Skin pigmentation involves the production of the pigment melanin by melanocytes, in melanosomes and subsequent transfer to keratinocytes. Within keratinocytes, melanin polarizes to the apical perinuclear region to form a protective cap, shielding the DNA from ultraviolet radiation-induced damage. Previously, we found evidence to support the exocytosis by melanocytes of the melanin core, termed melanocore, followed by endo/phagocytosis by keratinocytes as a main form of transfer, with Rab11b playing a key role in the process. Here, we report the requirement for the exocyst tethering complex in melanocore exocytosis and transfer to keratinocytes. We observed that the silencing of the exocyst subunits Sec8 or Exo70 impairs melanocore exocytosis from melanocytes, without affecting melanin synthesis. Moreover, we confirmed by immunoprecipitation that Rab11b interacts with Sec8 in melanocytes. Furthermore, we found that the silencing of Sec8 or Exo70 in melanocytes impairs melanin transfer to keratinocytes. These results support our model as melanocore exocytosis from melanocytes is essential for melanin transfer to keratinocytes and skin pigmentation and suggest that the role of Rab11b in melanocore exocytosis is mediated by the exocyst.

中文翻译：

---

囊泡是黑色素从黑素细胞胞吐并转移到角质形成细胞所必需的。

皮肤色素沉着涉及黑色素细胞中黑色素细胞中色素黑色素的产生，并随后转移至角质形成细胞中。在角质形成细胞内，黑色素极化至顶核周围区域，形成保护帽，从而保护DNA免受紫外线辐射引起的损害。以前，我们发现证据支持黑色素核心的黑色素细胞（称为melanocore）的胞吐作用，其次是角质形成细胞的内吞/吞噬作用，这是转移的主要形式，Rab11b在此过程中起关键作用。在这里，我们报告了在melanocore胞吐作用和转移到角质形成细胞中的囊外束缚复合物的要求。我们观察到，囊外亚基Sec8或Exo70的沉默会损害黑素细胞的melanocore胞吐作用，而不会影响黑色素的合成。而且，我们通过免疫沉淀证实Rab11b与黑素细胞中的Sec8相互作用。此外，我们发现黑素细胞中Sec8或Exo70的沉默会损害黑色素向角质形成细胞的转移。这些结果支持我们的模型，因为黑素细胞的黑素核胞吐作用对于黑色素转移至角质形成细胞和皮肤色素沉着至关重要，并暗示Rab11b在黑素核素胞吐作用中的作用是由囊泡介导的。