia-associated transcription factor (MITF), showing that the Akt pathway is involved in sphingosylphosphorylcholine-mediated melanin inhibition. Treatment with the proteasome inhibitor MG132 blocked the decrease in MITF by sphingosylphosphorylcholine, but sphingosylphosphorylcholine did not decrease the level of MITF mRNA, indicating that the reduction in the level of MITF results from MITF degradation. Furthermore, pre-incubation of Mel-Ab cells with pertussis toxin completely abolished the hypopigmenting effects and the activation of ERK and Akt by sphingosylphosphorylcholine, suggesting that the effects of sphingosylphosphorylcholine are mainly dependent on the G-protein-coupled receptor).


CONCLUSIONS
Together, these results suggest that sphingosylphosphorylcholine reduces melanin synthesis via pertussis toxin-sensitive ERK and Akt activation, and subsequent MITF degradation.
Kim
Dong-Seok
DS
Department of Biochemistry, Chung-Ang University College of Medicine, Seoul, Republic of Korea. ds_kim@cau.ac.kr
Park
Seo-Hyoung
SH
Kwon
Sun-Bang
SB
Kwon
Nyoun Soo
NS
Park
Kyoung-Chan
KC
D000818:Animals; D015153:Blotting, Western; D018929:Cell Culture Techniques; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D047468:Immunoprecipitation; D008543:Melanins / Q000096:biosynthesis*; D008544:Melanocytes / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D051379:Mice; D051739:Microphthalmia-Associated Transcription Factor / Q000037:antagonists & inhibitors / Q000502:physiology; D008858:Microscopy, Phase-Contrast; D010766:Phosphorylation; D010767:Phosphorylcholine / Q000031:analogs & derivatives* / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000502:physiology; D043562:Receptors, G-Protein-Coupled / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology
D004791:Enzyme Inhibitors; D008543:Melanins; D051739:Microphthalmia-Associated Transcription Factor; C497235:Mitf protein, mouse; D043562:Receptors, G-Protein-Coupled; C005356:sphingosine phosphorylcholine; D010767:Phosphorylcholine; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D013110:Sphingosine