Central Laboratory of Shaanxi Provincial People's Hospital, Xi'an, Shaanxi, China.
Department of Clinical Laboratory, Northwest Women and Children's Hospital, Xi'an, Shaanxi, China.
Biochem Biophys Res Commun. 2018 Sep 18;503(4):2536-2542. doi: 10.1016/j.bbrc.2018.07.012. Epub 2018 Jul 7.
The functionally specialized melanosome is a membrane-enclosed lysosome-related organelle, which coexists with lysosomes in melanocytes. Pre-melanosomal protein (PMEL) initiates pre-melanosome morphogenesis and is the only cell-specific pigment protein required for the formation of fibrils on which melanin is deposited in melanosomes. But the effects of PMEL on melanin synthesis and lysosome activity remain unclear. In the study, PMEL was silenced in human epidermal melanocytes by siRNA transfection. Compared to the non-treated group, melanin content in the transfected cells was greatly reduced. Real-time qPCR, Western blotting and immunofluorescence analyses all showed that PMEL-siRNA transfection reduced protein level of tyrosinase, a key enzyme in melanogenesis, but it does not affect tyrosinase gene expression. Moreover, in the absence of PMEL, lysosomal activation was manifested by an increase in the number of lysosomes and activity of hydrolysis enzymes. The lysosome inhibitors restored tyrosinase expression after PMEL silencing, indicating that tyrosinase was degradated by lysosomes. The data collectively showed that silencing of PMEL suppressed melanization through activating lysosomes and degradation of tyrosinase by lysosomes. Our findings provide novel insight into the interaction between the melanosome and its related organelle, the lysosome, supplying a new idea for the pathogenesis and clinical treatment of pigmented diseases.
功能性特化的黑素体是一种膜包裹的溶酶体相关细胞器，与黑素细胞中的溶酶体共存。前黑素小体蛋白 (PMEL) 启动前黑素小体形态发生，是形成黑素体中黑色素沉积的原纤维所必需的唯一细胞特异性色素蛋白。但是，PMEL 对黑色素合成和溶酶体活性的影响仍不清楚。在这项研究中，通过 siRNA 转染沉默了人表皮黑素细胞中的 PMEL。与未处理组相比，转染细胞中的黑色素含量大大减少。实时 qPCR、Western blot 和免疫荧光分析均表明，PMEL-siRNA 转染降低了黑色素生成关键酶酪氨酸酶的蛋白水平，但不影响酪氨酸酶基因表达。此外，在没有 PMEL 的情况下，溶酶体的激活表现为溶酶体数量的增加和水解酶活性的增加。在 PMEL 沉默后，溶酶体抑制剂恢复了酪氨酸酶的表达，表明酪氨酸酶被溶酶体降解。这些数据表明，沉默 PMEL 通过激活溶酶体和溶酶体降解酪氨酸酶来抑制黑色素生成。我们的研究结果为黑素体与其相关细胞器溶酶体之间的相互作用提供了新的见解，为色素性疾病的发病机制和临床治疗提供了新的思路。
