Institut Curie, PSL Research University, UMR144, Centre de Recherche, 26 rue d'Ulm, 75231 Paris, France; Centre National de la Recherche Scientifique, UMR144, Paris F-75248, France; Cell and Tissue Imaging Core Facility PICT-IBiSA, Institut Curie, Paris, France.
Institute of Cancer Research, Medical University Vienna, Vienna, Austria.
J Mol Biol. 2018 Oct 12;430(20):3802-3818. doi: 10.1016/j.jmb.2018.06.033. Epub 2018 Jun 22.
Genetically inheritable pigmentation defects provide a unique opportunity to reveal the function of proteins contributing to melanogenesis. Dyschromatosis universalis hereditaria (DUH) is a rare pigmentary genodermatosis associated with mutations in the ABCB6 gene. Here we use optical and electron microscopy imaging combined with biochemical tools to investigate the localization and function of ABCB6 in pigment cells. We show that ABCB6 localizes to the membrane of early melanosomes and lysosomes of the human melanocytic cell line MNT-1. Depletion of ABCB6 by siRNA impaired PMEL amyloidogenesis in early melanosomes and induced aberrant accumulation of multilamellar aggregates in pigmented melanosomes. PMEL fibril formation and normal maturation of pigmented melanosomes could be restored by the overexpression of wild-type ABCB6 but not by variants containing an inactivating catalytic mutation (K629M) or the G579E DUH mutation. In line with the impairment of PMEL matrix formation in the absence of ABCB6, morphological analysis of the retinal pigment epithelium of ABCB6 knockout mice revealed a significant decrease of melanosome numbers. Our study extends the localization of ABCB6 to melanosomes, suggesting a potential link between the function of ABCB6 and the etiology of DUH to amyloid formation in pigment cells.
遗传性可遗传的色素沉着缺陷为揭示参与黑色素生成的蛋白质的功能提供了独特的机会。遗传性全身色素异常（DUH）是一种罕见的色素性皮肤遗传病，与 ABCB6 基因突变有关。在这里，我们使用光学和电子显微镜成像结合生化工具来研究 ABCB6 在色素细胞中的定位和功能。我们表明 ABCB6 定位于人黑素细胞系 MNT-1 的早期黑素体和溶酶体的膜上。通过 siRNA 耗尽 ABCB6 会损害早期黑素体中的 PMEL 淀粉样变性，并诱导色素性黑素体中异常的多层聚集体积累。野生型 ABCB6 的过表达可以恢复 PMEL 纤维形成和色素性黑素体的正常成熟，但含有失活催化突变（K629M）或 DUH 突变 G579E 的变体则不能。与 ABCB6 缺失时 PMEL 基质形成受损一致，ABCB6 敲除小鼠视网膜色素上皮的形态分析显示黑素体数量明显减少。我们的研究将 ABCB6 的定位扩展到黑素体，表明 ABCB6 的功能与 DUH 中色素细胞中淀粉样形成的病因之间存在潜在联系。
