Laboratory of Membrane Trafficking Mechanisms, Department of Integrative Life Sciences, Graduate School of Life Sciences, Tohoku University, Aobayama, Aoba-Ku, Sendai, Miyagi, 980-8578, Japan.
Sci Rep. 2024 Jan 30;14(1):2529. doi: 10.1038/s41598-024-53072-6.
Tyrosinase (Tyr) is a key enzyme in the process of melanin synthesis that occurs exclusively within specialized organelles called melanosomes in melanocytes. Tyr is synthesized and post-translationally modified independently of the formation of melanosome precursors and then transported to immature melanosomes by a series of membrane trafficking events that includes endoplasmic reticulum (ER)-to-Golgi transport, post-Golgi trafficking, and endosomal transport. Although several important regulators of Tyr transport have been identified, their precise role in each Tyr transport event is not fully understood, because Tyr is present in several melanocyte organelles under steady-state conditions, thereby precluding the possibility of determining where Tyr is being transported at any given moment. In this study, we established a novel synchronized Tyr transport system in Tyr-knockout B16-F1 cells by using Tyr tagged with an artificial oligomerization domain FM4 (named Tyr-EGFP-FM4). Tyr-EGFP-FM4 was initially trapped at the ER under oligomerized conditions, but at 30 min after chemical dissociation into monomers, it was transported to the Golgi and at 9 h reached immature melanosomes. Melanin was then detected at 12 h after the ER exit of Tyr-EGFP-FM4. By using this synchronized Tyr transport system, we were able to demonstrate that Tyr-related protein 1 (Tyrp1), another melanogenic enzyme, is a positive regulator of efficient Tyr targeting to immature melanosomes. Thus, the synchronized Tyr transport system should serve as a useful tool for analyzing the molecular mechanism of each Tyr transport event in melanocytes as well as in the search for new drugs or cosmetics that artificially regulate Tyr transport.
酪氨酸酶(Tyr)是黑色素合成过程中的关键酶,仅在黑素细胞中称为黑素小体的专门细胞器中发生。Tyr 是在黑素体前体形成之前独立合成和翻译后修饰的,然后通过一系列膜运输事件被转运到未成熟的黑素小体,这些事件包括内质网(ER)到高尔基体的运输、高尔基体后运输和内体运输。虽然已经鉴定出几个 Tyr 运输的重要调节剂,但它们在每个 Tyr 运输事件中的精确作用尚不完全清楚,因为 Tyr 在稳态条件下存在于几种黑素细胞细胞器中,从而排除了在任何给定时刻确定 Tyr 正在被运输到何处的可能性。在这项研究中,我们通过使用带有人工寡聚化结构域 FM4 的 Tyr 标记(命名为 Tyr-EGFP-FM4),在 Tyr 敲除的 B16-F1 细胞中建立了一个新颖的同步 Tyr 运输系统。Tyr-EGFP-FM4 在寡聚化条件下最初被捕获在 ER 中,但在化学解离为单体 30 分钟后,它被转运到高尔基体,并在 9 小时后到达未成熟的黑素小体。Tyr-EGFP-FM4 离开 ER 后 12 小时检测到黑色素。通过使用这种同步 Tyr 运输系统,我们能够证明另一种黑色素生成酶酪氨酸相关蛋白 1(Tyrp1)是 Tyr 有效靶向未成熟黑素小体的正调节剂。因此,同步 Tyr 运输系统应该作为一种有用的工具,用于分析黑素细胞中每个 Tyr 运输事件的分子机制,以及寻找人工调节 Tyr 运输的新药物或化妆品。