ADAM protease inhibitors reduce melanogenesis by regulating PMEL17 processing in human melanocytes

作者：Kawaguchi Masakazu^*; Hozumi Yutaka; Suzuki Tamio

来源：Journal of Dermatological Science, 2015, 78(2): 133-142.

DOI：10.1016/j.jdermsci.2015.02.020

• Melanocyte
• Melanosome
• PMEL17
• ADAM protease
• Melanogenesis

Background: ADAMs (a disintegrin and metalloprotease) are a family of proteases involved in ectodomain shedding that play a role in various biological processes such as cell adhesion and migration. ADAM10 and ADAM17 are suggested to be involved in pigmentary disorders.
Objective: We examined the effect of ADAM protease inhibitors on the modulation of melanogenesis in normal human epidermal melanocytes (NHEM).
Methods: NHEMs and B1 6F10 treated with ADAM protease inhibitors were analyzed. AlamarBlue cell proliferation assay, melanin content assay, tyrosinase activity assay, Western blotting analysis, electron microscopic analysis, and RNA interference were employed.
Results: In NHEMs, melanin content was reduced by treatment with ADAM protease inhibitors. The inhibitors did not change the protein expression of tyrosinase, TRP-1, and MITF. In B1 6F10 cells, treatment of the cells with ADAM protease inhibitor diminished the alpha-MSH-induced increase in melanin content. Electron microscopy showed that the number of fibrillar and mature melanosomes was significantly reduced and that the vacuolar compartments were filled with dense unstructured aggregates after treatment with ADAM protease inhibitors. We therefore focused on the processing of PMEL17, a melanosomal glycoprotein that forms a fibrillar matrix on which melanin gets deposited. Proteolytic processing of PMEL17 is required to form functional fibrils during melanogenesis. Recently, gamma-secretase and beta-site amyloid precursor protein-cleaving enzyme 2 (BACE2) were found to cleave PMEL17. We found that ADAM protease inhibitors exerted effects on the processing of C-terminal and Nterminal fragments of PMEL17. Using BACE2 siRNA and gamma-secretase inhibitor, we showed that ADAM protease inhibitor affected PMEL17 processing in a gamma-secretase and BACE2-independent mechanism.
Conclusion: Several proteases, including ADAM proteases, can contribute to the formation of fibrils and their assembly into sheets in melanosomes.

• 出版日期2015-5