PDF(Pubmed)
Abstract：
Melanosomes are specialized membrane-bound organelles where melanin is synthesized and stored. The levels of melanin can be effectively reduced by inhibiting melanin synthesis or promoting melanosome degradation via autophagy. Ceramide, a key component in the metabolism of sphingolipids, is crucial for preserving the skin barrier, keeping it hydrated, and warding off the signs of aging. Our preliminary study indicated that a long-chain C22-ceramide compound (Ehux-C22) isolated from the marine microalga Emiliania huxleyi, reduced melanin levels via melanosomal autophagy in B16 cells. Recently, microRNAs (miRNAs) were shown to act as melanogenesis-regulating molecules in melanocytes. However, whether the ceramide Ehux-C22 can induce melanosome autophagy at the post-transcriptional level, and which potential autophagy-dependent mechanisms are involved, remains unknown. Here, miR-199a-3p was screened and identified as a novel upregulated miRNA in Ehux-C22-treated B16 cells. An in vitro high melanin expression model in cultured mouse melanoma cells (B16 cells) was established by using 0.2 μM alpha-melanocyte-stimulating hormone(α-MSH) and used for subsequent analyses. miR-199a-3p overexpression significantly enhanced melanin degradation, as indicated by a reduction in the melanin level and an increase in melanosome autophagy. Further investigation demonstrated that in B16 cells, Ehux-C22 activated miR-199a-3p and inhibited mammalian target of rapamycin(mTOR) level, thus activating the mTOR-ULK1 signaling pathway by promoting the expression of unc-51-like autophagy activating kinase 1 (ULK1), B-cell lymphoma-2 (Bcl-2), Beclin-1, autophagy-related gene 5 (ATG5), and microtubule-associated protein light chain 3 (LC3-II) and degrading p62. Therefore, the roles of Ehux-C22-regulated miR-199a-3p and the mTOR pathway in melanosomal autophagy were elucidated. This research may provide novel perspectives on the post-translational regulation of melanin metabolism, which involves the coordinated control of melanosomes.
摘要：
黑色素体是合成和储存黑色素的特化膜结合细胞器。黑色素的水平可以通过抑制黑色素合成或通过自噬促进黑素体降解来有效降低。神经酰胺,鞘脂代谢的关键成分，对保护皮肤屏障至关重要，保持它的水分，避开衰老的迹象。我们的初步研究表明，从海洋微藻Emilianiahuxleyi中分离出的长链C22-神经酰胺化合物（Ehux-C22），通过B16细胞中的黑色素自噬降低黑色素水平。最近,microRNAs（miRNAs）在黑素细胞中作为黑素生成调节分子发挥作用。然而,神经酰胺Ehux-C22是否可以在转录后水平诱导黑素小体自噬，以及涉及哪些潜在的自噬依赖性机制，仍然未知。这里,在Ehux-C22处理的B16细胞中筛选并鉴定miR-199a-3p为新的上调的miRNA。通过使用0.2μMα-黑素细胞刺激激素（α-MSH）在培养的小鼠黑色素瘤细胞（B16细胞）中建立了体外高黑色素表达模型，并用于随后的分析。miR-199a-3p过表达显著增强黑色素降解，如黑色素水平降低和黑素小体自噬增加所示。进一步的研究表明，在B16细胞中，Ehux-C22激活miR-199a-3p并抑制哺乳动物雷帕霉素靶蛋白（mTOR）水平，从而通过促进unc-51样自噬激活激酶1（ULK1）的表达激活mTOR-ULK1信号通路，B细胞淋巴瘤-2(Bcl-2),Beclin-1,自噬相关基因5(ATG5),和微管相关蛋白轻链3（LC3-II）和降解p62。因此,Ehux-C22调控的miR-199a-3p和mTOR通路在黑色素自噬中的作用被阐明.这项研究可能为黑色素代谢的翻译后调节提供新的观点，涉及黑色素体的协调控制。
