Tyrosinase catalyzes the rate‐limiting step in melanin synthesis. Melanin is synthesized from l‐tyrosin in the melanosomes, where tyrosinase and other melanogenic factors are recruited via the vesicle transport system. Genetic and biochemical approaches have revealed a correlation between impairments in the vesicle transport system and albinism. However, the specificity of the individual transport systems for the corresponding melanogenic factors has not been well elucidated yet. Here, we report that the thioxothiazolidin derivative, 4‐OST (4‐[(5E)‐5‐[(4‐fluorophenyl)methylidene]‐4‐oxo‐2‐sulfanylidene‐1,3‐thiazolidin‐3‐yl]‐4‐azatricyclo [5.2.1.0²,6]dec‐8‐ene‐3,5‐dione: CAS RN. 477766‐87‐3) strongly inhibited melanogenesis in mouse melanoma B16F10 cells. 4‐OST reduces tyrosinase protein levels without affecting its messenger RNA levels or enzymatic activity. Although a reduction in tyrosinase protein level was observed in the presence of a protein synthesis inhibitor, the reduction may be coupled with protein synthesis. Similarly, GIF‐2202 (a derivative of 4‐OST) lowers tyrosinase protein levels without affecting the levels of another melanogenic enzyme, tyrosinase‐related protein 1 (TYRP1) level. The reduction in tyrosinase protein level is associated with an increase in the levels of the lysosomal proteinase cathepsin S. Chloroquine, a lysosome inhibitor, restored the tyrosinase protein level downregulated by GIF‐2202, although no effects of other inhibitors (against proteasome, autophagy, or exocytosis) were observed. In addition, GIF‐2202 segregated the immunofluorescence signals of tyrosinase from those of TYRP1. Chloroquine treatment resulted in co‐localization of tyrosinase and cathepsin S signals near the perinuclear region, suggesting that 4‐OST and GIF‐2202 may alter the destination of the tyrosinase vesicle from the melanosome to the lysosome. 4‐OST and GIF‐2202 can be new tools for studying the tyrosinase‐specific vesicle transport system.

中文翻译：

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硫代噻唑烷衍生物，4-OST，通过增强含有酪氨酸酶的囊泡向溶酶体的特异性募集来抑制黑色素生成

酪氨酸酶催化黑色素合成的限速步骤。黑色素由黑色素体中的l-酪氨酸合成，其中酪氨酸酶和其他黑色素生成因子通过囊泡运输系统被募集。遗传和生化方法揭示了囊泡运输系统的损伤与白化病之间的相关性。然而，个体运输系统对相应黑色素生成因子的特异性尚未得到很好的阐明。在这里，我们报告了硫代噻唑啉衍生物 4-OST (4-[(5E)-5-[(4-fluorophenyl)methylidene]-4-oxo-2-sulfanylidene-1,3-thiazolidin-3-yl]- 4-氮杂三环 [5.2.1.0 ²,6]dec-8-ene-3,5-dione：CAS RN。477766-87-3) 强烈抑制小鼠黑色素瘤 B16F10 细胞中的黑色素生成。4-OST 降低酪氨酸酶蛋白水平而不影响其信使 RNA 水平或酶活性。尽管在蛋白质合成抑制剂的存在下观察到酪氨酸酶蛋白质水平的降低，但该降低可能与蛋白质合成有关。类似地，GIF-2202（4-OST 的衍生物）降低酪氨酸酶蛋白水平而不影响另一种黑色素生成酶酪氨酸酶相关蛋白 1（TYRP1）水平。酪氨酸酶蛋白水平的降低与溶酶体蛋白酶组织蛋白酶 S 水平的增加有关。氯喹，一种溶酶体抑制剂，恢复了 GIF-2202 下调的酪氨酸酶蛋白水平，尽管其他抑制剂（针对蛋白酶体，自噬或胞吐作用）被观察到。此外，GIF-2202 将酪氨酸酶的免疫荧光信号与 TYRP1 的免疫荧光信号分开。氯喹处理导致酪氨酸酶和组织蛋白酶 S 信号在核周区域附近共定位，表明 4-OST 和 GIF-2202 可能改变酪氨酸酶囊泡从黑素体到溶酶体的目的地。4-OST 和 GIF-2202 可以成为研究酪氨酸酶特异性囊泡转运系统的新工具。